Blip up‐down acquisition for spin‐ and gradient‐echo imaging (BUDA‐SAGE) with self‐supervised denoising enables efficient T2, T2, para‐ and dia‐magnetic susceptibility mapping

• Published in: Magnetic resonance in medicine Vol. 88; no. 2; pp. 633 - 650
• Main Authors: Zhang, Zijing, Cho, Jaejin, Wang, Long, Liao, Congyu, Shin, Hyeong‐Geol, Cao, Xiaozhi, Lee, Jongho, Xu, Jinmin, Zhang, Tao, Ye, Huihui, Setsompop, Kawin, Liu, Huafeng, Bilgic, Berkin
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.08.2022
• Subjects: Brain; Brain mapping; BUDA; Dipoles; Distortion; Echoes; Image contrast; Image reconstruction; In vivo methods and tests; Magnetic permeability; Magnetic resonance imaging; Magnetic susceptibility; Mapping; Neural networks; Neuroimaging; Noise reduction; QSM; SAGE; self‐supervised denoising; Separation; slider; source separation; Susceptibility; T2 mapping
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.29219

Purpose To rapidly obtain high resolution T2, T2*, and quantitative susceptibility mapping (QSM) source separation maps with whole‐brain coverage and high geometric fidelity. Methods We propose Blip Up‐Down Acquisition for Spin And Gradient Echo imaging (BUDA‐SAGE), an efficient EPI sequence for quantitative mapping. The acquisition includes multiple T2*‐, T2′‐, and T2‐weighted contrasts. We alternate the phase‐encoding polarities across the interleaved shots in this multi‐shot navigator‐free acquisition. A field map estimated from interim reconstructions was incorporated into the joint multi‐shot EPI reconstruction with a structured low rank constraint to eliminate distortion. A self‐supervised neural network (NN), MR‐Self2Self (MR‐S2S), was used to perform denoising to boost SNR. Using Slider encoding allowed us to reach 1 mm isotropic resolution by performing super‐resolution reconstruction on volumes acquired with 2 mm slice thickness. Quantitative T2 (=1/R2) and T2* (=1/R2*) maps were obtained using Bloch dictionary matching on the reconstructed echoes. QSM was estimated using nonlinear dipole inversion on the gradient echoes. Starting from the estimated R2/R2* maps, R2′ information was derived and used in source separation QSM reconstruction, which provided additional para‐ and dia‐magnetic susceptibility maps. Results In vivo results demonstrate the ability of BUDA‐SAGE to provide whole‐brain, distortion‐free, high‐resolution, multi‐contrast images and quantitative T2/T2* maps, as well as yielding para‐ and dia‐magnetic susceptibility maps. Estimated quantitative maps showed comparable values to conventional mapping methods in phantom and in vivo measurements. Conclusion BUDA‐SAGE acquisition with self‐supervised denoising and Slider encoding enables rapid, distortion‐free, whole‐brain T2/T2* mapping at 1 mm isotropic resolution under 90 s.