Program Information
Can Fluoroscopic Air-Kerma Rates Be Reliably Measured with Solid-State Meters?
C Feng1*, B Ozus2 , L Thai1 , L Wagner1 , (1)The University of Texas Health Science Center at Houston, Houston, TX,(2) CHI St Luke's Health, Baylor St Luke's Medical Center, Houston, TX
Presentations
SU-D-209-1 (Sunday, July 31, 2016) 2:05 PM - 3:00 PM Room: 209
Purpose:
Ionization chambers remain the standard for calibration of air-kerma rate measuring devices. Despite their strong energy-dependent response, solid state radiation detectors are increasingly used, primarily due to their efficiency in making standardized measurements. To test the reliability of these devices in measuring air-kerma rates, we compared ion chambers measurements with solid-state measurements for various mobile fluoroscopes operated at different beam qualities and air-kerma rates.
Methods:
Six mobile fluoroscopes (GE OEC models 9800 and 9900) were used to generate test beams. Using various field sizes and dose rate controls, copper attenuators and a lead attenuator were placed at the image receptor in varying combinations to generate a range of air-kerma rates. Air-kerma rates at 30 centimeters from the image receptors were measured using two 6-cm³ ion chambers with electrometers (Radcal, models 1015 and 9015) and two with solid state detectors (Unfors Xi and Raysafe X2). No error messages occurred during measurements. However, about two months later, one solid-state device stopped working and was replaced by the manufacturer. Two out of six mobile fluoroscopic units were retested with the replacement unit.
Results:
Generally, solid state and ionization chambers agreed favorably well, with two exceptions. Before replacement of the detector, the Xi meter when set in the “RF High” mode deviated from ion chamber readings by factors of 2 and 10 with no message indicating error in measurement. When set in the “RF Low” mode, readings were within -4% to +3%. The replacement Xi detector displayed messages alerting the user when settings were not compatible with air-kerma rates.
Conclusion:
Air-kerma rates can be measured favorably well using solid-state devices, but users must be aware of the possibility that readings can be grossly in error with no discernible indication for the deviation.
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