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Characterization of OSLDs for Use in Small Field Photon Beam Dosimetry

C Pham

C Pham*, P Alvarez, S Kry, D Luo, F Stingo, D Followill, MD Anderson Cancer Ctr., Houston, TX

SU-E-T-56 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: Use optically stimulated luminescent dosimeters (OSLD) whose visible active luminescent area were masked as a remote audit tool to measure small field photon doses down to a 7.5mm diameter field size.

Methods: Different aperture mask sizes (1, 2, and 3mm) were made for the OSLD nanodots and tested to determine which had the best reproducibility. These masks defined the active area of the OSLDs. The OSLDs were characterized by determining correction factors for - linearity, fading, depletion, element, and energy, in order to calculate dose. OSLD readings were performed with an OSLD reader with a known LED light distribution. Dose rate versus field size for OSLDs were generated and compared with other dosimeters (film, diodes, ion chamber, and Monte Carlo). All measurements were performed using a 6MV photon beam.

Results: The study determined the 2mm diameter aperture to be the smallest aperture with the best reproducible readings between each individual OSLD with coefficient of variation ranging between 1-1.5%. Linearity tests for the masked OSLDs showed correspondence with unmasked commissioning data to within 3% for both the 2mm and 3mm diameter aperture, for doses ranging from 50cGy to 200cGy. The 1mm masked OSLD will not be further investigated as it produced non-reproducible results and its linearity correction was not in agreement with the commissioning unmasked correction.

Conclusion: The 2mm masked OSLDs can potentially be used as a remote audit dosimetry tool to measure small photon field sizes doses.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by Public Health Service grants CA010953, CA081647, and CA21661 awarded by the National Cancer Institute, United States Department of Health and Human Services.

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