Repeated positioning in accurate radiotherapy based on virtual net technique and contrary reconstruction scheme

This paper presents a new repeated positioning system for external radiotherapy. A new scheme is proposed to rebuild patient's body surface 3-D image based on simple stereo vision model and virtual net technique, which improves the reconstruction precision of the template. For the calculation of the positioning error, the contrary reconstruction scheme is adopted and the positioning speed is greatly improved. The 3-D reconstructed video image of the right position in the first positioning is used as the reference template for the next positioning, and the positioning error is evaluated by projecting the template image into the patient's real-time video images and calculating the correlation ratio in the areas limited by the triangle of the reference image.