David Borrego MS, Presenter: Nothing to Disclose

Daniel A. Siragusa MD, Abstract Co-Author: Nothing to Disclose

Wesley E. Bolch PhD, Abstract Co-Author: Nothing to Disclose

Data from a detailed parameterization of over 23,763 exposure conditions from high frequency and/or high-dose fluoroscopically guided interventions reveal the dynamic nature of these procedures. As such, simple point calibrations of the KAP meter and spectral data assumptions may lead to gross errors in skin and organ dose calculations. This work seeks to investigate new methods and calibrations for improved accuracy gains over previous iterations of the University of Florida’s Rapid In-Clinic Peak Skin Dose Algorithm (RIPSA).

Calibration factor maps were developed that accounted for copper filtration, tube voltage, and current. The calibration factor maps were then coded into the RIPSA software for improved accuracy. Organ doses are further dependent on x-ray energy spectra. A first order estimation of the energy spectra was generated along with an energy spectra to match measured first and second HVLs to within ± 3% with an in-house spectrum generator based on the TASMIP database. Organ doses were then calculated with the use of MCNPX transport code.

The only statistically significant variables affecting the calibration factor are tube voltage within each filtration based on a one-way ANOVA (F(10,97)=3.18, p=0.001, α=0.05). The KAP meter is highly dependent on the quality of the x-ray spectra, which can introduce errors of up to 40% without the use of the calibration factor maps. Matching spectral data to the first and second HVLs yielded a 17% improvement in organ doses within in-field organs. These additional steps in calculating organ and skin doses have a negligible computational burden on the RIPSA software, with an average time of less than two seconds to calculate skin doses following an irradiation event.

This work represents robust improvements to the University of Florida’s RIPSA software by incorporating detailed x-ray energy spectra and calibration curves for the KAP meter while also overcoming the challenges of characterizing: 1) a dynamic radiological exam and 2) the variability of a patient population when conducting a dose reconstruction that can provide the interventional physician information needed to modify behavior when clinically appropriate.

This work is an innovative effort, overcoming previous challenges, to equip interventional radiologists with accurate organ and real-time skin dose distributions to help guide clinical decisions.

Borrego, D, Siragusa, D, Bolch, W, Developments to a Rapid In-clinic Peak Skin and Organ Dose Algorithm for Improved Patient Risk Management During High-dose Fluoroscopically Guided Interventions.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13016791.html