Journal of the Korean Society of Radiology (한국방사선학회논문지)

The Korean Society of Radiology (한국방사선학회)
권호 표지
DOI QR코드

DOI QR Code

Analysis of Photon Characteristics and Absorbed Dose with Cone Beam Computed Tomography (CBCT) using Monte Carlo Method

몬테칼로 기법을 이용한 CBCT의 광자선 특성 및 선량 분석

  • Kim, Jong-Bo (Department of Radiation Oncology, Dongnam Ins. of Radiological & Medical Science) ;
  • Kim, Jung-Hoon (Department of Radiological science, college of health sciences, Catholic University of Pusan) ;
  • Park, Eun-Tae (Department of Radiation Oncology, Inje University Busan Paik Hospital)
  • 김종보 (동남권원자력의학원 방사선종양학과) ;
  • 김정훈 (부산가톨릭대학교 보건과학대학 방사선학과) ;
  • 박은태 (인제대학교 부산백병원 방사선종양학과)
  • Received : 2017.05.31
  • Accepted : 2017.06.30
  • Published : 2017.06.30
Download PDF
⟨ Previous Next ⟩

Abstract

The cone beam computed tomography(CBCT) which can acquire 3-dimensions images is widely used for confirmation of patient position before radiation therapy. In this study, through the simulation using the Monte Carlo technique, we will analyze the exposure dose by cone beam computed tomography and present the standardized data. For the experiment, MCNPX(ver. 2.5.0) was used and the photon beam spectrum was analyzed after Cone beam was simulated. As a result of analyzing the photon beam spectrum, the average energy ranged from 25.7 to 37.6 keV at the tube voltage of 80 ~ 120 kVp and the characteristic X-ray energy was 9, 60, 68 and 70 keV. As a result of using the water phantom, the percentage depth dose was measured, and the maximum dose appeared on the surface and decreased with depth. The absorbed dose also decreased as the depth increased. The absorbed dose of the whole phantom was 9.7 ~ 18.7 mGy. This is a dose which accounts for 0.2% of about 10 Gy, which is generally used for radiation therapy per week, which is not expected to have a significant effect on the treatment effect. However, it should not be overlooked even if it is small compared with prescription dose.

방사선 치료 시 자세 확인 촬영을 목적으로 3차원 영상 획득이 가능한 콘빔씨티 촬영이 많이 이용되고 있다. 본 연구에서는 몬테칼로 기법을 이용한 모의실험을 통해 콘빔씨티 촬영 시 피폭선량을 정략적으로 분석하고 표준화된 데이터를 제시하고자 한다. 실험은 MCNPX(ver. 2.5.0)를 이용하였으며, 먼저 콘빔씨티를 모사한 후 광자선 스펙트럼을 분석하였다. 그리고 물 팬텀을 모사하여 깊이별 심부선량 백분율과 흡수선량을 측정하였다. 광자선 스펙트럼을 분석한 결과, 관전압 80 ~ 120 kVp 에서 평균 에너지는 조건에 따라 25.7 ~ 52.6 keV로 나타났으며 특성X선 에너지는 9, 60, 68, 70 keV로 나타났다. 물 팬텀을 사용하여 심부선량 백분율을 측정한 결과 표면에서 최대선량이 나타났으며 깊이가 깊어질수록 감소하는 것으로 나타났다. 흡수선량 또한 깊이가 증가할수록 감소하였으며 팬텀 전체가 받는 흡수선량은 9.7 ~ 18.7 mGy로 나타났다. 이는 일반적으로 방사선 치료에 사용되는 주당 처방선량인 약 10Gy의 0.2%를 차지하는 선량이며 이는 치료효과에는 큰 영향을 미치지 않을 것으로 판단된다. 그러나 처방선량에 비해 미미한 수준일지라도 이를 간과해서는 안 될 것이다.

