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OZ OZOZ OZ O[  O[ ?O[ ?O[? ?ÀO[? ?ÀO[???O[ ??O[ ??O[ ??O[ ?O[ ?O[??O[?? ?O\ ?? ?O\ ?? ?\?O\? x?? ?O\  ? x?O]? |?Os?  ?Or? Or? Pr? ?Pr ? ÀP/B? ÀPq? Pq? ?Pq?  Pq??  ?Pq? Pq?bq?bq?bq?cq?cq ?q??q L$p?q`?qxq|0q prgX ߀s߀Z     О#XZ2PXP#UK* #&R2P&P# #2PP# EUROPEAN GUIDELINES ON QUALITY CRITERIA FOR COMPUTED TOMOGRAPHY #&R2P&P# uu1uu1yDuq-]ddDy  * &EUR 16262 T  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P&P#  О  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkmGa)IT#2PP# EUROPEAN GUIDELINES ON QUALITY CRITERIA FOR COMPUTED TOMOGRAPHY #&R2P&P# These Guidelines result from the cooperative effort of the following European Study Group of radiologists and physicists involved in diagnostic computed tomography and consultation with experts in the field: Radiologists: G. Bongartz (CH) S.J. Golding (UK) A.G. Jurik (DK) M. Leonardi (I) E.v.P. van Meerten (NL) Physicists: J. Geleijns (NL) K.A. Jessen (DK) W. Panzer (D) P.C. Shrimpton (UK) G. Tosi (I) The present Report has been supported and edited in the framework of the European Commission's Radiation Protection Actions by: H.G. Menzel H. Schibilla D. Teunen * d%EUR 16262 EN ă S  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P&P#  О  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkmaa)S Y #i2P P#QUALITY CRITERIA FOR COMPUTED TOMOGRAPHY#&R2P &P# ă #Table of Contents ă `e!#GPage PREAMBLE `u"#IIII b: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkCHAPTER 1 : : : Quality Criteria for Computed Tomography`"#I1 bbb: : : Lyn22' ' ' Introduction!vv';;-39?O O D`w"#I 2' ' ' ƒ bbb: : : Lyn22' ' ' Objectives`w"#I 2 bbb: : : Lyn22' ' ' General Principles Associated with`"#I4 bbb: : : ' ' ' Good Imaging Technique; Technical, bbb: : : ' ' ' Clinical and Physical Parameters bbb: : : Lyn22' ' ' Guidance on Implementation`E"#I11 bbb: : : Lyn22' ' ' Description of Terms used in the Lists`E"#I12 bbb: : : ' ' ' of Quality Criteria bbb: : : Lyn22' ' ' List of Quality Criteria for Computed`E"#I15 bbb: : : ' ' ' Tomography bbb: : : Lyn22' ' ' List of References`E"#I62 bbb: : : Lyn22' ' ' Appendix I: Guidelines on Radiation Dose`E"#I64 bbb: : : ' ' ' to the Patient CHAPTER 2 : : : Summary of Research Results and Ongoing `E"#I71 bbb: : : Experiments Related to the Establishment bbb: : : of the Quality Criteria for CT and Reference bbb: : : Dose Values CHAPTER 3 : : : Quality Criteria Implementation and Audit Guidelines`E"#I87 CHAPTER 4 : : : Glossary`E"#I99 #XN\  P XP# DK)II#&R2P &P#UKӃ  PREAMBLE Computed Tomography (CT) was introduced into clinical practice in 1972 and revolutionised xray imaging by providing high quality images which reproduced transverse cross sections of the body. The technique offered in particular improved low contrast resolution for better visualization of soft tissue, but with relatively high absorbed radiation dose. The initial potential of the imaging modality has been realised by rapid technological developments, resulting in a continuing expansion of CT practice. As a result, the numbers of examinations are increasing to the extent that CT has made a substantial impact on not only patient care but also patient and population exposure from medical xrays. Today it accounts for up to 40% of the resultant collective dose from diagnostic radiology in some countries of the European Union (EU) (1,2). Special measures are consequently required to ensure optimisation of performance in CT, and of patient protection. In comparison with conventional radiology, the relative complexity, range and flexibility of scanner settings in CT may adversely affect the levels of image quality and patient dose achieved in practice. There is, therefore, a need to establish quality criteria for CT which will provide the required clinical information in its optimal form, with minimum dose to the patient. The quality criteria concept, as developed for conventional xray examinations of adult and paediatric patients by the European Commissions (EC) research actions, has proved to be an effective method for optimising the use of ionising radiation in medical imaging procedures. The purpose of quality criteria for CT was therefore also to provide an operational framework for radiation protection initiatives for this modality, in which technical parameters required for image quality are considered in relation to patient dose. CT continues to evolve and the research base for guidance is limited. The study group on Development of Quality Criteria for CT has drawn extensively on the results of the projects carried out in the ECs Research Action on Optimisation of Radiation Protection of the Patient. It has also gained inspiration from the guidelines of the German Federal Chamber of Physicians on Quality Assurance in Computed Tomography (3). The primary working document of April 1997 has been commented on by external experts from countries in Europe and was presented at the EC workshop on reference dose and quality in medical imaging, October 1997, Luxembourg (4). A revised document dated May 1998 was posted on the Internet (http://www.drs.dk/CT/document/) and advertised to all national delegates of the European Association of Radiology (EAR) and the European Federation of Organisations for Medical Physics (EFOMP), in addition to the European National Boards of Health and the associations of radiographers. A notification was also given to these bodies of a Workshop on Quality Criteria for Computed Tomography that was held in Aarhus, Denmark, 1314th November 1998. The document was open for discussion at the workshop and consequently revised to the present final guidelines. Furthermore, the study group performed a pilot study in 19971998 to test the image quality criteria, with simultaneous registration of the radiation dose, for five types of examination: 1) face and sinuses, 2) vertebral trauma, 3) HRCT of the lung, 4) liver and spleen and 5) osseous pelvis (5). The results have been taken into account in the final guidelines, including the specification of diagnostic reference dose values. These guidelines on Quality Criteria for Computed Tomography provide guidance on the definition and introduction of quality criteria for diagnostic images and equipment performance, as well as for dose to the patient. The report contains four chapters. The first chapter presents general principles associated with good imaging technique and lists the Quality Criteria for six groups of CT examination: cranium, face and neck, spine, chest, abdomen and pelvis, and bones and joints. Each group of examinations is subdivided into the most common examinations of specific organs or parts of the body. The chapter defines Diagnostic Requirements by specifying anatomical image criteria; indicates Criteria for the Radiation Dose to the Patient; and gives Examples of Good Imaging Technique by which the Diagnostic Requirements and Dose Criteria can be achieved. *  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P &P#  Оb: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhk  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkma(III*The second chapter summarises available research results as well as the ongoing experiments which have supported the establishment of the Quality Criteria listed in Chapter 1, and suggests directions for future research. The third chapter outlines a procedure for implementing and auditing the Quality Criteria and a model for image quality assessment. The fourth chapter contains a glossary of terms used in the guidelines. This initiative in CT will continue within the framework of forthcoming research programmes and is reflected by the Council Directive on health protection of individuals against dangers of ionising radiation in relation to medical exposure (6). For techniques such as CT the new Directive requires the establishment of quality assurance measures which include criteria that can be employed and checked in a comparable way so that the radiation dose to the patient can be linked to the required image quality and to the performance of the chosen technique. Emerging techniques such as multislice CT and fluoroCT have not been specifically addressed. With the continuing evolution of CT technology there will be a need for regular updating of the guidelines. It is the hope of the European Commissions services that the elaboration of the Quality Criteria for CT will stimulate the professionals concerned to look for improvements in the criteria in such a way that daytoday practice achieves optimal diagnostic information and fulfils at the same time the requirements for optimization of radiation protection in the 1997 Council Directive. Mr. S. Kaiser: : : ' ' ' vvv;;;Dr. H. Forsstr?m Directorate General vvv;;;Directorate General Environment, Nuclear Safety andvvv;;;Science, Research and Development Civil Protection' ' ' vvv;;;Nuclear Fission and Radiation Protection Radiation Protection 1.bbbKaul A, Bauer B, Bernhardt J, Noske D and Veit R. Effective doses to members of the public from the diagnostic application of ionizing radiation in Germany. European Radiology 7 , 1127 1132 (1997) 2.bbbShrimpton PC and Edyvean S. CT scanner dosimetry. British Journal of Radiology 71 , 1 3 (1998) 3.bbbLeitlinien der Bundesrztekammer zur Qualittssicherung in der Computertomographie. Dt. rztebl. 89 : Heft 49 (1992) (English translation: Guidelines of the Federal Chamber of Physicians on quality assurrence in computed tomography. Internal Document CEC XII/354/92-EN) 4.bbbBauer B, Corbett RH, Morres BH, Schibilla H and Teunen D (Eds). Proceedings of a Workshop on Reference Doses and Quality in Medical Imaging, Luxembourg, October 2325 1997. Radiation Protection Dosimetry 80 , Nos 13 (1998) 5.bbbJurik AG, Petersen J, Bongartz B, Golding SJ, Leonardi M, van Meerten PvE, Geleijns J, Jessen KA, Panzer W, Shrimpton P, Tosi G. Clinical use of image quality criteria in computed tomography related to radiation dose. A pilot study. European Radiology (to be submitted) ;  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P&P#  Оb: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhk  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm a(IVaa)aa);6.bbbCouncil Directive 97/43/EURATOM of 30 June 1997 on health protection of individuals against the dangers of ionizing radiation in relation to medical exposure. Official Journal L 180, p. 22, 9.7.1997. (Repealing Directive 84/466/EURATOM, O.J. no. L265, p. 1, 5.10.1984)   v  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P&P#  Оb: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhk  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#XZ2PXP#=a)#<2PP#v`#A #i2PP#Chapter 1#&R2P&P# ă  #i2PP#QUALITY CRITERIA FOR COMPUTED TOMOGRAPHY#&R2P&P# Table of Contents  `e!#GPage INTRODUCTION `"#I2 OBJECTIVES `"#I2 GENERAL PRINCIPLES ASSOCIATED WITH GOOD IMAGING TECHNIQUE; `"#I4 TECHNICAL, CLINICAL AND PHYSICAL PARAMETERS GUIDANCE ON IMPLEMENTATION `E"#I11 DESCRIPTION OF TERMS USED IN THE LISTS OF QUALITY CRITERIA `E"#I12 LIST OF QUALITY CRITERIA FOR COMPUTED TOMOGRAPHY `E"#I15 Cranium`E"#I16 Face and Neck`E"#I20 Spine`E"#I34 Chest`E"#I40 Abdomen and Pelvis`E"#I46 Bones and Joints`E"#I58 LIST OF REFERENCES `E"#I62 APPENDIX I: Guidelines on Radiation Dose to the Patient`E"#I64 _______ Technical terms are defined in the Glossary (Chapter 4) and are printed in italics when they are used for the first time in these guidelines.  #XZ2PXP#INTRODUCTION#&R2P&P# The two basic principles of radiation protection for medical exposures as recommended by ICRP are justification of practice and optimisation of protection, including the consideration of diagnostic reference levels (1, 2, 3). The emphasis is to keep dose to the patient as low as reasonably achievable (ALARA), consistent with clinical requirements. These principles are largely translated into a legal framework by the Council Directive (4). Justification is the first step in radiation protection and no diagnostic exposure is justifiable without a valid clinical indication. Every examination must result in a net benefit for the patient. This will be the case when it can be anticipated that the examination will influence the efficacy of clinical decisions made with respect to the following: """"""""bbb""""""""bbbdiagnosis """"""""bbb: : : patient management and therapy bbb: : : bb: : : final outcome for the patient """""""" Justification for computed tomography (CT) also implies that the required result cannot be achieved by other methods which are associated with lower risks for the patient. Ultrasound and MRI offer alternatives to CT in many areas of application. The magnitude of the absorbed dose in CT means that particular care is required for the examination of pregnant women, children, and particularly sensitive organs or tissues. Criteria for approving clinical requests in these circumstances need to be particularly stringent. As a corollary, justification requires that the imaging procedure is acceptably reliable, i.e. its results are reproducible and have sufficient predictive value with respect to the particular clinical question. Justification also necessitates that a suitably qualified person (as recognised by the competent authority), usually a radiologist, approves the need for CT and takes overall clinical responsibility for the examination. This person should work in close contact with the referring physician in order to establish the investigation procedure most appropriate to patient management. The person responsible may authorize an appropriately qualified operator (eg radiographer or medical radiation technologist) to perform the examination. In respect of radiological examinations, ICRP draws attention to the use of diagnostic reference levels as an aid to optimisation of protection in medical exposure. Once the diagnostic examination has been clinically justified, the subsequent imaging process must be optimised. The optimal use of ionising radiation involves the interplay of three important