The median cumulative radiation exposure per patient was lower in the CTA group than in the functional-testing group ( 10.0 mSv vs. 11.3 mSv ) , but 32.6 % of the patients in the functional-testing group had no exposure , so the overall exposure was higher in the CTA group ( mean , 12.0 mSv vs. 10.1 mSv ; P < 0.001 ) .