Bernadette L. Kirk

Brachytherapy dosimetry parameters calculated for a new 103Pd source

A new brachytherapy source having 103Pd adsorbed onto silver beads has been designed. The dose distributions of this source have been characterized using version 5 of the MCNP Monte Carlo radiation transport code available from Oak Ridge National Laboratory. These results are presented in terms of the updated AAPM Task Group No. 43 (TG-43U1) formalism, dosimetry parameters, and recommended calculation methodology.

Modulation of fossil fuel production by global temperature variations

Abstract An analysis of the fossil fuel production record since 1860 shows that the exponential growth in production is modulated in the inverse sense by variations in global average temperature. Taking this modulation into account shows that the underlying rate of increase is about 25% less than the widely quoted 4.3% annual rate. This modulation may also produce a partially ameliorating feedback if the often predicted carbon dioxide greenhouse effect actually materializes.

Impact of Radionuclide Physical Distribution on Brachytherapy Dosimetry Parameters

Abstract Radiation dose distributions of brachytherapy sources are generally characterized with the assumption that all internal components are equally radioactive. Autoradiographs and discussions with source manufacturers indicated this assumption of the radionuclide physical distribution may be invalid. Consequently, clinical dose distributions would be in error when not accounting for these internal variations. Many implants use brachytherapy sources with four 125I resin beads and two radiopaque markers used for imaging. Monte Carlo methods were used to determine dose contributions from each of the resin beads. These contributions were compared with those from an idealized source having a uniform physical distribution. Upon varying the 125I physical distribution while retaining the same overall radioactivity, the dose distribution along the transverse plane remained constant within 5% for r > 0.5 cm. For r ≤ 0.5 cm, relative positioning of the resin beads dominated the shielding effects, and dose distributions varied up to a factor of 3 at r = 0.05 cm. For points off the transverse plane, comparisons of the uniform and nonuniform dose distributions produced larger variations. Shielding effects within the capsule were virtually constant along the source long axis and demonstrated that anisotropy variations among the four resin beads were dependent on internal component positioning.

Time series analysis by the Maximum Entropy method

The principal subject of this report is the use of the Maximum Entropy method for spectral analysis of time series. The classical Fourier method is also discussed, mainly as a standard for comparison with the Maximum Entropy method. Examples are given which clearly demonstrate the superiority of the latter method over the former when the time series is short. The report also includes a chapter outlining the theory of the method, a discussion of the effects of noise in the data, a chapter on significance tests, a discussion of the problem of choosing the prediction filter length, and, most importantly, a description of a package of FORTRAN subroutines for making the various calculations. Cross-referenced program listings are given in the appendices. The report also includes a chapter demonstrating the use of the programs by means of an example. Real time series like the lynx data and sunspot numbers are also analyzed. 22 figures, 21 tables, 53 references.

Selective perturbation of in vivo linear energy transfer using high-Z vaginal applicators for Cf-252 brachytherapy

Abstract Californium-252 ( 252 Cf) brachytherapy sources emit both neutrons and photons, and have the potential to vastly improve the current standard-of-practice for brachytherapy. While hydrogenous materials readily attenuate the 252 Cf fission energy neutrons, high- Z materials are utilized to attenuate the 252 Cf gamma-rays. These differences in shielding materials may be exploited when treating with a vaginal applicator to possibly improve patient survival through perturbation of the in vivo linear energy transfer radiation.

THE RADIATION SAFETY INFORMATION COMPUTATIONAL CENTER: A RESOURCE FOR REACTOR DOSIMETRY SOFTWARE AND NUCLEAR DATA

The Radiation Safety Information Computational Center (RSICC) was established in 1963 to collect and disseminate computational nuclear technology in the form of radiation transport, shielding and safety software and corresponding nuclear cross sections. Approximately 1700 nuclear software and data packages are in the RSICC collection, and the majority are applicable to reactor dosimetry.

