The use of Roentgenstereofluorogrammetry to predict the 3-D spatial coordinates of points in low speed events

Imaging technologies such as cine-radiography, cine-MRI, and X-ray stereo photogrammetry have become popular diagnostic tools in biomechanical studies of musculoskeletal systems. However, their widespread use for research purposes has been restricted due to their high cost and somewhat limited availability. In an attempt to develop a reliable low cost system, a dual-fluoroscopic system capable of tracking the 3-D spatial motion of discrete landmark points in real time was developed. A simple methodology was developed to convert the analog fluoroscopic images to digital files for post-processing. A custom computer code based on the principles of X-ray stereo photogrammetry was also developed to predict 3-D coordinates from the 2-D images from the individual flouroscopes. The goal of the current study was to assess the accuracy and resolution of this system by using it to predict the motion of a test point following a known curvilinear trajectory. Our system predicted the time-varying motion and path of the test point within 0.25%. However, the current system is limited to studying low speed events only (max event frequency of 3 Hz) due to the limited sampling frequency of the A/D conversion employed here.