3D ultrasound fascicle tractography for objective muscle architecture analysis.

Muscle architecture plays a crucial role in muscle function, and its three-dimensional (3D) structure varies throughout life due to factors such as growth, training, and disease. However, measuring 3D muscle architecture directly in living patients is a complex task. Researchers have now developed a novel hybrid approach to accurately reconstruct 3D muscle fascicles using freehand ultrasound data in a coordinate system anchored by the muscle's central aponeurosis.

This method combines Hessian-based fascicle detection with wavelet-based refinement to generate precise volumetric fascicle orientations.

In a controlled synthetic dataset with pre-determined ground truth, the researchers were able to estimate fascicle orientations and lengths with high accuracy, within 2 degrees and approximately 1.5% respectively. When tested on living subjects, this technique successfully identified the expected fascicle lengthening in the human tibialis anterior following passive plantar flexion rotation, a movement that is not detected by traditional diffusion tensor imaging of the same muscle.

The proposed hybrid fascicle tractography technique offers a practical, non-invasive, and anatomically relevant solution for quantifying 3D muscle architecture in vivo, paving the way for important advancements in both clinical and applied muscle physiology research.