Digital subtraction angiography was unable to visualize nearly 10% of 1127 arterial segments analyzed by researchers in the U.K. Because four-slice CT angiography picked up all those missed stenoses, DSA should not be considered the gold standard in this patient population, they said.
"When we're doing technology assessment, comparing a new modality with a gold standard, DSA does not fulfill that criterion. It consistently fails to opacify distal vessels and has a large degree of interobserver variation," Dr. Andrew J. Edwards said at a Monday afternoon scientific session.
But neither is CTA perfect. Overall agreement by two observers for CTA was around 87%, and the specificity for diagnosing normal or nontreatable segments was in the low 90%. However, the sensitivity for diagnosing significantly stenosed or occluded segments with CTA was 79.1% and 72% for each observer.
"At his very worst, observer 2 failed to identify just over 50% of potentially treatable iliac lesions," Edwards said.
Edwards and colleagues from Derriford Hospital in Plymouth prospectively evaluated 44 patients referred for lower limb arteriography who underwent prior CTA with a four-slice scanner. Over 1000 arterial segments were analyzed by both DSA and CTA.
The group evaluated images with volume-rendered technology, in which an angiographic-type image that could be freely rotated and the window settings adjusted. Researchers also relied on reviewing the axial data in tandem with the volume-rendered data.
The group does not recommend CTA for assessing lower limb arterial disease. Neither does it recommend using volume-rendered images without access to MIP or MPR images.
The moderator asked what radiologists can do to avoid complications associated with a case that Edwards demonstrated. In that case, both axial and volume-rendered imaging missed a common iliac stenosis.
Edwards replied that some postprocessing programs now allow the radiologist to travel down the artery, particularly cross-sectionally in the iliacs.
"If we had that available, we might have picked up that stenosis. The bottom line, though, is to use narrower collimation. I don't think 3.2 mm is up to it for these short stenoses," Edwards said.
