Abstract

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Title:: Positioning accuracy and dose accuracy in radiotherapy using a novel positioner for thermoplastic immobilization

Author(s):: ZHU Yuanhu1; 2; SHE Guangnan3; WANG Xuetao2; TAN Xiang2; ZHU Lin2; HE Qiang2; JIAN Wanwei2; ZHANG Bailin2; MENG Haoyu2; ZHEN Xin1; 1. School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China 2. Department of Radiation Therapy, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China 3. Department of Digital Hospital Construction, The Sixth Affiliated Hospital, Sun Yat-sen University, Guangzhou 510655, China

Abstract:: Abstract: Objective To investigate the differences in positioning time, positional accuracy, and dose accuracy between the use and non-use of thermoplastic film positioners in radiotherapy immobilization. Methods Three patients requiring thermoplastic immobilization for radiotherapy were enrolled, with half of the treatments using a thermoplastic film positioner and the other half without. The positioning time, three-dimensional directional positioning errors after MVCT scanning matching, three-dimensional spatial vector displacement errors, and dose accuracy errors were recorded. The PTV margin was calculated using 2.5∑+0.7σ. Results The errors of no-positioner group and positioner group were 6.90 (2.85, 12.10) mm versus 2.60 (1.45, 8.10) mm in the X-axis direction (P=0.007), 9.30 (4.05, 16.15) mm versus 5.00 (2.60, 9.50) mm in the Y-axis direction (P=0.002), 3.40 (2.05, 4.10) mm versus 1.90 (1.30, 3.65) mm in the Z-axis direction (P=0.017), respectively. The PTV margins in the X, Y and Z axes were 9.15, 14.62, 2.15 mm in no-positioner group, and 6.50, 7.04, 2.97 mm in positioner group, respectively. Conclusion The application of positioners in thermoplastic immobilization can reduce the three-dimensional spatial positioning errors and minimize PTV margin.