Nondiseased liver stiffness measured by shear wave elastography: a pilot study

Comparison of the Behavior of 3D-Printed Endothelial Cells in Different Bioinks

Biomaterials with characteristics similar to extracellular matrix and with suitable bioprinting properties are essential for vascular tissue engineering. In search for suitable biomaterials, this study investigated the three hydrogels alginate/hyaluronic acid/gelatin (Alg/HA/Gel), pre-crosslinked alginate di-aldehyde with gelatin (ADA-GEL), and gelatin methacryloyl (GelMA) with respect to their mechanical properties and to the survival, migration, and proliferation of human umbilical vein endothelial cells (HUVECs). In addition, the behavior of HUVECs was compared with their behavior in Matrigel. For this purpose, HUVECs were mixed with the inks both as single cells and as cell spheroids and printed using extrusion-based bioprinting. Good printability with shape fidelity was determined for all inks. The rheological measurements demonstrated the gelling consistency of the inks and shear-thinning behavior. Different Young's moduli of the hydrogels were determined. However, all measured values where within the range defined in the literature, leading to migration and sprouting, as well as reconciling migration with adhesion. Cell survival and proliferation in ADA-GEL and GelMA hydrogels were demonstrated for 14 days. In the Alg/HA/Gel bioink, cell death occurred within 7 days for single cells. Sprouting and migration of the HUVEC spheroids were observed in ADA-GEL and GelMA. Similar behavior of the spheroids was seen in Matrigel. In contrast, the spheroids in the Alg/HA/Gel ink died over the time studied. It has been shown that Alg/HA/Gel does not provide a good environment for long-term survival of HUVECs. In conclusion, ADA-GEL and GelMA are promising inks for vascular tissue engineering.

Biophysical Approaches for Applying and Measuring Biological Forces

Over the past decades, increasing evidence has indicated that mechanical loads can regulate the morphogenesis, proliferation, migration, and apoptosis of living cells. Investigations of how cells sense mechanical stimuli or the mechanotransduction mechanism is an active field of biomaterials and biophysics. Gaining a further understanding of mechanical regulation and depicting the mechanotransduction network inside cells require advanced experimental techniques and new theories. In this review, the fundamental principles of various experimental approaches that have been developed to characterize various types and magnitudes of forces experienced at the cellular and subcellular levels are summarized. The broad applications of these techniques are introduced with an emphasis on the difficulties in implementing these techniques in special biological systems. The advantages and disadvantages of each technique are discussed, which can guide readers to choose the most suitable technique for their questions. A perspective on future directions in this field is also provided. It is anticipated that technical advancement can be a driving force for the development of mechanobiology.

Ex Vivo Evaluation of Mechanical Anisotropic Tissues with High-Frequency Ultrasound Shear Wave Elastography

The use of imaging devices to assess directional mechanics of tissues is highly desirable. This is because the directional mechanics depend on fiber orientation, and altered directional mechanics are closely related to the pathological status of tissues. However, measuring directional mechanics in tissues with high-stiffness is challenging due to the difficulty of generating localized displacement in these tissues using acoustic radiation force, a general method for generating displacement in ultrasound-based elastography. In addition, common ultrasound probes do not provide rotational function, which makes the measurement of directional mechanics inaccurate and unreliable. Therefore, we developed a high-frequency ultrasound mechanical wave elastography system that can accommodate a wide range of tissue stiffness and is also equipped with a motorized rotation stage for precise imaging of directional mechanics. A mechanical shaker was applied to the elastography system to measure tissues with high-stiffness. Phantom and ex vivo experiments were performed. In the phantom experiments, the lateral and axial resolution of the system were determined to be 144 μm and 168 μm, respectively. In the ex vivo experiments, we used swine heart and cartilage, both of which are considered stiff. The elastography system allows us to acquire the directional mechanics with high angular resolution in the heart and cartilage. The results demonstrate that the developed elastography system is capable of imaging a wide range of tissues and has high angular resolution. Therefore, this system might be useful for the diagnostics of mechanically anisotropic tissues via ex vivo tests.

Comparison of shear wave elastography (supersonic) with liver biopsy in a cohort of patients from a medium-income country: an observational study

INTRODUCTION

shear-wave elastography is a non-invasive diagnostic test that calculates the degree of liver fibrosis by measuring liver elasticity. This technique was recently introduced in Colombia. Thus, cutoff points delineating the change between fibrosis stages (using the Metavir scale) have not been previously defined in our patient population.

