How can I resample an image without changing the matrix size in MATLAB?

I have two DICOM images both have the same matrix sizes 512X512, however in the DICOM metadata I realized that one image has 0.4mm/pixel and the other is 0.79mm/pixel. I resampled 0.79mm/pixel image to 0.4mm/pixel using imresample.m (written by Omer Demirkayabut)but my matrix size changed to 992x992. Is there any way I can perform the resampling without changing the matrix size? I would really appreciate it if someone can help me. Thanks!

Answer 1

[Jan]

The question is not meaningful: The images are matrices only and do not contain the information of the resolution. Therefore you cannot resample the resolution, but only change the size of the matrix - and this cannot happen without changing the size of the matrix.

I guess, the problem is your assumption that a resampling is required. Please explain the actual problem in detail.

[Walter Roberson]

512 pixels at 0.4mm per pixel is 204.8 mm.

512 pixels at 0.79mm per pixel is 404.48 mm.

Therefore the two images cover different areas. But you are trying to treat them as if they covered the same area. That is not going to work.

[Slim]

Yes I understand the images are matrices only,I should have added that they are both DICOM images so I have the DICOM metadata for both and thats how I realized they had different resolutions. So I want to know if there is a way I can change the 0.79mm/pixel image to 0.4mm/pixel and still maintain the matrix size?

[Walter Roberson]

You could crop the expanded matrix, possibly at an arbitrary or random section. If the portion to be cropped is not to be arbitrary you might want to do something like image registration