肝纤维化磁共振扩散加权、磁共振灌注成像的实验研究
|
摘要
前言
肝纤维化是肝内纤维结缔组织的异常增生与沉积,是各种慢性肝病向肝硬化发展的必经阶段。肝纤维化的早期诊断及严重程度判定在慢性肝病的早期治疗和预后判断中有重要意义。
近年来各种MR功能成像方法的出现为肝纤维化的诊断带来了曙光,其中MR扩散加权成像(diffusion-weighted imaging,DWI)和磁共振灌注成像(perfusion-weighted imaging,PWI)分别通过检测组织内微观水分子的运动状态和血流灌注的变化,在肝纤维化形态学改变出现之前对肝脏分子水平的结构变化和血流动力学改变进行评价。
本研究对大鼠肝纤维化模型进行DWI和PWI检查,通过与肝脏组织病理、超微结构改变、血液生化学和Ⅳ型胶原(C-Ⅳ)、层粘蛋白(LN)免疫组化进行对照分析,对DWI和PWI结果作出更深入合理的解释,评价DWI、PWI在肝纤维化中的诊断效能,以便对无创性评价肝纤维化的方法作出合理选择和应用,提高肝纤维化的诊断水平。
材料和方法
雄性Wistar大鼠60只,体重200-250g,随机分为6组:1、2、3、4、5组为实验组,6组为对照组,每组10只。实验组大鼠每周2次背部皮下注射60%CCl_4和40%橄榄油混合液(0.2ml/100g),共12周。对照组大鼠背部皮下注射生理盐水(0.2ml/100g),每周2次,共12周。在给药4、6、8、10、12周末分别取1-5实验组和对照组2只大鼠进行MR扫描。
MR设备应用Philips Gyroscan Intera 1.5 T超导型磁共振仪,C3线圈。DWI采用SE-EPI序列,b值分别取333、666、1000s/mm~2,TR/TE=1723ms/66ms,层厚3.0mm,层间距0mm,矩阵128×256,激励次数1。DWI原始扩散图像获得后即由计算机自动绘出ADC图。感兴趣层面定为肝门上、下1-2层,感兴趣区选在肝右叶图像质量最好的层面,在不同b值图像上测量肝脏信号强度,同一位置测量3次并取平均值,尽量避开胆管、血管和伪影等。记录DWI图像信号强度(signalintensity,SI及对应的ADC值。比较不同肝纤维化分期时DWI参数的变化,分析各参数与纤维化分期之间的相关性。
灌注成像采用THRIVE(3D T1-TFE)序列,TR/TE=7.5ms/3.7ms,FA=10°,采集次数1,矩阵128×128,层厚2.0mm,层间隔0mm,块厚20mm,脂肪抑制。全肝扫描层数10层,共60个时相,扫描时间126秒。由鼠尾静脉留置针团注对比剂Gd-DTPA(0.05mmol/kg),随后续注10ml生理盐水冲管,注射对比剂同时开始PWI扫描。选用全部PWI灌注图像,分别选择腹主动脉、门静脉和肝实质作为感兴趣区ROI,自动绘制信号强度-时间曲线(time-signal intensity curve,TIC)。观察并记录①峰值时间;②信号上升最大斜率;③信号下降最大斜率。比较不同肝纤维化分期时PWI参数的变化,分析各参数与纤维化分期之间的相关性。
MR扫描后心脏穿刺取血5ml制备血清,统一进行血清学肝纤维化指标检测,包括透明质酸(HA)、Ⅲ型前胶原(PCⅢ)、Ⅳ型胶原(C-Ⅳ)和层粘连蛋白(LN)。比较不同纤维化分期时各指标的变化规律,分析血清学各指标间及与纤维化分期的相关性。
MR扫描后6小时内断头处死大鼠取肝,病理取材尽量与MR中ROI设置层面相对应,10%甲醛固定,行HE、Masson和网状纤维染色,光镜下判定肝纤维化分期。采用Envision二步法进行C-Ⅳ、LN免疫组化染色,定量测量C-Ⅳ、LN的阳性面积比。对照组和实验组每组2只,处死后即刻取1×1×3mm肝组织2.5%戊二醛固定,常规电镜切片制作,透射电镜下观察肝组织超微结构改变。
结果
对照组死亡0只,实验组死亡12只,共48只大鼠完成实验。肝纤维化分期:对照组S0(n=10),实验组S0(n=3)、S1(n=5)、S2(n=9)、S3(n=13)、S4(n=8)。随给药时间延长,实验组肝细胞变性、坏死及炎细胞浸润加重,胶原纤维和网状纤维数量增多、范围扩大。电镜观察随给药时间延长肝细胞损伤加重,贮脂细胞向肌成纤维细胞演变,肝内纤维沉积增多,肝窦毛细血管化早期出现并持续存在。
一、血清学肝纤维化指标变化
各血清学指标随纤维化分期进展逐渐升高,在S4期达到高峰。各血清学指标间及与肝纤维化分期之间显著正相关(P＜0.01)。
二、免疫组化结果
肝纤维化组C-Ⅳ、LN在汇管区及粗大的纤维间隔处肝窦壁阳性着色显著增强并呈连续性分布,随肝纤维化程度的增加肝窦壁C-Ⅳ、LN阳性表达逐渐增高。C-Ⅳ、LN阳性面积百分比与肝纤维化分期的相关系数分别为0.900和0.912,相关性有显著统计学意义(P＜0.01)。
三、DWI结果
根据肝纤维化分期进行分组,同一组内,随b值升高,SI值、ADC值逐渐降低,差异有显著统计学意义(P＜0.01)。在b取333、666和1000 s/mm~2时,随肝纤维化程度加重,DWI图像信号强度SI依次升高,ADC值依次降低,差异有显著统计学意义(P＜0.01)。ADC值与纤维化分期之间有很好的相关性,以b=1000s/mm~2时相关关系最密切。b=333 s/mm~2和666 s/mm~2时,根据SI和ADC值可以将S0～S2期与S4期进行区分,S0期与S3、S4期进行区分。b=1000s/mm~2时,可将S0～S2期与S4期进行区分。ADC值与肝纤维化血清学指标之间存在不同程度的负相关(P＜0.05)。
四、PWI结果
获得大鼠全肝MR灌注图像和稳定的信号强度-时间曲线。随肝纤维化分期进展,门静脉灌注曲线的达峰时间逐渐递增,信号上升最大斜率和信号下降最大斜率逐渐递减。根据门静脉灌注曲线的达峰时间,S2～S4期与S0期有统计学差异(P＜0.05,＜0.001,＜0.001)。根据门静脉的最大上升斜率和最大下降斜率,S0～S2期与S3、S4期有统计学差异(P＜0.05)。肝实质灌注曲线的达峰时间逐渐递增,最大上升斜率、最大下降斜率逐渐递减。S0～S2期与S3、S4期有统计学差异(P＜0.05)。
MR灌注参数与C-Ⅳ、LN相关性分析:门静脉和肝实质的达峰时间与C-Ⅳ和LN存在显著正相关关系(P＜0.01),门静脉和肝实质的最大上升斜率和最大下降斜率与C-Ⅳ和LN存在显著负相关关系(P＜0.01)。
结论
1、血清学指标HA、PCⅢ、C-Ⅳ和LN随肝纤维化分期进展依次升高,血清学指标相互之间及与肝纤维化分期之间存在显著正相关关系。
2、随肝纤维化分期进展,肝窦壁C-Ⅳ和LN的表达逐渐增高,C-Ⅳ、LN阳性面积百分比与肝纤维化分期之间存在显著正相关关系。
3、随肝纤维化分期进展,DWI图像的SI依次升高,ADC值依次降低。DWI可检测S3、S4期中、重度肝纤维化,但对判定S0～S2期肝纤维化尚有局限性。
4、ADC值与肝纤维化血液生化学各指标间存在良好的相关性,共同反映肝纤维化ECM异常增生和沉积的特征性病理改变。
5、MR-PWI可能检测轻度肝纤维化(S2期)和中、重度肝纤维化/早期肝硬化(S3、S4期),肝脏MR灌注参数与肝纤维化分期有良好的相关性,可反映肝纤维化各期的血流动力学变化趋势。
6、肝纤维化大鼠肝组织C-Ⅳ、LN和PWI灌注参数间存在密切的相关关系,均可反映肝纤维化肝窦毛细血管化病理变化,可解释MR灌注成像所反映的肝脏微循环状态和血流动力学改变。
Preface
Liver fibrosis is a pathologic state with abnormal synthesis and deposition of extracellular matrix.It is a procedure of cirrhosis resulted from all kinds of chronic liver diseases.Make early diagnosis and assess the severity of liver fibrosis accurately is very important for therapy and prognosis.
In recent years the functional imaging techniques of MR including difffusion weighted imaging(DWI)and perfusion-weighted imaging(PWI)have developed fast. DWI sensitizes the MR signal related to the incoherent microscopic motion of water molecules,and PWI evaluates the hemodynamic characteristics of the hepatic lesions. Both of them can assess ultrastructural changes and hemodynamic alterations before morphological alteration in liver fibrosis.
