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The Experimental Study in the Evaluation of Inflammatory Grading of Liver Fibrosis Using SPIO-enhanced 3.0-T MR Macrophage Imaging

Author: WuKanHua
Tutor: YanFuHua;XuPengJu;WangQingGuo
School: Fudan University
Course: Medical Imaging and Nuclear Medicine
Keywords: Magnetic resonance imaging Echo train Liver Rats Liver fibrosis Superparamagnetic iron oxide Prussian blue staining
CLC: R575.2
Type: Master's thesis
Year: 2009
Downloads: 38
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Abstract

PartⅠSPIO-enhanced 3.0T magnetic resonance imaging of liver fibrosis in rats-compare the R2^* values at different echo train lengthObjective:This study was designed to compare the R2^* values obtained by T2^* map of plain MRI or 2-hour delayed imaging after SPIO enhancement of rat liver at different echo train lengths（4 or 6） in order to determine the optimal parameters for 3.0T magnetic resonance imaging of rat liver fibrosis.Materials and methods:T2^* map of plain MRI and 2-hour delayed imaging after SPIO-enhancement of liver were performed in 9 normal male SD rats（clean grade）. TR=160ms,flip angle（FA）=30°,spatial resolution=160×160,slice thickness=2.5 mm;echo train length（ETL）=4 or 6.The R2^* values and signal-noise ratio（SNR） obtained by plain MRI and delayed MRI after SPIO enhancement at different ETL（4 or 6） were compared by paired t test.Results:On plain MRI,the R2^* value（61.47±8.71） using ETL=4 did not show significant difference from the R2^* value（56.56±4.66） using ETL=6（t=1.446,P＞0.05）.Two hours delayed imaging after SPIO-enhanced,the R2^* value（234.94±17.52） using ETL=4 was similar to the R2^* value（211.51±22.50） using ETL=6 （t=1.933,P＞0.05）.On plain MRI,the SNR（53.85±9.60） using ETL=4 showed significant difference from the SNR（73.30±12.25） using ETL=6（t=-3.553,P＜0.05）. Two hours delayed imaging after SPIO-enhanced,the SNR（24.45±5.62） using ETL=4 was also significantly different from the SNR（37.58±10.04） using ETL=6 （t=-5.991,P＜0.05）.Conclusion:T2^* map is helpful for improving the image quality of rat liver MRI using ETL=6.T2^*map sequence by ETL=6 is the recommended imaging sequence parameters for SPIO-enhanced 3.0T MRI in rat liver fibrosis model.PartⅡA pathological control study to evaluate liver fibrosis in rats by SPIO-labeled MR imaging of macrophage activityObjective:This study was designed to investigate the change of R2^* value of liver after SPIO enhancement and its correlation to the inflammation activity of liver.The correlation between MRI findings and results of pathological examination（Prussian blue staining） were also studied.Materials and methods:All experimental rats received liver MRI by both plain scan and 2-hour delayed imaging after SPIO enhancement.T2^* map and T2 map were acquired separately.Functool 4.5.3 software was used to acquire the corresponding R2^* map and R2 map and determine R2^* and R2 values.The data were grouped by inflammation activity and fibrosis degree of liver according to the histology activity index（Knodell score）.The following comparisons were made between groups:1.The R2^* and R2 values before and after SPIO enhancement were compared by paired t test in the group with the same inflammation grade;2.The R2^* and R2 values were compared by one-way analysis of variance in rats with different inflammation grades; 3.The R2^* and R2 values before and after SPIO enhancement were compared by paired t test in the group with the same fibrosis stage;4.The R2^* and R2 values were compared by one-way analysis of variance in rats with different fibrosis stages.The correlation between MRI findings and results of pathological examination（Prussian blue staining） were also studied.Results:The inflammation activity of rat liver fibrosis was classified into 3 grades: G_0-1,G₂,G₃.The R2^* and R2 values of rat liver changed significantly after SPIO enhancement in all groups.On plain MRI,the R2^* value between groups G0-1 and G2,or G2 and G3 showed significant difference.After enhancement,the difference between groups was not statistically significant.The difference of R2 value between plain MRI and SPIO-enhanced MRI was statistically significant between groups G0-1 and G2,or GO-1 and G3.At G0-1,some Prussian blue-positive cells were seen sporadically in liver parenchyma.The cell was small in size.At G2,a large number of blue-stained cells with enlarged size,elongated nucleus,and extended cytoplasm in the portal region and periportal space of rat liver.At G3,the number of blue-stained cells in the portal region of rat liver significantly decreased compared with the number at G2.The cells were also shrunken in size.The R2 value after SPIO enhancement in rats with different grades of inflammation activity showed weak correlation to the number of Prussian blue-positive cells （r=0.436,P=0.001）.The number of Prussian blue-positive cells was weakly correlated to the grade of inflammation activity（r=-0.407,P=0.003）.The R2^* of plain MRI and R2^* or R2 values after SPIO enhancement did not show correlation to different inflammation grades in rat liver fibrosis.Conclusion:T2^* map of plain MRI has great value in evaluating the mild and moderate liver inflammation activity.However,the T2^* map after SPIO enhancement only shows limited value in liver inflammation grading and fibrosis staging in rat model.The T2 map of both plain and SPIO-enhanced MRI is useful for evaluating the moderate and severe inflammation activity of rat liver.T2^* map in combination with T2 map can provide important information for objectively evaluating the inflammation activity and fibrosis degree in rat model.The number of Prussian blue-positive cells can,to some extent,reflect the liver inflammation activity and fibrosis degree.

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