title: A Monte Carlo brachytherapy study for dose distribution prediction in an inhomogeneous medium.
abstract: The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 (192Ir) iodine-125 (125I), and palladium-103 (103Pd). The computer code was validated by comparing the specific dose rate (Lambda), the radial dose function g(r), and anisotropy function F(r,theta;) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The 192Ir seed resulted in a dose rate of 1.115 +/- 0.001 cGy-hr(-1)-U(-1), the 125I seed resulted in a dose rate of 0.965 +/- 0.006 cGy/h(-1)/U(-1), and the 103Pd seed resulted in a dose rate of 0.671 +/- 0.002 cGy/h(-1)/U(-1). The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the 192Ir, an increase in dose rate of 84% for 125I, and an increase in dose rate of 83% for the 103Pd at the surface of the bone nearest to the source.
authors.affiliation: Sacred Heart Medical Center, Department of Radiation Oncology, Spokane, WA 99220, USA. Slate1@shmc.org
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Slate
authors.forename: Howard R
authors.initials: HR
authors.lastname: Elson
authors.forename: Michael A S
authors.initials: MA
authors.lastname: Lamba
authors.forename: William M
authors.initials: WM
authors.lastname: Kassing
authors.forename: Michael
authors.initials: M
authors.lastname: Soldano
authors.forename: William L
authors.initials: WL
authors.lastname: Barrett
mesh_terms: D016880:Anisotropy; D001918:Brachytherapy; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage*; D007496:Iridium Radioisotopes / Q000008:administration & dosage*; D009010:Monte Carlo Method; D009716:Numerical Analysis, Computer-Assisted; D010165:Palladium / Q000008:administration & dosage*; D010306:Parotid Gland / Q000528:radiation effects; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011879:Radiotherapy Dosage
chemical_list: D007457:Iodine Radioisotopes; D007496:Iridium Radioisotopes; D010165:Palladium