Here's the radiation dose info for medical tests:
 
Dose is measured in milliseverts (mSv)
 
First off, your question about air travel:
 
Air travel: exposure to radiation is higher because of cosmic rays (protons, electrons, neutrons, other ions);
average dose is approx 2 to 5 mSv for 600-800 hours of flying time (such as aircrew)  (source: WHO)
 
FAA says about 4.5 microSv/hour of flight (0.0045 mSv per hour)  range 3-9 microSv/h depending on the latitude
plane is crossing, which is in similar ballpark.
 
So plane travel gives us pretty low radiation compared to background radiation, even for people who take several
flights per year.
 
 
Natural background radiation:
approx 2.5 mSv/year from radioactive elements in the soil, radon, etc.
 
 
Medical tests:
 
source 1: see attached doscument "radiation doses"

source 2: http://www.hpa.org.uk/radiation/understand/radiation_topics/medical/ted_equivalent.htm
 
 
Order tests selectively!!  They are quite a bit more radiation than a flight!

Colin

Radiology: doses of radiation
Background exposure from earth, radon, cosmic rays: 2.5 mSv per year

Effective dose equivalents:

Reference:
Grainger and Alison’s Diagnostic Radiology