Impact of backscatter material thickness on the depth dose of orthovoltage irradiators for radiobiology research.

Impact of backscatter material thickness on the depth dose of orthovoltage irradiators for radiobiology research.
Phys Med Biol. 2019 Jan 23;:
Authors: Chen Q, Molloy J, Izumi T, Sterpin E
Abstract
The orthovoltage x-Ray energy frequently used in radiation research is prone to dosimetry errors due to insufficient backscatter conditions. In many radiobiology studies, especially for cell irradiations, precise dose calculation algorithms such as Convolution-Superposition or Monte Carlo are impractical and as such, less accurate hand calculation methods are used for dose estimation. These dose estimation methods typically assume full backscatter conditions. The purpose of this study is to demonstrate the magnitude of the dose error that results from insufficient backscatter, and to provide lookup tables to account this issue. The beam spectra of several widely used commercial systems (XRAD-225, XRAD-320, SARRP) were used in Monte Carlo (MC) simulations on a series of phantom setups to investigate the impact of varying backscatter conditions on dosimetry. The depth dose curves for different field sizes, water phantom thicknesses and beam qualities were generated. In addition, depth dependent backscatter factors for different field sizes and different beam qualities were calculated. It is demonstrated that as much as a 50% dose difference exists for different backscatter conditions at the beam qualities studied. The choice of cell dish siz...

Source: Physics in Medicine and Biology - January 23, 2019 Category: Physics Authors: Chen Q, Molloy J, Izumi T, Sterpin E Tags: Phys Med Biol Source Type: research