Quantitative evaluation of passive elastic properties of an individual skeletal muscle in vivo is among the major challenges of biomechanics, and its clinical application is severely limited. By combining shear-wave elastography (SWE) and B-mode imaging techniques, this study develops a novel non-invasive method to measure the local elastic modulus-fascicle strain curve of human pennation muscle during passive stretching using a single probe. Physiologically meaningful parameters are estimated and compared in subjects with different ages or pathological conditions. The in vivo experimental group comprised 12 healthy subjects (four children, four adults, and four seniors) and eight patients (four suffering from pseudohypertrophy, four from atrophy). Their gastrocnemius muscles were passively stretched using an ankle joint motion instrument. Local elastic moduli of the muscle were measured using SWE imaging frames and a built-in ‘F-ROI’ tool. The corresponding fascicle strains were simultaneously obtained using B-mode imaging frames and a gradient Radon transform. Three parameters (η, μ, G₀) were estimated from a normalized elastic modulus-strain curve using the Gauss–Newton method. The measured elastic modulus-strain curves all agreed with models of the estimated parameters (0.910 < R² < 0.999) and presented different patterns among normal and diseased subjects. η values were lower for pseudohypertrophies (1.93 ± 0.12), but higher for atrophies (63.40 ± 98.89), compared with normal ones (6.02 ± 2.53). In addition, μ values were higher for pseudohypertrophies (22.65 ± 16.40), but lower for atrophies (0.28 ± 0.41), compared with normal ones (1.07 ± 1.22). The proposed method may provide novel insight into the biomechanics of pennate muscle and has the potential to serve for clinical musculoskeletal medical diagnosis, as the single-probe scanning setup is broadly accepted.

体内单个骨骼肌被动弹性特性的定量评估是生物力学的主要挑战之一，其临床应用受到严重限制。通过结合剪切波弹性成像 (SWE) 和 B 模式成像技术，本研究开发了一种新的非侵入性方法，用于使用单个探头测量被动拉伸过程中人体羽状肌的局部弹性模量 - 束应变曲线。在具有不同年龄或病理状况的受试者中估计和比较具有生理意义的参数。在体内实验组包括12名健康受试者（4名儿童、4名成人和4名老年人）和8名患者（4名患有假性肥大，4名患有萎缩症）。他们的腓肠肌使用踝关节运动仪器被动拉伸。使用 SWE 成像框架和内置的“F-ROI”工具测量肌肉的局部弹性模量。使用 B 模式成像帧和梯度氡变换同时获得相应的束应变。三个参数（η、μ、G ₀）是使用高斯-牛顿法从归一化弹性模量-应变曲线估计的。测得的弹性模量-应变曲线都与估计参数的模型一致（0.910 <  R ² < 0.999) 并在正常和患病受试者中呈现不同的模式。与正常的 (6.02 ± 2.53) 相比，假性肥大的η值较低 (1.93 ± 0.12)，但萎缩的η值较高 (63.40 ± 98.89)。此外，与正常人 (1.07 ± 1.22) 相比，假性肥大 (22.65 ± 16.40) 的μ值较高，但萎缩 (0.28 ± 0.41) 的μ值较低。所提出的方法可以提供对羽状肌生物力学的新见解，并且有可能用于临床肌肉骨骼医学诊断，因为单探针扫描设置被广泛接受。