Solving the Boltzmann equation directly using deterministic techniques can be
significantly more efficient than using the Monte Carlo methods, and therefore it can be used to
improve the quality of radiotherapy planning. Relative to the amount of information generated,
and with the use of HPC resources, such techniques usually require significantly lower running
times (relatively to Monte Carlo) to provide detailed and precise solutions. Moreover, the rapid
proliferation of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) enable
human anatomy to be represented using regular images consisting of rectangularly (hexahedral)
shaped voxels in a regular matrix. These new developments make Cartesian geometry
deterministic techniques ideal for medical physics applications, especially given the demand for
high resolution absorbed dose distributions.
This research is focused on the development of EDK-SN, a first-of-a-kind capability to
assess organ absorbed doses incurred in radiation therapy (RT) applications using anatomical
patient models coupled with 3-D deterministic discrete ordinates (SN) radiation transport
methods. Absorbed doses delivered as a result of secondary charged particles will be linked
using electron kernels to account for secondary electron effects. This methodology is proposed
for regions in the phase space where Charged Particle Equilibrium (CPE) is not satisfied, and
subsequent absorbed dose estimation using a collisional kerma is not valid.
1.2 Initial Clinical Dose Evaluations
In the field of radiation therapy, absorbed dose distributions were historically first
approximated without doing any explicit radiation transport at all, but rather by extrapolating
from measured results taken for a particular energy, field size, and source-to-surface distance
(SSD) on a given machine. An extrapolation was performed by modifying the absorbed dose
that was experimentally determined under the reference parameters by ratios representing the
change between specific parameters and the parameters of interest. For example, if absorbed