Does different image parameters affect image registration?

I am currently trying to register 2, 3D CT images of a human tibia. I have implemented imregister to complete this task. When I register the right to left leg of the same individual from the same day, the registration is excellent. However, when I register the left leg to the left leg of the same individual 3 years later the registration is very poor. The CT collected a slice every 0.4mm but I noticed that the image spacing was different in the other 2 planes. One CT scan had image spacing of 0.156 x 0.156 x 0.4 while the other was 0.195 x 0.195 x 0.4. Could this explain the poor registration? Is there a way to specific the image spacing to improve the registration? Please let me know if my question is unclear or if you need more information/code/images. Thank you.

Answer 1

[Alex Taylor]

Hi Colleen, I would recommend you take a look at the following example that ships with the Image Processing Toolbox:

http://www.mathworks.com/help/images/examples/registering-multimodal-3-d-medical-images.html

It shows how spatial referencing objects can be used to specify the resolution of your images in each dimension and improve 3-D registration results with imregister.

In your case, the first CT image you described would have a spatial referencing object defined as:

 Rct = imref3d(size(yourImage), 0.156,  0.156, 0.4);

Where yourImage is the variable that contains the first CT image.

Passing spatial referencing information can be very useful in getting imregister/imregtform to converge.

[Colleen]

Hi Alex, this worked very well and solved my problem! Now, the registration is very good. Thanks for all your help and the suggested example. It was very helpful.

[Alex Taylor]

Collen,

I'm happy to hear that! Thanks for letting me know it worked out.

Answer 2

[Ashish Uthama]

Difference in spatial resolution differece might explain the poor registration.

You could specify the image spacing using using imref3d and use it with imregister.