GE Healthcare, Brondby, Denmark.
MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
NMR Biomed. 2023 Feb;36(2):e4835. doi: 10.1002/nbm.4835. Epub 2022 Oct 11.
Sodium MRI allows the non-invasive quantification of intra-organ sodium concentration. RF inhomogeneity introduces uncertainty in this estimated concentration. B field corrections can be used to overcome some of these limitations. However, the low signal-to-noise ratio in sodium MRI makes accurate B mapping in reasonable scan times challenging. The study aims to evaluate Bloch-Siegert off-resonance (BLOSI) B field correction for sodium MRI using a 3D Fermat looped, orthogonally encoded trajectories (FLORET) read-out trajectory. We propose a clinically feasible B field map correction method for sodium imaging at 3 T, evaluating five healthy subjects' brain, heart blood, kidneys, and thigh muscle. We scanned the subjects twice for repeatability measures and used sodium phantoms to determine organ total sodium concentration. Conventional proton scans were compared with sodium images for organ structural integrity. The BLOSI approach based on the 3D FLORET read-out trajectory was used in B field correction and 3D density-adapted radial acquisition for sodium imaging. Results indicate improvements in sodium imaging based on B field correction in a clinically feasible protocol. Improvements are determined in all organs by enhanced anatomical representation, organ homogeneity, and an increase in the total sodium concentration after applying a B field correction. The proposed BLOSI-based B field correction using a 3D FLORET read-out trajectory is clinically feasible for sodium imaging, which is shown in the brain, heart, kidney, and thigh muscle. This supports using fast B field mapping in the clinical setting.
钠磁共振成像允许对器官内的钠浓度进行非侵入性定量。射频不均匀性会给估计的浓度带来不确定性。可以使用 B 场校正来克服这些限制的一部分。然而，钠磁共振成像中的低信噪比使得在合理的扫描时间内准确地进行 B 映射具有挑战性。本研究旨在评估使用 3D 费马循环、正交编码轨迹（FLORET）读出轨迹的布洛赫-西格勒离共振（BLOSI）B 场校正对钠磁共振成像的影响。我们提出了一种在 3T 下用于钠成像的临床可行的 B 场图校正方法，对五名健康受试者的大脑、心脏血液、肾脏和大腿肌肉进行了评估。我们对受试者进行了两次扫描以进行重复性测量，并使用钠体模来确定器官总钠浓度。常规质子扫描与钠图像进行了比较，以评估器官结构的完整性。基于 3D FLORET 读出轨迹的 BLOSI 方法用于 B 场校正和 3D 密度自适应径向采集进行钠成像。结果表明，基于临床可行方案的 B 场校正可改善钠成像。通过增强解剖学表示、器官均匀性以及在应用 B 场校正后总钠浓度的增加，确定了所有器官中的改善。使用 3D FLORET 读出轨迹的基于 BLOSI 的 B 场校正对于钠成像具有临床可行性，这在大脑、心脏、肾脏和大腿肌肉中得到了证明。这支持在临床环境中使用快速 B 场映射。
