| BackgroundLiver fibrosis is found in almost all chronic liver disease, In the process of liver fibrosis there’s mainly collagen, proteoglycan and many other kinds of macromolecular substances accumulated in the extracellular matrix (ECM).Fiber bundle gradually formed fiber separation of liver parenchyma and formed multiple regenerative nodules of hepatocytes with the progression of liver fibrosis, then causes liver cirrhosis.Liver cirrhosis is the end-stage for almost all liver diseases.In the continuous progression of liver fibrosis, liver function and injury make the internal structuredue changes, patients will get a series of complicated clinical symptoms and signs. In the background of cirrhosis or liver fibrosis liver cells also have a chance to be cancerous.It has been found that in the dynamic developing procession from hepatic fibrosis to cirrhosis, liver fibrosis or even reached the stage of early cirrhosis may be reversed through appropriate treatment.Until now, liver biopsy is regarded as the "gold standard" for diagnosis and staging of liver fibrosis.Digital image analysis(DIA) can provide more quickly,accurately and relatively objective quantitative results than the traditional semi quantitative evaluation system can do, and the accurate evaluation of transition period via DIA may not need experienced physician.Collagen proportional area(CPA) is closely related with liver fibrosis staging,and can provide quantitative assessment of collagen content in liver tissue. But liver biopsy is an invasive examination and may has some sampling error,so it does not apply to the long-term repeated diagnosis and treatment for patients with diffuse liver disease. In order to provide diagnosis and treatment for the patients with liver fibrosis, especially patients who could benefit from early intervention. So,there’s urgent need for a reliable and non-invasive examination method to assess the patients’ condition, the efficacy of drug evaluation and also the epidemiological research.Medical imaging is a noninvasive examination method, which is practical for the daily clinical work.But for the early diagnosis of liver fibrosis and staging evaluation,it still not fully meets the clinical requirement.It have been confirmed that T1rho imaging can reflect energy or proton exchange interaction when macromolecular binding with water in the organization.During the T1rho pulses, the equilibrium magnetization vector firstly be rotated to the horizontal plane by an RF pulse, and realize spin lock via applying different amplitude of continuous spin lock pulses,.The magnetic torque parallel to the transverse axis synchronously decays with effective magnetic field, the longitudinal relaxation within the rotating coordinate system can be denoted by the T1rho values.This technology was applied to the study of liver fibrosis by scholars, and it has been found that T1rho values increased with liver fibrosis progression.But as so far there is not a unified conclusion that if T1rho technology can grade liver fibrosis and what is the key influencing factor of T1rho values and whther Adiabatic T1rho sequence may do the diagnosis of liver fibrosis. In this study,T1rho imaging in the diagnosis of liver fibrosis and the influencing factors are discussed, another purpose of this research is to preliminarily decide which kind of T1rho is more potential for grading diagnosis of liver fibrosis in clinical application.PART Ⅰ The Preliminary study on staging of liver fibrosis by Tlrho values in a CCL4 rat modelObjectiveTo explore the correlation between T1rho values and stage of liver fibrosis in rats,and explore the diagnostic value of Tlrho in staging liver fibrosis.Exploring that if the CPA values,inflammation score and steatosis influence the T1rho values of rats.Materials and Methods1.Liver fibrosis model and grouping methods65 healthy SD rats were randomly divided into model group (50 rats) and blank group (15 rats). The hepatic fibrosis model by subcutaneous injection of 50%CC14 oil solvent to establish model rats. Rats in the model group injected 50% CC14 solvent (0.2ml/100g) at 2w,3w,4w,5w,6w,7w,8w,9w, lOw and 11w.In each weeks 3-5 model rats selected randomly for liver conventional MRI and T1rho check, then get the original T1rho data into workstation to obtain T1rho values. All the rats in the blank group complete scanning a week after adaptability training. Get the rat liver tissue for pathological examination after MRI scan,The experimental rats