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Patients with a 70–99% stenosed carotid artery will undergo surgery to prevent rupture of the plaque. However, the degree of stenosis does not determine the vulnerability of the plaque, since vulnerability depends on the plaque's morphology, mechanical properties and the force acting on the plaque. Mechanical models of the carotid artery can improve decision-making of the surgeon by quantifying and...
Aluminium scandium nitride (ASN) exhibits a largely enhanced piezoelectric response as compared to aluminium nitride (AlN), which makes it an upcoming piezoelectric material for next generation RF filters, sensors, actuators and energy harvesting devices. In this work, process-microstructure-property relationships of such ASN films containing up to 40 at% Sc were investigated. Hereby, the influence...
Novel methods for determining rupture risk in abdominal aortic aneurysms (AAAs) have focused primarily on CT-based wall stress analysis using finite element models (FEMs). Recent studies have demonstrated ultrasound (US) based FEM, and the possibility of using inverse FEM analysis: matching displacements between the models and US to find patient specific aortic stiffness. This requires an accurate...
Burst wave lithotripsy (BWL) is an experimental method to noninvasively fragment urinary calculi using low-frequency focused bursts of ultrasound. To optimize many of the acoustic parameters for this technology, it is necessary to understand the physical interactions between ultrasound bursts and stones. In this study, the interaction of elastic waves with model stones was simulated and experimentally...
The number of transmit and receive channels needed to perform real-time 3-D ultrasonic imaging can be greatly reduced if row-column (RC) addressed 2-D transducer arrays are used. However, fabricating RC CMUTs have shown to be challenging. The difficulties are typically stress issues related to the high temperature processes and charging effects related to mobile charges in dielectric thin films, overall...
Abdominal aortic aneurysms are lethal in 80% of all cases when ruptured. Current guidelines for AAA repair are mainly based on the diameter, which has its shortcomings. Hence, a more patient-specific rupture risk assessment is needed. In this study, methods for elastography and wall stress analysis using 4D ultrasound (US) were developed. Patient-specific material properties and peak wall stresses...
P92 martensitic ferritic steels are an attractive material for critical components in power industries due to the excellent creep property. However, these steels are usually susceptible to creep strength degradation during a long service period under the elevated temperature and pressure. Creep damage evaluation is of concern to quantitatively assess the remaining lifespan of the critical components...
In shear wave elastography (SWE), acoustic radiation forces (ARF) are employed to generate shear waves within the tissue. Although the transmitted pulses are longer than those in conventional clinical ultrasound, they typically obey the mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as ARF-induced stresses and strain rates could potentially...
End-stage renal disease (ESRD) is an irreversible deterioration in the renal function in which the body loses its ability to maintain the fluid and metabolic balance. Transplantation is the treatment of choice for patients with ESRD. After transplantation, biopsies are performed to monitor the function of the kidney transplant over time. Due to the invasive nature of biopsies, we are investigating...
Third overtone and higher overtone thickness shear quartz resonators are used as a frequency source in ultra-stable oscillators. The governing equations for the force-frequency effect and the related acceleration sensitivity of these resonators are well established. The force exerted on the resonator causes initial stress and strain that in turn changes the resonator frequency. However, we have found...
Articular cartilage is composed of cartilage cells and extracellular matrix (mainly collagen type II and proteoglycan). When stress is applied, the cartilage releases water and the stress is distributed [1]. The extra-cellular matrix structure is important to perform normal cartilaginous functions. It is then important to evaluate the elasticity and anisotropy of the cartilage, in addition to the...
Shearography is an optical non-destructive testing technique which has been used as a practical tool in industrial applications due to its suitability for large area and fast inspections. Shearography is based on the differential of two interferometric patterns obtained when the test samples are under stress loading and when the stress loading is removed. Conventional loading methods for shearography...
Growth control is an important technique in plant markets, for appropriate shipping time of plants (e.g., flowers and fruits) allows for reducing production costs for post harvesting storage and pesticide. It is favorable to control plant growth without any chemicals; physical stresses are attractive candidates for this purpose. Here, we propose an ultrasound-based technique to control plant growth.
Nonlinear Lamb wave has been widely acknowledged as an efficient nondestructive method for evaluating early stage of fatigue damage. The previous studies focused on the evaluation of fatigue damage using the particular mode pairs, such as S1-S2 mode pair. Recently, the nonlinear S0 Lamb mode with low-frequency was considered for its unique features of less dispersion and easy to be generated, and...
Early detection of pathological structures is crucial for the prognosis and treatment of patients. Biomechanical characterization of nonlinear tissue behavior has been shown to significantly improve tumor differentiation compared to linear elastic modulus alone. We aim to characterize the third (A) and fourth (D) order elastic constants.
Blood-Brain Barrier opening (BBBO) with Focus Ultrasound (FUS) seems to give significant results in clearing amyloid plaques and restoring memory in Alzheimer's disease (AD-Tg) transgenic mice models. So far, only few teams have produced results [Burgess, 2014 — Leinenga, 2015] which motivates more investigations. To do so we set up two protocols: one on wild type (WT) mice and one AD-Tg mice.
We explore the frequency dependence of piezoceramic disc transducers bonded to plates. For some transducer dimensions, the frequency response shows a sharp peak. This behavior is inconsistent with the use of short pulses or broadband chirps for flaw localization. We use finite element simulation to show that the highly resonant behavior is caused by a high-strain region immediately beneath the transducer...
Early detection of pathological processes is crucial for the prognosis and treatment of patients, which can be facilitated through studying tissue biomechanical properties. Shear wave elastography is a technique to estimate the shear modulus of tissue. Such measurements quantify elasticity linearized around an immediate state of local stress condition, under applied nature of excitation. Stress-strain...
Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency...
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