辐射自显影胶片用于调强放疗剂量验证的可行性研究
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摘要
本课题的主要目的是分析不同扫描光源下EBT2胶片的剂量响应特性,将由EBT2胶片、Uniscan C880平板扫描仪和FilmQA剂量分析软件组建的IMRT剂量验证系统应用于临床。
课题研究首先将EBT2胶片被放置于固体水模体中,使用6MV光子线照射胶片,照射的剂量范围为0—280cGy,通过将扫描后的胶片影像分离成红光、绿光和蓝光影像,来分析不同扫描光源下胶片的剂量响应特性;然后通过对扫描仪的扫描不确定性和扫描方向对扫描仪读数的影响进行测试以评估由EBT2胶片、Uniscan C880平板扫描仪和FilmQA剂量分析软件组成的IMRT剂量验证系统的性能,并将该系统应用于一例鼻咽癌病例的剂量验证,来认识和掌握该系统的使用方法;最后使用该系统和mapcheck半导体探测器阵列对10组IMRT照射野进行剂量验证,通过观察不同参数设置下DTA指数和Gamma指数的变化,来分析EBT2胶片在IMRT剂量学验证上的优点。
通过研究我们发现,EBT2胶片在红光扫描光源下的剂量响应灵敏度最高且其响应曲线是非线性的,使用三次多项式可以满足该剂量响应曲线的拟合要求。扫描仪的单次扫描不确定性和多次扫描不确定性分别是0.22%和1.12%,胶片放置方位对扫描仪读数影响很大。通过对一组鼻咽癌IMRT照射野的剂量验证,发现该系统使用方法简单,测量结果与计划计算数据基本一致。通过对比mapcheck获取的IMRT验证结果,发现EBT2胶片比mapcheck具有更高的空间分辨率,能够测量到更多剂量检验点上的剂量变化。
研究说明,基于辐射自显影胶片EBT2的IMRT剂量验证系统操作简单、结果准确,具有很高的空间分辨率,非常适合射野内剂量梯度变化大、准确性要求高的IMRT的剂量验证,值得在临床中推广应用。
The purpose of this study is to investigate the dose response characteristic of EBT2 film which is scanned with different light sources. Then the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 scanner and FilmQA dosimetry analysis software was applied in clinical.
The EBT2 film was placed in solid water phantom, radiated with 6MV photon beam whose delivered dose are span from 0 to 280 cGy. Then the film was scanned with flatbed color scanner, and the scanned images were separated into red, green and blue images. The characteristic of image’s dose response was analyzed respectively. The scanner’s scanning uncertainty and film orientation effect were tested to evaluate the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software. Then the system was applied in a NPC case in experimental trial as well. 10 cases were tested by this system and mapcheck, the results were analyzed with DTA and Gamma index. The advancement of EBT2 film in IMRT dosimetric verification was investigated by setting various parameters to DTA and Gamma index.
The results showed that sequence of dose response sensitivity of the EBT2 film is red, green and blue when scanned in different lights. Cubic polynomial fitting method can satisfy the requirement of dose response curve. The Uniscan C880 scanner’s single and multiple scanning uncertainties were 0.22% and 1.12% respectively. Film orientation had a big effect on scanner’s readout. The IMRT dosimetric verification system composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software was easy to use, and the results got from this system were accurate. Compared with mapcheck, EBT2 have a higher spatial resolution; can check out more spatial point’s dose difference.
The IMRT dosimetric verification system based on radiochromic film EBT2 is easy to use and can acquire an accurate result. Due to the advantages of high spatial resolution, it is suitable to use in IMRT dose verification and is valuable for clinical application.
课题研究首先将EBT2胶片被放置于固体水模体中,使用6MV光子线照射胶片,照射的剂量范围为0—280cGy,通过将扫描后的胶片影像分离成红光、绿光和蓝光影像,来分析不同扫描光源下胶片的剂量响应特性;然后通过对扫描仪的扫描不确定性和扫描方向对扫描仪读数的影响进行测试以评估由EBT2胶片、Uniscan C880平板扫描仪和FilmQA剂量分析软件组成的IMRT剂量验证系统的性能,并将该系统应用于一例鼻咽癌病例的剂量验证,来认识和掌握该系统的使用方法;最后使用该系统和mapcheck半导体探测器阵列对10组IMRT照射野进行剂量验证,通过观察不同参数设置下DTA指数和Gamma指数的变化,来分析EBT2胶片在IMRT剂量学验证上的优点。
通过研究我们发现,EBT2胶片在红光扫描光源下的剂量响应灵敏度最高且其响应曲线是非线性的,使用三次多项式可以满足该剂量响应曲线的拟合要求。扫描仪的单次扫描不确定性和多次扫描不确定性分别是0.22%和1.12%,胶片放置方位对扫描仪读数影响很大。通过对一组鼻咽癌IMRT照射野的剂量验证,发现该系统使用方法简单,测量结果与计划计算数据基本一致。通过对比mapcheck获取的IMRT验证结果,发现EBT2胶片比mapcheck具有更高的空间分辨率,能够测量到更多剂量检验点上的剂量变化。
研究说明,基于辐射自显影胶片EBT2的IMRT剂量验证系统操作简单、结果准确,具有很高的空间分辨率,非常适合射野内剂量梯度变化大、准确性要求高的IMRT的剂量验证,值得在临床中推广应用。
The purpose of this study is to investigate the dose response characteristic of EBT2 film which is scanned with different light sources. Then the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 scanner and FilmQA dosimetry analysis software was applied in clinical.
