TH‐F‐105‐04: Development of a Novel High‐Throughput Variable Dose Rate Irradiator for in Vitro Radiobiology Research

Abstract

Purpose : Modern biology research often depends upon high‐throughput assays that are incompatible with traditional irradiation techniques due to dose inhomogeneity and dose rate limitations of the most common irradiator systems. To overcome these limitations, we sought to develop a high‐throughput, variable dose rate irradiator for in vitro radiobiology research. Methods: The Xoft Axxent eBx™ was chosen as the x‐ray source for its ability to vary current up to 300 μA, allowing delivery of a variety of doses over a range of dose rates to be applied to a 96‐well cell culture plate. This system delivers a 50kVp spectrum using standard surface applicators. Field flatness was achieved using a 10‐mm diameter surface applicator equipped with a flattening filter that is used for treating skin cancers. Additional collimation was designed to prevent dose contamination into adjacent wells. Dose uniformity was verified using EBT3 Gafchromic film and analyzed using ImageJ, while dose verification was achieved using TLD‐100 measurements and MCNP5 Monte Carlo simulations. Results : Translation of the well plate across the fixed radiation field is achieved using a precision motor‐driven computer controlled positioning system. An Exradin A20 ion chamber has been incorporated into this system to provide periodic air‐kerma rate verification during the irradiation cycle using newly proposed dosimetry formalism for this source. Ion chamber measurements of air‐kerma rate at the skin applicator exit window indicate achievable dose rates of 6–36 mGy/s while the dose uniformity profile of the 10mm Xoft skin applicator was maintained within 3.2% inside the cell culture well. Conclusions: This work indicates significant potential for the development of a high‐throughput, variable dose rate irradiator for in vitro radiobiology research using the Xoft Axxent eBx™ skin applicator system. This irradiator provides a powerful tool by increasing the efficiency and number of assay techniques available for the radiobiology researcher.