title: Characterization and Correction of Geometric Distortions in 814 Diffusion Weighted Images.
abstract: BACKGROUND
  Diffusion Weighted Imaging (DWI), which is based on Echo Planar Imaging (EPI) protocols, is becoming increasingly important for neurosurgical applications. However, its use in this context is limited in part by significant spatial distortion inherent to EPI.
  
  
  METHODS
  We evaluated an efficient algorithm for EPI distortion correction (EPIC) across 814 DWI scans from 250 brain tumor patients and quantified the magnitude of geometric distortion for whole brain and multiple brain regions.
  
  
  RESULTS
  Evaluation of the algorithm's performance revealed significantly higher mutual information between T1-weighted pre-contrast images and corrected b = 0 images than the uncorrected b = 0 images (p < 0.001). The distortion magnitude across all voxels revealed a median EPI distortion effect of 2.1 mm, ranging from 1.2 mm to 5.9 mm, the 5th and 95th percentile, respectively. Regions adjacent to bone-air interfaces, such as the orbitofrontal cortex, temporal poles, and brain stem, were the regions most severely affected by DWI distortion.
  
  
  CONCLUSIONS
  Using EPIC to estimate the degree of distortion in 814 DWI brain tumor images enabled the creation of a topographic atlas of DWI distortion across the brain. The degree of displacement of tumors boundaries in uncorrected images is severe but can be corrected for using EPIC. Our results support the use of distortion correction to ensure accurate and careful application of DWI to neurosurgical practice.
authors.affiliation: School of Medicine, University of California San Diego, San Diego, California, United States of America.|Center for Theoretical and Applied Neuro-Oncology, University of California San Diego Moores Cancer Center, San Diego, California, United States of America.
authors.forename: Jeffrey Mark
authors.initials: JM
authors.lastname: Treiber
authors.affiliation: Multimodal Imaging Laboratory, University of California San Diego, San Diego, California, United States of America.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: White
authors.affiliation: School of Medicine, University of California San Diego, San Diego, California, United States of America.|Center for Theoretical and Applied Neuro-Oncology, University of California San Diego Moores Cancer Center, San Diego, California, United States of America.|Neurosciences Graduate Program, University of California San Diego, San Diego, California, United States of America.
authors.forename: Tyler Christian
authors.initials: TC
authors.lastname: Steed
authors.affiliation: Multimodal Imaging Laboratory, University of California San Diego, San Diego, California, United States of America.
authors.forename: Hauke
authors.initials: H
authors.lastname: Bartsch
authors.affiliation: Multimodal Imaging Laboratory, University of California San Diego, San Diego, California, United States of America.
authors.forename: Dominic
authors.initials: D
authors.lastname: Holland
authors.affiliation: Multimodal Imaging Laboratory, University of California San Diego, San Diego, California, United States of America.|Department of Radiology, University of California San Diego, San Diego, California, United States of America.
authors.forename: Nikdokht
authors.initials: N
authors.lastname: Farid
authors.affiliation: Multimodal Imaging Laboratory, University of California San Diego, San Diego, California, United States of America.|Department of Psychiatry, University of California San Diego, San Diego, California, United States of America.
authors.forename: Carrie R
authors.initials: CR
authors.lastname: McDonald
authors.affiliation: Center for Theoretical and Applied Neuro-Oncology, University of California San Diego Moores Cancer Center, San Diego, California, United States of America.|Department of Neurosurgery, University of California San Diego, San Diego, California, United States of America.
authors.forename: Bob S
authors.initials: BS
authors.lastname: Carter
authors.affiliation: Multimodal Imaging Laboratory, University of California San Diego, San Diego, California, United States of America.
authors.forename: Anders Martin
authors.initials: AM
authors.lastname: Dale
authors.affiliation: Center for Theoretical and Applied Neuro-Oncology, University of California San Diego Moores Cancer Center, San Diego, California, United States of America.|Department of Neurosurgery, University of California San Diego, San Diego, California, United States of America.
authors.forename: Clark C
authors.initials: CC
authors.lastname: Chen
mesh_terms: D000465:Algorithms; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D011859:Radiography