Modeling energy deposition in trabecular spongiosa using the Monte Carlo code PENELOPE

The inhomogeneity of the target tissue can play an important role in assessing the radiation dose to critical biological targets. This is particularly relevant for calculations of energy deposition by ionizing radiation within regions of radiosensitive trabecular spongiosa. The main focus of this project is the creation of simple quadric-based geometric models of trabecular spongiosa designed specifically for implementation into the general-purpose Monte Carlo radiation transport code PENELOPE. Validation of these models is determined through comparisons of internal dimensions of the model with those of actual bone sites as well as through comparisons of absorbed fractions to the regions within the trabecular spongiosa following the monoenergetic emission of electrons with initial energies ranging from 10 keV to 4 MeV from sources contained within the trabecular spongiosa. On average, absorbed fraction values determined in the current study fall within 2% of values determined by previously published methods. The results of this work suggest that the use of quadric-based geometric models of trabecular spongiosa is a simple and adequate method for implementation into Monte Carlo radiation transport codes.