scholarly journals Development of High-Frequency (>60 MHz) Intravascular Ultrasound (IVUS) Transducer by Using Asymmetric Electrodes for Improved Beam Profile

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4414 ◽  
Author(s):  
Jin Sung ◽  
Jong Jeong
Keyword(s):  
Intravascular Ultrasound ◽  
Performance Degradation ◽  
Beam Profile ◽  
Center Frequency ◽  
Single Element ◽  
Aperture Size ◽  
Element Analysis ◽  
Signal Line ◽  
Asymmetric Electrodes ◽  
Penetration Depths

In most commercial single-element intravascular ultrasound (IVUS) transducers, with 20 MHz to 40 MHz center frequencies, a conductive adhesive is used to bond a micro-sized cable for the signal line to the surface of the transducer aperture (<1 mm × 1 mm size) where ultrasound beam is generated. Therefore, the vibration of the piezoelectric layer is significantly disturbed by the adhesive with the signal line, thereby causing problems, such as reduced sensitivity, shortened penetration depth, and distorted beam profile. This phenomenon becomes more serious as the center frequency of the IVUS transducer is increased, and the aperture size becomes small. Therefore, we propose a novel IVUS acoustic stack employing asymmetric electrodes with conductive and non-conductive backing blocks. The purpose of this study is to verify the extent of performance degradation caused by the adhesive with the signal line, and to demonstrate how much performance degradation can be minimized by the proposed scheme. Finite element analysis (FEA) simulation was conducted, and the results show that −3 dB, −6 dB, and −10 dB penetration depths of the conventional transducer were shortened by 20%, 25%, and 19% respectively, while those of the proposed transducer were reduced only 3%, 4%, and 0% compared with their ideal transducers which have the same effective aperture size. Besides, the proposed transducer improved the −3 dB, −6 dB, and −10 dB penetration depths by 15%, 12%, and 10% respectively, compared with the conventional transducer. We also fabricated a 60 MHz IVUS transducer by using the proposed technique, and high-resolution IVUS B-mode (brightness mode) images were obtained. Thus, the proposed scheme can be one of the potential ways to provide more uniform beam profile resulting in improving the signal to noise ratio (SNR) in IVUS image.

scholarly journals PMMA-Based Wafer-Bonded Capacitive Micromachined Ultrasonic Transducer for Underwater Applications

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 319 ◽  
Author(s):  
Mansoor Ahmad ◽  
Ayhan Bozkurt ◽  
Omid Farhanieh
Keyword(s):  
Wafer Bonding ◽  
Sacrificial Layer ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Single Element ◽  
Element Analysis ◽  
Laboratory Equipment ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Dry Etch

This article presents a new wafer-bonding fabrication technique for Capacitive Micromachined Ultrasonic Transducers (CMUTs) using polymethyl methacrylate (PMMA). The PMMA-based single-mask and single-dry-etch step-bonding device is much simpler, and reduces process steps and cost as compared to other wafer-bonding methods and sacrificial-layer processes. A low-temperature (< 180 ∘ C ) bonding process was carried out in a purpose-built bonding tool to minimize the involvement of expensive laboratory equipment. A single-element CMUT comprising 16 cells of 2.5 mm radius and 800 nm cavity was fabricated. The center frequency of the device was set to 200 kHz for underwater communication purposes. Characterization of the device was carried out in immersion, and results were subsequently validated with data from Finite Element Analysis (FEA). Results show the feasibility of the fabricated CMUTs as receivers for underwater applications.

scholarly journals DDEL-13. FOCUSED ULTRASOUND MEDIATED BLOOD BRAIN BARRIER DISRUPTION IN A MURINE MODEL OF PONTINE GLIOMA: A SAFETY AND FEASIBILITY STUDY

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii286-iii286
Author(s):  
Zachary Englander ◽  
Hong-Jian Wei ◽  
Antonios Pouliopoulos ◽  
Pavan Upadhyayula ◽  
Chia-Ing Jan ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Focused Ultrasound ◽  
Brain Barrier ◽  
Center Frequency ◽  
Single Element ◽  
Pontine Glioma ◽  
Orthotopic Model ◽  
Function Generator ◽  
Blood Brain ◽  
Glioma Model

Abstract BACKGROUND Drug delivery remains a major obstacle in DIPG, as the blood brain barrier (BBB) limits the penetration of systemic therapies to the brainstem. Focused ultrasound (FUS) is an exciting new technology that, when combined with microbubbles, can open the BBB permitting the entry of drugs across the cerebrovasculature. Given that the utility of FUS in brainstem tumors remains unknown, the purpose of our study was to determine the safety and feasibility of this technique in a murine pontine glioma model. METHODS A syngeneic orthotopic model was established by stereotactic injection of PDGF-B+PTEN-/-p53-/- murine glioma cells (10,000/1ul) into the pons of B6 albino mice. A single-element, spherical-segment FUS transducer (center frequency=1.5MHz) driven by a function generator through a power amplifier (acoustic pressure=0.7MPa) was used with concurrent intravenous microbubble injection (FUS+MB) to sonicate the tumor on post-injection day 14. BBB opening was confirmed with gadolinium-enhanced MRI and Evans blue. Kondziela inverted screen (KIS) testing was completed to measure motor function. Mice were either immediately sacrificed for histopathological assessment or serially monitored for survival. RESULTS In mice treated with FUS (n=11), there was no measured deficit in KIS testing. Additionally, the degree of intra-tumoral hemorrhage and inflammation on H&E in control (n=5) and treated mice (n=5) was similar. Lastly, there was no difference in survival between the groups (control, n=6, median=26 days; FUS, n=6, median=25 days, p&gt;0.05). CONCLUSION FUS+MB is a safe and feasible technique to open the BBB in a preclinical pontine glioma model.

