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As new flow imaging methods are actively being developed, there is a growing need to devise appropriate phantoms that can holistically assess the accuracy of the derived flow estimates. Straight-tube models simply cannot serve this purpose, nor can spinning discs that simulate tissue motion instead of flow dynamics. Anthropomorphic bifurcation models are also not ideal, because their geometry does...
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...
Automated robotic inspection systems are a way of speeding up the inspection of large components with complex geometries and reducing production bottlenecks during the non-destructive evaluation of critical parts. Such systems allow the collection of large data volumes, compared to existing inspection systems. To maximise the throughput of the non-destructive evaluation phase, it is crucial that the...
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...
While tissue-mimicking phantoms have been useful in the validation of ultrasonic equipment and image processing techniques, they are often restricted to simple vascular geometries due to limitations in fabrication techniques. To address this need, a novel technique has been employed to fabricate 3D-printed photo-curable poly(ethylene glycol) (PEG) hydrogel constructs containing complex, small-scale...
The k-Wave MATLAB toolbox is widely used to conduct medical ultrasound simulations. These require accurate models of acoustic sources. In k-Wave, a k-space pseudospectral time domain model of acoustic propagation, sources are introduced by adding acoustic pressure at points on a uniform, orthogonal grid. For curved sources two issues arise: First, points on the source's surface do not necessarily...
Gastrointestinal (GI) disease is one of the most common causes of death. Capsule endoscopy (CE) may contribute to early detection of disease and pathological classification. Current CE relies on optical images of the internal luminal surface of the GI tract to aid diagnosis. With the addition of microultrasound, the imaging capability can be extended within the wall of the GI tract, with the potential...
Shear Wave Elasticity Imaging is used to assess liver fibrosis, as shear wave speed (SWS) correlates with fibrosis stage. We have previously proposed a group SWS-based method to derive the tissue's stiffness (μ) and viscosity (η) using an analytic solution for the shear wave propagation in a Voigt material which accounts for the source excitation geometry [Rouze et al., IEEE IUS 2016]. However, in...
Piezoelectric ceramics are currently of considerable interest for their capabilities of converting compressive/tensile stresses to an electric charge, or vice versa. The applications of piezoelectric devises are far reaching, ranging from acoustic imaging to energy harvesting. However, conventional manufacturing processes such as etching and dicing for piezoelectric ceramics fabrication have limited...
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...
Clamp-on ultrasonic flowmeters geometry includes four different materials in the ultrasound propagation path: wedge, coupling material, pipe and liquid. In this case, oblique incidence ray generated by the emitter transducer is splitted into several rays caused by multiple reflections in pipe wall or because of propagation mode conversion at interfaces. These multiple paths are recombined at the reception...
There have been great interests in the nonlinear behavior of SAW resonators but realistic models for their frequency response characteristics have been limited. We present a general purpose finite element model that yields directly the nonlinear frequency response of second harmonic generation in SAW IDT resonators. The nonlinear model enabled us to study the effects of nonlinear material constants,...
Planar arrays comprising a two dimensional arrangement of elements have been extensively used in underwater applications for decades. The beam pattern of a planar array depends upon its aperture geometry. Further, the cost and complication of the underwater array system are highly dependent on the total number and geometry of the array elements, which is very important for underwater vehicles. A fully...
Design and optmiziation of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research projects all faces the problem of scaling up laboratory results for industrial use. A traditional ultrasonic reactor usually has several issues, such as low effectiveness and complex and unstable system performance, which all...
The purpose of this study was to investigate the accuracy and precision of fast plane wave 2-D vector flow imaging (VFI) under laminar and complex flow conditions in a human subject. The method has previously been validated in simulations and straight-vessel phantoms, however, complex flow patterns remain challenging to study, since there are no other imaging techniques accurately enough to compare...
Due to their enhanced properties with respect to conventional piezoelectric ceramics, 1–3 piezocomposite materials are predominant in high performance transducer applications. The determination of their effective electroelastic modulus has been the subject of numerous investigations. Simple modeling of the thickness mode is well documented in literature, however precise simple modeling of the full...
In this study, a comparison between velocity fields for a plane wave 2-D vector flow imaging (VFI) method and a computational fluid dynamics (CFD) simulation is made. VFI estimates are obtained from the scan of a flow phantom, which mimics the complex flow conditions in the carotid artery. Furthermore, the precision of the VFI method is investigated under laminar and complex flow conditions in vivo...
This study assesses the reliance of group shear wave speed calculations on the spatial dependence (source geometry) of an Acoustic Radiation Force Impulse excitation in viscoelastic materials. Furthermore, this work examines the impact of motion filtering on the reliability of a lookup table approach to viscoelastic parameter determination. An analytic solution which includes the effects of source...
The knowledge and determination of effective elastic, piezoelectric and dielectric constants for 1-3 piezocomposites play a key role in understanding and optimizing the performance of the material for various applications. This paper details a theoretical coupled method for determining the effective electroelastic tensors [CE, e, ∊S] of 1–3 piezocomposites with various pillar shapes using computed...
In this work, an all-optical ultrasound imaging system that is capable of synthesising arbitrary source aperture geometries is presented. This capability is achieved by delivering focussed excitation light onto a spatially extended generating surface, where ultrasound is generated photoacoustically. Using a scanning mirror, the position of the resulting acoustical source was continuously varied to...
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