Radiation dose comparison between V/P-SPECT and CT-angiography in the diagnosis of pulmonary embolism.

PURPOSE: The aim of this study is to compare two routine protocols at our institution, CTPA and V/P-SPECT, in terms of radiation dose to the most exposed organs (lungs and breast) and to the embryo/fetus in the case of pregnant patients. METHODS: At our institution, the CTPA protocol includes a contrast enhanced CT (scan parameters: 100kVp, 700mA, 0.5s/rot, pitch 0.984) and in some cases a non-contrast enhanced CT acquisition (120kVp, 400mA, 0.5s/rot, pitch 1.375). In the V/P-SPECT protocol, ventilation SPECT was performed after inhalation of 99mTc-Technegas, reaching 30MBq in the lungs; perfusion was performed after intravenous administration of 60-120MBq of 99mTc-MAA. The absorbed doses (mGy) to lungs and breast from CTPA were estimated using the "ImPACT CT Patient Dosimetry Calculator". The embryo/fetus dose was estimated for different gestational stages (0-7, 8-12, 13-25 and 26-40weeks) using the web based calculation tool "COnceptus Dose Estimation" (CODE). Doses to organs and embryo/fetus from V/P-SPECT were estimated based on published dose data normalized to administered activity (mGy/MBq). RESULTS: Embryo/fetus absorbed doses are similar for CTPA and V/P-SPECT and bellow 1mGy. The calculated dose to the lungs (breast) was 1.3-10.6 (27-136) times higher from CTPA when compared with V/P-SPECT. CONCLUSION: For the diagnosis of PE in women, if both imaging modalities are available, it is recommended to proceed with V/P-SPECT rather than CTPA due to the considerably lower radiation dose to the breast.

The Warburg effect in mycobacterial granulomas is dependent on the recruitment and activation of macrophages by interferon-γ.

Granulomas are the hallmark of mycobacterial disease. Here, we demonstrate that both the cell recruitment and the increased glucose consumption in granulomatous infiltrates during Mycobacterium avium infection are highly dependent on interferon-γ (IFN-γ). Mycobacterium avium-infected mice lacking IFN-γ signalling failed to developed significant inflammatory infiltrations and lacked the characteristic uptake of the glucose analogue fluorine-18-fluorodeoxyglucose (FDG). To assess the role of macrophages in glucose uptake we infected mice with a selective impairment of IFN-γ signalling in the macrophage lineage (MIIG mice). Although only a partial reduction of the granulomatous areas was observed in infected MIIG mice, the insensitivity of macrophages to IFN-γ reduced the accumulation of FDG. In vivo, ex vivo and in vitro assays showed that macrophage activated by IFN-γ displayed increased rates of glucose uptake and in vitro studies showed also that they had increased lactate production and increased expression of key glycolytic enzymes. Overall, our results show that the activation of macrophages by IFN-γ is responsible for the Warburg effect observed in organs infected with M. avium.

Is ultraviolet radiation a synergistic stressor in combined exposures? The case study of Daphnia magna exposure to UV and carbendazim.

The toxicological assessment of chemical compounds released to the environment is more accurate when mixtures of chemicals and/or interactions between chemicals and natural stressors are considered. Ultraviolet radiation can be taken as a natural stressor since the levels of UV are increasing due to the decrease of its natural filter, the stratospheric ozone concentration. Therefore, a combination of chemical exposures and increasing UV irradiance in aquatic environments is likely to occur. In the current study, combined effects of carbendazim and ultraviolet radiation were evaluated, using selected life traits as endpoints on Daphnia magna. To design combined exposures, first single chemical and natural stressor bioassays were performed: a reproduction test with carbendazim and a reproduction, feeding inhibition and Energy budget test with ultraviolet radiation. Following single exposures, the combinations of stressors included exposures to UV radiation and carbendazim for a maximum exposure time of 4h, followed by a post-exposure period in chemically contaminated medium for a maximum of 15 days, depending on the endpoint, where the effects of the combined exposures were investigated. Statistical analyses of the data set were performed using the MixTox tool and were based on the conceptual model of Independent Action (IA) and possible deviations to synergism or antagonism, dose-ratio or dose-level response pattern. Both ultraviolet radiation and carbendazim as single stressors had negative impacts on the measured life traits of daphnids, a decrease on both feeding rates and reproduction was observed. Feeding rates and reproduction of D. magna submitted to combined exposures of ultraviolet radiation and carbendazim showed a dose-ratio deviation from the conceptual model as the best description of the data set, for both endpoints. For feeding inhibition, antagonism was observed when the UV radiation was the dominant item in combination, and for reproduction, synergism was observed when UV radiation dominated the exposure. From these results, the combined exposure of ultraviolet radiation and chemical compounds should also be considered for risk assessment as this study has shown that more severe effect than expected by single chemical assessment might be observed.