Improvements to Computational Methods for Radiation Dosimetry
Objectives for MPD F.1.1
- Modify existing codes so that they are useable on present day computer operating systems.
- Provide better end-user access to existing computational codes.
Background: Computations have increasingly become a vital part in the chain of steps that relate measurement to dose or kerma. Dosimetric calculations are rooted in comprehensive evaluations of data that describe the basic physical interactions of radiation with matter. These evaluations are then utilized by computer codes that simulate the macroscopic measurement system under consideration, modeling the system in all necessary detail. These computer codes can be deterministic, but more often employ the Monte Carlo technique of particle transport. In addition to their vital role in the standards and measurement process, such codes find increasing use in radiation protection, medical, industrial and security applications involving dosimetry.
Some existing codes still require users to enter data in older computer languages, such as Fortran. Unlike present day computer operating systems, such as the widely used Windows platform, these older codes are less tolerant of errors in data entry and often generate an abundance of data, much of which is not germane to the specific circumstances being modeled. Often times data output has to be transcribed into another program in order to have graphics that clearly illustrate the output of the probability code. The RT-Office code, for example, has been developed in Eastern Europe which functions on a Windows platform, maintains a database of properties of commonly used materials, and generates easily understood graphics directly.
Within the US, access to codes is inhibited by a complex arrangement with the Department of Energy’s Oak Ridge National Laboratory. Royalty fees for alleged maintenance of these codes are charged on a single-user basis. Many of these codes have been developed by taxpayer funded efforts, such as those developed at NIST. It was the opinion of an Industry Working Group at the DOE’s 2009 conference on “Accelerators for America’s Future,” that such intellectual property developed at public expense should be widely available to the public at minimal service costs. In the computational area, this would facilitate the use of these codes in the teaching environment and broaden the end-user use of mathematical simulation. This would bring the US into line with the practice more common in the European Union where laboratories make codes available upon request. The International Atomic Energy Agency (IAEA) has recently published a booklet on the Use of Mathematical Modeling in Electron Beam Processing: A Guidebook and when purchased in hard copy (42 Euros) includes a disk with the commonly used codes on it.
With such a diversity of sources for physical data and for simulation codes, there is a wide variety of applications that make critical use of these methods. In recent years, modeling was useful in establishing depth-dose profiles for the US Postal Service as it adopted radiation treatment to decontaminate mail from potential biohazards, such as anthrax (see Appendix H). Simulations have also been used to study of the possible treatment of high-risk passenger luggage in order to mitigate bioagents and pests. In the radiation therapy field, NIST participated in a study of the dosimetry of beta-emitting brachytherapy sources comparing code results with calibration measurements. The medical community is also finding uses for these codes as exemplified in the development of three dimensional (3D) dosimetry techniques (see MPD A.3.4).
There is a vital effort in using simulations in standards, homeland-security, industrial, radiation-protection and medical applications depends on the health of the underlying code-development efforts. These codes, however, must be in a user friendly computer platform and readily available to the end-user community.
1 – Provide adequate computational resources for NIST to translate the most widely use simulation codes into present day computer operating systems.
2 – Since the use of these codes involves a broad base of industry, the medical community, academia and government, the custody and management of these codes should transferred to NIST, where, in fact, some codes originated. NIST, through its Measurement Services, is properly structured to provide fast and competent user response.
1 – In order to translate the major simulation codes into access via present day computer operating systems, maintain current competency, a minimum of two person-years is required.
2 – The transfer of the custody of existing codes from the Department of Energy to the Department of Commerce will require members of the concerned user community to directly address Congress on this issue.