Design and performance characteristics of an experimental cesium-137 irradiator to simulate internal radionuclide dose rate patterns.

ABSTRACT

UNLABELLED When radionuclides are administered internally, the biological effect can depend on the total absorbed dose and the rate at which it is delivered. A 137Cs irradiator was designed to deliver dose-rate patterns that simulate those encountered in radionuclide therapy. METHODS: An 18-Ci 137Cs irradiator was fitted with a computer-controlled mercury attenuator that facilitated changes in dose rates as desired. The absorbed dose and dose rates were calibrated with MOSFET dosimeters customized for low dose-rates. RESULTS: Initial dose rates ranging from 0.01-30 cGy/hr can be delivered depending on the location of the cage in the irradiator and the thickness of the mercury in the attenuator system. To demonstrate the irradiator system's capability to deliver dose-rate patterns encountered in radionuclide therapy, a simulation was performed where the dose rate initially increased exponentially followed by an exponential decrease in the dose rate. CONCLUSION: The irradiator system is well-suited to expose small animals to any dose-rate pattern, thereby facilitating calibration of biological dosimeters (e.g., cell survival, chromosome aberrations), which can be used to measure the absorbed dose to a target tissue after administration of radionuclides.