45 research outputs found
Synthetic Aperture Imaging Using High-Frequency Convex Array for Ophthalmic Ultrasound Applications
No full textHigh-frequency ultrasound (HFUS) imaging has emerged as an essential tool for pre-clinical studies and clinical applications such as ophthalmic and dermatologic imaging. HFUS imaging systems based on array transducers capable of dynamic receive focusing have considerably improved the image quality in terms of spatial resolution and signal-to-noise ratio (SNR) compared to those by the single-element transducer-based one. However, the array system still suffers from low spatial resolution and SNR in out-of-focus regions, resulting in a blurred image and a limited penetration depth. In this paper, we present synthetic aperture imaging with a virtual source (SA-VS) for an ophthalmic application using a high-frequency convex array transducer. The performances of the SA-VS were evaluated with phantom and ex vivo experiments in comparison with the conventional dynamic receive focusing method. Pre-beamformed radio-frequency (RF) data from phantoms and excised bovine eye were acquired using a custom-built 64-channel imaging system. In the phantom experiments, the SA-VS method showed improved lateral resolution (>10%) and sidelobe level (>4.4 dB) compared to those by the conventional method. The SNR was also improved, resulting in an increased penetration depth: 16 mm and 23 mm for the conventional and SA-VS methods, respectively. Ex vivo images with the SA-VS showed improved image quality at the entire depth and visualized structures that were obscured by noise in conventional imaging.11Ysciescopu
Acoustic Power Transfer Using Self-Focused Transducers for Miniaturized Implantable Neurostimulators
No full textAn emerging neurostimulation therapy utilizes electroceuticals to treat numerous neurological disorders. With the aim to discover novel clinical applications of neural stimulation, device miniaturization has been a key challenge for successful clinical translation of implantable stimulators. The battery size has been a limiting factor in further miniaturization, so wireless power transfer without the use of an implanted battery has gained interest. Among various power transfer techniques, acoustic power transfer (APT) provides substantial benefits for powering implantable devices due to its proven safety and efficiency for human body penetration. In this study, we proposed an APT-based neurostimulator with an integrated self-focused 3.6 MHz acoustic transducer and a receiver circuit composed of a power management module and pulse generator. The size of the entire device was 8 mm × 8 mm ×8.6 mm, which is small enough to be implanted with a small incision. A focused beam generated by an external transmitter was received by another focused beam from a receiver transducer, and this optimized pair of transducers with a receiver circuit generated 1.5 V, 1.3 ms pulse trains, which successfully transmitted stimulation pulses. We adopted a 1–3 composite with a piezolayer to implement a curved aperture, which enabled less-attenuated, focused, and matched beams for maximization of power transfer efficiency. We evaluated APT performance through rigorous bench-top and phantom tests and demonstrated the feasibility of stimulation through an in vivo experiment of sciatic nerve stimulation using a rat model.11Ysciescopu
Lead-Free Piezoelectric Composite With Lithium Niobate and Barium Titanate Fabricated by Interdigital Pair Bonding Technique
No full textSince 2003, when the European Union (E.U.) announced the restriction of hazardous substances (RoHS), multiple efforts have been made to replace lead zirconate titanate (PZT) based piezoelectric materials. However, despite these efforts, very few PZT alternatives have been found. The Lithium niobate (LN) is one such lead-free piezoelectric material often used in acoustic applications due to its high signal generation efficiency, high curie temperature, and high mechanical Q factor. However, LN is not suitable for miniaturized applications because of its low dielectric constant and high electrical impedance. In this paper, we aim to address the problem of the low-dielectric constant of LN while avoiding hazardous PZT material. We propose to utilize 1–3 composites structure with LN and barium titanate (BT), which has a high dielectric constant while controlling acoustic properties such as density, dielectric constant, sound velocity. We also developed new LN-BT modeling to design piezoelectric composite with interdigital pair bonding (IPB) technique, based on previous PZT-polymer 1–3 composite modeling. We verified that the composite components are lead-free by examining with the scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). This proposed lead-free composite with high-dielectric and lower electrical impedance is better suited for miniaturized applications
Detection of micro inclusions in steel sheets using high-frequency ultrasound speckle analysis
No full textAbstractWith the increasing need for steel sheet quality assurance, the detection of micro-scaled inclusions in steel sheets has become critical. Many techniques have been explored to detect inclusions, e.g., visual inspection, radiography, magnetic testing, and ultrasound. Among these methods, ultrasound (US) is the most commonly used non-destructive testing (NDT) method due to its ease of use and deep penetration depth. However, ultrasound currently cannot be used for detecting the micro-scaled inclusions due to low spatial resolution, e.g., less than 30 μm, which are the key important factors causing the cracks in the high-quality steel sheets. Here, we demonstrate a high-resolution US imaging (USI) using high-frequency US transducers to image micro inclusions in steel sheets. Our system utilizes through-transmission USI and identifies ultrasound scattering produced by the inclusions. We first ultrasonically imaged the artificial flaws induced by the laser on the steel sheet surface for validating the system. We then imaged the real inclusions in the steel sheets formed during manufacturing processes and analyzed them to derive quantitative parameters related to the number of micro-scaled inclusions. Our results confirm that inclusions less than 30 μm can be identified using our high-resolution USI modality and has the potential to be used as an effective tool for quality assurance of the steel sheets.11Ysciescopu
Thermal Ablation and High-Resolution Imaging Using a Back-to-Back (BTB) Dual-Mode Ultrasonic Transducer: In Vivo Results
