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> Hi Jerome, > > yes, SPM will probably slower on 4D files than on 3D files. Also > it will > be slower on .nii files than on .hdr/.img pairs. The reason is, > that for > combined header and data files (as in 3D .nii and 4D cases) SPM > needs > something like random-write-access to your file to store small > bits of > information. This is more expensive in terms of I/O time > (especially on > large disks/RAID systems/network file storage) than storing 3D > data with > separate .hdr/.img files. However, storing one large file is more > efficient in terms of disk usage (if you have > partitioned/formatted your > disk to efficiently store large files). In short, there is no free > lunch, and you have to decide what is more important to you: > saving > time or saving disk space... > I've just investigated this because I am doing a transition of our > network > filesystem away from NFS and had to resolve some performance > issues as > well. > > Volkmar > > On Wed, 4 Apr 2007, Paul Macey wrote: > > > Hi Jérôme > > > > I just wrote something to split 4D to 3D; run the attached > script > > (cspm_im_4Dto3D, from SPM5 only) and it will prompt for a 4D > file to split. > > You can also use it in batch mode with a couple more options > (see help). The > > 3D files should be the same as in the 4D file, so I don't think > you will > > loose anything by converting. > > > > Best wishes, > > Paul > > > > Jérôme Redouté wrote: > >> Dear SPMers, > >> My parameters estimation process is extremely slow. Could > this slowness > >> be due to using a 4D-Niftii dataset? > >> In order to check that, I would like to convert my sw_xxxx.nii > 4D files > >> into a set of 3D files. > >> My questions are: > >> -SPM has a function to convert 3D -> 4D , but is the reverse > function>> available? Where can I find such a converter? > >> -These images are preprocessed (realignment, normalisation, > smoothing), do > >> I risk to lose these parameters by converting to 4D to 3D? > >> Thanks for your help > >> Jerome > >> > > > > -- > Volkmar Glauche > - > Department of Neurology [log in to unmask] > Universitaetsklinikum Freiburg Phone 49(0)761-270-5331 > Breisacher Str. 64 Fax 49(0)761-270-5416 > 79106 Freiburg http://fbi.uniklinik-freiburg.de/39_5Apr200714:26:[log in to unmask] |