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Deep learning–based image restoration algorithm for coronary CT angiography



The purpose of this study was to compare the image quality of coronary computed tomography angiography (CTA) subjected to deep learning–based image restoration (DLR) method with images subjected to hybrid iterative reconstruction (IR).


We enrolled 30 patients (22 men, 8 women) who underwent coronary CTA on a 320-slice CT scanner. The images were reconstructed with hybrid IR and with DLR. The image noise in the ascending aorta, left atrium, and septal wall of the ventricle was measured on all images and the contrast-to-noise ratio (CNR) in the proximal coronary arteries was calculated. We also generated CT attenuation profiles across the proximal coronary arteries and measured the width of the edge rise distance (ERD) and the edge rise slope (ERS). Two observers visually evaluated the overall image quality using a 4-point scale (1 = poor, 4 = excellent).


On DLR images, the mean image noise was lower than that on hybrid IR images (18.5 ± 2.8 HU vs. 23.0 ± 4.6 HU, p < 0.01) and the CNR was significantly higher (p < 0.01). The mean ERD was significantly shorter on DLR than on hybrid IR images, whereas the mean ERS was steeper on DLR than on hybrid IR images. The mean image quality score for hybrid IR and DLR images was 2.96 and 3.58, respectively (p < 0.01).


DLR reduces the image noise and improves the image quality at coronary CTA.

Key Points

• Deep learning–based image restoration is a new technique that employs the deep convolutional neural network for image quality improvement.

• Deep learning–based restoration reduces the image noise and improves image quality at coronary CT angiography.

• This method may allow for a reduction in radiation exposure.

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Contrast-to-noise ratio


Computed tomography angiography


Deep convolutional neural network


Deep learning–based image restoration


Edge rise distance


Edge rise slope


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The authors state that this work has not received any funding.

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Corresponding author

Correspondence to Fuminari Tatsugami.

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The scientific guarantor of this publication is Kazuo Awai.

Conflict of interest

Kazuo Awai received a research grant from Canon Medical Systems Co. Ltd. Zhou Yu, Jian Zhou, and Yujie Lu are employees of Canon Medical Research USA. The other authors declare that they have no conflict of interest.

Statistics and biometry

No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.


• retrospective

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• performed at one institution

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Tatsugami, F., Higaki, T., Nakamura, Y. et al. Deep learning–based image restoration algorithm for coronary CT angiography. Eur Radiol 29, 5322–5329 (2019).

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  • Computed tomography angiography
  • Cardiac imaging techniques
  • Artificial intelligence
  • Image enhancement