were divided into SO phase and S2 phase, S3 phase and S4 phase according to the METAVIR standard.2.MR Imaging equipment, scanning sequence and parametersUsing 3.0T TX Achieva magnetic resonance scanner produced by Philips company and animal coilthe for T1rho scan for experimental animals.Scanning sequence and parameters:the rats were anesthetized and placed in animal coil, ventral pad under the abdomen before scanning the rats to reduce the activity of rats in the progress of scanning. Head advanced, prone position, scan range cover whole liver.Run axial scans T1WI, T2WI and T1rho scanning after 3D positioning.Main parameters of the sequences:(1) T1WI:fast spin echo sequence (TSE). TR/TE 400ms/10ms, FOV 60mmx60mm, thickness 3mm; (2) T2WI:fast spin echo sequence (TSE), TR/TE 1080ms/120ms, FOV 60mmx60mm, thickness 3mm; (3) T1rho, fast gradient echo sequence (TFE), TR/TE 4.9ms/2.4ms.The spin-lock times were 0,10,20,40,60ms and spin-lock frequency was 500HZ, FOV 60mm x60mm, thickness 2mm, flip angle 40°.3.Measurement of T1rho valuesImport the original data processing to workstation.T1rho values are measured via image J (NIH, Bethesda, MD, USA).Choose 5 large levels from the liver.In each levels,5 ROIs were randomly selected and there were totally 25 ROIs obtained from a sample.ROIs ranged from 3 to 4mm2. The average value of the 25 ROIs is regarded as the Tlrho value of this sample.4. Statistical methodsUse SPSS 20.0 statistical software package for data processing.Measurement data were expressed as mean±standard deviation (x±s).ONEWAY-ANOVA was used to test the diffrerence of Tlrho values among each stages.The correlation between Tlrho values and the stages of liver fibrosis was analyzed by Spearman correlation test. ROC curve analysis was used to predict the diagnostic efficacy of Tlrho values in diagnosis of liver fibrosis. The Youden index was used to evaluate the sensitivity and specificity of Tlrho values in predicting the stages of liver fibrosis in rats.ResultsNo liver fibrosis was found in 15 rats of blank group. MRI and pathological examination were done in 43 rats of the model group(7 rats died during the experiment).There were 15 rats in S0,11 rats in S1,12 rats in S2,10 rats in S3 and 10 rats in S4.The Tlrho average values of each stages were 41.234±1.833ms,47.981± 4.213ms,50.516±4.204ms,54.772±4.468ms and 58.119±2.892ms, repectively.Tlrho values were significant diffrent among stages (P<0.05). In liver fibrosis process Tlrho values of rats have highly positive correlation with the stage of liver fibrosis and CPA values,r=0.712,0.562, P<0.01,and showed a moderate positive correlation with inflammation score,r=0.388, P<0.05.Tlrho values have no significant correlation with steatosis and edema(P> 0.05). Area under ROC curve,AUC for Tlrho values to differenciating SO from S1-4 was 0.989, the cut-off point was 45.171, sensitivity was 0.907, specificity was 1, the AUC for S0-1 vs S2-4 was 0.925, cut-off point was 47.192, sensitivity and specificity were 0.938 and 0.846,respectively, AUC for SO-2 vs s3-4 was 0.932, cutoff value was 52.380. The sensitivity and specificity were 0.900 and 0.895, AUC for S0-3 vs S4 was 0.923 and cut-off value was 54.687. The sensitivity and specificity were 1 and 0.854 respectively.Conclusions1.Tlrho values increase with the progression of liver fibrosis in rats, and they have a high degree of correlation.2. Tlrho values were moderately correlated with inflammation score and there is no significant correlation between Tlrho values and steatosis, the factors that affect the Tlrho value are complex. CPA?3.Tlrho values have a high diagnostic efficacy in the diagnosis of liver fibrosis in rats.As a truly non-invasive examination technology, it has high application value in staging of liver fibrosis in rats.PART II Comparison of Tlrho traditional sequence and Tlrho adiabatic sequence in the diagnosis of liver fibrosis in ratsObjectiveTraditional Tlrho sequence and Adiabatic Tlrho sequence were used at 3.0T magnetic resonance on diagnosis of liver fibrosis in rats model for comparing the diagnostic efficiency of staging liver fibrosis, scanning parameters and the quality of the images,and decide which one is more likely suitable for clinical use.Materials and Methods1.Liver fibrosis model and grouping methods65 healthy SD rats were randomly divided into model group (50 rats) and blank group (15 rats). The hepatic fibrosis model by subcutaneous injection of 50%CC14 oil solvent to establish model