Application of a Pelvic Phantom in Brachytherapy Dosimetry for High-dose-rate (HDR) 192Ir Source Based on Monte Carlo Simulations

다국어 초록 (Multilingual Abstract)

In this study, we evaluate how the radial dose function is influenced by the source position as wellas the phantom size and shape. A pelvic water phantom similar to the pelvic shape of a human bodywas designed by averaging dimensions obtained from computed tomography (CT) images of patientstreated with brachytherapy for cervical cancer. Furthermore, for the study of the effects of sourceposition on the dose distribution, the position of the source in the water phantom was determinedby using the center of mass of the gross target volume (GTV) in the CT images. To obtain thedosimetric parameter of a high-dose-rate (HDR) 192Ir source, we performed Monte Carlo simulationsby using the Monte Carlo n-particle extended code (MCNPX). The radial dose functions obtainedusing the pelvic water phantom were compared with those of spherical phantom with differentsizes, including the Monte Carlo (MC) results of Williamson and Li. Differences between the radialdose functions from this study and the data in the literature increased with the radial distances.
The largest differences appeared for spherical phantom with the smallest size. In contrast to thepublished MC results, the radial dose function of the pelvic water phantom significantly decreasedwith radial distance in the vertical direction because full scattering was not possible. When thesource was located in posterior position 2 cm from the center in the pelvic water phantom, thedifferences between the radial dose functions rapidly decreased with the radial distance in the lowervertical direction. If the International Commission on Radiation Units and Measurements bladderand rectum points are considered, doses to these reference points could be underestimated by upto 1% − 2% at a distance of 3 to 6 cm. Our simulation results provide a valid clinical referencedata and can used to improve the accuracy of the doses delivered during brachytherapy applied topatients with cervical cancer.

참고문헌 (Reference)

1 T. J. Choi, 20 : 283-, 2002

2 G. P. Glasgow, 6 : 49-, 1979

3 F. Ballester, 24 : 1221-, 1997

4 A. S. Meigooni, 27 : 2168-, 2000

5 D. Baltas, 28 : 1875-, 2001

6 R. Nath, 22 : 209-, 1995

7 M. J. Rivard, 31 : 633-, 2004

8 W. H. Ellett, 14 : 615-, 1969

9 J. P´erez-Calatayud, 31 : 2075-, 2004

10 J. F. Williamson, 18 : 776-, 1991

11 D. Granero, 35 : 4872-, 2008

12 J. F. Williamson, 22 : 809-, 1995

13 G. M. Daskalov, 25 : 2200-, 1998

14 P. Karaiskos, 30 : 9-, 2003

15 P. Papagiannis, 30 : 712-, 2003

16 D. Granero, 76 : 79-, 2005

17 R. E. Wallace, 26 : 2465-, 1999

18 D. Granero, 38 : 487-, 2011

19 F. Ballester, 27 : 2182-, 2000

20 E. Casal, 27 : 132-, 2000

21 F. Ballester, 46 : 2029-, 2001

22 J. Perez-Calatayud, 29 : 538-, 2002

23 J. C. Anctil, 25 : 2279-, 1998

24 R. K. Valicenti, 22 : 821-, 1995

25 A. S. Kirov, 40 : 2015-, 1995

26 안우상, "미소선원 적분법과 몬테칼로 방법을 이용한 AAPM TG-43 선량계산 인자 평가: microSelectron HDR Ir-192 선원에 대한 적용" 한국의학물리학회 22 (22): 190-197, 2011

27 F. M. Khan, "The Physics of Radiation Therapy" Lippincott Williams & Wilkins 315-, 2010

28 D. B. Pelowitz, "MCNPXTM User’s Manual, Version 2.7.0, LA-CP-1100438" 2011

29 L. L. Anderson, "Interstitial Collaborative Working Group (IGWG), Interstitial Brachytherapy: Physical, Biological, and Clinical Considerations" Raven 1990