There was a significant increase in external radiation exposure using the RRA versus LRA ( head : median : 6.12 [ interquartile range ( IQR ) : 2.6 to 16.6 ] mRems vs. median : 12.0 [ IQR : 6.4 to 22.0 ] mRems , p = 0.02 ; thyroid : median : 10.10 [ IQR : 4.3 to 25 ] mRems vs. median : 18.70 [ IQR : 11.0 to 38 ] mRems , p = 0.001 ) .