Shearwave dispersion ultrasound vibrometry (sduv) on swine kidney

Abstract

Shearwave Dispersion Ultrasound Vibrometry (SDUV) is used to quantify both tissue shear elasticity and shear viscosity by evaluating dispersion of shear wave propagation speed over a certain bandwidth (50–500 Hz). The motivation for developing elasticity imaging techniques is based on the possibility of diagnosing disease process. However, it is important to study the mechanical properties of healthy tissues; such data can enhance clinical knowledge and improve understanding of the mechanical properties of tissue. The purpose of this study is to evaluate the feasibility of SDUV for in vitro measurements of renal cortex shear elasticity and shear viscosity on healthy swine kidney. A total of eight excised kidneys from female pigs were used in these in vitro experiments, and a battery of different tests were performed to gain insight on the material properties of the renal cortex. From these eight kidneys, the overall renal cortex elasticity and viscosity was 1.81 ± 0.17 kPa and 1.48 ± 0.49 Pa·s, respectively. In an analysis of the material properties over time after excision, there was not a statistically significant difference in shear elasticity over a 24 hour period, but a statistically significant difference in shear viscosity was found. Homogeneity of the renal cortex was examined and it was found that shear elasticity and shear viscosity were statistically different within a kidney, suggesting global tissue inhomogeneity. More than 30% increases in shear elasticity and shear viscosity were observed after immersion in 10% formaldehyde. Lastly, it was found that the renal cortex is rather anisotropic. Two values for shear elasticity and shear viscosity were measured depending on shear wave propagation direction. These various tests elucidated different aspects of the material properties and the structure of the ex vivo renal cortex.

A two-criterion model for microvascular bioeffects induced in vivo by contrast microbubbles exposed to medical ultrasound

“…These include: experimental results for the frequency-dependence of the threshold for capillary hemorrhage in the kidneys of rats infused with Definity™ obtained by Miller et al (2008b), measurements of the size distribution of Definity™ microbubbles immediately prior to dosing reported by Goertz et al (2007), the probability that a bubble of a given size will cross the capillary bed of the mammalian lung derived from data on the sizes of lung capillaries given by Hogg (1987), the model for the dynamics of spherical gas bubbles in soft tissue developed by Yang and Church (2005), the finding that assuming a bubble pulsating within a blood vessel remains spherical provides both a tractable problem and reasonable agreement with observations as discussed in Chen et al (2011), and the method for estimating the threshold for inertial cavitation in vivo described by . The more significant portions of these are described in the Background and Methods, with some of the text below having been taken rather liberally from the original articles.…”

“…The values of the density (ρ), interfacial tension (σ), rigidity (G) and viscosity (µ) for blood were 1050 kg m −3 , 0.056 N m −1 , 0.0 kPa and either 3 or 5 mPa·s, respectively, while those for kidney tissue were 1100 kg m −3 , 0.056 N m −1 , either 0 kPa, 1 kPa, 2 kPa or 0.18 MPa and 3 -23 mPa·s, respectively. These values encompass bulk-tissue values for rigidity reported for kidney from ultrasound elastography methods for frequencies below 1 kHz (Arda et al 2011;Amador et al 2011;Derieppe et al 2012;Gennisson et al 2012;Grenier et al 2013;Moon et al 2015) and a direct shear-wave method for frequencies above 6 MHz . It is worth noting here that in all cases for which sufficient data are available for comparison over several orders of magnitude for frequency, the values for the modulus of rigidity in tissue tend to remain the same, while values for viscosity decrease by a factor of 100 (see also Madsen et al 1983;Deffieux et al 2009;Chen et al 2013).…”

“…While the changes in the radii of curvature (radial and axial) are rather small during bubble expansion, they can be much larger during the collapse phase. The small radius of curvature that obtains during the invagination of the vessel wall, shown in some detail in the photomicrographs and movies acquired by Chen et al (2011), tends to maximize the stress and strain within the wall Hosseinkhah et al 2013), potentially leading directly to its failure. The role of liquid jetting is less clear.…”

“…This bioeffect is readily observable, of clear biological significance and serves as the threshold of concern for patient risk. While the modeling of specific mechanisms of capillary injury, such as capillary stretching (Qin and Ferrara, 2006;Miao et al 2008), vessel invagination (Hosseinkhah et al 2013), jet impingement (Chen et al 2011), and fluid stress (Hosseinkhah et al 2015), and possibly others, is an ultimate goal, such modeling likely would require extensive detailed theoretical analysis by three-dimensional finite-amplitude methods for any full accounting of the complex microbubble-capillary problem. Here, we pursue the general approach of the MI which was based primarily on theoretical microbubble behavior in an effort to obtain general insights into the problem.…”

A finite element model to study the effect of tissue anisotropy onex vivoarterial shear wave elastography measurements

“…The potential of SWE to detect tissue anisotropy was previously shown for in-vitro tissue phantoms (Chatelin et al, 2014;Aristizabal et al, 2014) for skeletal and cardiac muscle (Gennisson et al, 2010;Urban et al, 2016;Rudenko & Sarvazyan, 2006;Pernot et al, 2007) and kidneys (Amador et al, 2011). However, most of the studies in literature have mainly focused on bulky transverse isotropic materials with only one family of fibres (Rudenko & Sarvazyan, 2006;Gennisson et al, 2010;Royer et al, 2011;Rudenko & Sarvazyan, 2014;Chatelin et al, 2015;Urban et al, 2016;Guo et al, 2015;Chatelin et al, 2014).…”