Lamb wave dispersion ultrasound vibrometry (LDUV) method for quantifying mechanical properties of viscoelastic solids (original) (raw)
Related papers
Transcutaneous Viscoelasticity Estimation of Heart Wall Using Ultrasound
Future Medical Engineering Based on Bionanotechnology, 2006
This paper describes a novel method to noninvasively measure the myocardial viscoelasticity in vivo to evaluate the heart diastolic properties. By the ultrasonic measurement of the myocardial motion, we have already found that some pulsive waves are spontaneously excited by aortic-valve closure (AVC) at end-systole (T 0). In this study, a sparse sector scan at a sufficiently high frame rate clearly reveals wave propagation along the heart wall. The propagation time of the wave along the heart wall is very small, namely, several milliseconds, and cannot be measured by conventional equipment. From the measured phase velocity, we estimate the myocardial viscoelasticity in vivo. In in vivo experiments applied to 6 healthy subjects, the propagation of the pulsive wave was clearly visible in all subjects. For the frequency component up to 90 Hz, the typical propagation speed is about several m/s and rapidly decreased around the time of AVC. For the healthy subject, the typical value of elasticity was about 24-30 kPa and did not change around the time of AVC. The typical transient values of viscosity decreased rapidly from 400 Pa⋅s to 70 Pa⋅s around the time of AVC. The measured shear elasticity and viscosity in this study are comparable to those obtained for the human tissues using audio frequency in in vitro experiments reported in the literature. This method offers potential for in vivo imaging of the spatial distribution of the passive mechanical properties of the myocardium, which cannot be obtained by conventional echocardiography, CT, or MRI.
Biomedical physics & engineering express, 2018
Diastolic dysfunction causes close to half of congestive heart failures and is associated with increased stiffness in left-ventricular myocardium. A clinical tool capable of measuring viscoelasticity of the myocardium could be beneficial in clinical settings. We used Lamb wave Dispersion Ultrasound Vibrometry (LDUV) for assessing the feasibility of making non-invasive measurements of myocardial elasticity and viscosity in pigs. open-chest measurements of myocardial elasticity and viscosity obtained using a Fourier space based analysis of Lamb wave dispersion are reported. The approach was used to perform ECG-gated transthoracic measurements of group velocity, elasticity and viscosity throughout a single heart cycle. Group velocity, elasticity and viscosity in the frequency range 50-500 Hz increased from diastole to systole, consistent with contraction and relaxation of the myocardium. Systolic group velocity, elasticity and viscosity were 5.0 m/s, 19.1 kPa, 6.8 Pa·s, respectively. I...
Noninvasive measurement of myocardial viscoelasticity
2005
This presentation proposes a novel method to noninvasively measure the myocardial viscoelasticity in vivo to evaluate the heart diastolic properties. By the ultrasonic measurement of the myocardial motion, we have already found that some pulsive waves are spontaneously excited by aortic-valve closure (AVC) at end-systole (T 0). In this study, a sparse sector scan at a sufficiently high frame rate clearly reveals wave propagation along the heart wall. The propagation time of the wave along the heart wall is very small, namely, several milliseconds, and cannot be measured by conventional equipment. From the measured phase velocity, we estimate the myocardial viscoelasticity in vivo. In in vivo experiments applied to 6 healthy subjects, the propagation of the pulsive wave was clearly visible in all subjects. For the frequency component up to 90 Hz, the typical propagation speed is about several m/s and rapidly decreased around the time of AVC. For the healthy subject, the typical value of elasticity was about 24-30 kPa and did not change around the time of AVC. The typical transient values of viscosity decreased rapidly from 400 Pa•s to 70 Pa•s around the time of AVC. The measured shear elasticity and viscosity in this study are comparable to those obtained for the human tissues using audio frequency in in vitro experiments reported in the literature. This method offers potential for in vivo imaging of the spatial distribution of the passive mechanical properties of the myocardium.
