CHEST, GENERAL
| Preparatory steps: | |||
| - | Indications: suspected or known pulmonary, pleural or lymph node disease, including metastatic neoplasms, infection, traumatic lesions and focal diseases | ||
| - | Advisable preliminary investigations: chest radiography | ||
| - | 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 neck to upper abdomen | ||
| 1. | DIAGNOSTIC REQUIREMENTS | ||
| Image criteria: | |||
| 1.1 | Visualization of | ||
| 1.1.1 | Entire thoracic wall | ||
| 1.1.2 | Entire thoracic aorta and vena cava | ||
| 1.1.3 | Entire heart | ||
| 1.1.4 | Entire lung parenchyma | ||
| 1.1.5 | Vessels after intravenous contrast media | ||
| 1.2 | Critical reproduction | ||
| 1.2.1 | Visually sharp reproduction of the thoracic aorta | ||
| 1.2.2 | Visually sharp reproduction of the anterior mediastinal structures, including thymic residue (if present) | ||
| 1.2.3 | Visually sharp reproduction of the trachea and main bronchi | ||
| 1.2.4 | Visually sharp reproduction of the paratracheal tissue | ||
| 1.2.5 | Visually sharp reproduction of the carina and lymph node area | ||
| 1.2.6 | Visually sharp reproduction of the oesophagus | ||
| 1.2.7 | Visually sharp reproduction of the pleuromediastinal border | ||
| 1.2.8 | Visually sharp reproduction of large and medium sized pulmonary vessels | ||
| 1.2.9 | Visually sharp reproduction of segmental bronchi | ||
| 1.2.10 | Visually sharp reproduction of the lung parenchyma | ||
| 1.2.11 | Visually sharp reproduction of the border between the pleura and the thoracic wall | ||
| 2. | CRITERIA FOR RADIATION DOSE TO THE PATIENT | ||
| 2.1 | CTDIW | : | routine chest: 30 mGy |
| 2.1 | DLP | : | routine chest: 650 mGy cm |
| 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 |
| 3.3 | Nominal slice thickness | : | 7-10 mm serial or preferably helical |
| 3.4 | Inter-slice distance/pitch | : | contiguous or a pitch = 1.0; 4-5 mm or pitch up to 1.5 may be used for large lesions or detection of lymphadenopathy alone; even larger inter-slice distance/pitch may be applied in critically ill patients |
| 3.5 | FOV | : | adjusted to largest thoracic diameter within the volume of investigation |
| 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 | : | 300-600 HU (soft tissue) 800-1.600 HU (lung parenchyma) |
| 3.11 | Window level | : | 0-30 HU (soft tissue, unenhanced examination) 30-60 HU (soft tissue, enhanced examination) -500 - -700 HU (lung parenchyma) |
| 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 | - | may be used to characterise lesions or to distinguish them from vessels |
| 4.3 | Problems and pitfalls | - | anatomical misregistration due to variation in the phase of respiration |
| - | focal atelectasis may obscure pathology | ||
| - | motion artefact due to cardiac pulsation or respiration | ||
| 4.4 | Modification to technique | - | prone position may be used to elucidate pleural lesions or focal spaces |
| - | the examination may be confined to a specific area of interest | ||
| - | 4 mm slices may be used for specific examination of hilar pathology and subtle pulmonary lesions | ||