http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

Continuous monitoring of the central-blood-pressure waveform from deeply embedded vessels, such as the carotid artery and jugular vein, has clinical value for the prediction of all-cause cardiovascular mortality. However, existing non-invasive approaches, including photoplethysmography and tonometry, only enable access to the superficial peripheral vasculature. Although current ultrasonic technologies allow non-invasive deep-tissue observation, unstable coupling with the tissue surface resulting from the bulkiness and rigidity of conventional ultrasound probes introduces usability constraints. Here, we describe the design and operation of an ultrasonic device that is conformal to the skin and capable of capturing blood-pressure waveforms at deeply embedded arterial and venous sites. The wearable device is ultrathin (240 μm) and stretchable (with strains up to 60%), and enables the non-invasive, continuous and accurate monitoring of cardiovascular events from multiple body locations, which should facilitate its use in a variety of clinical environments.

/pdf/monitoring-of-the-central-blood-pressure-waveform-via-a-205q4e1ldq.pdf

Monitoring of the central blood pressure waveform via a conformal ultrasonic device.

Recent progress in flexible and stretchable piezoelectric devices for mechanical energy harvesting, sensing and actuation

Advances in Piezoelectric Polymer Composites for Energy Harvesting Applications: A Systematic Review

/pdf/noninvasive-estimation-of-tumor-interstitial-fluid-pressure-3bvlxhva.pdf

Noninvasive Estimation of Tumor Interstitial Fluid Pressure from Subharmonic Scattering of Ultrasound Contrast Microbubbles

Altered vascular stiffness can influence hemodynamics in the long-term vessel stiffening process, which can be aggravated in a viscous cycle. Elucidation of how vascular stiffness and hemodynamics interact with each other, underpins insights into cardiovascular disease and its diagnosis. In our ultrasound measurement study, the affect of arterial stiffness on hemodynamics is investigated by simulated physiological flow in experimental elastic vessel phantoms based on a 10wt% polyvinyl alcohol aqueous solution that solidifies when subjected to up to 8 freeze-thaw (f-t) cycles. As the vascular phantoms are subjected to these f-t cycles, their Young's modulus, speed of sound, and attenuation coefficients increase. Elastic phantoms of constant inner diameter were subjected to pressure increase in a fluid circuit, resulting in diameter and pulse pressure increments. It can be shown that increased vascular stiffness causes degraded vasomotion and elevated pulse pressure, indicating degradation in the function of blood pumping. Peak velocity measured by Doppler and Echo Particle Image Velocimetry (EchoPIV) techniques have bias less than 5% during the whole cardiac cycle. The EchoPIV results demonstrate parabolic velocity profiles for all three phantoms. Measured peak velocities demonstrate that the stiffer vessel has a smaller peak-to-peak value of velocity, while showing up a slight difference for their shear rate due to their relatively small stiffness differences. In summary, our experiments show that vascular stiffness has influence on vasomotion, flow pressure, flow velocity, and shear rate.

Physiological flow characterization in elastic vessel phantom using Ultrasonic Particle Image Velocimetry

Brain ultrasound has attracted great attention recently due to its noninvasive treatment function for brain diseases. However, ultrasound is still difficult to pass through an intact skull. Phase correction is recognized as an effective method for skull compensation. Half-wavelength pitch transducer is important for the phase correction and, hence, thousands of elements array is required to cover large area human tissue. The clock synchronization between elements is crucial for the phase correction; however, the traditional clock scheme which is designed for 128- or 256-element system is not suitable for thousands of elements. In addition, the clock scheme needs to be magnetic resonance imaging (MRI) compatible since MRI-guided intervention is becoming a routine operation for the brain ultrasound. This study is the first to propose an optical fiber-based clock synchronization method for MRI-guided ultrasound array system. The optical fiber not only distributes the clock but also sets up a link to transmit the data for ultrasound beamformer. The link is full-duplex so both the clock and the data can be transmitted and received simultaneously. The precision of clock synchronization is less than 557 ps when using 50 MHz clock, and the period jitter of the clock is less than 10 ps (rms). Multiple 128- or 256-channel ultrasonic systems can be synchronized, and the error between the channels can be less than 10 ns when using 1-MHz ultrasound transducer. The system can work in an MRI scanning room and communicate with a console via only one fiber. In vivo primate animal study has been achieved, and it has been proven that the proposed clock scheme is suitable for MRI-guided large-scale ultrasound array system.

Fiber-Based Clock Synchronization Method for Medical Ultrasound System

Ultrasound (US) brain stimulation is a promising treatment for epilepsy. However., the mechanism of how US suppresses seizures is unclear. Most of the preclinical tests were performed on anesthetic animals, which limits the accurate assessment of US suppression. In this study, we applied transcranial US with different stimulation paradigms on awake epileptic mice models induced by pentylenetetrazol (PTZ), and evaluated the suppression effects by analyzing the electroencephalographic (EEG) signals, including firing rate of epileptic spikes and spike-wave discharge (SWD). The mice were recovered for 7 days after surgery and then fixed to a constructed platform to perform ultrasound stimulation with fixed or dynamic pulse repetition frequency (PRF). The results showed that sonication of fixed-PRF US 10 minutes before PTZ administration could significantly reduce the number of SWD, and had a tendency to reduce the spike firing rate. In addition, both fixed and dynamic US sonicated right after PTZ administration for 10 minutes had tendency to reduce the spike firing rate. This study explored the suppressive effect of different ultrasound stimulation paradigms on awake and epileptic mice., which shed light on the optimizing stimulation paradigms used in the future clinical application.

Optimizing stimulation paradigms to improve the suppression effect of ultrasonic brain stimulation on seizures

Micro-ultrasound is able to delineate small structures with fine spatial resolution on the order of several tens of microns. It is an invaluable imaging tool for many clinical and preclinical applications. This paper presents the development of an open system for various biomedical studies. The system design was based on field programmable gate array (FPGA) embedded in a printed circuit board to achieve flexible imaging applications. The major image processing algorithms were achieved by the novel field programmable technology for high speed and flexibility. Real-time imaging processing was achieved by fast processing algorithms and high speed data transfer interface. Extensive tests including hardware, algorithms, tissue mimicking phantom, and tissue specimen measurements were conducted to demonstrate good performance of the system. Multi-modality imaging was also facilitated by the developed open system.

Weibao Qiu

Papers

Noninvasive Estimation of Tumor Interstitial Fluid Pressure from Subharmonic Scattering of Ultrasound Contrast Microbubbles

Physiological flow characterization in elastic vessel phantom using Ultrasonic Particle Image Velocimetry

Fiber-Based Clock Synchronization Method for Medical Ultrasound System

Optimizing stimulation paradigms to improve the suppression effect of ultrasonic brain stimulation on seizures

Open system for micro-ultrasound