Room: Exhibit Hall | Forum 7
Purpose: To characterize the energy dependence of TLD-100 microcubes in a mouse phantom for NIST-matched kilovoltage x-ray beams and radiobiology x-ray beams.
Methods: To assess the energy response of the TLD-100 microcubes, irradiations were performed in 3D-printed murine-morphic phantoms. Moderately filtered x-ray beams at the UWADCL, lightly filtered x-ray beams with HVLs matching an XRad 320 radiobiology irradiator, and a â?¶â?°Co beam were used to irradiate the microcubes in-phantom. The irradiators, phantoms, and dosimeters were modeled using the EGSnrc Monte Carlo code. The electron spectra were simulated and compared for the M-series and radiobiology beams. Dose to water and dose to TLD were tallied using the egs_chamber code. The measurements and simulations were used to determine the intrinsic energy dependence, absorbed-dose energy dependence, and absorbed-dose sensitivity in both standard M-series beams and the radiobiology x-ray beams.
Results: The measured in-phantom detector response per dose to water had a maximum difference of 45% relative to â?¶â?°Co.The Monte Carlo-predicted absorbed dose response had a maximum value of 30% relative to â?¶â?°Co. The radiobiology x-ray beams exhibited similar electron spectra to the reference x-ray beams at depth. This led to deviations of less than 3% in the measured and simulated microcube energy response when comparing radiobiology x-ray beams and the reference M-series beams.
Conclusion: These results indicate that changes in beam quality for kilovoltage x-rays has a significant impact on detector output when measuring in phantom. The energy response is consistent with previous investigations of TLD-100 microcube response in water. Though the photon spectra in radiobiology and reference M-series beams differ, the energy response of the TLDs in the radiobiology beams was comparable to the reference beams. This suggests that minimal energy response corrections for TLD-100 microcubes are needed for in-phantom dose verification when appropriate reference x-ray beams are chosen for calibration.