Dong Yiming, Najac Chloé, van Osch Matthias J P, Webb Andrew, Börnert Peter, Lena Beatrice
C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.
Philips Research Hamburg, Hamburg, Germany.
Magn Reson Med. 2025 Jul;94(1):119-133. doi: 10.1002/mrm.30442. Epub 2025 Jan 29.
To evaluate accelerated T- and T-mapping techniques for ultra-low-field MRI using low-rank reconstruction methods.
Two low-rank-based algorithms, image-based locally low-rank (LLR) and k-space-based structured low-rank (SLR), were implemented to accelerate T and T mapping on a 46 mT Halbach MRI scanner. Data were acquired with 3D turbo spin-echo sequences using variable-density poisson-disk random sampling patterns. For validation, phantom and in vivo experiments were performed on six healthy volunteers to compare the obtained values with literature and to study reconstruction performance at different undersampling factors and spatial resolutions. In addition, the reconstruction performance of the LLR and SLR algorithms for T mapping was compared using retrospective undersampling datasets. Total scan times were reduced from 45/38 min (R = 1) to 23/19 min (R = 2) and 11/9 min (R = 4) for a 2.5 × 2.5 × 5 mm resolution, and to 18/16 min (R = 4) for a higher in-plane resolution 1.5 × 1.5 × 5 mm for T/T mapping, respectively.
Both LLR and SLR algorithms successfully reconstructed T and T maps from undersampled data, significantly reducing scan times and eliminating undersampling artifacts. Phantom validation showed that consistent T and T values were obtained at different undersampling factors up to R = 4. For in vivo experiments, comparable image quality and estimated T and T values were obtained for fully sampled and undersampled (R = 4) reconstructions, both of which were in line with the literature values.
The use of low-rank reconstruction allows significant acceleration of T and T mapping in low-field MRI while maintaining image quality.
使用低秩重建方法评估用于超低场磁共振成像（MRI）的加速T值和T2*值映射技术。
在一台46 mT的哈尔巴赫MRI扫描仪上，实现了两种基于低秩的算法，即基于图像的局部低秩（LLR）和基于k空间的结构化低秩（SLR），以加速T值和T2值映射。使用可变密度泊松盘随机采样模式，通过3D快速自旋回波序列采集数据。为了进行验证，对六名健康志愿者进行了体模和体内实验，将获得的值与文献进行比较，并研究不同欠采样因子和空间分辨率下的重建性能。此外，使用回顾性欠采样数据集比较了LLR和SLR算法对T2值映射的重建性能。对于2.5×2.5×5 mm分辨率的T/T2值映射，总扫描时间分别从45/38分钟（R = 1）减少到23/19分钟（R = 2）和11/9分钟（R = 4），对于更高的面内分辨率1.5×1.5×5 mm的T/T2值映射，总扫描时间减少到18/16分钟（R = 4）。
LLR和SLR算法均成功地从欠采样数据中重建了T值和T2值映射，显著减少了扫描时间并消除了欠采样伪影。体模验证表明，在高达R = 4的不同欠采样因子下，获得了一致的T值和T2值。对于体内实验，全采样和欠采样（R = 4）重建获得了可比的图像质量以及估计的T值和T2*值，两者均与文献值一致。
使用低秩重建可在保持图像质量的同时，显著加速低场MRI中的T值和T2*值映射。
