Hi,
There are other interpolation schemes such as nearest neighbour
or sinc, but they each have some disadvantages too, and will
make one image qualitatively different from the other. The
smoothing is inherent in trilinear interpolation, some rather
ugly discontinuities occur with nearest neighbour and some
ringing and/or variable smoothing can occur with sinc.
An alternative is to transform both images to a half-way
point, this equalising the interpolation effects. This is
what is done in SIENA, and you can do the same by extracting
the forward and backward half-transformation matrices from
the output of "avscale" as run on your original transformation
matrices.
That's what I would recommend.
All the best,
Mark
> Hi,
> You can change the interpolation scheme to nearest neighbour.
> (Advanced options in the gui)
>
> Saad.
>
>
> On 2 Apr 2007, at 14:28, Oliver Singer wrote:
>
>> Hi,
>>
>> I am trying to realign FA-maps of one subject, who was scanned at
>> two different time points. After running BET I am using FLIRT for
>> realigning (rigid body transform, 6D OF) the B0 images (extracted
>> from the DTI data set) of the second measurement to the B0 images of
>> the first measurement and as secondary images to apply the
>> transform to I take the FA maps of the second measurement.
>> The realignment works fine, but the FA-map of the second
>> measuresment (the realigned one) was "smoothed" during the process.
>> Since the first FA-map was not processed, the two maps differ in
>> terms of their "resolution / smootheness".
>> Is there a way either to turn off the "smoothing" during the
>> realignment or to smoothe the first FA-map (which was not
>> transformed) in a similar way? (I do not want to realign all images
>> to a "standard brain" due to gross pathology)
>> Any help is appreciated,
>>
>> Yours , Oliver
>
> ------------------------------------------------------------------------
> ---
> Saad Jbabdi,
> Postdoctoral Research Assistant,
> Oxford University FMRIB Centre
>
> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222545 (fax 222717)
> [log in to unmask] http://www.fmrib.ox.ac.uk/~saad
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