Although normally used for group-wise registration, Dartel can also be
used to register images in a pairwise way (which is just a group-wise
registration with n=2). You can get it to write out Jacobian
determinants, but you'd get two of these for the two images, which
would need combining in some way.
Best regards,
-John
On 21 October 2010 17:54, Greg Book <[log in to unmask]> wrote:
> Thanks for the suggestions. I've played with DARTEL a little, but I'm not
> sure it will give me what I'm looking for. I'm interested in knowing the
> displacement of each voxel as image A is deformed to image B. I'm not
> terribly interested in groups and mean images, but I'll create those
> if necessary.
> Does DARTEL generate jacobian transforms in the same way that HDW does?
>
> On Thu, Oct 21, 2010 at 11:39 AM, John Ashburner <[log in to unmask]>
> wrote:
>>
>> Given the magnitudes of the displacements, Dartel would probably do a
>> better job with these images. However, if you want to try to achieve
>> much greater deformations with HDW, then you could try reducing the
>> amount of regularisation and increasing the number of iterations.
>>
>> Best regards,
>> -John
>>
>> On 21 October 2010 16:35, Greg Book <[log in to unmask]> wrote:
>> > I've been using HDW for a little while and been able to do most of what
>> > I
>> > want, however I'm not able to get the warps quite the way I need them.
>> > I have some CT data that I cropped to expose the structures of interest.
>> > These images are 80x80x80 mm. (1 voxel = 1 mm). Differences between
>> > structures in the images are on the order of 5mm, so I was hoping that
>> > the
>> > images would be warped internally by 5 voxels. However, after warping,
>> > voxels in the warped image are only displaced by about 1mm... so in the
>> > end
>> > the structures don't match up between two warped images and are still
>> > 4mm
>> > apart from where they should be.
>> >
>> > I'm attempting to warp the aorta, so I'm basically trying to warp a 20mm
>> > diameter tube to a 25mm diameter tube. Is this something that HDW can
>> > do?
>> > I'm wondering how strong the warping is, and how I can adjust it? Should
>> > I
>> > leave the CT images at 256x256x140.
>> >
>> > The 2D circle to square warping in Chapter 4 of the human brain function
>> > book is exactly the kind of warping effect I'm looking for.
>> >
>
>
|