[Mristudio-users] switching between images of different voxel sizes

[susumu mori]

Hi Andreas,

There are basically two types of files; those with and without header
information. Raw and Rec files are raw formats without header. So, every
time you open them, you have to tell DtiStudio about their image dimensions.
If you find anything wrong about image dimensions, it is either you
specified the wrong parameters or you didn't specify and DtiStudio simply
used parameters of the previous data (DtiStudio assumes the parameter of the
new data are the same as the previous ones if you don't specify).

Because RAW and Rec files do not contain image dimension information, the
dimension information you had in Analyze (i.e. 0.86mm) is lost. If you find
the image resolution is 1mm later when you load Rec, that means you
specified so when you load the Rec (e.g. matrix size is 256x256 and FOV is
256x256 in the data loading window). In this case, you simply had to type in
correct FOV (e.g. 240x240).

DtiStudio doesn't have functions to change dimensions. So before and after
data processing, the dimensions should remain the same. If your image looks
blurrier, the only reason I can think of is due to image co-registration.

The same goes for the number slices. Analyze format contains this
information but Rec/RAW don't. There is a field to specify the number of the
slices in the initial data loading window. If you don't specify this field,
it keeps the information from the previous session. If the number of the
slices are 55, then you have to explicitly type "55" or choose "All slices".

On Fri, Jul 15, 2011 at 7:35 PM, Andreas Buchmann <buchmann2 at wisc.edu>wrote:

>  Dear MRI-Studio experts,****
>
> ** **
>
> I'm using DTI Studio version 3.0.2.****
>
> When I open images with a certain voxel size and later swap to images with
> a different voxel size, DTI Studio still uses the old voxel size.****
>
> For example, analyze images correctly shown in 0.86mm in-plane resolution
> were saved as 1x1mm voxels in rec format (but with correct slice thickness,
> which changed too), so the images were blurred in xy-plane.****
>
> ** **
>
> Earlier, I observed a similar problem with defining image parameters in the
> 'DTI mapping' tab: for example, the program switched some parameters
> automatically to the new image type, leaving others according to the old
> images, which lead to inconsistencies (for example, 39 slices, but the slice
> number went from 0 to 54).****
>
> ** **
>
> I solved the problem by reading in the new image type several times. Is
> there a less cumbersome procedure?****
>
> ** **
>
> Many thanks****
>
> Andreas****
>
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