• He Wang, Rencheng Zheng, Fei Dai, Qianfeng Wang, and Chengyan Wang.
• Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China.
• J Magn Reson Imaging. 2019 Dec 1; 50 (6): 1937-1947.

BackgroundLow signal-to-noise ratio (SNR) has been a major limiting factor for the application of higher-resolution diffusion-weighted imaging (DWI). Most of the conventional denoising models suffer from the drawbacks of shallow feature extraction and hand-crafted parameter tuning. Although multiple studies have shown the promising applications of image denoising using convolutional neural networks (CNNs), none of them have considered denoising multiple b-value DWIs using a multichannel CNN model.PurposeTo present a joint denoising CNN (JD-CNN) model to improve the SNR of multiple b-value DWI.Study TypeRetrospective technical development.PopulationTwenty healthy rats and two rats with clinically confirmed focal cortical dysplasia were included to evaluate the performance of the proposed method.Field Strength/Sequence11.7T MRI, a multiple b-values DWI sequence.AssessmentThe total variation (TV) and BM3D denoising methods were also performed on the same dataset for comparison. Peak SNR (PSNR) and normalized mean square error (NMSE) were calculated for the assessment of image qualities.Statistical TestsA paired Student's t-test was conducted to compare the diffusion parameter measurements between different approaches. P < 0.01 was considered statistically significant.ResultsSimulation results showed substantial improvement of image quality after JD-CNN denoising (PSNR of original image: 23.15 ± 1.77; PSNR of denoised image: 42.94 ± 2.12). The proposed method outperforms the state-of-the-art methods on high b-value DWIs in terms of PSNR (TV: 33.51 ± 0.83, BM3D: 35.12 ± 0.94, JD-CNN: 46.52 ± 0.98). In addition, the NMSE of the estimated apparent diffusion coefficient (ADC) reduces from 0.72 ± 0.13 to 0.45 ± 0.06 (P < 0.01) with the application of the JD-CNN model.Data ConclusionThe proposed method is able to remove noise with a wide range of noise levels in multiple b-value DWI and improve the diffusion parameter estimation. This shows potential clinical promise.Level Of Evidence2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:1937-1947.© 2019 International Society for Magnetic Resonance in Medicine.

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