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Quantitative Assessment of Single-Image Super-Resolution in Myocardial Scar Imaging

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Quantitative Assessment of Single-Image Super-Resolution in Myocardial Scar Imaging
A novel, validated image fusion system that allows real-time integration of three-dimensional echocardiography and X-ray fluoroscopy for guidance of cardiac cacheterization. The system was validated in two stages: pre-clinical to determine function and validate accuracy, and in the clinical setting to assess clinical workflow feasibility and determine overall system accuracy.

Single-image super resolution is a process of obtaining a high-resolution image from a set of low-resolution observations by signal processing. While super resolution has been demonstrated to improve image quality in scaled down images in the image domain, its effects on the Fourier-based image acquisition technique, such as MRI, remains unknown. We performed high-resolution ex vivo late gadolinium enhancement (LGE) magnetic resonance imaging (0.4 × 0.4 × 0.4 mm3) in postinfarction swine hearts (n=24). The swine hearts were divided into the training set (n=14) and the test set (n=10), and in all hearts, low-resolution images were simulated from the high-resolution images. In the training set, super-resolution dictionaries with pairs of small matching patches of the high- and low-resolution images were created. In the test set, super resolution recovered high-resolution images from low-resolution images using the dictionaries. The same algorithm was also applied to patient LGE (n=4) to assess its effects. Compared with interpolated images, super resolution significantly improved basic image quality indices . Super resolution using Fourier-based zero padding achieved the best image quality. However, the magnitude of improvement was small in images with zero padding. Super resolution substantially improved the spatial resolution of the patient LGE images by sharpening the edges of the heart and the scar. In conclusion, single-image super resolution significantly improves image errors. However, the magnitude of improvement was relatively small in images with Fourier-based zero padding. These findings provide evidence to support its potential use in myocardial scar imaging.
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Authors

See complete bios of the authors in the full version of this article.
H AshikagaH Ashikaga
Dr. Ashikaga joined John Hopkins in 2012 as an Assistant Professor of medicine and biomedical engineering. He is an Attending Cardiac Electrophysiologist with Johns Hopkins Hospital. His research interests include cardiac electromechanical mapping, cardiovascular MRI/CT, mathematical modeling, cardiac biomechanics, and image-guided diagnosis and intervention.

H EstnerH Estner
Dr. Estner has been the Head of the Department for Clinical Electrophysiology, Ludwig-Maximilians University since 2011. Her research interests include cardiac mapping, cardiovascular MRI, and clinical studies including image-guided diagnosis and intervention.

D HerzkaD Herzka
Dr. Herzka joined the Johns Hopkins University School of Medicine, Baltimore, MD, USA, as an Assistant Professor of biomedical engineering in 2008. His current research focuses on MRI acquisition and reconstruction technique development. His interests include dynamic imaging with MRI, fast and high-resolution cardiac imaging, musculoskeletal system imaging, and fetal imaging.

E McVeighE McVeigh
Dr. McVeigh founded the Medical Imaging Laboratory, Department of Biomedical Engineering, as part of a Whitaker Development Award in 1991. In 1999, he joined the Laboratory of Cardiac Energetics with the NIH, Bethesda, to develop a research program in cardiovascular interventional MRI. he was appointed as a Massey Professor and Director of the Department of Biomedical Engineering, Johns Hopkins in 2007.

H HalperinH Halperin
Dr. Halperin is currently the David J. Carver Professor of medicine, and Professor of radiology and biomedical engineering with Johns Hopkins Medical Institutions, and is a Clinical Electrophysiologist with Johns Hopkins Hospital. He is the Co-Director of the Johns Hopkins Cardiovascular Imaging Center of Excellence, and the Director of Advanced Cardiovascular Life Support with Johns Hopkins Hospital.

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