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Multi-frequency transducers may have a number of emerging applications including multi-scale imaging, superharmonc contrast imaging and imaging-therapy applications. For imaging-therapy applications low-frequencies are typically needed for therapeutic heating or contrast agent destruction, while higher-frequencies are required for high-resolution imaging. However, development of these multi-frequency...
In recent years, focusing an ultrasound beam on a subwavelength scale, i.e. beyond the diffraction limit, has attracted much attention. Under this circumstances, the beam is referred to as a superfocused beam. Focusing beyond the diffraction limit may substantially improve the resolution of ultrasound imaging systems, underwater sonar, and acoustic microscopy. Also, it may further enhance particle...
The study of beampatterns and their use in imaging systems has a long history in optics and acoustics. In addition, the topic of limited diffraction fields has received increasing attention since the characterization of Bessel beams in optics. The class of “localized waves” include X-beams, Airy beams, and related monochromatic and broadband solutions.
Clinical studies using HRpQCT have revealed that cortical bone porosity is a major risk factor for fracture Not only average porosity but also pore size and local accumulation of large basic multicellular units (BMUs) have been associated with a reduction of the hip strength. However, an increase of cortical pore dimensions is poorly captured by X-ray based techniques. A previous in-silico study provided...
Focused ultrasound is a promising method for non-invasive neural stimulation in the brain. Early studies have shown that neurological conditions such as essential tremors can be effectively treated with ultrasound ablation, while sub-thermal stimulation is being explored to probe functional connections in the brain and may have therapeutic benefits in a variety of neurological diseases. Although systems...
Kidney cancer is a severe disease which can be treated by using a non-invasive, controllable and focused ultrasound surgery method-histotripsy. Previously, histotripsy produced by hundred-microsecond-long focused ultrasound pulses has been proposed by us, which generates mechanical homogenized lesion by employing boiling bubbles and high duty cycle compared with conventional methods. However, the...
In previous work, the advantage of using super-harmonic contrast imaging to visualize the microvasculature in tumors and organs has been demonstrated [1]. This was performed using dual frequency (DF) probes consisting of a high frequency single element transducer from a motorized probe concentric with a low frequency ring [2]. However, mechanically scanned systems have limitations, including single...
In the first-in-human trial of ultrasonic propulsion, subjects passed collections of residual stone fragments after repositioning with a C5-2 probe. Here, effectiveness and safety in moving multiple fragments is compared between the C5-2 and a custom SC-50 probe that produces a longer beam and burst duration.
In the acoustic tweezers literature, it is sometimes stated that there would be no radiation pressure in the absence of nonlinearity. In fact, such a circumstance would allow violation of the Second Law of Thermodynamics, an issue we discuss in this talk. In the limit where the Second Law applies, all radiant forms of energy must carry an associated momentum. Shaped beams offer (along with shaped...
The Beam Based Method (BBM) is inspired by bat echolocation as a novel ultrasonic sonar. The method is designed for a system consisting of an emitter and two receivers with a directional beam pattern and was previously tested in simulation with ideally designed beam patterns of the receivers. This sonar aims to support autonomous robot navigation and provide a bat inspired biosonar to improve target...
Ultrasound had been reported to locate the actual in situ focal spot of FUS and to compensate for guidance error due to beam distortion. However it still cannot determine exposure dosage in a clinical setting, therefore monitoring often require MR thermography. The main challenge is that multiple relevant acoustic parameters are not easily isolated from measurable signal characteristics in noninvasive...
The 30MHz lithium niobate (LiNbO3) ultrasound transducer with a highly focused beam was used to generate gradient force which can pull a single leukemia cell to toward a focus to be a trapping situation. The transducer was sterilized by using 70% ethanol before the experiment. Five leukemia cells before treatment and five cells after treatment by a chemotherapy drug were trapped and measured their...
Transcranial focused ultrasound (FUS) is a noninvasive technique for therapy and study of brain neural activation. Here we report on the design and characterization of a new MR-guided FUS transducer for neuromodulation in nonhuman primates at 650kHz. Focus size and grating lobes during electronic steering were quantified using hydrophone measurements in water and a three-axis stage. Pressure output...
High-intensity focused ultrasound (HIFU) have been an attractive research topic for some time now. HIFU studies have started with single-element transducers, but using arrays provide the opportunity to scan the focal point electronically. Modular and scalable driving systems that can be used with custom-made transducer elements to drive these arrays are needed and at the present time there are few...
With the ongoing drive to integrate more functionality and processing power on the same semiconductor area, the device structures have become 3D. Such structures, like FinFETs and their successors Gate-All-Around (GAA) nanowire FETs, bring on new challenges to measure their geometry and material properties non-destructively at the nanometer scale. Photo Thermal Acoustic Imaging (PTAI) is a potential...
A noninvasive measurement of in situ acoustic intensity is useful in a variety of therapeutic applications such as ultrasound induced drug and gene delivery. Some previously proposed methods assumed other acoustic parameters such as scattering coefficient to be constant. This paper proposed a method free of such restrictions, by estimating all the relevant parameters using the highly nonlinear behaviors...
In this work, we present experimental results on subwavelength focusing of an ultrasound beam by a polymer ball-shaped lens (Rexolite) immersed in water at room temperature. The superfocusing phenomenon occurs in the shadow region of the ball lens in the nearfield. The ball lens with radius 12.2 mm yields a focused beam with a 14.4 dB-intensity gain, a subwavelength focal spot with the full width...
Microbubble (MB) volumetric pulsations can be selectively seeded with external ultrasonic fields. The therapeutic use of this phenomenon encompass mechanical thrombolysis and targeted drug deliveries through sonoporating endothelial cells. However, expected outcomes are still plagued by low bubble concentrations and short circulation time after administration. MBs preferentially flow along the centerline...
This article explains how a multi-frequency ultrasonic beam path is split due to passing through dispersive materials and the implications that it has in flow measurement using a Clamp-on ultrasonic flowmeter. The importance of knowing this phenomenon is because dispersive materials are commonly used in the manufacture of transducer wedges and plastic pipes. Splitting of the ultrasonic beam path occurs...
Transcranial focused ultrasound (tFUS) is a novel noninvasive neuromodulation method that has many potential application in the treatment of neuropsychiatric and neurologic disorders. One such application is addiction control through neuromodulation. It is hypothesized that proper stimulation of the nucleus accumbens can help in controlling or suppressing addictive behavior such as alcohol, drug and...
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