RESULTS	Measured radiation attenuation provided by the XPF caps ( n = 70 ) , XPF thyroid collars ( n = 40 ) , and standard thyroid collars ( n = 38 ) was 85.4 % 25.6 % , 79.7 % 25.8 % and 71.9 % 34.2 % , respectively ( mean difference XPF vs standard thyroid collars , 7.8 % [ 95 % CI , -5.9 % to 21.6 % ] ; p = 0.258 ) .\