Whole-Brain Vessel Wall MRI: A Parameter Tune-up Solution to Improve the Scan Efficiency of Three-Dimensional Variable Flip-Angle Turbo Spin-Echo

Purpose: To propose and evaluate a parameter tune-up solution to expedite a three-dimensional (3D) variable-flip-angle turbo spin-echo (TSE) sequence for whole-brain intracranial vessel wall (IVW) imaging. Materials and Methods: Elliptical k-space sampling and prolonged echo train length (ETL), were used to expedite a 3D variable-flip-angle TSE-based sequence. To compensate for the potential loss in vessel wall signal, optimal combination of prescribed T-2 and ETL was experimentally investigated on 22 healthy volunteers at 3 Tesla. The optimized protocol (7-8 min) was then compared with a previous protocol (reference protocol, 11-12 min) in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel wall sharpness, and wall delineation quality on a 4-point scale (0: poor; 3: excellent) in 10 healthy volunteers. A pilot study of five patients was performed and lesion delineation score was used to demonstrate the diagnostic quality. Results: A protocol with ETL = 52 and prescribed T-2 = 170 ms was deemed an optimized one, which, compared with the reference protocol, provided significantly improved wall SNR (12.0 +/- 1.3 versus 10.0 +/- 1.1; P = 0.002), wall-lumen CNR (9.7 +/- 1.2 versus 8.0 +/- 0.9; P = 0.002), wall-CSF CNR (2.8 +/- 1.0 versus 1.7 +/- 1.0; P = 0.026), similar vessel wall sharpness at both inner (1.59 +/- 0.18 versus 1.58 +/- 0.14, P = 0.87) and outer (1.71 +/- 0.25 versus 1.83 +/- 0.30; P = 0.18) boundaries, and comparable vessel wall delineation score for individual segments (1.95-3; P > 0.06). In all patients, atherosclerotic plaques (10) or wall dissection (5) were identified with a delineation score of 3 or 2. Conclusion: A parameter tune-up solution can accelerate 3D variable-flip-angle TSE acquisitions, particularly allowed for expedited whole-brain IVW imaging with preserved wall delineation quality.