In our experimental study,DWI and PWI examinations were underwent in rat model of liver fibrosis.The changes of them in different stages of liver fibrosis were analyzed.DWI and PWI results were compared with histopathological, ultramicrostructural,blood biochemiology,typeⅣcollagen(C-Ⅳ)and laminin(LN) immunohistochemistry expressions to make further interpretations.The diagnosis efficacies of DWI and PWI parameters for liver fibrosis as well as the correlations among them were analyzed,so as to choose noninvasive method for assessing liver fibrosis reasonably.
Materials and Methods
Sixty Wistar rats were divided into six groups:1 to 5 as experimental group,and 6 as control group with 10 rats each.Mixed resolution(0.2ml/100g)with 60%carbon tetrachloride(CCl_4)and 40%olive oil were hypodermic injected twice a week on rats of experimental group,while in control group were injected 0.2ml/100g saline twice a week.At 4,6,8,10,12 weekends after injection,rats of 1 to 5 experimental groups and two rats of control group were underwent MR examination respectively.
All MR examinations were performed on a 1.5 Tesla unit(Philips Intera)with the C3 coil.Three different b values were tested:333,666 and 1000s/mm~2.Spin echo echo-planar DWI was performed using the following acquisition parameters: TR/TE=1723ms/66ms,slice thickness/slice gap=3mm/0mm,matrix=128×256, NSA=1.The software may provide ADC images automatically after DWI original diffusion images were acquired.Then all images were transferred to Philips workstation.Slice of interesting were selected at hepatic right lobes.Three ROI avoiding large vessels and artifacts were placed over 1-2 representative sections involving hepatic hilar.Signal intensity(SI)and ADC value were recorded and compared among different stages of liver fibrosis.The relationships among DWI parameters,liver fibrosis stage were analyzed.
First-pass contrast enhanced perfusion MR imaging was performed on rats in experimental and control groups.A THRIVE(T1-TFE)three dimensional sequence was undertaken with the following acquisition parameters:TR/TE=7.Sms/3.Sms,slice thickness/slice gap=2mm/0mm,block thickness=20mm,matrix=128×128,NSA=1. Sixty phases of dynamic images for ten slices of the whole liver were obtained during 126 seconds after intravenous bolus administration of Gd-DTPA(0.05mmol/kg)via caudal vein.The scan began as soon as bolus administration started.Region-of-interest analyses over the aorta,the portal vein,and liver parenchyma enabled generation of concentration-time curves.Perfusion parameters were recorded as follows:①Time to peak(TP);②Wash-in rate;③Wash-out rate.Three parameters of portal vein and liver parenchyma were compared among different stages of liver fibrosis.The relationships among PWI parameters,fibrosis stage were analyzed.
Blood samples were obtained in all animals after MR examination to observe serum markers of liver fibrosis including hyaluronic acid(HA),procollagen typeⅢ(PCⅢ),typeⅣcollagen(C-Ⅳ)and laminin(LN).The differences of results at various stages of liver fibrosis were compared.Analysis of relationships among serum markers and stage of liver fibrosis were performed.
Liver was resected within six hours after MR scanning and fixed in 10%formalin. HE,Masson and reticular fiber staining stained the samples separately.The stage of liver fibrosis was decided by light microscopy.C-Ⅳand LN immunohistochemistry staining were undertaken by Envision two-step method.A sample with 1×1×3mm volume was obtained and fixed in 2.5%glutaral for making electron microscopic section in 2 rats of control group and of each experimental group.Hepatic ultrastructure was observed by transmission electron microscope.Correlation between ADC and serum marker,perfusion parameter and C-Ⅳcollagen and LN expression were analyzed separately.
Results
Twelve rats of experimental group were eliminated from experiment due to death in the process of breeding.With the prolongation of injection,the severity of hepatic degeneration,necrosis and inflammatory cell infiltration progressed,the amount of collagen and reticular fiber increased.The injury of hepatic cell progressed and the deposition of fibrous tissue increased under electron microscope as the injection time prolonged.Morphology of fat-storing cell changed and hepatic sinusoidal capillarization developed in the process of liver fibrosis.
1.Results of serum indices in liver fibrosis
All serum fibrosis indices increased as the stage of liver fibrosis increased,and reached the peak on S4 stage.There was a significantly positive correlation among all serum fibrosis indices and between serum indices and stage of liver fibrosis(P＜0.01).
2.Results of C-Ⅳand LN immunohistochemistry staining
We found C-Ⅳand LN dramatically increased and successionally deposited along the wall of sinusoids and thick fibrous septa.The positive expression of C-Ⅳand LN increased as the stage of liver fibrosis progressed.There was a significantly positive correlation between C-Ⅳor LN and stage of liver fibrosis(P＜0.01).The r values amount to 0.900 and 0.912,respectively.
3.Results of DWI
Grouping according as different stage of fibrosis,we found that SI and ADC values decreased along with b values increasing(P＜0.01).When b values equal to 333, 666 and 1000 s/mm~2 respectively,SI increased and ADC decreased gradually as the stage of fibrosis progressed(P＜0.01).There was a good relationship between ADC and fibrosis stage,especially when b value was 1000 s/mm~2.When b values equal to 333 and 666s/mm~2,S0-S2 can be distinguished from S3 and S4 stage,and S3 can be distinguished from S4 stage according to SI and ADC values.Moreover b value equal to 1000 s/mm~2,S0-S2 can be distinguished from S4 stage.There was excellent negtive correlation between ADC and serum indices(P＜0.05).
4.Appearances and results of PWI
On perfusion-weighted image,inferior vena cava,abdominal aorta and portal vein visualized in order.As the stage of fibrosis progressed,TP of portal vein increased progressively,and the wash-in rate and wash-out rate decreased progressively. According to TP of portal vein,S2-S4 stage can be distinguished from S0(P＜0.05,＜0.001,＜0.001).According to wash-in rate and wash-out rate of portal vein,S0-S2 stage can be distinguished from S3 and S4 stage(P＜0.05).As the stage of fibrosis progressed,TP of liver parenchyma increased progressively,and the wash-in rate and wash-out rate decreased progressively.S0-S2 stage can be distinguished from S3 and S4 stage(P＜0.05).
Of all parameters,TP of portal vein and liver parenchyma had a positive correlation with the expressions of C-Ⅳand LN(P＜0.01).The wash-in and wash-out rate of portal vein and liver parenchyma had a negative correlation with the expressions of C-Ⅳand LN(P＜0.01).
Conclusions
1.All serum fibrosis indices increased as the stage of liver fibrosis progressed. There was a significantly positive correlation among all indices and between serum indices and stage of liver fibrosis.
2.The positive expression of C-Ⅳand LN increased as the stage of liver fibrosis progressed.There was a significantly positive correlation between C-Ⅳor LN and stage of liver fibrosis.
3.SI increased and ADC value decreased gradually as the stage of fibrosis progressed.There was a good relationship between ADC and stage of fibrosis, especially when b value equal to 1000 s/mm~2.DWI was an effective method to detect liver fibrosis on S3 and S4 stage.
4.There was excellent correlation between ADC and serum indices.It reflected the characteristic pathologic state of abnormal synthesis and deposition of extracellular matrix.
5.PWI should be an effective method to quantify severity of liver fibrosis as well as to detect early cirrhosis(S2 stage)and severe fibrosis(S3-S4 stage).MR perfusion parameters were better correlated with fibrosis staging,and were associated with hemodynamic alternations.
6.There were excellent correlations between the perfusion parameters and the expressions of C-Ⅳand LN.These correlations would better interpreted sinusoidal capillarization in liver fibrosis.
