> ultrasound is not CT

They're using "CT" in its literal sense: tomography*, using computers. In this case, ultrasound is the penetrating wave rather than x-ray. It is of course a very different thing than what the medical world knows as "CT" today.

*https://en.wikipedia.org/wiki/Tomography

we can do tomography on any round-robin-rectify multi-pov source, doesn't have to be x-ray is just de facto use in medicine, closer to at min marketing ed problem