대한방사선치료학회지 (The Journal of Korean Society for Radiation Therapy)
- 제24권1호
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- Pages.1-10
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- 2012
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- 1598-8449(pISSN)
동적다엽콜리메이터를 이용한 세기변조방사선 치료 시 선량분포상의 선량률 변화에 따른 효과
Effect of Dose Rate Variation on Dose Distribution in IMRT with a Dynamic Multileaf Collimator
- 임경달 (서울대학교병원 방사선종양학과) ;
- 제영완 (서울대학교병원 방사선종양학과) ;
- 윤일규 (서울대학교병원 방사선종양학과) ;
- 이제희 (서울대학교병원 방사선종양학과) ;
- 유숙현 (서울대학교병원 방사선종양학과)
- Lim, Kyoung-Dal (Department of Radiation Oncology, Seoul National University Hospital) ;
- Jae, Young-Wan (Department of Radiation Oncology, Seoul National University Hospital) ;
- Yoon, Il-Kyu (Department of Radiation Oncology, Seoul National University Hospital) ;
- Lee, Jae-Hee (Department of Radiation Oncology, Seoul National University Hospital) ;
- Yoo, Suk-Hyun (Department of Radiation Oncology, Seoul National University Hospital)
- 투고 : 2011.08.30
- 심사 : 2012.03.09
- 발행 : 2012.03.31
초록
목 적: 동적다엽콜리메이터를 이용한 세기변조방사선 치료 시 선량률 임의 변경 되었을 경우 선량 분포 차와 변화를 평가하고자 한다. 대상 및 방법: 소조사야와 대조사야의 두 가지 세기변조방사선치료계획을 임상적 치료계획시스템(Eclipse, Varian, Palo Alto, CA)을 이용하여 계획하였다. 각각의 치료계획은 선량률 100, 400, 600 MU/min으로 변화시켜 조사야별 세 종류로 치료계획을 하였다. 측정기 2D-Array (2D-Array Seven729, PTW-Freiburg)는 측정 깊이 0.5 cm를 고려하여 위로 Solid water phantom (
Purpose: To evaluate dose distribution differences when the dose rates are randomly changed in intensity-modulated radiation therapy using a dynamic multileafcollimator. Materials and Methods: Two IMRT treatment plans including small-field and large-field plans were made using a commercial treatment planning system (Eclipse, Varian, Palo Alto, CA). Each plan had three sub-plans according to various dose rates of 100, 400, and 600 MU/min. A chamber array (2D-Array Seven729, PTW-Freiburg) was positioned between solid water phantom slabs to give measurement depth of 5 cm and backscattering depth of 5 cm. Beam deliveries were performed on the array detector using a 6 MV beam of a linear accelerator (Clinac 21EX, Varian, Palo Alto, CA) equipped with 120-leaf MLC (Millenium 120, Varian). At first, the beam was delivered with same dose rates as planned to obtain reference values. After the standard measurements, dose rates were then changed as follows: 1) for plans with 100 MU/min, dose rate was varied to 200, 300, 400, 500 and 600 MU/min, 2) for plans with 400 MU/min, dose rate was varied to 100, 200, 300, 500 and 600 MU/min, 3) for plans with 600 MU/min, dose rate was varied to 100, 200, 300, 400 and 500 MU/min. Finally, using an analysis software (Verisoft 3.1, PTW-Freiburg), the dose difference and distribution between the reference and dose-rate-varied measurements was evaluated. Results: For the small field plan, the local dose differences were -0.8, -1.1, -1.3, -1.5, and -1.6% for the dose rate of 200, 300, 400, 500, 600 MU/min, respectively (for 100 MU/min reference), +0.9, +0.3, +0.1, -0.2, and -0.2% for the dose rate of 100, 200, 300, 500, 600 MU/min, respectively (for 400 MU/min reference) and +1.4, +0.8, +0.5, +0.3, and +0.2% for the dose rate of 100, 200, 300, 400, 500 MU/min, respectively (for 600 MU/min reference). On the other hand, for the large field plan, the pass-rate differences were -1.3, -1.6, -1.8, -2.0, and -2.4% for the dose rate of 200, 300, 400, 500, 600 MU/min, respectively (for 100 MU/min reference), +2.0, +1.8, +0.5, -1.2, and -1.6% for the dose rate of 100, 200, 300, 500, 600 MU/min, respectively (for 400 MU/min reference) and +1.5, +1.9, +1.7, +1.9, and +1.2% for the dose rate of 100, 200, 300, 400, 500 MU/min, respectively (for 600 MU/min reference). In short, the dose difference of dose-rate variation was measured to the -2.4~+2.0%. Conclusion: Using the Varian linear accelerator with 120 MLC, the IMRT dose distribution is differed a little <(