John R. Cameron Memorial Lecture

Abstract

​John Cameron is well known for two areas of research: Bone Mineral and TLD. I will discuss the present use of TLD for Pre-clinical radiobiology applications and the importance of standards. Radiation dose values for radiobiological research have shown variability in the accuracy of the delivered dose.  While the delivered dose is usually precise within a given institution, the radiobiological results may not be replicable at other institutions. Accurate radiation dose is required to ensure reproducibility in establishing the radiobiological effect in biological systems among institutions. The dose should be the most precise and accurate parameter of the entire process. In the case of X-rays, the energy spectra differ significantly from standard NIST beams. In addition, some doses for 137Cs are based on obsolete quantities, such as the roentgen. To be able to relate biological doses between institutions, accuracy needs to be maintained in reporting the dose. Results from the program for harmonization of dose reviewed 34 machines (X-ray and Isotope) and a total of 83 tests. Traceable NIST beams were used by matching half-value layers (HVL) for the radiobiology X-ray beams with respect to NIST M beams. Phantoms have been developed containing LiF:Mg,Ti thermoluminescent detectors (TLD) to measure the dose from total body irradiation of mice and others. Variations from the requested dose ranged from +20% to - 25% for the X-ray machines. The results have an uncertainty of 2.5% at one standard deviation. Doses were resolved for institutions after discovery of some physics problems which will be explained by examples. For 137Cs, the quantity exposure can be -12% different than absorbed dose to water. Radiobiology applications need the expertise and help of Medical Physicists. The result of this program is harmonization of dose among institutions regardless of radiation source used for the research. ​​