Abstract 2766: Hemodynamic Changes Following Direct EC-IC Bypass In Moyamoya Disease Patients Measured Using Combined Arterial Spin Labeling And Dynamic Susceptibility Contrast MR Imaging

Abstract

Background: The goal of direct bypass in Moyamoya patients is to reduce the risk of future strokes, presumably by improving cerebral hemodynamics. Combined ASL and DSC MR perfusion imaging (CAD-perfusion) is a new quantitative methodology to measure perfusion parameters ( 1 ). Methods: We applied this method to 20 newly-diagnosed, symptomatic Moyamoya patients (11 bilateral, 9 unilateral). Imaging was acquired at 3T (GE MR 750, Waukesha, WI) before and approximately 6 months following direct STA-MCA anastomosis. ASL was performed using 3D fast-spin-echo background-suppressed pseudocontinuous ASL with the following parameters (TR/TE/label time/post-label delay 5500/2.5/1500/2000 ms; spatial resolution 3 × 3 × 4 mm; imaging time 4:37). DSC was performed using gradient-echo EPI with the following parameters (TR/TE 1800/40 ms; 1.9 × 1.9 × 5 mm; 0.1 mmol/kg Multihance contrast). Images were co-registered, placed into template space, and resliced to 10 mm axial slice thickness corresponding to the ASPECTS slices using SPM8. CAD-perfusion images (CAD-CBF and CAD-CBV) were created using standard methods ( 1 ). Analysis was by hemisphere (n=20 posterior, n=31 bypassed anterior, and n=9 non-bypassed anterior regions). Hemodynamic measurements were made in mixed cortical ROI’s. The Wilcoxon rank-sum test was used to assess significance at the p<0.05 level. Results: 6 months following bypass, Tmax in the bypassed anterior circulation decreased significantly (from 3.6±1.2 to 3.0±0.9 sec, p=0.019) but did not change in either the non-bypassed anterior circulation or posterior circulation. CAD-CBF did not increase in any of the three regions; in particular, no increase was seen in the anterior bypassed regions (from 34.8±8.5 to 36.8±8.1 ml/100 g/min, p>0.05). This is consistent with prior reports suggesting that baseline CBF does not change following bypass ( 2 ). Interestingly, CAD-CBV was significantly increased in all regions following bypass; this change was largest in the non-bypassed anterior circulation (from 4.5±1.0 to 6.1±2.3%, p=0.035). Conclusion: Hemodynamic changes following bypass are complex and involve both hemispheres. CAD-perfusion MRI allows the ability to follow these parameters in a quantitative way.