Developing a GYN Cs-Selectron Brachytherapy Treatment Planning Software Accounting for Inter-Source, Applicator and Heterogeneity Effects
H Safigholi1, D Sardari1, S Sina2, S Karimi Jashni3, S Mahdavi3, M Mosleh-Shirazi4, S Karbasi5, F Massicano6, R Guedes Possoni7, H Yoriyaz8, A Meigooni9*, (1) Science and Research Branch, Islamic Azad University, Tehran, Iran,(2) Radiation Research Center, Shiraz University, Shiraz, Fars, (3) Tehran University of Medical Sciences, Tehran, Tehran, (4) Namazi Hospital, Shiraz,(5) Shiraz University of Medical Sciences, Shiraz, Fars, (6) Cidade Universitaria, Sao Paulo,(7) Cidade Universitaria, Sao Paulo, SP, (8) IPEN, Cadidate university, Sao Paulo, SP, (9) Comprehensive Cancer Center of Nevada, Las Vegas, NVSU-E-T-525 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: In this project new treatment software based on TG-43U1 and Monte Carlo (MC) simulations for treatment of GYN cancers were developed. This treatment software accounted for inter-source effect, applicator attenuation, and tissue heterogeneity for Cs-137 selectron machine.
Methods:MC Linear TG-43U1 functions for combination of 8 active-inactive pellets with 2 cm physical length for filling tandem and ovoid were obtained. Total length of tandem and ovoid filled with three and one linear sources, respectively. With this approach inter-source effect and applicator attenuations have been hidden in TG-43U1 functions. To account heterogeneity effect in software design, the library of dose inhomogeneity correction factor (DICF) for various different thickness and position respect to one active Cs pellet for air and aluminum (as a bone) were simulated. A non-homogen GYN polyethylene phantom were designed, which contain a cylinder of air as a rectum, and two symmetric aluminum spheres as a femur bone heads. GYN reference dosimetry points for TLD detectors were machined in the phantom according ICRU-38 report. Finally reference points dose rate were compared using new software, STPS software, TLD measurements and full MC simulations.
Results: New software data have good agreement with TLD and MC simulations (up to 5%). However STPS data for more reference points are less than TLD and MC simulation (up to 3%) due to not considered applicators and inter-source attenuation. For tip of tandem and ovoid STPS data are more than TLD, and MC about 26% and 17%, respectively. More over DICF data can create data with accuracy of 2% in comparison to TLD and MC measurements.
Conclusion:In this project for first time developed a 3D GYN-Cs-Selectron treatment planning software (TPS) based on Linear TG-43U1 functions and libraries of MC simulations which modified inter-source effect, applicator attenuations, and heterogeneity effects.