PATIENTS AND METHODS

a retrospective study was performed of patients who had undergone two-dimensional shear-wave elastography (2D-SWE) and liver biopsy (LB) between June 2010 and June 2018 at a private outpatient hepatology center in Bogota, Colombia. We used a training dataset (subjects with time between biopsy and 2D-SWE of ≤ 6 months) to establish diagnostic cutoff values and a test dataset (subjects with time between biopsy and 2D-SWE of > 6 months) to validate our results.

RESULTS

a total of 453 subjects (training dataset, n = 153; test dataset, n = 300) were included. In the training dataset, the cutoff points were 7.6, 8.4, 9.5 and 10.9 kPa, and the areas under the curve were 0.75, 0.83, 0.89 and 0.94 for mild fibrosis, significant fibrosis, advanced fibrosis and cirrhosis, respectively. In the test dataset, the areas under the curve were 0.77, 0.78, 0.83 and 0.89 for mild fibrosis, significant fibrosis, advanced fibrosis, and cirrhosis, respectively.

CONCLUSION

two-dimensional shear-wave elastography was reliable and useful for the non-invasive evaluation of liver fibrosis, particularly in patients with advanced fibrosis and cirrhosis. Cutoff points for fibrosis in a Hispanic population were described.

Elastografía en tiempo real (Supersonic), experiencia de un centro en Bogotá

Introducción: la elastografía en tiempo real, 2D-SWE (Supersonic), es una prueba no invasiva que se utiliza para determinar la elasticidad del hígado y, de esa forma, calcular el grado de fibrosis hepática. En Colombia, la prueba se introdujo en 2016 y no existen hasta el momento estudios del comportamiento de la prueba en todos los pacientes hepáticos, solo se han publicado en pacientes sanos y cirróticos. Objetivo: analizar la experiencia de la aplicación de la elastografía en tiempo real, en sujetos atendidos en el centro de enfermedades hepáticas y digestivas de Bogotá, Colombia. Materiales y métodos: estudio descriptivo retrospectivo de una cohorte de sujetos atendidos entre marzo de 2016 y julio de 2017. Se realizó una historia clínica completa y una prueba de elastografía en tiempo real (Supersonic). Resultados: se incluyeron 654 sujetos, con una mediana de edad de 55 años (rango intercuartílico [RIC]: 45-64). La mediana de valores de fibrosis expresada en kilopascales (kPs) fue de 8,3, con un promedio de 5 mediciones. Se observó una diferencia significativa en el grado de fibrosis entre los grupos de edad y en relación con el diagnóstico final, donde se evidenció una mayor fibrosis en el grupo de enfermedades colestásicas (autoinmune, colangitis biliar primaria [CBP] y superposición autoinmune-CBP). La tasa global de fracaso fue menor al 1 %. Conclusiones: es la primera descripción del comportamiento de la prueba a nivel nacional. Los valores de rigidez hepática observados en los diferentes estadios demuestran la utilidad de la prueba para la determinación de la fibrosis hepática en pacientes con diferentes patologías.

Ionically and Enzymatically Dual Cross-Linked Oxidized Alginate Gelatin Hydrogels with Tunable Stiffness and Degradation Behavior for Tissue Engineering

