Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA.
Magn Reson Med. 2024 Feb;91(2):497-512. doi: 10.1002/mrm.29862. Epub 2023 Oct 10.
To determine the sensitivity profiles of probabilistic and deterministic DTI tractography methods in estimating geometric properties in arm muscle anatomy.
Spin-echo diffusion-weighted MR images were acquired in the dominant arm of 10 participants. Both deterministic and probabilistic tractography were performed in two different muscle architectures of the parallel-structured biceps brachii (and the pennate-structured flexor carpi ulnaris. Muscle fascicle geometry estimates and number of fascicles were evaluated with respect to tractography turning angle, polynomial fitting order, and SNR. The DTI tractography estimated fascicle lengths were compared with measurements obtained from conventional cadaveric dissection and ultrasound modalities.
The probabilistic method generally estimated fascicle lengths closer to ranges reported by conventional methods than the deterministic method, most evident in the biceps brachii (p > 0.05), consisting of longer, arc-like fascicles. For both methods, a wide turning angle (50º-90°) generated fascicle lengths that were in close agreement with conventional methods, most evident in the flexor carpi ulnaris (p > 0.05), consisting of shorter, feather-like fascicles. The probabilistic approach produced at least two times more fascicles than the deterministic approach. For both approaches, second-order fitting yielded about double the complete tracts as third-order fitting. In both muscles, as SNR decreased, deterministic tractography produced less fascicles but consistent geometry (p > 0.05), whereas probabilistic tractography produced a consistent number but altered geometry of fascicles (p < 0.001).
Findings from this study provide best practice recommendations for implementing DTI tractography in skeletal muscle and will inform future in vivo studies of healthy and pathological muscle structure.
确定概率和确定性弥散张量成像（DTI）追踪方法在估计手臂肌肉解剖结构的几何性质方面的敏感谱。
在 10 名参与者的优势手臂中采集自旋回波扩散加权 MR 图像。在两种不同的肌肉结构中进行了确定性和概率追踪，分别是平行结构肱二头肌（和羽状结构尺侧腕屈肌。根据追踪的转向角度、多项式拟合阶数和 SNR，评估肌束几何估计值和肌束数量。将 DTI 追踪估计的肌束长度与从常规尸体解剖和超声模式获得的测量值进行比较。
概率方法通常比确定性方法更接近常规方法报告的范围来估计肌束长度，在肱二头肌中最为明显（p>0.05），由较长的弧形肌束组成。对于两种方法，较大的转向角度（50°-90°）产生的肌束长度与常规方法非常吻合，在尺侧腕屈肌中最为明显（p>0.05），由较短的羽毛状肌束组成。概率方法产生的肌束数量至少是确定性方法的两倍。对于两种方法，二阶拟合产生的完整束比三阶拟合多一倍。在两种肌肉中，随着 SNR 的降低，确定性追踪产生的肌束较少，但几何形状一致（p>0.05），而概率追踪产生的肌束数量一致，但肌束的几何形状发生了改变（p<0.001）。
本研究的结果为在骨骼肌中实施 DTI 追踪提供了最佳实践建议，并将为健康和病理性肌肉结构的未来体内研究提供信息。