aspects of the imaging process: bM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQh bbbMMMbbMMMdiagnostic quality of the image """"""""bbbMMMbbMMMradiation dose to the patient """"""""bbbMMMbbMMMchoice of examination technique """""""" This document provides guidance on all three of these aspects for a number of selected CT examinations, as an example of an achievable standard of daytoday practice. The Quality Criteria presented define a level of performance considered necessary to produce images of standard quality for a particular anatomical region. For comparability, the aim has been to establish Guidelines on Quality Criteria for CT in accordance with the structure of the existing "European Guidelines for Diagnostic Radiographic Images" for adult and paediatric patients in conventional radiology (5, 6). #XZ2PXP#OBJECTIVES #&R2P&P#ьThe objectives of the guidelines are to achieve: bbbMMMbbMMMadequate image quality, comparable throughout Europe """"""""bbbMMMbbMMMreasonably low radiation dose per examination """""""" The guidelines also provide a basis for accurate radiological interpretation of the image. The guidelines are directed primarily at clinical and technical staff who perform CT and report on it. They will also be of interest to those responsible for the design of CT equipment and for the maintenance of its function. They will be helpful to those who have responsibility for equipment specification and purchase. The guidelines represent an achievable standard of good practice which may be used as a basis for further development by the radiological community. In support of these objectives, the guidelines provide structured advice on the following key areas: #XZ2PXP#Diagnostic Requirements#&R2P&P# The diagnostic requirements are presented as image criteria, which in CT are basically of two different types: anatomical and physical image criteria. The anatomical image criteria include requirements which must be fulfilled when specific clinical questions are posed. These criteria may be defined in terms of visualization or critical reproduction of anatomical features (see Description of Terms, p.12). Evaluation of image quality based on anatomical criteria takes into account both the anatomy of the area under examination and the contrast between different tissues which is essential for the detection of pathological changes. The physical image criteria are measurable by objective means. They include noise; low contrast resolution; spatial resolution; linearity; uniformity and stability of the CT numbers; slice thickness and dose. It is mandatory for departments carrying out CT to employ a suitable quality assurance programme to maintain imaging performance at optimal levels. Routine tests have to specify physical image criteria. #XZ2PXP#Criteria for Radiation Dose to the Patient#&R2P&P# Consideration of dose constraint has particular importance in CT, since this is recognised as a relatively high dose modality. ICRP (1) has recommended the dose constraint concept for medical exposure, that is translated to diagnostic reference levels for diagnostic radiography (3). The application of this concept is in line with the reference dose values for a standard sized patient indicated in the previous European Guidelines (5, 6). In the present guidelines tentative reference dose values for CT have been established for selected examinations in order to facilitate comparison of examination protocols used in different departments and with different types of equipment. The reference dose values are based on dose descriptors defined in Appendix 1. More detailed discussion of dosimetry is given in Chapter 2. Diagnostic reference dose values provide quantitative guidance to help identify relatively poor or inadequate use of the technique rather than an indication of satisfactory performance. Further dose reduction below reference values may be achievable without compromising the diagnostic value of an individual examination, and this should always be pursued. #XZ2PXP#Examples of Good Imaging Technique#&R2P&P# Image quality in CT depends primarily on two types of scan parameter: doserelated parameters and those which are related to processing and viewing of the image. Both are hardware related. Doserelated parameters are the slice thickness, interslice distance, pitch factor, volume of investigation, exposure factors and gantry tilt. Processing parameters are field of view, number of measurements, reconstruction matrix size, reconstruction algorithm and window settings for viewing the image. Impact of these parameters on image quality and patient dose can be assessed quantitatively by measurement with test phantoms, which provide information essential to the definition of quality criteria related to the clinical objective. #XZ2P XP#GENERAL PRINCIPLES ASSOCIATED WITH GOOD IMAGING TECHNIQUE: TECHNICAL, CLINICAL AND PHYSICAL PARAMETERS #&R2P!&P# CT images are the result of the interplay of physical phenomena giving rise to attenuation by the patient of a thin fan beam of xrays, and complex technical procedures. Each image consists of a matrix of pixels whose CT numbers (measured in Hounsfield Units, HU) represent attenuation values for the volume elements (voxels) within the slice. The quality of the image relates to the fidelity of the CT numbers and to the accurate reproduction of small differences in attenuation (low contrast resolution) and fine detail (spatial resolution). Good imaging performance demands that image quality should be sufficient to meet the clinical requirement for the examination, whilst maintaining the dose to the patient at the lowest level that is reasonably practicable. In order to achieve this, there must be careful selection of technical parameters that control exposure of the patient and the display of the images, and also regular checking of scanner performance with measurement of physical image parameters as part of a programme of quality assurance. #XZ2P"XP# Lyn1..bbbTechnical Parameters: Display and Exposure Parameters with an Influence on Image Quality and Dose Lyn1. #&G\  P#&P#bbb bb 1.1bbbNominal slice thickness bbbThe nominal slice thickness in CT is defined as the full width at half maximum (FWHM) of the sensitivity profile, in the centre of the scan field; its value can be selected by the operator according to the clinical requirement and generally lies in the range between 1mm and 10mm. In general, the larger the slice thickness, the greater the low contrast resolution in the image; the smaller the slice thickness, the greater the spatial resolution. If the slice thickness is large, the images can be affected by artefact, due to partial volume effects; if the slice thickness is small (e.g. 12mm), the images may be significantly affected by noise. bbb bb 1.2bbbInterslice distance/pitch factor bbbInterslice distance is defined as the couch increment minus nominal slice thickness. In helical CT the pitch factor is the ratio of the couch increment per rotation to the nominal slice thickness at the axis of rotation. In clinical practice the interslice distance generally lies in the range between 0 and 10mm, and the pitch factor between 1 and 2. The interslice distance can be negative for overlapping scans which in helical CT means a pitch < 1. In general, for a constant volume of investigation, the smaller the interslice distance or pitch factor, the higher both the local dose and the integral dose to the patient. The increase in the local dose is due to superimposition of the dose profiles of the adjacent slices. The increase in the integral dose is due to an increase in the volume of tissue undergoing direct irradiation as indicated by a packing factor.  bbbIn those cases where 3D reconstruction or reformatting of the images in coronal, sagittal or oblique planes is required, it is necessary to reduce the interslice distance to zero or perform a helical scan. In screening or examinations performed with regard to control of disease it can be diagnostically justifiable to have an interslice distance corresponding to half the slice thickness or a pitch factor of 1.52. 1.3bbbVolume of investigation bbbVolume of investigation, or imaging volume, is the whole volume of the region under examination. It is defined by the outermost margins of the first and last examined slices or helical exposure. The extent of the volume of investigation depends on the clinical needs; in general the greater its value the higher the integral dose to the patient, unless an increased interslice distance or pitch factor is used. 1.4bbbExposure factors bbbExposure factors are defined as the settings of xray tube voltage (kV), tube current (mA) and exposure time (s). In general, one to three values of tube voltage (in the range between 80 and 140 kV) can be selected. A high tube voltage is recommended for high resolution CT (HRCT) of the lungs and may be used for examination of osseous structures such as the spine, pelvis and shoulder. Soft tissue structures are usually best visualised using the standard tube voltage for the given equipment. In some cases of quantitative computed tomography (QCT), the same slice is examined with two different values of tube voltage, in order to subtract corresponding images and derive information about the composition of particular tissues. At given values of tube voltage and slice thickness, the image quality depends on the product of xray tube current (mA) and exposure time (s), expressed in mAs. Absolute values of mAs necessary for an imaging task will depend on the type of scanner and the patient size and composition. For a particular CT model, an increase in radiographic exposure setting (mAs) is accompanied by a proportional increase in the dose to the patient. Relatively high values of radiographic exposure setting (mAs) should therefore be selected only in those cases where a high signal to noise ratio is indispensable. bbbA method for correlating the exposure setting (for a given tube voltage) with the overall image quality is by drawing contrastdetail curves for each available setting. These curves express the minimum size of detail which can still be recognised in the CT image for a given difference in contrast between the detail and the surrounding medium. 1.5bbbField of view bbbField of view (FOV) is defined as the maximum diameter of the reconstructed image. Its value can be selected by the operator and generally lies in the range between 12 and 50 cm. The choice of a small FOV allows increased spatial resolution in the image, because the whole reconstruction matrix is used for a smaller region than is the case with a larger FOV; this results in reduction of the pixel size. In any case, the selection of the FOV must take into account not only the opportunity for increasing the spatial resolution but also the need for examining all the areas of possible disease. If the FOV is too small, relevant areas may be excluded from the visible image. If raw data are available the FOV can be changed by postprocessing. 1.6bbbGantry tilt bbbGantry tilt is defined as the angle between the vertical plane and the plane containing the xray tube, the xray beam and the detector array. Its value normally lies in the range between 25$ and +25$. The degree of gantry tilt is chosen in each case according to the clinical objective. It may also be used to reduce the radiation dose to sensitive organs or tissues and/or to reduce or eliminate artefacts. 1.7bbbReconstruction matrix bbbReconstruction matrix is the array of rows and columns of pixels in the reconstructed image, typically 512 x 512. 1.8bbbReconstruction algorithm bbbReconstruction algorithm (filter, or kernel) is defined as the mathematical procedure used for the convolution of the attenuation profiles and the consequent reconstruction of the CT image. In most CT scanners, several reconstruction algorithms are available. The appearance and the characteristics of the CT image depend strongly on the algorithm selected. Most CT scanners have special soft tissue or standard algorithms for examination of the head, abdomen etc. Depending on clinical requirements, it may be necessary to select a high resolution algorithm which provides greater spatial resolution, for detailed representation of bone and other regions of high natural contrast such as pulmonary parenchyma. 1.9bbbWindow width bbbWindow width is defined as the range of CT numbers converted into grey levels and displayed on the image monitor. It is expressed in HU. The window width can be selected by the operator according to the clinical requirements, in order to produce an image from which the clinical information may be easily extracted. In general, a large window (for instance 400 HU) represents a good choice for acceptable representation of a wide range of tissues. Narrower window widths adjusted to diagnostic requirements are necessary to display details of specific tissues with acceptable accuracy. 1.10bbbWindow level bbbWindow level is expressed in HU and is defined as the central value of the window used for the display of the reconstructed CT image. It should be selected by the viewer according to the attenuation characteristics of the structure under examination. #XN\  P$XP# Lyn1..bbbClinical and Associated Performance Parameters Lyn1. #&G\  P%&P# bbbA series of clinical factors play a special part in the optimal use of ionising radiation in CT. They are described here in order to ensure that an appropriate CT examination is carried out, providing diagnostic quality with a reasonable radiation dose for the patient. bbb A CT examination should therefore only be carried out on the basis of a justifiable clinical indication, and exposure of the patient should always be limited to the minimum necessary to meet clinical objectives. bbbAdequate clinical information, including the records of previous imaging investigations, must be available to the person approving requests for CT. bbbIn certain applications, in order to practice CT effectively, prior investigation of the patient by other forms of imaging might be required. 