Simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) imaging: Comparison with contrast‐enhanced MR angiography for measuring carotid stenosis

Purpose To evaluate in a proof-of-concept study the feasibility of Simultaneous Noncontrast Angiography and intraPlaque hemorrhage (SNAP) imaging as a clinical magnetic resonance angiography (MRA) technique for measuring carotid stenosis. There is a growing interest in detecting intraplaque hemorrhage (IPH) during the clinical management of carotid disease, yet luminal stenosis has remained indispensable during clinical decision-making. SNAP imaging has been proposed as a novel IPH imaging technique that provides carotid MRA with no added scan time. Flowing blood shows negative signal on SNAP because of phase-sensitive inversion recovery. Materials and Methods In all, 58 asymptomatic subjects with 16–79% stenosis on ultrasound were scanned at 3T by SNAP with 0.8 mm isotropic resolution and 16 cm longitudinal coverage. Two readers measured luminal stenosis of bilateral carotid arteries (n = 116) on minimum intensity projections of SNAP using the NASCET criteria. In the subset (48 arteries) with contrast-enhanced (CE) MRA available for comparison, luminal stenosis was also measured on maximum intensity projections of CE-MRA. Results Intraclass correlation coefficients (ICCs) with 95% confidence intervals were 0.94 (0.90–0.96) and 0.93 (0.88–0.96) for intra- and interreader agreement on stenosis measurements, respectively. Corresponding kappas for grading stenosis (0–29%, 30–69%, 70–99%, and 100%) were 0.79 (0.67–0.89) and 0.80 (0.68–0.90). Agreement between SNAP and CE-MRA was high (ICC: 0.95 [0.90–0.98]; kappa: 0.82 [0.71–0.93]). Conclusion As a dedicated IPH-imaging sequence, SNAP also provided carotid stenosis measurement that showed high intra- and interreader consistency and excellent agreement with CE-MRA. Further comparisons with digital subtraction angiography and other noninvasive techniques are warranted. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1045–1052.