Department of Radiological Sciences, University of California, Los Angeles, California.
Physics and Biology in Medicine IDP, University of California, Los Angeles, California.
Magn Reson Med. 2019 Apr;81(4):2374-2384. doi: 10.1002/mrm.27565. Epub 2018 Nov 28.
To develop and evaluate a multishot diffusion-prepared (DP) magnitude-stabilized balanced steady-state free precession (bSSFP) diffusion imaging sequence with improved geometric fidelity.
A signal spoiler (magnitude stabilizer; MS) was implemented in a DP-bSSFP diffusion sequence. Effects of magnitude stabilizers with respect to phase errors were simulated using Bloch simulation. Phantom study was conducted to compare the apparent diffusion coefficient (ADC) accuracy and geometric reliability, quantified using target registration error (TRE), with diffusion-weighted single-shot echo-planar imaging (DW-ssEPI). Six volunteers were recruited. DW-ssEPI, DP-bSSFP with and without ECG triggering, and DP-MS-bSSFP with and without ECG triggering were acquired 10 times with b = 500 s/mm in a single-shot manner to evaluate magnitude variability. Diffusion trace images and diffusion tensor images were acquired using a 4-shot DP-MS-bSSFP.
Simulation showed that the DP-MS-bSSFP approach is insensitive to phase errors. The DP-MS-bSSFP approach had satisfactory ADC accuracy on the phantom with <5% difference with DW-ssEPI. The mean/max TRE for DW-ssEPI was 2.31/4.29 mm and was 0.51/1.20 mm for DP-MS-bSSFP. In the repeated single-shot study, DP-bSSFP without ECG triggering had severe signal void artifacts and exhibited a nonrepeatable pattern, which can be partially mitigated by ECG triggering. Adding the MS provided stable signal magnitude across all repetitions. High-quality ADC maps and color-coded fractional anisotropy maps were generated using the 4-shot DP-MS-bSSFP. The mean/max TRE was 2.89/10.80 mm for DW-ssEPI and 0.59/1.69 mm for DP-MS-bSSFP. Good agreements of white matter ADC, cerebrospinal fluid ADC, and white matter fractional anisotropy value were observed between DP-MS-bSSFP and DW-ssEPI.
The proposed DP-MS-bSSFP approach provided high-quality diffusion-weighted and diffusion-tensor images with minimal geometric distortion.
开发和评估一种具有改进的几何保真度的多-shot 扩散准备（DP）幅度稳定平衡稳态自由进动（bSSFP）扩散成像序列。
在 DP-bSSFP 扩散序列中实现了信号扰流器（幅度稳定器；MS）。使用 Bloch 模拟模拟了幅度稳定器对相位误差的影响。进行了体模研究，以比较表观扩散系数（ADC）的准确性和几何可靠性，使用目标注册误差（TRE）进行量化，与扩散加权单次激发回波平面成像（DW-ssEPI）进行比较。招募了 6 名志愿者。使用 DW-ssEPI、带和不带 ECG 触发的 DP-bSSFP 以及带和不带 ECG 触发的 DP-MS-bSSFP 在单次激发方式下采集 10 次 b = 500 s/mm 的数据，以评估幅度变化。使用 4-shot DP-MS-bSSFP 采集扩散轨迹图像和扩散张量图像。
模拟表明 DP-MS-bSSFP 方法对相位误差不敏感。DP-MS-bSSFP 方法在体模上具有令人满意的 ADC 准确性，与 DW-ssEPI 的差异小于 5%。DW-ssEPI 的平均/最大 TRE 为 2.31/4.29mm，DP-MS-bSSFP 为 0.51/1.20mm。在重复单次激发研究中，没有 ECG 触发的 DP-bSSFP 具有严重的信号空洞伪影，并表现出不可重复的模式，这可以通过 ECG 触发部分缓解。添加 MS 可在所有重复中提供稳定的信号幅度。使用 4-shot DP-MS-bSSFP 生成高质量的 ADC 图和彩色编码各向异性分数图。DW-ssEPI 的平均/最大 TRE 为 2.89/10.80mm，DP-MS-bSSFP 为 0.59/1.69mm。DP-MS-bSSFP 与 DW-ssEPI 之间观察到白质 ADC、脑脊液 ADC 和白质各向异性分数值具有良好的一致性。
所提出的 DP-MS-bSSFP 方法提供了具有最小几何变形的高质量扩散加权和扩散张量图像。
