Before hepatic surgery , we randomly assigned 60 patients ( 17 women , 43 men ; mean SD age , 68.9 10.1 years ) who had undergone 3D-CTA to 1 of 2 protocols ; 30 patients underwent scanning under the conventional 120-kilovolt ( peak ) protocol with filtered back projection ( P1 ) ; and 30 patients , under an 80-kilovolt ( peak ) protocol with HIR ( P2 ) .