This study was conducted to identify the structures that can mimic aneurysm on CT angiography with using the 3-D volume rendering technique and a 16-row detector CT.

This study examined 206 patients who underwent CT angiography with a 16-row detector CT from May 2003 to July 2004. For the CT angiography, the contrast media was injected at a rate of 4 cc per second. The scanning was then done when 5 seconds delay time had elapsed after the CT number of the common carotid artery had reached 150. The baseline images were obtained by reconstructing the row data with a kernel value of H31f, a slice thickness of 1 mm and an increment of 0.5 mm. Finally, the 3-D images were constructed by using a volume rendering technique. The structures that were confused with aneurysm on CT angiography were further evaluated by MPR or MIP to ascertain whether they were aneurysms. For comparison, digital subtraction angiography was done in 86 patients and surgery was done in 5 patients.

On CT angiography, 51 patients did not show any abnormalities, and 80 patients showed definitive aneurysms, as was ascertained by their sizes, shapes and locations, or by the aneurysm clips only. The remaining 75 patients showed 90 aneurysm mimicking structures that were 35 infundibular dilatations or preaneurysmal blebs, 24 focal dilatations of the branches of the deep middle cerebral veins, 6 focal dilatations of the sphenoparietal sinuses adjacent to the middle cerebral artery, 18 focal dilatations of the inferior sagittal sinuses adjacent to the pericallosal artery and 7 low density calcifications of the vessel walls that were adjacent to the aneurysm-prevalent arteries.

CT angiography based on volume rendering technique was able to identify the structures that were confused with aneurysm. Accordingly, careful observation is required for interpreting the reconstructing 3-D images since a wide variety of structures can be confused with aneurysm on CT angiography.