Complementary Roles of Dynamic Contrast-Enhanced MR Imaging and Postcontrast Vessel Wall Imaging in Detecting High-Risk Intracranial Aneurysms

BACKGROUND AND PURPOSE: Individual assessment of the absolute risk of intracranial aneurysm rupture remains challenging. Emerging imaging techniques such as dynamic contrast-enhanced MR imaging and postcontrast vessel wall MR imaging may improve risk estimation by providing new information on aneurysm wall properties. The purpose of this study was to investigate the relationship between aneurysm wall permeability on dynamic contrast-enhanced MR imaging and aneurysm wall enhancement on postcontrast vessel wall MR imaging in unruptured intracranial aneurysms. MATERIALS AND METHODS: Patients with unruptured saccular intracranial aneurysms were imaged with vessel wall MR imaging before and after gadolinium contrast administration. Dynamic contrast-enhanced MR imaging was performed coincident with contrast injection using 3D T1-weighted spoiled gradient-echo imaging. The transfer constant (K-trans) was measured adjacent to intracranial aneurysm and adjacent to the normal intracranial artery. RESULTS: Twenty-nine subjects were analyzed (mean age, 53.9 +/- 13.5 years; 24% men; PHASES score: median, 8; interquartile range, 4.75-10). K-trans was higher in intracranial aneurysms compared with the normal intracranial artery (median, 0.0110; interquartile range, 0.0060-0.0390 versus median, 0.0032; interquartile range, 0.0018-0.0048 min(-1); P < .001), which correlated with intracranial aneurysm size (Spearman rho = 0.54, P = .002) and PHASES score (rho = 0.40, P = .30). Aneurysm wall enhancement, detected in 19 (66%) aneurysms, was associated with intracranial aneurysm size and the PHASES score but not significantly with K-trans (P = .30). Aneurysms of 2 of the 9 patients undergoing conservative treatment ruptured during 1-year follow-up. Both ruptured aneurysms had increased K-trans, whereas only 1 had aneurysm wall enhancement at baseline. CONCLUSIONS: Dynamic contrast-enhanced MR imaging showed increased K-trans adjacent to intracranial aneurysms, which was independent of aneurysm wall enhancement on postcontrast vessel wall MR imaging. Increased aneurysm wall permeability on dynamic contrast-enhanced MR imaging provides new information that may be useful in intracranial aneurysm risk assessment.