2.1bbbSupervision bbbCT examinations should be performed under the clinical responsibility of a radiologist/practitioner according to the regulations (4) and standard examination protocols should be available. bbbEffective supervision may support radiation protection of the patient by terminating the examination when the clinical requirement has been satisfied, or when problems occurring during the examination (for example, unexpected uncooperation by the patient or the discovery of contrast media residue from previous examinations) cannot be overcome. bbbProblems and pitfalls: the responsible radiologist/practitioner should be aware of clinical or technical problems which may interfere with image quality. Many of these are particular to specific organs or tissues and may lead to modification of technique. The radiologist/practitioner and the radiographer must be aware of manoeuvres which may be used to overcome such diagnostic or technical problems in order to provide a clinically relevant examination. 2.2bbbPatient Preparation bbbThe following patientrelated operational parameters play an important role for the quality of the CT examination: bbb2.2.1: : : Cooperation. Patient cooperation should be ensured as far as possible prior to the examination. An explanation of the procedure should be given to each patient. Good communication with and control of the patient is equally necessary during the whole examination. bbb2.2.2: : : Protective Shielding. Relevant protection for sensitive organs outside the imaging field is a leadpurse for the male gonads, if the edge of the volume of investigation is less than 10 15 cm away. The protection of female gonads by wraparound lead has not yet been demonstrated (7,8). Appropriate protection measures must be applied to persons who, for clinical reasons or to ensure cooperation, may need to accompany patients in the examination room during the examination. bbb2.2.3: : : Clothing. The area of examination should be free of external metal or other radio dense items where possible. Special attention must be given to eliminating any xray dense material in the patients clothes or hair. bbb2.2.4: : : Fasting. Fasting prior to the examination is not essential. Restraint from food, but not fluid, is recommended if intravenous contrast media are to be given. bbb2.2.5: : : Intravenous contrast media. These are needed in some examinations and must be employed in a manner appropriate to the clinical indication, taking into consideration the risk factors. bbb2.2.6: : : MM: : : Oral or cavitatory contrast media. Oral contrast medium may be required in abdominopelvic examinations and must be administered at times and in doses appropriate to the indication. Administration of contrast medium per rectum may be required in some examinations of the pelvis and a vaginal tampon should be used in some examinations for gynaecological applications. bbb2.2.7: : : Positioning and motion. Most CT examinations are carried out with the patient supine. In this position the patient is most comfortable with the knees flexed. Alternate positioning may be required to aid comfort and cooperation, for appropriate display of anatomy, to reduce absorbed radiation to particular organs, or to minimise artefact. Motion should be kept to a minimum to reduce artefacts; typical sources of artefacts are involuntary patient movement, respiration, cardiovascular action, peristalsis and swallowing. 2.3bbbExamination Technique bbb " "MMMScan projection radiograph. bbbMMMA scan projection radiograph permits the examination to be planned and controlled accurately, and provides a record of the location of images. It is recommended that this is performed in all cases. In general such imaging provides only a small fraction of the total patient dose during a complete CT procedure (9) bbbMMMClinical aspects of setting the appropriate technical parameters. bbbMMMThese parameters must be set according to the area of examination and clinical indication, as follows: bbbMMM*: : : Nominal slice thickness is chosen according to the size of the anatomical structure or lesion that needs to be visualised. Staff should be aware of the implications of choice of slice thickness in relation to the image quality and radiation dose to the patient. bbbMMM*: : : #XZ2P&XP#Interslice distance is chosen according to the area under examination and the clinical indication. Staff should be aware of the risk of overlooking lesions which fall in the interslice interval during serial CT. In general, the interval should not exceed one half of the diameter of suspected lesions. This problem is absent in helical scanning, when an appropriate reconstruction index is used. """"""""bbbMMM*: : : #XZ2P'XP#Field of view (FOV). Selection of FOV must respect image resolution and the need to examine all areas of possible disease. If the FOV is too small, disease may be excluded from the visible image. bbbMMM*: : : Exposure factors: tube voltage (kV), tube current (mA) and exposure time (s) affect image quality and patient dose. Increasing exposure increases low contrast resolution by reducing noise but also increases patient dose. Patient size is an important factor in determining the image noise. Image quality consistent with the clinical indications should be achieved with the lowest possible dose to the patient. In certain examinations image noise is a critical issue and higher doses might be required. bbbMMM*: : : The volume of investigation is the imaging volume, defined by the beginning and end of the region imaged. It should cover all regions of possible disease for the particular indication. bbbMMM*: : : #XZ2P(XP#Reconstruction algorithm: this is set according to the indication and area under examination. For most examinations, images are displayed utilising algorithms suitable for soft tissues; other algorithms available include those providing greater spatial resolution for detailed display of bone and other areas of high natural contrast. 2.4bbbHelical or Spiral CT bbbHelical or spiral CT is obtained by continuous tube rotation coupled with continuous patient transport through the gantry, resulting in volumetric data acquisition. Due to the high speed and ease of image performance with this technique it should be emphasized that helical CT presents particular challenges in radiation protection and it should not be used without clinical justification. Helical CT is in most cases preferable to serial CT because of advantages such as: bbbMMMa possibility of dose saving: bbbMMM*: : : the repeating of single scans, which sometimes results from lack of patient cooperation in serial CT, is reduced in spiral CT because of the shorter examination times involved bbbMMM*: : : for pitch > 1 the dose will be reduced compared with contiguous serial scanning; there are no data missing as may be the case with the use of an interslice interval in serial CT bbbMMM*: : : the practice of using overlapping scans or thin slices in serial CT for high quality 3D display or multiplanar reconstructions is replaced by the possibility of reconstructing overlapping images from one helical scan volume data set bbbMMMextremely shortened examination time: bbbMMM*: : : makes it possible to acquire continuous patient data during a single breathhold; problems with inconsistent respiration can thereby be avoided bbbMMM*: : : disturbances due to involuntary movements such as peristalsis and cardiovascular action are reduced bbbMMM *: : : may optimize scanning with the use of intravenous contrast media (10,11) bbbMMM """"""""bbbMMMimages can be reconstructed for any couch position in the volume of investigation: bbbMMM*: : : anatomical misregistration is avoided bbbMMM*: : : equivocal lesions can be further evaluated without additional patient exposure bbbMMM*: : : the possibility of displaying the data volume in transverse slices reconstructed at intervals smaller than the xray beam collimation results in overlapping slices which, in combination with reduced or eliminated movement artefacts, makes it possible to perform high quality threedimensional (3D) and multi planar reconstructions with smooth tissue contours. This is used especially in skeletal (12) and vascular imaging (CT angiography) (10). """"""""bbbHelical CT, however, has drawbacks such as: bbbMMMease of performance may tempt the operator to extend the examination unjustifiably, either by increasing the imaging volume, or by repeated exposure of a region bbbMMMalthough most image quality parameters are equivalent for contiguous serial CT and helical CT performed with a pitch = 1 (13,14), the performance of helical CT with a pitch greater than 1.5 may imply lower and possibly insufficient diagnostic image quality due to reduced low contrast resolution (10,14) bbbMMMspatial resolution in the zdirection is lower than indicated by the nominal slice width (13,15) unless special interpolation is performed (15) bbMMMthe technique has inherent artefact bbbWhen using helical CT in conjunction with intravenous injection of contrast media to provide optimally enhanced images, careful timing of exposure relative to intravenous injection is mandatory. 2.5bbbImage viewing conditions bbbIt is recommended that initial reading of CT images is carried out from the TV monitor. Display of images and postprocessing image reconstruction should be at a display matrix of at least 512 x 512. bbbBrightness and contrast control on the viewing monitor should be set to give a uniform progression of the grey scale from black to white. A calibrated greyscale would be preferable. bbbSettings of window width and window level dictate the visible contrast between tissues and should generally be chosen to give optimum contrast between normal structures and lesions. 2.6bbbFilm Processing bbbOptimal processing of the film has important implications for the diagnostic quality of the image stored on film. Film processors should be maintained at their optimum operating conditions as determined by the manufacturer and by regular and frequent quality control procedures. 3.bbbPhysical Parameters: Physical Measures of Scanner Performance.#&R2P)&P# bbbThe quality of the CT image may be expressed in terms of physical parameters such as uniformity, linearity, spatial resolution, low contrast resolution and absence of artefacts according to IEC recommendations (16). It depends on the technological characteristics of the CT scanner, the exposure factors used and image viewing conditions. Quality may be assessed by quantitative measurement of the parameters listed above, using suitable test phantoms, and by the appearance of artefacts. These measurements should be conducted regularly, in order to guarantee the maintenance of performance of the CT scanner during its whole period of use. It is essential that such technical quality control has been performed when using the criteria presented in these guidelines. 3.1bbbTest Phantoms bbbTest phantoms (phantom of a standardised human shape or test objects of a particular shape, size and structure) are used for the purposes of calibration and evaluation of the performance of CT scanners. Performance is checked by acceptance tests after installation and important repairs, and by periodic quality control tests, as established in standardised protocols. A number of test phantoms are commercially available and most manufacturers provide one or more test objects. bbbThe test phantoms should allow for the following parameters to be checked: mean CT number, uniformity, noise, spatial resolution, slice thickness, dose and positioning of couch (16). 3.2bbbCT Number bbbThe accuracy of CT number is verified by scanning a test object utilising the usual operating parameters and reconstruction algorithms. The CT number is affected by the xray tube voltage, beam filtration and object thickness. The CT number of water is by definition equal to 0 HU and the mean CT number measured over the central region of interest (ROI) should be in the range +/ 4HU. bbb 3.3bbbLinearity bbbLinearity concerns the linear relationship between the calculated CT number and the linear attenuation coefficient of each element of the object. It is essential for the correct evaluation of a CT image and, in particular, for the accuracy of QCT. Deviations from linearity should not exceed +/ 5HU over specific ranges (soft tissue or bone). bbb 3.4bbbUniformity bbbUniformity relates to the requirement for the CT number of each pixel in the image of a homogeneous object to be the same within narrow limits over various regions of the object such as a cylindrical 20 cm diameter phantom of waterequivalent plastic. The difference in the mean CT number between a peripheral and a central region of a homogeneous test object should be 8HU. Such differences are largely due to the physical phenomenon of beam hardening. 3.5bbbNoise bbbPicture element (pixel) or image noise is the local statistical fluctuation in the CT numbers of individual picture elements of a homogeneous ROI. Noise is dependent on the radiation dose and has a marked effect on low contrast resolution. The magnitude of the noise is indicated by the standard deviation of the CT numbers over a ROI in a homogeneous substance. It should be measured over an area of about 10% of the crosssectional area of the test object. Image noise diminishes with the use of a slightly flattened convolution kernel, with simultaneous reduction of spatial resolution and an increase in low contrast resolution. Image noise is inversely proportional to the square root of the dose and to the slice thickness. For example, if the dose is halved then the noise will only increase by about 40%. Conversely, a reduction in slice thickness requires a proportionate increase in dose in order to avoid an increase in noise. The medical problem under study and the corresponding image quality required should determine what level of image noise and what patient dose are reasonably practicable. 