Noninvasive Viscoelasticity Estimation of Heart Wall Using Ultrasound
This presentation proposes a novel method to noninvasively measure the myocardial viscoelasticity in vivo to evaluate the heart diastolic properties. By the ultrasonic measurement of the myocardial motion, we have already found that some pulsive waves are spontaneously excited by aorticvalve closure (AVC) at end-systole (T 0). In this study, a sparse sector scan at a sufficiently high frame rate clearly reveals wave propagation along the heart wall. The propagation time of the wave along the heart wall is very small, namely, several milliseconds, and cannot be measured by conventional equipment. From the measured phase velocity, we estimate the myocardial viscoelasticity in vivo. In in vivo experiments applied to 6 healthy subjects, the propagation of the pulsive wave was clearly visible in all subjects. For the frequency component up to 90 Hz, the typical propagation speed is about several m/s and rapidly decreased around the time of AVC. For the healthy subject, the typical value of elasticity was about 24-30 kPa and did not change around the time of AVC. The typical transient values of viscosity decreased rapidly from 400 Pa•s to 70 Pa•s around the time of AVC. The measured shear elasticity and viscosity in this study are comparable to those obtained for the human tissues using audio frequency in in vitro experiments reported in the literature. This method offers potential for in vivo imaging of the spatial distribution of the passive mechanical properties of the myocardium, which cannot be obtained by conventional echocardiography, CT, or MRI
Viscoelasticity measurement of heart wall in in vivo
IEEE Ultrasonics Symposium, 2004, 2004
By measuring spatial distribution of the minute vibrations in the heart wall from the chest wall using ultrasound, we find that some impulses propagate along the heart wall in healthy human subjects just after closure of the aortic valve for the first time. Their amplitude is found to be on the order of several tens of micrometers, and up to 100 Hz. Their propagation speed shows frequency dispersion, which agrees with the theoretical characteristics of the Lamb wave. The instantaneous viscoelasticity of the wall is then noninvasively determined. These findings have a novel potential for myocardial tissue characterization in clinical diagnosis.
In vivo viscoelasticity estimation of myocardium
IEEE Ultrasonics Symposium, 2005.
Though myocardial viscoelasticity is essential in the evaluation of heart diastolic properties, it has never been noninvasively measured in vivo. By the ultrasonic measurement of the myocardial motion, we have already found that some pulsive waves are spontaneously excited by aortic-valve closure (AVC) at end-systole (T0). In this study, a sparse sector scan at a sufficiently high frame rate clearly reveals wave propagation along the heart wall. The propagation time of the wave along the heart wall is very small, namely, several milliseconds, and cannot be measured by conventional equipment. From the measured phase velocity, we estimate the myocardial viscoelasticity in vivo. In in vivo experiments applied to 6 healthy subjects, 3 patients with hypertrophic cardiomyopathy (HCM), and 3 patients with aortic stenosis (AS), the propagation of the pulsive wave was clearly visible in all subjects. For the frequency component up to 90 Hz, the typical propagation speed is about several m/s and rapidly decreased around the time of AVC. For the healthy subject, the typical value of elasticity was about 24-30 kPa and did not change around the time of AVC. The typical transient values of viscosity decreased rapidly from 400 Pa•s to 70 Pa•s around the time of AVC. The measured shear elasticity and viscosity in this study are comparable to those obtained for the human tissues using audio frequency in in vitro experiments reported in the literature. The method cannot be easily applied to these patients because there were inhomogeneities in the phase velocities due to the diseased myocardium. By applying the measurement of the phase velocity to each of 5 layers set in the heart wall, the phase velocity in the middle layer was lower than those in the LV-and RV-sides of the heart wall, which will corresponds to the change in myocardial fiber orientations. This method offers potential for in vivo imaging of the spatial distribution of the passive mechanical properties of the myocardium, which cannot be obtained by conventional echocardiography, CT, or MRI.
Japanese Journal of Applied Physics
It is important to evaluate the viscoelasticity of muscle for assessment of its condition. However, quantitative and noninvasive diagnostic methods have not yet been established. In our previous study, we developed a method, which used ultrasonic acoustic radiation forces irradiated from two opposite horizontal directions, for measurement of the viscoelasticity. Using two continuous wave ultrasounds, an object can be actuated with an ultrasonic intensity, which is far lower (0.9 W/cm 2) than that in the case of the conventional acoustic radiation force impulse (ARFI) method. In the present study, in vitro experiments using phantoms made of polyurethane rubber and porcine muscle tissue embedded in a gelatin block were conducted. We actuated phantoms by ultrasonic radiation force and measured the propagation velocity of the generated shear wave inside the phantoms using a diagnostic ultrasound system. The viscoelasticities of phantoms were estimated by fitting a viscoelastic model, i.e., the Voigt model, to the frequency characteristic of the measured shear wave propagation speed. In the mechanical tensile test, a softer polyurethane phantom exhibited a lower elasticity and a higher viscosity than a polyurethane phantom with a higher elasticity and a lower viscosity. The viscoelasticity measured by ultrasound showed the same tendency as that in the tensile test. Furthermore, the viscoelasticity of the phantom with porcine muscular tissue was measured in vitro, and the estimated viscoelasticity agreed well with that reported in the literature. These results show the possibility of the proposed method for noninvasive and quantitative assessment of the viscoelasticity of biological soft tissue.
