Combined with CT, contrast causes significant DNA damage

The addition of an intravenous iodinated contrast agent during chest CT increases the level of radiation-induced DNA damage, according to a study published online Feb. 4 in Radiology.

According to the study’s authors, including Eike I. Piechowiak, MD, with the department of radiology at Phillips University in Marburg, Germany, diagnostic x-ray procedures account for 17 percent of total ionizing radiation exposure to people worldwide, making them the largest known source of man-made radiation exposure.

“Because of x-ray exposure, the risk of developing cancer is increased as a result of additional DNA damage, primarily in the form of DNA double-strand breaks,” Piechowiak and colleagues wrote.

The nephrotoxic and cytotoxic effects of using iodinated contrast agents are well-documented, while little is known about the agents’ effect on DNA damage during CT or angiographic treatment. Piechowiak and colleagues aimed to study the effect of iodinated contrast agents on developing double-strand breaks in DNA in patients who underwent chest CT exams.

In all, 245 patients who were scheduled for a CT were included in the study. Of these, 66 patients underwent unenhanced CT, while 179 patients underwent contrast material-enhanced CT after the intravenous administration of 18.651 mg (average) of iodine.

To study potential damage, the researchers tracked the average number of phosphorylated histone HSAZ (yH2AX) foci lymphocyte using fluorescence microscopy.

In both groups, yH2AX foci levels increased after the CT exam. For the patients who underwent the contrast-enhanced CT, there was an increased amount of DNA radiation damage—the number of induced yH2AX foci increased in this cohort by approximately 107 percent.

Piechowiak and colleagues wrote that these findings have two implications—the first is the potential risk of x-ray radiation cannot by assessed correctly by measuring the dose-length product with CT and that the effect of contrast material needs to be considered.

Second, iodinated contrast agents in x-ray examinations should be considered even more carefully—in repeated investigations, including follow-up examinations, for example.

“The strengths of the present study lie in the large patient cohort, which allowed us to show significant differences exist between groups,” the authors wrote. “In addition, we investigated two clinically relevant patient groups undergoing chest CT with or without the application of contrast agents.”

DNA radiation damage causes cancer and if this damage is enhanced through procedures like contrast mediums administered during CT, the likelihood of cancer generation is theoretically increased, Piechowiak and colleagues added.

“Consequently, the potential cellular effect in contrast-enhanced examinations is not exclusively dependent on the radiation dose and therefore cannot be assessed solely with conventional dosimetry.”