LUMBAR SPINE, DISCAL HERNIATION
| Preparatory steps: | |||
| - | Indications: radiculopathy (sciatica), back pain, failure of conservative treatment and postoperative back pain, especially when MRI is contra-indicated | ||
| - | Advisable preliminary investigations: radiography of the spine; electromyography; MRI is a preferable alternative examination without exposure to ionising radiation | ||
| - | 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: lateral of the suspected diseased disks | ||
| 1. | DIAGNOSTIC REQUIREMENTS | ||
| Image criteria: | |||
| 1.1 | Visualization of | ||
| 1.1.1 | The entire region of suspected pathology | ||
| 1.1.2 | Vessels after intravenous contrast media | ||
| 1.1.3 | Spinal cord and nerve roots after intrathecal injection of contrast media (CT-myelography) | ||
| 1.2 | Critical reproduction | ||
| 1.2.1 | Visually sharp reproduction of the intervertebral disk profiles | ||
| 1.2.2 | Visually sharp reproduction of the thecal sac | ||
| 1.2.3 | Visually sharp reproduction of the perithecal fat | ||
| 1.2.4 | Visually sharp reproduction of the intervertebral radicular canals | ||
| 1.2.5 | Visually sharp reproduction of the nerve roots | ||
| 1.2.6 | Reproduction of the main vessels and perithecal venous plexuses after intravenous contrast media | ||
| 1.2.7 | Reproduction of the cortical and trabecular bone | ||
| 1.2.8 | Visually sharp reproduction of the intervertebral joints | ||
| 1.2.9 | Reproduction of the paravertebral ligaments | ||
| 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, legs in flexion |
| 3.2 | Volume of investigation | : | from pedicle to pedicle with targeting of a slice at the centre of the suspected diseased disks |
| 3.3 | Nominal slice thickness | : | 2-5 mm |
| 3.4 | Inter-slice distance/pitch | : | contiguous or a pitch = 1.0 |
| 3.5 | FOV | : | spine dimension |
| 3.6 | Gantry tilt | : | as parallel as possible to the intervertebral disc planes; a different gantry tilt may be required for each intervertebral space |
| 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 | : | 140-400 HU (soft tissue) 2000-3000 HU (bones) 250-300 HU (lumbar spine) |
| 3.11 | Window level | : | 30-40 HU (soft tissue) 200-400 HU (bones) 25-35 HU (lumbar spine) |
| 3.12 | Protective Shielding | : | lead-purse for the male gonads if the edge of the volume of investigation is less than 10-15 cm away |
| 4. | CLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE | ||
| 4.1 | Motion | - | movement artefact deteriorates image quality (prevented by sedation of non-cooperative patients) |
| 4.2 | Intravenous contrast media | - | useful to identify vascular structures and enhancing lesions |
| 4.3 | Problems and pitfalls | - | foreign bodies (beam hardening artefacts) |
| - | calcifications versus contrast enhancement | ||
| 4.4 | Modification to technique | - | intrathecal injection of contrast medium (CT-myelography) to delineate the spinal cord and nerve roots |