Purpose: To introduce a highly accelerated T1-weighted magnetization-prepared rapid gradient echo (MP-RAGE) acquisition that uses wave-controlled aliasing in parallel imaging (wave-CAIPI) encoding to retain high image quality. Methods: Significant acceleration of the MP-RAGE sequence is demonstrated using the wave-CAIPI technique. Here, sinusoidal waveforms are used to spread aliasing in all three directions to improve the g-factor. Combined with a rapid (2 s) coil sensitivity acquisition and data-driven trajectory calibration, we propose an online integrated acquisition-reconstruction pipeline for highly efficient MP-RAGE imaging. Results: The 9-fold accelerated MP-RAGE acquisition can be performed in 71 s, with a maximum and average g-factor of g max ¼ 1.27 and g avg ¼ 1.06 at 3T. Compared with the state-ofthe-art method controlled aliasing in parallel imaging results in higher acceleration (2D-CAIPIRINHA), this is a factor of 4.6/1.4 improvement in g max /g avg . In addition, we demonstrate a 57 s acquisition at 7T with 12-fold acceleration. This acquisition has a g-factor performance of g max ¼ 1.15 and g avg ¼ 1.04. Conclusion: Wave encoding overcomes the g-factor noise amplification penalty and allows for an order of magnitude acceleration of MP-RAGE acquisitions. Magn Reson Med 79:401-406,

Background Rapid volumetric imaging protocols could better utilize limited scanner resources. Purpose To develop and validate an optimized 6‐minute high‐resolution volumetric brain MRI examination using Wave‐CAIPI encoding. Study Type Prospective. Population/Subjects Ten healthy subjects and 20 patients with a variety of intracranial pathologies. Field Strength/Sequence At 3 T, MPRAGE, T2‐weighted SPACE, SPACE FLAIR, and SWI were acquired at 9‐fold acceleration using Wave‐CAIPI and for comparison at 2–4‐fold acceleration using conventional GRAPPA. Assessment Extensive simulations were performed to optimize the Wave‐CAIPI protocol and minimize both g‐factor noise amplification and potential T1/T2 blurring artifacts. Moreover, refinements in the autocalibrated reconstruction of Wave‐CAIPI were developed to ensure high‐quality reconstructions in the presence of gradient imperfections. In a randomized and blinded fashion, three neuroradiologists assessed the diagnostic quality of the optimized 6‐minute Wave‐CAIPI exam and compared it to the roughly 3× slower GRAPPA accelerated protocol using both an individual and head‐to‐head analysis. Statistical Test A noninferiority test was used to test whether the diagnostic quality of Wave‐CAIPI was noninferior to the GRAPPA acquisition, with a 15% noninferiority margin. Results Among all sequences, Wave‐CAIPI achieved negligible g‐factor noise amplification (gavg ≤ 1.04) and burring artifacts from T1/T2 relaxation. Improvements of our autocalibration approach for gradient imperfections enabled increased robustness to gradient mixing imperfections in tilted‐field of view (FOV) prescriptions as well as variations in gradient and analog‐to‐digital converter (ADC) sampling rates. In the clinical evaluation, Wave‐CAIPI achieved similar mean scores when compared with GRAPPA (MPRAGE: ØW = 4.03, ØG = 3.97; T2w SPACE: ØW = 4.00, ØG = 4.00; SPACE FLAIR: ØW = 3.97, ØG = 3.97; SWI: ØW = 3.93, ØG = 3.83) and was statistically noninferior (N = 30, P < 0.05 for all sequences). Data Conclusion The proposed volumetric brain exam retained comparable image quality when compared with the much longer conventional protocol. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:961–974.