Correlation between Liver Elasticity by Ultrasound Elastography and Liver Functional Reserve

Mechanical properties of human hepatic tissues to develop liver-mimicking phantoms for medical applications

Using liver phantoms for mimicking human tissue in clinical training, disease diagnosis, and treatment planning is a common practice. The fabrication material of the liver phantom should exhibit mechanical properties similar to those of the real liver organ in the human body. This tissue-equivalent material is essential for qualitative and quantitative investigation of the liver mechanisms in producing nutrients, excretion of waste metabolites, and tissue deformity at mechanical stimulus. This paper reviews the mechanical properties of human hepatic tissues to develop liver-mimicking phantoms. These properties include viscosity, elasticity, acoustic impedance, sound speed, and attenuation. The advantages and disadvantages of the most common fabrication materials for developing liver tissue-mimicking phantoms are also highlighted. Such phantoms will give a better insight into the real tissue damage during the disease progression and preservation for transplantation. The liver tissue-mimicking phantom will raise the quality assurance of patient diagnostic and treatment precision and offer a definitive clinical trial data collection.

E-AHPBA-ESSO-ESSR Innsbruck consensus guidelines for preoperative liver function assessment before hepatectomy

BACKGROUND

Posthepatectomy liver failure (PHLF) contributes significantly to morbidity and mortality after liver surgery. Standardized assessment of preoperative liver function is crucial to identify patients at risk. These European consensus guidelines provide guidance for preoperative patient assessment.

METHODS

A modified Delphi approach was used to achieve consensus. The expert panel consisted of hepatobiliary surgeons, radiologists, nuclear medicine specialists, and hepatologists. The guideline process was supervised by a methodologist and reviewed by a patient representative. A systematic literature search was performed in PubMed/MEDLINE, the Cochrane library, and the WHO International Clinical Trials Registry. Evidence assessment and statement development followed Scottish Intercollegiate Guidelines Network methodology.

RESULTS

Based on 271 publications covering 4 key areas, 21 statements (at least 85 per cent agreement) were produced (median level of evidence 2- to 2+). Only a few systematic reviews (2++) and one RCT (1+) were identified. Preoperative liver function assessment should be considered before complex resections, and in patients with suspected or known underlying liver disease, or chemotherapy-associated or drug-induced liver injury. Clinical assessment and blood-based scores reflecting liver function or portal hypertension (for example albumin/bilirubin, platelet count) aid in identifying risk of PHLF. Volumetry of the future liver remnant represents the foundation for assessment, and can be combined with indocyanine green clearance or LiMAx® according to local expertise and availability. Functional MRI and liver scintigraphy are alternatives, combining FLR volume and function in one examination.

CONCLUSION

These guidelines reflect established methods to assess preoperative liver function and PHLF risk, and have uncovered evidence gaps of interest for future research.

Significance of Shear Wave Dispersion Slope Values Before Versus After Biliary Drainage in Patients With Obstructive Jaundice: A Single-Center Prospective Observational Cohort Study

ABSTRACT

The shear wave dispersion (SWD) slope has become available in the clinical practice and is related to tissue viscosity. However, clinical evaluation using SWD was not yet performed for obstructive jaundice. We aimed to evaluate the change of SWD values between before and after biliary drainage in patients with obstructive jaundice. This prospective observational cohort study evaluated 20 patients with obstructive jaundice who underwent biliary drainage. The SWD and liver elasticity values were measured before versus after biliary drainage, comparing between days -5 and 0 (day 0), days 1 and 3 (day 2), and days 6 and 8 (day 7). The mean ± SD values of SWD measured at day 0, day 2, and day 7 were 15.3 ± 2.7, 14.2 ± 3.3, and 13.3 ± 2.4 m/s/kHz, respectively. Dispersion slope values were decreased significantly from day 0 to day 2, from day 2 to day 7, and from day 0 to day 7 ( P < 0.05). Liver elasticity levels and serum hepatobiliary enzymes were additionally decreased significantly over time after biliary drainage. The correlations between SWD and liver elasticity values were strong ( r = 0.91, P < 0.01). In conclusion, t he SWD values decreased significantly over time after biliary drainage concomitant with liver elasticity.

High correlation of hepatic shear wave velocity with esophageal varices complication rate in patients with chronic liver diseases

BACKGROUND

Histological evaluation by liver biopsy is considered the gold standard for assessing liver disease; however, it is highly invasive. Non-invasive liver stiffness measurement by shear wave elastography (SWE) is effective for evaluating the hepatic fibrosis stage and related diseases. In this study, we investigated the correlations of liver stiffness with hepatic inflammation/fibrosis, functional hepatic reserve, and related diseases in patients with chronic liver disease (CLD).

METHODS

Shear wave velocity (Vs) values were measured using point SWE in 71 patients with liver disease from 2017 to 2019. Liver biopsy specimens and serum biomarkers were collected at the same time, and splenic volume was measured using computed tomography images with the software Ziostation2. Esophageal varices (EV) were evaluated by upper gastrointestinal endoscopy.

