ORIGINAL RESEARCH INTERVENTIONAL VascularWall Imaging of Unruptured Cerebral Aneurysms with a Hybrid of Opposite-Contrast MR Angiography

BACKGROUND AND PURPOSE: Inflammation and degeneration of the intracranial saccular aneurysm wall play a major role in aneurysm formation, development and subsequent rupture. The aim of this studywas to characterize thewalls of unruptured intracranial aneurysms by using a hybrid of opposite-contrast MRA at 3T. MATERIALS AND METHODS: Fourteen consecutive patients with 17 unruptured intracranial aneurysms who initially underwent clipping surgery were prospectively evaluated. All aneurysms were scanned preoperatively by using a hybrid of opposite-contrast MRA in 3T high-resolutionMR imaging.We classified intraoperative findings of atherosclerotic plaques in the aneurysms into 3 grades: grade A (major plaques), grade B (minor plaques), and grade C (no plaques). The contrast ratio of the high-intensity area was also measured relative to the background low-intensity area inside the carotid artery. RESULTS: Findings from preoperative plaque imaging of the aneurysm corresponded to the intraoperative findings in 15 of 16 aneurysms (excluding 1 that was impossible to visualize in its entirety due to anatomic reasons). Overall sensitivity and specificity of the hybrid of opposite-contrast MRAwere 88.9 % and 100%, respectively. During the operation, 4 aneurysms were classified as grade A; 5, as grade B; and 7, as grade C. The means of the contrast ratio for grades A, B, and C were 0.72 0.03, 0.34 0.30, and0.02 0.09, respectively. CONCLUSIONS: The hybrid of opposite-contrast MRA can detect visible atherosclerotic plaques in the unruptured aneurysm wall, and the contrast ratio in intracranial aneurysms correlatedwith their presence and extent. A study including a larger series is needed to validat