3 ms·

I can't speak to the clinical aspect of medical imaging but I've done some development with medical images. If you end up pursuing your diff concept here are a

I can't speak to the clinical aspect of medical imaging but I've done some development with medical images. If you end up pursuing your diff concept here are a few things which might help point you in the right area or give you some additional keywords when searching: 1. CT images measure densities of tissue (in Hounsfield units). 2. The images will first need to be aligned/registered/fused. There are different ways to do this but it can be difficult if the two scans were done with different protocols/hardware as the image resolutions and dimensions can differ but also anatomy regularly changes (not as much in the head area). 3. Fusions are often described as having a primary (unchanged) and a secondary (the image that's modified to align to the primary). 4. Fusions can be very basic rigid alignments (like moving one photo on top of another) or be fancy by moving voxels independently (often called deformable registration, like cutting a photo into squares and moving them) however these are difficult to evaluate for correctness. 5. Fusions are often viewed as a transparency overlay of one image on top of another (in the case of deformable it's the deformed image over top the primary). 6. After doing a fusion a subtraction can be performed to find the difference in image values (the densities). Best of luck and enjoy the field.

ska 6y ago
Adding a couple of hopefully helpful comments here. 1. There is a lot of terminological abuse in this area, but fusion is properly a display (or production of new images) technique, (co-) registration is the mapping of one image to another. 2. You almost certainly do not want deformative or even affine transforms in the registration of same patient bony anatomy in CT (because it is stereo-tactically accurate). You want a rigid transform here. Also because of CT you can rely on the units are meaningful so you don't need to normalize. 3. Because you are doing rigid transform only , you should not resample the moving image here (could be both images move, more often as you describe). Most package will get this wrong. Save the resampling for the end and do it once. 4. You will have to resample one or both images, as their underlying lattices will not be aligned. There is a bit of subtlety here, but in the OPs case probably best to sample both to a similar isotropic grid (e.g. 1mmx1mmx1mm) and subtract. 5. You can do the resampling explicitly or implicitly (i.e. as part of computing the subtraction) but either way use a proper smoothing filter not tri-linear interpolation. 6. Oh, a note - your original images are probably 12 bit encoded in 16 bit ints, make sure your loader isn't truncating or rescaling to 8 bit.

ska 6y ago

Adding a couple of hopefully helpful comments here. 1. There is a lot of terminological abuse in this area, but fusion is properly a display (or production of new images) technique, (co-) registration is the mapping of one image to another. 2. You almost certainly do not want deformative or even affine transforms in the registration of same patient bony anatomy in CT (because it is stereo-tactically accurate). You want a rigid transform here. Also because of CT you can rely on the units are meaningful so you don't need to normalize. 3. Because you are doing rigid transform only , you should not resample the moving image here (could be both images move, more often as you describe). Most package will get this wrong. Save the resampling for the end and do it once. 4. You will have to resample one or both images, as their underlying lattices will not be aligned. There is a bit of subtlety here, but in the OPs case probably best to sample both to a similar isotropic grid (e.g. 1mmx1mmx1mm) and subtract. 5. You can do the resampling explicitly or implicitly (i.e. as part of computing the subtraction) but either way use a proper smoothing filter not tri-linear interpolation. 6. Oh, a note - your original images are probably 12 bit encoded in 16 bit ints, make sure your loader isn't truncating or rescaling to 8 bit.