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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...
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,...
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 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...
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...
Speed of sound (SoS) could prove useful as a biomarker for detecting and staging non-alcoholic fatty liver disease due to its dependence on fat concentration in the liver. However, current ultrasound SoS estimators yield poor accuracy and/or are difficult to implement on traditional pulse-echo scanner architectures. We propose a model and a method to estimate speed of sound in a localized region of...
Echocardiograms are acquired from standard views to ensure correct assessment of cardiac function. There is an increasing use of quantitative tools where specific views are required. Further, non-expert users of echocardiography are increasing, and thus a need for quality assurance during imaging. The aim of this project is to develop automatic and robust real-time classification of cardiac views...
Cortical bone is an anisotropic material with hierarchical structure whose elastic properties are described at different length scales. At millimeter-scale, the whole set of stiffness tensor can be conveniently measured by resonant ultrasound spectroscopy (RUS). At microscopic-scale, micro-indentation and scanning acoustic microscopy are often used to quantify tissue matrix elastic properties. However,...
The postmenopausal osteoporosis is likely influenced by the events taking place during bone development [1]. To prevent future risk of osteoporosis, the appropriate growth of bone during teenagers is important. The ultrasonic bone densitometry is portable and has no radiation exposure, which is suitable for the evaluation of children's bone. In this study, an ultrasonic bone measurement system of...
Contrast enhanced ultrasound (CEUS) has shown great promise in quantifying myocardial perfusion and ventricular flow. More recently high frame-rate contrast enhanced echocardiography (HFR CE), based on pulse inversion (PI) and diverging waves, has shown to significantly improve the image contrast over standard CEUS [M. Toulemonde, IUS 2016]. Both contrast pulse sequences and spatial compounding involve...
Time domain beamforming is an ultrasonic method of imaging point-like scattering objects in low contrast media. This method has been widely applied in medical and industrial ultrasonic imaging modalities, but its resolution is known to be limited by pulse width and frequency. In general, high frequency components of ultrasonic signals are more heavily attenuated, and thus there is a tradeoff between...
Contrast enhanced ultrasound (CEUS) imaging offers great opportunities for new ultrasound applications by improving the contrast between blood and tissue using microbubbles. However, the low signal-to-noise ratio (SNR) due to the low mechanical index (MI) requirement can be an issue in practice. Multiplane wave (MW) imaging is a technique recently proposed to increase the SNR for compounding plane...
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