MR AND MAGNETIZATION-TRANSFER IMAGING IN CIRRHOTIC AND FATTY LIVERS

Purpose. To determine whether low-field MR fat/water separation and ma gnetisation transfer (MT) techniques are useful in studying the livers of patients with parenchymal liver diseases in vivo. Material and Met hods: MR and MT imaging of the liver in 33 patients (14 with primary b iliary cirrhosis, 15 with alcohol-induced liver disease, and 4 with fa tty liver) was performed by means of the fat/water separation techniqu e at 0.1 T. The relaxation time T1 and the MT contrast (MTC) parameter of liver and spleen tissue were measured, and the relative proton den sity fat content N(%) and MTC of the liver were calculated from the se parate fat and water images. The value of N(%) was also compared with the percentage of fatty hepatocytes at histology. Results. The relaxat ion rate R1 of liver measured from the magnitude image, and the differ ence in the value of MTC measured from the water image compared with t he one measured from the fat and water magnitude image, both depended linearly on the value of N(%). The value of N(%) correlated significan tly with the percentage of the fatty hepatocytes. In in vivo fatty tis sue, fat infiltration increased both the observed relaxation rate R1 a nd the measured magnetisation ratio (the steady state magnetisation M- s divided by the equilibrium magnetisation M-o, M-s/M-o) and consequen tly decreased the MT efficiency measured in a magnitude MR image. The amount of liver fibrosis did not correlate with the value of MTC measu red after fat separation. Conclusion. Our results in studying fatty li vers with MR imaging and the MT method show that the fat/water separat ion gives more reliable parametric results. Characterisation of liver cirrhosis by means of the MTC parameter is not reliable, even after fa t separation.