title: A method of generalized projections (MGP) ghost correction algorithm for interleaved EPI.
abstract: Investigations into the method of generalized projections (MGP) as a ghost correction method for interleaved EPI are described. The technique is image-based and does not require additional reference scans. The algorithm was found to be more effective if a priori knowledge was incorporated to reduce the degrees of freedom, by modeling the ghosting as arising from a small number of phase offsets. In simulations with phase variation between consecutive shots for n-interleaved echo planar imaging (EPI), ghost reduction was achieved for n = 2 only. With no phase variation between shots, ghost reduction was obtained with n up to 16. Incorporating a relaxation parameter was found to improve convergence. Dependence of convergence on the region of support was also investigated. A fully automatic version of the method was developed, using results from the simulations. When tested on in vivo 2-, 16-, and 32-interleaved spin-echo EPI data, the method achieved deghosting and image restoration close to that obtained by both reference scan and odd/even filter correction, although some residual artifacts remained.
authors.affiliation: Academic Unit of Radiology, University of Sheffield, Royal Hallamshire Hospital, Sheffield S10 2JF, UK. k.j.lee@sheffield.ac.uk
authors.forename: K J
authors.initials: KJ
authors.lastname: Lee
authors.forename: N G
authors.initials: NG
authors.lastname: Papadakis
authors.forename: D C
authors.initials: DC
authors.lastname: Barber
authors.forename: I D
authors.initials: ID
authors.lastname: Wilkinson
authors.forename: P D
authors.initials: PD
authors.lastname: Griffiths
authors.forename: M N J
authors.initials: MN
authors.lastname: Paley
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology; D003198:Computer Simulation; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation; D015233:Models, Statistical; D019047:Phantoms, Imaging