Liquid-Liver Phantom

Morr, Anna Sophie; Herthum, Helge; Schrank, Felix; Anders, Matthias S.; Lerchbaumer, Markus Herbert; Müller, Hans-Peter; Fischer, Thomas; Jenderka, Klaus-Vitold; Hansen, Hendrik H.G.; Janmey, Paul A.; Braun, Jürgen; Sack, Ingolf; Tzschätzsch, Heiko

doi:10.1097/rli.0000000000000862

Cited by 19 publications

(13 citation statements)

References 46 publications

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“…Therefore, we classified livers according to their mechanical properties. The clustering in two groups based on the cutoff value of 1.6 m/s for the liver SWS agrees with SWS values of a healthy human liver, i.e., approximately 1.4 m/s for 30-60 Hz when considering the dispersion of SWS in the liver as analyzed by Morr et al (2022). This biomechanical classification revealed that stiff livers differ significantly from soft livers in their metabolic capacities.…”

Section: Discussionsupporting

confidence: 68%

On the relationship between metabolic capacities and in vivo viscoelastic properties of the liver

Shahryari

Keller

Meierhofer

et al. 2023

Front. Bioeng. Biotechnol.

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The liver is the central metabolic organ. It constantly adapts its metabolic capacity to current physiological requirements. However, the relationship between tissue structure and hepatic function is incompletely understood; this results in a lack of diagnostic markers in medical imaging that can provide information about the liver’s metabolic capacity. Therefore, using normal rabbit livers, we combined magnetic resonance elastography (MRE) with proteomics-based kinetic modeling of central liver metabolism to investigate the potential role of MRE for predicting the liver’s metabolic function in vivo. Nineteen New Zealand white rabbits were investigated by multifrequency MRE and positron emission tomography (PET). This yielded maps of shear wave speed (SWS), penetration rate (PR) and standardized uptake value (SUV). Proteomic analysis was performed after the scans. Hepatic metabolic functions were assessed on the basis of the HEPATOKIN1 model in combination with a model of hepatic lipid-droplet metabolism using liquid chromatography–mass spectrometry. Our results showed marked differences between individual livers in both metabolic functions and stiffness properties, though not in SUV. When livers were divided into ‘stiff’ and ‘soft’ subgroups (cutoff SWS = 1.6 m/s), stiff livers showed a lower capacity for triacylglycerol storage, while at the same time showing an increased capacity for gluconeogenesis and cholesterol synthesis. Furthermore, SWS was correlated with gluconeogenesis and PR with urea production and glutamine exchange. In conclusion, our study indicates a close relationship between the viscoelastic properties of the liver and metabolic function. This could be used in future studies to predict non-invasively the functional reserve capacity of the liver in patients.

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Section: Discussionsupporting

confidence: 68%

On the relationship between metabolic capacities and in vivo viscoelastic properties of the liver

Shahryari

Keller

Meierhofer

et al. 2023

Front. Bioeng. Biotechnol.

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“…The setup we used in this study was less biased than other inversion-based MRE techniques (46) due to the cylinder geometry of the samples and the noiseinsensitive, analytical solution for elasticity reconstruction. The consistency of our method was confirmed in a wellcharacterized tissue-mimicking phantom providing values in agreement with shear oscillatory rheometry (47). Due to this consistency, tabletop MRE was used in previous studies (41,(48)(49)(50) as a reference method and was employed here without further calibration.…”

