Highly‐accelerated volumetric brain examination using optimized wave‐CAIPI encoding

• Published in: Journal of magnetic resonance imaging 2019-09, Vol.50 (3), p.961-974
• Main Authors: Polak, Daniel, Cauley, Stephen, Huang, Susie Y., Longo, Maria Gabriela, Conklin, John, Bilgic, Berkin, Ohringer, Ned, Raithel, Esther, Bachert, Peter, Wald, Lawrence L., Setsompop, Kawin
• Format: Article
• Language: English
• Subjects: Acceleration; Adult; Aged; Aged, 80 and over; Amplification; Blurring; Brain; Brain - diagnostic imaging; Brain - pathology; Brain Diseases - diagnostic imaging; Brain Diseases - pathology; Converters; Defects; Diagnostic systems; Female; Field of view; Field strength; Humans; Image Interpretation, Computer-Assisted - methods; Image quality; Image reconstruction; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Medical imaging; Middle Aged; Neuroimaging; Noise; Organ Size; Population (statistical); Population studies; Prospective Studies; Quality assessment; Reproducibility of Results; Single-Blind Method; Statistical tests; Young Adult
• ISSN: 1053-1807; 1522-2586
• DOI: 10.1002/jmri.26678

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