3.6bbbSpatial Resolution bbbSpatial resolution at high and low contrast are interdependent and critical to image quality and good imaging of diagnostically important structures. bbbThe spatial resolution at high contrast (high contrast resolution) determines the minimum size of detail visualised in the plane of the slice with a contrast 10%. It is affected by the reconstruction algorithm, the detector width, the slice thickness, the object to detector distance, the xray tube focal spot size, and the matrix size.bbbThe spatial resolution at low contrast (low contrast resolution) determines the size of detail that can be visibly reproduced when there is only a small difference in density relative to the surrounding area. Low contrast resolution is considerably limited by noise. The perception threshold in relation to contrast and detail size can be determined, for example, by means of a contrastdetail curve. In such determinations, the effects of the reconstruction algorithm and of the other scanning parameters have to be known. Dose and the corresponding image noise greatly affect low contrast resolution. bbb 3.7bbbSlice Thickness bbbThe slice thickness is determined in the centre of the field of view as the distance between the two points on the sensitivity profile along the axis of rotation at which response has fallen to 50%. Certain deviations in thickness should not be exceeded because of the effect of slice thickness on image detail; for example, with a nominal slice thickness 8mm, a maximum deviation of  10% is acceptable; tolerable deviations for smaller slice thickness of 28 mm and < 2 mm are  25% and #&R2P*&P# 50%, respectively. bbbThe use of postpatient collimation, which is inherent in some CT equipment to reduce the slice sensitivity profile, leads to significant increases in the patient dose for a series of contiguous slices (9). 3.8bbbStability of CT numbers bbbStability is defined as the maintenance over time of constancy of CT number and of uniformity. It can be checked by means of a suitable test object, containing at least three specimens of different materials, e.g. water, Polymethylmethacrylate (PMMA) and Teflon. Deviations should not exceed +/ 5 CT numbers with respect to initial mean values. A similar tolerance should be applied in the verification of uniformity, as measured in three ROIs, each containing approximately 100 pixels and placed respectively at the centre, at the periphery, and in a position intermediate between the centre and the periphery of the reconstructed image. 3.9bbbPositioning of couch bbbThe accuracy of positioning of the patient couch is evaluated by moving the loaded couch a defined distance relative to the gantry and subsequently moving it back to the start position (16). Positional accuracy includes both deviation in longitudinal positioning and also backlash. Maximum tolerances of 2 mm apply to both criteria. These also apply to mobile CT equipment. #XZ2P+XP#GUIDANCE ON IMPLEMENTATION#&R2P,&P# Quality Criteria are presented for a number of selected CT examinations. They apply to adult patients of standard size (~70kg mass and ~170cm height) undergoing usual application of the technique for the type of examination under consideration. These Quality Criteria are to be used by radiologists, operators and medical physicists as a check on the routine performance of the entire imaging process. The Quality Criteria are helpful for the immediate checking of the quality of imaging performance while the patient is still in the scanner. However, the Quality Criteria cannot be applied to all cases. For certain clinical indications a lower level of image quality may be acceptable but this should always be associated with a lower radiation dose to the patient. For each selected CT examination certain preparatory steps are necessary to ensure full justification and accurate control of the examination: Indications, Advisable preliminary investigations, Patient preparation and Scan projection radiograph. These will be given at the top of the List of Quality Criteria for each type of examination. The Quality Criteria are divided into the following three parts that are generally characteristic for the CT procedures, in addition to a fourth part which takes into account special clinical conditions: Lyn1..bbbDIAGNOSTIC REQUIREMENTSLyn1.  bbbThese list image criteria which specify important anatomical structures that should be visible in the image to aid accurate diagnosis. A qualitative guide to the necessary degree of visibility of these essential structures is provided in the following Description of Terms. 2.bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT bbbReference dose values are provided as far as available, in relation to technique for a standardsized patient for each type of CT examination considered. These quantities are defined in Appendix 1 to Chapter 1 and discussed in detail in Chapter 2. Lyn1..bbbEXAMPLE OF GOOD IMAGING TECHNIQUELyn1.  bbbThis section provides examples of CT technique parameters which facilitate good imaging performance that is capable of meeting all the above Quality Criteria. If radiologists and operators find that Diagnostic Requirements or Criteria for Radiation Dose to the Patient are not met, then the Example of Good Imaging Technique can be used as a guide to how their technique might be improved. 4.bbbCLINICAL CONDITIONS WITH IMPACT ON IMAGING PERFORMANCE bbbA number of conditions due to patient behaviour and technical particularities are listed which require special awareness and intervention of the operator. #XZ2P-XP#DESCRIPTION OF TERMS USED IN THE LISTS OF QUALITY CRITERIA#&R2P.&P# #XZ2P/XP#Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1. #&R2P0&P# bbbThe listed image criteria refer to characteristic features of imaged anatomical structures that are defined in the region of examination with a specific degree of visibility. At the present time there are no internationally accepted definitions. For the purpose of these guidelines the degree of visibility is defined as follows: 1.1bbb Visualization The organs and structures are detectable in the volume of investigation. 1.2bbb Critical reproduction The structures particular to the specific indication are discriminated to a level essential for diagnosis. This will include the terms: bbb© MMMreproduction details of anatomical structures are visible but not necessarily clearly defined. bbb©MMM visually sharp reproduction anatomical details are clearly defined. #XZ2P1XP#Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT#&R2P2&P# Lyn1.  bbb Diagnostic reference dose values are indicated for two dose descriptors weighted CT DI (CTDIW) and doselength product (DLP) on the basis of absorbed dose to air, in relation to technique for a standardsized patient. 2.1bbbCTDIw is the approximation of average dose over a single slice in the standard head or body CT dosimetry phantom, expressed in terms of absorbed dose to air (mGy). 2.2bbbDLP characterises exposure for a complete examination in relation to linear integration of the dose to the standard head or body CT dosimetry phantom on the basis of absorbed dose to air (mGy cm). 2.3bbbComparison of CTDIw or DLP values for a particular type of procedure provides a useful indication of relative performance. However, data for examinations on different regions of the body can not be compared directly in order to assess relative patient risk. bbbAppendix 1 to Chapter 1 gives further information concerning the definition of these quantities and methods to check compliance with the dose criteria. The derivation of the diagnostic reference dose values and additional background information is given in Chapter 2.  #XZ2P3XP#Lyn1..bbbEXAMPLE OF GOOD IMAGING TECHNIQUE#&R2P4&P# Lyn1.  bbbParameters are listed that contribute to the fulfilment of the Diagnostic Requirements and the Criteria for Radiation Dose to the Patient. 3.1bbb Patient position 3.2 bbbVolume of investigation anatomical landmarks for beginning and end of the scan. 3.3 bbbNominal slice thickness for serial or collimation for helical CT in mm. 3.4 bbbInterslice distance/pitch in mm/factor. 3.5 bbbField of View (FOV) maximum diameter (in cm) of the reconstructed image. 3.6 bbbGantry tilt angle ($) between vertical plane and plane containing the xray tube, the xray scan beam and the detector array. 3.7bbb Xray tube voltage in kV. This should, if possible, be selected so as to achieve the required image quality at lowest practicable dose. 3.8bbb Tube current and exposure time product in mAs. Selection of tube current (mA) and exposure time (s) to determine radiographic exposure (mAs) is of critical importance. Absolute values of mAs cannot be recommended in view of significant differences in operating characteristics between types of scanner. Operators should be aware of the characteristics particular to their scanner and understand the range of settings that are consistent with meeting required image quality and reference dose values. 3.9 bbbReconstruction algorithm broad type of mathematical filter for the reconstruction of the CT image. 3.10 bbbWindow width in HU. Range of CT numbers converted into grey levels and displayed on the image monitor. 3.11 bbbWindow level in HU. Central value of the window used for the display of the reconstructed CT image. 3.12 bbbProtective shielding additional protection devices to reduce exposure of sensitive organs and tissues. #XZ2P5XP#4.bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE#&R2P6&P# bbb Motion patient or organ movements. bbb Problems and pitfalls mostly site specific clinical or technical problems which impede image quality. bbb Modification of technique in order to provide clinically relevant examination in case of technical or diagnostic problems. #i2P7P# x LIST OF QUALITY CRITERIA FOR COMPUTED TOMOGRAPHY #&R2P8&P# `e!#GPage CRANIUM Lyn22bbbBrain, General`E"#I16 Lyn22bbbSkull Base`E"#I18 FACE AND NECK Lyn22bbbFace and Sinuses`E"#I20 Lyn22bbbPetrous Bone`E"#I22 Lyn22bbbOrbits`E"#I24 Lyn22bbbSella and Hypophysis`E"#I26 Lyn22bbbSalivary Glands (Parotid and Submandibular)`E"#I28 Lyn22bbbPharynx`E"#I30 Lyn22bbbLarynx`E"#I32 SPINE Lyn22bbbVertebral and Paravertebral Structures `E"#I34 Lyn22bbbLumbar Spine, Discal Herniation`E"#I36 Lyn22bbbSpinal Cord`E"#I38 CHEST Lyn22bbbChest, General`E"#I40 Lyn22bbbChest, Mediastinal Vessels`E"#I42 Lyn22bbbChest, HRCT (High Resolution Computed Tomography)`E"#I44 ABDOMEN AND PELVIS Lyn22bbbAbdomen, General`E"#I46 Lyn22bbbLiver and Spleen`E"#I48 Lyn22bbbKidneys`E"#I50 Lyn22bbbPancreas`E"#I52 Lyn22bbbAdrenal Glands`E"#I54 Lyn22bbbPelvis, General`E"#I56 BONES AND JOINTS Lyn22bbbOsseous Pelvis`E"#I58 Lyn22bbbOsseous Shoulder`E"#I60   e  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P9&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQh  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm`$"7#i2P:P# BRAIN, GENERAL e bM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`bePreparatory steps: bbbIndications: traumatic lesions, and suspected or known focal or diffuse structural disease of the brain when MRI is contraindicated or not available bbbAdvisable preliminary investigations: clinical neurological examination; MRI is often an alternative examination without exposure to ionizing radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from skull base to vertex; in patients with multiple injuries from cervical vertebra to vertex 1.bbbDIAGNOSTIC REQUIREMENTS Image criteria: 1.1 bbbVisualization of 1.1.1bbbWhole cerebrum 1.1.2bbbWhole cerebellum 1.1.3bbbWhole skull base 1.1.4bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the border between white and grey matter 1.2.2bbbVisually sharp reproduction of the basal ganglia 1.2.3bbbVisually sharp reproduction of the ventricular system 1.2.4bbbVisually sharp reproduction of the cerebrospinal fluid space around the mesencephalon 1.2.5bbbVisually sharp reproduction of the cerebrospinal fluid space over the brain 1.2.6bbbVisually sharp reproduction of the great vessels and the choroid plexuses after intravenous contrast media 2.bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT 2.1bbbCTDIW' ' ' vvv:routine head: 60 mGy 2.2bbbDLP: : : ' ' ' vvv:routine head: 1050 mGy cm 3.bbbEXAMPLES OF GOOD IMAGING TECHNIQUE 3.1bbbPatient position vvv:supine 3.2bbbVolume of investigationvvv:from foramen magnum to the skull vertex 3.3bbbNominal slice thicknessvvv:2-5 mm in posterior fossa; 5-10 mm in hemispheres 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:head dimension (about 24 cm) 3.6bbbGantry tilt vvv:1012$ above the orbito-meatal (OM) line to reduce exposure of the eye lenses 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and vvv:should be as low as consistent with bbbexposure time product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:soft tissue 3.10bbbWindow width vvv:090 HU (supratentorial brain) bbbMMM: : : ' ' ' vvv140160 HU (brain in posterior fossa) bbbMMM: : : ' ' ' vvv20003000 HU (bones) 3.11bbbWindow level vvv:4045 HU (supratentorial brain) bbbMMM: : : ' ' ' vvv3040 HU (brain in posterior fossa) bbbMMM: : : ' ' ' vvv200400 HU (bones) 4.bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE 4.1bbbMotion ' ' ' vvv©movement artefact deteriorates image quality (prevented by head fixation or sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures, enhancing lesions and alterations of blood-brain barrier bbbMMM: : : ' ' '  4.3bbbProblems and pitfalls vvv©calcifications versus contrast enhancement bbbMMM: : : ' ' ' vvv©interpetrous beam hardening artefacts 4.4bbbModification to technique vvv©;;;subtle irregularity can be checked with slices in the area of suspected pathology, before considering contrast administration   DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P;&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#XZ2P<XP#`]$"<#i2P=P# SKULL BASE ć Preparatory steps: bbbIndications: neurological diseases (cranial nerves), trauma, malformations, metastasis and bone diseases bbbAdvisable preliminary investigations: x-ray examination of the skull and base may only occasionally be necessary; MRI may be an alternative examination without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from C2 to skull vertex Lyn1..bbb DIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire skull base from C1 to the suprasellar region 1.1.2bbbEntire cerebellum 1.1.3bbbBasal part of the frontal lobes 1.1.4bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the cortical and trabecular bone structures 1.2.2bbbVisually sharp reproduction of the air filled compartments 1.2.3bbbVisually sharp reproduction of the sella turcica 1.2.4bbbVisually sharp reproduction of the cerebellar contours 1.2.5bbbReproduction of the border between the white and grey matter (cerebellum) 1.2.6bbbVisually sharp reproduction of the cerebrospinal fluid space around the brain stem 1.2.7bbbVisually sharp reproduction of the great vessels and choroid plexuses after intravenous contrast media Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine 3.2bbbVolume of investigationvvv:from C1 to the suprasellar region 3.3bbbNominal slice thicknessvvv:2-5 mm 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:head dimension (about 24 cm) 3.5bbbGantry tilt vvv:OM line 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with bbbtime product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:high resolution or soft tissue/standard 3.10bbbWindow width vvv:20003000 HU (bones) bbbMMM: : : ' ' ' vvv7090 HU (supratentorial brain) bbbMMM: : : ' ' ' vvv100160 HU (brain in posterior fossa) 3.11bbbWindow level vvv:200400 HU (bones) bbbMMM: : : ' ' ' vvv4045 HU (supratentorial brain) bbbMMM: : : ' ' ' vvv3040 HU (brain in posterior fossa) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion ' ' ' vvv©movement artefact deteriorates image quality (prevented by head fixation or sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures, enhancing lesions and alterations of blood-brain barrier bbbMMM: : : ' ' '  4.3bbbProblems and pitfallsvvv©calcifications versus contrast enhancement bbbMMM: : : ' ' ' vvv©interpetrous beam hardening artefacts 4.4bbbModification to technique vvv©;;;subtle irregularity can be checked with slices in the area of suspected pathology, before considering contrast administration bbMM: : : ' ' ' vvv© higher mAs may be required if artefacts degrade the image quality in the posterior fossa f  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P>&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2P?P# `D$"5FACE AND SINUSES f Preparatory steps: bbbIndications: trauma, malformations, malignancies and inflammation bbbAdvisable preliminary investigations: appropriate x-ray examination of the face except for isolated evaluation of the sinuses; MRI may be an alternative examination, especially in malignancies bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from jaw to vertex Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria 1.1bbbVisualization of 1.1.1bbbEntire face from palate to the top of the frontal sinus 1.1.2bbbVessels after intravenous contrast media 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the cortical and trabecular bone structures 1.2.2bbbVisually sharp reproduction of the frontal sinuses 1.2.3bbbVisually sharp reproduction of the sphenoid sinuses 1.2.4bbbVisually sharp reproduction of the orbitae 1.2.5bbbReproduction of the globe, optic nerve and orbital muscles 1.2.6bbbVisually sharp reproduction of the ethmoid 1.2.7bbbVisually sharp reproduction of the maxilla and its sinuses 1.2.8bbbVisually sharp reproduction of the nasal cavity 1.2.9bbbVisually sharp reproduction of the rhinopharynx Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' '  vvv:35 mGy (pilot study (17)) 2.2bbbDLP: : : ' ' ' vvv:360 mGy cm (pilot study) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine for axial scans; supine or prone for coronal scans 3.2bbbVolume of investigationvvv:from palate to the top of the frontal sinus 3.3bbbNominal slice thicknessvvv:3-5 mm. Helical CT is preferable for evaluation of the face 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0; 12 mm or a pitch up to 1.2 1.5 may be used in screening examinations of the sinuses 3.5bbbFOV: : : ' ' ' vvv:head dimension (about 24 cm) 3.6bbbGantry tilt vvv:0 to 10$ from OM for axial scanning of the face; according to the patient position for coronal scanning 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with bbbtime product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:high resolution or standard 3.10bbbWindow width vvv:15003000 HU (bones) bbbMMM: : : ' ' ' vvv1401000 HU (soft tissue) 3.11bbbWindow level vvv:200400 HU (bones) bbbMMM: : : ' ' ' vvv30100 HU (soft tissue) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion ' '  !vvv©movement artefact deteriorates image quality (prevented by head fixation or sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures and enhancing lesions 4.3bbbProblems and pitfallsvvv©artefacts from teeth or dental prothesis/fillings 4.4bbbModification to techniquevvv©change of gantry angulation or patient position to avoid artefact bbbMMM: : : ' ' ' vvv©examination of the sinuses in a prone position to keep inflammatory secretion away from the osteomeatal complex bbbMMM: : : ' ' ' vvv©examination of the sinuses preliminary to functional endoscopic sinus surgery is best performed directly in the coronal plane b  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P@&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PAP# `$"9PETROUS BONE b Preparatory steps: bbbIndications: hearing deficits, inflammation, vertigo, facial or acoustic nerve diseases, malformations, bone diseases and trauma bbbAdvisable preliminary investigations: examination of acoustic and labyrinth function, bbbevoked potentials; appropriate x-ray examination of skull, base and petrous bone may only occasionally be necessary; MRI may be an alternative examination without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from mastoid to above skull base Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire petrous bone 1.1.2bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the cortical and trabecular bone structures 1.2.2bbbVisually sharp reproduction of the bone structures of the temporal bone such as the cochlea: ossicular chain, fenestra ovale, facial canal and labyrinth 1.2.3bbbVisually sharp reproduction of the air filled compartments 1.2.4bbbVisually sharp reproduction of the adjacent cerebellum 1.2.5bbbVisually sharp reproduction of the adjacent cerebrum 1.2.6bbbReproduction of border between the white and grey matter 1.2.7bbbVisually sharp reproduction of the great vessels and choroid plexuses after intravenous contrast media Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' '  vvv:no specific value as yet available (for information: routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine, for axial scans; supine or prone for coronal scans 3.2bbbVolume of investigationvvv:from 0.5 cm below to 0.5 cm above the petrous bone #&R2PB&P#3.3bbbNominal slice thicknessvvv:*1-3 mm 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' #&R2PC&P#vvv#&R2PD&P#:head dimension (about 24 cm); secondary reduction of FOV is necessary for evaluation of subtle pathology 3.6bbbGantry tilt vvv:OM line or tilted above OM line for axial scanning; according to the patient position for coronal scanning 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with bbbtime product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:high resolution or standard 3.10bbbWindow width vvv:20003000 HU (bones) bbbMMM: : : ' ' ' vvv#&R2PE&P##&R2PF&P#140160 HU (soft tissue) bbbMMM: : : ' ' ' vvv#&R2PG&P##&R2PH&P#15002500 HU (middle setting) 3.11bbbWindow level vvv:200400 HU (bones) bbbMMM: : : ' ' ' vvv#&R2PI&P##&R2PJ&P#3040 HU (soft tissue) bbbMMM: : : ' ' ' vvv#&R2PK&P##&R2PL&P#150250 HU (middle setting) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates image quality (prevented by head fixation or sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures and enhancing lesions 4.3bbbProblems and pitfalls #&R2PM&P##&R2PN&P#vvv©calcifications versus contrast enhancement bbbMMM: : : ' ' ' #&R2PO&P#vvv#&R2PP&P#ѩinterpetrous bone hardening artefacts 4.4bbbModification to technique vvv©;;;#&R2PQ&P#subtle irregularity can be checked with slices in the area of suspected pathology, before considering contrast administration bbbMMM: : : ' ' ' vvv©higher mAs may be required if artefacts degrade the image quality in the posterior fossa bbbMMM: : : ' ' ' vvv©coronal scans may be used to reduce artefacts bbMM: : ' '  !vvv©intrathecal contrast may be useful to detect small accustic neuromas \  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2PR&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PSP# `$"AORBITS \ Preparatory steps: bbbIndications: structural diseases of the orbits and orbital content, trauma, foreign body bbbAdvisable preliminary investigations: evaluation of visual function; evoked potentials; appropriate x-ray examination of the orbits may occasionally be necessary; MRI and ultrasonography may be alternative examinations without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from jaw to vertex Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire orbits 1.1.2bbbOsseous walls 1.1.3bbbVessels after intravenous contrast media 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the osseous walls 1.2.2bbbVisually sharp reproduction of the optic nerve canal 1.2.3bbbVisually sharp reproduction of the globe 1.2.4bbbVisually sharp reproduction of the optic nerve 1.2.5bbbVisually sharp reproduction of the orbital muscles 1.2.6bbbVisually sharp reproduction of the retrobulbar fat 1.2.7bbbVisually sharp reproduction of the main vessels after intravenous contrast media Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine for axial scans; supine or prone for coronal scans 3.2bbbVolume of investigationvvv:from 0.5 cm below to 0.5 cm above the orbital cavity 3.3bbbNominal slice thicknessvvv:2-5 mm 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:head dimension (about 24 cm); secondary reduction of FOV is necessary for evaluation of subtle pathology3.6bbbGantry tilt vvv:©6 to 10$ from OM or parallel to the optic nerve for axial scanning; according to the patient position for coronal scanning 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with bbbtime product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:high resolution or standard 3.10bbbWindow width vvv:140300 HU (soft tissue) bbbMMM: : : ' ' ' vvv20003000 HU (bones) bbbMMM: : : ' ' ' vvvabout 4000 HU (special orbit window) 3.11bbbWindow level vvv:3040 HU (soft tissue) bbbMMM: : : ' ' ' vvv200400 HU (bones) bbbMMM: : : ' ' ' vvvabout 0 HU (special orbit window) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates image quality (prevented by head fixation or sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures and enhancing lesions 4.3bbbProblems and pitfallsvvv©calcifications versus contrast enhancement bbbMMM: : : ' ' ' vvv©foreign bodies (beam hardening artefacts) bbbMMM: : : ' ' ' vvv©artefacts from orbital or dental prothesis/fillings 4.4bbbModification to techniquevvv©change of gantry angulation or patient position to avoid artefact j  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2PT&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PUP# `$"0SELLA AND HYPOPHYSIS j Preparatory steps: bbbIndications: suspicion of sellar or hypophyseal alterations (endocrinological diseases, visual defects, alterations of ocular motility) when MRI is contraindicated or not available. MRI is the examination of choice bbbAdvisable preliminary investigations: evaluation of visual function bbbPatient preparation: information about the procedure: restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from C2 to above skull base  1. 1. 1. 1. 1. 1. 1. 1.AutoList18 a1AutoList18bbbDIAGNOSTIC REQUIREMENTS Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire hypophyseal region including osseous walls 1.1.2bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction the osseous limit of the sella 1.2.2bbbVisually sharp reproduction of the hypophysis and its stalk 1.2.3bbbReproduction of intrahypophyseal density differences 1.2.4bbbVisually sharp reproduction of the chiasm and suprasellar cisterns 1.2.5bbbVisually sharp reproduction of the cavernous sinuses and lateral sellar regions 1.2.6bbbVisually sharp reproduction of the main vessels after intravenous contrast media 2.bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT 2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information:routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) 3.bbbEXAMPLES OF GOOD IMAGING TECHNIQUE 3.1bbbPatient position vv':supine for axial scans; supine or prone for coronal scans 3.2bbbVolume of investigationvvv:from 0.5 cm below to 0.5 cm above the hypophyseal region 3.3bbbNominal slice thicknessvvv:2-3 mm 3.4bbbInterslice distance/pitch!vvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:head dimension (about 24 cm); secondary reduction of FOV is necessary for evaluation of subtle pathology 3.6bbbGantry tilt vvv:OM line for axial scanning; according to the patient position for coronal scanning 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue or high resolution 3.10bbbWindow width vvv:140300 HU (soft tissue) bbbMMM: : : ' ' ' vvv20003000 HU (bones) 3.11bbbWindow level vvv:3040 HU (soft tissue) bbbMMM: : : ' ' ' vvv200400 HU (bones)  1. 1. 1. 1. 1. 1. 