The growing clinical use of MR elastography requires the development new quantitative standards for measuring tissue stiffness. Here, we examine a soft mimicking phantom material (Ecoflex) over wide frequency range (200 Hz to 7.75 kHz). recorded data are fit cohort viscoelastic models varying complexity (integer and fractional order). This was accomplished using multiple sample sizes by employing geometric focusing shear wave front compensate changes in wavelength attenuation this broad...

Magnetic resonance elastography (MRE) was extended to the microscopic scale image low-frequency acoustic shear waves (typically less than 1 kHz) in soft gels and biological tissues with high spatial resolution (34 micromx34 micromx500 microm). Microscopic MRE (microMRE) applied agarose gel phantoms, frog oocytes, tissue-engineered adipogenic osteogenic constructs. Analysis of low-amplitude wave pattern samples allowed material stiffness viscous loss properties (complex stiffness) be...

Knowledge of mechanical properties tissue-engineered cartilage is essential for the optimization tissue engineering strategies. Microscopic magnetic resonance elastography (μMRE) a recently developed MR-based technique that can nondestructively visualize shear wave motion. From observed pattern in MR phase images (e.g., modulus or stiffness) be extracted. For quantification dynamic small and stiff cartilage, μMRE needs to performed at frequencies kilohertz range. However, greater than 1 kHz...

The most common method to design tuned dynamic vibration absorbers is still that of Den Hartog, based on the principle invariant points. However, this optimal only when attaching absorber a single-degree-of-freedom undamped main system. In present paper, an extension classical Hartog approach multi-degree-of-freedom system presented. Sherman-Morrison matrix inversion theorem used obtain expression leads points for Using expression, analytical solution damper value derived. Also, effect...

We present experimental and computational results that describe the level, distribution, importance of velocity fluctuations within venous anastomosis an arteriovenous graft. The motivation this work is to understand better biomechanical forces in development intimal hyperplasia these grafts. Steady-flow vitro studies (Re=1060 1820) were conducted a graft model represents measure by means laser Doppler anemometry. Numerical simulations with same geometry flow conditions employing spectral...

Full explanation for the pathogenesis of syringomyelia (SM), a neuropathology characterized by formation cystic cavity (syrinx) in spinal cord (SC), has not yet been provided. It hypothesized that abnormal cerebrospinal fluid (CSF) pressure, caused subarachnoid space (SAS) flow blockage (stenosis), is an underlying cause syrinx and subsequent pain patient. However, paucity detailed vivo pressure data made theoretical explanations difficult to reconcile. In order understand complex...

In this paper, a new model of the harmonic drive transmission is presented. The purpose work to better understand hysteresis behavior while constructing type comprehensive model. four dominant aspects behavior—nonlinear viscous friction, nonlinear stiffness, hysteresis, and kinematic error—are all included in taken be black box, dynamometer used observe input/output relations transmission. This phenomenological approach does not require any specific knowledge internal kinematics. novel...

SampLe Interval Modulation-magnetic resonance elastography (SLIM-MRE) is introduced for simultaneously encoding all three displacement projections of a monofrequency vibration into the MR signal phase. In SLIM-MRE, individual components are observed using different sample intervals. doing so, modulated with apparent frequencies in phase expressed as harmonic function start time motion gradients and can thus be decomposed by applying Fourier transform to sampled multidirectional phases. this...

A novel technique for measuring in vivo human skin viscoelastic properties using optical elastography has been developed. The uses geometrically focused surface (GFS) waves that allow wide bandwidth measurements of the wave field. An analytical solution case a radiating annular disk source was fit to experimentally measured GFS waves, enabling an estimate frequency-dependent wavenumber, which can then be related dynamic shear modulus. Several models were modulus dispersion curve....

Noninvasive measurement of mechanical wave motion (sound and vibration) in the lungs may be diagnostic value, as it can provide information about properties lungs, which turn are affected by disease injury. In this study, two previously derived theoretical models vibroacoustic behavior lung parenchyma compared: (1) a Biot theory poroviscoelasticity (2) an effective medium for compression (also known "bubble swarm" model). A fractional derivative formulation shear viscoelasticity is...

The cornea is a highly specialized organ that relies on its mechanical stiffness to maintain aspheric geometry and refractive power, corneal diseases such as keratoconus have been linked abnormal tissue biomechanics. Dynamic optical coherence elastography (OCE) clinically promising non-contact non-destructive imaging technique can provide measurements of directly in vivo. method the concepts where shear waves are generated imaged within obtain properties stiffness. accuracy OCE-based...

An analytical solution is developed for the problem of surface wave generation on a linear viscoelastic half-space by finite rigid circular disk located and oscillating normal to it. The an incremental advancement theoretical work reported in articles focused seismology. Since application interest here medical diagnostics, verified experimentally using phantom with material properties comparable biological soft tissue. Findings suggest that prior estimates literature shear viscosity human...

Noninvasive measurement of the speed with which cerebrospinal fluid (CSF) velocity wave travels through spinal canal is interest as a potential indicator CSF system pressure and compliance, both may play role in development craniospinal diseases. However, (VWS) has eluded researchers primarily due to either lack access measurements or poor temporal resolution. Here, we present VWS methodology using novel MR sequence that acquires unsteady during cardiac cycle time interval <10 ms. Axial were...

Previous studies of the first author and others have focused on low audible frequency (&amp;lt;1 kHz) shear surface wave motion in a viscoelastic material comprised or representative soft biological tissue. A specific case considered has been (Rayleigh) caused by circular disk located oscillating normal to it. Different approaches identifying type coefficients model based these measurements proposed. One approach optimize an assumed match frequency-dependent Rayleigh speed. Another...

Previous studies have shown that therapeutic pulsed ultrasound (pulsed) has superior stimulatory effect on bone fracture healing compared with continuous (continuous). Our predictive hypothesis was can produce better formation during mandibular osteodistraction than ultrasound. Thirty-six New Zealand rabbits were divided into 3 groups of 12. Osteodistraction performed at mm/day for 5 days. Group 1 received pulsed, group 2 ultrasound, and the control (distraction only). Bone assessed by...