Background: When the heart rate of a patient exceeds the physical limits of a scanning device, even retrospective electrocardiography (ECG) gating technology cannot correct motion artifacts. The purpose of this study was to use deep learning methods to correct motion artifacts in coronary computed tomography angiography (CCTA) images acquired with retrospective ECG gating. Methods: To correct motion artifacts in CCTA images, we used a cycle Wasserstein generative adversarial network with a gradient penalty (WGAN-GP) to synthesize CCTA images without motion artifacts, and applied objective image indicators and clinical quantitative scores to evaluate the images. The objective image indicators included peak signal-to-noise ratio (PSNR), structural similarity (SSIM), and normalized mean square error (NMSE). For clinical quantitative scoring, we randomly selected 50 sets of images from the test data set as the scoring data set. We invited 2 radiologists from Zhongnan Hospital of Wuhan University to score the composite images. Results: In the test images, the PSNR, SSIM, NMSE and clinical quantitative score were 24.96±1.54, 0.769±0.055, 0.031±0.023, and 4.12±0.61, respectively. The images synthesized by cycle WGAN-GP performed better on objective image indicators and clinical quantitative scores than those synthesized by cycle least squares generative adversarial network (LSGAN), UNet, WGAN, and cycle WGAN. Conclusions: Our proposed method can effectively correct the motion artifacts of coronary arteries in CCTA images and performs better than other methods. According to the performance of the clinical score, correction of images by this method does not affect the clinical diagnosis. ^ ORCID: 0000-0003-0618-6240.

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In this paper, to realize a better adaptive method for the lightning electric field signal denoising, we firstly compared the decomposition results of three methods called the EMD (empirical mode decomposition), the CEEMDAN (complete ensemble empirical mode decomposition with adaptive noise), and the EWT (empirical wavelet transform) by artificial signals, respectively, and found that the EWT was better than the other two methods. Then, a MEWT (modified empirical wavelet transform) method based on the EWT was presented for processing the natural lightning signals data. By using our MEWT method, we processed three types of electric field signal data with different frequency bands radiated by the lightning step leader, the cloud pulse and the return stroke, respectively, and the VLF (very low frequency) lightning signals propagating different distances from 500 km to 3500 km, by using the data of the fast electric field change sensors from Nanjing Lightning Location Network (NLLN) in 2018 and the data of the fast electric field change sensors and the VLF electric antennas from the NUIST Wide-range Lightning Location System (NWLLS) in 2021. The results showed that our presented MEWT method could adaptively process different lightning signal data with different frequencies from the step leader, the cloud pulse, and the return stroke; for the lightning VLF signal data from 500 km to 3500 km, the MEWT also achieved a better noise reduction effect. After denoising the signal by using our MEWT, the detection ability of the fast electric field change sensor was improved, and more weak lightning signals could be identified.

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On December 31, 2019, the Wuhan Health Commission reported the discovery of an “unexplained” pneumonia for the first time; the pathogen was confirmed as novel coronavirus pneumonia (2019-nCoV) on January 7, 2020. As one of the important examination methods for the Corona Virus Disease 2019 (COVID-19), Computed Tomography (CT) examination plays an important role in the clinical discovery of suspected cases, diagnosis, and treatment review. This paper reviews the published papers in order to offer help in early clinical screening, disease diagnosis, disease severity determination and post-treatment review.