1.2AutoList19 a1AutoList19bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE 4.1bbbMotion' ' ' vvv©movement artefact deteriorates image quality (prevented by head fixation or sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures, enhancing lesions and alterations of blood-brain barrier 4.3bbbProblems and pitfallsvvv©calcifications versus contrast enhancement bbbMMM: : : ' ' ' vvv©foreign bodies (beam hardening artefacts) bbbMMM: : : ' ' ' vvv©artefacts from dental prothesis/fillings 4.4bbbModification to techniquevvv©change of gantry angulation or patient position to avoid artefact   DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2PV&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PWP# `% $"SALIVARY GLANDS (PAROTID AND SUBMANDIBULAR) ā Preparatory steps: bbbIndications: lateral facial mass; recurrent parotid or submandibular swelling; T/N staging of salivary gland neoplasms bbbAdvisable preliminary investigations: radiography if calculus is suspected; ultrasonography or MRI may be alternative examinations without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from orbital region to glottis Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1bbbVisualization of 1.1.1bbbEntire parotid gland 1.1.2bbbEntire submandibular gland 1.1.3bbbOverlaying subcutaneous fat and skin 1.1.4bbbRegional lymph node territories (in cases of neoplasm) 1.1.5bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the glandular tissue 1.2.2bbbVisually sharp reproduction of the margins of normal glands 1.2.3bbbVisually sharp reproduction of the paraglandular fat spaces 1.2.4bbVisually sharp reproduction of regional lymph node areas 1.2.5bbReproduction of the mandible and associated muscles 2.bbCRITERIA FOR RADIATION DOSE TO THE PATIENT 2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine 3.2bbbVolume of investigationvvv:parotid: from external ear to angle of jaw; submandibular gland: from dorsum of tongue to hyoid bone; from external ear to glottis if detection of lymphadenopathy is required 3.3bbbNominal slice thicknessvvv:35 mm 3.4bbbInterslice distance/pitchvvv:contiguous, but for large lesions distances of <35 mm or a pitch up to 1.5 2.0 may be used 3.5bbbFOV: : : ' ' ' vvv:adjusted to the minimum required to demonstrate complete cross section of the face. Reduction of FOV may be necessary for the evaluation of subtle pathologies 3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbb time product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard or if necessary high resolution 3.10bbbWindow width vvv:250500 HU 3.11bbbWindow level vvv:030 HU (unenhanced examination) bbbMMM: : : ' ' ' vvv3060 HU (enhanced examination) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality (prevented by quiet respiration; swallowing should be suspended during exposure but encouraged between exposures to avoid salivary pooling) 4.2bbbIntravenous contrast mediavvv©may be required to distinguish lymphadenopathy and blood vessels bbbMMM: : : ' ' ' vvv©for better definition of lesionsO O O bbbMMM: : : ' ' ' vvv©for demonstrating involvement of cranium by neoplasms 4.3bbbProblems and pitfalls vvv©artefact from dental prothesis/fillings bbbMMM: : : ' ' ' vvv©movement artefact due to swallowing bbbMMM: : : ' ' ' vvv©submandibular lymphadenopathy may mimic enlarged submandibular glands 4.4bbbModification to techniquevvv©extension of the examination to the cranium to demonstrate relationship of disease to the base of the skull and the parapharyngeal space bbbMMM: : : ' ' ' vvv©change of gantry angulation or patient position to avoid artefact ]  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2PX&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PYP# `$"?PHARYNX ] Preparatory steps: bbbIndications: diagnosis of parapharyngeal masses; T/N staging of pharyngeal neoplasms bbbAdvisable preliminary investigations: endoscopy may be performed; MRI and ultrasonography may be alternative examinations without exposure to ionising radiation, ultrasonography especially with regard to surrounding structures bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from orbital roof to root of neck 1.bbDIAGNOSTIC REQUIREMENTS Image criteria: 1.1bbbVisualization of 1.1.1bbbEntire pharynx 1.1.2bbbRegional lymph node areas and associated muscles 1.1.3bbbBase of the skull 1.1.4bbbOesophagopharyngeal junction 1.1.5bbbVessels after intravenous contrast media 1.2bbbCritical reproduction 1.2.1bbbReproduction of the wall of pharynx throughout the area of examination 1.2.2bbbVisually sharp reproduction of the mucosal margin 1.2.3bbbVisually sharp reproduction of the parapharyngeal fat spaces 1.2.4bbbVisually sharp reproduction of the parapharyngeal muscles 1.2.5bbbVisually sharp reproduction of regional lymph node areas Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine 3.2bbbVolume of investigationvvv:nasopharynx: from sphenoid bone to hyoid bone and continue to root of the neck for N-staging of neoplasms; bbbMMM: : : ' ' ' vvvoropharynx/hypopharynx: from palate to root of the neck 3.3bbbNominal slice thicknessvvv:35 mm serial or preferably helical 3.4bbbInterslice distance/pitchvvv:contiguous, but for large lesions distances of <35 mm or a pitch up to 1.5 2 may be used3.5bbbFOV: : ' ' ' vvv:adjusted to the minimum required to demonstrate complete cross section of the face. Reduction of FOV may be necessary for the evaluation of subtle pathologies 3.6bbbGantry tilt !vvv:none 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevv':should be as low as consistent with bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard or if necessary high resolution 3.10bbbWindow width vvv:300500 HU 3.11bbbWindow level vvv:030 HU (unenhanced examination) bbbMMM: : : ' ' ' vvv3060 HU (enhanced examination) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality (swallowing should be suspended during exposure but encouraged between exposures to avoid salivary pooling) 4.2bbbIntravenous contrast mediavvv©may be required to improve contrast between normal and abnormal tissues or characterize some parapharyngeal lesions bbbMMM: : : ' ' ' vvv©routinely required if invasion of the base of the skull is suspected 4.3bbbProblems and pitfallsvvv©artefact from dental prothesis/fillings bbbMMM: : : ' ' ' vvv©apposition of the pharyngeal mucosal folds may obscure pathology bbbMMM: : : ' ' ' vvv©pooling of saliva may mimic pathology bbbMMM: : : ' ' ' vvv©superficial mucosal extent of neoplasms may not be identified bbbMMM: : : ' ' ' vvv©secretion from oropharyngeal neoplasms 4.4bbbModification to techniquevvv©coronal sections for demonstrating the relationship of disease to the skull base bbbMMM: : : ' ' ' vvv©exposure with open mouth or with oral Valsava to open nasopharyngeal folds bbbMMM: : : ' ' ' vvv©change of gantry angulation or patient position to avoid artefact \  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2PZ&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2P[P# `p$"@LARYNX \ Preparatory steps: bbbIndications: T/N staging of neoplasm; evaluation of congenital or post-traumatic abnormalities of airway bbbAdvisable preliminary investigations: MRI and ultrasonography may be alternative examinations without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral from floor of mouth to thoracic inlet 1.bbbDIAGNOSTIC REQUIREMENTS Image criteria: 1.1bbbVisualization of 1.1.1bbbEntire larynx 1.1.2bbbParalaryngeal tissues, including muscles, blood vessels and the thyroid gland 1.1.3bbbRegional lymph node areas 1.1.4bbbSpine and paravertebral muscles. 1.1.5bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbReproduction of the wall of the larynx throughout the area of examination 1.2.2bbbVisually sharp reproduction of the mucosal folds 1.2.3bbbVisually sharp reproduction of the perimucosal fat spaces 1.2.4bbbVisually sharp reproduction of the intrinsic pharyngeal muscles 1.2.5bbbVisually sharp reproduction of the paralaryngeal muscles 1.2.6bbbVisually sharp reproduction of regional lymph node areas 2.bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT 2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine head: 60 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine head: 1050 mGy cm) 3.bbbEXAMPLES OF GOOD IMAGING TECHNIQUE 3.1bbbPatient position vvv:supine 3.2bbbVolume of investigationvvv:from base of tongue to root of neck 3.3bbbNominal slice thicknessvvv:35 mm serial or preferably helical CT, especially in patients having difficulties with salivary pooling 3.4bbbInterslice distance/pitchvvv:contiguous, but for large lesions distances of <35 mm or a pitch up to 1.5 2.0 may be used 3.5bbbFOV: : : ' ' ' vvv:adjusted to the minimum required to demonstrate complete cross section of the neck. Reduction of FOV may be necessary for the evaluation of subtle pathologies 3.5bbbGantry tilt vvv:none or modified parallel to the line of vocal folds on scan projection radiograph 3.6bbbXray tube voltage (kV)vvv:standard 3.7bbTube current and exposurevvv:*should be as low as consistent with required bbbtime product (mAs)!vv'image quality 3.8bbbReconstruction algorithmvvv:soft tissue/standard or if necessary high resolution 3.9bbbWindow width vvv:250500 HU 3.10bbbWindow level vvv:030 HU (unenhanced examination) bbbMMM: : : ' ' ' vvv3060 HU (enhanced examination) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion ' ' ' vvv©movement artefact deteriorates the image quality (avoided by quiet respiration; swallowing should be suspended during exposure but encouraged between exposures to avoid salivary pooling) 4.2bbbIntravenous contrast mediavv'may be required to distinguish lymphadenopathy bbbMMM: : : ' ' ' vvv©improves delineation of neoplasm 4.3bbbProblems and pitfallsvvv©movement artefact due to respiration bbbMMM: : : ' ' ' vvv©staging errors due to poor discrimination between normal and abnormal tissues bbbMMM: : : ' ' ' vvv©salivary pooling may mimic pathology bbbMMM: : : ' ' ' vvv©displacement of vocal fold by adjacent mass may mimic glottal involvement 4.4bbbModification to techniquevvv©reformatted images may require thin serial slices if helical CT is not available bbbMMM: : : ' ' ' vvv©sections through glottis may be obtained during phonation |  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P\&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2P]P# ` $"VERTEBRAL AND PARAVERTEBRAL STRUCTURES | Preparatory steps: bbbIndications: traumatic lesions and as a guide to biopsy; also structural diseases of the vertebrae, medulla and paravertebral tissues, if MRI is contraindicated or not available. MRI is the examination of choice in nontraumatic disorders bbbAdvisable preliminary investigations: radiography of the vertebral column, and in some patients myelography bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal or lateral of the suspected diseased region Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1bbbVisualization of 1.1.1bbbThe entire region of suspected pathology 1.1.2bbbVessels after intravenous contrast media 1.1.3bbbSpinal cord and nerve roots after intrathecal injection of contrast media (CTmyelography) 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the cortical and trabecular bone 1.2.2bbbVisually sharp reproduction of the intervertebral joints 1.2.3bbbVisually sharp reproduction of the intervertebral disk profiles 1.2.4bbbVisually sharp reproduction of the intervertebral radicular canals 1.2.5bbbReproduction of the thecal sac 1.2.6bbbVisually sharp reproduction of the spinal cord or cauda equina (CTmyelography) 1.2.7bbbReproduction of the paravertebral ligaments 1.2.8bbbVisually sharp reproduction of the paravertebral muscles 1.2.9bbbReproduction of the main vessels and perithecal venous plexuses after intravenous contrast medium Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:70 mGy for vertebral trauma (pilot study (17)) 2.2bbbDLP: : ' ' ' vvv:460 mGy cm for vertebral trauma (pilot study) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine 3.2bbbVolume of investigationvvv:from 1 cm above to 1 cm below the region of suspected pathology 3.3bbbNominal slice thicknessvvv:2-5 mm 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:dimension corresponding to the spine and surrounding paravertebral structures 3.6bbbGantry tilt vvv:none (allow easy production of reformatted images) or parallel to the intervertebral disks 3.7bbbXray tube voltage (kV)vvv:standard or high kV in large persons to avoid noise 3.8bbbTube current and exposurevv':should be as low as consistent with bbbtime product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:soft tissue or high resolution 3.10bbbWindow width vvv:140350 HU (soft tissue) bbbMMM: : : ' ' ' vvv20003000 HU (bones) bbbMMM: : : ' ' ' vvv300400 HU (cervical spine) 3.11bbbWindow level vvv:3040 HU (soft tissue) bbbMMM: : : ' ' ' vvv200400 HU (bones) bbbMMM: : : ' ' ' vvv2535 HU (cervical spine) 3.12bbbProtective shieldingvvv:leadpurse for the male gonads if the edge of the volume of investigation is less than 1015 cm away Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion ' ' ' vvv©movement artefact deteriorates image quality (prevented by sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures and enhancing lesions 4.3bbbProblems and pitfallsvvv©foreign bodies (beam hardening artefacts) 4.4bbbModification to techniquevvv©production of reformatted images of adequate quality may require thin serial slices if helical CT is not available u  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P^&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2P_P# `$"%LUMBAR SPINE, DISCAL HERNIATION u Preparatory steps: bbbIndications: radiculopathy (sciatica), back pain, failure of conservative treatment and postoperative back pain, especially when MRI is contraindicated bbbAdvisable preliminary investigations: radiography of the spine; electromyography; MRI is a preferable alternative examination without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: lateral of the suspected diseased disks Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1bbbVisualization of 1.1.1bbbThe entire region of suspected pathology 1.1.2bbbVessels after intravenous contrast media 1.1.3bbbSpinal cord and nerve roots after intrathecal injection of contrast media (CT-myelography) 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the intervertebral disk profiles 1.2.2bbbVisually sharp reproduction of the thecal sac 