scholarly journals Image-Free Ultrasound Blood-Flow Monitoring Circuit System with Automatic Range-Gate Positioning Scheme: A Pilot Study

2021 ◽  
Vol 11 (22) ◽  
pp. 10617
Author(s):  
Hyun-Tae Park ◽  
Ji-Yong Um
Keyword(s):  
Blood Flow ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Single Element ◽  
Proof Of Concept ◽  
Clock Frequency ◽  
Flow Monitoring ◽  
Time Operation ◽  
Manual Adjustment ◽  
Pulsed Wave Doppler

This work proposes a proof-of-concept ultrasound blood-flow-monitoring circuit system using a single-element transducer. The circuit system consists of a single-element ultrasonic transducer, an analog interface circuit, and a field-programmable gate array (FPGA). Since the system uses a single-element transducer, an ultrasound image cannot be reconstructed unless scanning with mechanical movement is used. An ultrasound blood-flow monitor basically needs to acquire a Doppler sample volume by positioning a range gate at a vessel region on a scanline. Most recent single-transducer-based ultrasound pulsed-wave Doppler devices rely on a manual adjustment of the range gate to acquire Doppler sample volumes. However, the manual adjustment of the range gate depends on the user’s experience, and it can be time consuming if a transducer is not properly positioned. Thus, automatic range-gate-positioning is more desirable for image-free pulsed-wave Doppler devices. This work proposes a circuit system which includes a new automatic range-gate-positioning scheme. It blindly tracks the position of a blood vessel on a scanline by using the accumulation of Doppler amplitude deviations and a hysteresis slicing function. The proposed range-gate-positioning scheme has been implemented in an FPGA for real-time operation and is based on addition-only computations, except for filter parts to reduce the complexity of computation in the hardware. The proposed blood-flow-monitoring circuit system has been implemented with discrete commercial chips for proof-of-concept purposes. It uses a center frequency of 2 MHz and a system-clock frequency of 20 MHz. The FPGA only utilizes 5.6% of slice look-up-tables (LUTs) for implementation of the range-gate-positioning scheme. For measurements, the circuit system was utilized to interrogate a customized flow phantom model, which included two vessel-mimicking channels. The circuit system successfully acquired Doppler sample volumes by positioning a range gate on a fluid channel. In addition, the estimated Doppler shift frequency shows a good agreement with the theoretical value.

scholarly journals Fabrication of 2-D Capacitive Micromachined Ultrasonic Transducer (CMUT) Array through Silicon Wafer Bonding

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 99
Author(s):  
Ziyuan Wang ◽  
Changde He ◽  
Wendong Zhang ◽  
Yifan Li ◽  
Pengfei Gao ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Silicon Wafer ◽  
Wafer Bonding ◽  
High Reliability ◽  
Ultrasonic Transducer ◽  
Silicon Film ◽  
Center Frequency ◽  
Single Element ◽  
Flow Monitoring ◽  
Static Capacitance

Capacitive micromachined ultrasound transducers (CMUTs) have broad application prospects in medical imaging, flow monitoring, and nondestructive testing. CMUT arrays are limited by their fabrication process, which seriously restricts their further development and application. In this paper, a vacuum-sealed device for medical applications is introduced, which has the advantages of simple manufacturing process, no static friction, repeatability, and high reliability. The CMUT array suitable for medical imaging frequency band was fabricated by a silicon wafer bonding technology, and the adjacent array devices were isolated by an isolation slot, which was cut through the silicon film. The CMUT device fabricated following this process is a 4 × 16 array with a single element size of 1 mm × 1 mm. Device performance tests were conducted, where the center frequency of the transducer was 3.8 MHz, and the 6 dB fractional bandwidth was 110%. The static capacitance (29.4 pF) and center frequency (3.78 MHz) of each element of the array were tested, and the results revealed that the array has good consistency. Moreover, the transmitting and receiving performance of the transducer was evaluated by acoustic tests, and the receiving sensitivity was −211 dB @ 3 MHz, −213 dB @ 4 MHz. Finally, reflection imaging was performed using the array, which provides certain technical support for the research of two-dimensional CMUT arrays in the field of 3D ultrasound imaging.

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.

Design and Experiment of Capacitive Micromachined Ultrasonic Transducer Array for High-Frequency Underwater Imaging

2020 ◽  
Vol 13 ◽  
Author(s):  
Yuanyu Yu ◽  
Jiujiang Wang ◽  
Xin Liu ◽  
Sio Hang Pun ◽  
Weibao Qiu ◽  
...  
Keyword(s):  
Ultrasound Imaging ◽  
High Frequency ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Design Parameters ◽  
Underwater Imaging ◽  
Release Process ◽  
Steel Wires ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Frequency Ultrasound

