Contrast Medium-enhanced Radiation Damage Caused by CT Examinations

Purpose: To assess the effect of iodinated contrast medium (CM) on the induction and repair of DNA double-strand breaks (DSBs) in peripheral blood lymphocytes after computed tomographic (CT) examinations. Materials and Methods: This prospective study was approved by the institutional ethics committee; written informed patient consent was obtained from 37 patients. Venous blood samples were taken from patients before and at 30 minutes, 1 hour, 2.5 hours, and 5 hours after performing CT with (n = 18) or without (n = 19) intravenous administration of CM (iopromide or iomeprol). DSBs were assessed in lymphocytes by enumerating gamma H2AX foci. DSB levels after CT were compared with those obtained after in vitro irradiation. Cell culture experiments with peripheral lymphocytes and fibroblasts were performed with iopromide, iomeprol, or the control substance mannitol added before or immediately after x- or gamma-ray irradiation. DSBs were assessed at 5 minutes, 30 minutes, 2.5 hours, and 5 hours after irradiation. Data were analyzed by using linear regression and the one-tailed Welch and paired sample t tests. Results: The presence of CM during CT increases DSB levels in peripheral lymphocytes by approximately 30%. Cell culture experiments confirmed this effect and further showed that CM administered prior to x- ray irradiation increases the initial DSB yield but has no effect if added after irradiation or when gamma-rays are used instead of x- rays. Conclusion: The highly sensitive gamma H2AX foci assay shows that CM-enhanced radiation damage incurred in peripheral lymphocytes during CT. However, it is unknown whether long-term bioeffects of low-dose ionizing radiation from CT examinations, such as cancer, are increased by using CM. (C) RSNA, 2009