How are portable X-ray machines powered?

I was discussing the mess that is our current fuel dilemma earlier today with my sister who is a freshly graduated radiology student from a local technical college. She said that the portable x-ray machines at the hospitals she’s done clinicals at are virtually self-sufficient as far as power goes and that she’s heard that they can actually go fast enough to bust through a wall. So, my question is: how are these things powered, and how practical would it be to develop a scooter or something that is powered the same way for cheaper transportation?

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