Development of a three-dimensional anthropometry system for human body composition assessment
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The prevalence of obesity has made it necessary to develop a convenient, reliable and safe tool for timely assessing and monitoring this condition in public health. We suggest that three-dimensional (3D) anthropometry can provide a convenient, accommodating and comprehensive means to body composition assessment. A 3D anthropometry system based on stereo vision technology is developed. To make it more portable and affordable, the system is reduced to a two-stance design and only uses off-the-shelf components. The system is calibrated in two separate stages: camera calibration and 3D registration. The first stage is relatively complicated, but there is no need to repeat frequently. Therefore, only 3D registration is required when the system is transported. This property contributes to the portability and also reduces cost of maintenance. In this system, image acquisition can be completed in 200 ms, which is important in reducing artifacts caused by slight body movement. However, the computation in stereo vision is complex and intensive, and is still a challenge. A two-phase stereo matching algorithm is developed. In the first phase, the foreground is accurately segmented with the help of a predefined virtual interface, and a coarse disparity map is generated with block matching. In the second phase, local least squares matching is performed in combination with global optimization within a regularization framework, so as to ensure both accuracy and reliability. To make the 3D data more interpretable and manageable, it is essential to convert the raw 3D data to a surface model. For our system, a unique challenge is that there are large gaps in the data caused by occlusions. An effective surface reconstruction algorithm based on subdivision surface representation is developed. It has been verified that the algorithm is reliable in gap closing, accurate in representation, and efficient in data compression. To make the 3D anthropometry system ready for practical use, a body measurement system dedicated to body composition assessment is developed based on an earlier system that was designed for applications in apparel fitting. The functions of 3D measurement are enhanced by taking advantage of modern graphics hardware. The overall performance of the presented system has been evaluated on mannequins and human subjects. It has been shown that the measurements are highly repeatable. The feasibility of 3D anthropometry in body fat assessment has been demonstrated in comparison to air displacement plethysmography and bioimpedance analysis.