OSSEOUS PELVIS
Preparatory steps: | |||
- | Indications: evaluation or verification of pelvic ring and acetabular fractures, hip dislocation, bone tumours, degenerative, infectious, arthritic and osteonecrotic changes | ||
- | Advisable preliminary investigations: always conventional radiography; MRI or ultrasonography may be alternative examinations without exposure to ionising radiation in non- traumatic disorders | ||
- | Patient preparation: information about the procedure; restraint from food, but not fluid, is recommended, if intravenous contrast media are to be given | ||
- | Scan projection radiograph: frontal from iliac crest to ischial tuberosity | ||
1. | DIAGNOSTIC REQUIREMENTS | ||
Image criteria: | |||
1.1 | Visualization of | ||
1.1.1 | Whole pelvic ring | ||
1.1.2 | Hip(s) including the trochanter region | ||
1.1.3 | Sacroiliac joints | ||
1.1.4 | Pubic symphysis | ||
1.2 | Critical reproduction | ||
1.2.1 | Visually sharp reproduction of the pelvic bones | ||
1.2.2 | Visually sharp reproduction of the hip joint(s) | ||
1.2.3 | Visually sharp reproduction of the sacroiliac joints | ||
1.2.4 | Visually sharp reproduction of the pubic symphysis | ||
1.2.5 | Visually sharp reproduction of the pelvic musculature | ||
2. | CRITERIA FOR RADIATION DOSE TO THE PATIENT | ||
2.1 | CTDIW | : | 25 mGy (pilot study (17)) |
2.1 | DLP | : | 520 mGy cm (pilot study) |
3. | EXAMPLES OF GOOD IMAGING TECHNIQUE | ||
3.1 | Patient position | : | supine with arms at chest or head level |
3.2 | Volume of investigation | : | tumour/fracture: from 1 cm above to 1 cm below the diseased area; joint disorders: 1 cm above to 1 cm below the joint region |
3.3 | Nominal slice thickness | : | 3-5 mm in the hip region; 3-10 mm outside the hip, serial or preferably helical |
3.4 | Inter-slice distance/pitch | : | contiguous or pitch = 1.0 in the hip region, <5 mm or a pitch up to 1.2 - 1.5 outside the hip region |
3.5 | FOV | : | pelvis, hip or sacroiliac joint dimension (usually 15-40 cm) |
3.6 | Gantry tilt | : | usually none, but cranial tilting should be used for examination of the sacroiliac joints to reduce radiation to the female gonads |
3.7 | X-ray tube voltage (kV) | : | standard or high kV in large persons to avoid noise |
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 |
3.10 | Window width | : | 1000-1500 HU (joints/bones) 200-600 HU (soft tissue) |
3.11 | Window level | : | 150-200 HU (joints/bones) 30-50 HU (soft tissue) |
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 image quality and the value of reconstructions |
4.2 | Intravenous contrast media | - | useful for delineating malignant and inflammatory lesions extending into the soft tissue, and for detecting traumatic lesion of pelvic organs |
4.3 | Problems and pitfalls | - | artefact due to metallic objects such as prothesis |
4.4 | Modification to technique | - | intracavitary contrast media to delineate traumatic lesion of pelvic organs |