Contrast-enhanced MRA

Fig. 15.1 la-d. A 62-year-old patient with symptomatic left internal carotid artery occlusion and progressive stroke. Initial DWI shows only punctuate small lesions in the deep borderzone of the left hemisphere (a), while the hypoperfused area on the time-to-peak maps affects the complete left middle cerebral artery territory and is most pronounced in the deep borderzone area (b). On day 3, the acute lesion has grown considerably larger, paralleling progression of symptoms (c). Contrast-enhanced MRA shows proximal occlusion of the left internal carotid artery (d)... 

D contrast-enhanced MRA (optional) 2D dynamic contrast-enhanced subtraction MRA (optional) TR/TE/FA 3.5/1.0/40 coronal+sagittal ... 

The differences between low molecular weight Gd-based CAs and macromolecular CAs stem mainly from their pharmacodynamic and pharmacokinetic properties, that is, what the CA does to the body, and vice versa. In addition to the observed relaxivity, the dynamic relaxivity is another parameter that is used in contrast-enhanced MRA in the presence of different types of CAs. The dynamic relaxivity describes the relaxivity results from both bound and non-bound complexes. For example, a comparison of the strongly HSA-bound MS-325 with the non-HSA-bound P792 in rabbit showed P792 to have a more constant dynamic relaxivity [114], A constant pharmacokinetics profile is also favorable for MRA analysis. 

Fig. 6.10 Normal neck MRA. MIP image of 2D TOP of the neck (a) shows artifactual signal loss at the horizontal turn of the left vertebral artery (arrow). This area has normal flow on MIP images from the contrast-enhanced MRA (ceMRA) (b). The ceMRA also has excellent depiction of the origins of the neck vessels...

Fig. 5.29. Contrast-enhanced MRA prior to UAE. Maximum intensity projection of a Tl-weighted contrast-enhanced MR angiography depicts the uterine arteries long white arrows) as well as an enlarged the right ovarian artery thick white arrow)...

Fig. 5.26. a Time-of-flight MR angiography of normal intracranial vessels, b Contrast-enhanced MRA technique with a large lield-of-view covering all vessels from the aortic arch to the circle of Willis... 

Fig.5.30a-c. Giant basilar stem aneurysm, recurrent aneurysm could have been missed on TOF-MRA, but is delineated on contrast-enhanced MRA... 

CT, MRI, and TEE yield equally reliable diagnostic values for confirming or ruling out thoracic AD (Shiga et al. 2006). However, craniocaudal extension of the dissection is most easily detected by MDCT. Acute AD (<2 weeks) is most commonly diagnosed by CTA, since it is an emergency indication. The appropriate imaging of the chronic type of dissection is by either CTA or contrast-enhanced MRA. If acute AD is suspected. 

Nevertheless, not all patients are suitable for MRl/MRA exams. Individuals with implanted metal devices (pacemakers, cerebral vascular clips, etc.) should not be considered for such imaging. Claustrophobia remains a relative contraindication. The exam may also be limited by respiratory movements, but with contrast-enhanced MRA the acquisition time has significantly decreased (approximately 20 seconds for a complete limb exam), making breath-hold image possible. 

Wang Y, Yu Y, Li D, et al. (2000) Artery and vein separation using susceptibility-dependent phase in contrast-enhanced MRA. Journal of Magnetic Resonance Imaging. 12 661-670. 

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