肝纤维化是肝内纤维结缔组织的异常增生与沉积,是各种慢性肝病向肝硬化发展的必经阶段。肝纤维化的早期诊断及严重程度判定在慢性肝病的早期治疗和预后判断中有重要意义。
近年来各种MR功能成像方法的出现为肝纤维化的诊断带来了曙光,其中MR扩散加权成像(diffusion-weighted imaging,DWI)和磁共振灌注成像(perfusion-weighted imaging,PWI)分别通过检测组织内微观水分子的运动状态和血流灌注的变化,在肝纤维化形态学改变出现之前对肝脏分子水平的结构变化和血流动力学改变进行评价。
本研究对大鼠肝纤维化模型进行DWI和PWI检查,通过与肝脏组织病理、超微结构改变、血液生化学和Ⅳ型胶原(C-Ⅳ)、层粘蛋白(LN)免疫组化进行对照分析,对DWI和PWI结果作出更深入合理的解释,评价DWI、PWI在肝纤维化中的诊断效能,以便对无创性评价肝纤维化的方法作出合理选择和应用,提高肝纤维化的诊断水平。
材料和方法
雄性Wistar大鼠60只,体重200-250g,随机分为6组:1、2、3、4、5组为实验组,6组为对照组,每组10只。实验组大鼠每周2次背部皮下注射60%CCl_4和40%橄榄油混合液(0.2ml/100g),共12周。对照组大鼠背部皮下注射生理盐水(0.2ml/100g),每周2次,共12周。在给药4、6、8、10、12周末分别取1-5实验组和对照组2只大鼠进行MR扫描。
MR设备应用Philips Gyroscan Intera 1.5 T超导型磁共振仪,C3线圈。DWI采用SE-EPI序列,b值分别取333、666、1000s/mm~2,TR/TE=1723ms/66ms,层厚3.0mm,层间距0mm,矩阵128×256,激励次数1。DWI原始扩散图像获得后即由计算机自动绘出ADC图。感兴趣层面定为肝门上、下1-2层,感兴趣区选在肝右叶图像质量最好的层面,在不同b值图像上测量肝脏信号强度,同一位置测量3次并取平均值,尽量避开胆管、血管和伪影等。记录DWI图像信号强度(signalintensity,SI及对应的ADC值。比较不同肝纤维化分期时DWI参数的变化,分析各参数与纤维化分期之间的相关性。
灌注成像采用THRIVE(3D T1-TFE)序列,TR/TE=7.5ms/3.7ms,FA=10°,采集次数1,矩阵128×128,层厚2.0mm,层间隔0mm,块厚20mm,脂肪抑制。全肝扫描层数10层,共60个时相,扫描时间126秒。由鼠尾静脉留置针团注对比剂Gd-DTPA(0.05mmol/kg),随后续注10ml生理盐水冲管,注射对比剂同时开始PWI扫描。选用全部PWI灌注图像,分别选择腹主动脉、门静脉和肝实质作为感兴趣区ROI,自动绘制信号强度-时间曲线(time-signal intensity curve,TIC)。观察并记录①峰值时间;②信号上升最大斜率;③信号下降最大斜率。比较不同肝纤维化分期时PWI参数的变化,分析各参数与纤维化分期之间的相关性。
MR扫描后心脏穿刺取血5ml制备血清,统一进行血清学肝纤维化指标检测,包括透明质酸(HA)、Ⅲ型前胶原(PCⅢ)、Ⅳ型胶原(C-Ⅳ)和层粘连蛋白(LN)。比较不同纤维化分期时各指标的变化规律,分析血清学各指标间及与纤维化分期的相关性。
MR扫描后6小时内断头处死大鼠取肝,病理取材尽量与MR中ROI设置层面相对应,10%甲醛固定,行HE、Masson和网状纤维染色,光镜下判定肝纤维化分期。采用Envision二步法进行C-Ⅳ、LN免疫组化染色,定量测量C-Ⅳ、LN的阳性面积比。对照组和实验组每组2只,处死后即刻取1×1×3mm肝组织2.5%戊二醛固定,常规电镜切片制作,透射电镜下观察肝组织超微结构改变。
结果
对照组死亡0只,实验组死亡12只,共48只大鼠完成实验。肝纤维化分期:对照组S0(n=10),实验组S0(n=3)、S1(n=5)、S2(n=9)、S3(n=13)、S4(n=8)。随给药时间延长,实验组肝细胞变性、坏死及炎细胞浸润加重,胶原纤维和网状纤维数量增多、范围扩大。电镜观察随给药时间延长肝细胞损伤加重,贮脂细胞向肌成纤维细胞演变,肝内纤维沉积增多,肝窦毛细血管化早期出现并持续存在。
一、血清学肝纤维化指标变化
各血清学指标随纤维化分期进展逐渐升高,在S4期达到高峰。各血清学指标间及与肝纤维化分期之间显著正相关(P＜0.01)。
二、免疫组化结果
肝纤维化组C-Ⅳ、LN在汇管区及粗大的纤维间隔处肝窦壁阳性着色显著增强并呈连续性分布,随肝纤维化程度的增加肝窦壁C-Ⅳ、LN阳性表达逐渐增高。C-Ⅳ、LN阳性面积百分比与肝纤维化分期的相关系数分别为0.900和0.912,相关性有显著统计学意义(P＜0.01)。
三、DWI结果
根据肝纤维化分期进行分组,同一组内,随b值升高,SI值、ADC值逐渐降低,差异有显著统计学意义(P＜0.01)。在b取333、666和1000 s/mm~2时,随肝纤维化程度加重,DWI图像信号强度SI依次升高,ADC值依次降低,差异有显著统计学意义(P＜0.01)。ADC值与纤维化分期之间有很好的相关性,以b=1000s/mm~2时相关关系最密切。b=333 s/mm~2和666 s/mm~2时,根据SI和ADC值可以将S0～S2期与S4期进行区分,S0期与S3、S4期进行区分。b=1000s/mm~2时,可将S0～S2期与S4期进行区分。ADC值与肝纤维化血清学指标之间存在不同程度的负相关(P＜0.05)。
四、PWI结果
获得大鼠全肝MR灌注图像和稳定的信号强度-时间曲线。随肝纤维化分期进展,门静脉灌注曲线的达峰时间逐渐递增,信号上升最大斜率和信号下降最大斜率逐渐递减。根据门静脉灌注曲线的达峰时间,S2～S4期与S0期有统计学差异(P＜0.05,＜0.001,＜0.001)。根据门静脉的最大上升斜率和最大下降斜率,S0～S2期与S3、S4期有统计学差异(P＜0.05)。肝实质灌注曲线的达峰时间逐渐递增,最大上升斜率、最大下降斜率逐渐递减。S0～S2期与S3、S4期有统计学差异(P＜0.05)。
MR灌注参数与C-Ⅳ、LN相关性分析:门静脉和肝实质的达峰时间与C-Ⅳ和LN存在显著正相关关系(P＜0.01),门静脉和肝实质的最大上升斜率和最大下降斜率与C-Ⅳ和LN存在显著负相关关系(P＜0.01)。
结论
1、血清学指标HA、PCⅢ、C-Ⅳ和LN随肝纤维化分期进展依次升高,血清学指标相互之间及与肝纤维化分期之间存在显著正相关关系。
2、随肝纤维化分期进展,肝窦壁C-Ⅳ和LN的表达逐渐增高,C-Ⅳ、LN阳性面积百分比与肝纤维化分期之间存在显著正相关关系。
3、随肝纤维化分期进展,DWI图像的SI依次升高,ADC值依次降低。DWI可检测S3、S4期中、重度肝纤维化,但对判定S0～S2期肝纤维化尚有局限性。
4、ADC值与肝纤维化血液生化学各指标间存在良好的相关性,共同反映肝纤维化ECM异常增生和沉积的特征性病理改变。
5、MR-PWI可能检测轻度肝纤维化(S2期)和中、重度肝纤维化/早期肝硬化(S3、S4期),肝脏MR灌注参数与肝纤维化分期有良好的相关性,可反映肝纤维化各期的血流动力学变化趋势。
6、肝纤维化大鼠肝组织C-Ⅳ、LN和PWI灌注参数间存在密切的相关关系,均可反映肝纤维化肝窦毛细血管化病理变化,可解释MR灌注成像所反映的肝脏微循环状态和血流动力学改变。
Preface
Liver fibrosis is a pathologic state with abnormal synthesis and deposition of extracellular matrix.It is a procedure of cirrhosis resulted from all kinds of chronic liver diseases.Make early diagnosis and assess the severity of liver fibrosis accurately is very important for therapy and prognosis.
In recent years the functional imaging techniques of MR including difffusion weighted imaging(DWI)and perfusion-weighted imaging(PWI)have developed fast. DWI sensitizes the MR signal related to the incoherent microscopic motion of water molecules,and PWI evaluates the hemodynamic characteristics of the hepatic lesions. Both of them can assess ultrastructural changes and hemodynamic alterations before morphological alteration in liver fibrosis.
In our experimental study,DWI and PWI examinations were underwent in rat model of liver fibrosis.The changes of them in different stages of liver fibrosis were analyzed.DWI and PWI results were compared with histopathological, ultramicrostructural,blood biochemiology,typeⅣcollagen(C-Ⅳ)and laminin(LN) immunohistochemistry expressions to make further interpretations.The diagnosis efficacies of DWI and PWI parameters for liver fibrosis as well as the correlations among them were analyzed,so as to choose noninvasive method for assessing liver fibrosis reasonably.
Materials and Methods
Sixty Wistar rats were divided into six groups:1 to 5 as experimental group,and 6 as control group with 10 rats each.Mixed resolution(0.2ml/100g)with 60%carbon tetrachloride(CCl_4)and 40%olive oil were hypodermic injected twice a week on rats of experimental group,while in control group were injected 0.2ml/100g saline twice a week.At 4,6,8,10,12 weekends after injection,rats of 1 to 5 experimental groups and two rats of control group were underwent MR examination respectively.
All MR examinations were performed on a 1.5 Tesla unit(Philips Intera)with the C3 coil.Three different b values were tested:333,666 and 1000s/mm~2.Spin echo echo-planar DWI was performed using the following acquisition parameters: TR/TE=1723ms/66ms,slice thickness/slice gap=3mm/0mm,matrix=128×256, NSA=1.The software may provide ADC images automatically after DWI original diffusion images were acquired.Then all images were transferred to Philips workstation.Slice of interesting were selected at hepatic right lobes.Three ROI avoiding large vessels and artifacts were placed over 1-2 representative sections involving hepatic hilar.Signal intensity(SI)and ADC value were recorded and compared among different stages of liver fibrosis.The relationships among DWI parameters,liver fibrosis stage were analyzed.
First-pass contrast enhanced perfusion MR imaging was performed on rats in experimental and control groups.A THRIVE(T1-TFE)three dimensional sequence was undertaken with the following acquisition parameters:TR/TE=7.Sms/3.Sms,slice thickness/slice gap=2mm/0mm,block thickness=20mm,matrix=128×128,NSA=1. Sixty phases of dynamic images for ten slices of the whole liver were obtained during 126 seconds after intravenous bolus administration of Gd-DTPA(0.05mmol/kg)via caudal vein.The scan began as soon as bolus administration started.Region-of-interest analyses over the aorta,the portal vein,and liver parenchyma enabled generation of concentration-time curves.Perfusion parameters were recorded as follows:①Time to peak(TP);②Wash-in rate;③Wash-out rate.Three parameters of portal vein and liver parenchyma were compared among different stages of liver fibrosis.The relationships among PWI parameters,fibrosis stage were analyzed.
