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KMID : 1164220140260020225
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Journal of Korean Society for Radiotherapeutic Technology
2014 Volume.26 No. 2 p.225 ~ p.232
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Evaluation of superficial dose for Postmastectomy using several treatment techniques
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Song Yong-Min
Choi Ji-Min
Kim Jin-Man
Kwon Dong-Yeol
Kim Jong-Sik
Cho Hyun-Sang
Song Gi-Won
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Abstract
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Purpose : The purpose of this study was to evaluate the surface and superficial dose for patients requiring postmastectomy radiation therapy(PMRT) with different treatment techniques.
Materials and Methods : Computed tomography images were acquired for the phantom(I’mRT, IBA) consisting of tissue equivalent material. Hypothetical chestwall and lung were outlined and modified. Five treatment techniques(Wedged Tangential; WT, 4-field IMRT, 7-field IMRT, TOMO DIRECT, TOMO HELICAL) were evaluated using only 6MV photon beam. GafChromic EBT3 film was used for dose measurements at the surface and superficial dose. Surface dose profiles around the phantom were obtained for each treatment technique. For superficial dose measurements, film were used inside the phantom and analyzed superficial region for depth from 1-6mm.
Results : TOMO DIRECT showed the highest surface dose by 47~70% of prescribed dose, while 7-field IMRT showed the lowest by 35~46% of prescribed dose. For the WT, 4-field IMRT and 7-field IMRT, superficial dose were measured over 60%, 70%, and 80% for 1mm, 2mm, and 5mm depth, respectively. In case of TOMO DIRECT and TOMO HELICAL, over 75%, 80%, and 90% of prescribed dose was measured, respectively. Surface and superficial dose range were uniform in overall chestwall for the 7-field IMRT and TOMO HELICAL. In contrast, Because of the dose enhancement effect with oblique incidence, The dose was gradually increased toward the obliquely tangential angle for the WT and TOMO DIRECT.
Conclusion : For PMRT, TOMO DIRECT and TOMO HELICAL deliver the higher surface and superficial doses than treatment techniques based linear accelerator. It showed adequate dose(over 75% of prescribed dose) at 1mm depth in skin region.
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KEYWORD
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Postmastectomy, skin dose, Gafchromic EBT3
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