PANCREAS
| Preparatory steps: | |||
| - | Indications: suspected or known focal or diffuse disease of the pancreas or peripancreatic structures | ||
| - | Advisable preliminary investigations: ultrasonography; laboratory investigations (amylase, lipase). MRI may be an alternative examination without exposure to inonising radiation | ||
| - | Patient 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 | ||
| - | Scan projection radiograph: frontal from lower chest to middle abdomen | ||
| 1. | DIAGNOSTIC REQUIREMENTS | ||
| Image criteria: | |||
| 1.1 | Visualization of | ||
| 1.1.1 | Entire pancreas (head, body, tail, uncinate process) | ||
| 1.1.2 | Entire diseased peripancreatic tissue | ||
| 1.1.3 | Adjacent parts of liver, spleen, bowels and stomach | ||
| 1.1.4 | Vessels after intravenous contrast media | ||
| 1.2 | Critical reproduction | ||
| 1.2.1 | Visually sharp reproduction of the pancreatic contours | ||
| 1.2.2 | Visually sharp reproduction of the pancreatic parenchyma | ||
| 1.2.3 | Reproduction of the pancreatic duct | ||
| 1.2.4 | Visually sharp reproduction of the common bile duct within the pancreatic head | ||
| 1.2.5 | Visually sharp reproduction of the mesenteric artery and vein | ||
| 1.2.6 | Visually sharp reproduction of the splenic artery and vein | ||
| 1.2.7 | Visually sharp reproduction of the portal vein | ||
| 1.2.8 | Visually sharp reproduction of the coeliac trunk | ||
| 1.2.9 | Visually sharp reproduction of diaphragmatic crura | ||
| 1.2.10 | Visually sharp reproduction of the aorta | ||
| 1.2.11 | Visually sharp reproduction of the vena cava | ||
| 1.2.12 | Visually sharp reproduction of the renal vessels | ||
| 1.2.13 | Visually sharp reproduction of the duodenum | ||
| 2. | CRITERIA FOR RADIATION DOSE TO THE PATIENT | ||
| 2.1 | CTDIW | : | no specific value as yet available (for information: routine abdomen: 35 mGy) |
| 2.1 | DLP | : | no specific value as yet available (for information: routine abdomen: 800 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 | : | 1-2 cm above the pancreatic tail to 1-2 cm below the uncinate process; larger volume may be needed to include all peripancreatic lesions such as pseudocysts or exudates |
| 3.3 | Nominal slice thickness | : | 3-5 mm; 7-10 mm in known larger lesions, serial or preferably helical |
| 3.4 | Inter-slice distance/pitch | : | contiguous or a pitch = 1.0; 5-10 mm or a pitch up to 1.2-2.0 for exudates caudal to the pancreas |
| 3.5 | FOV | : | 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 |
| 3.6 | 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 |
| 3.10 | Window width | : | 150 - 400 HU |
| 3.11 | Window level | : | 30 - 50 HU (enhanced examination) 0 - 30 HU (unenhanced examination) |
| 4. | CLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE | ||
| 4.1 | Motion | - | movement artefact deteriorates the image quality. This is prevented by a standard breath-hold technique; alternatively if this is not possible scan during quiet respiration |
| 4.2 | Intravenous contrast media | - | useful for delineation of tumorous or inflammatory disease |
| - | scanning early after injection of intravenous contrast media is useful for detection of intrapancreatic tumours | ||
| 4.3 | Problems and pitfalls | - | inconsistent breath holding between slices may obscure subtle pathology in serial CT |
| - | insufficient differentiation of pancreatic head and duodenum due to lack of oral contrast media in duodenum | ||
| - | insufficient pancreatic delineation in patients with reduced retroperitoneal fatty tissue | ||
| 4.4 | Modification to technique | - | bowel motion may require spasmolytic therapy |
| - | the examination may be extended to include the liver with contrast in the portovenous phase in the case of tumour suspicion | ||
| - | intra-arterial contrast media may be used for detection of endocrine pancreatic tumours | ||