Computer-assisted analysis of human upper arm flexion by 4D-visualization based on MRI

Purpose 4D-visualization of the human upper arm based on sequential or dynamic MRI may be useful in functional orthopedic disorders and surgical planning. A cascade of 4D-visualization approaches have been applied including deformation of the soft tissue surfaces and muscular contraction. Skeletal structures and the epifascial tissue comprising vascular structures are included in the 4D-visualization. Methods Sequential MRI (T2-weighted spin echo sequences) scans of a healthy volunteer's upper extremity were obtained. The skeletal, muscular, and epifascial tissues were segmented. For 4D-rendering of the elbow joint, surface models of the humerus, the ulna, and the radius, were displaced with respect to the movement. For 4D-visualization of the soft tissue, the processed MRI data were subjected to highly transparent direct volume rendering with special two-tone transfer functions designed with regard to the application, e.g., muscular inner structure or fasciae. For rendering of time dependent behavior, the visualization was continuously updated. Results Continuous deformation of muscular inner structure and fasciae, and dynamics of muscle fibers could be differentiated in 4D-visualizations of the upper extremity. Using sequential MRI scans, this work was constrained by the high sagittal slice thickness and separation. Conclusion 4D-visualization of the upper extremity based on sequential MRI is feasible and provides a realistic appearance in comparison with anatomical drawings and preparations. The 4D-visualization method may be useful for detecting and monitoring muscular pathologies and lesions.