| OBJECTIVESSuperpararaagnetic iron oxides ( SPIO) are particulate contrast a-gents for magnetic resonance ( MR) imaging. These contrast agents are distributed to reticuloendothelial cells, such as Kupffer cells (KCs) , and cause local field inhomogeities that produce rapid dephasing of neighboring proton spins, resulting in a shortening of T2. In contrast, malignant liver tumors cannot absorb these agents because of a lack of reticuloendothelial cells. Therefore, the contrast between tumor tissue and surrounding normal liver tissue is enhanced because of signal loss in the liver tissue. It has been reported that the reduced phagocytic activity in cirrhotic liver may cause decrease of SPIO - mediated enhancement of liver. The current study is to evaluate the relationship of signal intensity ( SI) changes in liver parenchyma with different degree of liver fibrosis/cirrhosis on SPIO enhanced MRI.SUBJECTS AND METHODSSubjectsThis study was conducted on male Wistar rats. Liver cirrhosis was induced by oral administration of thioacetamide (TAA) solution(35mg/dl) for experimental group. 45 rats were divided into 3 groups who were feed 12, 17 and 21 weeks respectively with TAA solution. After that they were feed with normal diet more than 2 months. 10 rats were feed with normal diet at the same time served as control group.MeasurementsBefore imaging each rat underwent anesthesia with an intraperito-neal injection of sodium thiopental (20mg/kg). MR imaging was performed before and 60 minutes after intravenous administration of SPIO. Feridex, SPIO contrast agent, was given 20umol/kg. A 2.0 T superconductive MR system ( Elscint) was used. Axial spin - echo 550/12 was used for Tl - weighted images and fast spin - echo 3600/ 126 was used for T2 - weighted images. SI were measured on both right and left lobe of liver before and after enhancement. Then signal -noise ratio (SNR) and relative SI change were calculated. The rats were killed immediately after imaging for pathologic correlation. Standard hematoxylin - eosin stain, trichrome stain and special fibrous reticulum stain were analyzed together for histological degree of fibro-sis and cirrhosis. 21 rats in experimental group and 8 in control group keep alive after the whole procedure. All the 29 rats were divided into 4 groups according the histological degree of liver fibrosis and cirrhosis on ScheuerS criterion (0-4 grade) : Group 0 (n =8) that is the control group; Group 1, grade 1 fibrosis ( n = 5 ) ; Group 2, grade 2 fibrosis ( n = 8 ) and Group 3 , grade 3 and 4 fibrosis/cirrhosis ( n = 8 ). All data were correlated with the histological degree of liver fibrosis and cirrhosis.Statistical analysisAll data are presented as the mean ?SD. At test or one - way ANOVA were used to compare differences. Spearman correlation anal-ysis was used to evaluate the correlation between variables. A p value less than 5% was considered significant.RESULTSSignal intensity change before and after enhancementBoth experimental and control group had marked SI decrease after Feridex administration ( p <0. 01) . SNRs in both two groups significantly decrease after enhancement (p <0.01).The relative SI change in control and experimental group was -59. 98±?18. 93, - 43. 69±?14. 91 respectively. Although the change in normal group was more marked, but t test showed no significant difference existed ( p = 0. 238 ) .Comparison among different histological degreeANOVA analysis showed that there was significant difference a-mong these groups according to average SI and SNR before and after enhancement (p >0.05). But there was significant difference among these groups according to the relative SI changes (p <0. 05). The followed Tukey t test indicated only one significant difference between Group 0 and Group 2 ( p = 0.006 ).Correlation between histological degree and the relative SI changeThere was no direct relationship found between SI change and histological degree with Spearman correlation analysis (p=0.212,r = 0.239).D...
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