  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.
