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Characterization of a Novel X-Ray Attenuation Phantom for Radiobiology Irradiators

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N Viscariello

N Viscariello*, W Culberson , J Micka , L DeWerd , University of Wisconsin-Madison, Madison, WI


SU-I-GPD-T-643 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Radiation biology research relies on accurate dose delivery to the target. The HVL of the x-ray beam is generally utilized as a classifying metric for device calibration, but this measurement is not well defined in radiobiology cabinet irradiators. This work presents a novel, single-exposure device for measurement of an alternative attenuation curve metric to compare radiobiology beams to standard NIST-matched beams.

Methods: Two phantoms were designed and fabricated using EBT3 film behind layers of copper or aluminum, depending on beam energy. The attenuation of each reference NIST-matched beam was measured by irradiating the phantom in air. The in-phantom attenuation curves were generated through normalization to an open, unattenuated region. Previously validated Monte Carlo models of the reference orthovoltage beams were utilized in the phantom design, and to determine correction factors accounting for the presence of the surrounding phantom and measurement conditions. The phantoms were then irradiated in two radiobiology cabinet irradiators, a Kimtron IC-160 unit and a PXi XRad 320 unit, for comparison to the reference beams.

Results: The film measurements show that the reference NIST-matched beams can be discriminated using this phantom at all depths of attenuation. Monte Carlo and measurement results agreed to within 3.6%. This model predicts that phantom scatter accounts for less than 5.2% of the contribution to film at any position. Attenuation curves in the radiobiology beams were compared and were able to be matched to the nearest reference beam.

Conclusion: This device was characterized in a range of NIST-matched moderately filtered x-ray beams. Attenuation measurements in radiobiology irradiators indicate that this is a useful method for matching to reference beams. This will allow for calibration of other detectors used in cabinet irradiators to establish traceability to appropriate NIST-matched beams, leading to more accurate dosimetry measurements.

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