The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Cardiovascular disease, including atherosclerosis and critical limb ischemia, affects millions of people worldwide. There is a clinical need to base treatment decisions on quantitative analysis of the plaque composition. However, no reliable clinical methods to quantify the mechanical properties of plaque components and detect plaque vulnerability currently exist, particularly for coronary disease...
Elastic properties of the ocular tissues are significantly affected by intraocular pressure (IOP) in the eye. For example, the speed of the elastic wave in the cornea dramatically increases with IOP. In our previous studies using ultrasound shear wave imaging we demonstrated that, for the lens, the increase in IOP does not result significant changes in the wave velocity. Compared with ultrasound imaging,...
Piezoelectric ultrasonic motors (PUMs) are based on the concept of driving the runner by a mechanical vibration excited on the stator via the converse piezoelectric effect. They exhibit merits of small size, simple structure, quick response, high accuracy and resolution, self-locking when power off and a lack of electromagnetic radiation. The linear PUMs become the research focus in recent years as...
Displacement estimation is a critical component of elastography. The measurement of sub-resolution displacements relies on high cross-correlation (CC) between repeated collinear RF acquisitions. CCs are degraded by common sources of acoustic noise, such as reverberation clutter, in addition to the displacement of scatterers within the radiation force field. CCs are also degraded spatially across the...
Blood clotting, a process to avoid bleeding, involves vasoconstriction, platelet plug build-up, coagulation, clot retraction and fibrinolysis. During coagulation, blood changes from liquid to gel, and the clot viscoelastic properties continue modifying until fibrinolysis. Tests to analyze bleeding disorders and anticoagulant therapy include clot-based assays, to detect the end-point of fibrin network...
To elicit bio-effects, ultrasound (US) stimulated microbubbles (MBs) must be in proximity to their target and this is not always the case (e.g. sonothrombolysis). Radiation forces can direct MBs to clots and our previous work suggested clot degradation patterns (Fig A) could be influenced by ‘transport pulses’. However, this is a complex process involving a population of MBs, with size-dependent radiation...
The acoustic microstreaming originating from microbubbles' linear oscillations can be used as a potential cell sonoporation tool for drug delivery and gene transfection. However, this bubble-based method suffers from bubble instability, non-uniform size, unreliable performance, and inconvenient trapping. In order to overcome the above drawbacks, in this study, we proposed a massive drug delivery method...
The concept of the band structure is central to the field of phononic crystals. Indeed, capturing the dispersion of Bloch waves — the eigenmodes of propagation in periodic media — gives invaluable information on allowed propagation modes, their phase and group velocities, local resonances, and band gaps. Band structures are usually obtained by solving an eigenvalue problem defined on a closed and...
Myocardial elastance, derived from pressure-volume (PV) loops in the left ventricle (LV), can be used to assess LV function and myocardial performance. This method requires an invasive intracardiac pressure-volume catheter to be inserted in the LV, limiting the method's utility in clinical screening and monitoring. Strain echocardiography and cardiac acoustic radiation force impulse (ARFI) imaging...
Nanoparticle manipulation has a variety of potential applications, from two-dimensional material fabrication to biomedical engineering. Pattern and transportation of nanoparticles has been receiving increasing attention in recent years. Ultrasound as a mechanical wave has proven to be the most effective in the manipulation of micro-objects in a non-contact and non-invasive fashion. However, due to...
A real-time ultrasound (US) coagulation monitoring for coagulation based on acoustic radiation force is described. US imaging to facilitate HIFU has advantages with respect to portability, cost effectiveness and spatiotemporal resolution. Localized motion imaging (LMI) is one of the techniques based on US to detect a change of tissue mechanical properties caused by its thermal coagulation. To achieve...
Cellular functions, for example proliferation, migration or gene expression, usually accompany a relationship with their mechanical properties. Three main methods, including atomic force microscopy (AFM), optical tweezer and magnetic tweezers, have been developed to measure cell's mechanics. However, AFM needs to contact cell resulting in prominent physical changes in elasticity and a pericellular...
It was shown experimentally in [1], [2] that a macroscopic cylindrical solid can be rotated due to the excitation of two counter-propagating surface acoustic waves (SAWs) with different amplitudes on its surface. Arising internal distributed rotation force has been calculated phenomenologically in the partial case of a piezoelectric tube with a ring unidirectional electrode transducer (RUDT) using...
Acoustic droplet vaporization (ADV) is a process when a droplet is converted into a gaseous bubble under ultrasound (US) stimulation. Our previous study has shown that the mechanical force generated by ADV can release drugs and disrupt vessels. It would result in the streaming intact droplets leaking into tissue. In addition, the intact droplets may occur ADV process by subsequent US stimulation....
Elasticity values reported by shear wave elastography techniques for Breast tissue/mass are a combination of elasticity and viscosity at the frequency with peak shear wave energy; thus, resulting in overestimation of tissue elasticity. To better estimate shear elasticity and to understand the role of shear viscosity in suspicious breast masses at different frequencies, the frequency dispersion of...
Contact manipulation using a micropipette is widely used for cell culture and evaluation. However, the operation efficiency and the damage on the cells depend on the individual skills. A technique for manipulating a micro biological material with high accuracy and selectivity is required. Our group has been investigating noncontact ultrasonic manipulation techniques using acoustic standing wave. In...
Microbubbles (MBs) are widely used in clinical site as contrast agents in ultrasound imaging due to its eminent responsiveness to several MHz band. In recent years, ultrasound drug delivery system (DDS) using MBs are widely researched to achieve selective medication to the targeted diseased part. In the condition of high number density of bubbles to enhance the performance of DDS, it is essentially...
Imaging technologies that allow assessment of the elastic properties of soft tissue provide clinicians with an important asset for several diagnostic applications. A quantitative measure of stiffness can be obtained by shear-wave (SW) elasticity imaging, a method that uses acoustic radiation force to produce laterally-propagating shear waves that can be tracked to obtain the velocity, which in turn...
Phononic crystals have attracted intensive research interest for decades since the early 1990s. They exhibit a spatially periodic feature regarding the distribution of physical properties, geometry, boundary conditions, or/and external stimuli, making their wave spectrum quite different from the conventional continuous one, usually with frequency band gaps where waves cannot propagate through them...
The 30MHz lithium niobate (LiNbO3) ultrasound transducer with a highly focused beam was used to generate gradient force which can pull a single leukemia cell to toward a focus to be a trapping situation. The transducer was sterilized by using 70% ethanol before the experiment. Five leukemia cells before treatment and five cells after treatment by a chemotherapy drug were trapped and measured their...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.