Radiation dose reduction using deep learning-based image reconstruction for a low-dose chest computed tomography protocol: a phantom study.

Background: The aim of this study was to compare the dose reduction potential and image quality of deep learning-based image reconstruction (DLIR) with those of filtered back-projection (FBP) and iterative reconstruction (IR) and to determine the clinically usable dose of DLIR for low-dose chest computed tomography (LDCT) scans. Methods: Multi-slice computed tomography (CT) scans of a chest phantom were performed with various tube voltages and tube currents, and the images were reconstructed using seven methods to control the amount of noise reduction: FBP, three stages of IR, and three stages of DLIR. For subjective image analysis, four radiologists compared 48 image data sets with reference images and rated on a 5-point scale. For quantitative image analysis, the signal to noise ratio (SNR), contrast to noise ratio (CNR), nodule volume, and nodule diameter were measured. Results: In the subjective analysis, DLIR-Low (0.46 mGy), DLIR-Medium (0.31 mGy), and DLIR-High (0.18 mGy) images showed similar quality to the FBP (2.47 mGy) image. Under the same dose conditions, the SNR and CNR were higher with DLIR-High than with FBP and all the IR methods (all P<0.05). The nodule volume and size with DLIR-High were significantly closer to the real volume than with FBP and all the IR methods (all P<0.001). Conclusions: DLIR can improve the image quality of LDCT compared to FBP and IR. In addition, the appropriate effective dose for LDCT would be 0.24 mGy with DLIR-High.

Cardioprotective Effects of Omega-3 Polyunsaturated Fatty Acids: Dichotomy between Experimental and Clinical Studies.

The high-fat diet of North Americans has a major impact on cardiovascular disease occurrence. Notably, fatty acids have been identified as important factors that could modulate such diseases, especially myocardial infarction (MI). Experimentally, omega-3 polyunsaturated fatty acids (PUFA) have demonstrated positive effects on cardiovascular disorders and have also shown cardioprotection by decreasing MI size. Although many animal experiments have clearly established the benefits of omega-3 PUFA, clinical studies have not reached similar conclusions. In fact, the findings of recent clinical investigations indicate that omega-3 PUFA play only a minor role in cardiovascular health. This dichotomy between experimental and clinical studies may be due to different parameters that are not taken into account in animal experiments. We have recently observed that the high consumption of omega-6 PUFA results in significant attenuation of the beneficial effect of omega-3 PUFA on MI. We believe that part of the dichotomy between experimental and clinical research may be related to the quantity of omega-6 PUFA ingested. This review of the data indicates the importance of considering omega-6 PUFA consumption in omega-3 PUFA studies.

A high omega-3 fatty acid diet rapidly changes the lipid composition of cardiac tissue and results in cardioprotection.

The present study was designed to ascertain the effects of 3 diets with different omega-3/6 fatty acid ratios on infarct size and the modifications that these diets induce in the lipid composition of cardiac tissue. Sprague-Dawley rats were fed omega-3/6 fatty acid diets with 1:1, 1:5, or 1:20 ratios for at least 10 days, followed by occlusion of the left anterior descending artery for 40 min and 24 h of reperfusion. Infarct size was significantly smaller in the 1:1 group than in the other groups. Significantly higher concentrations of the omega-3 fatty acids eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid were found in the 1:1 group than in the other groups. Omega-6 polyunsaturated fatty acid levels were similar between groups, although they were higher in the 1:5 and 1:20 groups than in the 1:1 group. Margaric acid concentrations were higher in the 1:1 group than in the other groups. Docosahexaenoic acid levels in cardiac tissue and infarct size were significantly correlated with no other significant links being apparent. The present study indicated that a 1:1 omega-3/6 fatty acid ratio protected against ischemia and was associated with increased omega-3 fatty acid composition of cardiac tissue.