Temperature effect on the tensile behaviors of carbon/polyimide composite laminate

2016 ◽  
Vol 231 (24) ◽  
pp. 4592-4602 ◽  
Author(s):  
Liang Li ◽  
Purong Jia ◽  
Wenge Pan
Keyword(s):  
Temperature Effect ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Thermomechanical Coupling ◽  
Single Element ◽  
Element Analysis ◽  
Open Hole ◽  
Dimensional Finite Element ◽  
Different Temperatures ◽  
Three Dimensional Finite Element

Experimental and numerical investigations were carried out to study the temperature effect on the stiffness, strength, and failure behaviors of carbon/polyimide composite laminates. Both unnotched laminates and open-hole laminates were tested under tension load at three temperatures (room temperature, 200 ℃, and 250 ℃). A three-dimensional finite element analysis was carried out to study the thermomechanical coupling behavior in the notched laminate. The model considers each layer and interface as a single element in the thickness direction so that in-plane stress and interlaminar stress could be analyzed in the model. The stresses around the open-hole changing characteristics with the temperature and tensile loading have been discussed in detail. Failure analysis was carried out to predict the residual strength of the notched laminates at different temperatures. Compared to the experimental data, the numerical results have an excellent agreement.

Simulation and Analysis of the Temperature-Compensated FBAR

2015 ◽  
Vol 719-720 ◽  
pp. 490-495
Author(s):  
Bin Zhou ◽  
Yang Gao ◽  
Yi He ◽  
Wan Jing He
Keyword(s):  
Temperature Coefficient ◽  
Electromechanical Coupling ◽  
Positive Temperature Coefficient ◽  
Frequency Drift ◽  
Center Frequency ◽  
Positive Temperature ◽  
Analysis Software ◽  
Element Analysis ◽  
Simulated Temperature ◽  
Temperature Coefficient Of Frequency

The property of temperature-frequency drift has an effect on the passband ripples, center frequency and insertion loss of FBAR filters, reducing the reliability of its electrical application. A temperature-frequency drift simulation of a typical Mo/AlN/Mo FBAR is achieved by means of finite element analysis software ANSYS, the simulated temperature coefficient of frequency is about-35ppm/°C within the temperature range of-50°C~150°C. By adding a compensated layer with positive temperature coefficient in the FBAR structure, the effects of the compensated layer thickness on temperature-frequency drift, resonant frequency and electromechanical coupling are analyzed. The simulated temperature coefficient of frequency of designed temperature compensated FBAR, which composed of Mo/AlN/SiO2/Mo, is about 0.8ppm/°C, the property of temperature-frequency drift is effectively improved.

Finite Element Modeling of Effect of Adhesive Layer and Carrier Thickness Used for Strain Gauge Mounting

2015 ◽  
Vol 1119 ◽  
pp. 828-832
Author(s):  
K. Vadivuchezhian ◽  
K. Subrahmanya ◽  
N. Chockappan
Keyword(s):  
Finite Element ◽  
Strain Gauge ◽  
Adhesive Layer ◽  
Element Model ◽  
Strain Gauges ◽  
Single Element ◽  
Metal Foil ◽  
Engineering Structures ◽  
Element Analysis ◽  
Typical Strain

Metal foil strain gauges are most widely used for the stress analysis in engineering structures. Typical strain gauge system includes strain sensitive grid, carrier material, and adhesive layer. Strain measurement from the strain gauge is partially affected by carrier and adhesive materials and their thickness. In the present work, a Finite Element Model is developed in order to study the effect of both adhesive layer and carrier thickness on strain measurements while using strain gauges. To understand the behavior of the adhesive material, mechanical characterization is done on bulk adhesive specimen. Finite Element Analysis (FEA) is carried out with different materials namely epoxy and polyurethane. Initially a single element foil loop is considered for the analysis and further this is extended to metal foil strain gauge with nine end-loops. Finally, the strain variation through thickness of adhesive layer, carrier and strain sensitive grid is obtained from FEA. The results thus obtained are compared with analytical results from Basic Strength of Materials approach.

