2024-03-28T14:53:02Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/507552022-11-17T02:08:08Zhdl_2115_20040hdl_2115_121Use of Implanted Markers and Interportal Adjustment With Real-Time Tracking Radiotherapy System to Reduce Intrafraction Prostate MotionShimizu, ShinichiOsaka, YasuhiroShinohara, NobuoSazawa, AtaruNishioka, KentaroSuzuki, RyusukeOnimaru, RikiyaShirato, HirokiRadiotherapyProstateIntrafraction organ motionImage-guided radiotherapy492Purpose: Interportal adjustment was applied to patients with prostate cancer using three fiducial markers and two sets of fluoroscopy in a real-time tumor-tracking radiotherapy (RTRT) system. The incidence of table position adjustment required to keep intrafractional uncertainty within 2.0 mm was investigated in this study. Methods and Materials: The coordinates of the center of gravity of the three fiducial markers were measured at the start of every portal irradiation in intensity-modulated radiotherapy (IMRT) with seven ports. The table position was adjusted to the planned position if the discrepancy was larger than 2.0 mm in the anterior-posterior (AP), cranial-caudal (CC), or left-right (LR) directions. In total, we analyzed 4541 observations in 20 patients who received 70 Gy in 30 fractions (7.6 times a day in average). Results: The incidence of table position adjustment at 10 minutes from the initial set-up of each treatment was 14.2%, 12.3%, and 5.0% of the observations in the AP, CC, and LR directions, respectively. The accumulated incidence of the table position adjustment was significantly higher at 10 minutes compared to that at 2 minutes for AP (p = 0.0033) and CC (p = 0.0110) but not LR (p = 0.4296). An adjustment greater than 5 mm was required at least once in the treatment period in 11 (55%) patients. Conclusions: Interportal adjustment of table position was required in more than 10% of portal irradiations during the 10-minute period after initial setup to maintain treatment accuracy within 2.0 mm.ElsevierJournal Articleapplication/pdfhttp://hdl.handle.net/2115/50755https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/50755/1/IJROBP81-4_e393-e399.pdf0360-3016International Journal of Radiation Oncology*Biology*Physics814e393e3992011-11-15enginfo:pmid/21658857info:doi/10.1016/j.ijrobp.2011.04.043author