Ultrasonic Transducer And Method For Using Same

An improved ultrasonic transducer fabricated on a silicon base has a piezoelectric layer of polyvinylidene fluoride-trfluroethylene copolymer. The piezoelectric layer is sandwiched between two conductive electrodes, all of which are supported on a dielectric layer on top of the silicon base. At least one of the electrodes forms a Fresnel zone plate to focus the ultrasonic signals from the transducers. To improve the performance of the transducer, the silicon base behind the active area is removed, leaving the dielectric layer as a membrane to support the electrodes and the piezoelectric layer. The resulting void in the silicon base is filled with an acoustically matched backing, such as an epoxy, to enhance the wideband performance of the transducer. The transducer is especially suited for characterizing anatomical structures or features requiring very high resolution.Georgia Tech Research Corp.Medical College Of Georgia Research Institut

Instrumentation for propulsion systems development

Apparatus and techniques developed or used by NASA-Lewis to make steady state or dynamic measurements of gas temperature, pressure, and velocity and of the temperature, tip clearance, and vibration of the blades of high-speed fans or turbines are described. The advantages and limitations of each instrument and technique are discussed and the possibility of modifying them for use in developing various propulsion systems is suggested

Two-dimensional optical processing using one-dimensional input devices

Two-dimensional optical processing architectures that are implemented with one-dimensional input spatial light modulators are reviewed. The advanced state of the art of available one-dimensional devices and the flexibility that exists in the design of two-dimensional architectures with one-dimensional transducers leads to the implementation of the most powerful and versatile optical processors. Signal and image processing architectures of this type are discussed

Whole-blood sorting, enrichment and in situ immunolabeling of cellular subsets using acoustic microstreaming

Analyzing undiluted whole human blood is a challenge due to its complex composition of hematopoietic cellular populations, nucleic acids, metabolites, and proteins. We present a novel multi-functional microfluidic acoustic streaming platform that enables sorting, enrichment and in situ identification of cellular subsets from whole blood. This single device platform, based on lateral cavity acoustic transducers (LCAT), enables (1) the sorting of undiluted donor whole blood into its cellular subsets (platelets, RBCs, and WBCs), (2) the enrichment and retrieval of breast cancer cells (MCF-7) spiked in donor whole blood at rare cell relevant concentrations (10 mL− 1), and (3) on-chip immunofluorescent labeling for the detection of specific target cellular populations by their known marker expression patterns. Our approach thus demonstrates a compact system that integrates upstream sample processing with downstream separation/enrichment, to carry out multi-parametric cell analysis for blood-based diagnosis and liquid biopsy blood sampling

Refraction-corrected ray-based inversion for three-dimensional ultrasound tomography of the breast

Ultrasound Tomography has seen a revival of interest in the past decade, especially for breast imaging, due to improvements in both ultrasound and computing hardware. In particular, three-dimensional ultrasound tomography, a fully tomographic method in which the medium to be imaged is surrounded by ultrasound transducers, has become feasible. In this paper, a comprehensive derivation and study of a robust framework for large-scale bent-ray ultrasound tomography in 3D for a hemispherical detector array is presented. Two ray-tracing approaches are derived and compared. More significantly, the problem of linking the rays between emitters and receivers, which is challenging in 3D due to the high number of degrees of freedom for the trajectory of rays, is analysed both as a minimisation and as a root-finding problem. The ray-linking problem is parameterised for a convex detection surface and three robust, accurate, and efficient ray-linking algorithms are formulated and demonstrated. To stabilise these methods, novel adaptive-smoothing approaches are proposed that control the conditioning of the update matrices to ensure accurate linking. The nonlinear UST problem of estimating the sound speed was recast as a series of linearised subproblems, each solved using the above algorithms and within a steepest descent scheme. The whole imaging algorithm was demonstrated to be robust and accurate on realistic data simulated using a full-wave acoustic model and an anatomical breast phantom, and incorporating the errors due to time-of-flight picking that would be present with measured data. This method can used to provide a low-artefact, quantitatively accurate, 3D sound speed maps. In addition to being useful in their own right, such 3D sound speed maps can be used to initialise full-wave inversion methods, or as an input to photoacoustic tomography reconstructions

Precision optical angular position marker system for rotating machinery

An optical system is described which generates one or more markers of the angular shaft position of rotating machinery. The system consists of a light source, an optical cable, a machinery mounted lens assembly, a light detector, and a signal conditioner. Light reflected by targets on the rotor is converted to a digital output signal. The system is highly immune to extreme environments of vibration and temperature and achieved a 0.002 percent precision under operational test conditions

Sonoporaton and Impedance Spectroscopy for the Assistance with and Observation of Development of Healthier Embryos and Fetuses.

M.S. Thesis. University of Hawaiʻi at Mānoa 2017

Transducers for measuring acoustic transients

This thesis is concerned with the design and development of measuring devices for the characterisation of acoustic transients with high temporal and spatial resolution. Three new techniques are demonstrated characterising acoustic transients generated by Nd-YAG laser (1060nm, 30ns, 55mJ) assisted breakdown of water and air. The first technique demonstrates the use of a high power semiconductor laser in a high speed multiple exposure imaging system. This system developed is capable of illuminating an event with up to 10 pulses of light at a maximum repetition rate of 5MHz, with a timing accuracy of ≈5ns. Each semiconductor laser light pulse has a FWHM duration of 50ns, peak power of 30W, and a wavelength of 860nm. Images of individual acoustic transients are displayed on the same CCD camera frame, and it was found that this is best achieved using a dark field imaging technique such as Schlieren imaging. [Continues.

Investigation of ultrasonic properties of MAGIC gels for pulse-echo gel dosimetry

This thesis describes investigations into the design and evaluation of novel ultrasonic methods for 3-dimensional ionising radiation dose verification. Pulse-echo ultrasound methods were investigated for the measurement and analysis of complex radiation therapy dose delivery.The physical properties of MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) polymer gel dosimeters have been characterized. The variations of speed of sound, ultrasonic attenuation coefficient and density of MAGIC gel with radiation dose and temperature have been quantified. This extends work that has previously been reported for the properties of this gel to the effect of measurement temperature on the results. The facilities to perform these measurements were specified, constructed and evaluated as part of the project.The measurement of radiation dose using ultrasound back scatter from an interface between the polymer gel dosimeter and an inert reflector is demonstrated. To enable the measurement of radiation dose using pulse-echo ultrasound methods a novel inert material has been specified, manufactured and characterised. This material is matched to the acoustic impedance of MAGIC gel to produce the most dose-sensitive reflections.The reflections from the interface between the inert reflector and dose-dependent MAGIC gel have been analysed using both a single element transducer and a commercial ultrasound scanner. Both measurement systems demonstrate the same dose and temperature dependence of the ultrasonic reflection. A methodology has been developed to relate pixel values from the ultrasound scanner to the amplitude of the reflected ultrasound signal. A phantom consisting of an array of threads formed from the inert backscattering material has been designed and constructed and a method of extracting pixel data from images of the array acquired using a commercial ultrasound scanner has been developed, so that multiple imaging positions could be used to perform a 3-dimensional assessment of radiation dose distributions.It has been demonstrated that a pulse-echo technique using a commercial ultrasound scanner shows promise for radiation gel dosimetry. Further investigation and alternative polymer gel and inert reflector combinations may improve these techniques