rats. Rats in the model group injected 50% CC14 solvent (0.2ml/100g) at 2w,3w,4w,5w,6w,7w,8w,9w, lOw and 11w.In each weeks 3-5 model rats selected randomly for liver conventional MRI and Tlrho check, then get the original Tlrho data into workstation to obtain Tlrho values. All the rats in the blank group complete scanning a week after adaptability training. Get the rat liver tissue for pathological examination after MRI scan,The experimental rats were divided into SO phase and S2 phase, S3 phase and S4 phase according to the METAVIR standard.2.MR Imaging equipment, scanning sequence and parametersUsing 3.0T TX Achieva magnetic resonance scanner produced by Philips company and animal coilthe for Tlrho scan for experimental animals.Scanning sequence and parameters:the rats were anesthetized and placed in animal coil, ventral pad pad under the abdomen before scanning the rats to reduce the activity of rats in the progress of scanning. Head advanced, prone position, scan range cover whole liver.Run axial scans T1WI, T2WI and Tlrho scanning after 3D positioning.Main parameters of the sequences:(1) T1WI:fast spin echo sequence (TSE). TR/TE 400ms/10ms, FOV 60mmx60mm, thickness 3mm; (2) T2WI:fast spin echo sequence (TSE), TR/TE 1080ms/120ms, FOV 60mmx60mm, thickness 3mm; (3)traditional Tlrho, fast gradient echo sequence (TFE), TR/TE 4.9ms/2.4ms.The spin-lock times were 0,10,20,40,60ms and spin-lock frequency was 500HZ, FOV 60mmx60mm, thickness 2mm, flip angle 40°.Adiabatic Tlrho,fast gradient echo sequence (TFE), TR/TE 4.2ms/2.1ms. The spin-lock times were 0,27,54ms and spin-lock frequency was 500HZ,FOV 60mmx60mm, thickness 2mm, flip angle 10°.3.Measurement of visual scoreVisual score was categorized as l:Poor,2:Fair,3:Good,4:Excellent by two experienced MR expert.The mean scores was considered as the final score of the samples.4.Measurement of Tlrho valuesImport the original data processing to workstation.Tlrho values are measured via image J (NIH, Bethesda, MD, USA).Choose 5 large levels from the liver.In each levels,5 ROIs were randomly selected and there were totally 25 ROIs obtained from a sample.ROIs ranged from 3 to 4mm2. The average value of the 25 ROIs is regarded as the Tlrho value of this sample. 5.Statistical methodsUse SPSS 20.0 statistical software package for data processing.Measurement data were expressed as mean±standard deviation (x±s).A paired t-test was used to test the average values obtained with continuous wave and adiabatic pulse. ONEWAY-ANOVA was used to test the diffrerence of Tlrho values among each stages.ROC curve analysis was used to predict the diagnostic efficacy of Tlrho values in diagnosis of liver fibrosis. The Youden index was used to evaluate the sensitivity and specificity of Tlrho values in predicting the stages of liver fibrosis in rats.ResultsNo liver fibrosis was found in rats of blank group. MRI and pathological examination were done in 43 rats of the model group(7 rats died during the experiment).There were 15 rats in S0,11 rats in S1,12 rats in S2,10 rats in S3 and 10 rats in S4.. The visual evaluation of the homogeneity of the Tlrho maps resulted in 2.360±0.613 for block pulse locking and 3.401±0.699 for adiabatic pulse locking. Adiabatic spin locking images scored significantly higher compared to block locking (P<0.05). The average Tlrho values of traditional Tlrho for each stages were 41.234±1.833ms,47.981±4.213ms,50.516±4.204ms,54.772±4.468ms and 58.119±2.892ms,respectively.Tlrho values of Adiabatic Tlrho for each stages were 70.679±3.926ms,86.451±9.893ms,94.121±5.517ms,104.001±6.651ms and 111.971±5.146ms,respectively.Tlrho values of both Tlrho sequences were significant diffrent among stages (P<0.05). Area under ROC curve,AUC for traditional Tlrho values to differenciating SO vsSl-4, S0-1 vs S2-4,S0-2 vs S3-4 and S0-3 vs S4 were 0.989,0.924,0.932 and 0.923,respectively.AUC for Adiabatic Tlrho to differentiating SO vsSl-4, S0-1 vs S2-4,S0-2 vs S3-4 and S0-3 vs S4 were 0.992, 0.948,0.967 and 0.963.respectively.Conclusions1. Tlrho values measured by both kinds of Tlrho sequences increased with the progression of hepatic fibrosis in rats, and have positively correlated with the degree of liver fibrosis in rats.2, Both of the traditional Tlrho and Adiabatic Tlrho sequences have high diagnostic efficacy for the diagnosis of liver fibrosis in rats, and Adiabatic Tlrho may be more potential for clinical application than the traditional one. |
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