Program Information
Energy Response of Thermoluminescent Microcube Dosimeters in Water for Kilovoltage X-Ray Beams
L Di Maso*, M Lawless , W Culberson , L DeWerd , University of Wisconsin-Madison, Madison, WI
Presentations
SU-G-201-8 (Sunday, July 31, 2016) 4:00 PM - 6:00 PM Room: 201
Purpose: To characterize the energy dependence for TLD-100 microcubes in water at kilovoltage energies.
Methods: TLD-100 microcubes with dimensions of (1 x 1 x 1) mm³ were irradiated with kilovoltage x-rays in a custom-built thin-window liquid water phantom. The TLD-100 microcubes were held in Virtual Water™ probes and aligned at a 2 cm depth in water. Irradiations were performed using the M-series x-ray beams of energies ranging from 50-250 kVp and normalized to a ⁶⁰Co beam located at the UWADCL. Simulations using the EGSnrc Monte Carlo Code System were performed to model the x-ray beams, the ⁶⁰Co beam, the water phantom and the dosimeters in the phantom. The egs_chamber user code was used to tally the dose to the TLDs and the dose to water. The measurements and calculations were used to determine the intrinsic energy dependence, absorbed-dose energy dependence, and absorbed-dose sensitivity. These values were compared to TLD-100 chips with dimensions of (3.2 x 0.9 x 0.9) mm³.
Results: The measured TLD-100 microcube response per dose to water among all investigated x-ray energies had a maximum percent difference of 61% relative to ⁶⁰Co. The simulated ratio of dose to water to the dose to TLD had a maximum percent difference of 29% relative to ⁶⁰Co. The ratio of dose to TLD to the TLD output had a maximum percent difference of 13% relative to ⁶⁰Co. The maximum percent difference for the absorbed-dose sensitivity was 15% more than the used value of 1.41.
Conclusion: These results confirm that differences in beam quality have a significant effect on TLD response when irradiated in water. These results also indicated a difference in TLD-100 response between microcube and chip geometries. The intrinsic energy dependence and the absorbed-dose energy dependence deviated up to 10% between TLD-100 microcubes and chips.
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