A5087893919- Ultrasound Imaging and Elastography
- Ultrasound and Hyperthermia Applications
- Ultrasonics and Acoustic Wave Propagation
- Flow Measurement and Analysis
- Photoacoustic and Ultrasonic Imaging
- Ultrasound in Clinical Applications
- Acoustic Wave Resonator Technologies
- Advanced Fiber Optic Sensors
- Underwater Acoustics Research
- Ultrasound and Cavitation Phenomena
- Infrared Thermography in Medicine
- Radiation Dose and Imaging
- Educational Systems and Policies
- Sensor Technology and Measurement Systems
- Analytical Chemistry and Sensors
- Advanced Thermodynamic Systems and Engines
- Optical Imaging and Spectroscopy Techniques
- Bone health and osteoporosis research
- Non-Invasive Vital Sign Monitoring
- Engineering Applied Research
- Non-Destructive Testing Techniques
- Advanced MEMS and NEMS Technologies
- Electromagnetic Launch and Propulsion Technology
- Microbial Inactivation Methods
- Hemodynamic Monitoring and Therapy
United States Food and Drug Administration
2010-2022
University of Idaho
2018-2021
Universidad de las Américas Puebla
2018-2021
North Carolina State University
2014-2021
University of Hawaii System
2013-2021
University of Wisconsin–Madison
2013-2021
University of Maine
2013-2021
University of Illinois Urbana-Champaign
2002-2021
Iowa State University
2021
Idaho State University
2018-2020
The theoretical approaches which have been used to study the velocity potential and pressure fields radiated by a planar piston source vibrating in an infinite rigid baffle are broadly reviewed discussed with emphasis on basic mathematical methods employed. Attention is focused those aspects of theory directly related point or spatially averaged transient field pulsed radiator. Studies nonuniformly also reviewed. Much this material has not previously compared, so where possible common...
The continued examination of potential biological effects ultrasound and their relationship to clinical practice is a key element in evaluating the safety diagnostic ultrasound. Periodically, American Institute Ultrasound Medicine (AIUM) sponsors conferences bringing experts together examine literature on bioeffects develop conclusions recommendations related most recent effort included whose origins were thermal or nonthermal, with separate evaluations for fetal In addition, due...
A theoretical model is presented for evaluating the transient velocity potential and pressure fields radiated by a pulsed planar piston set in an infinite rigid baffle having arbitrary spatial distribution. The method based on development of generalized impulse response function which describes potential, either at point or averaged over finite receiving surface, resulting from excitation uniformly nonuniformly vibrating source. For specific case circular source receiver this plotted using...
Some of the methods, calculations, and problems associated with making hydrophone measurements in diagnostic ultrasound fields are considered. Several organizations have proposed definitions various peak average intensities that need to be specified when characterizing medical fields. All these can determined from measurements, but bandwidths encountered (>50 MHz), along small focal diameters achievable ( approximately 1 mm), place great demands on performance. Two general types hydrophones...
To address the challenges associated with measuring ultrasonic power from high-intensity focused ultrasound transducers via radiation force, a technique based on pulsed measurements was developed and analyzed. Two were characterized in terms of an effective duty factor, which then used to calculate during pulse at high applied levels. absorbing target designs used, both gave comparable results displayed no damage minimal temperature rise if placed near transducer away focus. The method...
Miniature piezoelectric polymer hydrophones for ultrasonic field characterization in the low megahertz region have been developed and tested. The principal advantages of these devices over conventional are their uniform frequency response minimal perturbation field. These characteristics achieved by rendering a small central thin sheet polyvinylidene fluoride locally piezoelectric, then supporting holding it taut metal hoop having dimensions larger than being probed. Both single elements...
Tissue-mimicking materials (TMMs) can provide a convenient, stable, and reproducible means for testing high intensity focused ultrasound (HIFU) devices. When TMMs containing thermal sensors are used to measure ultrasound-induced temperature rise, it is important that measurement results reasonably represent those occur in biological tissue. Therefore the aim of this paper compare behavior TMM under HIFU exposure ex vivo This was accomplished using both previously developed fresh swine muscle...
The traditional method for calculating acoustic pressure amplitude is to divide a hydrophone output voltage measurement by the sensitivity at working frequency, but this approach neglects frequency dependence of sensitivity. Another perform complex deconvolution between waveform and impulse response (the inverse Fourier transform sensitivity). In paper, effects on measurements peak compressional (p+), rarefactional (p-), pulse intensity integral (PII) are studied. Time-delay spectrometry...
The voltage response of ceramic and polyvinylidene fluoride (PVDF) hydrophones was measured in the receive mode for angles incidence ranging from 0 degrees to 90 degrees. measurements were performed at 2.5, 3.5, 5.0, 8.0 MHz; these frequencies are typical those used medical diagnosis. results compared three theoretical models based on diffraction theory; correlation between is evident some PVDF but not others, any hydrophone. effective radius, as defined AIUM-NEMA standard diagnosis...
A tissue-mimicking material (TMM) for the acoustic and thermal characterization of high-intensity focused ultrasound (HIFU) devices has been developed. The is a high-temperature hydrogel matrix (gellan gum) combined with different sizes aluminum oxide particles other chemicals. ultrasonic properties (attenuation coefficient, speed sound, acoustical impedance, conductivity diffusivity) were characterized as function temperature from 20 to 70°C. backscatter coefficient nonlinearity parameter...
Nonlinear acoustic signals contain significant energy at many harmonic frequencies. For applications, the sensitivity (frequency response) of a hydrophone will not be uniform over such broad spectrum. In continuation previous investigation involving deconvolution methodology, (implemented in frequency domain as an inverse filter computed from frequency-dependent sensitivity) was investigated for improvement accuracy and precision nonlinear output measurements. Timedelay spectrometry used to...
This paper describes the development of PVDF hydrophones for characterizing medical ultrasound fields. The polymer hydrophone approaches that have resulted from this work are discussed, with emphasis given to spot-poled membrane design has become de facto reference device these measurements. various national and international standards regulations followed successful use also summarized. works discussed encompass polymer-based designed primarily diagnostic lithotripsy exposure measurements,...
This paper discusses a method currently used to calibrate miniature ultrasonic receivers in the 1- 10-MHz frequency range. The compares power radiated by source transducer integrated intensity obtained scanning receiver across ultrasound field series of linear parallel lines. Sources error are presented and theoretical models experimental data analyzed estimate maximum uncertainty associated with this technique, as Bureau Radiological Health. Our calculations accuracy calibration constants...
A method based on time-delay spectrometry (TDS) was developed for measuring both magnitude and phase response of a hydrophone. The tested several types hydrophones used in medical ultrasound exposimetry over the range from 5 to 18 MHz. These included polyvinylidene fluoride (PVDF) spot-poled membrane, needle, capsule designs. One needle hydrophone designed high-intensity focused (HIFU) applications. average reproducibility (after repositioning hydrophone) measurement 2.4°. minimum-phase...