Passive tracking of catheters and guidewires by contrast-enhanced MR fluoroscopy.

Passive MR tracking of catheters and guidewires is usually done by dynamically imaging a single thick slab, subtracting a baseline image, and combining the result with a previously acquired MR angiogram. In the in vitro and in vivo experiments reported here, it is demonstrated that this approach may be greatly simplified by using a suitable intravascular contrast agent. The proposed method, contrast-enhanced MR fluoroscopy, combines tracking and angiography into a single sequence and allows direct visualization of the magnetically prepared parts of catheters and guidewires with respect to the vasculature at a frame rate of about one image per 1.5 seconds. Contrast-enhanced MR fluoroscopy, although still limited in temporal resolution, thus obviates the need for subtraction and overlay techniques and eliminates the sensitivity of tracking to subject motion between acquisitions. Magn Reson Med 45:17-23, 2001.