Department of Radiological Sciences, University of California, Los Angeles, California, USA.
Biomedical Physics Interdepartmental Program, University of California, Los Angeles, California, USA.
Magn Reson Med. 2018 Feb;79(2):663-672. doi: 10.1002/mrm.26709. Epub 2017 Apr 25.
To design and evaluate eddy current-nulled convex optimized diffusion encoding (EN-CODE) gradient waveforms for efficient diffusion tensor imaging (DTI) that is free of eddy current-induced image distortions.
The EN-CODE framework was used to generate diffusion-encoding waveforms that are eddy current-compensated. The EN-CODE DTI waveform was compared with the existing eddy current-nulled twice refocused spin echo (TRSE) sequence as well as monopolar (MONO) and non-eddy current-compensated CODE in terms of echo time (TE) and image distortions. Comparisons were made in simulations, phantom experiments, and neuro imaging in 10 healthy volunteers.
The EN-CODE sequence achieved eddy current compensation with a significantly shorter TE than TRSE (78 versus 96 ms) and a slightly shorter TE than MONO (78 versus 80 ms). Intravoxel signal variance was lower in phantoms with EN-CODE than with MONO (13.6 ± 11.6 versus 37.4 ± 25.8) and not different from TRSE (15.1 ± 11.6), indicating good robustness to eddy current-induced image distortions. Mean fractional anisotropy values in brain edges were also significantly lower with EN-CODE than with MONO (0.16 ± 0.01 versus 0.24 ± 0.02, P < 1 x 10 ) and not different from TRSE (0.16 ± 0.01 versus 0.16 ± 0.01, P = nonsignificant).
The EN-CODE sequence eliminated eddy current-induced image distortions in DTI with a TE comparable to MONO and substantially shorter than TRSE. Magn Reson Med 79:663-672, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
设计并评估用于高效弥散张量成像（DTI）的涡流补偿凸优化弥散编码（EN-CODE）梯度波形，该技术可消除涡流引起的图像失真。
采用 EN-CODE 框架生成涡流补偿的弥散编码波形。从回波时间（TE）和图像失真两方面，将 EN-CODE DTI 序列与现有的涡流补偿双反转聚焦自旋回波（TRSE）序列以及单极（MONO）和非涡流补偿 CODE 序列进行比较。在 10 名健康志愿者的模拟、体模实验和神经成像中进行了比较。
EN-CODE 序列实现了涡流补偿，TE 明显短于 TRSE（78 对 96 ms），略短于 MONO（78 对 80 ms）。EN-CODE 体模的体素内信号方差低于 MONO（13.6±11.6 对 37.4±25.8），与 TRSE 无差异（15.1±11.6），表明对涡流引起的图像失真具有良好的鲁棒性。脑边缘的平均各向异性分数值也明显低于 MONO（0.16±0.01 对 0.24±0.02，P<1×10），与 TRSE 无差异（0.16±0.01 对 0.16±0.01，P=非显著）。
EN-CODE 序列在 DTI 中消除了涡流引起的图像失真，TE 与 MONO 相当，明显短于 TRSE。磁共振医学 79:663-672,2018。©2017 国际磁共振学会。
