Virtual intra-arterial angioscopy (VIA) of the carotid artery based on helical CT data

The purpose of this study was to visualize both the vessel wall and atherosclerotic plaques in virtual intra-arterial angioscopy (VIA) based on helical CT data sets. To achieve this in vitro, the optimal reconstruction threshold of the vessel wall was determined to be 56.4% of the maximum enhancement. Using this threshold, 20 patients suffering from symptomatic carotid disease were examined in a helical CT scanner. The degree of stenosis was defined using the North American Symptomatic Endarterectomy Trial (NASCET) criteria and compared with results from digital substraction angiography (DSA). Grading of stenoses was only possible by adding the separately computed plaque geometry to the geometry of the vessel wall in a second step. Correlation between VIA and DSA in low grade, medium grade and high grade stenosis was 88%, 93% and 71%, respectively. Complete occlusions were diagnosed correctly in all patients. Sensitivity and specificity for the correct diagnosis of high grade stenosis was 93.7% and 91.3%, respectively. A realistic depiction of intraluminal structures in carotid arteries can only be generated by displaying both the vessel wall and plaque structures simultaneously.