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经IAEA-483报告修正前后高能光子束小野输出因子与蒙特卡罗模拟对比分析研究
肖振华, 王振宇, 欧阳斌, 文碧秀
中山大学附属第一医院放射治疗科,广州 510080
Comparative analysis of output factor of high-energy photon small field between measurements with or without correction of IAEA-483 report and Monte-Carlo simulation
Xiao Zhenhua, Wang Zhenyu, Ouyang Bin, Wen Bixiu
Department of Radiation Oncology, the First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China
Abstract：Objective To evaluate the accuracy of measurement of the output factor of high-energy photon small field (Scp) using commercial semi-diodes and ionization chambers in small fields in accordance with the IAEA-483 report, which has been proposed that all kinds of detectors should be revised for small field Scp measurement in clinical practice. Methods EGSnrc of Monte Carlo (MC) software was utilized to simulate the treatment head of Varian Novalis Tx linear accelerator, and the profile curve and relative dose value were generated by simulation in DOSXYZnrc based on derived phase space file. Measurement of PDD and Profiles was used to adjust and validate the simulation mode. Detectors including ionization chambers A16, A14sL,CC01,CC13, PFD and EFD and semi-diodes PFD, EFD and Razor under different radiation field settings (0.5cm to 10.0cm) were employed to measure the profile curves and Scp of FWHM equivalent rectangular fields, which were compared with data of Monte-Carlo simulation. The measurement of Scp was revised by data given in the IAEA-483 report. The data with or without correction were compared with the data of MC simulation. Results A curve deviation oF<2.0% between MC simulation and PFD measurement was accepted. MC simulated Profiles were consistent with PFD, EFD and Razor measurements, when the field was<3.0cm. Razor response in the out-field region was 2.3% higher than those of MC and PFD, and it increased with the increment of field and was 3.0% at 10.0cm. The maximum 20.0%-80.0% penumbra width was detected as 3.0 mm for CC13 at 10.0cm rectangular field. With the decrease of the radiation field, the deviation relative to MC simulation was increased as for Scp mean values of 7detectors before correction. The standard deviation (SD) of the measured value was increased rapidly when it was close to 1.0cm, ranging from 0.009-0.014 for the field of 5.0cm-1.5cm to 0.030-0.089 for the field of 1.0cm-0.5cm. The mean value of SD for the whole measurement before correction was 0.030. The mean SD of Scp measured by the six probes was 0.008, 0.013 at 0.8cm and 0.021 at 0.6cm after correction. When the equivalent field was ≥1.0cm, the corrected Scp and MC simulation deviation was ranged from -3.6% to -0.5%. The error was between -6.9% and -1.3% when the radiation field was<1.0cm. Conclusion The SD of Scp measured by different detectors after correction in accordance to the IAEA-483 report is small, which is in good agreement with the data of MC simulation, suggesting that it could be applied in clinical dosimetry.
Xiao Zhenhua,Wang Zhenyu,Ouyang Bin et al. Comparative analysis of output factor of high-energy photon small field between measurements with or without correction of IAEA-483 report and Monte-Carlo simulation[J]. Chinese Journal of Radiation Oncology, 2021, 30(12): 1280-1285.
