Noninvasive assessment of liver disease—measurement of hepatic fibrosis using tissue strain imaging

Biomarkers of liver fibrosis

Liver fibrosis is the final common pathway for almost all causes of chronic liver injury. Liver fibrosis is now known to be a dynamic process having significant potential for resolution. Therefore, fibrosis prediction is an essential part of the assessment and management of patients with chronic liver disease. As such, there is strong demand for reliable liver biomarkers that provide insight into disease etiology, diagnosis, therapy, and prognosis in lieu of more invasive approaches such as liver biopsy. Current diagnostic strategies range from use of serum biomarkers to more advanced imaging techniques including transient elastography and magnetic resonance imaging. In addition to these modalities, there are other approaches including the use of novel, but yet to be validated, biomarkers. In this chapter, we discuss the biomarkers of liver fibrosis including the use of invasive and noninvasive biomarkers and disease-specific biomarkers in various chronic liver diseases.

Contrast-enhanced CT quantification of the hepatic fractional extracellular space: correlation with diffuse liver disease severity

OBJECTIVE

The purpose of this study was to determine whether contrast-enhanced CT quantification of the hepatic fractional extracellular space (ECS) correlates with the severity of diffuse liver disease.

MATERIALS AND METHODS

The cases of 70 patients without (46 men, 24 women; mean age, 59.1 years) and 36 patients with (23 men, 13 women; mean age, 63.1 years) cirrhosis who had undergone unenhanced and 10-minute delayed phase contrast-enhanced CT were retrospectively identified. By consensus one experienced radiologist and one trainee measured the CT attenuation of the liver and aorta to estimate the fractional ECS, defined as the ratio of the difference between the attenuation of the liver on 10-minute and unenhanced images to the difference between the attenuation of the aorta on 10-minute and unenhanced images multiplied by 1 minus the hematocrit. Findings were correlated with each patient's Model of End-Stage Liver Disease (MELD) score.

RESULTS

The mean MELD score was higher in patients with than in those without cirrhosis (14.3 ± 7.3 versus 7.20 ± 2.4, p < 0.0001). The mean fractional ECS was significantly greater in patients with cirrhosis than in those without cirrhosis (41.0% ± 9.0% versus 23.8% ± 6.3%, p < 0.0001). The fractional ECS correlated with the MELD score (r = 0.572, p < 0.0001) and was predictive of cirrhosis with an area under the receiver operating characteristic curve of 0.953 (p < 0.0001). The sensitivity and specificity of an expanded fractional ECS greater than 30% for the prediction of cirrhosis were 92% and 83%. Multivariate linear regression revealed that the fractional ECS is complementary to the MELD score as a predictor of cirrhosis (p < 0.0001).

CONCLUSION

Noninvasive contrast-enhanced CT quantification of the fractional ECS correlates with the MELD score, an indicator of the severity of liver disease, and merits further study.

Tissue Doppler imaging and tissue strain imaging for the evaluation of hepatic fibrosis in patients with chronic hepatitis B

We studied the feasibility of evaluating the stages of liver fibrosis with tissue Doppler imaging (TDI) and tissue strain imaging (TSI) for patients with chronic hepatitis B virus infection. One hundred ten patients were divided into two groups: normal adult group (n = 38) and chronic liver disease group (n = 72, patients infected with HBVs). The chronic liver disease group was divided into three subgroups on the basis of the Scheuer scoring system and clinical evidence: mild fibrosis (S0 and S1, n = 11), moderate fibrosis (S2 and S3, n = 27) and cirrhosis (S4 and clinically typical cirrhosis, n = 34) groups. TDI was performed for a chosen oblique section. Four regions of interest (ROIs), A-D, were chosen in the hepatic parenchyma based on the direction of propagation from the heart to the liver. Strain rate curves were obtained on the basis of TDI and TSI findings. Strain peak rates (SPRs) of all ROIs and the differences in times to SPRs for the four ROIs (TA-B, TB-C and TC-D) in the hepatic parenchyma were measured with TDI and TSI. Strain rate curves were analyzed for each ROI. The strain rate curves for the normal adult group were synchronous, whereas those for the chronic liver disease group were asynchronous. SPRs of the ROIs gradually decreased with the progression of liver fibrosis. The SPRs of ROI B significantly correlated with chronic liver disease severity (r = 0.991, p < 0.05). Areas under the curve (AUCs) of the ROI A and ROI B SPRs at the moderate fibrosis and cirrhosis stages were 0.86 ± 0.06, 0.81 ± 0.56 and 0.90 ± 0.65, 0.92 ± 0.04, respectively. The AUC of the SPRs of ROIs A and B correlated better than the platelet/age/phosphatase/α-fetoprotein/aspartate aminotransferase (PAPAS) index for advanced fibrosis. The differences in time to SPRs among the peaks of the four ROIs (TA-B, TB-C and TC-D) gradually increased with the progression of liver fibrosis. TDI and TSI with quantitative measurements using tissue Doppler analysis software (TDIQ, GE Medical Systems, Horten, Norway) provided reliable information for evaluating non-invasive liver fibrosis in patients with chronic hepatitis B.

