Abstract：Objective To test intraoperative radiotherapy with mobile photon beam using the INTRABEAM system (Germany), and to analyze the dosimetric characteristics of low-energy photon beam using X-ray source and spherical applicators and explore its potential limitations in clinical application. Methods A special water phantom, a parallel-plate ionization chamber, and an electrometer were used to measure the depth dose rates and isotropy of dose distribution in x/y plane of X-ray source and different spherical applicators in the INTRABEAM system. Those data were then compared with the system data. Results For the X-ray source, the deviation of observed depth dose rate and isotropy in the x/y plane from the system data were-2.16%±1.36% and-1.9%~2.1%, respectively. For applicators with different diameters, the deviation of observed depth dose rate, transfer coefficient, and isotropy in x/y plane from the system data were-10.0%~2.3%,-8.9%~4.2%, and-1.6%~2.6%, respectively. Surface dose rate and dose gradient became larger with the decrease in the diameter of the spherical applicator. The measurement of depth dose rate and isotropy of X-ray source and spherical applicators showed good repeatability. The influencing factors for measurement accuracy included the positioning error of ionization chamber, energy response, noise current, and correction factor f’(R). Conclusions This study reveals the dosimetric characteristics of the INTRABEAM system, verifies the accuracy of the system data, and obtains the data for clinical application and routine quality assurance. However, large dose gradient and small therapeutic range may limit its wide clinical application.
Ouyang Bin,Xiao Zhenhua,Wang Zhenyu et al. Intraoperative radiotherapy using low-energy X rays:dosimetric characteristics and potential limitations in clinical application[J]. Chinese Journal of Radiation Oncology, 2016, 25(8): 867-871.
[1] Armoogum KS,Parry JM,Souliman SK,et al. Functional intercomparison of intraoperative radiotherapy equipment-Photon Radiosurgery System[J].Radiat Oncol,2007,2:11.DOI:10.1186/1748-717X-2-11 [2] Vaidya JS,Wenz F,Bulsara M,et al. Risk-adapted targeted intraoperative radiotherapy versus whole-breast radiotherapy for breast cancer:5-year results for local control and overall survival from the TARGIT-A randomised trial[J].Lancet,2014,383(9917):603-613.DOI:10.1016/S0140-6736(13)61950-9 [3] 赵惠,汪延明,贺清卿,等.INTRABEAM实施乳腺癌术中放疗系统临床应用观察(附20例报告)[J].现代肿瘤医学,2014,22(12):2972-2974.DOI:10.3969/j.issn.1672-4992.2014.12.64 Zhao H,Wang YM,He QQ,et al. Clinical evaluation of the INTRABEAM intraoperative radiotherapy system in 20 patients with breast cancer[J].J Mod Oncol,2014,22(12):2972-2974.DOI:10.3969/j.issn.1672-4992.2014.12.64 [4] Eaton DJ,Duck S.Dosimetry measurements with an intra-operative x-ray device[J].Phys Med Biol,2010,55(12):N359-N369.DOI:10.1088/0031-9155/55/12/N02 [5] Schneider F,Clausen S,Thlking J,et al. A novel approach for superficial intraoperative radiotherapy (IORT) using a 50 kV X-ray source:a technical and case report[J].J ApplClin Med Phys,2014,15(1):4502.DOI:10.1120/jacmp.v15i1.4502 [6] Ebert MA,Asad AH,Siddiqui SA.Suitability of radiochromic films for dosimetry of very-low energy X-rays[J].J Appl Clin Med Phys,2009,10(4):2959.DOI:10.1120/jacmp.v10i4.2957 [7] Soares C,Drupieski C,Wingert B,et al. Absorbed dose measurements of a handheld 50 kVP X-ray source in water with thermoluminescence dosemeters[J].Radiat Prot Dosimetry,2006,120(1-4):78-82.DOI:10.1093/rpd/nci622 [8] Eaton DJ.Quality assurance and independent dosimetry for an intraoperative x-ray device[J].Med Phys,2012,39(11):6908-6920.DOI:10.1118/1.4761865 [9] Ebert MA,Carruthers B.Dosimetric characteristics of a low-kV intra-operative x-ray source:implications for use in a clinical trial for treatment of low-risk breast cancer[J].Med Phys,2003,30(9):2424-2431.DOI:10.1118/1.1595611 [10] Ebert MA,Carruthers B,Lanzon PJ,et al. Dosimetry of a low-kV intra-operative X-ray source using basic analytical beam models[J].Australas Phys Eng Sci Med,2002,25(3):119-123.DOI:10.1007/BF03178772
2016, Vol. 25 
