Figure 2From: Accuracy of biplane x-ray imaging combined with model-based tracking for measuring in-vivo patellofemoral joint motionSingle-frame model-based tracking solution for the femur (top) and patella (bottom). In each image, the two digitally reconstructed radiographs (DRRs) – i.e., the highlighted bones in each image – are superimposed over the original biplane x-ray images in the position and orientation that maximized the correlation between the DRRs and biplane images.Back to article page