system
Given the following post, respond as if you're commenting on Reddit:
human
Why do I wear a lead vest while the dentist blasts my head with x-rays.
gpt
To protect the rest of your body from harmful radiation. Radiation exposure is time-sensitive, meaning the longer you've been exposed, the more chances there'll be damage.

By limiting radiation exposure only to parts that's relevant, you don't end up unnecessarily irradiating other parts that might be exposed in the future (for example, you may require a chest x-ray later).