BACKGROUND AND PURPOSE: Accurate quantification of WM lesion load is essential for the care of patients with multiple sclerosis. We tested whether the combination of accelerated 3D-FLAIR and denoising using deep learning-based reconstruction could provide a relevant strategy while shortening the imaging examination.
MATERIALS AND METHODS:Twenty-eight patients with multiple sclerosis were prospectively examined using 4 implementations of 3D-FLAIR with decreasing scan times (4 minutes 54 seconds, 2 minutes 35 seconds, 1 minute 40 seconds, and 1 minute 15 seconds). Each FLAIR sequence was reconstructed without and with denoising using deep learning-based reconstruction, resulting in 8 FLAIR sequences per patient. Image quality was assessed with the Likert scale, apparent SNR, and contrast-to-noise ratio. Manual and automatic lesion segmentations, performed randomly and blindly, were quantitatively evaluated against ground truth using the absolute volume difference, true-positive rate, positive predictive value, Dice similarity coefficient, Hausdorff distance, and F1 score based on the lesion count. The Wilcoxon signed-rank test and 2-way ANOVA were performed.
RESULTS:Both image-quality evaluation and the various metrics showed deterioration when the FLAIR scan time was accelerated. However, denoising using deep learning-based reconstruction significantly improved subjective image quality and quantitative performance metrics, particularly for manual segmentation. Overall, denoising using deep learning-based reconstruction helped to recover contours closer to those from the criterion standard and to capture individual lesions otherwise overlooked. The Dice similarity coefficient was equivalent between the 2-minutes-35-seconds-long FLAIR with denoising using deep learning-based reconstruction and the 4-minutes-54-seconds-long reference FLAIR sequence.CONCLUSIONS: Denoising using deep learning-based reconstruction helps to recognize multiple sclerosis lesions buried in the noise of accelerated FLAIR acquisitions, a possibly useful strategy to efficiently shorten the scan time in clinical practice.ABBREVIATIONS: AVD ¼ absolute volume difference; dDLR ¼ denoising using deep learning-based reconstruction; DSC ¼ Dice similarity coefficient; HD ¼ Hausdorff distance; MS ¼ multiple sclerosis; PPV ¼ positive predictive value; TPR ¼ true-positive rate M ultiple sclerosis (MS) is the most common inflammatory disease of the central nervous system affecting young patients, 1 in which demyelination mediated by autoimmune mechanisms is spatially and temporally disseminated. MR imaging plays an essential role not only in the initial diagnosis of MS 2 but also in regular monitoring as a sensitive marker of disease activity for promptly switching therapy if progression is observed. 3 Life-long imaging follow-up is, therefore, required for most patients with MS. A short examination time is necessary to improve the patient's comfort and to cope with the high number of demands in imaging centers.