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Acoustic radiation force has many applications. One of the related technologies is the ability to noninvasively expel stones from the kidney. To optimize the procedure it is important to develop theoretical approaches that can provide rapid calculations of the radiation force depending in stone size and elastic properties, together with ultrasound beam diameter, intensity, and frequency. We hypothesize...
In this work, an effective transcranial imaging technique is proposed to compensate for distortions of ultrasound (US) field caused by skull bone. The results of an experimental study using skull phantoms and 2D synthetic array are presented. The method was used to visualize mm-sized spherical scatterers made from styrofoam as well as a soft silicone tube mimicking a blood vessel. It is shown that...
Recent advances in the field of physical acoustics, imaging technologies, piezoelectric materials, and ultrasonic transducer design have led to emerging of novel methods and apparatus for ultrasonic diagnostics, therapy and body aesthetics. The paper presents the results on development and experimental study of different high intensity focused ultrasound (HIFU) transducers. Technological peculiarities...
Histotripsy is a non-invasive ultrasound therapy which utilizes cavitation clouds to mechanically fractionate tissue. The mechanism by which bubble clouds form is important to understand the histotripsy process. We used high speed imaging with frame rates between 0.1-10 million fps to observe the progression of cloud formation. A 1 MHz spherically-focused transducer was used to apply single histotripsy...
Accurate measurement of pressure waveforms is important for characterization of medical ultrasound equipment. Calibration and measurements can be difficult for high amplitude fields such as those produced by lithotripters. Additionally, it was found previously that the response of membrane hydrophones is sensitive to water conductivity, particularly at low frequencies. The purpose of this study was...
Correct measurement of acoustic pressure is crucial in many applications, e.g. medical diagnostics and therapy, where the physical effect of ultrasound on tissue depends on specific parameters of the wave, such as positive and negative pressure, shock front thickness, and pulse duration. In our previous paper, we reported building a new low-cost PVDF hydrophone to detect broadband signals from lithotripters...
The secular equation for acoustic waves at fluid-solid interfaces yields the common leaky wave and its complement. This complementary wave grows instead of decays with propagation and is time-reversed compared to the leaky wave. Moreover, this growing wave has not yet been observed experimentally, perhaps due to difficulty of its excitation. Experimental observation of this wave was one goal of our...
Identification of stone fragmentation, or comminution, during shock wave lithotripsy (SWL) would aid a urologist in determining the treatment endpoint, but there is currently little feedback available to do so. Here we report the measurement and analysis of SW scattering by kidney stone models in water to study the inverse relationship between stone size and scatter frequency. Stones were exposed...
It is currently difficult to assess whether a kidney stone has fractured during shock wave lithotripsy. Here we report the calculation and measurement of shock wave scattering by stone models in water. Calculations were based on linear elastic theory to find pressure in the fluid and stress in the stone models, and on scattering theory to find radiation from the stone models. Measurements were made...
Calibration of medical shock wave sources is critical and challenging. Aside from the fiber optic probe hydrophone, there are few if any commercially available hydrophones designed for measuring medical shock waves. We have developed a new PVDF membrane hydrophone and compared it to measurements with a fiber optic probe hydrophone (FOPH) in several lithotripters. One part of the hydrophone held the...
The accurate characterization of high intensity focused ultrasound (HIFU) fields is important for the prediction of thermal and mechanical bio-effects in tissue, as well as for the development of standards for therapeutic systems. At HIFU intensity levels, the combined effects of nonlinearity and diffraction result in the formation of asymmetric shocked waveforms and a corresponding distortion of...
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