Table 6.
CT-scan protocol. Suggested scan parameters and general guidelines are given
| CT scan protocol—parameters | ||
| Feature | Value | Additional comments |
| Coverage | Aortic arch to Circle of Willis | Always evaluate degree of atherosclerosis and morphology of the aortic arch and potential variants of the circle of Willis |
| Scan mode | Helical (may vary on scanner type) | Protocol must be adjusted according to manufacturer guidelines (singe vs dual-source systems) |
| Scan direction | Caudo-cranial | Not commonly used, small anatomic coverage, to be considered when intravenous contrast is contraindicated |
| Start of acquisition | Bolus tracking on the aortic arch | Local experiences may vary |
| Collimation | 0.6 × 64 (or better) | Depends on the scanner detector configuration |
| Pitch | Depending on the scanner type, typically < 1 | |
| kV | 120 | 100 kV is not recommended for examinations, as kV influences plaque attenuation values. |
| mA | 350 | Anatomy-based modulation may be used |
| FOV | 200 mm, centered on cervical arteries | A well-centered FOV may improve resolution and lower dose |
| Filter | Medium to sharp | Local experience may vary; Visual effect of filter may be influenced by chosen iterative reconstruction techniques and other noise-reductions algorithms |
| Slice thickness | < = 1 mm for secondary raw data set, 3 mm for reading data set | Secondary raw data set is used for detail reviewing and post-processing |
| Reconstruction interval | 50 % of chosen slice thickness for the secondary raw data set | No overlap is necessary for the reading of 3 mm datasets |
| CT-scan protocol—general guidelines | ||
| Patient preparation | Check for usual CT-related contra-indications | |
| IV access | Antecubital vein (right arm preferred) | |
| Gadolinium-contrast concentration | > = 300 mg iodine/mL | |
| Contrast volume | 30–50 mL depending on body weight | |
| Injection rate / saline flush | > = 4 mL/s; 50 cc saline flush | |
| Evaluation of neovascularization | A non-enhanced scan is necessary, identical scan parameters | |
| Post-processing | Review of axial unprocessed images | |
| Curved-MPR images along a complete trajectory | ||
| VR-images for complex/tortuous anatomy | ||
| Reporting | Structured reporting recommended | |