1.2.3bbbVisually sharp reproduction of the perithecal fat 1.2.4bbbVisually sharp reproduction of the intervertebral radicular canals 1.2.5bbbVisually sharp reproduction of the nerve roots 1.2.6bbbReproduction of the main vessels and perithecal venous plexuses after intravenous contrast media 1.2.7bbbReproduction of the cortical and trabecular bone 1.2.8bbbVisually sharp reproduction of the intervertebral joints 1.2.9bbbReproduction of the paravertebral ligaments Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine abdomen: 35 mGy) 2.2bbbDLP: : : ' ' '  vvv:no specific value as yet available (for information: routine abdomen: 800 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position !vvv:supine, legs in flexion 3.2bbbVolume of investigationvvv:from pedicle to pedicle with targeting of a slice at the centre of the suspected diseased disks 3.3bbbNominal slice thicknessvvv:2-5 mm 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:spine dimension 3.6bbbGantry tilt vvv:as parallel as possible to the intervertebral disc planes; a different gantry tilt may be required for each intervertebral space 3.7bbbXray tube voltage (kV)vvv:standard or high kV in large persons to avoid noise 3.8bbbTube current and exposurevvv:should be as low as consistent with bbbtime product (mAs)vvvrequired image quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard or high resolution 3.10bbbWindow width vvv:140400 HU (soft tissue) bbbMMM: : : ' ' ' vvv20003000 HU (bones) bbbMMM: : : ' ' ' vvv250300 HU (lumbar spine) 3.11bbbWindow level vvv:3040 HU (soft tissue) bbbMMM: : : ' ' ' vvv200400 HU (bones) bbbMMM: : : ' ' ' vvv2535 HU (lumbar spine) 3.12bbbProtective shieldingvvv:leadpurse for the male gonads if the edge of the volume of investigation is less than 1015 cm away Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates image quality (prevented by sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures and enhancing lesions 4.3bbbProblems and pitfallsvvv©foreign bodies (beam hardening artefacts) bbbMMM: : : ' ' ' vvv©calcifications versus contrast enhancement 4.4bbbModification to techniquevvv©intrathecal injection of contrast medium (CT- myelography) to delineate the spinal cord and nerve roots a  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2P`&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PaP# `$";SPINAL CORD a Preparatory steps: bbbIndications: tetraparesis, paraparesis, other neurological deficits and spinal cord compression syndrome when MRI is contraindicated or not available. MRI is the examination of choice bbbAdvisable preliminary investigations: radiography of the spine and/or myelography bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal or lateral of all the suspected vertebral segments Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1bbbVisualization of 1.1.1bbbThe entire region of suspected pathology 1.1.2bbbVessels after intravenous contrast media 1.1.3bbbSpinal cord and nerve roots after intrathecal injection of contrast media (CT-myelography) 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of spinal cord contours (CT-myelography) 1.2.2bbbVisually sharp reproduction of the thecal sac 1.2.3bbbVisually sharp reproduction of the perithecal fat 1.2.4bbbVisually sharp reproduction of the intervertebral disk profiles 1.2.5bbbReproduction of the main vessels and perithecal venous plexuses after intravenous contrast media 1.2.6bbbVisually sharp reproduction of the intervertebral radicular canals 1.2.7bbbVisually sharp reproduction of the intervertebral joints 1.2.8bbbReproduction of the paravertebral ligaments 1.2.9bbbVisually sharp reproduction of the paravertebral muscles Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine chest or abdomen: 30/35 mGy) 2.2bbbDLP: : ' ' ' vvv:no specific value as yet available (for information: routine chest or abdomen: 650/800 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine, legs in flexion 3.2bbbVolume of investigationvvv:from 1 cm above to 1 cm below suspected pathology 3.3bbbNominal slice thicknessvvv:*2-5 mm 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.03.5bbbFOV: : : ' ' ' vvv:spine dimension9? 3.6bbbGantry tilt vvv:none (allow easy production of reformatted images) 3.7bbbXray tube voltage (kV)vvv:standard or high kV in large persons to avoid noise 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard or high resolution 3.10bbbWindow width vvv:140400 HU (soft tissue) bbbMMM: : : ' ' ' vvv20003000 HU (bones) bbbMMM: : : ' ' ' vvv250300 HU (cervical spine) bbbMMM: : : ' ' ' vvv30004000 HU (CT-myelography) 3.11bbbWindow level vvv:3040 HU (soft tissue) bbbMMM: : : ' ' ' vvv200400 HU (bones) bbbMMM: : : ' ' ' vvv2535 HU (cervical spine) bbbMMM: : : ' ' ' vvv400600 HU (CT-myelography) 3.12bbbProtective shieldingvvv:leadpurse for the male gonads if the edge of the volume of investigation is less than 1015 cm away Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates image quality (prevented by sedation of non-cooperative patients) 4.2bbbIntravenous contrast mediavvv©useful to identify vascular structures and enhancing lesions 4.3bbbProblems and pitfallsvvv©foreign bodies (beam hardening artefacts) bbbMMM: : : ' ' ' vvv©calcifications versus contrast enhancement 4.4bbbModification to techniquevvv©intrathecal injection of contrast medium (CT- myelography) to delineate the spinal cord and nerve roots bbbMMM: : : ' ' ' vvv©production of reformatted images of adequate quality may require thin serial slices if helical CT is not available d  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Pb&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PcP# `#$"7CHEST, GENERAL d Preparatory steps: bbbIndications: suspected or known pulmonary, pleural or lymph node disease, including metastatic neoplasms, infection, traumatic lesions and focal diseases bbbAdvisable preliminary investigations: chest radiography bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from neck to upper abdomen Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire thoracic wall 1.1.2bbbEntire thoracic aorta and vena cava 1.1.3bbbEntire heart 1.1.4bbbEntire lung parenchyma 1.1.5bbbVessels after intravenous contrast media 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the thoracic aorta 1.2.2bbbVisually sharp reproduction of the anterior mediastinal structures, including thymic residue (if present) 1.2.3bbbVisually sharp reproduction of the trachea and main bronchi 1.2.4bbbVisually sharp reproduction of the paratracheal tissue 1.2.5bbbVisually sharp reproduction of the carina and lymph node area 1.2.6bbbVisually sharp reproduction of the oesophagus 1.2.7bbbVisually sharp reproduction of the pleuromediastinal border 1.2.8bbbVisually sharp reproduction of large and medium sized pulmonary vessels 1.2.9bbbVisually sharp reproduction of segmental bronchi 1.2.10bbbVisually sharp reproduction of the lung parenchyma 1.2.11bbbVisually sharp reproduction of the border between the pleura and the thoracic wall Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:routine chest: 30 mGy 2.2bbbDLP: : : ' '  vvv:routine chest: 650 mGy cm Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine, arms above the head 3.2bbbVolume of investigationvvv:from lung apex to the base of the lungs 3.3bbbNominal slice thicknessvvv:710 mm serial or preferably helical 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0; 45 mm or pitch up to 1.5 may be used for large lesions or detection of lymphadenopathy alone; even larger interslice distance/pitch may be applied in critically ill patients 3.5bbbFOV: : : ' ' ' vvv:adjusted to largest thoracic diameter within the volume of investigation 3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard 3.10bbbWindow width vvv:300600 HU (soft tissue) bbbMMM: : : ' ' ' vvv8001.600 HU (lung parenchyma) 3.11bbbWindow level vvv:030 HU (soft tissue, unenhanced examination) bbbMMM: : : ' ' ' vvv3060 HU (soft tissue, enhanced examination) bbbMMM: : : ' ' ' vvv500700 HU (lung parenchyma) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbMotion' ' ' vvv©movement artefact deteriorates the image quality. This is prevented by a standard breathhold technique; alternatively if this is not possible scan during quiet respiration 4.2bbbIntravenous contrast mediavvv©may be used to characterise lesions or to distinguish them from vessels 4.3bbbProblems and pitfalls vvv©anatomical misregistration due to variation in the phase of respiration bbbMMM: : : ' ' ' vvv©focal atelectasis may obscure pathology bbbMMM: : : ' ' ' vvv©motion artefact due to cardiac pulsation or respiration 4.4bbbModification to techniquevvv©prone position may be used to elucidate pleural lesions or focal spaces bbbMMM: : : ' ' ' vvv©the examination may be confined to a specific area of interest bbbMMM: : : ' ' ' vvv©4 mm slices may be used for specific examination of hilar pathology and subtle pulmonary lesions p  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Pd&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PeP# `$"*CHEST, MEDIASTINAL VESSELS p Preparatory steps: bbbIndications: suspected or known major vessel aneurysm, dissection or congenital anomaly bbbAdvisable preliminary investigations: chest radiography, including lateral projection; MRI or transoesophageal ultrasonography may be alternative examinations without exposure to ionising radiation bbbPatient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from neck to upper abdomen Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire thoracic aorta 1.1.2bbbEntire vena cava 1.1.3bbbEntire heart 1.1.4bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the contour of the thoracic aorta 1.2.2bbbVisually sharp reproduction of the wall of the thoracic aorta 1.2.3bbbVisually sharp reproduction of the superior vena cava 1.2.4bbbVisually sharp reproduction of the major anterior mediastinal vessels 1.2.5bbbVisually sharp reproduction of the heart 1.2.6bbbVisually sharp reproduction of the inferior vena cava 1.2.7bbbVisually sharp reproduction of large and medium sized pulmonary vessels Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine chest: 30 mGy) 2.2bbbDLP: : : ' ' ' vvv:no specific value as yet available (for information: routine chest: 650 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine, arms above the head 3.2bbbVolume of investigationvvv:may be limited to area of radiographic abnormality or clinically suspected lesion 3.3bbbNominal slice thicknessvvv:45 mm serial or preferably helical 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0; 24 mm or a pitch up to 1.2 1.5 for large lesions 3.5bbbFOV: : : ' ' ' vvv:limited to area of the heart and major vessels3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard 3.10bbbWindow width vvv:100400 HU (soft tissue, unenhanced examination) bbbMMM: : : ' ' ' vvv150500 HU (soft tissue, enhanced examination) 3.11bbbWindow level vvv:050 HU (soft tissue, unenhanced examination) bbbMMM: : : ' ' ' vvv20150 HU (soft tissue, enhanced examination, depends on dose and method of contrast administration) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality. This is prevented by a standard breathhold technique; alternatively if this is not possible scan during quiet respiration 4.2bbbIntravenous contrast mediavvv©enhancement is required for many examinations 4.3bbbProblems and pitfalls vvv©artefact from the cardiac outline may cross the aorta and mimic dissection flap bbbMMM: : : ' ' ' vvv©inhomogeneities in luminal opacification due to inconstant blood flow bbbMMM: : : ' ' ' vvv©inappropriate administration of contrast media may mimic thrombus 4.4bbbModification to techniquevvv©not usually required bbbMMM: : : ' ' ' vvv v  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Pf&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PgP# `1$"$CHEST, HRCT (HIGH RESOLUTION CT) v Preparatory steps: bbbIndications: detection and characterization of diffuse parenchymal lung disease including emphysema or bronchiectasis bbbAdvisable preliminary investigations: chest radiography and respiratory function tests bbbPatient preparation: information about the procedure bbbScan projection radiograph: frontal from neck to upper abdomen Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1bbbVisualization of 1.1.1bbbEntire field of lung parenchyma 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the lung parenchyma 1.2.2bbbVisually sharp reproduction of pulmonary fissures 1.2.3bbbVisually sharp reproduction of secondary pulmonary lobular structures such as interlobular arteries 1.2.4bbbVisually sharp reproduction of large and medium sized pulmonary vessels 1.2.5bbbVisually sharp reproduction of small pulmonary vessels 1.2.6bbbVisually sharp reproduction of large and medium sized bronchi 1.2.7bbbVisually sharp reproduction of small bronchi 1.2.8bbbVisually sharp reproduction of the pleuromediastinal border 1.2.9bbbVisually sharp reproduction of the border between the pleura and the thoracic wall Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:35 mGy (pilot study (17)) 2.2bbbDLP: : : ' ' ' vvv:280 mGy cm (pilot study) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine, arms above the head 3.2bbbVolume of investigationvvv:from lung apex to the base of the lungs (survey) or corresponding to radiographically defined abnormality (localised disease) 3.3bbbNominal slice thicknessvvv:12 mm 3.4bbbInterslice distancevvv:1020 mm 3.5bbbFOV: : : ' ' ' vvv:adjusted to the minimum which will demonstrate the whole lung field 3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (kV)vvv:high kV or standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:high resolution 3.10bbbWindow width vvv:10001600 HU 3.11bbbWindow level vvv:400700 HU Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality and breathhold technique is mandatory 4.2bbbIntravenous contrast mediavvv©not required 4.3bbbProblems and pitfalls vvv©motion artefact due to dyspnoea bbbMMM: : : ' ' ' vvv©atelectasis may obscure pathology 4.4bbbModification to technique vvv©;;;prone