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Piezoelectric single crystals (piezocrystals) of lead magnesium niobate-lead titante (PMN-PT) and lead zinc niobate-lead titanate (PZN-PT) have extremely large electromechanical coupling coefficients and exhibit strains of over one percent. The technical significance of these properties to devices is enormous and includes a doubling of bandwidth, decreased package size, and increased resolution. The...
Leukemia commonly leads to hypoxia in the bone marrow, which can then result in increased resistance to chemotherapy. However, the relationship between local hypoxia and disease progression is not well understood, and it is unclear whether hypoxia in the bone marrow is diffuse or focal in presentation. Spectroscopic photoacoustic (PA) imaging-based estimation of blood oxygen saturation (SO2) can be...
Photoacoustic (PA) imaging aims for the reconstruction of acoustic sources that originate in pulsed light absorption. While the speed of sound (SOS) in biological tissue is heterogeneous, standard reconstruction algorithms usually assume a constant SOS. This results in deformations of the reconstructed sources, which are referred to as aberration and can have a severe impact on the spatial resolution...
The development of ultrafast ultrasound imaging brings great opportunities to improve imaging technologies such as shear wave elastography and ultrafast Doppler imaging. In ultrafast imaging, there are trade-offs among image signal-to-noise ratio (SNR), resolution, and the high frame rate. Multiplane wave (MW) imaging is proposed to solve this tradeoff by encoding multiple plane waves with positive/negative...
Robust detection of the smallest circulating cerebral microemboli is an efficient way of preventing cerebrovascular accidents (CVA). Transcranial Doppler ultrasound is widely considered as the most convenient system for the detection of microemboli. Standard detection used in commercial device is achieved through the whole Doppler energy spectrum where constant empirical thresholds are implemented...
Air-coupled transducers are used to conduct fast non-contact inspections in NDT. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled NDT. This paper presents a methodology for improving the bandwidth of an air-coupled diaphragm transducer without sensitivity loss by connecting a number...
A typical medical ultrasound-imaging system consists of a passive probe and a backend system containing the analog frontend and the digital processing unit, to which the probe connects over a coaxial cable harness. Digital processing is increasingly performed in software on powerful GPUs or multicore CPUs. These new system architectures have not only enabled new imaging modalities (Ultrafast Imaging,...
Bonding technology using anisotropic conductive paste shows great promise to achieve the denser integration schemes that are required for the application of high resolution ultrasonic imaging. A design of experiments has been carried out to characterize and optimize a flip-chip bonding technology that utilizes a novel, magnetically aligned anisotropic conductive paste. This optimized process has the...
Photoacoustic (PA) imaging aims for the reconstruction of acoustic sources that originate in pulsed light absorption. While the speed of sound (SOS) in biological tissue is heterogeneous, standard reconstruction algorithms usually assume a constant SOS. This results in deformations of the reconstructed sources, which are referred to as aberration and can have a severe impact on the spatial resolution...
Experimental results from volumetric 3-D vector flow measurements using a 62+62 row-column addressed (RCA) array are presented. A plane-by-plane steered transmit sequence and its post processing steps are described for obtaining 3-D vector flow in a volume. A modified version of the transverse oscillation (TO) velocity estimator is used, which exploits the focal lines generated with the tall elements...
The medical management of patients with continuous-flow left ventricular assist devices (LVADs) requires frequent measurement and analysis of various physiological parameters. Among the most important is blood pressure (BP), which cannot be reliably measured by the standard oscillometric method because of an impaired pulsation due to continuous flow. The objective of this work is to show the feasibility...
Obtaining ultrafast images using steered plane wave (PW) imaging remains a challenge due to the trade-off between image quality and frame rate. PW imaging indeed relies on compounding in order to preserve a good image quality, usually using multiple successive emissions, which in turn yields a decrease of the frame rate. As opposed to this classical approach, we propose a new strategy to reduce the...
Recently a new beamformer called the Delay-Multiply-And-Sum (DMAS) beamformer was introduced in the field of medical ultrasound imaging (Matrone et al IEEE Trans. Med. Imag. 2015). Instead of summing the signals recorded by each transducer element as with the Delay-And-Sum (DAS) beamformer, the DMAS algorithm multiplies the signals pairwise before summing them. This multiplication creates an “artificial...
Accurate characterisation of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. This requires hydrophones calibrated to a traceable standard. The existing implementation of the primary standard at the National Measurement Institutes, e.g., NPL and PTB, can provide accurate calibration to a maximum frequency of 40MHz. However, the increasing use of...
Ultrafast ultrasound has contributed to a renewed interested in vector Doppler. Sampling RF signals at a rate 4 times the carrier frequency is the standard procedure since this rule complies with the Nyquist sampling theorem, regardless of the transducer bandwidth. RF acquisition with a high-performance multi-channel system generates massive datasets, especially in 3-D ultrafast ultrasound. The objective...
Robust detection of the smallest circulating cerebral micro-emboli is an efficient way of preventing Cerebrovascular Accidents. Transcranial Doppler ultrasound is widely considered as the most convenient system for the detection of micro-emboli. Commercially realized standard detection is achieved through the whole Doppler energy spectrum where constant empirical thresholds are implemented. In this...
Our group has previously demonstrated that lower shear rate in the pulsatile blood flow yields greater red blood cell (RBC) aggregation which in turn results in a higher oxygen saturation (sO2) level and a higher photoacoustic (PA) signal. Higher shear rates led to disaggregation thereby decreasing the PA signal amplitude and the sO2. These results suggest that the interrelationship between the sO...
High frame-rate contrast enhanced echocardiography (HFR CE), based on pulse inversion (PI) and diverging wave transmission, was recently proposed for improving the image contrast over standard contrast enhanced ultrasound (CEUS) with focused transmission [M. Toulemonde, IUS 2016]. While it has great potential for improved quantification of myocardium perfusion, it is not clear as whether the stability...
Vector Doppler techniques are ready to substituting the standard methods for blood velocity investigation. However, like in classic Pulse Wave methods, the maximum detectable velocity is related to the Pulse Repetition Frequency (PRF), which is limited by the maximum depth and/or hardware constraints. Unfortunately, the blood velocity, e.g. in stenotic vessels, can easily peak at 2m/s, thus resulting...
We have developed a modern array driver employing multi-channel arbitrary waveform generator and linear amplifiers for transmit wavefront synthesis. The system utilizes deep waveform memory that can be configured for switching between transmit patterns seamlessly thus allowing for the use of spatial and frequency diversity in image acquisition. In this paper, we present the first experimental results...
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