The EBT2 film was placed in solid water phantom, radiated with 6MV photon beam whose delivered dose are span from 0 to 280 cGy. Then the film was scanned with flatbed color scanner, and the scanned images were separated into red, green and blue images. The characteristic of image’s dose response was analyzed respectively. The scanner’s scanning uncertainty and film orientation effect were tested to evaluate the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software. Then the system was applied in a NPC case in experimental trial as well. 10 cases were tested by this system and mapcheck, the results were analyzed with DTA and Gamma index. The advancement of EBT2 film in IMRT dosimetric verification was investigated by setting various parameters to DTA and Gamma index.
The results showed that sequence of dose response sensitivity of the EBT2 film is red, green and blue when scanned in different lights. Cubic polynomial fitting method can satisfy the requirement of dose response curve. The Uniscan C880 scanner’s single and multiple scanning uncertainties were 0.22% and 1.12% respectively. Film orientation had a big effect on scanner’s readout. The IMRT dosimetric verification system composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software was easy to use, and the results got from this system were accurate. Compared with mapcheck, EBT2 have a higher spatial resolution; can check out more spatial point’s dose difference.
The IMRT dosimetric verification system based on radiochromic film EBT2 is easy to use and can acquire an accurate result. Due to the advantages of high spatial resolution, it is suitable to use in IMRT dose verification and is valuable for clinical application.
引文
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[2] Fogliata A, Vanetti E, Albers D, et al. On the dosimetric behaviour of photon dose calculation algorithms in the presence of simple geometric heterogeneities: comparison with Monte Carlo calculations. Phys. Med. Biol, 2007, 52(5): 1363– 1385.
[3]胡逸民,张红志,戴建荣.肿瘤放射物理学[M].北京:原子能出版社,1999: 613- 615.
[4] Jursinic PA, Nelms BE. A 2-D diode array and analysis software for verification of intensity modulated radiation therapy delivery. Med. Phys, 2003, 30(5): 870- 879.
[5] Létourneau D, Gulam M, Yan D, et al. Evaluation of a 2D diode array for IMRT quality assurance. Radiotherapy and oncology. 2004, 70(2): 199-206.
[6]沈国辉,余辉,张书旭,等.基于MatriXX调强放疗计划的剂量学验证.职业与健康, 2009, 25(13): 1348- 1350.
[7] Daniel A. Low, William B. Harms, Sasa Mutic,et,al. A technique for the quantitative evaluation of dose distributions[J] Med. Phys. 1998, 25(5): 656-661.
[8]戴建荣,胡逸民,张红志,等.针对患者调强放射治疗计划的剂量学验证.中华放射肿瘤学杂志.2004,13(3), 229- 232.
[9]马金利,蒋国梁,等.冲洗时间因素对胶片剂量的影响.中华放射肿瘤学杂志.2005, l4(6):514- 518.
[10]李勤,李光俊,韩军等.调强验证中胶片刻度方法的研究.中华放射肿瘤学杂志.2007, 16(5):384- 385.
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[13] Robar JL, Clark BG.The use of radiographic film for linear accelerator stereotactic radiosurgical dosimetry. Med. Phys, 1999, 26(10): 2144- 2150.
[14] Danciu C, Proimos BS, Rosenwald JC, et al. Variation of sensitometric curves of radiographic films in high energy photon beams. Med. Phys. 2001, 28(6): 966-974.
[15]周颖娟,黄劭敏,邓小武.辐射显色剂量胶片的特性及其在放射医学的应用.国际肿瘤学杂志,2007,34(1): 28- 30.
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[20]周颖娟,黄劭敏,邓小武.用放射性铬胶片进行调强放疗剂量验证的研究.中华放射肿瘤学杂志2007,16(4):307-312.
[21]高兴旺,祁振宇,张罗生,等.二维半导体探测器阵列与免洗放射性铬胶片在调强放射治疗计划剂量验证中的应用比较.中国肿瘤,2008,17(8):690-693.
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[25] Leybovich LB, Sethi A, Dogan N. Comparison of ionization chambers of various volumes for IMRT absolute dose verification. Med. Phys. 2003, 30(2): 119- 123.
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[28] Robar JL, Clark BG. The use of radiographic film for linear accelerator stereotactic radiosurgical dosimetry. Med. Phys, 1999, 26(10): 2144- 2150.
