(Sunday, 7/29/2018) 1:00 PM - 1:55 PM
Room: Room 207
Purpose: To characterize the response of Optically Stimulated Luminescent Dosimeters (OSLDs) in a simulated fluoroscopy beam.
Methods: OSLD response to various energies, scatter, time, tube current, angulation, and dose rate were assessed. The half-value layers (HVL) of typical clinical beams in a fluoroscopic system driven by automatic brightness control (ABC) were measured and then replicated using a standard x-ray beam with aluminum (Al) and copper (Cu) filtration added.
Results: By comparing OSLD measurements with those from a 0.6 cc ion-chamber (IC), energy dependence was observed in the clinical range of 65-95 kVp, ranging from 7-24% for Fluoroscopic Mode 1 (1 mm Al + 0.4 mm Cu), 0-7% for Fluoroscopic Mode 2 (1 mm Al + 0.1 mm Cu), and 0-10% for Radio-graphic Mode (1 mm Al). Furthermore, differences in OSLD measurements due to scatter were observed to range from 0-4%,0-4%, and 3-12% for 65, 80, and 100 kVp in Fluoroscopic Mode 1, respectively, while for Fluoroscopic Mode 2, differences ranged from 1-5%, 4-9%, and 0-4% for 65, 80, and 100 kVp, respectively. OSLDs responded linearly (minimum R²=0.995) when compared to IC measurements with varied tube current or exposure time. OSLDs responded differently by 4-15% as a function of dose rate ranging from 136.2-304.4 µGy/s. Although OSLDs showed angular dependence in air, no dependence was observed with OSLDs placed in a cylindrical acrylic phantom. Correction factors were generated to account for OSLD dependence on energy (0.91-1.11), dose rate (0.85-1.04), angulation in air (0.87-1.04) and scatter (0.86-1.12) for different fluoroscopic modes and kVp settings.
Conclusion: Energy, scatter, dose rate, and angularity correction factors were generated for use of OSLDs in interventional fluoroscopic rooms. Large correction factors seem to be necessary for beams filtered with copper.
Keywords
Not Applicable / None Entered.
Taxonomy
Not Applicable / None Entered.
Contact Email
