Dear Xeuying
Just to add to that:
The probability values in the SPM Anatomy toolbox are actually stored in multiples of 25, i.e., a 10% probability has the grey value 25, a 20% probability has the grey value 50, and so on up to a grey value of 250 for 100% probability.
So once you decided on a threshold (e.g. > 40%),you have to determine the corresponding grey value cutoff (in this example > 100).
HOWEVER:
It has been shown, that the Maximum Probability Map (MPM) representations give better reflection of the underlying architecture than simple thresholding (Eickhoff et al., NI 2006). You might thus want to use the "Create ROI" function of the Anatomy Toolbox to create your masks rather than thresholded PMaps.
Best
Simon
> -----Ursprüngliche Nachricht-----
> Von: =?windows-1252?Q?Jan_Gl=E4scher?= <[log in to unmask]>
> Gesendet: 30.05.07 23:44:55
> An: [log in to unmask]
> Betreff: Re: [SPM] How to convert a probability map into an ordinary mask?
>
> Dear Xeuying,
>
> you can use the ImCalc button for this task (spm_imcalc.m). First, you have
> to determine a threshold, e.g. 0.5: voxel with probabilities above this
> threshold will be included, others will be excluded.
>
> Your probability image is the input image, the expression to use is i1>0.5
> (where 0.5 is your threshold).
>
> Cheers,
> Jan
>
> Xueying Zhang wrote:
> > Dear SPM users,
> >
> > I'm trying to convert the probability mask (e.g. Hippocampus_FD.img) in
> > the "Anatomy toolbox" to an ordinary mask.
> >
> > I appreciate it if you anyone help me.
> >
> >
> >
> > Sincerely yours,
> >
> > Xueying (Sherry) Zhang
> > --------------------------------------
> > Ph.D.
> > Department of Biomedical Engineering
> > SUNY at Stony Brook
> >
> > _________________________________________________________________
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> >
> >
>
> --
> Jan Gläscher, Ph.D. Div. Humanities & Social Sciences
> +1 (626) 395-4976 (office) Caltech, Broad Center, M/C 114-96
> +1 (626) 395-2000 (fax) 1200 California Blvd
> [log in to unmask] Pasadena, CA 91125
>
--
===================================
Dr. Simon B. Eickhoff
Institut für Neurowissenschaften und Biophysik - Medizin
Forschungszentrum Juelich
Leo-Brandt-Str. 5
52425 Juelich
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