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[2] Fogliata A, Vanetti E, Albers D, et al. On the dosimetric behaviour of photon dose calculation algorithms in the presence of simple geometric heterogeneities: comparison with Monte Carlo calculations. Phys. Med. Biol, 2007, 52(5): 1363– 1385.
[3]胡逸民,张红志,戴建荣.肿瘤放射物理学[M].北京:原子能出版社,1999: 613- 615.
[4] Jursinic PA, Nelms BE. A 2-D diode array and analysis software for verification of intensity modulated radiation therapy delivery. Med. Phys, 2003, 30(5): 870- 879.
[5] Létourneau D, Gulam M, Yan D, et al. Evaluation of a 2D diode array for IMRT quality assurance. Radiotherapy and oncology. 2004, 70(2): 199-206.
[6]沈国辉,余辉,张书旭,等.基于MatriXX调强放疗计划的剂量学验证.职业与健康, 2009, 25(13): 1348- 1350.
[7] Daniel A. Low, William B. Harms, Sasa Mutic,et,al. A technique for the quantitative evaluation of dose distributions[J] Med. Phys. 1998, 25(5): 656-661.
[8]戴建荣,胡逸民,张红志,等.针对患者调强放射治疗计划的剂量学验证.中华放射肿瘤学杂志.2004,13(3), 229- 232.
[9]马金利,蒋国梁,等.冲洗时间因素对胶片剂量的影响.中华放射肿瘤学杂志.2005, l4(6):514- 518.
[10]李勤,李光俊,韩军等.调强验证中胶片刻度方法的研究.中华放射肿瘤学杂志.2007, 16(5):384- 385.
[11] Esthappan J, Mutic S, Harms WB, et al. Dosimetry of therapeutic photon beams using an extended dose range film. Med. Phys. 2002, 29(10): 2438- 2445.
[12] Suchowerska N, Davison A, Drew J, et al. The validity of using radiographic film for radiotherapy dosimetry. Australas Phys Eng Sci Med, 1997, 20(1): 20- 26.
[13] Robar JL, Clark BG.The use of radiographic film for linear accelerator stereotactic radiosurgical dosimetry. Med. Phys, 1999, 26(10): 2144- 2150.
[14] Danciu C, Proimos BS, Rosenwald JC, et al. Variation of sensitometric curves of radiographic films in high energy photon beams. Med. Phys. 2001, 28(6): 966-974.
[15]周颖娟,黄劭敏,邓小武.辐射显色剂量胶片的特性及其在放射医学的应用.国际肿瘤学杂志,2007,34(1): 28- 30.
[16] GAFCHROMIC? EBT2 self-developing film for radiotherapy dosimetry. February 19, 2009. http://www.gafchromic.com.
[17] Richley L, John AC, Coomber H, et al. Evaluation and optimization of the new EBT2 radiochromic film dosimetry system for patient dose verification in radiotherapy. Phys. Med. Biol, 2010, 55(9): 2601- 2617.
[18] Cheung T, Butson MJ, Yu PK. Post-irradiation colouration of Gafchromic EBT radiochromic film. Phys. Med. Biol, 2005, 50(20): 281- 285.
[19] Butson MJ, Yu PK, Cheung T, et al. High sensitivity radiochromic film dose comparisons. Phys. Med. Biol. 2002, 47(22): 291- 295.
[20]周颖娟,黄劭敏,邓小武.用放射性铬胶片进行调强放疗剂量验证的研究.中华放射肿瘤学杂志2007,16(4):307-312.
[21]高兴旺,祁振宇,张罗生,等.二维半导体探测器阵列与免洗放射性铬胶片在调强放射治疗计划剂量验证中的应用比较.中国肿瘤,2008,17(8):690-693.
[22] Daniel A. Low,James F. Dempsey, Evaluation of the gamma dose distribution comparison method. Med. Phys.2003, 30, 2455–2464.
[23] Chiu-Tsao ST, Ho Y, Shankar R, Wang L, et al. Energy dependence of response of new high sensitivity radiochromic films for megavoltage and kilovoltage radiation energies. Med .Phys. 2005, 32(11): 3350- 3354.
[24] Butson MJ, Cheung T, Yu PK . Absorption spectra analysis of exposed FWT-60 radiochromic film. Phys. Med. Biol, 2004, 49(22): N377- 381.
[25] Leybovich LB, Sethi A, Dogan N. Comparison of ionization chambers of various volumes for IMRT absolute dose verification. Med. Phys. 2003, 30(2): 119- 123.
[26] F. M. Khan, The physics of radiation Therapy, 2nd ed[M]. Baltimore, MD: Williams & Wilkins; 1994, 358- 359.
[27] Esthappan J, Mutic S, Harms WB, et al. Dosimetry of therapeutic photon beams using an extended dose range film. Med. Phys. 2002, 29(10): 2438- 2445.
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