Deep Learning Approach for Generating MRA Images From 3D Quantitative Synthetic MRI Without Additional Scans.
OBJECTIVES Quantitative synthetic magnetic resonance imaging (MRI) enables synthesis of various contrast weighted images as well as simultaneous quantification of T1 and T2 relaxation times and proton density. However, to date, it has been challenging to generate magnetic resonance angiography (MRA) images with synthetic MRI. The purpose of this study was to develop a deep learning algorithm to generate MRA images based on 3D synthetic MRI raw data. MATERIALS AND METHODS Eleven healthy volunteers and 4 patients with intracranial aneurysms were included in this study. All participants underwent a time of flight (TOF) MRA sequence and a 3D QALAS synthetic MRI sequence. The 3D QALAS sequence acquires 5 raw images, which were used as the input for a deep learning network. The input was converted to its corresponding MRA images by a combination of a single convolution and a U net model with a 5 fold cross validation, which were then compared with a simple linear combination model. Image quality was evaluated by calculating the peak signal to noise ratio (PSNR) structural similarity index measurements (SSIMs) and high frequency error norm (HFEN) These calculations were performed for deep learning MRA (DL MRA) and linear combination MRA (linear MR) relative to TOF MRA, and compared with each other using a nonparametric Wilcoxon signed rank test. Overall image quality and branch visualization, each scored on a 5 point Likert scale, were blindly and independently rated by 2 board certified radiologists. RESULTS Deep learning MRA was successfully obtained in all subjects. The mean PSNR, SSIM, and HFEN of the DL MRA were significantly higher, higher, and lower, respectively, than those of the linear MRA (PSNR, 35.3 0.5 vs 34.0 0.5, P 0.001; SSIM, 0.93 0.02 vs 0.82 0.02, P 0.001; HFEN, 0.61 0.08 vs 0.86 0.05, P 0.001) The overall image quality of the DL MRA was comparable to that of TOF MRA (4.2 0.7 vs 4.4 0.7, P 0.99) and both types of images were superior to that of linear MRA (1.5 0.6, for both P 0.001) No significant differences were identified between DL MRA and TOF MRA in the branch visibility of intracranial arteries, except for ophthalmic artery (1.2 0.5 vs 2.3 1.2, P 0.001) CONCLUSIONS Magnetic resonance angiography generated by deep learning from 3D synthetic MRI data visualized major intracranial arteries as effectively as TOF MRA, with inherently aligned quantitative maps and multiple contrast weighted images. Our proposed algorithm may be useful as a screening tool for intracranial aneurysms without requiring additional scanning time.
Investigative radiology