Detection and Evaluation on the Accuracy of Fiducial Tracking with Spine Auxiliary Positioning during IGRT Treatment

With spine auxiliary positioning during IGRT treatment, utilize the simulated human phantom and dynamic lung phantom to detect the accuracy of fiducial tracking, and evaluate the value of it. Utilize CT to scan the phantoms which contain films, and design plans for phantoms and spine auxiliary positioning which use 1, 2, 3, 4, 5 and 6 fiducials for tracking, respectively. Each phantom plan shall be repeatedly implemented 3 times. The E2E software is used to analyze the accuracy of irradiation and then the average value is acquired. The results of detecting the simulated human phantom: the accuracy of irradiation with 1 and 2 fiducials for tracking (combining with spine auxiliary positioning) was 1.11 mm and 1.05 mm; with 3, 4, 5 and 6 fiducials, the accuracy was 1.07 mm, 0.92 mm, 0.97 mm and 1.15 mm, respectively. The results of detecting dynamic lung phantom: with 1 and 2 fiducials used for tracking (combining with spine auxiliary positioning), the accuracy of irradiation was 1.03 mm and 0.70 mm; with 3, 4, 5 and 6 fiducials, the accuracy was 0.58 mm, 1.02 mm, 0.65 mm and 0.96 mm, respectively. For the relatively static tumor or moving tumor, if the rotation direction of tumor is consistent with spine, the accuracy of using 1 or 2 fiducials for tracking was the same as using 3 to 6 fiducials. When the number of fiducials is not enough, fiducial tracking along with spine auxiliary positioning can well solve this problem.