Abstract：Objective To evaluate the effects of orthogonal magnetic fields on the dose distribution of 6MeV X-ray in a uniform water and heterogeneous phantoms. Methods The Monte Carlo simulation software Gate v8.2 was used to investigate the dose distribution of X-ray beams of different field sizes in a uniform water phantom, water-air/bone-water layer phantom and"custom lung model" in the magnetic field strength of 0.0, 0.5, 1.0, 1.5, 3.0 T, respectively. The relationship between the intensity of magnetic field and the dose distribution of X-rays in the phantoms was analyzed. Results The existence of a magnetic field would cause the X-ray to shorten the built-up area in the water phantom;when the field was 10cm×10cm, the maximum dose on the central axis could change by up to 56.22%(3.0 T). The transverse dose distribution of the radiation field in the direction of the vertical magnetic field shifted to one side by up to 43.64%(-44.55%). The average dose of the air layer in the water-air-water phantom could be reduced by 57.4%(3.0 T). In the water-bone-water phantom, the dose at the proximal end of the bone layer was decreased by 16.5%, whereas the dose at the distal end was increased by 22.6%(1.5 T). The dose change in each layer in the customed lung model was positively correlated with the magnetic field strength. Conclusion The existence of the orthogonal magnetic field will cause the change of X-ray dose distribution on the built-up area and both sides of the radiation field in the phantoms, which is more obvious adjacent to the interface of heterogeneous phantom.
Hu Birong,Meng Qianqian,Zhong Renming. Dosimetric study of 6MeV X-ray in different phantoms in a magnetic field[J]. Chinese Journal of Radiation Oncology, 2022, 31(6): 544-549.
[1] Winkel D, Bol GH, Kroon PS, et al. Adaptive radiotherapy:the Elekta unity MR-Linac concept[J]. Clin Transl Radiat Oncol, 2019, 18:54-59. DOI:10.1016/j.ctro.2019.04.001.
[2] KLÜter S. Technical design and concept of a 0.35 T MR-Linac[J]. Clin Transl Radiat Oncol, 2019, 18:98-101. DOI:10.1016/j.ctro.2019.04.007.
[3] Raaymakers BW, Jürgenliemk-Schulz IM, Bol GH, et al. First patients treated with a 1.5 T MRI-Linac:clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment[J]. Phys Med Biol, 2017, 62(23):L41-L50. DOI:10.1088/1361-6560/aa9517.
[4] Chen X, Paulson ES, Ahunbay E, et al. Measurement validation of treatment planning for a MR-Linac[J]. J Appl Clin Med Phys, 2019, 20(7):28-38. DOI:10.1002/acm2.12651.
[5] 王春燕, 刘漪, 曲典, 等. 三维水箱模体中辐射剂量分布的模拟研究[J]. 核电子学与探测技术, 2009, 29(2):309-311, 441. DOI:10.3969/j.issn.0258-0934.2009.02.018.
Wang CY, Liu Y, Qu D, et al. Simulation calculation for the distribution of radiation dosage in water[J]. Nucl Electronic Detect Technol,2009,29(2):309-311, 441. DOI:10.3969/j.issn.0258-0934.2009.02.018.
[6] 冯宁远. 实用放射治疗物理学[M]. 北京:北京医科大学中国协和医科大学联合出版社,1998:227.
Feng NY. Practical radiation therapy physics[M]. Beijing:Joint Publishing House of Peking Medical College and Peking Union Medical College,1998:227.
[7] 蓝澄云. BJ-6B型加速器手工测量PDD与三维水箱测量PDD的对比分析[J]. 中华放射医学与防护杂志, 2005, 25(1):64. DOI:10.3760/cma.j.issn.0254-5098.2005.01.042.
Lan CY. Comparative analysis of PDD measured manually with BJ-6B accelerator and measured with 3d water tank[J]. Chin J Radiol Med Protect, 2005, 25(1):64. DOI:10.3760/cma.j.issn.0254-5098.2005.01.042.
[8] 王春燕, 刘漪, 刘云鹏, 等. 基于Monte Carlo方法的放射治疗剂量分布计算方法的研究[J]. 医疗设备信息, 2007(04):8-10.
Wang CY, Liu Y, Liu YP, et al. Research on calculation method of radiation therapy dose distribution based on Monte Carlo method[J]. China Med Devic, 2007(04):8-10.
[9] Raaijmakers AJ, Raaymakers BW, Lagendijk JJ. Experimental verification of magnetic field dose effects for the MRI-accelerator[J]. Phys Med Biol, 2007, 52(14):4283-4291. DOI:10.1088/0031-9155/52/14/017.
[10] Jan S, Benoit D, Becheva E, et al. GATE v6:a major enhancement of the GATE simulation platform enabling modelling of CT and radiotherapy[J]. Phys Med Biol, 2011, 56(4):881-901. DOI:10.1088/0031-9155/56/4/001.
[11] Rubinstein AE, Liao Z, Melancon AD, et al. Technical note:A Monte Carlo study of magnetic-field-induced radiation dose effects in mice[J]. Med Phys, 2015, 42(9):5510-5516. DOI:10.1118/1.4928600.
[12] Kirkby C, Stanescu T, Rathee S, et al. Patient dosimetry for hybrid MRI-radiotherapy systems[J]. Med Phys, 2008, 35(3):1019-1027. DOI:10.1118/1.2839104.
[13] Bilal AS, Arman S, Raj PM, et al. Evaluation of a commercial MRI Linac based Monte Carlo dose calculation algorithm with geant 4[J]. Med Phys, 2016. DOI:10.1118/1.4939808.
[14] 阳露. 利用蒙特卡罗软件TOPAS研究MRIgRT中磁场对多粒子辐射剂量的影响[D]. 合肥:中国科学技术大学,2018.
Yang L. Using Monte Carlo software TOPAS to study the effect of magnetic field on multi-particle radiation dose in MRIgRT[D]. Hefei:University of Science and Technology of China, 2018.
[15] Zhang Y, Yan S, Cui Z, et al. Out-of-field dose assessment for a 1.5 T MR-Linac with optically stimulated luminescence dosimeters[J]. Med Phys, 2021, 48(7):4027-4037. DOI:10.1002/mp.14839.
[16] Xia W, Zhang K, Li M, et al. Corrigendum:impact of magnetic field on dose distribution in MR-guided radiotherapy of head and neck cancer[J]. Front Oncol, 2020, 10:604231. DOI:10.3389/fonc.2020.604231.
[17] Costa F, Doran SJ, Hanson IM, et al. Investigating the effect of a magnetic field on dose distributions at phantom-air interfaces using PRESAGE® 3D dosimeter and Monte Carlo simulations[J]. Phys Med Biol, 2018, 63(5):05NT01. DOI:10.1088/1361-6560/aaaca2.
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