Blood samples were obtained in all animals after MR examination to observe serum markers of liver fibrosis including hyaluronic acid(HA),procollagen typeⅢ(PCⅢ),typeⅣcollagen(C-Ⅳ)and laminin(LN).The differences of results at various stages of liver fibrosis were compared.Analysis of relationships among serum markers and stage of liver fibrosis were performed.
Liver was resected within six hours after MR scanning and fixed in 10%formalin. HE,Masson and reticular fiber staining stained the samples separately.The stage of liver fibrosis was decided by light microscopy.C-Ⅳand LN immunohistochemistry staining were undertaken by Envision two-step method.A sample with 1×1×3mm volume was obtained and fixed in 2.5%glutaral for making electron microscopic section in 2 rats of control group and of each experimental group.Hepatic ultrastructure was observed by transmission electron microscope.Correlation between ADC and serum marker,perfusion parameter and C-Ⅳcollagen and LN expression were analyzed separately.
Results
Twelve rats of experimental group were eliminated from experiment due to death in the process of breeding.With the prolongation of injection,the severity of hepatic degeneration,necrosis and inflammatory cell infiltration progressed,the amount of collagen and reticular fiber increased.The injury of hepatic cell progressed and the deposition of fibrous tissue increased under electron microscope as the injection time prolonged.Morphology of fat-storing cell changed and hepatic sinusoidal capillarization developed in the process of liver fibrosis.
1.Results of serum indices in liver fibrosis
All serum fibrosis indices increased as the stage of liver fibrosis increased,and reached the peak on S4 stage.There was a significantly positive correlation among all serum fibrosis indices and between serum indices and stage of liver fibrosis(P＜0.01).
2.Results of C-Ⅳand LN immunohistochemistry staining
We found C-Ⅳand LN dramatically increased and successionally deposited along the wall of sinusoids and thick fibrous septa.The positive expression of C-Ⅳand LN increased as the stage of liver fibrosis progressed.There was a significantly positive correlation between C-Ⅳor LN and stage of liver fibrosis(P＜0.01).The r values amount to 0.900 and 0.912,respectively.
3.Results of DWI
Grouping according as different stage of fibrosis,we found that SI and ADC values decreased along with b values increasing(P＜0.01).When b values equal to 333, 666 and 1000 s/mm~2 respectively,SI increased and ADC decreased gradually as the stage of fibrosis progressed(P＜0.01).There was a good relationship between ADC and fibrosis stage,especially when b value was 1000 s/mm~2.When b values equal to 333 and 666s/mm~2,S0-S2 can be distinguished from S3 and S4 stage,and S3 can be distinguished from S4 stage according to SI and ADC values.Moreover b value equal to 1000 s/mm~2,S0-S2 can be distinguished from S4 stage.There was excellent negtive correlation between ADC and serum indices(P＜0.05).
4.Appearances and results of PWI
On perfusion-weighted image,inferior vena cava,abdominal aorta and portal vein visualized in order.As the stage of fibrosis progressed,TP of portal vein increased progressively,and the wash-in rate and wash-out rate decreased progressively. According to TP of portal vein,S2-S4 stage can be distinguished from S0(P＜0.05,＜0.001,＜0.001).According to wash-in rate and wash-out rate of portal vein,S0-S2 stage can be distinguished from S3 and S4 stage(P＜0.05).As the stage of fibrosis progressed,TP of liver parenchyma increased progressively,and the wash-in rate and wash-out rate decreased progressively.S0-S2 stage can be distinguished from S3 and S4 stage(P＜0.05).
Of all parameters,TP of portal vein and liver parenchyma had a positive correlation with the expressions of C-Ⅳand LN(P＜0.01).The wash-in and wash-out rate of portal vein and liver parenchyma had a negative correlation with the expressions of C-Ⅳand LN(P＜0.01).
Conclusions
1.All serum fibrosis indices increased as the stage of liver fibrosis progressed. There was a significantly positive correlation among all indices and between serum indices and stage of liver fibrosis.
2.The positive expression of C-Ⅳand LN increased as the stage of liver fibrosis progressed.There was a significantly positive correlation between C-Ⅳor LN and stage of liver fibrosis.
3.SI increased and ADC value decreased gradually as the stage of fibrosis progressed.There was a good relationship between ADC and stage of fibrosis, especially when b value equal to 1000 s/mm~2.DWI was an effective method to detect liver fibrosis on S3 and S4 stage.
4.There was excellent correlation between ADC and serum indices.It reflected the characteristic pathologic state of abnormal synthesis and deposition of extracellular matrix.
5.PWI should be an effective method to quantify severity of liver fibrosis as well as to detect early cirrhosis(S2 stage)and severe fibrosis(S3-S4 stage).MR perfusion parameters were better correlated with fibrosis staging,and were associated with hemodynamic alternations.
6.There were excellent correlations between the perfusion parameters and the expressions of C-Ⅳand LN.These correlations would better interpreted sinusoidal capillarization in liver fibrosis.
引文
1 高春芳,陆伦根.纤维化疾病的基础和临床.上海:上海科学技术出版社.2004:5.
2 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin N Am.1998;6(1):125-138.
3 Koinuma M,Ohashi I,Hanafusa K,et al.Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.J Magn Reson Imaging.2005;22(1):80-85.
4 Van Beers BE,Materne R,Annet L,et al.Capillarization of the sinusoids in liver fibrosis:noninvasive assessment with contrast-enhanced MRI in the rabbit.Magn Reson Med.2003;49(4):692-699.
5 Rosen BR,Belliveau JW,Vevea JM,et al.Perfusion imaging with NMR contrast agents.Magn Reson Med.1990;14(2):249-265.
6 Desmet VJ,Gerber M,Hoofnagle JH,et al.Classification of chronic hepatitis:diagnosis,grading and staging.Hepatology.1994;19(6):1513-1520.
7 Wu J,Norton PA.Animal models of liver fibrosis.Scand J Gastroenterol.1996;31(12):1137-1143.
8 Montfort I,Perez-Tarnayo R.Collagenase in experimental carbon tetrachloride cirrhosis of the liver.Am J Pathol.1978;92(2):411-420.
9 Brandao CG,Ferreira HHA,Piovesana H,et al.Development of an experimental model of liver cirrhosis in rabbits.Clinical and Experimental Pharmacology and Physiology.2000;27(12):987-990.
10 Ugazio G,Bosia S,Cornaglia E.Experimental model of cirrhosis in rabbits exposed to carbon tetrachloride by inhalation.Exp Commun Mol Pathol Pharmacol.1995;88(1):63-77.
11 曾林,王慧芳,曹永成,等.四氯化碳诱导家兔肝纤维化模型的建立.动物医学进展.2003;24(5):108-110.
12 Ohishi T,Saito H,Tsusaka K,et al.Antifibrogenic effect of an angiotensin converting enzyme inhibitor on chronic carbon tetrachloride-induced hepatic fibrosis in rats.Hepatol Res.2001;21(2):147-158.
13 Di Vinicius I,Baptista AP,Barbosa AA,et al.Morphological signs of cirrhosis regression: Experimental observation on carbon tetrachloride induced liver cirrhosis of rats.Pathol Res Pract.2005;201(6):449-456.
14 Svegliati Baroni G,D'Ambrosio L,Ferretti G,et al.Fibrogenic effect of oxidative stress on rat hepatic stellate cells.Hepatology.1998;27(3):720-726.
15 陆雄,刘平.肝纤维化过程中一个重要的病理改变—肝窦毛细血管化.中华肝脏病杂志.2001;9(1):53-54.
16 Benyon RC,Arthur MJ.Extracellular matrix degradation and the role of hepatic stellate cells.Semin Liver Dis.2001;21(3):373-384.
17 Matsumoto S,Yamamoto K,Nagano T,et al.Immunohistochemical study on phynotypical changes of hepatocytes in liver diseases with reference to extracellular matrix composition.Liver.1999;19(1):32-38.
18 Tanikawa K.Serum maker for hepatic fibrosis and related liver pathology.Patho Res Pract.1994;190(9-10):960-968.
19 Hsing CH,Leu FJ,Tsao TY,et al.Extracellular matrix alteration in chronic hepatitis.Zhonghua Yi Xue Za Zhi(Taipei).1991;48(4):259-266.
20 Afdhal NH,Nunes D.Evaluation of liver fibrosis:A concise review.Am J Gastroenterol.2004;99(6):1160-1174.
21 Friedman SL.Molecular regulation of hepatic fibrosis,an integrated cellular response to tissue injury.J Biol Chem.2000;275(4):2247-2250.
22 Guechot J,Poupon RE,Poupon R.Serum hyaluronan as a marker of liver fibrosis.J Hepatol.1995;22(suppl 2):103-106.
23 Murawaki Y,Ikuta Y,Nishimura Y,et al.Serum markers for connective tissue turnover in patients with chronic hepatitis B and chronic hepatitis C:a comparative analysis.J Hepatol.1995;23(2):145-152.