Hydrogels that allow for the successful long-term in vitro culture of cell-biomaterial systems to enable the maturation of tissue engineering constructs are highly relevant in regenerative medicine. Naturally derived polysaccharide-based hydrogels promise to be one material group with enough versatility and chemical functionalization capability to tackle the challenges associated with long-term cell culture. We report a marine derived oxidized alginate, alginate dialdehyde (ADA), and gelatin (GEL) system (ADA-GEL), which is cross-linked via ionic (Ca²⁺) and enzymatic (microbial transglutaminase, mTG) interaction to form dually cross-linked hydrogels. The cross-linking approach allowed us to tailor the stiffness of the hydrogels in a wide range (from <5 to 120 kPa), without altering the initial ADA and GEL hydrogel chemistry. It was possible to control the degradation behavior of the hydrogels to be stable for up to 30 days of incubation. Increasing concentrations of mTG cross-linker solutions allowed us to tune the degradation behavior of the ADA-GEL hydrogels from fast (<7 days) to moderate (14 days) and slow (>30 days) degradation kinetics. The cytocompatibility of mTG cross-linked ADA-GEL was assessed using NIH-3T3 fibroblasts and ATDC-5 mouse teratocarcinoma cells. Both cell types showed highly increased cellular attachment on mTG cross-linked ADA-GEL in comparison to Ca²⁺ cross-linked hydrogels. In addition, ATDC-5 cells showed a higher proliferation on mTG cross-linked ADA-GEL hydrogels in comparison to tissue culture polystyrene control substrates. Further, the attachment of human umbilical vein endothelial cells (HUVEC) on ADA-GEL (+) mTG was confirmed, proving the suitability of mTG+Ca²⁺ cross-linked ADA-GEL for several cell types. Summarizing, a promising platform to control the properties of ADA-GEL hydrogels is presented, with the potential to be applied in long-term cell culture investigations such as cartilage, bone, and blood-vessel engineering, as well as for biofabrication.

Supersonic shear imaging for the diagnosis of liver fibrosis and portal hypertension in liver diseases: a meta-analysis

BACKGROUND AND AIMS

The meta-analysis aimed to summarize the technical success rate of supersonic shear imaging (SSI) and to evaluate the diagnostic performance of liver and spleen stiffness measurement (LSM and SSM) with SSI for the detection of liver fibrosis, portal hypertension, and gastroesophageal varices in liver diseases.

METHODS

PubMed, EMBASE, and Cochrane Library databases were searched. Technical success rate of SSI was pooled. Area under curve (AUC), sensitivity, and specificity with corresponding 95% confidence interval (CI) were calculated.

RESULTS

Included studies regarding the diagnostic performance of SSI for liver fibrosis, portal hypertension, and esophageal varices numbered 28, 4, and 4 respectively. The pooled technical success rates of LSM and SSM were 95.3% and 75.5%, respectively. The AUC, sensitivity, and specificity of LSM/SSM for different stages of liver fibrosis were 0.85-0.94, 0.7-0.89, and 0.82-0.92, respectively. The AUC, sensitivity, and specificity of LSM were 0.84 (95%CI = 0.8-0.86), 0.79 (95%CI = 0.7-0.85), and 0.82 (95%CI = 0.72-0.88) for clinically significant portal hypertension, 0.85 (95%CI = 0.82-0.88), 0.8 (95%CI = 0.68-0.88), and 0.8 (95%CI = 0.6-0.92) for any varices, and 0.86 (95%CI = 0.83-0.89), 0.86 (95%CI = 0.76-0.92), and 0.61 (95%CI = 0.35-0.83) for high-risk varices, respectively.

CONCLUSIONS

LSM with SSI had a high diagnostic accuracy for liver fibrosis, but a moderate diagnostic accuracy for portal hypertension and esophageal varices.

Assessment of the mechanical properties of the muscle-tendon unit by supersonic shear wave imaging elastography: a review

This review aimed to describe the state of the art in muscle-tendon unit (MTU) assessment by supersonic shear wave imaging (SSI) elastography in states of muscle contraction and stretching, during aging, and in response to injury and therapeutic interventions. A consensus exists that MTU elasticity increases during passive stretching or contraction, and decreases after static stretching, electrostimulation, massage, and dry needling. There is currently no agreement regarding changes in the MTU due to aging and injury. Currently, the application of SSI for the purpose of diagnosis, rehabilitation, and physical training remains limited by a number of issues, including the lack of normative value ranges, the lack of consensus regarding the appropriate terminology, and an inadequate understanding of the main technical limitations of this novel technology.

Optimal Acquisition Number for Hepatic Shear Wave Velocity Measurements in Children

OBJECTIVE

To investigate the minimum optimal acquisition number of hepatic shear wave velocities (SWVs) on ultrasound elastography in children.

MATERIALS AND METHODS

We prospectively performed hepatic supersonic shear wave elastography in children of four groups (group A-C, healthy children, group A with 0-5 years old; group B with 6-10 years old; group C with 11-18 years old; and group D, children with previous Kasai operation) with free breathing (FB) and breath holding (BH) status, if possible. SWVs were measured fifteen times for each child at a 4 cm depth for the right lobe using a 1-6 MHz convex transducer. Mean SWVs from three, five, and seven acquisitions were compared to the mean SWV from fifteen measurements, using an intraclass correlation coefficient (ICC) analyzed with the 1,000 times bootstrap method.

