In vivo ultrasound–MRI 3D mapping of neuromuscular compartments reveals the neuromechanical architecture of finger-specific control

Neuromuscular compartments provide the functional substrate for finger-specific motor control, yet their in vivo three-dimensional (3D) architecture remains unresolved because of the absence of clear fascial landmarks for imaging. Here, we present a multimodal imaging framework combining ultrasound and magnetic resonance imaging (MRI) to provide volumetric compartment segmentation and in vivo architectural reconstruction of the flexor digitorum superficialis. During isolated finger flexion, tissue movement directions estimated from dynamic ultrasound delineate compartment contours, which are mapped into a 3D MRI reference to generate volumetric compartment masks.

Using these masks as constraints, tractography reconstructs 3D fiber trajectories and yields compartment-specific architectural measurements. In ten healthy individuals, compartment topology and fiber orientations were consistent with classic cadaveric anatomy, and estimated compartments accurately predicted surface electromyography amplitude distributions. This framework provides 3D fiber trajectories and quantitative parameters for finger-specific computational models, establishing a foundation for subject-specific neuromuscular digital twins and next-generation neuromuscular interfaces.

We thank the support from Siemens Healthineers Ltd. This work was supported in part by the National Natural Science Foundation of China (Grants No. 52227808 and 52575026) and the Science and Technology Commission of Shanghai Municipality (Grant No. 24511103500). These authors contributed equally: Yang Li, Yang Yu, Yiming Kang.

These authors jointly supervised this work: Dario Farina, Xiangyang Zhu. State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China Yang Li (李洋), Yang Yu (于洋), Yiming Kang (康亦铭), Zongtian Yin (尹宗天), Yuxuan Wei (魏玉烜), Xinjun Sheng (盛鑫军) & Xiangyang Zhu (朱向阳) Shanghai Key Laboratory of Intelligent Robotics, Shanghai Jiao Tong University, Shanghai, China Yang Yu (于洋), Xinjun Sheng (盛鑫军) & Xiangyang Zhu (朱向阳) Meta Robotics Institute, Shanghai Jiao Tong University, Shanghai, China Department of Bioengineering, Imperial College London, London, UK MR Research Collaborations, Siemens Healthineers Ltd., Shanghai, China Correspondence to Yang Yu (于洋), Dario Farina or Xiangyang Zhu (朱向阳). Y.L., Y.Y. (applicant), X.J. and X.Z. are inventors on a pending Chinese patent application (No. 202611328235.2) related to the methodology described in this article.

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