position may be used to elucidate dependent changes, especially small areas of atelectasis bbbMMM: : : ' ' ' vvv©examination in suspended expiration to detect air trapping bbbMMM: : : ' ' ' vvv©sections with smaller interslice distance for evaluation of very small areas of disease bbbMMM: : : ' ' ' vvv©sections with a craniocaudal 25 to 30$ gantry tilt for detection of bronchiectasies f  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Ph&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PiP# `$"4ABDOMEN, GENERAL f Preparatory steps: bbbIndications: inflammatory lesions, abscess, suspected or known structural alteration or space occupying lesions of the abdomen and retroperitoneum, lesions of major vessels such as aneurysms and traumatic lesions, and as a guide to biopsy bbbAdvisable preliminary investigations: ultrasonography and/or radiography of the abdomen. MRI may be an alternative examination with regard to the retroperitoneal space bbbPatient preparation: information about the procedure; exclude high density contrast media from previous investigations; oral application of contrast media for the intestine; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from lower chest to pelvis Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of .1 .1 .1 .1 .1 .1 .1 .1 AutoList22a1AutoList22bbbDiaphragm 1.1.2bbbEntire liver and spleen 1.1.3bbbRetroperitoneal parenchymal organs (pancreas, kidneys) 1.1.4bbbAbdominal aorta and the proximal part of the common iliac arteries 1.1.5bbbAbdominal wall including all herniations 1.1.6bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the liver parenchyma and intrahepatic vessels 1.2.2bbbVisually sharp reproduction of the splenic parenchyma 1.2.3bbbVisually sharp reproduction of the intestine 1.2.4bbbVisually sharp reproduction of the perivascular retroperitoneal space 1.2.5bbbVisually sharp reproduction of the pancreatic contours 1.2.6bbbVisually sharp reproduction of the duodenum 1.2.7bbbVisually sharp reproduction of the kidneys and proximal ureters 1.2.8bbbVisually sharp reproduction of the aorta 1.2.9bbbVisually sharp reproduction of the aortic bifurcation and common iliac arteries 1.2.10bbbReproduction of lymph nodes smaller than 15 mm in diameter 1.2.11bbbReproduction of branches of the abdominal aorta 1.2.12bbbVisually sharp reproduction of the vena cava 1.2.13bbbReproduction of tributaries to the vena cava in particular the renal veins Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:routine abdomen: 35 mGy 2.2bbbDLP: : : ' ' ' vvv:routine abdomen: 780 mGy cm Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine with arms at chest or head level 3.2bbbVolume of investigationvvv:from dome of the liver to the aortic bifurcation 3.3bbbNominal slice thicknessvvv:710 mm; 45 mm for dedicated indications only (suspected small lesions), serial or preferably helical 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0; in screening investigations, eg. for traumatic lesions  10 mm or a pitch up to 1.2 2.0 3.5bbbFOV: : : ' ' ' vvv:adjusted to the largest abdominal diameter 3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (Kv)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required ("("H bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:standard or soft tissue 3.10bbbWindow width vvv:150-600 HU bbbMMM: : : ' ' ' vvv2000-3000 HU (bone, if required) 3.11bbbWindow level vvv:30-60 HU (enhanced examination) bbbMMM: : : ' ' ' vvv030 HU (unenhanced examination) bbbMMM: : : ' ' ' vvv400-600 HU (bone, if required) 3.12bbbProtective shieldingvvv:leadpurse for the male gonads if the edge of the volume of investigation is less than 1015 cm away Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality. This is prevented by a standard breathhold technique; alternatively if this is not possible scan during quiet respiration 4.2bbbIntravenous contrast mediavvv©useful for differentiating vessels and organ tissues from adjacent structures and to detect parenchymal lesions in solid organs 4.3bbbProblems and pitfallsvvv©noncontrasted parts of the intestine may mimic tumours bbbMMM: : : ' ' ' vvv©the delineation of organs and structures may be poor in cachectic patients with reduced intraabdominal and retroperitoneal fat 4.4bbbModification to techniquevvv©helical CT which is beneficial for elimination of motion artefact can be used for demonstrating vascular pathologies (CT angiography) bbbMMM: : : ' ' ' vvv©may be combined with examination of the pelvis f  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Pj&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm`b$"6#i2PkP# LIVER AND SPLEEN f Preparatory steps: bbbIndications: suspected or known focal or diffuse disease of the liver, biliary tree, gallbladder, spleen or adjacent structures bbbAdvisable preliminary investigations: ultrasonography; MRI may be an alternative examination without exposure to ionising radiation bbbPatient preparation: information about the procedure; exclude high density contrast media form previous investigations; oral contrast media for bowel and stomach demarcation; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from lower chest to pelvis Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire liver 1.1.2bbbEntire spleen 1.1.3bbbVessels after intravenous contrast media 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the liver parenchyma and intrahepatic portal veins 1.2.2bbbVisually sharp reproduction of the liver veins 1.2.3bbbVisually sharp reproduction of the structures of the liver hilus 1.2.4bbbVisually sharp reproduction of the common hepatic duct 1.2.5bbbReproduction of the ductus choledochus (common bile duct) in the pancreatic parenchyma 1.2.6bbbReproduction of the gallbladder wall 1.2.7bbbVisually sharp reproduction of the splenic parenchyma 1.2.8bbbVisually sharp reproduction of the splenic artery 1.2.9bbbVisually sharp reproduction of the extrahepatic portal vein system including v. lienalis and v. mesenterica sup. 1.2.10bbbVisually sharp reproduction of the aorta and inferior vena cava 1.2.11bbbVisually sharp reproduction of the origin of the coeliac trunk 1.2.12bbbVisually sharp reproduction of the mesenteric artery Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:35 mGy (pilot study (17)) 2.2bbbDLP: : : ' '  vvv:900 mGy cm (pilot study) 3.bbbEXAMPLES OF GOOD IMAGING TECHNIQUE 3.1bbbPatient position vvv:supine with arms at chest or head level 3.2bbbVolume of investigationvvv:from above diaphragm to 1 cm below the caudal end of the liver and spleen 3.3bbbNominal slice thicknessvvv:710 mm; 45 mm if small lesions are suspected, serial or preferably helical 3.4bbbInterslice distancevvv:contiguous or a pitch = 1.0; 10 mm or a pitch up to 1.2 2.0 in screening investigations 3.5bbbFOV: : : ' ' ' vvv:adjusted to the largest diameter of the abdomen within the volume under investigation 3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard 3.10bbbWindow width vvv:150-300 HU 3.11bbbWindow level vvv:40-80 HU (enhanced examination) bbbMMM: : : ' ' ' vvv030 HU (unenhanced examination) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality. This is prevented by standard breath hold technique; alternatively if this is not possible scan during quiet respiration bbbMMM: : : ' ' ' vvv©cardiac motion may cause artefacts in left liver lobe 4.2bbbIntravenous contrast mediavvv©useful to delineate organ tissue and vessels and detect focal lesions in solid organs 22222222AutoList12bbbMMM: : : ' ' ' vvv©multiphased section examination may be indicated 4.3bbbProblems and pitfallsvvv©inconsistent breath holding between slices may obscure subtle pathology in serial CT bbbMMM: : : ' ' ' vvv©differentiation of small hepatic or splenic cysts from tumours can be difficult bbbMMM: : : ' ' ' vvv©inhomogeneous attenuation during initial contrast enhancement may mimic focal hepatic or splenic disease bbbMMM: : : ' ' ' vvv©non-calcified bile stones may not be identifiable 4.4bbbModification to technique vvv©;;;in case of suspected haemangioma, serial CT of the pathology several minutes after injection of contrast media bbMM: : ' '  !vvv©additional thinner slices may be obtained to delineate subtle alterations ]  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Pl&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PmP# `$"@KIDNEYS ] Preparatory steps: bbbIndications: suspected or known focal or diffuse structural disease of the kidneys, and traumatic lesions! bbbAdvisable preliminary investigations: ultrasonography; blood-creatinine (especially prior to administration of contrast media). MRI may be an alternative examination without exposure to ionising radiation bbbPatient preparation: information about the procedure; exclude high density contrast media from previous investigations; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from liver dome to upper pelvis Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1bbb Visualization of 1.1.1bbbBoth kidneys 1.1.2bbbProximal part of the ureters 1.1.3bbbVessels after intravenous contrast media 1.2 bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the renal parenchyma 1.2.2bbbVisually sharp reproduction of the renal pelvis and calices/ 1.2.3bbbVisually sharp reproduction of the proximal part of the ureters 1.2.4bbbVisually sharp reproduction of the perirenal spaces 1.2.5bbbVisually sharp reproduction of the aorta and vena cava 1.2.6bbbVisually sharp reproduction of the renal arteries 1.2.7bbbVisually sharp reproduction of the renal veins Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine abdomen: 35 mGy) 2.2bbbDLP: : : ' '  vvv:no specific value as yet available (for information: routine abdomen: 800 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1bbbPatient position vvv:supine with arms at chest or head level 3.2bbbVolume of investigationvvv:1 cm above the most cranial pole of the kidneys to 1 cm below the most caudal pole; depending on the findings (eg. tumour) extension of the volume may be needed 3.3bbbNominal slice thicknessvvv:4-5 mm for unknown or small pathologies; 7-10 mm for follow up of larger lesions 3.4bbbInterslice distance/pitchvvv:contiguous or a pitch = 1.0 3.5bbbFOV: : : ' ' ' vvv:adjusted to the largest diameter of the abdomen within the volume under investigation; secondary magnification by reducing the FOV may be necessary for evaluation of subtle pathology 3.6bbbGantry tilt vvv:none 3.7bbbXray tube voltage (kV)vvv:standard 3.8bbbTube current and exposurevvv:should be as low as consistent with required bbbtime product (mAs)vvvimage quality 3.9bbbReconstruction algorithmvvv:soft tissue/standard 3.10bbbWindow width vvv:200-400 HU 3.11bbbWindow level vvv:30-150 HU (enhanced examination) bbbMMM: : : ' ' ' vvv0-30 HU (unenhanced examination) Lyn1..bbbCLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE Lyn1.  4.1bbbMotion' ' ' vvv©movement artefact deteriorates the image quality. This is prevented by a standard breathhold technique; alternatively if this is not possible scan during quiet respiration 4.2bbbIntravenous contrast mediavvv-combination of native and contrast enhanced studies are necessary in most patients to characterise lesions or distinguish them from vessels bbbMMM: : : ' ' ' vvv©multiphased section examination may be indicated. An optimal injection protocol is then important bbbMMM: : : ' ' ' vvv 4.3bbbProblems and pitfallsvvv©inconsistent breath holding between slices may obscure subtle pathology in serial CT bbbMMM: : : ' ' ' vvv©differentiation of small cysts from tumours may be difficult bbbMMM: : : ' ' ' vvv©non-calcified stones may not be identifiable `##J 4.4bbbModification to technique vv'-;;;additional thinner slices may be obtained to delineate minor alterations ^  DK .,,. П b' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#&R2Pn&P#  ОbM: ' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`be  Пb' v;O #%(c+(.03w6<9<>APDGILdO)RTWxZ=]`beQhkm#i2PoP# `$">PANCREAS ^ Preparatory steps: bbbIndications: suspected or known focal or diffuse disease of the pancreas or peripancreatic structures! bbbAdvisable preliminary investigations: ultrasonography; laboratory investigations (amylase, lipase). MRI may be an alternative examination without exposure to inonising radiation bbbPatient preparation: information about the procedure; exclude high density contrast media from previous investigations; oral contrast media directly prior to the examination (in right lateral position) to demarcate the duodenum; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given bbbScan projection radiograph: frontal from lower chest to middle abdomen Lyn1..bbbDIAGNOSTIC REQUIREMENTS Lyn1.  Image criteria: 1.1 bbbVisualization of 1.1.1bbbEntire pancreas (head, body, tail, uncinate process) 1.1.2bbbEntire diseased peripancreatic tissue 1.1.3bbbAdjacent parts of liver, spleen, bowels and stomach 1.1.4bbbVessels after intravenous contrast media 1.2bbbCritical reproduction 1.2.1bbbVisually sharp reproduction of the pancreatic contours 1.2.2bbbVisually sharp reproduction of the pancreatic parenchyma 1.2.3bbbReproduction of the pancreatic duct 1.2.4bbbVisually sharp reproduction of the common bile duct within the pancreatic head 1.2.5bbbVisually sharp reproduction of the mesenteric artery and vein 1.2.6bbbVisually sharp reproduction of the splenic artery and vein 1.2.7bbbVisually sharp reproduction of the portal vein 1.2.8bbbVisually sharp reproduction of the coeliac trunk 1.2.9bbbVisually sharp reproduction of diaphragmatic crura 1.2.10bbbVisually sharp reproduction of the aorta 1.2.11bbbVisually sharp reproduction of the vena cava 1.2.12bbbVisually sharp reproduction of the renal vessels 1.2.13bbbVisually sharp reproduction of the duodenum Lyn1..bbbCRITERIA FOR RADIATION DOSE TO THE PATIENT Lyn1.  2.1bbbCTDIW' ' ' vvv:no specific value as yet available (for information: routine abdomen: 35 mGy) 2.2bbbDLP: : : ' '  vvv:no specific value as yet available (for information: routine abdomen: 800 mGy cm) Lyn1..bbbEXAMPLES OF GOOD IMAGING TECHNIQUE Lyn1.  3.1