No full textWe present a back-to-back (BTB) structured, dual-mode ultrasonic device that incorporates a single-element 5.3 MHz transducer for high-intensity focused ultrasound (HIFU) treatment and a single-element 20.0 MHz transducer for high-resolution ultrasound imaging. Ultrasound image-guided surgical systems have been developed for lesion monitoring to ensure that ultrasonic treatment is correctly administered at the right locations. In this study, we developed a dual-element transducer composed of two elements that share the same housing but work independently with a BTB structure, enabling a mode change between therapy and imaging via 180-degree mechanical rotation. The optic fibers were embedded in the HIFU focal region of ex vivo chicken breasts and the temperature change was measured. Images were obtained in vivo mice before and after treatment and compared to identify the treated region. We successfully acquired B-mode and C-scan images that display the hyperechoic region indicating coagulation necrosis in the HIFU-treated volume up to a depth of 10 mm. The compact BTB dual-mode ultrasonic transducer may be used for subcutaneous thermal ablation and monitoring, minimally invasive surgery, and other clinical applications, all with ultrasound only.11Ysciescopu
CMOS high voltage analog 1-64 multiplexer/de-multiplexer for integrated ultrasound guided breast needle biopsy
No full textUltrasound guided needle biopsy is an important method for collection of breast cancer tissue. In this paper, we report on the design and testing of a high-voltage 1 to 64 Multiplexer/Demultiplexer (MUX/De-MUX) integrated circuit (IC) for ultrasound-guided breast biopsy applications implemented in a high-voltage CMOS process. The IC is intended to be incorporated inside the breast biopsy needle and is designed to fit inside the needle inner diameter of 2.38 mm. The MUX/De-MUX electronics are made up of three parts, including a low-voltage 6 to 64 decoder, a level shifter to convert from low voltage to high voltage, and analog high-voltage switches. Experimental results show a -3-dB bandwidth of over 70 MHz, Rds (on) of 140 Omega, -2.279-dB insertion loss, and -17.5-dB off isolation at 70 MHz with low-voltage input. Finally, we present results obtained via synthetic aperture imaging using the fabricated MUX/De-Mux device and a high-frequency ultrasound array. This device and technique hold promise for high-frequency imaging probes where a limited number of elements are used and the depth of penetration is short such as in breast biopsy and intravascular applications.11Nsciescopu
Evaluation method for acoustic trapping performance by tracking motion of trapped microparticle
No full textWe report a method to evaluate the performances of a single-beam acoustic tweezer using a high-frequency ultrasound transducer. The motion of a microparticle trapped by a 45-MHz single-element transducer was captured and analyzed to deduce the magnitude of trapping force. In the proposed method, the motion of a trapped microparticle was analyzed from a series of microscopy images to compute trapping force; thus, no additional equipment such as microfluidics is required. The method could be used to estimate the effective trapping force in an acoustic tweezer experiment to
assess cell membrane deformability by attaching a microbead to the surface of a cell and tracking the motion of the trapped bead, which is similar to a bead-based assay that uses optical tweezers. The results showed that the trapping force increased with increasing acoustic intensity and duty factor, but the force eventually reached a plateau at a higher acoustic intensity. They demonstrated that this method could be used as a simple tool to evaluate the performance and to optimize the operating conditions of acoustic tweezers.11sciescopu
Exosomes and ultrasound: The future of theranostic applications
No full textBiomaterials and pertaining formulations have been very successful in various diagnostic and therapeutic applications because of its ability to overcome pharmacological limitations. Some of them have gained significant focus in the recent decade for their theranostic properties. Exosomes can be grouped as biomaterials, since they consist of various biological micro/macromolecules and possess all the properties of a stable biomaterial with size in nano range. Significant research has gone into isolation and exploitation of exosomes as potential theranostic agent. However, the limitations in terms of yield, efficacy, and target specificity are continuously being addressed. On the other hand, several nano/microformulations are responsive to physical or chemical alterations and were successfully stimulated by tweaking the physical characteristics of the surrounding environment they are in. Some of them are termed as photodynamic, sonodynamic or thermodynamic therapeutic systems. In this regard, ultrasound and acoustic systems were extensively studied for its ability towards altering the properties of the systems to which they were applied on. In this review, we have detailed about the diagnostic and therapeutic applications of exosomes and ultrasound separately, consisting of their conventional applications, drawbacks, and developments for addressing the challenges. The information were categorized into various sections that provide complete overview of the isolation strategies and theranostic applications of exosomes in various diseases. Then the ultrasound-based disease diagnosis and therapy were elaborated, with special interest towards the use of ultrasound in enhancing the efficacy of nanomedicines and nanodrug delivery systems, Finally, we discussed about the ability of ultrasound in enhancing the diagnostic and therapeutic properties of exosomes, which could be the future of theranostics
Quantification of Inter-Erythrocyte Forces with Ultra-High Frequency (410 MHz) Single Beam Acoustic Tweezer
No full textThe Effect of Mandatory XBRL Reporting across the Financial Information Environment: Evidence in the First Wave of Mandated U.S. Filers
No full textThis study examines the effect of mandatory XBRL disclosure across various aspects of the financial information environment. Our findings show an increase in information efficiency, a decrease in event return volatility, and a reduction of change in stock returns volatility for 428 firms (1,536 10-K and 10-Q filings) post-XBRL disclosure. In addition, this study shows that XBRL mitigates information risk in the market, especially when there is increased uncertainty in the information environment. Our results are robust to various alternative specifications and research modifications such as a matched-pair control (326 XBRL versus 326 non-XBRL firms), current stock market condition, potential earnings releases, and corporate governance. This study contributes to the literature by systematically documenting evidence of how mandatory XBRL disclosure decreases information risk and information asymmetry in both general and uncertain information environments. Our evidence could potentially assist the SEC in their effort to expeditiously assess the benefits of XBRL
