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The large scale oscillation of insonified microbubbles (MBs) is considered to be the primary effect for sonoporation and thus enhances cell transfection in gene therapy. MB destruction on the other hand is suspected to lead to lower transfection rates. For future in vivo therapy, online acoustic monitoring could be used to identify these effects and to determine optimal pulse sequence parameters adaptively...
We describe the first mapping of biological current in a live heart using ultrasound current source density imaging (UCSDI). Ablation procedures that treat severe heart arrhythmias require detailed maps of the cardiac activation wave. UCSDI can potentially improve on existing mapping procedures which are time-consuming and limited by its poor spatial resolution (5-10 mm). UCSDI is based on a pressure-induced...
The TDK model originally developed for capacitive micromachined ultrasonic transducers (CMUT) is applied to the modeling and design of capacitive ultrasonic mass resonators (CUMR). The diaphragm of CUMRs is treated as a laminated plate in tension and supported by elastic foundation, and then its fundamental frequency can be expressed in terms of the stiffness of the diaphragm, tension in it, the electrostatic...
Considerable interest in the elastic properties of soft tissue has developed in medicine due to their clinical relevance for monitoring the progression of various diseases as well as a biomarker for cancer. Most newly developed imaging modalities use shear wave to estimate the elasticity of tissue. A novel surface wave method has been developed by us for non-invasively estimating the elasticity of...
This work presents a distributed nonlinear equivalent circuit to asses the intermodulation distortion (IMD) occurring in a BAW resonator. Closed-form expressions for intermodulation distortion at 2f1-f2 are obtained. Comparisons between analytical and simulated results are in good agreement. Extension of this analysis could be used to predict the nonlinear performance of more complex systems using...
The mechanical nonlinearity due to high power level in zinc oxide thin film bulk acoustic wave resonators has been studied in this work. The nonlinear behavior of these resonators was investigated using transmission response measurements. The resonator was decoupled from the 50 Ohm line impedance by 20 pF shunting capacitors in order to allow the excitation of high mechanical vibration levels at the...
This paper presents the growth and characterization of PZT ferroelectric thin films by using the sol-gel technology. In this paper, we study the influences of annealing temperatures, different film thickness and different substrates, including titanium and platinum layers on silicon substrate, on the ferroelectric performance of PZT thin films by analyzing the polarization hysteresis. The polarization...
The lifetime of active RFID tag is limited by the equipped battery capacity. A passive RFID tag which gathers power via inductive coupling from RF power for temperature sensing was proposed to extend the lifetime of the tag. An oscillator with film bulk acoustic resonator (FBAR) lies at the heart of the tag. A four-layered FBAR with Al/AlN/SiNX/Au composite structure was fabricated. The oscillation...
This paper describes an investigation of determining acoustical physical constants of ZnO. We obtained three specimens of (001)-, (100)-, and (101)-ZnO crystal substrates prepared from three very small single crystals, grown by the hydrothermal synthesis method. We measured bulk-wave velocities in the frequency range from 50 MHz to 300 MHz and LSAW velocities at 225 MHz using the ultrasonic microspectroscopy...
In this paper, we report recent progress that has been made in the development of a high frame rate duplex HF ultrasound system with both B-scan imaging and Doppler flow measurements. A 32-channel HF analog beamformer module with transmitting focusing and dynamic focusing on reception was implemented. High-speed timing circuits were used to achieve high imaging frame rate by reducing the acquisition...
While trained sonographers can reliably diagnose arterial injury using imaging ultrasound in the hospital, a portable ultrasound device with an automated algorithm to detect major bleeding would be useful for medics in the field. We characterized normal blood flow in the upper extremities with an image-based flow model and evaluated its ability to detect vascular abnormalities by looking for flows...
The spectral analysis of echo signals from linear and non-linear scatters is important for understanding the behavior of ultrasound contrast microbubbles (MBs) and assisting the design of insonifying pulse waveforms. Most pulse designs assume a theoretical MB behavior instead of using experimental data despite it being accepted that theoretical models have not succeeded in describing MB behavior....
Possible ways of reducing calibration complexity are considered for a non-contact passive torque and temperature sensor based on three one-port SAW resonators working at 433-437 MHz. A spread of sensor characteristics is investigated and it is shown that dynamic calibration curves differ considerably from the static ones not allowing accelerated temperature variation during calibration. A simplified...
A histomorphological method has been used universally in the researches on the focused ultrasound modifications on the neural tissues, but the dynamic effect is usually unknown. We report on an electrophysiological method to investigate the time-dependent effect of focused ultrasound on the conduction properties of toad's sciatic nerve. It was noticed that focused ultrasound could make the CAPs descend...
This article reports on the fabrication and characterization of lambda-pitched piezoelectric micromachined ultrasound transducer (pMUT) arrays fabricated using a unique process combining conventional silicon technology and low cost screen printing of thick film PZT. The pMUTs are designed as 8 element membrane based devices dimensioned to operate in bending mode in the 1-10 MHz regime. The devices...
Targeted microbubbles bind specifically to molecular markers of diseases and their unique acoustic signature is used to image cellular processes in-vivo. The ability of time reversal processing to focus waves through heterogeneities on such targeted microbubbles is demonstrated. For this purpose, microbubbles were deposited on a gelatin phantom and their specific signal was recorded by a high intensity...
Color flow mapping has become an important clinical tool, for diagnosing a wide range of vascular diseases. Only the velocity component along the ultrasonic beam is estimated, so to find the actual blood velocity, the beam to flow angle has to be known. Because of the unpredictable nature of vascular hemodynamics, the flow angle cannot easily be found as the angle is temporally and spatially variant...
We report on piezoelectrically actuated 13 MHz silicon beam resonators operating in the fundamental length extensional BAW mode. The resonance is evoked using an aluminum nitride layer grown on top of the resonator. We demonstrate quality factors as high as Q~55000 in vacuum, and transduction factors of the order of eta~20 muN=V. The anchor loss is studied using designs with variations in the support...
High frequency ultrasound transducer arrays that can operate at frequencies above 30 MHz are needed for high resolution medical imaging. A key issue in the development of these miniature imaging arrays is the need for photolithographic patterning of array electrodes. To achieve this directly on a 1-3 piezocomposite requires not only planar, parallel and smooth surfaces, but also an epoxy composite...
The 2D P-matrix simulation method is extended to deal with SAW substrates exhibiting a strong anisotropy in slowness and excitation such as YZ-cut lithium niobate.In these substrates the parabolic approximation of the slowness curve is in general not valid. Instead, the exact form of the slowness as obtained from solutions of the basic wave equations of the piezoelectric half space needs to be employed...
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