MR and magnetisation transfer imaging in cirrhotic and fatty livers.
Alanen A, Komu M, Leino R, Toikkanen S.: Acta Radiol 1998 Jul;39(4):434-9
Department of Diagnostic Radiology, University of Turku, Finland.
PURPOSE: To determine whether
low-field MR fat/water separation and magnetisation transfer (MT)
techniques are useful in studying the livers of patients with
parenchymal liver diseases in vivo. MATERIAL AND METHODS: MR and
MT imaging of the liver in 33 patients (14 with primary biliary
cirrhosis, 15 with alcohol-induced liver disease, and 4 with fatty
liver) was performed by means of the fat/water separation technique
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
density fat content N(%) and MTC of the liver were calculated
from the separate fat and water images. The value of N(%) was
also compared with the percentage of fatty hepatocytes at histology.
RESULTS: The relaxation rate R1 of liver measured from the magnitude
image, and the difference in the value of MTC measured from the
water image compared with the one measured from the fat and water
magnitude image, both depended linearly on the value of N(%).
The value of N(%) correlated significantly with the percentage
of the fatty hepatocytes. In in vivo fatty tissue, fat infiltration
increased both the observed relaxation rate R1 and the measured
magnetisation ratio (the steady state magnetisation MS divided
by the equilibrium magnetisation MO, MS/MO) and consequently decreased
the MT efficiency measured in a magnitude MR image. The amount
of liver fibrosis did not correlate with the value of MTC measured
after fat separation. CONCLUSION: Our results in studying fatty
livers with MR imaging and the MT method show that the fat/water
separation gives more reliable parametric results. Characterisation
of liver cirrhosis by means of the MTC parameter is not reliable,
even after fat separation.
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