RESULTS

Among CLD-related function and complications, Vs values were highly correlated with liver fibrosis and EV complication rates. The median Vs values for liver fibrosis grades F0, F1, F2, F3, and F4 were 1.18, 1.34, 1.39, 1.80, and 2.12 m/s, respectively. Comparison of receiver operating characteristic (ROC) curves to predict cirrhosis showed that area under the ROC (AUROC) curve for Vs values was 0.902, which was not significantly different from the AUROCs for the FIB-4 index, platelet count, hyaluronic acid, or type IV collagen 7S, while it was significantly different from the AUROC for mac-2 binding protein glycosylation isomer (M2BPGi) (P < 0.01). Comparison of ROC curves to predict EV showed that the AUROC for Vs values was 0.901, which was significantly higher than the AUROCs for FIB-4 index (P < 0.05), platelet count (P < 0.05), M2BPGi (P < 0.01), hyaluronic acid (P < 0.05), and splenic volume (P < 0.05). In patients with advanced liver fibrosis (F3 + F4), there was no difference in blood markers and splenic volume, while Vs value was significantly higher in patients with EV (P < 0.01).

CONCLUSIONS

Hepatic shear wave velocity was highly correlated with EV complication rates in chronic liver diseases as compared to blood markers and splenic volume. In advanced CLD patients, Vs values of SWE are suggested to be effective in predicting the appearance of EV noninvasively.

Feasibility of liver stiffness measured using two-dimensional shear wave elastography in assessing preoperative liver function for patients with hepatocellular carcinoma

OBJECTIVES

To evaluate the feasibility of liver stiffness (LS) measured using two-dimensional shear wave elastography (2D SWE) in assessing preoperative liver function for patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A total of 143 patients who underwent surgical resection for HCC between August 2018 and December 2019 were enrolled prospectively. LS measurement, liver function tests including serum biochemical indicators, and indocyanine green (ICG) clearance test were performed preoperatively. Child-Pugh (CP) score, Albumin-bilirubin (ALBI) score and Model for End-Stage Liver Disease score were calculated. ICG retention rate at 15 min (ICG R15) and ICG elimination rate constant (ICG K) were determined automatically. Fibrosis stage was determined based on pathological findings. The association between LS and serum biochemical indicators, liver function scores, and the ICG results were analyzed.

RESULTS

Weak to moderate correlations were identified between LS and biochemical indicators of liver function (all p < 0.01). Weak correlation was identified between LS and CP score, and between LS and ALBI score (all p < 0.001). Moderate correlation was identified between LS and ICG R15 (Pearson r = 0.62, p < 0.001), and between LS and ICG K value (Pearson r =  - 0.49, p < 0.001). The best cutoff of LS to discriminate a normal ICG R15 was 10.6 kPa, with area under the curve (AUC), sensitivity, specificity of 0.874, 0.900 and 0.724, respectively.

CONCLUSIONS

LS determined using 2D SWE could be a potential tool for the preoperative evaluation of liver function in patients with HCC.

Hepatectomy-Induced Alterations in Hepatic Perfusion and Function - Toward Multi-Scale Computational Modeling for a Better Prediction of Post-hepatectomy Liver Function

Liver resection causes marked perfusion alterations in the liver remnant both on the organ scale (vascular anatomy) and on the microscale (sinusoidal blood flow on tissue level). These changes in perfusion affect hepatic functions via direct alterations in blood supply and drainage, followed by indirect changes of biomechanical tissue properties and cellular function. Changes in blood flow impose compression, tension and shear forces on the liver tissue. These forces are perceived by mechanosensors on parenchymal and non-parenchymal cells of the liver and regulate cell-cell and cell-matrix interactions as well as cellular signaling and metabolism. These interactions are key players in tissue growth and remodeling, a prerequisite to restore tissue function after PHx. Their dysregulation is associated with metabolic impairment of the liver eventually leading to liver failure, a serious post-hepatectomy complication with high morbidity and mortality. Though certain links are known, the overall functional change after liver surgery is not understood due to complex feedback loops, non-linearities, spatial heterogeneities and different time-scales of events. Computational modeling is a unique approach to gain a better understanding of complex biomedical systems. This approach allows (i) integration of heterogeneous data and knowledge on multiple scales into a consistent view of how perfusion is related to hepatic function; (ii) testing and generating hypotheses based on predictive models, which must be validated experimentally and clinically. In the long term, computational modeling will (iii) support surgical planning by predicting surgery-induced perfusion perturbations and their functional (metabolic) consequences; and thereby (iv) allow minimizing surgical risks for the individual patient. Here, we review the alterations of hepatic perfusion, biomechanical properties and function associated with hepatectomy. Specifically, we provide an overview over the clinical problem, preoperative diagnostics, functional imaging approaches, experimental approaches in animal models, mechanoperception in the liver and impact on cellular metabolism, omics approaches with a focus on transcriptomics, data integration and uncertainty analysis, and computational modeling on multiple scales. Finally, we provide a perspective on how multi-scale computational models, which couple perfusion changes to hepatic function, could become part of clinical workflows to predict and optimize patient outcome after complex liver surgery.

