Dosimetric characterization of an X-ray irradiator for use with cells

Purpose This study aims to characterize an X-ray irradiator (CellRad™, Precision X-ray Inc., North Branford, CT) for use with cells using its internal parallel-plate ionization chamber by evaluating the linearity and repeatability of dose and dose rates delivered by the machine. Methodology Using the on-board software modules for X-ray irradiation, dose linearity and repeatability tests were performed at the following setting: 130 kVp, 5.0 mA, and 33.0 cm source-to-shelf distance. Four (4) setups with distinct combinations of 0.5-mm Al added filtration and turntable rotation settings were employed. The measurements obtained from the internal ionization chamber were analyzed using statistical tests. Results The X-ray irradiator can generate temporally linear and repeatable doses from aluminum-filtered (0.5 mm) and unfiltered X-ray beams (130 kV, 5.0 mA). At a 33.0-cm source-to-shelf distance, the computed dose rates indicate that the X-ray irradiator can deliver 1.345 ± 0.046 Gy/min and 6.718 ± 0.11 Gy/min at the specified tube and shelf settings, with and without the 0.5 mm Al added filter, respectively. An acceptable level of repeatability of the dose is achieved after at least 20 s of irradiation time. The automatic dose control function of the irradiator was also found to measure accumulated doses within ± 5% of the target dose for all the setups employed in this study. The results also revealed that turntable rotation has no significant effect on the dose measured by the internal dosimeter for both filtered and unfiltered beams. On the other hand, adding a 0.5-mm Al filtration significantly alters the beam by decreasing the measured dose rate to only 20% of that of the unfiltered beam. Conclusions and recommendations This study demonstrates that the X-ray irradiator can generate and measure precise radiation doses that vary linearly with irradiation time. The available irradiation modules in the on-board software can be used to deliver doses within ± 5% of the target dose, although irradiation time should be at least 20 s to achieve acceptable dose repeatability. Further dosimetric calibration and output verification using external dosimetry system(s) should be conducted for the complete dosimetric characterization of this X-ray irradiator.