Monte Carlo (MC) methods provide the most accurate to-date dose calculations in heterogeneous media and complex geometries, and this spawns increasing interest in incorporating MC calculations into treatment planning quality assurance process. This involves MC dose calculations for clinically produced treatment plans. To perform these calculations, a number of treatment plan parameters specifying radiation beam and patient geometries need to be transferred to MC codes, such as BEAMnrc and DOSXYZnrc. Extracting these parameters from DICOM files is not a trivial task, one that has previously been performed mostly using Matlab-based software. This paper describes the DICOM tags that contain information required for MC modeling of conformal and IMRT plans, and reports the development of an in-house DICOM interface, through a library (named Vega) of platform-independent, object-oriented C++ codes. The Vega library is small and succinct, offering just the fundamental functions for reading/modifying/writing DICOM files in a C++ program. The library, however, is flexible enough to extract all MC required data from DICOM files, and write MC produced dose distributions into DICOM files that can then be processed in a treatment planning system environment. The library can be made available upon request to the authors.
Deep Dive into Vega library for processing DICOM data required in Monte Carlo verification of radiotherapy treatment plans.
Monte Carlo (MC) methods provide the most accurate to-date dose calculations in heterogeneous media and complex geometries, and this spawns increasing interest in incorporating MC calculations into treatment planning quality assurance process. This involves MC dose calculations for clinically produced treatment plans. To perform these calculations, a number of treatment plan parameters specifying radiation beam and patient geometries need to be transferred to MC codes, such as BEAMnrc and DOSXYZnrc. Extracting these parameters from DICOM files is not a trivial task, one that has previously been performed mostly using Matlab-based software. This paper describes the DICOM tags that contain information required for MC modeling of conformal and IMRT plans, and reports the development of an in-house DICOM interface, through a library (named Vega) of platform-independent, object-oriented C++ codes. The Vega library is small and succinct, offering just the fundamental functions for reading/mo
This is a revised version of our paper that has been refereed and published by the
Australasian Physical & Engineering Sciences in Medicine (APESM) journal at:
Australas Phys Eng Sci Med, 2008, Vol. 31 (4), 290-299.
Vega library for processing DICOM data required in Monte Carlo
verification of radiotherapy treatment plans
Christopher Locke1 and Sergei Zavgorodni1,2
1 Department of Physics and Astronomy, University of Victoria, Victoria BC, Canada.
2 Department of Medical Physics, British Columbia Cancer Agency, Vancouver Island
Center, Victoria BC, Canada.
Running title: DICOM library for MC calculations
Key words: Monte Carlo, BEAMnrc, DOSXYZnrc, radiotherapy dose calculations, DICOM
Corresponding author:
Sergei Zavgorodni,
Department of Medical Physics
BC Cancer Agency, Vancouver Island Centre
2410 Lee Street, Victoria, BC, Canada, V8R 6V5
Phone: +1 250-519-5628
Fax: +1 250-519-2024
szavgorodni@bccancer.bc.ca
Abstract
Monte Carlo (MC) methods provide the most accurate to-date dose calculations in heterogeneous media and
complex geometries, and this spawns increasing interest in incorporating MC calculations into treatment
planning quality assurance process. This involves MC dose calculations for clinically produced treatment
plans. To perform these calculations, a number of treatment plan parameters specifying radiation beam and
patient geometries need to be transferred to MC codes, such as BEAMnrc and DOSXYZnrc. Extracting these
parameters from DICOM files is not a trivial task, one that has previously been performed mostly using
Matlab-based software. This paper describes the DICOM tags that contain information required for MC
modeling of conformal and IMRT plans, and reports the development of an in-house DICOM interface,
through a library (named Vega) of platform-independent, object-oriented C++ codes. The Vega library is
small and succinct, offering just the fundamental functions for reading/modifying/writing DICOM files in a
C++ program. The library, however, is flexible enough to extract all MC required data from DICOM files,
and write MC produced dose distributions into DICOM files that can then be processed in a treatment
planning system environment. The library can be made available upon request to the authors.
DICOM library for MC calculations
2
- Introduction
Calculation accuracy of the modern commercial radiotherapy treatment planning algorithms does not always
meet modern dosimetric requirements in situations where dose distributions are delivered to volumes with
heterogeneous media, such as air-tissue and lung-tissue interfaces1-3. It is well recognized that the most
accurate methods to calculate the dose near such interfaces are based on Monte Carlo (MC) electron/photon
particle transport algorithms. In this situation a number of group2,4-10 implemented a process that enables re-
calculation of treatment plans using MC based codes.
Many other groups are also in the process of, or interested in, implementing such MC based “calculation
engines” in their institutions, and most “building blocks” required for this implementation are available or
published. MC codes commonly used in these implementations are BEAM 11,12 and DOSXYZnrc13,14. They
are utilized for modeling radiation transport through linac and patient geometries respectively. The patient
geometry can be specified using CTcreate code14, available with the BEAM/DOSXYZnrc distribution. The
multi-leaf collimator (MLC) shapes and motion can be modeled as reported in the literature8,15-18, with some
of these codes being available from the authors. Methods for calibration of a “Monte Carlo linac” and
conversion of MC calculated dose (given in Gy/electron) to the absolute dose in Gy have also been described
in the literature19,20. Coordinate transformations between EGSnrc co-ordinate system and a DICOM-compliant
treatment planning system (TPS) co-ordinate system, that are required to re-calculate TPS-produced plans
using BEAM/DOSXYZnrc codes, have also been reported by our group recently21.
An essential component of any automated treatment plan verification process is a capability of extracting all
geometry and dosimetric parameters, specific for a treatment plan, from the treatment planning system. Many
modern TPS use the DICOM format as a platform for information exchange - importing and exporting
treatment plans, CT data and dose distributions. Due to the complicated, recursive structure of DICOM files,
extracting the treatment plan parameters such as beam energy, field size, MLC shapes, gantry and couch
angles etc. that need to be transferred from the TPS into the MC system is not a trivial task, and often
becomes a bottleneck in the development of a MC verification system. Only one example of such software,
the DICOM-RT toolbox22, has been reported so far. The DICOM-RT toolbox is MATL
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