Yeah I did a (mostly failed) PhD on ultrasonic imaging and found many things that worked in simulations but not in practice. The fancier your imaging algorithm gets the most ill posed it becomes and more sensitive to noise and errors.

Even if you add noise to your simulation , when you go to the real world it will have lots of sources of noise and errors that you didn't model. In this case I suspect aligning the CT scan with the ultrasound probe will be extremely difficult.

Also there's a reason ultrasonographers are so highly paid, and it's mostly used for pregnancies. In normal tissue it kind of sucks as an imaging method. (On an absolute scale; obviously it's amazing technology.)

Eh maybe it will work though. You never know.