24 Eriksson S,Fraser JRE,Laurent TC,et al.Endothelial cells are a site of uptake and degradation of hyaluronic acid in the liver.Exp Cell Res.1983;144(1):223-228.
25 王静艳,高红,王兆荃,等.Ⅲ型前胶原层粘连蛋白在肝纤维化诊断中的意义.中国医科大学学报.1997;26(2):177.
26 叶红军,高永生,王丽英,等.血清Ⅲ型前胶原对肝纤维化的诊断价值.临床肝胆病杂志.1993;9(2):90-92.
27 Fontana RJ,Lok AS.Noninvasive monitoring of patients with chronic hepatitis.Hepatology.2002;36(5 Suppl 1):S57-64.
28 Murawaki Y,Koda M,Okamoto K,et al.Diagnostic value of serum type Ⅳ collagen test in comparison with platelet count for predicting the fibrotic stage in patients with chronic hepatitis.J Gastroenterol Hepatol.2001;16(7):777-781.
29 Walsh KM,Fletcher A,MacSween RN,et al.Basement membrane peptides as markers of liver disease in chronic hepatitis C.J Hepatol.2000;32(2):325-330.
30 Yamashita Y,Tang Y,Takahashi M.Ultrafast MR imaging of the abdomen:echo planar imaging and diffusion-weighted imaging.J Magn Reson Imaging.1998;8(2):367-374.
31 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin NAm.1998;6(1):125-138.
32 Muller M,Prasad P,Siewert B,et al.Abdominal diffusion mapping with use of a whole-body echo-planar system.Radiology.1994;190(2):475-478.
33 Moteki T,Horikoshi H,Oya N,et al.Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turbo-FLASH magnetic resonance images.J Magn Resort Imaging.2002;15(5):564-572.
34 Yamada I,Aung W,Himeno Y,et al.Diffusion Coefficients in Abdominal Organs and Hepatic Lesions:Evaluation with Intravoxel Incoherent Motion Echo-planar MR Imaging.Radiology.1999;210(3):617-623.
35 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin N Am.1998;6(1):125-138.
36 Jonathan HB,Allen DE,Peter ER.Acute cerebral infarction:quantification of spin-density and T2 shine-through phenomena on diffusion-weighted MR imaging.Radiology.1999;212(2):333-339.
37 Naganawa S,Sato C,Kumada H,et al.Apparent diffusion coefficient in cervical cancer of the uterus:comparison with the normal uterine cervix.Eur Radiol.2005;15(1):71-78.
38 张晓鹏.在宏观静止中感受微观运动:磁共振扩散加权成像临床应用的若干认识.中国医学影像技术.2005;21(12):1796-1798.
39 Aube C,Racineux PX,Lebigot J,et al.Diagnosis and quantification of hepatic fibrosis with diffusion weighted MR imaging:preliminary results.J Radiol.2004;85(3):301-306.
40 Boulanger Y,Amara M,Lepanto L,et al.Diffusion-weighted MR imaging of the liver of hepatitis C patients.NMR Biomed.2003;16(3):132-136.
41 Moteki T,Horikoshi H,Oya N,et al.Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turbo-FLASH magnetic resonance images.J Magn Resort Imaging.2002;15(5):564-572.
42 杨正汉,谢敬霞,周诚,等.肝硬化组织表观扩散系数改变及其可能机制的实验研究.中国医学影像技术.2002;18(9):849-851.
43 Koinuma M,Ohashi I,Hanafusa K,et al.Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.J Magn Reson Imaging.2005;22(1):80-85.
44 Housset C,Guechot J.Hepatic fibrosis:Phsiopathology and biological diagnosis.Pathol Biol.1999;47(9):886-899.
45 陆雄,刘成海,徐光福,等.大鼠肝纤维化形成过程中肝窦壁层粘连蛋白及Ⅳ-C蛋白的变化.世界华人消化杂志.2001;9(3):260.
46 Rinck PA.Magnetic Resonance Imaging.Berlin:Blackwell Science.2001;149.
47 Keogan MT,Edelman RR.Technologic advances in abdominal MR imaging.Radiology.2001;220(2):310-320.
48 Ichikawa T,Arbab AS,Araki T,et al.Perfusion MR imaging with a superaramagnetic iron oxide using T2-weighted and susceptibility sensitive echo planar sequences:evaluation of tumor vascularity in hepatocellular carcinoma.AJR.1999;173(1):207-213.
49 Pandharipande PV,Krinsky GA,Rusinek H,et al.Perfusion imaging of the liver:current challenges and future goals.Radiology.2005;234(3):661-673.
50 Tsui EY,Chan JH,Cheung YK,et al.Evaluation of therapeutic essectiveness of transarterial chemoembolization for hepatocellular carcinoma:correlation of dynamic susceptibility contrast enhanced echo planar imaging and hepatic angiography.Clin Imaging.2000;24(4):210-216.
51 Scharf J,Zapletal C,Hess t,et al.Assessment of hepatic perfusion in pigs by pharmacokinetic analysis of dynamic MR images.J Magn Reson Imaging.1999;9(4):568-572.
52 Materne R,Smith AM,Peeters F,et al.Assessment of hepatic perfusion parameters with dynamic MRI.Magn Reson Med.2002;47(1):135-142.
53 Guan S,Zhao WD,Zhou KR,et al.CT perfusion at early stage of hepatic diffuse disease.World J Gastroenterol.2005;11(22):3465-3467.
54 Van Beers BE,Leconte I,Materne R,et al.Hepatic perfusion parameters in chronic liver disease:dynamic CT measurements correlated with disease severity.AJR.2001;176(3):667-673.
55 Drop A,Rosinska-bogusiewicz K,Zbanska-klonowska K,et al.Dynamic CT of Hepatic Cirrhosis.Ann Univ Mariae Curie Sklodaska.2002;57(2):39-46.
56 Yamada K,Wu O,Gonzalez RG,et al.Magnetic resonance perfusion-weighted imaging of acute cerebral infarction:effect of the calculation methods and underlying vasculopathy.Stroke.2002;33(1):87-94.
57 李鹏超,鲁建国,马庆久,等.大鼠肝硬化形成过程中门静脉压力及血流动力学变化.第四军医大学学报.2007;28(5):404-406.
58 陆雄,刘平,徐光福,等.肝窦毛细血管化在二甲基亚硝胺大鼠肝纤维化门静脉高压形成中的作用.中华肝脏病杂志.2003;11(10):595-598.
59 Annet L,Materne R,Danse E,et al.Hepatic flow parameters measured with MR imaging and Doppler US:correlations with degree of cirrhosis and portal hypertension.Radiology.2003;229(2):409-414.
60 Yang Z,Xie JX,Zhang Y,et al.Evaluation of cirhotic liver with perfusion-weighted MR imaing:an experimental study in animal models.Radiology.2000;217[Supp1]:1249.
61 Metz CE.Some practical issues of experimental design and data analysis in radiological ROC studies.Invest Radiol.1989;24(3):234-245.
62 Hanley JA,McNeil BJ.The meaning and use of the area under a receiver Operating characteristic(ROC)curve.Radiology.1982;143(1):29-36.
1 高春芳,陆伦根.纤维化疾病的基础和临床.上海:上海科学技术出版社.2004;5.
2 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin N Am.1998;6(1):125-138.
3 Muller M,Prasad P,Siewert B,et al.Abdominal diffusion mapping with use of a whole-body echo-planar system.Radiology.1994;190(2):475-478.
4 Moteki T,Horikoshi H,Oya N,et al.Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turbo-FLASH magnetic resonance images.J Magn Reson Imaging.2002;15(5):564-572.
5 Yamada I,Aung W,Himeno Y,et al.Diffusion coefficients in abdominal organs and hepatic lesions:evaluation with intravoxel incoherent motion echo-planar MR imaging.Radiology.1999;210(3):617-623.
6 Patel MR,Siewert B,Warach S,et al.Diffusion and perfusion imaging techniques.MRI Clin North Am.1995;3(3):425-427.
7 Amano Y,Kumazaki T,Ishihara M.Single-shot diffusion-weighted echo-planar imaging of normal and cirrhotic livers using a phased-array multicoil.Acta Radiol.1998;39(4):440-442.
8 Namimoto T,Yamashita Y,Sumi S,et al.Focal liver masses:characterization with diffusion weighted echo planar MR imaging.Radiology.1997;204(3):739-744.
9 Chow LC,Bammer R,Moseley ME,et al.Single breath-hold diffusion-weighted imaging of the abdomen.J Magn Reson Imaging.2003;18(3):377-382.
10 Ichikawa T,Haradome H,Hachiya J,et al.Diffusion-weighted MR imaging with single-shot echo-planar imaging in the upper abdomen:preliminary clinical experience in 61 patients.Abdom Imaging.1999;24(5):456-461.
11 Hori M,Ichikawa T,Sou H,et al.Improving diffusion-weighted imaging of liver with SENSE technique:a preliminary study.Nippon Igaku Hoshasen Gakkai Zasshi.2003;63(4):177-179.
12 Taouli B,Martin AJ,Qayyum A,et al.Parallel imaging and diffusion tensor imaging for diffusion-weighted MRI of the liver:preliminary experience in healthy volunteers.AJR.2004;183(3):677-680.
13 Chiu FY,Jao JC,Chen CY,et al.Effect of intravenous gadolinium-DTPA on diffusion-weighted magnetic resonance images for evaluation of focal hepatic lesions.J Comput Assist Tomogr.2005;29(2):176-180.
