Scanning the workers. A full body scan is low enough dosage that it is safe to be scanned every ~3 days (IIRC), so 30% of workers would be randomly selected for a whole body scan each day when they leave the mines.

Since then it has been repurposed for extreme cases like unconscious car crash victims in order to determine the extent of injuries. Or so I learned in a medical imaging elective.

The technology behind it is really cool! By using temporal separation for the different parts of the image they reduce scattering blur, allowing them to use a much lower dose to get the same image quality.