A verification study of Offset values of different applicators in afterloading brachytherapy
Liu Min, Wang Xianliang, Yuan Ke, Wan Bin, Yang Feng, Kang Shengwei, Li Jie, Wang Pei
Department of Radiation Oncology,Sichuan Cancer Hospital,School of Medicine of University of Electronic Science and Technology of China,Radiation Oncology Key Laboratory of Sichuan Province,Chengdu 610041,China
Abstract：Objective To investigate the Offset values of different applicators in afterloading brachytherapy. Methods Six types of applicators were selected in this study which included stainless steel interstitial needle (Part#083.062),proguide round needle (Part#189.608),proguide sharp needle (Part#189.601),vaginal multi-channel applicator (Part#110.800),fletcher CT/MR applicator (Part#189.745) and henschke titanium applicator (Part#110.437). According to the sources imaging in the fluorography film, the distance of applicators between the first dwell position and the top could be measured. Marker was pasted on the surface of applicator corresponding to the first dwell position. And then the applicator was put into the pelvic phantom for a CT scan. During applicator reconstruction in the treatment planning system, the Offset values of all applicators could be acquired through adjusting the value of offset to superimpose the first dwell and the marker images. On account of the density of plastic material applicators were similar to human tissues, it was difficult to reconstruct the top of the applicator. With the help of stopper or simulation source, the value of offset could be acquired for plastic material applicators. Based on the measurement results, the differences were analyzed among different applicators. Results The Offset values significantly differed among various applicators. The Offset value for stainless steel interstitial needle was -11.4 mm,-4.1 mm for proguide round needle,-3.5 mm for proguide sharp needle, 0 mm or -5.0 mm for vaginal multi-channel applicator,-6.5 mm for fletcher CT/MR applicator and -7.5 mm for henschke titanium applicator, respectively. Conclusion To adapt to the rapid development of precise radiotherapy, it is necessary to verify the Offset value in afterloading brachytherapy.
Liu Min,Wang Xianliang,Yuan Ke et al. A verification study of Offset values of different applicators in afterloading brachytherapy[J]. Chinese Journal of Radiation Oncology, 2020, 29(2): 126-130.
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2020, Vol. 29 
