COMPARISON OF IN-PHASE AND OPPOSED-PHASE GRE AND CONVENTIONAL SE MR PULSE SEQUENCES IN T1-WEIGHTED IMAGING OF LIVER-LESIONS

Purpose: Our goal was to compare in-phase (IF) and opposed-phase (OF) GRE and conventional SE sequences in T1-weighted (T1-W) imaging of the liver and to evaluate chemical shift GRE imaging in characterizing li ver/lesions for fat content. Method: LP and OP T1-W GRE with fast low angle shot (FLASH) technique and T1-W SE sequences were compared in 16 2 patients at 1.0 T. Chemical shift GRE imaging was used to characteri ze lesions with fat content. Two hundred sixteen lesions were analyzed in three groups of liver: (a) ''normal'' liver (n = 74 with 110 lesio ns); (b) cirrhotic liver (n = 76 with 85 lesions), and (c) fatty liver (n = 12 with 21 lesions). Liver/lesion contrast and liver/lesion cont rast-to-noise ratio were assessed for lesion detectability. The percen tage of signal intensity variation (SIV) between IP and OP images was used to characterize lesions for fat content. Results: The OP GRE sequ ence had significantly higher contrast for normal and cirrhotic livers (p < 0.001), and the IP GRE sequence had significantly higher contras t and contrast-to-noise ratio for fatty liver (p < 0.001). There were no significant differences between OP, IF, and TI-W SE imaging in cirr hotic cases for contrast-to-noise ratio (p < 0.28). Chemical shift ima ging detected fat in 21 lesions (9.7%, mean SIV, 191.1%) (sensitivity and specificity 100% when compared with fine needle aspiration cytolog y). Conclusion: OP GRE sequences could replace conventional SE sequenc es in T1-W imaging in nonfatty livers, whereas in fatty livers, T1-W S E sequences could be obviated, but both OP and IP sequences are necess ary. Chemical shift imaging (OF and IP) can be used to accurately char acterize lesions for fat content.