MRA: Current Applications in Body Vascular Imaging

Advantages of MRA over CTA include increased signalto-noise ratio, easier 3D postprocessing, and utility in patients with renal dysfunction, such as diabetics [2,3]. In patients who require recurrent follow-up imaging, MRA is superior, given its lack of ionizing radiation. MRA is often used to image the visceral aortic branches and in many centers is the gold standard for visualizing the renal arteries. MRA has also been shown to be valuable in the preprocedural and follow-up of patients undergoing aortic EVAR. In the planning stages, CE-MRA has been shown not only to be as accurate as CTA but able to provide functional, hemodynamic information that CTA cannot. As well, common delayed complications, for example, endoleak, are more conspicuous with contrast-enhanced MRA [8]. Other applications of MRA include cerebrovascular imaging and visualization of the infrainguinal arterial system [2]. Conventional angiography has traditionally been the gold standard for imaging vascular TOS because of its high resolution, however, it is invasive, requires the use of iodinated contrast, and does not always allow the cause of the compression to be determined [13]. MRA is perfectly suited to the imaging of vascular TOS, with its high spatial resolution, noninvasiveness, and short acquisition times [14]. Use of MRA to evaluate TOS requires 2 positions, neutral and challenged, and 2 separate contrast injections, but can be dynamically interrogated by using TRICKS or TWIST techniques. TRICKS in real time is demonstrated in Video 1. Dynamic MRA avoids the potential for residual intravascular contrast contaminations and reduced signal-to-noise ratios. Two separate static MRA studies examined this potential pitfall and concluded that image quality was. rarely impaired by the increased background contrast, because they were able to achieve detailed images of both the arteries and veins in both arm positions [11,15]. MRA, with its superior softtissue imaging capabilities, has the distinct advantage of demonstrating the underlying cause of TOS, whether it is congenital bony or fibromuscular anomalies, trauma, or posture. Ultimately, TOS is a surgical and/or clinical diagnosis, and a multidisciplinary approach is paramount. It has been suggested that diagnostic utility of MRA and CTA in detecting PAD is variable, depending on the anatomic level of the disease and the degree of venous contamination [17,18]. The infrapopliteal region is poorly visualized by CTA because of the small-