PET/CT image registartion

Hi, I am a learner. I have a 512x512x74 CT image with 0.3848x0.3848x3 mm voxel size and PET image,135x135x74 with 3x3x3mm voxel size. Please advise me on the PET/CT registration process with different dimensions and voxel sizes. I tried Resample volume but gives an error. Thank you.

If these were from a fairly modern PET/CT scanner, and you loaded via dicom and the headers were correct, then the images should have loaded in the correct patient space, no resampling needed.

Thank you ! The original PET images 256x256x74 with voxels size 1.59095x 1.59095 x74 were resized and convolved using Matlab then converted to nrrd format to add in the 3D slicer.

It’s likely that the matlab step lost the geometry information. You’ll need to trace the calculation and reconstruct the correct origin, spacing, and directions to make the volumes line up again.

Thank you. Yes, I have considered origin, direction and voxel size.

Screenshot 2023-07-15 174450

I have these two images to register, I am not sure if I need to change the origin before landmark registration. After registration, I am intending to see the dose (PET unit Gy) in the selected volume using segment editor and quantification. I will greatly appreciate your help! Thank you.

I guess I can use Resample scalar/vector/DWI volume module to change the origin through the Manual output parameter.