The impact of elastography with virtual touch quantification of future remnant liver before major hepatectomy

Background

Liver elastography with virtual touch quantification (VTQ) measures the velocity of the shear wave generated by a short-duration acoustic force impulse, with values expressed in units of velocity (m/s). VTQ can evaluate right or left hepatic lobes separately. VTQ might be appropriate for the evaluation of future remnant liver after hepatectomy.

Methods

We analyzed 95 patients underwent liver elastography with VTQ and both future remnant liver and resected side before hepatectomy of more than two sections, except for central bisectionectomy. We divided the patients into a high VTQ group (≥1.52 m/s, n=37, 39%) and a low VTQ group (<1.52 m/s, n=58, 61%) according to the VTQ of future remnant liver. Transient elastography could not be performed in 22 cases due to tumor size. We defined the group with liver stiffness measurement (LSM) ≥7.9 kPa as the high LSM group (n=29, 40%) and those with LSM <7.9 kPa as the low LSM group (n=44, 60%). We investigated the outcome after hepatectomy and the correlations between the VTQ of future remnant liver and other indicators for hepatic fibrosis.

Results

The high VTQ group showed significantly higher postoperative ascites (19% vs. 3%; P=0.01), pathological fibrosis (19% vs. 5%; P=0.03), and rates of patients with postoperative T-bil ≥2.0 mg/dL (70% vs. 40%; P<0.01). The high LSM group showed no significant postoperative outcomes compared to the low LSM group. The high VTQ group showed a higher frequency of male gender (78% vs. 57%; P=0.03), higher indocyanine green retention rate at 15 min (ICGR15) (10.5% vs. 6.3%; P<0.01), hyaluronic acid (100 vs. 67 ng/mL; P=0.02), type IV collagen 7S (7.6 vs. 5.1 ng/mL; P<0.01), Mac-2 binding protein glycan isomer (M2BPGi) (1.19 vs. 1.00; P=0.01), Fibrosis-4 (FIB-4) index (2.25 vs. 1.76; P=0.01), and aspartate aminotransferase to platelet ratio index (APRI) score (0.64 vs. 0.41; P<0.01). We also observed an especially strong positive correlation between the high VTQ and hyaluronic acid or type IV collagen 7S.

Conclusions

Elastography with VTQ for future remnant liver before major hepatectomy is an accurate and useful method as a preoperative evaluation.

Estimation of liver elasticity using the finite element method and four-dimensional computed tomography images as a biomarker of liver fibrosis

PURPOSE

Current radiotherapy planning procedures are generally designed based on anatomical information only and use computed tomography (CT) images that do not incorporate organ-functional information. In this study, we developed a method for estimating liver elasticity using the finite element method (FEM) and four-dimensional CT (4DCT) images acquired during radiotherapy planning, and we subsequently evaluated its feasibility as a biomarker for liver fibrosis.

MATERIALS AND METHODS

Twenty patients who underwent 4DCT and ultrasound-based transient elastography (UTE) were enrolled. All patients had chronic liver disease or cirrhosis. Liver elasticity measurements of the UTE were performed on the right lobe of the patient's liver in 20 patients. The serum biomarkers of the aspartate aminotransferase (AST)-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4) were available in 18 of the 20 total patients, which were measured within 1 week after undergoing 4DCT. The displacement between the 4DCT images obtained at the endpoints of exhalation and inspiration was determined using the actual (via deformable image registration) and simulated (via FEM) respiration-induced displacement. The elasticity of each element of the liver model was optimized by minimizing the error between the actual and simulated respiration-induced displacement. Then, each patient's estimated liver elasticity was defined as the mean Young's modulus of the liver's right lobe and that of the whole liver using the estimated elasticity map. The estimated liver elasticity was evaluated for correlations with the elasticity obtained via UTE and with two serum biomarkers (APRI and FIB-4).

RESULTS

The mean ± standard deviation (SD) of the errors between the actual and simulated respiration-induced displacement in the liver model was 0.54 ± 0.33 mm. The estimated liver's right lobe elasticity was statistically significantly correlated with the UTE (r = 0.87, P < 0.001). Furthermore, the estimated whole liver elasticity was statistically significantly correlated with the UTE (r = 0.84, P < 0.001), APRI score (r = 0.62, P = 0.005), and FIB-4 score (r = 0.54, P = 0.021).

CONCLUSION

In this study, liver elasticity was estimated through FEM-based simulation and actual respiratory-induced liver displacement obtained from 4DCT images. Furthermore, we assessed that the estimated elasticity of the liver's right lobe was strongly correlated with the UTE. Therefore, the estimated elasticity has the potential to be a feasible imaging biomarker for assessing liver fibrosis using only 4DCT images without additional inspection or equipment costs. Because our results were derived from a limited sample of 20 patients, it is necessary to evaluate the accuracy of elasticity estimation for each liver segment on larger groups of biopsied patients to utilize liver elasticity information for radiotherapy planning.