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Dear Bas We have only ever implemented the FieldMap toolbox for the AP/PA phase-encode direction. We don't have any plans to collect data with an LR/RL phase-encode direction in the immediate future so we currently don't intend to update the toolbox for this. However, in theory it should be possible to tweak the toolbox to work for LR phase-encode direction. If you then plan to use the Realign and Unwarp option to apply the fieldmap, you will also need to tweak this. Unfortunately, I think both of these tasks (especially the latter) could be quite fiddly. If you decide to go ahead with the modifications, I strongly recommend you acquire phantom data in which there is an obvious distortion (e.g. apply an additional shim in your phase-encode direction). You can then use this to test what you've done. Best wishes Chloe On Mon, June 9, 2008 19:59, Bas Neggers wrote: > Dear list, > > > I am trying to use the fieldmap SPM5 toolbox to correct geometric > distortions for coronal slices of high resolution (2x2x2) 2DEPI data. The > 2DEPI acquisition (on a Philips Achieva MR scanner) is accelerated > with SENSE (eg, sparse K-space sampling) to decrease distortion. This > helps, but is not enough due to long readout in case of high-resolution > data. Phase encoding was in the LR direction. This is the only option, > because SENSE acceleration can't be done FH since most SENSE headcoil does > not have opposing coils in that direction. > > Now I read in the manual that the Fieldmap toolbox is designed for axial > slices with phase encoding either AP or PA. Would it be possible to tweak > the fieldmap toolbox to do corrections for coronal slices the right way? > The only message I found with a similar question was: > http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind04&L=spm&O=D&F=&I=-3&S=&P > =306371 > but unfortunately I could not find an answer... > > I tried to simulate SENSE readout when acquiring the required phase maps > at 2 echo times by doubling voxel size in the phase encoding direction, or > by adding a 2nd shot. That seems to have worked. > > Any help would be appreciated! > > > Cheers, > > > Bas > > > -- > -------------------------------------------------- > Dr. S.F.W. Neggers > Division of Brain Research > Rudolf Magnus Institute for Neuroscience > Utrecht University Medical Center > Visiting : Heidelberglaan 100, 3584 CX Utrecht > Room B.01.1.03 > Mail : Huispost B.01.206, P.O. Box 85500 > 3508 GA Utrecht, the Netherlands > Tel : +31 (0)30 2509609 > Fax : +31 (0)30 2505443 > E-mail : [log in to unmask] > Web : http://www.fmri.nl/people/bas.html > -------------------------------------------------- > > -- Dr Chloe Hutton Wellcome Trust Centre for Neuroimaging Institute of Neurology University College London 12 Queen Square London WC1N 3BG United Kingdom Tel. +44-20-7833-7478, (internal ext 4368) Fax +44-20-7813-1420 [log in to unmask]