Program Information
Fluoroscopic Table and Pad Transmission Factors for Peak Skin Dose Estimation
M DeLorenzo*, K Yang , X Li , B Liu , Massachusetts General Hospital, Boston, MA
Presentations
WE-AB-601-6 (Wednesday, August 2, 2017) 7:30 AM - 9:30 AM Room: 601
Purpose: To measure fluoroscopic table and pad attenuation properties for improving the accuracy of patient peak skin dose estimation.
Methods: A complete data set of fluoroscopic table and pad transmission factors was obtained as a function of kVp, added copper (Cu) filtration, and field size for two interventional radiology fluoroscopes: the General Electric (GE) Innova 4100 and Siemens Axiom Artis. A Radcal 10x6-10 ion chamber was suspended from the image receptor, just above the patient support, and centered in the x-ray beam. The field size at the ion chamber was measured with lead rulers. The fluoroscopes were operated in service mode, allowing manual selection of kVp, mA and added Cu filtration. Air kerma rate was measured with the table, and with the table and pad in the x-ray beam for three field sizes (24 x 24 cm², 18 x 18 cm² and 12 x 12 cm²), for every Cu filter choice and for tube voltages ranging from 60-125 kVp, in 10 kVp increments. The patient support was pivoted away from the x-ray beam and the air kerma rate measurements were repeated, from which table transmission factors were calculated.
Results: The GE Innova 4100 table, and table plus pad transmission factors ranged from 0.87 to 0.93 and 0.73 to 0.89, respectively. The Siemens Axiom Artis table, and table plus pad transmission factors ranged from 0.84 to 0.96 and 0.71 to 0.88, respectively.
Conclusion: The patient support pad and field size have a large impact on the broad beam transmission of the fluoroscopic system. Importantly, these results show a wide variation in broad beam table transmission for modern fluoroscopic systems employing large field sizes and a range of Cu filters. The data can be directly used for patient fluoroscopic skin dose estimation.
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