Hepatic fibrosis: evaluation with semiquantitative contrast-enhanced CT

PURPOSE

To evaluate the feasibility of using contrast material-enhanced computed tomographic (CT) measurements of hepatic fractional extracellular space (fECS) and macromolecular contrast material (MMCM) uptake to measure severity of liver fibrosis.

MATERIALS AND METHODS

All procedures were approved by and executed in accordance with University of California, San Francisco, institutional animal care and use committee regulations. Twenty-one rats that received intragastric CCl(4) for 0-12 weeks were imaged with respiratory-gated micro-CT by using both a conventional contrast material and a novel iodinated MMCM. Histopathologic hepatic fibrosis was graded qualitatively by using the Ishak fibrosis score and quantitatively by using morphometry of the fibrosis area. Hepatic fECS and MMCM uptake were calculated for each examination and correlated with histopathologic findings by using uni- and multivariate linear regressions.

RESULTS

Ishak fibrosis scores ranged from a baseline of 0 in untreated animals to a maximum of 5. Histopathologic liver fibrosis area increased from 0.46% to 3.5% over the same interval. Strong correlations were seen between conventional contrast-enhanced CT measurements of fECS and both the Ishak fibrosis scores (R(2) = 0.751, P < .001) and the fibrosis area (R(2) = 0.801, P < .001). Strong negative correlations were observed between uptake of MMCM in the liver and Ishak fibrosis scores (R(2) = 0.827, P < .001), as well as between uptake of MMCM in the liver and fibrosis area (R(2) = 0.643, P = .001). Multivariate linear regression analysis showed a trend toward independence for fECS and MMCM uptake in the prediction of Ishak fibrosis scores, with an R(2) value of 0.86 (P = .081 and P = .033, respectively).

CONCLUSION

Contrast-enhanced CT measurements of fECS and MMCM uptake are individually capable of being used to estimate the degree of early hepatic fibrosis in a rat model.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112452/-/DC1.

Liver stiffness assessment by tagged MRI of cardiac-induced liver motion

Cirrhosis is an important and growing public health problem, affecting millions of Americans and many more people internationally. A pathological hallmark of the progression to cirrhosis is the development of liver fibrosis, so that monitoring the appearance and progression of liver fibrosis can be used to guide therapy. Here, we report a method to use magnetization-tagged magnetic resonance imaging to measure the cardiac-induced motion and deformation in the liver, as a means for noninvasively assessing liver stiffness, which is related to fibrosis. The initial results show statistically significant differences between healthy and cirrhotic subjects in the direct comparisons of the maximum displacement (mm), and the maximum (P1) and minimum (P2) two-dimensional strains, through the cardiac cycle (3.514 ± 0.793, 2.184 ± 0.611; 0.116 ± 0.043, 0.048 ± 0.011; -0.094 ± 0.020, -0.041 ± 0.015; healthy, cirrhosis, respectively; P < 0.005 for all). There are also significant differences in the displacement-normalized P1 and P2 strains (mm(-1) ) (0.030 ± 0.008, 0.017 ± 0.007; -0.024 ± 0.006, -0.013 ± 0.004; healthy, cirrhosis, respectively; P < 0.005 for all). Therefore, this noninvasive imaging-based method is a promising means to assess liver stiffness using clinically available imaging tools.

New noninvasive assessment of liver fibrosis in chronic hepatitis B: maximal accumulative respiration strain

OBJECTIVE

A novel parameter acquired from conventional B-mode sonographic videos was introduced in this study, and its diagnostic accuracy for evaluation of hepatic fibrosis was investigated.

