Image Analysis
Images were analyzed on an offline workstation (Philips) by 1
observer (N.D., 3 years of experience); a second observer (A.K.,
7 years of experience) analyzed a subset of images (n=10). The
observers were blinded for clinical data. On the T w VIRTA images,
1
all major arteries of the Circle of Willis and its branches were
scored for presence of vessel wall lesions (both symptomatic and
asymptomatic); the contralateral side or the vessel wall more proxi-
mal or distal to the lesion was used as reference. The MCA stenosis
that was identified as the culprit lesion by DSA was used as the
symptomatic lesion and the other lesions as asymptomatic. Next, we
assessed morphological features, by scoring thickening pattern, dis-
tribution pattern, and enhancement pattern of the lesion. The thick-
ening pattern was scored as focal or diffuse, where focal was defined
as a short region or focal point lesion and diffuse as a lesion over a
longer trajectory (eg, >0.5 cm). Next, the distribution of the lesion