A system and method for compensating for torque reaction forces in a medical, apparatus is disclosed. The astern may include a rotary element which rotates about an axis. A contra-rotating flywheel may be driven to rotate about the axis relative to the rotary element, wherein the flywheel is free to rotate and is accelerated and decelerated by a driver which is fixed to the rotary element. Contra-rotation of the flywheel may compensate for torque reaction forces when the rotary element is accelerated or decelerated.
