• About
  • Policies
  • What is open access
  • Library
  • Contact
Advanced search
      View Item 
      •   BUIR Home
      • Scholarly Publications
      • Faculty of Engineering
      • Department of Electrical and Electronics Engineering
      • View Item
      •   BUIR Home
      • Scholarly Publications
      • Faculty of Engineering
      • Department of Electrical and Electronics Engineering
      • View Item
      JavaScript is disabled for your browser. Some features of this site may not work without it.

      Phase-correcting non-local means filtering for diffusion-weighted imaging of the spinal cord

      Thumbnail
      Embargo Lift Date: 2019-05-21
      View / Download
      1.8 Mb
      Author(s)
      Kafalı, Sevgi Gökçe
      Çukur, Tolga
      Sarıtaş, Emine Ülkü
      Date
      2018
      Source Title
      Magnetic Resonance in Medicine
      Print ISSN
      0740-3194
      Electronic ISSN
      1522-2594
      Publisher
      John Wiley
      Volume
      80
      Issue
      3
      Pages
      1020 - 1035
      Language
      English
      Type
      Article
      Item Usage Stats
      193
      views
      238
      downloads
      Abstract
      Purpose: DWI suffers from low SNR when compared to anatomical MRI. To maintain reasonable SNR at relatively high spatial resolution, multiple acquisitions must be averaged. However, subject motion or involuntary physiological motion during diffusion-sensitizing gradients cause phase offsets among acquisitions. When the motion is localized to a small region, these phase offsets become particularly problematic. Complex averaging of acquisitions lead to cancellations from these phase offsets, whereas magnitude averaging results in noise amplification. Here, we propose an improved reconstruction for multi-acquisition DWI that effectively corrects for phase offsets while reducing noise. Theory and Methods: Each acquisition is processed with a refocusing reconstruction for global phase correction and a partial k-space reconstruction via projection-onto-convex-sets (POCS). The proposed reconstruction then embodies a new phase-correcting non-local means (PC-NLM) filter. PC-NLM is performed on the complex-valued outputs of the POCS algorithm aggregated across acquisitions. The PC-NLM filter leverages the shared structure among multiple acquisitions to simultaneously alleviate nuisance factors including phase offsets and noise. Results: Extensive simulations and in vivo DWI experiments of the cervical spinal cord are presented. The results demonstrate that the proposed reconstruction improves image quality by mitigating signal loss because of phase offsets and reducing noise. Importantly, these improvements are achieved while preserving the accuracy of apparent diffusion coefficient maps. Conclusion: An improved reconstruction incorporating a PC-NLM filter for multi-acquisition DWI is presented. This reconstruction can be particularly beneficial for high-resolution or high-b-value DWI acquisitions that suffer from low SNR and phase offsets from local motion.
      Keywords
      Denoising
      Diffusion weighted imaging
      Motion
      Non-local means
      Phase correction
      Spinal cord
      Permalink
      http://hdl.handle.net/11693/50006
      Published Version (Please cite this version)
      https://doi.org/10.1002/mrm.27105
      Collections
      • Aysel Sabuncu Brain Research Center (BAM) 249
      • Department of Electrical and Electronics Engineering 4011
      • National Magnetic Resonance Research Center (UMRAM) 301
      Show full item record

      Browse

      All of BUIRCommunities & CollectionsTitlesAuthorsAdvisorsBy Issue DateKeywordsTypeDepartmentsCoursesThis CollectionTitlesAuthorsAdvisorsBy Issue DateKeywordsTypeDepartmentsCourses

      My Account

      Login

      Statistics

      View Usage StatisticsView Google Analytics Statistics

      Bilkent University

      If you have trouble accessing this page and need to request an alternate format, contact the site administrator. Phone: (312) 290 2976
      © Bilkent University - Library IT

      Contact Us | Send Feedback | Off-Campus Access | Admin | Privacy