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...

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...

Purpose The purpose of this study was to (1) develop a novel tissue-mimicking thermochromic (TMTC) phantom that permanently changes colour from white magenta upon heating above ablative temperatures, and (2) assess its utility for specific applications in evaluating thermal therapy devices.Materials methods Polyacrylamide gel mixed with ink custom made produce TMTC biological temperatures (> 60 °C). properties the were characterised, compared those human tissue. In addition, as tool...

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...

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...

A new approach for characterizing high intensity focused ultrasound (HIFU) transducers is presented. The technique based upon the acoustic streaming field generated by absorption of HIFU beam in a liquid medium. quantified using digital particle image velocimetry, and numerical algorithm employed to compute giving rise observed field. method as presented here applicable moderate regimes, above intensities which may be damaging conventional hydrophones, but below levels where nonlinear...

The field of high intensity focused ultrasound (HIFU) is developing rapidly. For basic research, quality control, and regulatory assessment a reusable phantom that has both thermal acoustic properties close to soft tissue critical. A hydrogel‐based mimicking material (TMM) been developed shows promise for such phantom. attenuation, speed sound, B/A, diffusivity conductivity, as well the cavitation threshold, were measured found mimic published values tissue. attenuation 0.53f1.04 from 1 MHz...

Cavitation activity and temperature rise have been investigated in a tissue-mimicking material excised bovine liver treated with ethanol insonated 0.825 MHz focused acoustic transducer. The power was varied from 1.3 to 26.8 W find the threshold leading onset of inertial cavitation. events were quantified by three independent techniques: B-mode ultrasound imaging, needle hydrophone measurements passive cavitation detection. Temperature or near focal zone measured thermocouples embedded...

For high intensity therapeutic ultrasound (HITU) devices, pre-clinical testing can include measurement of power, pressure/intensity and temperature distribution, acoustic thermal simulations, assessment targeting accuracy treatment monitoring. Relevant International Electrotechnical Commission documents recently have been published. However, technical challenges remain because the often focused, large amplitude pressure fields encountered. Measurement modeling issues using hydrophones...

Time-delay spectrometry (TDS) is a swept-frequency technique that has proven useful in several ultrasonic applications. Commercial TDS systems are available, but only the audio frequency range. Several research have been constructed, and they used effectively for substitution calibration of hydrophones measurement attenuation sound velocity materials. Unfortunately these depend on features commercial equipment no longer manufactured, so new system designed using modern straightforward signal...

A blood mimicking fluid (BMF) has been developed for the acoustic and thermal characterizations of high intensity focused ultrasound (HIFU) ablation devices. The BMF is based on a degassed de-ionized water solution dispersed with low density polyethylene microspheres, nylon particles, gellan gum, glycerol. broad range physical parameters, including attenuation coefficient, speed sound, viscosity, conductivity, diffusivity, were characterized as function temperature (20-70 degrees C)....

Ultrasound (US) imaging can be enhanced using gas-filled microbubble contrast agents. Strong echo signals are induced at the tissue-gas interface following collapse. Applications include assessment of ventricular function and virtual histology. While ultrasound US agents widely used, their impact on physiological response vascular tissue to vasoactive has not been investigated in detail. In present study, rat dorsal aortas were treated with via a clinical transducer presence or absence...

Egg white, a protein-containing solution, is characterized as blood coagulation surrogate for the acoustical and thermal evaluation of therapeutic ultrasound, especially high intensity focused ultrasound (HIFU) devices. Physical properties, including temperature, frequency dependent attenuation, sound speed, viscosity, were measured function temperature (20–95 °C). Thermal attenuation (5–12 1 MHz) cow blood, pig human also assessed compared with egg white. For 30 s exposure, both white...

Several finite amplitude approaches have been used to determine the nonlinearity parameter B/A of different materials. However, diffraction corrections or measurements far from transmitting transducer are necessary comply with plane wave assumption inherent in classical method. Alternatively, broadband, absolute pressure combination theoretical nonlinear field calculations must be performed. In this study a measurement technique is proposed that eliminates need for any these steps. The...

Time delay spectrometry (TDS) is extended for broadband characterization of plastics (low-density polyethylene, LDPE) and tissue-mimicking material (TMM). The results suggest that TDS the conventional pulse method give comparable measurements frequency-dependent attenuation coefficient phase velocity near center frequency, where signal-to-noise ratio high. However, show enhanced bandwidth 30%−40% (LDPE) 89%−100% (TMM) 43% 36% a single transmitter/receiver pair. In addition, provides...

A polyurethane-based tissue mimicking material (TMM) and blood (BMM) for the acoustic thermal characterization of high intensity therapeutic ultrasound (HITU) devices has been developed. Urethane powder other chemicals were dispersed into either a temperature hydrogel matrix (gellan gum) or degassed water to form TMM BMM, respectively. The ultrasonic properties both including attenuation coefficient, speed sound, acoustical impedance, backscatter characterized at room temperature....

If a hydrophone's sensitivity varies appreciably with frequency, its response must be deconvolved the measured hydrophone signal for accurate pressure measurements. For deconvolution, phase of known. We examine hypothesis that hydrophones behave as minimum systems, in which case can calculated from amplitude via Hilbert transformation. The relative and responses several types were time delay spectrometry. One was piezo-ceramic needle designed high-intensity focused ultrasound (HIFU)...

As new medical applications of ultrasound emerge with operating frequencies in the hundreds kilohertz to low megahertz region, it becomes more important have convenient calibration methods for hydrophones this frequency range. Furthermore, short diagnostic pulses affected by finite amplitude distortion require that hydrophone response be known well below center frequency. National standards laboratories can provide accurate data at these frequencies, but two now employed, laser...