The Radiation Safety Information Computational Center (RSICC): A resource for nuclear science pplications

The Radiation Safety Information Computational Center (RSICC) has been in existence since 1963. RSICC collects, organizes, evaluates and disseminates technical information (software and nuclear data) involving the transport of neutral and charged particle radiation, and shielding and protection from the radiation associated with: nuclear weapons and materials, fission and fusion reactors, outer space, accelerators, medical facilities, and nuclear waste management. RSICC serves over 12,000 scientists and engineers from about 100 countries.

SU‐FF‐T‐378: Radiation Transport Software for Medical Physics Studies

Purpose: To present a summary of radiationtransportsoftware for medical physics applications. Method and Materials: The RadiationSafety Information Computational Center (RSICC), a center at Oak Ridge National Laboratory (ORNL), is the Department of Energy software center for radiationtransport and safetysoftware. The center houses over 1600 software packages and nuclear cross section data of importance to nuclear science applications. The different software packages have been applied to the following topics: • Dosimetry calculations for radiation therapy • Treatment planning in radiation oncology • Design of photon and secondary neutron shielding for therapy rooms • Evaluating and estimating patient and staff radiationdose • Electron beam transport and energy deposition • Secondary neutron and gamma transport and energy deposition • Cancer brachytherapy dosimetry • Medicaldiagnosticimaging applications, including SPECT, PET, and x‐ray imaging • Error evaluations for accelerator particle delivery systems • Modalities of treatment and exploration of alternatives • Licensing and safety analysis for medicalradiation facilities • Medicaldiagnostics and therapy Examples of software in the RSICC collection include MCNP/MCNPX, ITS, ANISN, TORT, EGS4, PARTISN, SERA, and PENELOPE. There are other software packages (not available through RSICC), which have been applied to the above topics ‐ for example, PENTRAN, A3MCNP, ATTILA, COMET, EGSnrc, TransMED, EVENT, FLUKA, PEREGRINE. Results: Studies on selected software is presented, particularly on the above applications. Conclusion: As the field of medical physics advances, computer software technology continues on the road to improvement and efficiency. Conflict of Interest: Work was supported by the Department of Energy under contract DE‐AC05‐00OR22725.

Impact of impingement on the Hudson River white perch population. Final report

The impact of power plant impingement on the 1974 and 1975 year classes of the Hudson River white perch population is assessed using a simple model derived from Rickers theory of fisheries dynamics. The impact of impingement is expressed in the model as the conditional mortality rate, rather than as the more commonly used exploitation rate. Since the calculated impact is sensitive to errors in the estimation of population size and total mortality, ranges of probable values of these quantities are used to compute upper and lower bounds on the fractional reduction in abundance of each year class. Best estimates of abundance and mortality are used to compute the conditional impingement mortality rate separately for each plant and month. The results are used to assess the relative impacts of white perch impingement at six Hudson River power plants and to identify the seasons during which the impact is highest.

Generalized fish life-cycle poplulation model and computer program

A generalized fish life-cycle population model and computer program have been prepared to evaluate the long-term effect of changes in mortality in age class 0. The general question concerns what happens to a fishery when density-independent sources of mortality are introduced that act on age class 0, particularly entrainment and impingement at power plants. This paper discusses the model formulation and computer program, including sample results. The population model consists of a system of difference equations involving age-dependent fecundity and survival. The fecundity for each age class is assumed to be a function of both the fraction of females sexually mature and the weight of females as they enter each age class. Natural mortality for age classes 1 and older is assumed to be independent of population size. Fishing mortality is assumed to vary with the number and weight of fish available to the fishery. Age class 0 is divided into six life stages. The probability of survival for age class 0 is estimated considering both density-independent mortality (natural and power plant) and density-dependent mortality for each life stage. Two types of density-dependent mortality are included. These are cannibalism of each life stage by older age classes and intra-life-stage competition.