You're right - if BET detects negative values it makes them all positive
and fills up the (positive) intensity range. This is is because some other
programs used subsequently need positive values to work right.
You can avoid this either by using avwmaths to remove all your negative
numbers before running BET or by rescaling the output afterwards.
Cheers.
On Fri, 16 Apr 2004, Himachandra Chebrolu wrote:
> Hi All,
> When I'm using BET to extract the brains out,my input
> image data type is signed 16 bit integer and the data
> lies mostly in the range of -125 to 3871(Ideally data
> must be from 12 bits making the minimum and maximum
> values 0 and 4096).But after extraction the output of
> the BET has mimimum and maximum values of 0 and
> 32767.It is using all the 16 bits to represent data
> whereas I only want it represent data in 12 bits.Has
> anybody had a similar problem?How do you guys suggest
> about going arund this?
> Thanks,
> Hima.
>
>
>
>
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Stephen M. Smith DPhil
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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