KIDNEYS
| Preparatory steps: | |||
| - | Indications: suspected or known focal or diffuse structural disease of the kidneys, and traumatic lesions | ||
| - | Advisable preliminary investigations: ultrasonography; blood-creatinine (especially prior to administration of contrast media). MRI may be an alternative examination without exposure to ionising radiation | ||
| - | Patient 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 | ||
| - | Scan projection radiograph: frontal from liver dome to upper pelvis | ||
| 1. | DIAGNOSTIC REQUIREMENTS | ||
| Image criteria: | |||
| 1.1 | Visualization of | ||
| 1.1.1 | Both kidneys | ||
| 1.1.2 | Proximal part of the ureters | ||
| 1.1.3 | Vessels after intravenous contrast media | ||
| 1.2 | Critical reproduction | ||
| 1.2.1 | Visually sharp reproduction of the renal parenchyma | ||
| 1.2.2 | Visually sharp reproduction of the renal pelvis and calices/ | ||
| 1.2.3 | Visually sharp reproduction of the proximal part of the ureters | ||
| 1.2.4 | Visually sharp reproduction of the perirenal spaces | ||
| 1.2.5 | Visually sharp reproduction of the aorta and vena cava | ||
| 1.2.6 | Visually sharp reproduction of the renal arteries | ||
| 1.2.7 | Visually sharp reproduction of the renal veins | ||
| 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 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 |
| 3.3 | Nominal slice thickness | : | 4-5 mm for unknown or small pathologies; 7-10 mm for follow up of larger lesions |
| 3.4 | Inter-slice distance/pitch | : | contiguous or a pitch = 1.0 |
| 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/standard |
| 3.10 | Window width | : | 200-400 HU |
| 3.11 | Window level | : | 30-150 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 | - | combination of native and contrast enhanced studies are necessary in most patients to characterise lesions or distinguish them from vessels |
| - | multiphased section examination may be indicated. An optimal injection protocol is then important | ||
| 4.3 | Problems and pitfalls | - | inconsistent breath holding between slices may obscure subtle pathology in serial CT |
| - | differentiation of small cysts from tumours may be difficult | ||
| - | non-calcified stones may not be identifiable | ||
| 4.4 | Modification to technique | - | additional thinner slices may be obtained to delineate minor alterations |