[1] Crop F, Reynaert N, Pittomvils G, et al. The influence of small field sizes, penumbra, spot size and measurement depth on perturbation factors for microionization chambers[J]. Phys Med Biol, 2009, 54(9):2951-2969. DOI:10.1088/0031-9155/54/9/024. [2] Dieterich S, Sherouse GW. Experimental comparison of seven commercial dosimetry diodes for measurement of stereotactic radiosurgery cone factors[J]. Med Phys, 2011, 38(7):4166-4173. DOI:10.1118/1.3592647. [3] Chen F, Graeff CF, Baffa O. K-band EPR dosimetry:small-field beam profile determination with miniature alanine dosimeter[J]. Appl Radiat Isot, 2005, 62(2):267-271. DOI:10.1016/j.apradiso.2004.08.036. [4] Calcina CS, de Oliveira LN, de Almeida CE, et al. Dosimetric parameters for small field sizes using Fricke xylenol gel, thermoluminescent and film dosimeters, and an ionization chamber[J]. Phys Med Biol, 2007, 52(5):1431-1439. DOI:10.1088/0031-9155/52/5/014. [5] Zhang B, Zhu J, Li Y, et al. Feasibility of lateral dose profile measurements in a small field using TLDs[J]. Phys Med Biol, 2015, 60(3):N47-57. DOI:10.1088/0031-9155/60/3/N47. [6] Gagnon JC, Thériault D, Guillot M, et al. Dosimetric performance and array assessment of plastic scintillation detectors for stereotactic radiosurgery quality assurance[J]. Med Phys, 2012, 39(1):429-436. DOI:10.1118/1.3666765. [7] Hardcastle N, Basavatia A, Bayliss A, et al. High dose per fraction dosimetry of small fields with gafchromic EBT2 film[J]. Med Phys, 2011, 38(7):4081-4085. DOI:10.1118/1.3597834. [8] Palmans H, Andreo P, Huq M S, et al. Dosimetry of small static fields used in external photon beam radiotherapy:Summary of TRS-483, the IAEA-AAPM international Code of Practice for reference and relative dose determination[J]. Medl Phys, 2018, 45(11):e1123-e1145. DOI:10.1002/mp.13208. [9] Rogers DW, Faddegon BA, Ding GX, et al. BEAM:a Monte Carlo code to simulate radiotherapy treatment units[J]. Med Phys, 1995, 22(5):503-524. DOI:10.1118/1.597552. [10] Popescu IA, Shaw CP, Zavgorodni SF, et al. Absolute dose calculations for Monte Carlo simulations of radiotherapy beams[J]. Phys Med Biol, 2005, 50(14):3375-3392. DOI:10.1088/0031-9155/50/14/013. [11] 岳海振,张艺宝,胡俏俏,等.6MV光子束均整与非均整模式蒙特卡罗模型的绝对剂量刻度与输出因子模拟[J]. 中华放射医学与防护杂志,2017, 37(1):29-34. DOI:10.3760/cma.j.issn.0254-5098.2017.01.006. Yue HZ, Zhang YB, Hu QQ, et al. 6 Absolute dose scale and output factor simulation of the MV photon beam homogeneous and heterogeneous mode Monte Carlo model[J]. Chin J Radiol Med Protect, 2017, 37(1):29-34. DOI:10.3760/cma.j.issn.0254-5098.2017.01.006. [12] Sheikh-Bagheri D, Rogers DW. Sensitivity of megavoltage photon beam Monte Carlo simulations to electron beam and other parameters[J]. Med Phys, 2002, 29(3):379-390. DOI:10.1118/1.1446109. [13] Sham E, Seuntjens J, Devic S, et al. Influence of focal spot on characteristics of very small diameter radiosurgical beams[J]. Med Phys, 2008, 35(7):3317-3330. DOI:10.1118/1.2936335. [14] Ding GX, Duggan DM, Coffey CW.commissioning stereotactic radiosurgery beams using both experimental and theoretical methods[J]. Phys Med Biol, 2006, 51(10):2549-2566. DOI:10.1088/0031-9155/51/10/013. [15] 李明辉,马攀,田源,等. 基于IAEA483号报告的小野射野输出因子测量及修正方法[J]. 中华放射肿瘤学杂志,2019, 28(6):452-456. DOI:10.3760/cma.j.issn.1004-4221.2019.06.013. Li MH, Ma P, Tian Y, et al. Measurement and correction method based on the IAEA483 report[J]. Chin J Radiat Oncol, 2019, 28(6):452-456. DOI:10.3760/cma.j.issn.1004-4221.2019.06.013. [16] Azangwe G, Grochowska P, Georg D, et al. Detector to detector corrections:a comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams[J]. Med Phys, 2014, 41(7):072103. DOI:10.1118/1.4883795. [17] Yin Z, Hugtenburg RP, Beddoe AH. Response corrections for solid-state detectors in megavoltage photon dosimetry[J]. Phys Med Biol, 2004, 49(16):3691-3702. DOI:10.1088/0031-9155/49/16/015. [18] Ding G X. Using Monte Carlo simulations to commission photon beam output factors—a feasibility study[J]. Phys Med Biol, 2003, 48(23):3865-3874. DOI:10.1088/0031-9155/48/23/005. [19] Chetty IJ, Curran B, Cygler JE, et al. Report of the AAPM Task Group No. 105:Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning[J]. Med Phys, 2007, 34(12):4818-4853. DOI:10.1118/1.2795842.
2021, Vol. 30 
