ADRENAL GLANDS
Preparatory steps: | |||
- | Indications: suspected or known focal or diffuse structural disease of the adrenal glands | ||
- | Advisable preliminary investigations: ultrasonography; scintigraphy; laboratory investigations. 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 lower chest to middle abdomen | ||
1. | DIAGNOSTIC REQUIREMENTS | ||
Image criteria: | |||
1.1 | Visualization of | ||
1.1.1 | Both adrenal glands | ||
1.1.2 | Upper perirenal spaces | ||
1.1.3 | Vessels after intravenous contrast media | ||
1.2 | Critical reproduction | ||
1.2.1 | Visually sharp reproduction of the right adrenal body | ||
1.2.2 | Visually sharp reproduction of the right adrenal crura | ||
1.2.3 | Visually sharp differentiation of the right adrenal gland from adjacent structures | ||
1.2.4 | Visually sharp reproduction of the left adrenal body | ||
1.2.5 | Visually sharp reproduction of the left adrenal crura | ||
1.2.6 | Visually sharp differentiation of the left adrenal gland from adjacent structures | ||
1.2.7 | Visually sharp reproduction of the diaphragmatic crura | ||
1.2.8 | Visually sharp reproduction of the aorta | ||
1.2.9 | Visually sharp reproduction of the vena cava | ||
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 to 1-2 cm below the adrenal glands |
3.3 | Nominal slice thickness | : | 2-5 mm, serial or preferably helical; can be larger if pathology is already known. |
3.4 | Inter-slice distance/pitch | : | contiguous or a pitch = 1.0; in the case of minor pathology, overlapping slices by serial CT |
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 to improve delineation of the adrenals from adjacent organs or structures, and for characterization of tumours |
4.3 | Problems and pitfalls | - | inconsistent breath holding between slices may obscure subtle pathology in serial CT |
- | insufficient adrenal delineation in patients with reduced retroperitoneal fatty tissue | ||
4.4 | Modification to technique | - | administration of oral contrast media to improved delineation from adjacent organs or structures |