Viscoelastic property measurement in thin tissue constructs using ultrasound
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2008
We present a dual-element concave ultrasound transducer system for generating and tracking of localized tissue displacements in thin tissue constructs on rigid substrates. The system is comprised of a highly focused PZT-4 5-MHz acoustic radiation force (ARF) transducer and a confocal 25-MHz polyvinylidene fluoride imaging transducer. This allows for the generation of measurable displacements in tissue samples on rigid substrates with thickness values down to 500 µm. Impulse-like and longer duration sine-modulated ARF pulses are possible with intermittent M-mode data acquisition for displacement tracking. The operations of the ARF and imaging transducers are strictly synchronized using an integrated system for arbitrary waveform generation and data capture with a shared timebase. This allows for virtually jitter-free pulse-echo data well suited for correlation-based speckle tracking. With this technique we could faithfully capture the entire dynamics of the tissue axial deformation at pulse-repetition frequency values up to 10 kHz. Spatio-temporal maps of tissue displacements in response to a variety of modulated ARF beams were produced in tissue-mimicking elastography phantoms on rigid substrates. The frequency response was measured for phantoms with different modulus and thickness values. The frequency response exhibited resonant behavior with the resonance frequency being inversely proportional to the sample thickness. This resonant behavior can be used in obtaining high-contrast imaging using magnitude and phase response to sinusoidally modulated ARF beams. Furthermore, a second order forced harmonic oscillator (FHO) model was shown to capture this resonant behavior. Based on the FHO model, we used the extended Kalman filter (EKF) for tracking the apparent modulus and viscosity of samples subjected to dc and sinusoidally modulated ARF. The results show that the stiffness (apparent modulus) term in the FHO is largely time-invariant and can be estimated robustly using the EKF. On the other hand, the damping (apparent viscosity) is time varying. These findings were confirmed by comparing the magnitude response of the FHO (with parameters obtained using the EKF) with the measured ones for different thin tissue constructs.
Annals of Biomedical Engineering, 2000
Experiments were performed to test the hypothesis that viscoelastic properties of the swine myocardium are independent of heart rate (HR), preload (PL), and afterload (AL). Left ventricular pressure and aortic flow (AoF) waveforms were recorded in 13 swine. At different paced heart rates, an inferior vena caval occlusion (IVC) was used to reduce PL, then the IVC was released and simultaneously the aorta was clamped to increase AL. Equivalent left ventricular pressure waveform pairs consisting of an ejecting waveform (denoted as LVP) and isovolumic waveform (denoted as hydromotive pressure, HMP) were selected according to specified criteria resulting in 371 equivalent waveform pairs. From the selected waveform pairs and corresponding aortic flow waveforms, the viscoelastic properties (k and ε 1) were estimated by HMP = LVP + ε 1 V EJ + k × LVP × AoF. Here ε 1 is the parallel elastance, k is the myocardial friction, and V EJ is the integral of AoF over ejection. Next, using k, ε 1 , LVP, and AoF waveforms, HMP was estimated using the equation above. To validate the model, the measured HMP and model-calculated HMP were compared for 371 matched waveform pairs (R 2 = 0.97, SEE = 3.7 mmHg). The viscoelastic parameters (k and ε 1) did not exhibit any clear or predictable dependence on HR, PL, and AL.
Ultrasound in Medicine & Biology, 2007
Biomechanical properties of soft tissues are important for a wide range of medical applications, such as surgical simulation and planning and detection of lesions by elasticity imaging modalities. Currently, the data in the literature is limited and conflicting. Furthermore, to assess the biomechanical properties of living tissue in vivo, reliable imaging-based estimators must be developed and verified. For these reasons we developed and compared two independent quantitative methods -crawling wave estimator (CRE) and mechanical measurement (MM) for soft tissue characterization. The CRE method images shear wave interference patterns from which the shear wave velocity can be determined and hence the Young's modulus can be obtained. The MM method provides the complex Young's modulus of the soft tissue from which both elastic and viscous behavior can be extracted. This article presents the systematic comparison between these two techniques on the measurement of gelatin phantom, veal liver, thermal-treated veal liver, and human prostate. It was observed that the Young's moduli of liver and prostate tissues slightly increase with frequency. The experimental results of the two methods are highly congruent, suggesting CRE and MM methods can be reliably used to investigate viscoelastic properties of other soft tissues, with CRE having the advantages of operating in nearly real time and in situ.