ABSTRACT
Objective To investigate the effects of low contrast agent concentration and optimal monoenergetic image on myocardial image quality in dual source, dual energy coronary CT angiography (CCTA).Methods Sixty patients,who were clinically suspected of coronary heart disease and referred to perform dual energy CCTA examination,were prospectively collected between January and June 2016 in the first affiliated hospital of Xinjiang Medical University and then randomly divided into two groups with thirty cases in each group.Dual-energy CCTA was performed in both groups with the same parameters expect the iodine contrast agent concentration.The iopamidol concentrations were 370 and 320 mg/ml for groups A and B, respectively. The raw images of the two groups were reconstructed to get conventional mixed energy images and 60,65,70,75,80,85,90 keV single energy images,respectively labeled as group A1 to A8 and group B1 to B8.The CT attenuation,noise,signal-to-noise ratio(SNR)and contrast to noise ratio(CNR)were measured in images from groups A1 to A8 and B1 to B8. And the optimal monoenergetic image set was selected.Rank sum test was used to compare the CT value,noise,SNR and CNR between groups A1 to A8 and B1 to B8.The differences of above-mentioned parameters between A1 and B5 group,A5 group and B5 group were compared by independent sample t test.Results The differences of CT value,noise,SNR and CNR between groups A1 and A8, B1 and B8 were statistically significant (P<0.05). The CNR and SNR of group A5 were significantly higher than that of group A1,and the image noise of group A5 was lower than that of group A1(all P<0.05),and the images of A5 group(75 keV)were the optimal monoenergetic image. The SNR and CNR of the left ventricular lateral wall in group B5 were significantly higher than those in group B1,and the noise was lower than that in group B1(all P<0.05),and the image of B5 group(75 keV) was the optimal monoenergetic image. The difference of image noise between groups A1 and B5 was statistically significant(P<0.05),while the differences of SNR and CNR between these two groups were not significant(all P>0.05).The differences of image noise,SNR and CNR between groups A5 and B5 were not significant(all P>0.05).Conclusions The myocardial CCTA image quality by using iodine contrast agent (320 mg/ml) and optimal monoenergetic imaging (75 keV) is equivalent to that of conventional iodine contrast agent(370 mg/ml)mixed energy image.The strategy can effectively reduce the amount of contrast agent when meeting the needs of the clinical diagnosis.
ABSTRACT
Autophagy and apoptosis are both highly regulated biological processes that play essential roles in tissue homeostasis, development and diseases. Autophagy is also described as a mechanism of death pathways, however, the precise mechanism of how autophagy links to cell death remains to be fully understood. Beclin 1 is a dual regulator for both autophagy and apoptosis. In this study we found that Beclin 1 was a substrate of caspase-3 with two cleavage sites at positions 124 and 149, respectively. Furthermore, the autophagosome formation occurred, followed by the appearance of morphological hallmarks of apoptosis after staurosporine treatment. The cleavage products of Beclin 1 reduced autophagy and promoted apoptosis in HeLa cells and the cells in which Beclin 1 was stably knocked down by specific shRNA. In addition, the cleavage of Beclin 1 resulted in abrogating the interaction between Bcl-2 with Beclin 1, which could be blocked by z-VAD-fmk. Thus, our results suggest that the cleavage of Beclin 1 by caspase-3 may contribute to inactivate autophagy leading towards augmented apoptosis.