Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 82, Issue 6, Pages 2273-2285Publisher
WILEY
DOI: 10.1002/mrm.27889
Keywords
convolutional neural networks; deep learning; hyperpolarized gas; image reconstruction; MRI
Funding
- National Natural Science Foundation of China [81625011, 81771917, 91859206, 81730048, 81825012]
- National Key RAMP
- D Program of China [2016YFC1304700]
- Key Research Program of Frontier Sciences, CAS [QYZDY-SSW-SLH018]
- Hubei Provincial Natural Science Foundation of China [2017CFA013, 2018ACA143]
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Purpose To fast and accurately reconstruct human lung gas MRI from highly undersampled k-space using deep learning. Methods The scheme was comprised of coarse-to-fine nets (C-net and F-net). Zero-filling images from retrospectively undersampled k-space at an acceleration factor of 4 were used as input for C-net, and then output intermediate results which were fed into F-net. During training, a L2 loss function was adopted in C-net, while a function that united L2 loss with proton prior knowledge was used in F-net. The 871 hyperpolarized Xe-129 pulmonary ventilation images from 72 volunteers were randomly arranged as training (90%) and testing (10%) data. Ventilation defect percentage comparisons were implemented using a paired 2-tailed Student's t-test and correlation analysis. Furthermore, prospective acquisitions were demonstrated in 5 healthy subjects and 5 asymptomatic smokers. Results Each image with size of 96 x 84 could be reconstructed within 31 ms (mean absolute error was 4.35% and structural similarity was 0.7558). Compared with conventional compressed sensing MRI, the mean absolute error decreased by 17.92%, but the structural similarity increased by 6.33%. For ventilation defect percentage, there were no significant differences between the fully sampled and reconstructed images through the proposed algorithm (P = 0.932), but had significant correlations (r = 0.975; P < 0.001). The prospectively undersampled results validated a good agreement with fully sampled images, with no significant differences in ventilation defect percentage but significantly higher signal-to-noise ratio values. Conclusion The proposed algorithm outperformed classical undersampling methods, paving the way for future use of deep learning in real-time and accurate reconstruction of gas MRI.
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