Characterization of frequency-dependent material properties of human liver and its pathologies using an impact hammer

Abstract

The current methods for characterization of frequency-dependent material properties of human liver are very limited. In fact, there is almost no data available in the literature showing the variation in dynamic elastic modulus of healthy or diseased human liver as a function of excitation frequency. We show that frequency-dependent dynamic material properties of a whole human liver can be easily and efficiently characterized by an impact hammer. The procedure only involves a light impact force applied to the tested liver by a hand-held hammer. The results of our experiments conducted with 15 human livers harvested from the patients having some form of liver disease show that the proposed approach can successfully differentiate the level of fibrosis in human liver. We found that the storage moduli of the livers having no fibrosis (F0) and that of the cirrhotic livers (F4) varied from 10 to 20 kPa and 20 to 50 kPa for the frequency range of 0-80 Hz, respectively.

Extracellular matrix particle–glycosaminoglycan composite hydrogels for regenerative medicine applications

“…We expect that high tissue particle concentrations increased the availability of free amine groups to facilitate faster gelation, but the inclusion of too many tissue particles appeared to compromise the final mechanical properties of the gel and resulted in lower maximum moduli. Liver matrix composite gels demonstrated a maximum storage modulus (247–22,323 Pa) that shifted 100‐fold within a range of tissue particle to CS–NHS ratios (3:1 and 1:3 tissue: CS–NHS wt/wt respectively), and spanned measured storage modulus values for native liver tissue reported in the literature (600–11,000 Pa) . The measured maximum storage modulus of fat (688 Pa), lung (1950 Pa), and spleen (596 Pa) composite gels were in the same order of magnitude of respective native soft tissues storage modulus values reported in the literature (fat [200–900 Pa], lung [5500 Pa], spleen [200–2000 Pa]) and fell within ranges of storage modulus values of other formulations of ECM and GAG based hydrogels (11–50,000 Pa) .…”

Liver stiffness assessment with tagged MRI of cardiac-induced liver motion in cirrhosis patients

“…Our method also works in a different effective frequency range. According to Ozcan et al , the storage and loss moduli of human livers increase with an increase in excitation frequency. Thus, this method may provide additional new information on the properties of the liver by using much lower frequency of ∼1 Hz, compared other more conventional imaging approaches, using frequencies of ∼50 Hz for US elastography and of ∼65 Hz for MRE.…”

Quantifying tissue mechanical properties using photoplethysmography

“…This value is higher for vessels, for example the portal vein YM was reported by Wang et al to be 32.04 +/− 5.65 KPa for a pressure of 75 mmHg [45]. Tissue compliance has been reported to decrease 3 to 10 times with the development of fibrosis [40,44,49] which results in a similar increase in its YM. For our in vitro studies, phantoms were developed with YM of 11.7, 15 and 61 KPa and the analysis of the PPG rise time showed a significant decrease with the increase of the YM.…”

“…The mechanical properties of tissue can be significant for a number of medical applications. In particular for our work, mechanical properties are of great importance to the success of transplant surgeries [43] and are indicators of hepatic health [44][45][46]. In this paper, we showed the ability of using the waveform of the PPG signal to monitor changes in compliance and diagnose vascular complications that are the second most common cause of graft failure after primary graft non function [47,48].…”