CHEST, HRCT (HIGH RESOLUTION CT)
| Preparatory steps: | |||
| - | Indications: detection and characterization of diffuse parenchymal lung disease including emphysema or bronchiectasis | ||
| - | Advisable preliminary investigations: chest radiography and respiratory function tests | ||
| - | Patient preparation: information about the procedure | ||
| - | Scan projection radiograph: frontal from neck to upper abdomen | ||
| 1. | DIAGNOSTIC REQUIREMENTS | ||
| Image criteria: | |||
| 1.1 | Visualization of | ||
| 1.1.1 | Entire field of lung parenchyma | ||
| 1.2 | Critical reproduction | ||
| 1.2.1 | Visually sharp reproduction of the lung parenchyma | ||
| 1.2.2 | Visually sharp reproduction of pulmonary fissures | ||
| 1.2.3 | Visually sharp reproduction of secondary pulmonary lobular structures such as interlobular arteries | ||
| 1.2.4 | Visually sharp reproduction of large and medium sized pulmonary vessels | ||
| 1.2.5 | Visually sharp reproduction of small pulmonary vessels | ||
| 1.2.6 | Visually sharp reproduction of large and medium sized bronchi | ||
| 1.2.7 | Visually sharp reproduction of small bronchi | ||
| 1.2.8 | Visually sharp reproduction of the pleuromediastinal border | ||
| 1.2.9 | Visually sharp reproduction of the border between the pleura and the thoracic wall | ||
| 2. | CRITERIA FOR RADIATION DOSE TO THE PATIENT | ||
| 2.1 | CTDIW | : | 35 mGy (pilot study (17)) |
| 2.1 | DLP | : | 280 mGy cm (pilot study) |
| 3. | EXAMPLES OF GOOD IMAGING TECHNIQUE | ||
| 3.1 | Patient position | : | supine, arms above the head |
| 3.2 | Volume of investigation | : | from lung apex to the base of the lungs (survey) or corresponding to radiographically defined abnormality (localised disease) |
| 3.3 | Nominal slice thickness | : | 1-2 mm |
| 3.4 | Inter-slice distance/pitch | : | 10-20 mm |
| 3.5 | FOV | : | adjusted to the minimum which will demonstrate the whole lung field |
| 3.6 | Gantry tilt | : | none |
| 3.7 | X-ray tube voltage (kV) | : | high kV or standard |
| 3.8 | Tube current and exposure time product (mAs) | : | should be as low as consistent with required image quality |
| 3.9 | Reconstruction algorithm | : | high resolution |
| 3.10 | Window width | : | 1000-1600 HU |
| 3.11 | Window level | : | -400 - -700 HU |
| 4. | CLINICAL CONDITIONS WITH IMPACT ON GOOD IMAGING PERFORMANCE | ||
| 4.1 | Motion | - | movement artefact deteriorates the image quality and breath-hold technique is mandatory |
| 4.2 | Intravenous contrast media | - | not required |
| 4.3 | Problems and pitfalls | - | motion artefact due to dyspnoea |
| - | atelectasis may obscure pathology | ||
| 4.4 | Modification to technique | - | prone position may be used to elucidate dependent changes, especially small areas of atelectasis |
| - | examination in suspended expiration to detect air trapping | ||
| - | sections with smaller inter-slice distance for evaluation of very small areas of disease | ||
| - | sections with a cranio-caudal -25 to -30° gantry tilt for detection of bronchiectasies | ||