Section: Discussionsupporting

confidence: 60%

Ex vivo magnetic resonance elastography of the small bowel in Crohn’s disease

Loch¹,

Kamphues²,

Beyer³

et al. 2023

Quant Imaging Med Surg

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Background: Conventional magnetic resonance enterography is limited in differentiating active inflammation and fibrosis in lesions of Crohn's disease (CD), thus providing a restricted basis for therapeutic decision making. Magnetic resonance elastography (MRE) is an emerging imaging tool that differentiates soft tissues on the basis of their viscoelastic properties. The aim of this study was to demonstrate the feasibility of MRE in assessing the viscoelastic properties of small bowel samples and quantifying differences in viscoelastic properties between healthy ileum and ileum affected by CD.Methods: Twelve patients (median age: 48 years) were prospectively enrolled in this study between September 2019 and January 2021. Patients of the study group (n=7) underwent surgery for terminal ileal CD, while patients of the control group (n=5) underwent segmental resection of healthy ileum. MRE of ileal tissue samples of surgical specimens from both groups was performed in a compact tabletop MRI scanner.Penetration rate (a in m/s) and shear wave speed (c in m/s) were determined as markers of viscosity and stiffness for vibration frequencies f of 1,000, 1,500, 2,000, 2,500, and 3,000 Hz. Additionally, damping ratio γ was deduced, and frequency-independent viscoelastic parameters were calculated using the viscoelastic spring-pot model.Results: Penetration rate a was significantly lower in CD-affected ileum compared to healthy ileum for all vibration frequencies (P<0.05). Consistently, damping ratio γ was higher in CD-affected ileum, averaged over all frequencies (healthy: 0.58±0.12, CD: 1.04±0.55, P=0.03), as well as at 1,000 and 1,500 Hz individually (P<0.05). Spring-pot-derived viscosity parameter η was also significantly reduced in CD-affected tissue (2.62±1.37 versus 10.60±12.60 Pa•s, P=0.02). No significant difference was found for shear wave speed c between healthy and diseased tissue at any frequency (P>0.05).^ ORCID: 0000-0003-1513-8339.Conclusions: MRE of surgical small bowel specimens is feasible, allowing determination of viscoelastic properties and reliable quantification of differences in viscoelastic properties between healthy and CDaffected ileum. Thus, the results presented here are an important prerequisite for future studies investigating comprehensive MRE mapping and exact histopathological correlation including characterization and quantification of inflammation and fibrosis in CD.

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“…Possible underlying mechanisms relate to effective-medium stiffness properties, which are altered by vascular softening ( Parker, 2014 ; Parker, 2015 ) or poroelastic effects such as increased coupling between blood pool and solid tissue ( Lilaj et al, 2021 ). Poroelastic effects in elastography are known to be more relevant in the lower frequency range ( McGarry et al, 2015 ), which might have contributed to the aforementioned discrepancies of results reported in the literature since transient elastography techniques exploit higher frequency bands than THE ( Morr et al, 2022 ). Of note, the baseline stiffness values we measured in our experiment (liver: 1.36 m/s, spleen: 1.63 m/s) are slightly lower than what has been reported in previous studies using THE (Tzschätzsch et.…”

Section: Discussionmentioning

confidence: 99%

Valsalva Maneuver Decreases Liver and Spleen Stiffness Measured by Time-Harmonic Ultrasound Elastography

Meyer

Tzschätzsch

Wellge

et al. 2022

Front. Bioeng. Biotechnol.

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Ultrasound elastography quantitatively measures tissue stiffness and is widely used in clinical practice to diagnose various diseases including liver fibrosis and portal hypertension. The stiffness of soft organs has been shown to be sensitive to blood flow and pressure-related diseases such as portal hypertension. Because of the intricate coupling between tissue stiffness of abdominal organs and perfusion-related factors such as vascular stiffness or blood volume, simple breathing maneuvers have altered the results of liver elastography, while other organs such as the spleen are understudied. Therefore, we investigated the effect of a standardized Valsalva maneuver on liver stiffness and, for the first time, on spleen stiffness using time-harmonic elastography (THE). THE acquires full-field-of-view stiffness maps based on shear wave speed (SWS), covers deep tissues, and is potentially sensitive to SWS changes induced by altered abdominal pressure in the hepatosplenic system. SWS of the liver and the spleen was measured in 17 healthy volunteers under baseline conditions and during the Valsalva maneuver. With the Valsalva maneuver, SWS in the liver decreased by 2.2% (from a median of 1.36 m/s to 1.32 m/s; p = 0.021), while SWS in the spleen decreased by 5.2% (from a median of 1.63 m/s to 1.51 m/s; p = 0.00059). Furthermore, we observed that the decrease was more pronounced the higher the baseline SWS values were. In conclusion, the results confirm our hypothesis that the Valsalva maneuver decreases liver and spleen stiffness, showing that THE is sensitive to perfusion pressure-related changes in tissue stiffness. With its extensive organ coverage and high penetration depth, THE may facilitate translation of pressure-sensitive ultrasound elastography into clinical routine.

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Liquid-Liver Phantom

Cited by 19 publications

References 46 publications

On the relationship between metabolic capacities and in vivo viscoelastic properties of the liver

On the relationship between metabolic capacities and in vivo viscoelastic properties of the liver

Ex vivo magnetic resonance elastography of the small bowel in Crohn’s disease

Valsalva Maneuver Decreases Liver and Spleen Stiffness Measured by Time-Harmonic Ultrasound Elastography

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