PELVIS, GENERAL
| Preparatory steps: | |||
| - | Indications: disorders of the prostate, uterus or female gonads and suspected or known focal or diffuse structural disease of the pelvis eg. lymphomas | ||
| - | Advisable preliminary investigations: ultrasonography and MRI are alternative examinations without exposure to ionising radiation; endoscopy (for intraluminal pathology) | ||
| - | Patient preparation: information about the procedure; exclude high density contrast media from previous investigations; administration of oral or rectal contrast media for bowel demarcation; vaginal contrast tampon in gynaecological indications. Urinary bladder should not be empty; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given | ||
| - | Scan projection radiograph: frontal from iliac crest to proximal femur | ||
| 1. | DIAGNOSTIC REQUIREMENTS | ||
| Image criteria: | |||
| 1.1 | Visualization of | ||
| 1.1.1 | Entire iliac bones | ||
| 1.1.2 | Entire ischial bones | ||
| 1.1.3 | Entire pubic symphysis | ||
| 1.1.4 | Entire urinary bladder | ||
| 1.1.5 | All peripelvic muscles | ||
| 1.1.6 | Vessels after intravenous contrast media | ||
| 1.2 | Critical reproduction | ||
| 1.2.1 | Visually sharp reproduction of the bladder wall | ||
| 1.2.2 | Reproduction of the distal portion of the ureters | ||
| 1.2.3 | Visually sharp reproduction of the rectum | ||
| 1.2.4 | Visually sharp differentiation of the perirectal space | ||
| 1.2.5 | Visually sharp reproduction of the uterus | ||
| 1.2.6 | Visually sharp reproduction of the parametrical tissues or seminal vesicles | ||
| 1.2.7 | Visually sharp reproduction of the prostata | ||
| 2. | CRITERIA FOR RADIATION DOSE TO THE PATIENT | ||
| 2.1 | CTDIW | : | routine pelvis: 35 mGy |
| 2.1 | DLP | : | routine pelvis: 570 mGy cm |
| 3. | EXAMPLES OF GOOD IMAGING TECHNIQUE | ||
| 3.1 | Patient position | : | supine with arms at chest or head level |
| 3.2 | Volume of investigation | : | from iliac crest to pelvic floor |
| 3.3 | Nominal slice thickness | : | 7-10 mm; 4-5 mm if small lesions are suspected, serial or preferably helical CT |
| 3.4 | Inter-slice distance/pitch | : | contiguous or a pitch = 1.0; 4-5 mm or a pitch up to 1.2-1.5 may be used in screening examinations |
| 3.5 | FOV | : | adjusted to the maximum diameter of the pelvis |
| 3.6 | Gantry tilt | : | none |
| 3.7 | X-ray tube voltage (kV) | : | standard |
| 3.8 | Tube current and exposure time product (mAs) | : | should be as low as consistent with required image quality |
| 3.9 | Reconstruction algorithm | : | soft tissue/standard or high resolution if bone evaluation is required |
| 3.10 | Window width | : | 200 - 600 HU (soft tissues) 2000 - 3000 HU (bones) |
| 3.11 | Window level | : | 30 - 60 HU (enhanced examination) 0 - 30 HU (unenhanced examination) 400 - 600 HU (bones) |
| 3.12 | Protective Shielding | : | lead-purse for the male gonads |
| 4. | CLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE | ||
| 4.1 | Motion | - | movement artefact deteriorates the image quality |
| 4.2 | Intravenous contrast media | - | useful for delineation of neoplastic or inflammatory diseases and distinguishing lesions from vessels |
| 4.3 | Problems and pitfalls | - | delineation of organs and structures may be difficult in cachectic patients with reduced intra-abdominal and retroperitoneal fatty tissue |
| - | folds of the bowel wall or stool may mimic tumour | ||
| - | empty urinary bladder | ||
| - | contrast media "jets" from the ureters into the urinary bladder | ||
| 4.4 | Modification to technique | - | additional thinner slices to delineate small alterations |
| - | additional enteral contrast media may be needed to visualise the bowel | ||
| - | additional i.v. contrast media with regard to the urinary bladder | ||
| - | filling of the urinary bladder by oral water intake | ||