[Insight-users] Hints to create a known deformation image - Deformable Image registration?

[Luis Ibanez]

On Tue, Nov 3, 2009 at 7:56 AM, motes motes <mort.motes at gmail.com> wrote:
> On Mon, Nov 2, 2009 at 12:06 AM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
>> Hi Motes,
>>
>> 1) Lena is certainly not the best motif for evaluating a deformable
>>     registration process. You may want to use a grid image with
>>     about four time the density of lines of the BSpline grid, and
>>     lines that are more than 2 pixels apart.
>>
>>     The reason why you want lines to be more than 2 pixels apart
>>     is to avoid aliasing when you resample the image using the
>>     deformation field.
>
>
> I am still a bit confused about this suggestion. Do you suggestion to
> use the grid image as input to the registration process?
>
> Why is Lena not a good example? I have made a deformable version of
> the original Lena which I use as a moving image. I thought that the
> more varying intensities an image contains the higher the chance of
> alignment.
>
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Hi Motes,

1) Nope, I wasn't suggesting to use the grid image as input
    to the registration process. On the contrary, I meant to
    discourage you from doing so.

    The grid image is good for illustrating the effect of the
    resulting deformation field.

    Typically what you want to do is to take two real images
    register them, and the use the resulting deformation field
    to resample the grid image. This will give you an idea of
    the deformation that is applied to the moving image when
    mapped in to the coordinate system of the fixed image.


2) Lenna is not a good example, "if" your real goal is to
    perform registration of medical images.

    The reason is that the spatial distribution of intensities in
    the image of Lenna is quite different from what you see
    in a medical image.

    Lenna's image has large regions where the interaction of
    the skin normal with lightning result in gradual variation
    of intensity.  This type of intensity gradient is rare in medical
    images of internal organs (except maybe when due to the
    inhomogeneity of the field in an MRI image).


 Regards,


       Luis