Macroscopic muscular modeling based on in vivo 4D-radiology

Due to muscular deformation and movement, standard radiology provides only a snapshot of a probably never recurring situation. The scope of this project is dynamic rendering of muscular structures, starting from 4D-radiology, namely 3D+time, to macroscopic visualization and simulation based thereon. As full real time 4D-MRI is still beyond the technical possibilities for most human muscles, we follow kind of multi level approach. The first step is the analysis of muscular tissue of cadaveric preparations where validation can be performed by direct comparison. Secondly, nearly static, but living muscular tissue is studied based on standard 3DMRI. The first step towards time dependency are ex post composed series of static MRI where the muscle goes back to relaxed position between the acquisition steps. This is followed by so called “quasi-continuous” acquisition where, though not real time, the muscle does not go back to its original state, however remains in stretched position during acquisition. The final goal is full real time data acquisition. The radiological acquisition is followed by highly detailed image processing, segmentation, and visualization where the deforming muscular tissue is subjected to direct volume rendering with special transfer functions. The applied methods are demonstrated for the flexion of a human ankle joint and deforming human upper arm musculature. The visualization techniques proved to be well suited for capturing dynamics, but additional radiological research is strongly needed. The area of application of 4D-modeling ranges from biomechanics to medical diagnosis and therapy of muscular disorders. Key words: 4D-visualization, dynamic MRI, sequential MRI, upper arm musculature, ankle joint flexion, lower leg musculature, biceps brachii muscle, gastrocnemius muscle, direct volume rendering, 3D-reconstructio