Division of Radiation Biophysics, Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, United States of America.
Harvard Medical School, Boston, MA 02115, United States of America.
Phys Med Biol. 2023 Sep 1;68(17):175045. doi: 10.1088/1361-6560/acf10c.
Diffusion-weighted MR imaging (DW-MRI) is known to quantify muscle fiber directionality and thus may be useful for radiotherapy target definition in sarcomas. Here, we investigate the variability of tissue anisotropy derived from diffusion tensor (DT) in the human thigh to establish the baseline parameters and protocols for DW-MRI acquisition for future studies in sarcoma patients.We recruited ten healthy volunteers to acquire diffusion-weighted MR images of the left and right thigh. DW-MRI data were used to reconstruct DT eigenvectors within each individual thigh muscle. Deviations of the principal eigenvector from its mean were calculated for different experimental conditions.Within the majority of muscles in most subjects, the mode of the histogram of the angular deviation of the principal eigenvector of the water DT from its muscle-averaged value did not exceed 20°. On average for all subjects, the mode ranged from 15° to 24°. Deviations much larger than 20° were observed in muscles far from the RF coil, including cases with significant amounts of subcutaneous fat and muscle deformation under its own weight.Our study is a robust characterization of angular deviations of muscle fiber directionality in the thigh as determined by DW-MRI. We show that an appropriate choice of experimental conditions reduces the variability of the observed directionality. Precise determination of tissue directionality will enable reproducible models of microscopic tumor spread, with future application in defining the clinical target volume for soft tissue sarcoma.
弥散加权磁共振成像（DW-MRI）可定量评估肌肉纤维的方向性，因此可能有助于肉瘤放射治疗靶区的定义。在此，我们研究了来自人类大腿的弥散张量（DT）的组织各向异性的可变性，以建立 DW-MRI 采集的基线参数和方案，用于未来的肉瘤患者研究。我们招募了 10 名健康志愿者，对他们的左右大腿进行了弥散加权磁共振成像。DW-MRI 数据用于在每个个体大腿肌肉内重建 DT 本征向量。为不同的实验条件计算了主本征向量与其肌肉平均值的角度偏差的偏差。在大多数受试者的大多数肌肉中，水 DT 的主本征向量的角度偏差的直方图的模式不超过 20°。对于所有受试者的平均值，模式范围在 15°到 24°之间。在远离 RF 线圈的肌肉中观察到远大于 20°的偏差，包括存在大量皮下脂肪和肌肉在自身重量下变形的情况。我们的研究是对 DW-MRI 确定的大腿肌肉纤维方向性的角度偏差的稳健特征描述。我们表明，适当选择实验条件可以降低观察到的方向性的可变性。组织方向性的精确确定将能够实现微观肿瘤扩散的可重复模型，未来将应用于定义软组织肉瘤的临床靶区。
