SU-E-T-153: Proton Linearity and Energy Dependence Studies of Optically Stimulated Luminescent Detectors for Remote Audits of Proton Beam Calibrations by the Radiological Physics Center

Abstract

Purpose: Implement Optically Stimulated Luminescent Detectors (OSLD) into Radiological Physics Centerˈs (RPC) remote audit quality assurance (QA) program for protons. Methods: The OSLDs were aluminum oxide (Al2O3:C) nanoDots™ from Landauer, Inc. (Glenwood, IL.). A standard RPC remote audit electron phantom with detector inserts at two different locations with three scatter rings and slabs of water equivalent plastic phantom, added on top of the phantom to place both dosimeter locations within the SOBP, were used. Two nanoDots™ were placed in each detector insert of the phantom. For the linearity study, a 250 MeV proton beam with reference setup (FS = 10 × 10 cm2, 10cm SOBP) was used with the beam isocenter located between the two detector depths. Doses of 25, 50, 100, 200, 300, 350 cGy at isocenter were delivered. For the energy dependence study, doses of 200 cGy each were delivered with the reference setup for 250, 200, and 160 MeV proton beams. Co-60 measurement was performed as a standardization process. The OSLDs were read on a MicroStar reader from Landauer between 5 to 7 days after irradiation. Results: The OSLD irradiated had a linear dose response of y=−8.3513E−5x+1.0084 with an R2 = 1.000 over the dose range where y=Kl (dose linearity factor) and x=dose. The energy dependence of the OSLD for the three different energies was less than 3% for the irradiation conditions and fluctuation for different OSLDs less than 1% for the same energy used for the RPC remote audit program. Conclusions: The OSLD showed a linear dose response and consistent energy dependence for three proton energies at the MD Anderson Cancer Center Proton Center. OSLD can be used to replace the TLD for RPCˈs remote audit QA program for proton beam output. Work supported by PHS CA0 10953 and CA081647 awarded by NCI, DHHS