Investigation of Tissue Heterogeneities Effect on Dose Distribution from 192-Ir Source During Brachytherapy Treatments

Document Type : Original Article

Authors

1 Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

2 Department of Medical Physics, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

3 Department of Oral and Maxillofacial Radiology, Faculty of Density, Ahvaz Jundishapur University of Medical Sciences, Ahwaz, Iran

Abstract

Background and objective: The possible defect of recommended protocol by the American Association of Physicists in Medicine (AAPM, TG43) for dosimetry in the field of brachytherapy is that this protocol does not consider tissue heterogeneities (such as bone, lung, …) when applying resulted dosimetry parameters in treatment planning systems. The purpose of this study was to evaluate dose differences with and without heterogeneities in brachytherapy with iridium source (Ir -192)
Subjects and Methods: Dose distribution from microselectron HDR Ir-192 source located in center of the homogeneous water phantom calculated by MCNP-4C simulation method. In different simulations, heterogeneities of bone, lung, air and soft tissue were considered. The effect of source positioning in phantom and distance between source and heterogeneities on dose distribution were evaluated.
Results: The calculated dose, due to heterogeneity of bone, was reduced, while those due to air and lung were increased? Heterogeneity of soft tissues has no meaningful effect on the dose distribution.  Increasing distance from center of phantom decreases dose due to decrease of scattering.
Conclusion: Heterogeneities of bone, lung, and air especially in the near distance from Ir-192 source implanted position can change the dose compared to the water homogeneity phantom. In future Treatment Planning System (TPS) TPS, for accurate dose estimation, the effect of heterogeneities on dose distribution should be considered. Furthermore, in order to acquire the exact dose, due considerations of correct amount of scattering, dosimetry must be carried out on a large enough phantoms.

Keywords

References

1-Rivard MJ, Coursey BM, DeWerd LA, Hanson WF, Huq MS, Ibbott GS, et al. Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. Med Phys 2004;31(3):633-74.
2-Meigooni AS, Nath R. Tissue inhomogeneity correction for brachytherapy sources in a heterogeneous phantom with cylindrical symmetry. Med Phys 1992;19(2):401-7.
3-Williamson JF, Perera H, Li Z, Lutz WR. Comparison of calculated and measured heterogeneity correction factors for 125I, 137Cs, and 192Ir brachytherapy sources near localized heterogeneities. Med Phys 1993;20(1):209-22.
4-Kirov AS, Williamson JF, Meigooni AS, Zhu Y. Measurement and calculation of heterogeneity correction factors for an Ir-192 high dose-rate brachytherapy source behind tungsten alloy and steel shields. Med Phys 1996;23(6):911-9.
5-Das RK, Keleti D, Zhu Y, Kirov AS, Meigooni AS, Williamson JF. Validation of Monte Carlo dose calculations near 125I sources in the presence of bounded heterogeneities. Int J Radiat Oncol Bio Phys 1997;1;38(4):843-53.
6-Daskalov GM, Kirov AS, Williamson JF. Analytical approach to heterogeneity correction factor calculation for brachytherapy. Med Phys 1998;25(5):722-35.
7-Das I, Both S, Cheng C. Inhomogeneity correction in brachytherapy. Med Phys 2006;33(6):2112.  
8-Poon E, Verhaegen F. An analytical approach to account for shielding, anatomical heterogeneities and patient dimensions for 192Ir high dose rate brachytherapy applications. Med Phys 2008;35(6):2864.
9-Kwan IS, Wilkinson D, Cutajar D, Lerch M, Rosenfeld A, Howie A, et al. The effect of rectal heterogeneity on wall dose in high dose rate brachytherapy. Med Phys 2009;36(1):224-32.
10-Graf M, Scanderbeg D, Yashar C, Jiang S. SU-GG-T-37: Monte carlo dose comparison assessing material inhomogeneity effects in breast brachytherapy. Med Phys 2010;37(6):1.
11-Karaiskos P, Angelopoulos A, Sakelliou L, Sandilos P, Antypas C, Vlachos L, et al. Monte Carlo and TLD dosimetry of an 192Ir high dose-rate brachytherapy source. Med Phys 1998;25(10):1975-84.
12-Yang Y, Rivard MJ. Evaluation of brachytherapy lung implant dose distributions from photon-emitting sources due to tissue heterogeneities. Med Phys 2011;38(11):5857-62.
13-Terribilini D, Manser P, Frei D, Volken W, Mini R, Fix MK. Implementation of a brachytherapy Ir-source in an in-house system and comparison of simulation results with EGSnrc, VMC++ and PIN. J Physics 2007;74(1):14.
14-Chandola RM, Tiwari S, Kowar MK, Choudhary V. Effect of inhomogeneities and source position on dose distribution of nucletron high dose rate Ir-192 brachytherapy source by Monte Carlo simulation. J Cancer Res Ther 2010;6(1):54-7.
15-Granero D, Perez-Calatayud J, Pujades-Claumarchirant MC, Ballester F, Melhus CS, Rivard MJ. Equivalent phantom sizes and shapes for brachytherapy dosimetric studies of 192Ir and 137Cs. Med Phys 2008;35(11):4872-7.
16-Russell KR, Ahnesjö A. Dose calculation in brachytherapy for a192Ir source using a primary and scatter dose separation technique. Phys Med Biol 1996;41(6):1007-24.
Jundishapur Scientific Medical Journal
Volume 12, Issue 3 - Serial Number 84
July and August 2013
Pages 285-297

Files

History

  • Receive Date: 11 December 2012
  • Revise Date: 10 January 2013
  • Accept Date: 09 February 2013

Share

How to cite

Statistics