Precise volume assessment for gastrocnemius muscles based on 3D ultrasound imaging.

Accurate muscle volume measurement is crucial for evaluating muscle impairment in healthcare and sports medicine. Compared to traditional methods, 3D ultrasound imaging offers noninvasive, flexible, cost-effectiveness advantages. This study aims to develop a precise volume assessment method for skeletal muscle, specifically gastrocnemius muscle, based on 3D ultrasound imaging. A feasible practice integrating 3D freehand ultrasound imaging based on optical tracking, slice extraction and alpha-shape-based surface reconstruction was proposed for precise volume assessment. 2D ultrasound images with spatial positions were acquired. Target slices were extracted for segmentation, and the alpha‑shape algorithm reconstructed the 3D muscle mesh for volume calculation. Phantom experiment using a pork tenderloin validated our method with a relative deviation of 0.47% compared to water displacement method. Clinical validation against MRI yielded relative deviations of 0.66% to 5.06% for manual segmentation and 0.28% to 2.58% for automated segmentation (using TransUNet). The method achieved smooth, detailed surfaces and outperformed Marching Cubes and Poisson reconstruction in accuracy and morphological fidelity. The proposed 3D freehand ultrasound workflow enables precise, detailed muscle volume assessment, showing strong agreement with MRI. Its accessibility and accuracy suggest significant potential for clinical and sports medicine applications in monitoring muscle health.