title: Susceptibility artefact correction using dynamic graph cuts: application to neurosurgery.
abstract: Echo Planar Imaging (EPI) is routinely used in diffusion and functional MR imaging due to its rapid acquisition time. However, the long readout period makes it prone to susceptibility artefacts which results in geometric and intensity distortions of the acquired image. The use of these distorted images for neuronavigation hampers the effectiveness of image-guided surgery systems as critical white matter tracts and functionally eloquent brain areas cannot be accurately localised. In this paper, we present a novel method for correction of distortions arising from susceptibility artefacts in EPI images. The proposed method combines fieldmap and image registration based correction techniques in a unified framework. A phase unwrapping algorithm is presented that can efficiently compute the B0 magnetic field inhomogeneity map as well as the uncertainty associated with the estimated solution through the use of dynamic graph cuts. This information is fed to a subsequent image registration step to further refine the results in areas with high uncertainty. This work has been integrated into the surgical workflow at the National Hospital for Neurology and Neurosurgery and its effectiveness in correcting for geometric distortions due to susceptibility artefacts is demonstrated on EPI images acquired with an interventional MRI scanner during neurosurgery.
authors.affiliation: Centre for Medical Image Computing, University College London, London, UK. Electronic address: p.daga@cs.ucl.ac.uk.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Daga
authors.affiliation: Centre for Medical Image Computing, University College London, London, UK.
authors.forename: Tejas
authors.initials: T
authors.lastname: Pendse
authors.affiliation: Centre for Medical Image Computing, University College London, London, UK.
authors.forename: Marc
authors.initials: M
authors.lastname: Modat
authors.affiliation: National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: White
authors.affiliation: National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Mancini
authors.affiliation: Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK.
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Winston
authors.affiliation: National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: McEvoy
authors.affiliation: National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK.
authors.forename: John
authors.initials: J
authors.lastname: Thornton
authors.affiliation: National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK.
authors.forename: Tarek
authors.initials: T
authors.lastname: Yousry
authors.affiliation: Centre for Medical Image Computing, University College London, London, UK.
authors.forename: Ivana
authors.initials: I
authors.lastname: Drobnjak
authors.affiliation: Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK.
authors.forename: John S
authors.initials: JS
authors.lastname: Duncan
authors.affiliation: Centre for Medical Image Computing, University College London, London, UK; Dementia Research Centre, Institute of Neurology, University College London, London, UK.
authors.forename: Sebastien
authors.initials: S
authors.lastname: Ourselin
mesh_terms: D000465:Algorithms; D016477:Artifacts; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods*; D019635:Neurosurgical Procedures; D019047:Phantoms, Imaging; D012984:Software; D035501:Uncertainty
keywords: Graph cuts; Image-guided neurosurgery; Magnetic resonance imaging; Phase unwrapping; Susceptibility