Andres Abadia, Presenter: Nothing to Disclose

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

David Pawel, Abstract Co-Author: Nothing to Disclose

In this study, revised Environmental Protection Agency (EPA) risk models have been implemented with the intention of providing age and gender dependent lifetime attributable risk (LAR) tables needed to better quantify stochastic risk in medical imaging studies such as computed tomography, fluoroscopy, and nuclear medicine.

EPA risk models were coded using Microsoft Office Excel 2007. The LAR approach to risk quantification is contrasted, via an FDG PET/CT simulation example (by use of MCNPX), to the use of the ICRP (International Commission on Radiological Protection) effective dose. Effective doses obtained from the simulation were corrected using a detriment adjusted nominal risk coefficient that is reported in ICRP 103 as 5.5 x 10-2 Sv-1. It was deemed more appropriate to analyze only radiogenic cancer mortality risks in order to obtain a better contrast with the effective dose-derived radiation detriment, as a lethality fraction is an integral part of the detriment concept among other stochastic endpoints. Moreover, since effective dose calculations use sex-and-age averaged tissue weighting factors, the effect of using sex-averaged versus sex-specific LARs was also examined.

Radiation detriment was observed to underestimate the overall LAR of cancer mortality, for ages 0-15 years, and started to approach LARs for adults at age 30. For exposure ages 30 through 80 years, radiation detriment overestimated the risk of cancer and erroneously provided the same risk index for all those ages. From the overall LARs it was observed, for this particular example, that averaging across sexes and ages resulted in both overestimation (for males) and underestimation (for females) of risks of cancer-induced mortality to individuals.

The study concluded that sex- and age-averaging, along with the radiation detriment technique of “risk” quantification, are very inconsistent methods and thus unfit quantities to assess individual risks of radiogenic cancer for medical imaging procedures such as nuclear medicine, fluoroscopy, and CT. It is the belief of the author that the LAR approach is much more transparent and subject to better interpretation.

It is extremely vital to be able to quantify stochastic risks to patients resulting from medical diagnostic and interventional procedures since the potential harmful effects are stochastic in nature.

Abadia, A, Bolch, W, Pawel, D, Alternatives to the Effective Dose for Stochastic Risk Assessment in Medical Imaging.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12030467.html