title: A simplified analytical dose calculation algorithm accounting for tissue heterogeneity for low-energy brachytherapy sources.
abstract: The American Association of Physicists in Medicine Task Group No. 43 (AAPM TG-43) formalism is the standard for seeds brachytherapy dose calculation. But for breast seed implants, Monte Carlo simulations reveal large errors due to tissue heterogeneity. Since TG-43 includes several factors to account for source geometry, anisotropy and strength, we propose an additional correction factor, called the inhomogeneity correction factor (ICF), accounting for tissue heterogeneity for Pd-103 brachytherapy. This correction factor is calculated as a function of the media linear attenuation coefficient and mass energy absorption coefficient, and it is independent of the source internal structure. Ultimately the dose in heterogeneous media can be calculated as a product of dose in water as calculated by TG-43 protocol times the ICF. To validate the ICF methodology, dose absorbed in spherical phantoms with large tissue heterogeneities was compared using the TG-43 formalism corrected for heterogeneity versus Monte Carlo simulations. The agreement between Monte Carlo simulations and the ICF method remained within 5% in soft tissues up to several centimeters from a Pd-103 source. Compared to Monte Carlo, the ICF methods can easily be integrated into a clinical treatment planning system and it does not require the detailed internal structure of the source or the photon phase-space.
authors: Medical Biophysics Department, Sunnybrook Research Institute, University of Toronto, 2075 Bayview Avenue, Toronto, ON M4N3M5, Canada.
authors: Shahram
authors: S
authors: Mashouf
authors: Eli
authors: E
authors: Lechtman
authors: Luc
authors: L
authors: Beaulieu
authors: Frank
authors: F
authors: Verhaegen
authors: Brian M
authors: BM
authors: Keller
authors: Ananth
authors: A
authors: Ravi
authors: Jean-Philippe
authors: JP
authors: Pignol
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D016477:Artifacts; D001918:Brachytherapy / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D009010:Monte Carlo Method; D010165:Palladium / Q000737:chemistry*; D019047:Phantoms, Imaging; D011868:Radioisotopes / Q000737:chemistry*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D014867:Water / Q000737:chemistry
chemical_list: D011868:Radioisotopes; D014867:Water; D010165:Palladium