As Limone17 alluded you do not have to be topless to have a chest x-ray performed. However as he rightfully stated any clothing that contains metal ( in the form of buttons, or in the case of bras under wire) or jewellery needs to be removed prior to the x-ray in order to to reduce any artifacts as the x-ray will not penetrate metal. Metal just shows up as a light area on the X-ray and as such blocks the underlying structures which the Doctors want to see.
A hospital gown is offered to both male and female patients, but in general most males tend not to bother with it and remain topless.
The x-ray should be taken on full inspiration and that is why the technician ask you to take a deep breath and hold your breath while the x-ray is performed. As he correctly stated positioning is important to ensure that the entire chest is seen.
Exposure to high levels of radiation can be very harmful. However, the X-rays used for medical purposes are safe because the dose of radiation is very small.
The strength of radiation in relation to long-term risk is measured using units called millisieverts (mSv). Some examples of typical exposures are:
- chest X-ray – 0.02 mSv
- a year's worth of medical tests – 0.4 mSv
-average annual exposure to natural radiation – 2.2 mSv
In the UK, 20 mSv is the maximum that someone who works with radiation is allowed to be exposed to in any given year.