Study of dose distortion and Bragg peak location correction in MRI-guided proton therapy
Deng Xiuzhen1,2, Li Xiufang3, Guo Mengya1,2, Gu Shuaizhe1,2, Liu Qi1,2, Chen Zhiling1,4
1Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China; 2University of Chinese Academy of Sciences, Beijing 100049, China; 3Shanghai APACTRON Particle Equipment Co., Ltd, Shanghai 201800, China; 4Shanghai Advanced Research Institute Chinese Academy of Sciences, Shanghai 201210, China
Abstract：Objective To analyze the influence of magnetic field on the proton beam delivery and dose distribution, and develop a correction method for the Bragg peak (BP) shift under the vertical magnetic field, providing reference for the dose calculation and beam delivery of MRI-guided proton therapy. Methods Monte Carlo (MC) simulation was used to study the dose distribution of the proton beam in the water phantom under the magnetic field. The BP location was corrected by the method of"angle correction+ energy correction", and the correction parameters were calculated by the analytical formula based on the simulation data. Results The magnetic field caused the dose distortion and shift of BP location. The shift degree was increased with the increase of field strength and initial energy. Compared with MC simulation, the result of calculating proton deflection in the air by the analytical method yielded a deviation within 0.2%. Based on the simulation data and calculation formulas, the correction parameters under different conditions could be calculated within 1s by using the MATLAB programming. The calculation results showed that the air layer with magnetic field, isocenter depth, irradiation direction exerted different influence on the correction parameters. After correction, the BP location was basically consistent with the expected (offset ≤0.2mm). Conclusions The BP shift under the vertical magnetic field can be effectively corrected by "the angle correction+ energy correction" method. The correction parameters under different conditions can be quickly and accurately calculated by the calculation formulas based on simulation data.
Deng Xiuzhen,Li Xiufang,Guo Mengya et al. Study of dose distortion and Bragg peak location correction in MRI-guided proton therapy[J]. Chinese Journal of Radiation Oncology, 2022, 31(2): 176-181.
[1] Suit H, Goldberg S, Niemierko A, et al. Proton beams to replace photon beams in radical dose treatments[J]. Acta Oncol, 2003, 42(8):800-808. DOI:10.1080/02841860310017676. [2] Barten DLJ, Tol JP, Dahele M, et al. Comparison of organ-at-risk sparing and plan robustness for spot-scanning proton therapy and volumetric modulated arc photon therapy in head-and-neck cancer[J]. Med Phys, 2015, 42(11):6589-6598. DOI:10.1118/1.4933245. [3] Meier G, Besson R, Nanz A, et al. Independent dose calculations for commissioning, quality assurance and dose reconstruction of PBS proton therapy[J]. Phys Med Biol, 2015, 60(7):2819-2836. DOI:10.1088/0031-9155/60/7/2819. [4] Liu P, Dong B, Nguyen DT, et al. First experimental investigation of simultaneously tracking two independently moving targets on an MRI-linac using real-time MRI and MLC tracking[J]. Med Phys, 2020, 47(12):6440-6449. DOI:10.1002/mp.14536. [5] Keall PJ, Barton M, Crozier S. The Australian magnetic resonance imaging-Linac program[J]. SeminRadiat Oncol, 2014, 24(3):203-206. DOI:10.1016/j.semradonc.2014.02.015. [6] Fallone BG. The rotating biplanar Linac-magnetic resonance imaging system[J]. SeminRadiat Oncol, 2014, 24(3):200-202. DOI:10.1016/j.semradonc.2014.02.011. [7] Hoffmann A, Oborn B, Moteabbed M, et al. MR-guided proton therapy:a review and a preview[J]. Radiat Oncol, 2020, 15(1):129-142. DOI:10.1186/s13014-020-01571-x. [8] Oborn BM, Dowdell S, Metcalfe PE, et al. Proton beam deflection in MRI fields:implications for MRI-guided proton therapy[J]. Med Phys, 2015, 42(5):2113-2124. DOI:10.1118/1.4916661. [9] Burigo LN, Oborn BM. MRI-guided proton therapy planning:accounting for an inline MRI fringe field[J]. Phys Med Biol, 2019, 64(21):215015. DOI:10.1088/1361-6560/ab436a. [10] 阳露,刘红冬,陈志,等. 基于TOPAS计算的磁场下质子辐射剂量分析[J]. 中国医学物理学杂志,2017, 34(3):217-224. DOI:10.3969/j.issn.1005-202X.2017.03.001. Yang L, Liu HD, Chen Z, et al. Analysis of proton radiation dose in magnetic field based on TOPAS calculation[J]. Chin J Med Phys, 2017, 34(3):217-224. DOI:10.3969/j.issn.1005-202X.2017.03.001. [11] Fuchs H, Moser P, Grschl M, et al. Magnetic field effects on particle beams and their implications for dose calculation in MR-guided particle therapy[J]. Med Phys, 2017, 44(3):1149-1156. DOI:10.1002/mp.12105. [12] Wolf R, Bortfeld T. An analytical solution to proton Bragg peak deflection in a magnetic field[J]. Phys Med Biol, 2012, 57(17):329-337. DOI:10.1088/0031-9155/57/17/N329. [13] Allison J, Amako K, Apostolakis J, et al. Geant4 developments and applications[J]. IEEE Trans Nucl Sci, 2006, 53(1):270-278. DOI:10.1109/TNS.2006.869826. [14] Hartman J, Kontaxis C, Bol GH, et al. Dosimetric feasibility of intensity modulated proton therapy in a transverse magnetic field of 1.5 T[J]. Phys Med Biol, 2015, 115(15):S79-S80. DOI:10.1016/S0167-8140(15)40160-4.
2022, Vol. 31 
