Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China; Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen, Guangdong, China.
Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China.
J Magn Reson. 2022 Jul;340:107232. doi: 10.1016/j.jmr.2022.107232. Epub 2022 Apr 30.
Positive susceptibility contrast imaging (PSCI) based on susceptibility mapping exhibits excellent efficacy for visualizing magnetic resonance (MR)-compatible metallic devices because of their high magnetic susceptibility compared to that of human tissues. However, the long-acquisition time required by the two-dimensional fast spin echo (2D FSE)-based PSCI approach, impedes its practical applications in 3D imaging. In this study, a three-dimensional (3D) susceptibility-based variable flip angle (vFA) FSE sequence was proposed to accelerate data acquisition in the clinical radiotherapy applications of ex vivo and in vivo rapid 3D PSCI for the imaging of metal seeds. Here, the proposed scheme applied a 3D modulated vFA technique for refocused imaging with an extended echo-train sequence for sampling data. The scheme integrated the projection-onto-dipole fields (PDF) to remove the background field and accelerate PSCI by using a compressive sensing framework with a variable-densitysampling mask. The experiments involved some gelatin phantoms, porcine tissues and patients with scapular tumors and brachytherapy seeds. All of the experimental results showed that the proposed scheme could accelerate data acquisition of 3D PSCI at the reduction factors of 2 ∼ 5 while accurately localizing the actual positions of the brachytherapy seeds in the ex vivo and in vivo applications. The results were compared with those of the existing methods, including susceptibility gradient mapping using the original resolution (SUMO) and gradient echo acquisition for superparamagnetic particle (GRASP).
基于磁化率映射的正磁化率对比成像（PSCI）在显示磁共振（MR）兼容的金属设备方面具有出色的效果，因为它们的磁化率比人体组织高。然而，基于二维快速自旋回波（2D FSE）的 PSCI 方法需要较长的采集时间，这阻碍了其在 3D 成像中的实际应用。在这项研究中，提出了一种基于三维（3D）磁化率的可变翻转角（vFA）FSE 序列，以加速在临床放射治疗应用中外科和体内快速 3D PSCI 中用于金属种子成像的体外和体内快速 3D PSCI 的数据采集。在这里，所提出的方案应用了一种 3D 调制 vFA 技术，用于具有扩展回波链序列的数据采样的重聚焦成像。该方案将投影到偶极子场（PDF）集成到通过具有可变密度采样掩模的压缩感知框架中以去除背景场并加速 PSCI。该实验涉及一些明胶体模、猪组织以及肩胛骨肿瘤和近距离放射治疗种子的患者。所有的实验结果表明，该方案能够在减少因子为 2 至 5 的情况下加速 3D PSCI 的数据采集，同时在体外和体内应用中准确地定位近距离放射治疗种子的实际位置。结果与现有的方法进行了比较，包括使用原始分辨率的磁化率梯度映射（SUMO）和超顺磁粒子的梯度回波采集（GRASP）。
