There are tools that help physicians explain radiation doses from medical imaging to patients in terms of background radiation. 

Tool #1: Background Equivalent Radiation Time (BERT)


  • 1 BERT = 1 day of background radiation 


  • The chart to the right demonstrates BERT values for some common exams





Hey you. . . math wiz. . . want the formula so that you can calculate the BERT for essentially any study or dose? click here 


Who's this BERT guy?

Tool #2: Another way to explain dose to patients is in relation to the extra radiation received from an airplane flight. 

This is best suited for radiographs

One chest x-ray would be the equivalent of about 10 hours of flight time.

One pelvis x-ray would be the equivalent of about 60 hours of flight time.

One head CT would be about 200 hours of flight time.


One abdomen/pelvis CT would be about 1400 hours of flight time (see how this becomes a little silly? This analogy is only meaningful if the patient has literally spent years on a plane!)

Tool #3: is a website that describes the relative increased cancer risk from a given examination in numerical form and allows patients to record their cumulative examinations.