METHODS

Twenty-eight patients with chronic hepatitis B and 8 patients with hepatic cysts in the right lobe (controls) were enrolled. B-mode sonographic videos of hepatic motion under the ensisternum in the sagittal plane were captured during peaceful breathing. Maximal accumulative respiration strain (MARS) values of hepatic tissue were obtained after image analysis. METAVIR scoring after liver biopsy was considered the standard. First, the relationship between MARS and the fibrotic stage was studied; and second, receiver operating characteristic (ROC) curves were used to assess the accuracy of MARS for evaluation of the fibrotic stage.

RESULTS

When the transducer was placed in the sagittal imaging plane under the ensisternum during the whole respiratory period, the hepatic tissue motion was almost in the same plane. The MARS values (mean +/- SD) were 29.44% +/- 10.44% in the F0 group (no fibrosis; n = 8), 19.30% +/- 9.10% in the F1 group (portal fibrosis without septa; n = 8), 18.09% +/- 7.36% in the F2-F3 group (portal fibrosis with few septa or numerous septa without cirrhosis; n = 12), and 14.16% +/- 4.18% in the F4 group (cirrhosis; n = 8). The Spearman correlation coefficient between MARS and the fibrotic stage was 0.516 (P = .001). The diagnostic accuracy rates, expressed as areas under the ROC curves, were 0.87 for mild fibrosis (F >or= 1), 0.72 for substantial fibrosis (F >or= 2), and 0.75 for cirrhosis (F = 4).

CONCLUSIONS

Maximal accumulative respiration strain attained from B-mode sonographic videos of hepatic tissue is a new, convenient, economical, and promising noninvasive parameter for assessment of hepatic fibrosis in patients with chronic hepatitis B.

Systematic review: non-invasive methods of fibrosis analysis in chronic hepatitis C

BACKGROUND

Accurate determination of the presence and degree of liver fibrosis is essential for prognosis and for planning treatment of patients with chronic hepatitis C virus (HCV). Non-invasive methods of assessing fibrosis have been developed to reduce the need for biopsy.

AIM

To perform a review of these non-invasive measures and their ability to replace biopsy for assessing hepatic fibrosis in patients with chronic HCV.

METHODS

A systematic review of PUBMED and EMBASE was performed through 2008 using the following search terms: HCV, liver, elastography, hepatitis, Fibroscan, SPECT, noninvasive liver fibrosis, ultrasonography, Doppler, MRI, Fibrotest, Fibrosure, Actitest, APRI, Forns and breath tests, alone or in combination.

RESULTS

We identified 151 studies: 87 using biochemical, 57 imaging and seven breath tests either alone or in combination.

CONCLUSIONS

Great strides are being made in the development of accurate non-invasive methods for determination of fibrosis. Although no single non-invasive test or model developed to date can match that information obtained from actual histology (i.e. inflammation, fibrosis, steatosis), combinations of two modalities of non-invasive methods can reliably differentiate between minimal and significant fibrosis, and thereby avoid liver biopsy in a significant percentage of patients.

Can imaging modalities diagnose and stage hepatic fibrosis and cirrhosis accurately?

The accurate diagnosis and staging of hepatic fibrosis is crucial for prognosis and treatment of liver disease. The current gold standard, liver biopsy, cannot be used for population-based screening, and has well known drawbacks if used for monitoring of disease progression or treatment success. Our objective was to assess performance and promise of radiologic modalities and techniques as alternative, noninvasive assessment of hepatic fibrosis. A systematic review was conducted. Six hundred twenty-eight studies were identified via electronic search. One hundred fifty-three papers were reviewed. Most described techniques that could differentiate between cirrhosis or severe fibrosis and normal liver. Accurate staging of fibrosis or diagnosis of mild fibrosis was often not achievable. Ultrasonography is the most common modality used in the diagnosis and staging of hepatic fibrosis. Elastographic measurements, either ultrasonography-based or magnetic resonance-based, and magnetic resonance diffusion weighted imaging, show the most promise for accurate staging of hepatic fibrosis. Most currently available imaging techniques can detect cirrhosis or significant fibrosis reasonably accurately. However, to date only magnetic resonance elastography has been able to stage fibrosis or diagnose mild disease. Utrasonographic elastography and magnetic resonance diffusion weighted appear next most promising.