RESULTS

Total eighty-eight children were included (25 children in group A, 30 children in group B, 21 children in group C, and 12 children in group D). The mean SWVs from fifteen measurements in FB status were 5.5 ± 1.3 kPa for groups A-C together and 8.0 ± 2.2 kPa for group D. For all groups together, mean SWVs from the three (ICC 0.944 and 0.937), five (ICC 0.958 and 0.938) and seven (ICC 0.969 and 0.941) acquisitions demonstrated almost perfect agreement with the reference of fifteen acquisitions in both FB and BH status, respectively. A subgroup analysis showed three measurements were in almost perfect agreement during FB for groups B-D and strong agreement (ICC 0.675) for group A.

CONCLUSION

Three acquisitions can be enough for hepatic SWVs in children more than 6 years old regardless of breathing status or hepatic pathology. More acquisitions are recommended for children under the age of 5 years during FB.

How many times should we repeat measuring liver stiffness using shear wave elastography?: 5-repetition versus 10-repetition protocols

The purpose of this study is to evaluate whether a 5-repetition liver stiffness (LS) measurement as the standard protocol of shear wave elastography (SWE) is comparable to a conventional 10-repetition measurement protocol and to identify factors that influence the reliability of the 5-repetition protocol. A total of 346 patients (mean, 48.0years; range, 15-81years, M:F=192:154) who underwent SWE were enrolled. The median, first quartile, third quartile, and interquartile range divided by the median (IQR/M) of LS measurement were calculated and compared between 5-repetition and 10-repetition protocols. Subgroup analyses were also performed to identify factors associated with measurement reliability. The overall mean LS from the 10-repetition protocol was 7.97kPa, which was not significantly different from the mean LS of the 5-repetition protocol (7.91kPa; p=0.192). However, the third quartile and IQR/M values of the two groups were significantly different from each other (p=0.003 and <0.001). Subgroup analysis revealed that the 5-repetition results were significantly different from the 10-repetition results in the fatty liver and high LS subgroups. Therefore, the 5-repetition SWE measurement protocol can replace the conventional 10-repetition protocol, with the exception of patients with fatty liver disease or an LS value higher than 10kPa.

Liver Fibrosis Evaluation Using Real-time Shear Wave Elastography in Hepatitis C-Monoinfected and Human Immunodeficiency Virus/Hepatitis C-Coinfected Patients

OBJECTIVES

A few studies have evaluated real-time shear wave elastography (SWE) for assessing liver fibrosis by measuring liver stiffness in patients with chronic hepatitis C virus (HCV) infection, but they excluded human immunodeficiency virus/HCV-coinfected patients. We investigated the diagnostic performance of liver stiffness measured by SWE as a noninvasive predictor of liver fibrosis in HCV using liver biopsy as a reference standard, including monoinfected and coinfected patients.

METHODS

We measured liver stiffness in patients with HCV undergoing liver biopsy (METAVIR fibrosis staging).

RESULTS

Eighty patients (53 monoinfected and 27 coinfected) were included. There was a significant correlation between liver stiffness and fibrosis stage (ρ = 0.685; P < .001). Areas under the receiver operating characteristic curve were 0.841, 0.879, and 0.975 when comparing fibrosis stages F0-F1 versus F2-F4, F0-F2 versus F3-F4, and F0-F3 versus F4, respectively. Suggested cutoff values were 8.5 kPa for F2, 10.4 kPa for F3, and 11.3 kPa for F4, with sensitivity and specificity of 81% and 84%, 81% and 95%, and 100% and 90%. There was no significant difference between the liver stiffness of monoinfected and coinfected patients (P = .453). When combining SWE with the fibrosis-4 score, accuracy increased from 82% to 88% and from 88% to 96%, with incongruent results of 26% and 29%, for F0-F1 versus F2-F4 and F0-F2 versus F3-F4.

CONCLUSIONS

Shear wave elastography of the liver is an effective noninvasive predictor of liver fibrosis in patients with HCV. There was no significant difference between monoinfected and coinfected patients; hence, the same cutoff values can be used for both groups. Combination of SWE with the fibrosis-4 score leads to higher accuracy, although at the expense of inconclusive results in some patients.

