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 gammaH2AX 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 gammaH2AX 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.

Cytotoxicity of iodinated and gadolinium-based contrast agents in renal tubular cells at angiographic concentrations: in vitro study.

PURPOSE: To test in vitro whether gadolinium-based contrast agents induce fewer toxic effects on renal tubular cells than does an iodinated contrast medium at concentrations used for angiography. MATERIALS AND METHODS: LLC-PK1 cells were incubated with iomeprol, gadopentetate dimeglumine, gadobenate dimeglumine, gadoterate meglumine, gadodiamide, and corresponding mannitol solutions for 24 hours at 37 degrees C in two experimental settings: measurements with equally attenuating solutions and measurements with equimolar solutions. Cytotoxicity was assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, trypan blue testing, and an assay to detect apoptosis and necrosis. Data were analyzed with analyses of variance and post hoc tests. RESULTS: Yielding the same x-ray attenuation, iomeprol-300 and iomeprol-150 at concentrations of 2.34-18.75 mg of iodine per milliliter induced significantly (P < .001) lower inhibition of MTT conversion (74%-102% of undamaged control cells) compared with 15.63-125.00 mmol/L concentrations of the gadolinium-based agents (mean percentages of undamaged control cells: 48%-80%, 50%-87%, 60%-95%, and 56%-92% with gadopentetate dimeglumine, gadobenate dimeglumine, gadoterate meglumine, and gadodiamide, respectively). At equimolar concentrations (62.5 mmol/L), iomeprol-190 induced a mean extent of inhibition of MTT conversion (69% of undamaged control cells) similar to that induced by gadoterate meglumine (71%) and gadodiamide (70%), whereas gadopentetate dimeglumine and gadobenate dimeglumine induced stronger effects (63% and 64%, respectively; P < .001). At trypan blue testing, there were more dead cells after incubation with 125 mmol/L gadopentetate dimeglumine than after incubation with iomeprol-190 (57% vs 19%, P < .001). The 125 mmol/L gadopentetate and gadobenate formulations induced more necrosis and apoptosis than did gadoterate meglumine, gadodiamide, and iomeprol (mean percentage difference between treated and untreated control cells: for necrosis, +124%, +95%, +17%, -6%, and +3%, respectively; for apoptosis, +34%, +35%, +13%, +4%, and +5%, respectively; P < .001). CONCLUSION: At angiographic concentrations, gadolinium-based contrast agents do not induce fewer cytotoxic effects on cultured renal tubular cells than does iomeprol.