Subtracted CTA offers alternative to 3D DSA for ID’ing aneurysms

Subtracted 320-detector row volumetric CT angiography (CTA), which allows bone-free visualization, is superior to nonsubtracted volumetric CTA for the detection of cerebral aneurysms and should be considered as the first-line imaging technique for evaluating suspected aneurysms, according to a study published online in Radiology.

The study found subtracted CTA was comparable to 3D rotational digital subtraction angiography (DSA), which is currently considered the gold standard despite its invasiveness, complexity and relatively high costs, explained Wenhua Chen, MD, of the Third Affiliated Hospital of Suzhou University, Changzhou, China.

“Subtracted volumetric CT angiography could replace invasive digital subtraction angiography as the first-line imaging technique for noninvasive evaluation of suspected cerebral aneurysms because of its high diagnostic sensitivity,” they wrote.

Findings were based on evaluation of 282 consecutive patients who underwent CTA for a suspected cerebral aneurysm between February 2011 and October 2012. All patients also received 3D rotational DSA, which was used as the reference standard.

A total of 239 cerebral aneurysms were detected in 198 patients on the basis of 3D DSA. While nonsubtracted CTA was able to show more than 96 percent of the aneurysms, it missed those that were close to bone tissue.

“The aneurysms missed at nonsubtracted volumetric CT angiography were generally located in the internal carotid artery,” wrote Chen and colleagues. “Detection of cerebral aneurysms adjacent to bone tissue was still challenging at nonsubtracted volumetric CT angiography because of the presence of overlying bone structures.”

Subtracted CTA showed 99.2 percent of aneurysms, and its accuracy was not significantly different from 3D DSA.

Subtracted CTA was not without its own limitations, however. Chen and colleagues noted that the technique has a difficult time identifying microaneurysms, missing two in this trial. Subtracted CTA also cannot display atherosclerotic plaque or aneurysmal calcification. And while eliminating bone tissue from images helps in the diagnosis of cerebral aneurysms, knowing the relationship of the aneurysm to bone structures is important for therapy.

“[S]ubtracted 320–detector row volumetric CT angiography is excellent for the detection of cerebral aneurysms and might be considered as a first-line imaging technique for the noninvasive evaluation of cerebral aneurysms because of its high diagnostic accuracy in some circumstances; however, it may still result in some missed microaneurysms,” summed the authors.