结合扩散与弛豫的MRI技术可更准确评估肌肉微观结构和血流。
Combined Diffusion-Relaxation MRI to Assess Muscle Microstructure and Composition
- 在12分钟内同步采集扩散与弛豫数据，提升微结构解析能力。
- 相比传统方法，新方法使血管分数估算误差降低至RMSE=0.03。
- 适用于运动训练、康复及神经肌肉疾病非侵入性评估。
量化肌肉组织特性对理解骨骼肌病理生理变化至关重要。T2弛豫与扩散MRI（dMRI）是潜在有效手段，但传统方法分别测量两者，特异性不足。本文提出一种联合扩散-弛豫MRI方法，以解耦肌肉中T2与扩散特性。在3T扫描仪上采用单层12分钟协议，整合6个b值与4个回波时间（TE）。5名健康受试者参与实验，数据用六种微结构扩散及扩散-弛豫模型分析。手动分割小腿肌肉后提取均值参数。忽略T2弛豫的模型显示强烈TE依赖性：当TE从50增至90毫秒时，平均扩散率（MD）下降达47%，各向异性（FA）上升75%，血管分数（fv）升高297%。而扩散-弛豫模型则获得无TE依赖估计结果。组织与血管弛豫时间分别为31–36毫秒（T2t）与66–86毫秒（T2v）。模拟验证了其对fv估计的高精度（r=0.95；RMSE=0.03）及显著降低的TE偏差。该方法可提供稳健、无回波时间依赖性的肌肉微结构与灌注相关生物标志物，尤其在血管分数估算方面有显著提升，具备评估肌肉生理、运动适应、康复及神经肌肉疾病的潜力。
原文摘要 · Abstract (English)
Quantifying muscle tissue properties is crucial for understanding pathophysiological changes occurring in skeletal muscle (SM). In particular, T2 relaxation and diffusion MRI (dMRI) are promising techniques. However, typical methods measure T2 and diffusion separately, making them less specific to microstructure than emerging combined diffusion-relaxation techniques. Here we demonstrate a combined diffusion-relaxation MRI approach for disentangling T2 and diffusivity properties in SM. A diffusion-relaxation acquisition was implemented on a 3 T scanner, combining six b-values and four echo times within a 12-min single-slice protocol. Five healthy participants were enrolled. Data were analysed with six microstructural diffusion and diffusion-relaxation models. Mean parameter values were extracted from manually segmented calf muscles. Models neglecting T2 relaxation showed strong TE dependence: mean diffusivity (MD) decreased by up to 47\%, fractional anisotropy (FA) increased by up to 75\%, and vascular fraction fv increased by up to 297\% when TE increased from 50 to 90 ms. Diffusion-relaxation models produced TE-independent estimates. Tissue and vascular relaxation times ranged 31-36 ms T2t and 66-86 ms T2v, respectively. Simulations confirmed improved accuracy for fv estimation (r=0.95; RMSE=0.03) and reduced TE-related bias. Combined diffusion-relaxation MRI provides robust, TE-independent estimates of muscle microstructural and perfusion-related biomarkers. The quantitative improvements observed - particularly in the estimation of fv - show its potential to provide non-invasive biomarkers for the assessment of muscle physiology, exercise adaptation, rehabilitation, and neuromuscular pathology.
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