The Validation of Hand Volume Measured by 3D Laser Scan
Hand volume is a useful evaluation for the situation of recovery process in many clinical treatments. Measuring methods of hand volume include the easy and fast yet inaccurate and imprecise ones, e.g. circumference measurements and figure-of-eight method; and the relatively accurate and precise yet expensive, not portable or even invasive ones, e.g. magnetic resonance imaging, bioelectrical impedance and perometer. Water volumetry is considered a golden method in this field. It is easy, fast, effective and portable; however, the accuracy and precision are limited by the operation of the experimenters, the position and posture of the measured hand, and the quality of the graduated cylinders. Additionally, it is inexecutable if trauma occurring on target hand. Measuring hand volume using 3D laser scan is comparably a medium option within all conflicting advantages and disadvantages. It is fast, easy in operation, relatively inexpensive, not invasive, and executable if trauma occurring on target hand.
This study aimed to validate the measurement of hand volume using 3D laser scan technologies. First, the 3D surface shape of hands was measured by a laser scan system with resolution of 1 mm × 1 mm × 1 mm and precision of ± 0.4 mm. About three seconds, a target hand was scanned and duplicated into a digital hand, which comprised about forty thousand 3D coordinates. And the hand volume was then calculated by software algorithm immediately. Second, the precision was analyzed by measuring the volume of a subject’s right hand five times using both laser scan and water volumetry by one experimenter. The standard error of the five repeated measurements was analyzed. Third, take the mean of five measurements of water volumetry as a base;the laser scan accuracy was analyzed by calculating the error of scan measurement. Another validation of the accuracy of laser scan was by measuring the volume of the right hand of five subjects by one experimenter and taking the result of water volumetry as a base to calculate the error of scan measure. These analyses were all performed for three hand postures. The resulted errors of precision and accuracy were tabulated for reference.
Keywords— Hand volume, 3D laser scan, Precision, Accuracy.