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The ability to measure perfusion rates of tissues in a non-invasive and label-free way could enable powerful diagnostic applications to peripheral vascular disease, ischemia, tumor hypoxia, ulcer characterization, and general tissue health. However, current medical techniques of measuring perfusion rates, which include contrast-enhanced ultrasound imaging, perfusion MR imaging require contrast agents...
We present an ultrasonic transit-time gas flow meter (UFM) that features a 40-kHz 2D-phased array for transmitting ultrasonic sound waves up- and downstream to two single element receivers. This allows us to electronically compensate for the well-known parasitic sound drift effect, and, thus, increasing the measurement range by improving the signal-to-noise-ratio (SNR). A regular double-path UFM consists...
Recent development of the air-coupled sensing technique provides great potential for practical data measurement in the field; however, an improved data analysis method and careful design of test configuration are required to inspect structures appropriately. Impact-echo (IE) is an efficient method to evaluate delamination-like defects in concrete bridge decks. However, practical application of air-coupled...
For evaluation of aged concrete structure, it is expected to apply ultrasonic nondestructive measurement. Special coupling media with high viscosity made scanning difficult and the application to huge structure was not practical. Our group prototyped a couplant-free probe realizing strong acoustic coupling using high pressure due to Hertzian contact and found a potential to excite longitudinal wave...
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...
Ultrasonic sensor has been widely used, ranging from underwater communication to many aspects, such as medical imaging and therapy. Compared with the traditional piezoelectric sensors, Capacitive micro-machined ultrasonic transducer(CMUT) have advantages of wide band, easy to integration, good consistency and low cost, which make it a research hotspot in the field of ultrasound. As the core of the...
In pulse compression using an M-sequence, the M-sequence modulated signal is transmitted and the received signal is correlated with the transmitted signal. However, the M-sequence modulated signal reflected from a moving object is Doppler-shifted. The Doppler-shifted M-sequence modulated signal cannot be correlated with the transmitted signal. Therefore, Doppler velocity estimation from a cyclic M-sequence...
Recently, the maintenance of aging structures such as steel bridge has become an important subject. For example, it is reported that corrosion occurred in a steel plate have broken the steel plate. So, development of the measurement method for residual thickness is desired.
In many industrial technological processes, liquids are subjected to high pressures, e.g., in the high pressure food preservation. Similarly, in modern fuel injection systems for diesel engines, biofuel is subjected to a pressure up to 300 MPa. In such conditions, in liquids, phase transitions can occur that substantially increase the density and liquid viscosity. This can be very detrimental for...
We present a fully-populated 2D-phased array, capable of emitting directed air-coupled ultrasound at 40 kHz without any grating lobes. In comparison to our previous work [Konetzke et al, IUS 2015], in which we describe a 1D-phased array, we use 3D printing techniques to realize a wave guide structure that fulfills the half-wavelength criteria of 4.3 mm. The key idea is to use the wave-guide structure...
Accurate measurement of acoustic dispersion has important applications in theoretical acoustics, ultrasound tissue characterization, ultrasound measurement systems, etc. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this work is focused on the study of the variation in the propagation...
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...
Skin stiffening is an early biomarker of many systemic sclerosis or fibrosis diseases. The Modified Rodnan Skin Score (MRSS) is considered the gold standard measurement in the majority of clinical studies of scleroderma or systemic sclerosis (SSc). However, the MRSS is a subjective palpation method. We have developed a noninvasive ultrasound surface wave elastography (USWE) technique for measuring...
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...
Combined endoscopic imaging and therapeutic tools for minimally invasive procedures may lead to increased efficacy of the procedure and reduced patient risk. Currently, our lab is investigating the use of histotripsy tissue ablation during ultrasound guided neurosurgery. In this work, we will present our progress toward the miniaturization of the histotripsy transducer for simultaneous, real-time...
Ultrasound velocity in soft biological tissues is defined by the molecular composition of the tissues [1]. Water is the main molecular component of soft tissues and muscle water content is typically over 70%. Ultrasound velocity in muscle is a linear function of the water content [2]. Since the muscle is the main water reservoir of human body, measurements of ultrasound velocity in muscle may serve...
Determining physical parameters of thin elastic multi-layers are essential in the field of scientific research and engineering applications. Routine matrix formulations for multilayered media are very complex and involve intensive computation. At the same time, conventional ultrasonic measurements need coupling agents, which greatly limit practical applications. The objective of this research is to...
Lipid-coated microbubbles are being researched as agents for ultrasound imaging and ultrasound-assisted drug delivery. It is well known that lipid shell composition of a microbubble affects the acoustic response. However, the effect of temperature on lipid shell viscoelasticity has not yet been fully established. The goal of this study was to determine the effect of temperature on the viscoelastic...
Periodic calibration of ultrasound imaging and instrumentation systems is critical to identify transducer condition or system failure. Performing impedance measurement allows the monitoring of transducer degradation and cable failure, typically using a dedicated impedance analyzer. This paper proposes a method of concurrent in-situ impedance measurement of all array elements without instrumentation...
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...
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