Must have quite the brushes, both for data and power.
Before about 1980, the rotating platform did not rotate continuously (before brushes) but went maybe 1-1/2 turns before stopping and rotating back.
Flexible cables were used that had a cable-handling system next to the wheel.
As I remember it, Varian had the first continuously-rotating CT system, using a small diameter oil-filled slipring at a closed end of the assembly.
I worked on the first open-end continuous-rotation CT scanner (Toshiba TCT900) using large-diameter sliprings, with the high-voltage rings enclosed in SF
6 insulating gas.
Modern scanners have the high-voltage supplies on the rotating platform, fed through low-voltage sliprings, with different high-speed data communication paths (optical or electrical).
To simplify the discussion of computed axial tomography, one needs to look through every point in the object from every angle to get the data required to "reconstruct" what was there at each point to form the image.