The images of HD-SAFIRE ( 2 ) showed similar image noise for liver parenchyma ( 13.4 Hounsfield unit [ HU ] ) , signal-to-noise ratio for liver parenchyma ( 9.2 ) , and lesion-to-liver contrast-to-noise ratio ( 4.5 ) , compared with the FD-FBP images ( 12.6 HU , P = 0.668 ; 9.6 , P > 0.999 ; and 4.5 , P > 0.999 , respectively ) .