We are trying to register a CT of the spine to tracked ultrasound images. However we do not manage to get to the desired registration accuracy. Are there requirements or do you have tips about the ultrasound scan to enable a good registration?
The question is quite generic, these are the main considerations:
- CT image quality, mainly spacing and artifacts
- Ultrasound image quality, image sharpness on the bone, contrast
- Registration algorithm
1: Is self explanatory, and in general not something easy to change, so 2&3 are the most interesting ones.
2: We have seen that ultrasound on bone, and specifically spine is quite challenging, given the number of structures. Furthermore one has to pick the US parameters adequately for the chosen registration algorithm.
3: I think that this is the critical point, as it influences the choices in 1&2. Picking the appropiate algorithm is hard and you have to iterate given your images and previous registration results. Image based algorithms can work to register the CT and US images, or you can do some post-processing on the images and use those instead. This is something you’ll have to research. Initial registration will of course help greatly.
What is your current approach, and what is the current registration accuracy vs the desired accuracy?