14 杨正汉,谢敬霞,章跃武,等.肝硬化的磁共振扩散加权成像研究.中国医学影像技术.2002;18(9):907-909.
15 Koinuma M,Ohashi I,Hanafusa K,et al.Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.J Magn Reson Imaging.2005;22(1):80-85.
16 Murtz,P,Flacke S,Traber F,et al.Abdomen:Diffusion-weighted MR Imaging with Pulse-triggered Single-Shot Sequences.Radiology.2002;224(1):258-264.
17 尚全良,肖恩华,贺忠,等.GE Signa Twinspeed 1.5 T磁共振肝脏扩散加权成像的技术探讨.中国医学影像技术.2004;20(10):1515-1518.
18 Poustchi-Amin M,Mirowitz SA,Brown JJ,et al.Principles and applications of echo-planar imaging:a review for the general radiologist.Radiographics.2001;21(3):767-779.
19 Takahashi M,Ono J,Harada K,et al.Diffusional anisotropy in cranial nerves with maturation:Quantitative evaluation with diffusion MR imaging in rats.Radiology.2000;216(3):881-885.
20 Taouli B,Vilgrain V,Dumont E,et al.Evaluation of Liver Diffusion Isotropy and Characterization of Focal Hepatic Lesions with Two Single-Shot Echo-planar MR Imaging Sequences:Prospective Study in 66 Patients.Radiology.2003;226(1):71-78.
21 Aube C,Racineux PX,Lebigot J,et al.Diagnosis and quantification of hepatic fibrosis with diffusion weighted MR imaging:preliminary results.J Radiol.2004;85(3):301-306.
22 Yamashita Y,Tang Y,Yakahashi M.Ultrafast MR imaging of the abdomen:echo planar imaging and diffusion-weighted imaging.J Magn Reson Imaging.1998;8(2):367-374.
23 Ichikawa T,Haradome H,Hachiya J,et al.Diffusion weighted MR imaging with a single-shot echoplanar sequence:detection and characterization of focal hepatic lesions.AJR.1998;170(2):397-402.
24 Boulanger Y,Amara M,Lepanto L,et al.Diffusion-weighted MR imaging of the liver of hepatitis C patients.NMR Biomed.2003;16(3):132-136.
25 杨正汉,谢敬霞,周诚,等.肝硬化组织表观扩散系数改变及其可能机制的实验研究.中 国医学影像技术.2002;18(9):849-851.
26 Annet L,Peeters F,Jorge AQ,et al.Assessment of diffusion-weighted imaging in liver fibrosis.Journal of MRI.2007;25(1):122-128.
27 Keogan MT,Edelman RR.Technologic advances in abdominal MR imaging.Radiology.2001;220(2):310-320.
28 Rohl L,Ostergaard L,Simonsen CZ,et al.Viability thresholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MRI and apparent difusion coeficient.Stroke.2001;32(5):1140-1146.
29 Rinck PA.Magnetic Resonance Imaging.Berlin:Blackwell Science.2001;149.
30 Ichikawa T,Arbab AS,Araki T,et al.Perfusion MR imaging with a superaramagnetic iron oxide using T2-weighted and susceptibility sensitive echoplanar sequences:evaluation of tumor vascularity in hepatocellular carcinoma.AJR.1999;173(1):207-213.
31 Tsui EY,Chan JH,Cheung YK,et al.Evaluation of therapeutic essectiveness of transarterial chemoembolization for hepatocellular carcinoma:correlation of dynamic susceptibility contrast enhanced echo planar imaging and hepatic angiography.Clin Imaging.2000;24(4):210-216.
32 Scharf J,Zapletal C,Hess t,et al.Assessment of hepatic perfusion in pigs by pharmacokinetic analysis of dynamic MR images.J Magn Reson Imaging.1999;9(4):568-572.
33 Mateme R,Smith AM,Peeters F,et al.Assessment of hepatic peffusion parameters with dynamic MRI.Magn Reson Meal.2002;47(1):135-142.
34 Ichikawa T,Haradome H,Hachiya J,et al.Perfusion-weighted MR imaging in the upper abdomen:preliminary clinical experience in 61 patients.AJR.1994;169(4):1061-1064.
35 Uematsu H,Yadama H,Sadato N,et al.Assessment of hepatic portal perfusion using T2*measurements of Gd-DTPA.JMRI.1998;8(3):650-654.
36 李鹏超,鲁建国,马庆久,等.大鼠肝硬化形成过程中门静脉压力及血流动力学变化.第四军医大学学报.2007;28(5):404-406.
37 陆雄,刘平,徐光福,等.肝窦毛细血管化在二甲基亚硝胺大鼠肝纤维化门静脉高压形成中的作用.中华肝脏病杂志.2003;11(10):595-598.
38 Annet L,Mateme R,Danse E,et al.Hepatic flow parameters measured with MR imaging and Doppler US:correlations with degree of cirrhosis and portal hypertension.Radiology.2003;229(2):409-414.
39 Van Beers BE,Materne R,Annet L,et al.Capillarization of the sinusoids in liver fibrosis:noninvasive assessment with contrast-enhanced MRI in the rabbit.Magn Reson Med.2003;49(4):692-699.
40 Van Beers BE,Leconte I,Materne R,et al.Hepatic perfusion parameters in chronic liver disease:dynamic CT measurements correlated with disease severity.AJR.2001;176(3):667-673.
41 周诚,杨正汉,叶晓华.CT、MR功能成像在肝脏病变的应用进展.中国医学计算机成像杂志.2004;10(5):329-337.
42 Uematsu H,Yamada H,Sadato N,et al.Assessment of hepatic portal perfusion using T2*measurements of Gd-DTPA.J Magn Reson Imaging.1998;8(3):650-654.
43 Zhao JG,Feng GS,Kong XQ,et al.Assessment of hepatoeellular carcinoma vascularity before and after transcatheter arterial chemoembolization by using first pass perfusion weighted MR imaging.World J Gastroenterol.2004;10(8):1152-1156.
44 Zhao JG,Feng GS,Kong XQ,et al.Changes of tumor microcirculation after transcatheter arterial chemoembolization:first pass perfusion MR imaging and Chinese ink casting in a rabbit model.World J Gastroenterol.2004;10(10):1415-1420.
45 SchafJ,Zapletal C,Hess T,et al.Assessment of hepatic perfusion in pigs by pharmacokinetic analysis of dynamic MR images.J Magn Reson Imaging.1999;9(4):568-572.
46 Reimer P,Saini S,Kwong KK,et al.Dynamic gadolinium-enhanced echo-planar MR imaging of the liver:effect of pulse sequence and dose on enhancement.J Magn Resort Imaging.1994;4(3):331-335.
47 Yang Z,Xie JX,Zhang Y,et al.Evaluation of cirrhotic liver with perfusion-weighted MR imaing:an experimental study in animal models.Radiology.2000;217[Supp1]:1249.
48 Peeters F,Annet L,Hermoye L,et al.Inflow correction of hepatic pension measurements using T1-weighted,fast gradient-echo contrast-enhanced MRI.Magn Reson Med.2004;51(4):710-717.
49 Taouli B, Losada M, Holland A, et al. Magnetic resonance imaging of hepatocellular carcinoma. Gastroenterology. 2004; 127(5 Suppl 1): 144-152.
2 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin N Am.1998;6(1):125-138.
3 Koinuma M,Ohashi I,Hanafusa K,et al.Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.J Magn Reson Imaging.2005;22(1):80-85.
4 Van Beers BE,Materne R,Annet L,et al.Capillarization of the sinusoids in liver fibrosis:noninvasive assessment with contrast-enhanced MRI in the rabbit.Magn Reson Med.2003;49(4):692-699.
5 Rosen BR,Belliveau JW,Vevea JM,et al.Perfusion imaging with NMR contrast agents.Magn Reson Med.1990;14(2):249-265.
6 Desmet VJ,Gerber M,Hoofnagle JH,et al.Classification of chronic hepatitis:diagnosis,grading and staging.Hepatology.1994;19(6):1513-1520.
7 Wu J,Norton PA.Animal models of liver fibrosis.Scand J Gastroenterol.1996;31(12):1137-1143.
8 Montfort I,Perez-Tarnayo R.Collagenase in experimental carbon tetrachloride cirrhosis of the liver.Am J Pathol.1978;92(2):411-420.
9 Brandao CG,Ferreira HHA,Piovesana H,et al.Development of an experimental model of liver cirrhosis in rabbits.Clinical and Experimental Pharmacology and Physiology.2000;27(12):987-990.
10 Ugazio G,Bosia S,Cornaglia E.Experimental model of cirrhosis in rabbits exposed to carbon tetrachloride by inhalation.Exp Commun Mol Pathol Pharmacol.1995;88(1):63-77.
11 曾林,王慧芳,曹永成,等.四氯化碳诱导家兔肝纤维化模型的建立.动物医学进展.2003;24(5):108-110.
12 Ohishi T,Saito H,Tsusaka K,et al.Antifibrogenic effect of an angiotensin converting enzyme inhibitor on chronic carbon tetrachloride-induced hepatic fibrosis in rats.Hepatol Res.2001;21(2):147-158.
13 Di Vinicius I,Baptista AP,Barbosa AA,et al.Morphological signs of cirrhosis regression: Experimental observation on carbon tetrachloride induced liver cirrhosis of rats.Pathol Res Pract.2005;201(6):449-456.
