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.

Three-dimensional SPACE with 2D CAIPIRINHA sampling pattern enables high-quality 3D TSE MRI of the knee at an acquisition time of 5 minutes and image quality, visibility of anatomic structures, SNR, and CNR similar to conventional 3D SPACE and 2D TSE, both of which require approximately 10-minute acquisition times.

Compressed sensing MRCP using incoherent undersampling combined with CS reconstruction provided comparable image quality to conventional MRCP while reducing the acquisition time to within a single breath-hold (16 seconds).

We accept the hypothesis that prospective compressed sensing acceleration of SEMAC is feasible for high-quality metal artifact reduction MRI of cobalt-chromium knee arthroplasty implants in less than 5 minutes and yields better quality than high-BW TSE and similarly high quality than lengthier SEMAC pulse sequences.

BackgroundChanges in muscle fat composition as for example observed in sarcopenia or muscular dystrophy affect physical performance and muscular function, like strength and power. The purpose of the present study is to measure the repeatability of Dixon magnetic resonance imaging (MRI) for assessing muscle volume and fat in the thigh. Furthermore, repeatability of magnetic resonance spectroscopy (MRS) for assessing muscle fat is determined.MethodsA prototype 6‐point Dixon MRI method was used to measure muscle volume and muscle proton density fat fraction (PDFF) in the left thigh. PDFF was measured in musculus semitendinosus of the left thigh with a T2‐corrected multi‐echo MRS method. For the determination of short‐term repeatability (consecutive examinations), the root mean square coefficients of variation of Dixon MRI and MRS data of 23 young and healthy (29 ± 5 years) and 24 elderly men with sarcopenia (78 ± 5 years) were calculated. For the estimation of the long‐term repeatability (13 weeks between examinations), the root mean square coefficients of variation of MRI data of seven young and healthy (31 ± 7 years) and 23 elderly sarcopenic men (76 ± 5 years) were calculated. Long‐term repeatability of MRS was not determined.ResultsShort‐term errors of Dixon MRI volume measurement were between 1.2% and 1.5%, between 2.1% and 1.6% for Dixon MRI PDFF measurement, and between 9.0% and 15.3% for MRS. Because of the high short‐term repeatability errors of MRS, long‐term errors were not determined. Long‐term errors of MRI volume measurement were between 1.9% and 4.0% and of Dixon MRI PDFF measurement between 2.1% and 4.2%.ConclusionsThe high degree of repeatability of volume and PDFF Dixon MRI supports its use to predict future mobility impairment and measures the success of therapeutic interventions, for example, in sarcopenia in aging populations and muscular dystrophy. Because of possible inhomogeneity of fat infiltration in muscle tissue, the application of MRS for PDFF measurements in muscle is more problematic because this may result in high repeatability errors. In addition, the tissue composition within the MRS voxel may not be representative for the whole muscle.