Optimizing MPRAGE for enhanced blood suppression and intraplaque hemorrhage detection in carotid artery imaging

This study aims to optimize the Magnetization Prepared Rapid Acquisition Gradient Echo (MPRAGE) technique to improve the accuracy of intraplaque hemorrhage (IPH) detection in carotid diseases and enhance reliability for clinical use, addressing the challenge of inconsistent blood suppression observed in commonly used clinical protocols.

Bloch equation simulations were used to evaluate the effects of inversion time and flip angle on blood suppression and tissue contrast. The optimized parameters were implemented on a clinical 3 T scanner and tested in four subjects. Quantitative measures included blood-muscle contrast and contrast-to-noise ratios (CNR) for lumen-wall and lumen-IPH. Imaging was performed in 21 patients with carotid artery disease, two MPRAGE acquisitions were performed per patient: (1) at the magnet isocenter with the standard IR pulse, and (2) at a 50-mm shifted position toward the heart with the wideband IR pulse. Qualitative image quality was evaluated independently by two neuroradiologists using a predefined 4-point scale (1 = poor, 4 = excellent) for blood suppression, vessel wall clarity, motion artifacts, and IPH visualization, in addition to quantitative SNR and CNR measurements.

The optimized MPRAGE sequence demonstrated significantly improved blood suppression, with blood-muscle contrast increasing from 0.42 ± 0.08 to 0.61 ± 0.07 (p = 0.002). Lumen-wall CNR increased from 15.2 ± 3.4 to 22.8 ± 4.1 (p = 0.01), and lumen-IPH CNR increased from 18.7 ± 5.2 to 26.3 ± 6.0 (p = 0.004). These improvements enhanced vessel wall delineation and IPH conspicuity.

Optimization of MPRAGE parameters enhances blood suppression and contrast, providing improved visualization of the carotid vessel wall and more reliable detection of IPH. This approach may increase the diagnostic accuracy of carotid plaque imaging.