Filli Lukas, Piccirelli Marco, Kenkel David, Guggenberger Roman, Andreisek Gustav, Beck Thomas, Runge Val M, Boss Andreas
From the *Institute of Diagnostic and Interventional Radiology and †Department of Neuroradiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland; and ‡MR Application Development, Siemens Healthcare, Erlangen, Germany.
Invest Radiol. 2015 Jul;50(7):456-63. doi: 10.1097/RLI.0000000000000151.
The aim of this study was to investigate the feasibility of accelerated diffusion tensor imaging (DTI) of skeletal muscle using echo planar imaging (EPI) applying simultaneous multislice excitation with a blipped controlled aliasing in parallel imaging results in higher acceleration unaliasing technique.
After federal ethics board approval, the lower leg muscles of 8 healthy volunteers (mean [SD] age, 29.4 [2.9] years) were examined in a clinical 3-T magnetic resonance scanner using a 15-channel knee coil. The EPI was performed at a b value of 500 s/mm2 without slice acceleration (conventional DTI) as well as with 2-fold and 3-fold acceleration. Fractional anisotropy (FA) and mean diffusivity (MD) were measured in all 3 acquisitions. Fiber tracking performance was compared between the acquisitions regarding the number of tracks, average track length, and anatomical precision using multivariate analysis of variance and Mann-Whitney U tests.
Acquisition time was 7:24 minutes for conventional DTI, 3:53 minutes for 2-fold acceleration, and 2:38 minutes for 3-fold acceleration. Overall FA and MD values ranged from 0.220 to 0.378 and 1.595 to 1.829 mm2/s, respectively. Two-fold acceleration yielded similar FA and MD values (P ≥ 0.901) and similar fiber tracking performance compared with conventional DTI. Three-fold acceleration resulted in comparable MD (P = 0.199) but higher FA values (P = 0.006) and significantly impaired fiber tracking in the soleus and tibialis anterior muscles (number of tracks, P < 0.001; anatomical precision, P ≤ 0.005).
Simultaneous multislice EPI with blipped controlled aliasing in parallel imaging results in higher acceleration can remarkably reduce acquisition time in DTI of skeletal muscle with similar image quality and quantification accuracy of diffusion parameters. This may increase the clinical applicability of muscle anisotropy measurements.
本研究旨在探讨采用回波平面成像（EPI）并应用同时多切片激发与并行成像中的带伪影控制的混叠校正技术（blipped controlled aliasing in parallel imaging results in higher acceleration unaliasing technique，简称CAIPI）来实现骨骼肌加速扩散张量成像（DTI）的可行性。
经联邦伦理委员会批准后，使用15通道膝关节线圈，在临床3-T磁共振扫描仪中对8名健康志愿者（平均[标准差]年龄，29.4[2.9]岁）的小腿肌肉进行检查。在b值为500 s/mm²的情况下，分别进行无切片加速的EPI（传统DTI）以及2倍和3倍加速的EPI。在所有这3次采集过程中测量分数各向异性（FA）和平均扩散率（MD）。使用方差分析和曼-惠特尼U检验，比较这3次采集在纤维束追踪性能方面的差异，包括纤维束数量、平均纤维束长度和解剖学精度。
传统DTI的采集时间为7分24秒，2倍加速时为3分53秒，3倍加速时为2分38秒。总体FA值范围为0.220至0.378，MD值范围为1.595至1.829 mm²/s。与传统DTI相比，2倍加速产生的FA和MD值相似（P≥0.901），纤维束追踪性能也相似。3倍加速导致MD值相当（P = 0.199），但FA值更高（P = 0.006），并且比目鱼肌和胫骨前肌的纤维束追踪明显受损（纤维束数量，P < 0.001；解剖学精度，P≤0.005）。
采用并行成像中的带伪影控制的混叠校正技术的同时多切片EPI能够实现更高的加速，可显著减少骨骼肌DTI的采集时间，同时保持相似的图像质量和扩散参数的定量准确性。这可能会提高肌肉各向异性测量的临床适用性。