Keywords

References

  1. D. Y. Kim, J. W. Choi, J. G. Yoon, "Comparison of using CBCT with ST Simulator for Radiation dose of Treatment Planning," The journal of the korea contents assosiations, Vol. 9, No. 12, pp. 1159-1166, 2009.
  2. Y. J. Kim, J. S. Lee, S. Y. Hong, H. J. Ko, "A Comparison between Three Dimensional Radiation Therapy and Intensity Modulated Radiation Therapy on Prostate Cancer," Journal of the Korean Society of Radiology, Vol. 7, No 6, pp. 409-414, 2013. https://doi.org/10.7742/jksr.2013.7.6.409
  3. S. J. Bang, Y. Y. Kim, I. S. Jeong, J. S. Kim, Y. G. Kim, "A Study of Image Quality and Exposed Dose by Field Size Changing on CBCT," The journal of the korean society for radiotherapeutic technology, Vol. 25, No. 2, pp. 175-180, 2013.
  4. C. J. Park, S. H. Park, J. S. Kim, Y. Y. Han, S. G. Ju, E. H. Shin, J. S. Shin, H. C. Park, Y. C. Ahn, "Digital Tomosynthesis for Patient Alignment System Using Half-fan Mode CBCT Projection Images," Korean Journal of Medical Physics, Vol. 21, No. 4, 2010.
  5. S. B. Hwang, K. H. Kim, I. H. Kim, W. Kim, H. S. Im, S. C. Han, J. M. Kang, J. H. Kim, "Imaging dose evaluations on Image Guided Radiation Therapy," The journal of the korean society for radiotherapeutic technology, Vol. 27, No. 1, pp. 1-11, 2015.
  6. J. H. Wang, "Guidelines for dose reduction in radiological imaging," Ministry of Food and Drug Safety, Chung-ju, Choong-buk, pp. 20-28, 2014.
  7. Semelka.R.C, Armao.D. M, Elias. J, Huda. W, "Imaging strategies to reduce the risk of radiation in CT studies, including selective substitution with MRI", Journal of magnetic resonance imaging, Vol. 25, No. 5, pp. 1053-1807, 2007.
  8. B. H. Won, "Numerical modeling of a density log and a spectral gamma-ray log using MCNP," Geological sience major, Division of earth environmental system, The graduate school of Pusan National University, 2014.
  9. J. K. Lee, "The study of radiation dose estimates for computed tomography using Monte Carlo method," Department of nuclear engineering, The graduate school of Kyung Hee University, 2011.
  10. J R. Briesmeister, "A General Monte Carlo N-Particle Transport Code,Version 4C, Manual LA-13790-M", Los Alamos Nat'1 Lab. 2000.
  11. Denise B. Pelowitz, "MCNPXTM USER'S MANUAL, Version 2.5.0," The Regents of the University of California at Los Alamos National Laboratory, California, 2005.
  12. H. J. Lim, "Status of Domestic Linear Accelerator," Health Insurance Review & Assessment Service, Won-ju, Kang-won, 2015.
  13. Abuhaimed, Abdullah Abdulaziz, "Dosimetric Investigations of Kilovoltage Cone Beam Computed Tomography (kV-CBCT) Utilized in Image Guided Radiation Therapy (IGRT) using Monte Carlo Simulations," PhD thesis, University of Glasgow, 2015.
  14. P. Downes, R. Jarvis, E. Radu, I. Kawrakow, E. Spezi, "Monte Carlo simulation and patient dosimetry for a kilovoltage cone-beam," Medical Physics, Vol. 36, No. 9, pp. 4156-4223, 2009. https://doi.org/10.1118/1.3196182
  15. W.Y. Song, S. Kamath, S. Ozawa, S.A. Ani, A. Chvetsov, N. Bhandare, J.R. Palta, C. Liu, J.G. Li, "A dose comparison study between XVI(R) and OBI(R) CBCT systems," Medical Physics, Vol. 35, No. 2, pp. 0094-2405, 2008.
  16. S. S. Kang, I. H. Ko, et al., "Radiation Therapeutics," Chung Koo Publishing Co., pp. 138-139, 2007.
  17. C. H. Lim, M. K. Cho, J. C. Han, H. B. Yoon, S. M. Yoon, M. H. Cheong, H. K. Kim, "Development of an MCNP-Based Cone-Beam CT Simulator," Journal of The Korean Society for Nondestructive Testing, Vol. 29, No. 4, pp. 351-359, 2009.
  18. Ding, G. X. , Duggan, D. M. , Coffey, C. W., "Characteristics of kilovoltage x-ray beams used for conebeam computed tomography in radiation therapy," Physics in Medicine and Biology, Volume 52, No. 6, pp. 0031-9155, 2007.
  19. Fouad Abdulaziz Abolaban "On Board Cone Beam CT for Treatment Planning in Image Guided Radiotherapy," Faculty of Engineering, The gaduate school of King Abdulaziz University, Saudi Arabia. 2011.
  20. Asa Palm, Elisabeth Nilsson, Lars Herrnsdorf "Absorbed dose and dose rate using the Varian OBI 1.3 and 1.4 CBCT system," Journal of applied clinical medical physics, Vol. 11, No. 1, pp. S93-S93, 2009.
  21. Y. M. Moon, "A study on the effective dose measurement for cone beam computed tomography using glass dosimeter," Department of Physics, The graduate school of Dong-A University, 2012.