Preliminary Investigation of the Dosimetric Properties of 'RadGel'

A preliminary investigation into the efficacy of a new 3D dosimetry material, RadGel™, for verification of radiation therapy dose distributions is presented. Small volumes of RadGel™ were found to exhibit a linear, reproducible response to dose. A gradual increase in optical-density (OD) with time was observed, suggesting scanning should be completed within 18 hours to keep a linear correlation of R(2) > 0.99. A larger 10 cm diameter volume of RadGel™ was irradiated with a rotationally symmetric "spoke" plan designed to rigorously evaluate scanner/dosimeter combined performance. The dosimeter was imaged with the Duke Mid-sized Optical-CT Scanner (DMOS). Promising OD and corresponding dose maps were obtained. Edge artefacts were observed and are suspected to be exacerbated by the particular container used in this early study. Further studies will evaluate new containers and methods for refractive matching at the gel-container-fluid interface.

Consensus radiation protection practices for academic research institutions.

Under the auspices of the Howard Hughes Medical Institute, a set of consensus guidelines for Radiation Protection Practices has been developed for biomedical research using radioactive materials. The purposes of the guidelines are (1) to promote good radiation protection practices consistent with the needs of biomedical research, the ALARA principle, and regulatory requirements; (2) to establish common goals and consistent practices within radiation safety programs; and (3) to build a meaningful partnership between radiation safety professionals and the biomedical research community. These practices are intended to enhance radiation protection and the efficiency of the research staff. The consensus guidelines will lessen the variability in radiation safety practices that is evident among many academic research institutions and will encourage better acceptance and regulatory compliance by users of radioactive materials in biomedical research.

Radiation safety as part of a comprehensive university occupational health and safety program.

Rutgers University has developed an integrated occupational health and safety program incorporating the disciplines of radiation protection, chemical hygiene, industrial hygiene, occupational safety, hazardous substance disposal, and environmental control. The program was implemented by the Department of Radiation and Environmental Health and Safety which was organized in a nontraditional way to provide an interdisciplinary resource and service to a large state university community. In the relatively short period of time that the new organization functioned at full capacity, the strengths of the new organization as well as a few weaknesses have become apparent. We present here a short discussion of the reorganization activities and the lessons learned.

Radiation chemistry of high-energy carbon, neon, and argon ions: molecular hydrogen yields.

Molecular hydrogen yields are reported for cupric sulfate solutions irradiated with high-energy heavy ions. The data are sparse but appear to be consistent with expectations from current theoretical models of the track structure of these ions. By considering these data in conjunction with previously published yields from other systems, estimates of the total water decomposition yields, G'-H2O, have been made.

Imaging of spatial radiation dose distribution in agarose gels using magnetic resonance.

Radiation dose distributions are conventionally measured using ionization chambers or diodes in liquid phantoms, or in two dimensions using film. This work describes a new application of magnetic resonance imaging to radiation dose planning. Agarose gels containing ferrous sulfate, sulfuric acid, and benzoic acid have been irradiated with 137Cs gamma rays and 6-14 MeV electrons, to doses of up to 20 Gy. The dose distributions have been imaged by magnetic resonance, making use of the effect on the T1 proton relaxation times of the radiolytic Fe3+. The image intensity was proportional to doses of up to 10 Gy, and images were stable for at least 24 h postirradiation. The G value for Fe3+ production was about 100 (molecules per 100 eV absorbed).

Radiation chemistry of high-energy carbon, neon, and argon ions: hydrated electron yields.

Neutral aqueous solutions of sodium nitrate/ethanol have been irradiated with high-energy heavy ions from the Berkeley Bevalac. Yields of nitrite have been used to estimate G values for the hydrated electron as a function of the residual range of these ions. Values of G(e-aq) have been estimated as a function of ion energy by adjusting the measured values for the effects of heavy ion fragmentation.

Radiation chemistry of high-energy carbon, neon, and argon ions: hydroxyl radical yields.

Chemical yields of H2O2 have been measured from aerated aqueous solutions of bromide and of formate irradiated at various pHs and solute concentrations with high-energy ions from the Berkeley Bevalac. Hydroxyl radical yields have been deduced from these data as a function of beam penetration into the solutions. By taking fragmentation of the primary ions into account, estimates of the instantaneous Gi OH values for the primary beams as a function of their energy have been made.