• K J Lee, N G Papadakis, D C Barber, I D Wilkinson, P D Griffiths, and M N J Paley.
• Academic Unit of Radiology, University of Sheffield, Royal Hallamshire Hospital, Sheffield S10 2JF, UK. k.j.lee@sheffield.ac.uk
• IEEE Trans Med Imaging. 2004 Jul 1; 23 (7): 839-48.

AbstractInvestigations 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.

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