Biological dosimetry for iodine contrast medium and X-ray interactions by cell survival

In the presence of an iodinated contrast medium, X-ray absorption is enhanced owing to photoelectric interactions. This has been shown both experimentally and in patients undergoing radiographic procedures using contrast media. Chromosome aberration assays of circulating lymphocytes in these patients revealed a significant increase in absorbed dose compared with those who underwent a similar radiological procedure without the use of contrast media. The authors report measurements of the dose enhancement as a function of iodine concentration and the effect of X-ray hardening on the photoactivation using biological dosimetry based on cell survival. Results show that the magnitude of photoactivation is linearly related to the iodine concentration and that X rays become less effective in eliciting photoactivation as they travel through the iodine-containing volume. Applications of iodine photoactivation based on these findings are also presented. (author)