Principles of contrast-enhanced MR angiography. Basic and clinical applications

Contrast-enhanced MR angiography has several advantages in the clinical setting. One advantage is the shortening of T1 because the source of signal increase is resistant to signal losses caused by blood saturation, especially for in-plane flow as encountered in TOF MR angiography and PC MR angiography. This T1 reduction is clearly advantageous in obtaining images of tortuous vessels and stenotic regions. Because the contrast agent Gd-DTPA is well-tolerated and has no nephrotoxic effect, its use in patients with impaired renal function is widely accepted. It is also reported in the literature that the depiction of large aneurysms is markedly more simple with CE-MR angiography than with digital subtraction angiography because filling and subsequent washout of contrast material can be followed over a longer period of time. The main intrinsic advantage of CE-MR angiography compared with TOF and PC-MR angiography is its acquisition speed (because of ultra-short TRs) with comparable gradient performance. Also, the slice orientation can be chosen as the clinical situation dictates and needs rather than being uniformly perpendicular to blood flow, as was often necessary previously. The author considers CE-MR angiography a valuable development for vascular MR imaging. It is currently being compared with alternative methods in studies at several centers.