Evaluation of Ultrafast Wave-CAIPI MPRAGE for Visual Grading and Automated Measurement of Brain Tissue Volume

Abstract

BACKGROUND AND PURPOSE: Volumetric brain MR imaging typically has long acquisition times. We sought to evaluate an ultrafast MPRAGE sequence based on Wave-CAIPI (Wave-MPRAGE) compared with standard MPRAGE for evaluation of regional brain tissue volumes. MATERIALS AND METHODS: We performed scan-rescan experiments in 10 healthy volunteers to evaluate the intraindividual variability of the brain volumes measured using the standard and Wave-MPRAGE sequences. We then evaluated 43 consecutive patients undergoing brain MR imaging. Patients underwent 3T brain MR imaging, including a standard MPRAGE sequence (acceleration factor [R] ¼ 2, acquisition time [TA] ¼ 5.2 minutes) and an ultrafast Wave-MPRAGE sequence (R ¼ 9, TA ¼ 1.15 minutes for the 32-channel coil; R ¼ 6, TA ¼ 1.75 minutes for the 20-channel coil). Automated segmentation of regional brain volume was performed. Two radiologists evaluated regional brain atrophy using semiquantitative visual rating scales. RESULTS: The mean absolute symmetrized percent change in the healthy volunteers participating in the scan-rescan experiments was not statistically different in any brain region for both the standard and Wave-MPRAGE sequences. In the patients undergoing evaluation for neurodegenerative disease, the Dice coefficient of similarity between volumetric measurements obtained from standard and Wave-MPRAGE ranged from 0.86 to 0.95. Similarly, for all regions, the absolute symmetrized percent change for brain volume and cortical thickness showed ,6% difference between the 2 sequences. In the semiquantitative visual comparison, the differences between the 2 radiologists' scores were not clinically or statistically significant. CONCLUSIONS: Brain volumes estimated using ultrafast Wave-MPRAGE show low intraindividual variability and are comparable with those estimated using standard MPRAGE in patients undergoing clinical evaluation for suspected neurodegenerative disease. ABBREVIATIONS: ASPC ¼ absolute symmetrized percent change; VBM ¼ voxel-based morphometry V olumetric brain MR imaging is widely used in clinical and research settings for the evaluation of patients with suspected neurodegenerative disease. Regional patterns of tissue loss aid in generating a differential diagnosis and assessing prognosis, and the identification of regional volume loss is increasingly used as an outcome measure in trials of potentially disease-modifying therapies. 1-4 Of particular value, the T1-weighted MPRAGE sequence provides excellent spatial resolution and tissue contrast 5 but has long acquisition times due to the need to encode a large number of k-space lines and the added TI required to achieve the prepared T1-weighted contrast. Unfortunately, long

High-fidelity fast volumetric brain MRI using synergistic wave-controlled aliasing in parallel imaging and a hybrid denoising generative adversarial network

“…For 32-channel coils, HDnGAN could be employed to denoise Wave-CAIPI images with 10× and even higher acceleration to further reduce the scan time potential to within a minute. Further, HDnGAN could be used for Wave-CAIPI magnetization prepared rapid gradient echo (MPRAGE) 36,37 and susceptibility-weighted imaging 38 or images reconstructed using other methods such as compressed sensing and LORAKS 3,4 .…”

“…6, Table 2). Further, HDnGAN can be used for a variety of other Wave-CAIPI-accelerated 3D sequences beyond T 2 -weighted FLAIR 41 , including 3D T 1 -weighted magnetization prepared rapid gradient echo (MPRAGE) 15,52 , susceptibility-weighted imaging 53 , and T 1 -weighted SPACE 54,55 , as well as images reconstructed using other accelerated methods such as compressed sensing and LORAKS 10,56 . Finally, the generator of HDnGAN can be replaced with any CNN (e.g., variational network 57 ) that reconstructs images directly from k-space data in order to recover image sharpness and realistic textural details in the reconstructed images.…”

Evaluation of Ultrafast Wave–Controlled Aliasing in Parallel Imaging 3D-FLAIR in the Visualization and Volumetric Estimation of Cerebral White Matter Lesions

“…The time-savings incurred by Wave-FLAIR may become more obvious when aggregated with other optimized fast 2D and 3D sequences. 12,19,26,27 For example, at our institution, we have implemented the Wave-FLAIR sequence along with optimized simultaneous multislice diffusion-weighted imaging, Wave T2 SPACE, Wave-SWI, and pre-and postcontrast Wave-T1 MPRAGE sequences in the clinical MS brain MR imaging protocol, bringing the total scan time for this protocol ,20 minutes. The ability to acquire multiple 3D sequences with complementary contrasts efficiently, such as Wave-FLAIR and Wave-SWI, may encourage the greater adoption of promising imaging signs such as the central vein sign and paramagnetic rim sign, [28][29][30] which have greater specificity for demyelinating lesions in MS and, in the case of the paramagnetic rim sign, may have prognostic value in identifying lesions with chronic active inflammation associated with greater disability.…”

Evaluation of Ultrafast Wave-CAIPI 3D FLAIR in the Visualization and Volumetric Estimation of Cerebral White Matter Lesions

“…The time-savings incurred by Wave-FLAIR may become more obvious when aggregated with other optimized fast 2D and 3D sequences. 12, 19, 24, 25 For example, at our institution, we have implemented the Wave-FLAIR sequence along with optimized simultaneous multislice diffusion-weighted imaging, Wave T2 SPACE, Wave-SWI and pre- and post-contrast Wave-T1 MPRAGE sequences in the clinical multiple sclerosis brain MRI protocol, bringing the total scan time for this protocol below 20 minutes. The ability to acquire multiple 3D sequences with complementary contrasts efficiently, such as Wave-FLAIR and Wave-SWI, may encourage the greater adoption of promising imaging signs such as the central vein sign and paramagnetic rim sign 26-28 , which have greater specificity for demyelinating lesions in MS and, in the case of the paramagnetic rim sign, may have prognostic value in identifying lesions with chronic active inflammation associated with greater disability.…”