14 Svegliati Baroni G,D'Ambrosio L,Ferretti G,et al.Fibrogenic effect of oxidative stress on rat hepatic stellate cells.Hepatology.1998;27(3):720-726.
15 陆雄,刘平.肝纤维化过程中一个重要的病理改变—肝窦毛细血管化.中华肝脏病杂志.2001;9(1):53-54.
16 Benyon RC,Arthur MJ.Extracellular matrix degradation and the role of hepatic stellate cells.Semin Liver Dis.2001;21(3):373-384.
17 Matsumoto S,Yamamoto K,Nagano T,et al.Immunohistochemical study on phynotypical changes of hepatocytes in liver diseases with reference to extracellular matrix composition.Liver.1999;19(1):32-38.
18 Tanikawa K.Serum maker for hepatic fibrosis and related liver pathology.Patho Res Pract.1994;190(9-10):960-968.
19 Hsing CH,Leu FJ,Tsao TY,et al.Extracellular matrix alteration in chronic hepatitis.Zhonghua Yi Xue Za Zhi(Taipei).1991;48(4):259-266.
20 Afdhal NH,Nunes D.Evaluation of liver fibrosis:A concise review.Am J Gastroenterol.2004;99(6):1160-1174.
21 Friedman SL.Molecular regulation of hepatic fibrosis,an integrated cellular response to tissue injury.J Biol Chem.2000;275(4):2247-2250.
22 Guechot J,Poupon RE,Poupon R.Serum hyaluronan as a marker of liver fibrosis.J Hepatol.1995;22(suppl 2):103-106.
23 Murawaki Y,Ikuta Y,Nishimura Y,et al.Serum markers for connective tissue turnover in patients with chronic hepatitis B and chronic hepatitis C:a comparative analysis.J Hepatol.1995;23(2):145-152.
24 Eriksson S,Fraser JRE,Laurent TC,et al.Endothelial cells are a site of uptake and degradation of hyaluronic acid in the liver.Exp Cell Res.1983;144(1):223-228.
25 王静艳,高红,王兆荃,等.Ⅲ型前胶原层粘连蛋白在肝纤维化诊断中的意义.中国医科大学学报.1997;26(2):177.
26 叶红军,高永生,王丽英,等.血清Ⅲ型前胶原对肝纤维化的诊断价值.临床肝胆病杂志.1993;9(2):90-92.
27 Fontana RJ,Lok AS.Noninvasive monitoring of patients with chronic hepatitis.Hepatology.2002;36(5 Suppl 1):S57-64.
28 Murawaki Y,Koda M,Okamoto K,et al.Diagnostic value of serum type Ⅳ collagen test in comparison with platelet count for predicting the fibrotic stage in patients with chronic hepatitis.J Gastroenterol Hepatol.2001;16(7):777-781.
29 Walsh KM,Fletcher A,MacSween RN,et al.Basement membrane peptides as markers of liver disease in chronic hepatitis C.J Hepatol.2000;32(2):325-330.
30 Yamashita Y,Tang Y,Takahashi M.Ultrafast MR imaging of the abdomen:echo planar imaging and diffusion-weighted imaging.J Magn Reson Imaging.1998;8(2):367-374.
31 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin NAm.1998;6(1):125-138.
32 Muller M,Prasad P,Siewert B,et al.Abdominal diffusion mapping with use of a whole-body echo-planar system.Radiology.1994;190(2):475-478.
33 Moteki T,Horikoshi H,Oya N,et al.Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turbo-FLASH magnetic resonance images.J Magn Resort Imaging.2002;15(5):564-572.
34 Yamada I,Aung W,Himeno Y,et al.Diffusion Coefficients in Abdominal Organs and Hepatic Lesions:Evaluation with Intravoxel Incoherent Motion Echo-planar MR Imaging.Radiology.1999;210(3):617-623.
35 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin N Am.1998;6(1):125-138.
36 Jonathan HB,Allen DE,Peter ER.Acute cerebral infarction:quantification of spin-density and T2 shine-through phenomena on diffusion-weighted MR imaging.Radiology.1999;212(2):333-339.
37 Naganawa S,Sato C,Kumada H,et al.Apparent diffusion coefficient in cervical cancer of the uterus:comparison with the normal uterine cervix.Eur Radiol.2005;15(1):71-78.
38 张晓鹏.在宏观静止中感受微观运动:磁共振扩散加权成像临床应用的若干认识.中国医学影像技术.2005;21(12):1796-1798.
39 Aube C,Racineux PX,Lebigot J,et al.Diagnosis and quantification of hepatic fibrosis with diffusion weighted MR imaging:preliminary results.J Radiol.2004;85(3):301-306.
40 Boulanger Y,Amara M,Lepanto L,et al.Diffusion-weighted MR imaging of the liver of hepatitis C patients.NMR Biomed.2003;16(3):132-136.
41 Moteki T,Horikoshi H,Oya N,et al.Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turbo-FLASH magnetic resonance images.J Magn Resort Imaging.2002;15(5):564-572.
42 杨正汉,谢敬霞,周诚,等.肝硬化组织表观扩散系数改变及其可能机制的实验研究.中国医学影像技术.2002;18(9):849-851.
43 Koinuma M,Ohashi I,Hanafusa K,et al.Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.J Magn Reson Imaging.2005;22(1):80-85.
44 Housset C,Guechot J.Hepatic fibrosis:Phsiopathology and biological diagnosis.Pathol Biol.1999;47(9):886-899.
45 陆雄,刘成海,徐光福,等.大鼠肝纤维化形成过程中肝窦壁层粘连蛋白及Ⅳ-C蛋白的变化.世界华人消化杂志.2001;9(3):260.
46 Rinck PA.Magnetic Resonance Imaging.Berlin:Blackwell Science.2001;149.
47 Keogan MT,Edelman RR.Technologic advances in abdominal MR imaging.Radiology.2001;220(2):310-320.
48 Ichikawa T,Arbab AS,Araki T,et al.Perfusion MR imaging with a superaramagnetic iron oxide using T2-weighted and susceptibility sensitive echo planar sequences:evaluation of tumor vascularity in hepatocellular carcinoma.AJR.1999;173(1):207-213.
49 Pandharipande PV,Krinsky GA,Rusinek H,et al.Perfusion imaging of the liver:current challenges and future goals.Radiology.2005;234(3):661-673.
50 Tsui EY,Chan JH,Cheung YK,et al.Evaluation of therapeutic essectiveness of transarterial chemoembolization for hepatocellular carcinoma:correlation of dynamic susceptibility contrast enhanced echo planar imaging and hepatic angiography.Clin Imaging.2000;24(4):210-216.
51 Scharf J,Zapletal C,Hess t,et al.Assessment of hepatic perfusion in pigs by pharmacokinetic analysis of dynamic MR images.J Magn Reson Imaging.1999;9(4):568-572.
52 Materne R,Smith AM,Peeters F,et al.Assessment of hepatic perfusion parameters with dynamic MRI.Magn Reson Med.2002;47(1):135-142.
53 Guan S,Zhao WD,Zhou KR,et al.CT perfusion at early stage of hepatic diffuse disease.World J Gastroenterol.2005;11(22):3465-3467.
54 Van Beers BE,Leconte I,Materne R,et al.Hepatic perfusion parameters in chronic liver disease:dynamic CT measurements correlated with disease severity.AJR.2001;176(3):667-673.
55 Drop A,Rosinska-bogusiewicz K,Zbanska-klonowska K,et al.Dynamic CT of Hepatic Cirrhosis.Ann Univ Mariae Curie Sklodaska.2002;57(2):39-46.
56 Yamada K,Wu O,Gonzalez RG,et al.Magnetic resonance perfusion-weighted imaging of acute cerebral infarction:effect of the calculation methods and underlying vasculopathy.Stroke.2002;33(1):87-94.
57 李鹏超,鲁建国,马庆久,等.大鼠肝硬化形成过程中门静脉压力及血流动力学变化.第四军医大学学报.2007;28(5):404-406.
58 陆雄,刘平,徐光福,等.肝窦毛细血管化在二甲基亚硝胺大鼠肝纤维化门静脉高压形成中的作用.中华肝脏病杂志.2003;11(10):595-598.
59 Annet L,Materne R,Danse E,et al.Hepatic flow parameters measured with MR imaging and Doppler US:correlations with degree of cirrhosis and portal hypertension.Radiology.2003;229(2):409-414.
60 Yang Z,Xie JX,Zhang Y,et al.Evaluation of cirhotic liver with perfusion-weighted MR imaing:an experimental study in animal models.Radiology.2000;217[Supp1]:1249.
61 Metz CE.Some practical issues of experimental design and data analysis in radiological ROC studies.Invest Radiol.1989;24(3):234-245.
62 Hanley JA,McNeil BJ.The meaning and use of the area under a receiver Operating characteristic(ROC)curve.Radiology.1982;143(1):29-36.
1 高春芳,陆伦根.纤维化疾病的基础和临床.上海:上海科学技术出版社.2004;5.
2 Gray L,Macfall J.Overview of diffusion imaging.MRI Clin N Am.1998;6(1):125-138.
3 Muller M,Prasad P,Siewert B,et al.Abdominal diffusion mapping with use of a whole-body echo-planar system.Radiology.1994;190(2):475-478.