Streamlining Screening to Treatment: The Hepatitis C Cascade of Care at Kaiser Permanente Mid-Atlantic States

Hepatitis C virus (HCV) screening is recommended for patients at risk and/or born during 1945-1965, but screening gaps persist. This new program screens target populations and enhances care linkage for chronically HCV-infected patients. Kaiser Permanente Mid-Atlantic States created a comprehensive HCV screening pathway, supported by a HCV care coordinator. The testing pathway includes HCV antibody (Ab), automatic HCV RNA for Ab-positive patients, coinfection and liver health tests, vibration-controlled transient elastography (VCTE), and a physician referral. A total of 11 200 patients were screened; 3.25% were HCV Ab positive, and 100% of Ab-positive patients received HCV RNA testing. Of HCV Ab-positive patients, 75.9% had chronic HCV, of which 80.8% underwent VCTE. HCV diagnosis was communicated to 94% of patients, and 70.9% had HCV documented in the electronic health record. The pathway shows promise in closing gaps, including improving HCV RNA testing, communicating diagnoses, and assessing liver fibrosis. Improved testing and linkage could increase curative treatment access.

Quantitative measurement of elasticity of the appendix using shear wave elastography in patients with suspected acute appendicitis

INTRODUCTION

Shear wave elastography (SWE) has not been studied for diagnosing appendicitis. We postulated that an inflamed appendix would become stiffer than a normal appendix. We evaluated the elastic modulus values (EMV) by SWE in healthy volunteers, patients without appendicitis, and patients with appendicitis. We also evaluated diagnostic ability of SWE for differentiating an inflamed from a normal appendix in patients with suspected appendicitis.

MATERIALS AND METHODS

Forty-one patients with clinically suspected acute appendicitis and 11 healthy volunteers were prospectively enrolled. Gray-scale ultrasonography (US), SWE and multi-slice computed tomography (CT) were performed. The EMV was measured in the anterior, medial, and posterior appendiceal wall using SWE, and the highest value (kPa) was recorded.

RESULTS

Patients were classified into appendicitis (n = 30) and no appendicitis groups (n = 11). One case of a negative appendectomy was detected. The median EMV was significantly higher in the appendicitis group (25.0 kPa) compared to that in the no appendicitis group (10.4 kPa) or in the healthy controls (8.3 kPa) (p<0.001). Among SWE and other US and CT features, CT was superior to any conventional gray-scale US feature or SWE. Either the CT diameter criterion or combined three CT features predicted true positive in 30 and true negative in 11 cases and yielded 100% sensitivity and 100% specificity. An EMV of 12.5 kPa for the stiffest region of the appendix predicted true positive in 28, true negative in 11, and false negative in two cases. The EMV (≥12.5 kPa) yielded 93% sensitivity and 100% specificity.

CONCLUSION

Our results suggest that EMV by SWE helps distinguish an inflamed from a normal appendix. Given that SWE has high specificity, quantitative measurement of the elasticity of the appendix may provide complementary information, in addition to morphologic features on gray-scale US, in the diagnosis of appendicitis.

Principles and clinical application of ultrasound elastography for diffuse liver disease

Accurate assessment of the degree of liver fibrosis is important for estimating prognosis and deciding on an appropriate course of treatment for cases of chronic liver disease (CLD) with various etiologies. Because of the inherent limitations of liver biopsy, there is a great need for non-invasive and reliable tests that accurately estimate the degree of liver fibrosis. Ultrasound (US) elastography is considered a non-invasive, convenient, and precise technique to grade the degree of liver fibrosis by measuring liver stiffness. There are several commercial types of US elastography currently in use, namely, transient elastography, acoustic radiation force impulse imaging, supersonic shear-wave imaging, and real-time tissue elastography. Although the low reproducibility of measurements derived from operator-dependent performance remains a significant limitation of US elastography, this technique is nevertheless useful for diagnosing hepatic fibrosis in patients with CLD. Likewise, US elastography may also be used as a convenient surveillance method that can be performed by physicians at the patients' bedside to enable the estimation of the prognosis of patients with fatal complications related to CLD in a non-invasive manner.