Time‐efficient, high‐resolution 3T whole‐brain relaxometry using 3D‐QALAS with wave‐CAIPI readouts

• Published in: Magnetic resonance in medicine 2024-02, Vol.91 (2), p.630-639
• Main Authors: Cho, Jaejin, Gagoski, Borjan, Kim, Tae Hyung, Wang, Fuyixue, Manhard, Mary Kate, Dean, Douglas, Kecskemeti, Steven, Caprihan, Arvind, Lo, Wei‐Ching, Splitthoff, Daniel Nico, Liu, Wei, Polak, Daniel, Cauley, Stephen, Setsompop, Kawin, Grant, Patricia Ellen, Bilgic, Berkin
• Format: Article
• Language: English
• Subjects: 3D‐QALAS; Algorithms; Brain; Brain mapping; Inhomogeneity; Mapping; Neuroimaging; Parameters; Proton density (concentration); T1/T2/PD mapping; time‐efficient quantitative mapping; wave‐CAIPI
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.29865

Purpose Volumetric, high‐resolution, quantitative mapping of brain‐tissue relaxation properties is hindered by long acquisition times and SNR challenges. This study combines time‐efficient wave–controlled aliasing in parallel imaging (wave‐CAIPI) readouts with the 3D quantification using an interleaved Look‐Locker acquisition sequence with a T2 preparation pulse (3D‐QALAS), enabling full‐brain quantitative T1, T2, and proton density (PD) maps at 1.15‐mm3 isotropic voxels in 3 min. Methods Wave‐CAIPI readouts were embedded in the standard 3D‐QALAS encoding scheme, enabling full‐brain quantitative parameter maps (T1, T2, and PD) at acceleration factors of R = 3 × 2 with minimum SNR loss due to g‐factor penalties. The quantitative parameter maps were estimated using a dictionary‐based mapping algorithm incorporating inversion efficiency and B1‐field inhomogeneity effects. The parameter maps using the accelerated protocol were quantitatively compared with those obtained from the conventional 3D‐QALAS sequence using GRAPPA acceleration of R = 2 in the ISMRM/NIST phantom, and in 10 healthy volunteers. Results When tested in both the ISMRM/NIST phantom and 10 healthy volunteers, the quantitative maps using the accelerated protocol showed excellent agreement against those obtained from conventional 3D‐QALAS at RGRAPPA = 2. Conclusion Three‐dimensional QALAS enhanced with wave‐CAIPI readouts enables time‐efficient, full‐brain quantitative T1, T2, and PD mapping at 1.15 mm3 in 3 min at R = 3 × 2 acceleration. The quantitative maps obtained from the accelerated wave‐CAIPI 3D‐QALAS protocol showed very similar values to those from the standard 3D‐QALAS (R = 2) protocol, alluding to the robustness and reliability of the proposed method.