Dear SPM-group,
We are currenlty planning to make a voxel-by-voxel statistical comparison
of ADC maps between healthy subjects and patients with epilepsy.
The approach we use is similar to that described in:
Diffusion tensor imaging of cryptogenic and acquired partial epilepsies.
Rugg-Gunn FJ, Eriksson SH, Symms MR, Barker GJ, Duncan JS.
Brain. 2001 Mar;124(Pt 3):627-36.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?
cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11222461
Using the mean ADC-map and the standard deviation ADC-map of the healthy
volunteers we are able to find voxels in the ADC map of each patient
individually that significantly (P < 0.001) deviate from the healthy group.
However, we also want to correct for multiple comparisons, using a
corrected P value P < 0.05). (with reference (Friston et al 1994))
Our initial thought was to use spm_est_smoothness.m & spm_resels.m
Using a temporal lobe mask, we should be able to obtain a FWHM estimate for
the temporal lobe area of each ADC-map, and after that a resel count for
the temporal lobe. Then, we would apply a Bonferroni correction with the
number of resels in stead of the number of voxels.
However, if we try to obtain FWHM and RPV-file, using spm_est_smoothness on
a normalized ADC map with a temporal lobe mask, we do not get reasonable
FWHM estimates (the order of magnitude is 10^-30mm, in stead of an expected
5 mm). Therefore this doen't seem to work.
Does anyone know how to proceed, or what other SPM-files to use?
Your help is greatly appreciated,
With kind regards,
Jaap Jansen
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J.F.A. Jansen, M.Sc.
Ph.D. Student
Department of Radiology
University Hospital Maastricht
Prof. Debyelaan 25
P.O. box 5800
6202 AZ Maastricht
The Netherlands
Phone: +31 43 38 76984
Fax: +31 43 38 76909
Email: [log in to unmask]
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