Program Information
Sensitivity of the Diagnostic Radiological Index of Protection (DRIP) to the Scatter Spectrum in Fluoroscopy
A Pasciak1 , A Jones2*, L Wagner3 , (1) University of Tennessee Medical Center, Knoxville, TN, (2) MD Anderson Cancer Center, Houston, TX, (3) UT Medical School, Houston, TX
Presentations
TH-AB-201-5 (Thursday, July 16, 2015) 7:30 AM - 9:30 AM Room: 201
Purpose: To evaluate the sensitivity of the Diagnostic Radiological Index of Protection (DRIP) to procedural factors in order to determine the feasibility of defining a single achievable beam quality to measure DRIP.
Methods: Monte Carlo simulations were performed to determine the shapes of scattered X-ray spectra incident on the operator in different clinical scenarios. Spectra were generated using primary spectra from Spektr as source terms with technique factors determined from measured automatic exposure control (AEC) curves. Fluoroscopist and patient were simulated as right elliptical cylinders of ICRU 44 tissue. Energy fluence per exposure (ψ/X) and areal density of elemental attenuators required to reduce beam intensity by 6 HVL were used to quantify changes in spectra.
Results: Results for ψ/X mirrored those for areal density. Projections of the same laterality as operator position resulted in higher ψ/X, while little difference was observed for changing craniocaudal angle. ψ/X increased steeply with increasing kV and added filtration, increasing by 125% from 60 to 120 kV and by 46% from 0.0 to 1.0 mm of copper at 80 kV. Differences were noted depending on operator position and projection, these differences were larger for lower beam qualities. Patient size affected ψ/X mainly through changes in kV and filtration triggered by AEC. Consequently, the highest values of ψ/X were observed for pediatric cardiology procedures and the lowest for adult abdominal interventions. In many circumstances barium was a better attenuator than lead. The areal density of barium required to reduce the scattered beam by 6 HVL varied by a factor of two across the range of scenarios simulated.
Conclusions: Procedural factors must be considered in the specification of beam qualities used to measure the DRIP. kV has the strongest influence on ψ/X and this effect is manifested in many ways through the action of the AEC system.
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