4 Moteki T,Horikoshi H,Oya N,et al.Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turbo-FLASH magnetic resonance images.J Magn Reson Imaging.2002;15(5):564-572.
5 Yamada I,Aung W,Himeno Y,et al.Diffusion coefficients in abdominal organs and hepatic lesions:evaluation with intravoxel incoherent motion echo-planar MR imaging.Radiology.1999;210(3):617-623.
6 Patel MR,Siewert B,Warach S,et al.Diffusion and perfusion imaging techniques.MRI Clin North Am.1995;3(3):425-427.
7 Amano Y,Kumazaki T,Ishihara M.Single-shot diffusion-weighted echo-planar imaging of normal and cirrhotic livers using a phased-array multicoil.Acta Radiol.1998;39(4):440-442.
8 Namimoto T,Yamashita Y,Sumi S,et al.Focal liver masses:characterization with diffusion weighted echo planar MR imaging.Radiology.1997;204(3):739-744.
9 Chow LC,Bammer R,Moseley ME,et al.Single breath-hold diffusion-weighted imaging of the abdomen.J Magn Reson Imaging.2003;18(3):377-382.
10 Ichikawa T,Haradome H,Hachiya J,et al.Diffusion-weighted MR imaging with single-shot echo-planar imaging in the upper abdomen:preliminary clinical experience in 61 patients.Abdom Imaging.1999;24(5):456-461.
11 Hori M,Ichikawa T,Sou H,et al.Improving diffusion-weighted imaging of liver with SENSE technique:a preliminary study.Nippon Igaku Hoshasen Gakkai Zasshi.2003;63(4):177-179.
12 Taouli B,Martin AJ,Qayyum A,et al.Parallel imaging and diffusion tensor imaging for diffusion-weighted MRI of the liver:preliminary experience in healthy volunteers.AJR.2004;183(3):677-680.
13 Chiu FY,Jao JC,Chen CY,et al.Effect of intravenous gadolinium-DTPA on diffusion-weighted magnetic resonance images for evaluation of focal hepatic lesions.J Comput Assist Tomogr.2005;29(2):176-180.
14 杨正汉,谢敬霞,章跃武,等.肝硬化的磁共振扩散加权成像研究.中国医学影像技术.2002;18(9):907-909.
15 Koinuma M,Ohashi I,Hanafusa K,et al.Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.J Magn Reson Imaging.2005;22(1):80-85.
16 Murtz,P,Flacke S,Traber F,et al.Abdomen:Diffusion-weighted MR Imaging with Pulse-triggered Single-Shot Sequences.Radiology.2002;224(1):258-264.
17 尚全良,肖恩华,贺忠,等.GE Signa Twinspeed 1.5 T磁共振肝脏扩散加权成像的技术探讨.中国医学影像技术.2004;20(10):1515-1518.
18 Poustchi-Amin M,Mirowitz SA,Brown JJ,et al.Principles and applications of echo-planar imaging:a review for the general radiologist.Radiographics.2001;21(3):767-779.
19 Takahashi M,Ono J,Harada K,et al.Diffusional anisotropy in cranial nerves with maturation:Quantitative evaluation with diffusion MR imaging in rats.Radiology.2000;216(3):881-885.
20 Taouli B,Vilgrain V,Dumont E,et al.Evaluation of Liver Diffusion Isotropy and Characterization of Focal Hepatic Lesions with Two Single-Shot Echo-planar MR Imaging Sequences:Prospective Study in 66 Patients.Radiology.2003;226(1):71-78.
21 Aube C,Racineux PX,Lebigot J,et al.Diagnosis and quantification of hepatic fibrosis with diffusion weighted MR imaging:preliminary results.J Radiol.2004;85(3):301-306.
22 Yamashita Y,Tang Y,Yakahashi M.Ultrafast MR imaging of the abdomen:echo planar imaging and diffusion-weighted imaging.J Magn Reson Imaging.1998;8(2):367-374.
23 Ichikawa T,Haradome H,Hachiya J,et al.Diffusion weighted MR imaging with a single-shot echoplanar sequence:detection and characterization of focal hepatic lesions.AJR.1998;170(2):397-402.
24 Boulanger Y,Amara M,Lepanto L,et al.Diffusion-weighted MR imaging of the liver of hepatitis C patients.NMR Biomed.2003;16(3):132-136.
25 杨正汉,谢敬霞,周诚,等.肝硬化组织表观扩散系数改变及其可能机制的实验研究.中 国医学影像技术.2002;18(9):849-851.
26 Annet L,Peeters F,Jorge AQ,et al.Assessment of diffusion-weighted imaging in liver fibrosis.Journal of MRI.2007;25(1):122-128.
27 Keogan MT,Edelman RR.Technologic advances in abdominal MR imaging.Radiology.2001;220(2):310-320.
28 Rohl L,Ostergaard L,Simonsen CZ,et al.Viability thresholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MRI and apparent difusion coeficient.Stroke.2001;32(5):1140-1146.
29 Rinck PA.Magnetic Resonance Imaging.Berlin:Blackwell Science.2001;149.
30 Ichikawa T,Arbab AS,Araki T,et al.Perfusion MR imaging with a superaramagnetic iron oxide using T2-weighted and susceptibility sensitive echoplanar sequences:evaluation of tumor vascularity in hepatocellular carcinoma.AJR.1999;173(1):207-213.
31 Tsui EY,Chan JH,Cheung YK,et al.Evaluation of therapeutic essectiveness of transarterial chemoembolization for hepatocellular carcinoma:correlation of dynamic susceptibility contrast enhanced echo planar imaging and hepatic angiography.Clin Imaging.2000;24(4):210-216.
32 Scharf J,Zapletal C,Hess t,et al.Assessment of hepatic perfusion in pigs by pharmacokinetic analysis of dynamic MR images.J Magn Reson Imaging.1999;9(4):568-572.
33 Mateme R,Smith AM,Peeters F,et al.Assessment of hepatic peffusion parameters with dynamic MRI.Magn Reson Meal.2002;47(1):135-142.
34 Ichikawa T,Haradome H,Hachiya J,et al.Perfusion-weighted MR imaging in the upper abdomen:preliminary clinical experience in 61 patients.AJR.1994;169(4):1061-1064.
35 Uematsu H,Yadama H,Sadato N,et al.Assessment of hepatic portal perfusion using T2*measurements of Gd-DTPA.JMRI.1998;8(3):650-654.
36 李鹏超,鲁建国,马庆久,等.大鼠肝硬化形成过程中门静脉压力及血流动力学变化.第四军医大学学报.2007;28(5):404-406.
37 陆雄,刘平,徐光福,等.肝窦毛细血管化在二甲基亚硝胺大鼠肝纤维化门静脉高压形成中的作用.中华肝脏病杂志.2003;11(10):595-598.
38 Annet L,Mateme R,Danse E,et al.Hepatic flow parameters measured with MR imaging and Doppler US:correlations with degree of cirrhosis and portal hypertension.Radiology.2003;229(2):409-414.
39 Van Beers BE,Materne R,Annet L,et al.Capillarization of the sinusoids in liver fibrosis:noninvasive assessment with contrast-enhanced MRI in the rabbit.Magn Reson Med.2003;49(4):692-699.
40 Van Beers BE,Leconte I,Materne R,et al.Hepatic perfusion parameters in chronic liver disease:dynamic CT measurements correlated with disease severity.AJR.2001;176(3):667-673.
41 周诚,杨正汉,叶晓华.CT、MR功能成像在肝脏病变的应用进展.中国医学计算机成像杂志.2004;10(5):329-337.
42 Uematsu H,Yamada H,Sadato N,et al.Assessment of hepatic portal perfusion using T2*measurements of Gd-DTPA.J Magn Reson Imaging.1998;8(3):650-654.
43 Zhao JG,Feng GS,Kong XQ,et al.Assessment of hepatoeellular carcinoma vascularity before and after transcatheter arterial chemoembolization by using first pass perfusion weighted MR imaging.World J Gastroenterol.2004;10(8):1152-1156.
44 Zhao JG,Feng GS,Kong XQ,et al.Changes of tumor microcirculation after transcatheter arterial chemoembolization:first pass perfusion MR imaging and Chinese ink casting in a rabbit model.World J Gastroenterol.2004;10(10):1415-1420.
45 SchafJ,Zapletal C,Hess T,et al.Assessment of hepatic perfusion in pigs by pharmacokinetic analysis of dynamic MR images.J Magn Reson Imaging.1999;9(4):568-572.
46 Reimer P,Saini S,Kwong KK,et al.Dynamic gadolinium-enhanced echo-planar MR imaging of the liver:effect of pulse sequence and dose on enhancement.J Magn Resort Imaging.1994;4(3):331-335.
47 Yang Z,Xie JX,Zhang Y,et al.Evaluation of cirrhotic liver with perfusion-weighted MR imaing:an experimental study in animal models.Radiology.2000;217[Supp1]:1249.
48 Peeters F,Annet L,Hermoye L,et al.Inflow correction of hepatic pension measurements using T1-weighted,fast gradient-echo contrast-enhanced MRI.Magn Reson Med.2004;51(4):710-717.
49 Taouli B, Losada M, Holland A, et al. Magnetic resonance imaging of hepatocellular carcinoma. Gastroenterology. 2004; 127(5 Suppl 1): 144-152.