School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.
MR Research Collaboration, Siemens Healthcare Limited, Frimley, United Kingdom.
Magn Reson Med. 2021 Mar;85(3):1441-1454. doi: 10.1002/mrm.28527. Epub 2020 Sep 28.
To achieve three-dimensional (3D) distortion-free apparent diffusion coefficient (ADC) maps for prostate imaging using a multishot diffusion prepared-gradient echo (msDP-GRE) sequence and ADC dictionary matching.
The msDP-GRE sequence is combined with a 3D Cartesian, centric k-space trajectory with center oversampling. Oversampled k-space center averaging and phase cycling are used to address motion- and eddy current-induced magnitude corruption. Extended-phase-graph (EPG) simulations and ADC dictionary matching are used to compensate for T effects. To shorten the acquisition time, each volume is undersampled by a factor of two and reconstructed using iterative sensitivity encoding. The proposed approach is characterized using simulations and validated in a kiwifruit phantom, comparing the msDP-GRE ADC maps obtained using both standard monoexponential fitting and dictionary matching with the clinical standard single-shot diffusion weighted-echo planar imaging (ssDW-EPI) ADC. Initial in vivo feasibility is tested in three healthy subjects, and geometric distortion is compared with anatomical T -weighted-turbo spin echo.
In the kiwifruit phantom experiment, the signal magnitude could be recovered using k-space center averaging and phase cycling. No statistically significant difference was observed in the ADC values estimated using msDP-GRE with dictionary matching and clinical standard DW-EPI (P < .05). The in vivo prostate msDP-GRE scans were free of geometric distortion caused by off-resonance susceptibility, and the ADC values in the prostate were in agreement with values found in the published literature.
Nondistorted 3D ADC maps of the prostate can be achieved using a msDP sequence and dictionary matching.
使用多shot 扩散预备梯度回波（msDP-GRE）序列和 ADC 字典匹配，实现前列腺成像的三维（3D）无失真表观扩散系数（ADC）图。
将 msDP-GRE 序列与具有中心过采样的 3D 笛卡尔、中心 k 空间轨迹相结合。使用过采样 k 空间中心平均和相位循环来解决运动和涡流引起的幅度失真。扩展相位图（EPG）模拟和 ADC 字典匹配用于补偿 T 效应。为了缩短采集时间，每个体积的欠采样因子为 2，并使用迭代灵敏度编码进行重建。使用模拟和猕猴桃体模对所提出的方法进行了特征描述，并与临床标准单次激发扩散加权回波平面成像（ssDW-EPI）ADC 进行了比较，验证了 msDP-GRE ADC 图的获取。在三个健康受试者中测试了初步的体内可行性，并与解剖 T 加权涡轮自旋回波比较了几何失真。
在猕猴桃体模实验中，使用 k 空间中心平均和相位循环可以恢复信号幅度。使用字典匹配和临床标准 DW-EPI 的 msDP-GRE 估计的 ADC 值没有统计学差异（P <.05）。体内前列腺 msDP-GRE 扫描无由离共振磁化率引起的几何失真，并且前列腺中的 ADC 值与已发表文献中的值一致。
使用 msDP 序列和字典匹配可以实现前列腺的无失真 3D ADC 图。