Life Prediction Feasibility in TMF via Stress/Strain Data From a Viscoplasticity-Based Numerical Model

2012 ◽  
Author(s):  
Justin Karl ◽  
Ali P. Gordon
Keyword(s):  
Life Prediction ◽  
Mechanical Load ◽  
Experimental Testing ◽  
Stress And Strain ◽  
Single Element ◽  
Load History ◽  
Analysis Software ◽  
Element Analysis ◽  
Strain Data ◽  
Temperature Strain

Contemporary computing packages handle a wide variety of stress analysis types, but are yet to provide an optimal way to handle certain load cases and geometries. Blades in gas turbine systems, for instance, undergo repetitive thermal and mechanical load cycles of varied shape and phasing. Complexly-shaped airfoils create non-uniform stress paths that exacerbate the problem of FEA software attempting to determine the correct states of stress and strain at any point during the load history. This research chronicles the update and integration of Miller’s original viscoplasticity model with ANSYS finite element analysis software. Elevated temperature strain-controlled LCF and strain-controlled TMF loadings were applied to single-element, uniaxial simulation runs and the results were then compared to data from duplicate experimental testing. Initial findings indicate that the model maintains significant accuracy through several cycles, but longer tests produce varying error in hysteretic response. A review of the modernized implementation of Miller’s viscoplasticity model is presented with a focus on modifications that may be used to improve future results.

Developing the atomic spectrometry techniques for cobalt and nickel analysis

2020 ◽  
pp. 94-101
Author(s):  
V. A. Korotkov ◽  
◽  
T. I. Velikaya ◽  
E. S. Poslavskaya ◽  
◽  
...  
Keyword(s):  
Internal Standard ◽  
Detection Limits ◽  
Atomic Emission ◽  
Atomic Spectrometry ◽  
Atomic Emission Spectrometry ◽  
Emission Spectrometry ◽  
Single Element ◽  
Element Analysis ◽  
Chemical Reagents ◽  
Cobalt And Nickel

The existing methods standardized for to cobalt and nickel analysis, i.e. GOST 13047–2014, GOST 6012–2011 and GOST 8776–2010, don’t correspond to the current and future requirements to these metals in terms of impurities concentration. GOST 13047–2014 provides single-element analysis applications that establish a sample preparation for single element only, takes a lot of efforts and an extremely long time, consume a lot of chemical reagents and are associated with a significant harmful impact on the environment. Being a multielement technique, atomic emission spectrometry with DC-arc spectrum excitation is associated with a high consumption of chemical reagents and a significant environmental impact. It doesn’t allow determining the sulfur and other important impurities. All standard techniques are based on the obsolete principle to dissolve the samples in glass beakers on hot plates. The authors of this paper propose to standardize the methods of atomic emission spectrometry and mass spectrometry (MS) with inductively coupled plasma (ICP) to run cobalt and nickel analysis. 2.5 g samples of cobalt and nickel were proposed to decompose in a mixture of acids in closed polypropylene vessels heated in HotBlock systems at the temperature of 110 оC. This saved up to 5 cm3 of nitric acid and up to 5 cm3 of hydrochloric acid. The solutions of nickel and cobalt were analyzed for impurities on an iCAP 6500 Duo spectrometer at low plasma discharge power and using the base lines as an internal standard. This helped to improve the detection limits of impurities. To select optimal wavelengthes, full spectra of analyzed solutions were captured. Isotope 185Re was chose as internal standard and a collision and reaction cell was used to remove interfering polyatomic ions on an ICP-MS spectrometer iCAP Qc. Nickel and cobalt samples as well as CRMs were analyzed. The impurities detection limits with the current and future cobalt and nickel grades. The methods developed may create the basis for a new GOST standard applicable to cobalt and nickel analysis.

DESIGN AND FABRICATION OF A 20 MHz ANNULAR ARRAY FOR MEDICAL ULTRASOUND

2012 ◽  
Vol 05 (01) ◽  
pp. 1150010
Author(s):  
ZHENHUA HU ◽  
JUE PENG
Keyword(s):  
Focal Point ◽  
Impedance Matching ◽  
Center Frequency ◽  
Depth Of Field ◽  
Single Element ◽  
Medical Ultrasound ◽  
Annular Array ◽  
Array Transducer ◽  
Small Depth

Most high frequency (> 15 MHz) medical ultrasound systems are based on single element transducers mechanically scanned. These systems can provide images with excellent resolution. However, single element transducers are often limited by the fixed focal point and small depth of field. Annular arrays consisting of concentric rings of elements are focused electronically. These arrays are desirable to avoid the fixed focal point of the single element transducers and improve the depth of field. This paper reports the design, fabrication, and characterization of a 5-element equal-area annular array transducer. After electrical impedance matching, the average center frequency was 20 MHz and -6 dB bandwidths ranged from 34 to 42%. The ILs for the matched annuli ranged from 6.1 to 26.5 dB.

A simulation study on tissue harmonic imaging with a single-element intravascular ultrasound catheter

2006 ◽  
Vol 120 (3) ◽  
pp. 1723-1731 ◽  
Author(s):  
Martijn E. Frijlink ◽  
David E. Goertz ◽  
Ayache Bouakaz ◽  
Antonius F. W. van der Steen
Keyword(s):  
Intravascular Ultrasound ◽  
Simulation Study ◽  
Harmonic Imaging ◽  
Single Element ◽  
Tissue Harmonic Imaging
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