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18 F-FDG PET/CT imaging is used in the diagnosis of diseases, including cancers. The principal photons used for imaging are 511 ke V gamma photons resulting from positron annihilation. The absorbed dose varies among body organs, depending on administered radioactivity and biological clearance. We have attempted to evaluate DNA double-strand breaks (DSB) and toxicity induced in V79 lung fibroblast cells in vitro by 18 F-FDG, at doses which might result from PET procedures. Cells were irradiated by 18 F-FDG at doses (14.51 and 26.86 mGy), comparable to absorbed doses received by critical organs during PET procedures. The biological endpoints measured were formation of γ-H2AX foci, mitochondrial stress, chromosomal aberrations, and cell cycle perturbation. Irradiation induced DSB (γH2AX assay), mitochondrial depolarization, and both chromosome and chromatid types of aberrations. At higher radiation doses, increased aneuploidy and reduced mitotic activity were also seen. Thus, significant biological effects were observed at the doses delivered by the 18 F-FDG exposure and the effects increased with dose., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objective: To quantify DNA damage in patients undergoing non-contrast and contrast-enhanced 18 F-FDG PET/CT whole body positron emission tomography/computed tomography (WB PET/CT) investigations using comet assay technique and micronucleus assay, and to study the effect of other baseline parameters of patients on DNA damage. Methodology: Eighty-four patients referred for 18 F-FDG PET/CT investigation were included in the study of which 44 patients underwent contrast-enhanced WB PET/CT and 40 patients underwent non-contrast WB PET/CT investigations. The investigations were performed on Discovery 690 PET/CT. For contrast-enhanced investigation, Omnipaque300 was injected intravenously based on the patient body weight. Absorbed dose resulting from the intravenous administration of 18 F-FDG was estimated using the ICRP 106 dose coefficients. Radiation dose from the acquisition of CT scans was estimated using CT dose index and dose-length product. Blood samples were collected from the patients for DNA damage analysis. Comet assay and MN assay was used to assess the DNA damage. The Differences in the comet TM (Tail Moment) and MNBC % in both groups were calculated. Result: The radiation dose received by the study population during 18 F-FDG WB PET/CT examination was 27.03 ± 2.33 mSv. Comet TM and percentage frequency of MNBC % was 65.22 ± 35.42 and 18.55 ± 10.14, respectively in the patients injected with contrast and 42.49 ± 28.52 and 13.76 ± 7.52 for non-contrast group. Significant increase in DNA damage was observed in the contrast group as compared to non-contrast group. Significant association was observed between patient weight, contrast volume and TM and MNBC%. Baseline parameters of the patients did not show significant correlation with TM and MNBC%. Conclusion: The patients undergoing contrast-enhanced WB PET/CT investigations have demonstrated higher DNA damage. The DNA damage was also observed to be more in heavier patients. The other baseline parameters of patients like age, sex, CBG, serum creatinine did not show any correlation with DNA damage.

Aim: In a Nuclear Medicine department, the risk of external and internal contamination in radiation workers is much higher than in other medical radiation facilities. The risk associated with both types of contaminations should be quantified to estimate the radiation dose received by the personal. Here, we designed an in vitro model to see the impact of internal and external contamination of F-18 and Technetium-99 m (Tc-99 m) on DNA damages. Methodology: Chinese hamster lung fibroblast V79 was used for all of the experiments. Irradiation was performed internally and externally (scenarios activity is mixed with the cell line [Internal] and activity kept at 1 cm distance from cell line [external]) using two different diagnostic radioactive sources (Tc-99 m and F-18) of known quantity 37 MBq. Total cumulated activity (MBq-min) was calculated up to one half-life of sources for both internal and external setups. An alkaline single gel electrophoresis technique (comet assay) was used for DNA damage analysis. Olive tail moment (OTM) was used to characterize DNA damage. Results: We have not observed any significant difference (P > 0.05) in OTM between internal and external irradiation for cumulated activity presented before one half-life of both diagnostic isotopes. However, a significant difference in OTM was noted between internal and external irradiation for cumulated activity presented at one half-life of radioactive sources (P < 0.05). DNA damage with internal exposure was found to be 17.28% higher for F-18 and 23% higher for Tc-99 m than external exposure at one half-life of radioactive sources. Overall, we noted greater DNA damage in F-18 as compared to Tc-99 m. Conclusions: Our in vitro study practically demonstrated that internal contamination is more hazardous than external exposure. [ABSTRACT FROM AUTHOR]

Background: Comet assay is a rapid and easiest method for measuring radiation-induced double-strand break in eukaryotic cells. On other side γH2AX is a sensitive biomarker for detecting DNA DSBs at very low dose radiation exposure. Objectives: In this study, we tried to investigate the biological effects at the low dose of gamma radiation after longer gamma exposer by using 18F. DNA damage was compared using comet assay and γH2AX assay. Methods: V79 cell line irradiated using 26.86 mGy for 30 min. Comet assay was performed at alkaline condition and checked after EtBr staining under fluorescent microscope and in the γH2AX assay, mouse monoclonal antiphosphohistone- H2ax used as a primary antibody and Alexa Fluor 488 goat anti-mouse IgG as secondary antibody. Results: DSBs were analyzed using comet tail moment and the number of γH2AX foci formation. Average TM was 42.64 ±18.46 and the number of γH2AX foci was 9.14 ±3.68. Our observation shows number of γH2AX foci value is lower than the comet result. Although comet result was heterogenic response and the number of comets presenting cell was varied at each slide preparation, which means the frequency distribution of comet presenting cells is not equal at a single time point. Some cells within a population shows no damage, whereas others show extensive DNA breakage. Conclusions Our comparative study shows comet assay is not very reliable technique at low dose exposure and may give false positive results in comparison to γH2AX assay. [ABSTRACT FROM AUTHOR]