Table 7.
MR-scan protocol. Suggested scan parameters and general guidelines
| MR scan protocol—parameters | |||||
| Anatomical target | Sequence* | Scan range | IV contrast | Signal characteristics | Additional comments |
| Lumen / ulceration visualization | 3D GRE T1WI | Aortic arch to Circle of Willis | Yes | T1-shortening of contrast agents enhances arteries against darker background | Most common method for CE-MRA. Commonly pre- and post-contrast acquisitions are performed |
| Time-resolved 3D GRE T1WI | Aortic arch to Circle of Willis | Yes | Same principle, but multiple short acquisitions provide dynamic flow information | May be used when patient cooperation is limited, incorporates non-contrast acquisition within same acquisition | |
| 3D TOF | Carotid bifurcation | No | High signal of moving voxels in selected volume | Not commonly used, small anatomic coverage, to be considered when intravenous contrast is contraindicated | |
| Intraplaque hemorrhage (IPH) | IR-TFE/SPGR (MP-RAGE) | Carotid bifurcation | No | High signal of blood degradation products within plaque | Most important detectable vulnerable plaque component. Presence is associated with increased future risk for ipsilateral stroke |
| Lipid-rich necrotic core (LRNC) | TSE/FSE T2WI | Carotid bifurcation | No | Hypointense on T2WI | May be used with intravenous contrast is contra-indicated |
| Non-enhanced and CE-T1WI | Carotid bifurcation | Yes | Hyperintense on T1WI | LRNC does not enhance on CE-T1WI sequences | |
| Fibrous cap (FC) | 3D TOF | Carotid bifurcation | No | Hypointense with varying thickness | An intact FC has a smooth and regular surface |
| CE-T1WI | Carotid bifurcation | Yes | Intact FC: enhancing and smooth band against dark lumen; thinned FC: smooth but not-enhancing band; ruptured FC: irregular surface non-enhancing band | Intact FC: enhancing and smooth band against dark lumen; thinned FC: smooth but not-enhancing band; ruptured FC: irregular surface non-enhancing band | |
| MR scan protocol—general guidelines | |||||
| Field strength | At least 1.5T, preferably 3T systems | ||||
| Coils | If available, dedicated carotid coils must be used | ||||
| Patient preparation | Check for usual MR-related contra-indications | ||||
| IV access | Antecubital vein (right arm preferred) | ||||
| Gadolinium-contrast concentration | > = 0.5 mol/L Gadolinium concentration. High relaxivity agents are preferred. | ||||
| Contrast volume | 6–15 mL depending on body weight | ||||
| Injection rate / saline flush | 2 mL/s; 50 cc saline flush | ||||
| 2D vs 3D sequences | 3D sequences are recommended, but local expertise may vary | ||||
| CE-MRA Post-processing |
Review of raw non-subtracted contrast-enhanced images MIP images processed on work station VR-images for complex/tortuous anatomy |
||||
| Reporting | Structured reporting recommended | ||||
*GRE, gradient echo; TOF, time of flight; IR-TFE, inversion recovery turbo field echo; SPGR, spoiled gradient recalled; TSE, turbo spin echo; SE, spin echo; CE, contrast-enhanced