A study on the positioning accuracy of patient positioning based on Optical Positioning System for nasopharyngeal carcinoma: Compared with conventional method

Purpose: The positioning accuracy of cancer center is an important factor for radiotherapy effect. The purpose of this study is to investigate the accuracy of patient positioning with Optical Positioning System(OPS) developed by Nanjing University in China, and show its superiority on positioning accuracy, compared with conventional method. Materials and Methods: 20 patients with nasopharyngeal carcinoma picked randomly were investigated. Before treatment, all received patient positioning with conventional method, and OPS´s function of tracking and positioning was triggered in the meantime. After patient positioning using conventional method was finished, the three positioning errors along three directions displayed on OPS were observed. If error along any direction was greater than 1.0mm, every step of patient positioning was checked to find error source. Results: In 20 clinical datasets, 15 datasets needed to be checked to find error source. Results showed that the difference of positioning results between conventional method and OPS-guided positioning method came from error source introduced in conventional method basically. And, about 66% positioning error comes from the manual operation error introduced in conventional method. Conclusion: This study indicates that OPS can eliminate the effect of almost manual error source introduced in conventional method basically and improve positioning accuracy of 2-5mm for patients with nasopharyngeal carcinoma.