The Chinese would check for 'illegal' pregnancies during the days of the one-child policy. They would use a solid state x-ray emitter as a source of radiation and a passive fluorescent screen, both probably because there was no reliable electrical power available and this is a very cheap to manufacture setup. The dose emitted would be quite high due to the insensitivity of the screen, the degradation over time of the source (requiring a higher than necessary quantity of radioactive material at the start to get a long useful operating life) and the duration, on the order of seconds.

I've tried to find a video of this but alas, no luck. The one I remember seeing was extremely primitive, safety was basically non-existent, both for the woman being screened (and her unborn child, quite possibly to be aborted anyway if detected) and the operator of the device.