Proposal of a Marker-less Registration Method for Measuring Changes in Daily Swelling of the Foot of Individuals with...

Individuals with spinal cord injury may face difficulties in perceiving their physical condition due to somatosensory deficits. In a previous study, we identified a potential correlation between leg swelling in individuals with spinal cord injury and their underlying physical condition. In this study, we propose a methodology for quantifying changes in daily leg swelling in individuals with spinal cord injury. This methodology involves the calculation of the volume of three-dimensional (3D) scan data obtained from a 3D scanner. Several 3D scanning methods have been proposed to measure foot swelling, but these methods require trimming marks on the skin of the measurement area, making long-term measurement and comparison difficult. In contrast, we developed a method of extracting the same area without trimming marks by aligning multiple scan data based on shape features and cutting them in the same plane. A prerequisite for the comparison of 3D data is registration, which involves the transformation of data from disparate coordinate systems into a unified one, ensuring the alignment of their postures. In order to apply the iterative closest point (ICP) algorithm, a frequently utilized registration method, to the registration of deforming foot data, a partial ICP method is proposed. This method involves the extraction of only the bony process of the foot for registration. The efficacy of this approach is then demonstrated through a comparative analysis with conventional registration methods. Finally, a comparison was made between the volume of the foot as determined by the proposed method and the volume of the foot as measured by the gold standard water displacement (WD) method. The results of this comparison demonstrated that the performance of the proposed method is equivalent to that of the WD method.