Background:: Ultrasound is widely used in the applications of underwater imaging. Capacitive micromachined ultrasonic transducer (CMUT) is a promising candidate to the traditional piezoelectric ultrasonic transducer. In underwater ultrasound imaging, better resolutions can be achieved with a higher frequency ultrasound. Therefore, a CMUT array for high-frequency ultrasound imaging is proposed in this work. Methods:: Analytical methods are used to calculate the center frequency in water and the pull-in voltage for determining the operating point of CMUT. Finite element method model was developed to finalize the design parameters. The CMUT array was fabricated with a five-mask sacrificial release process. Results:: The CMUT array owned an immersed center frequency of 2.6 MHz with a 6 dB fractional bandwidth of 123 %. The pull-in voltage of the CMUT array was 85 V. An underwater imaging experiment was carried out with the target of three steel wires. Conclusion:: In this study, we have developed CMUT for high-frequency underwater imaging. The experiment showed that the CMUT can detect the steel wires with the diameter of 100 μm and the axial resolution was 0.582 mm, which is close to one wavelength of ultrasound in 2.6 MHz.

scholarly journals Anti-N-Methyl-D-Aspartate Receptor Encephalitis with Decrease in Blood Flow in Cerebellum

2021 ◽  
pp. 17-23
Author(s):  
Koji Obara ◽  
Tomoko Ono ◽  
Itaru Toyoshima
Keyword(s):  
Working Memory ◽  
Blood Flow ◽  
Ovarian Teratoma ◽  
Emission Computed Tomography ◽  
High Dose ◽  
Promising Alternative ◽  
Flow Monitoring ◽  
Aspartate Receptor ◽  
Nmdar Encephalitis ◽  
Consciousness Disturbance

In anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, progressive cerebellar atrophy potentially leads to severe sequelae. We encountered a patient with anti-NMDAR antibody encephalitis who showed a decrease of blood flow in the cerebellum. A 15-year-old girl presented with consciousness disturbance. Influenza encephalopathy was suspected, and she was treated with glucocorticoid pulse therapy, high-dose intravenous immunoglobulins, and plasma exchange sequentially. She subsequently underwent left oophorectomy due to the presence of anti-NMDAR antibodies and a left ovarian teratoma. In spite of the surgery, her neuropsychiatric symptoms persisted, and she recovered slowly after the introduction of oral methotrexate (MTX). Sequential cerebral blood flow monitoring with single-photon emission computed tomography showed marked cerebellar hypoperfusion. Although mild impairments including working memory and verbal fluency persisted, she eventually returned to high school 3 years after onset. Profound cerebellar hypoperfusion including lobules VI and VII may be the reason for her working memory impairment and speaking problems. Oral MTX may be a promising alternative treatment for some refractory cases of anti-NMDAR encephalitis.

Postoperative Blood Flow Monitoring after Free-Tissue Transfer by Means of the Hydrogen Clearance Technique

1997 ◽  
Vol 99 (2) ◽  
pp. 493-505 ◽  
Author(s):  
Hans-Guenther Machens ◽  
Peter Mailaender ◽  
Ralf Reimer ◽  
Norbert Pallua ◽  
Yuan Lei ◽  
...  
Keyword(s):  
Blood Flow ◽  
Free Tissue Transfer ◽  
Flow Monitoring ◽  
Tissue Transfer ◽  
Hydrogen Clearance ◽  
Clearance Technique

Intensive blood flow monitoring following femoro-distal bypass: Can early outcome be reliably predicted?

1992 ◽  
Vol 6 (2) ◽  
pp. 148-152 ◽  
Author(s):  
John A. Brennan ◽  
Abigail J. Thrush ◽  
David H. Evans ◽  
Peter R.F. Bell
Keyword(s):  
Blood Flow ◽  
Early Outcome ◽  
Flow Monitoring

scholarly journals Formation of PZT Thick Film Single Elements Using EHDA Deposition

2009 ◽  
Vol 628-629 ◽  
pp. 405-410 ◽  
Author(s):  
Da Zhi Wang ◽  
R.A. Dorey
Keyword(s):  
Thick Film ◽  
Relative Permittivity ◽  
Ultrasonic Transducer ◽  
Sol Gel ◽  
Etching Process ◽  
Single Element ◽  
Electrohydrodynamic Atomization ◽  
Fringe Effect ◽  
Pzt Thick Film

In this paper, electrohydrodynamic atomization combined with a polymeric micromoulding technique was used to form PZT single element devices using a PZT sol-gel slurry without an etching process. The PZT single element device was initially designed to work as a piezoelectric ultrasonic transducer consisting of a circular or a square of various sizes, which was produced and used to evaluate the process. The resulting PZT device had a homogenous microstructure. It was observed that the relative permittivity of the circular and square single element devices was especially high at small size due to the fringe effect. The results show that the radius and width of the PZT single circular and square element devices with a thickness of 15µm should be bigger than 400µm in order to reduce the fringe effect.

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.

An Improved Method for Coronary Sinus Blood Flow Monitoring by Intravascular Doppler Technique

Angiology ◽  
1998 ◽  
Vol 49 (12) ◽  
pp. 975-984
Author(s):  
Pietro Vandoni ◽  
Rodolfo Perondi ◽  
Antonio Saino ◽  
Guido Pomidossi ◽  
Michele Ciulla ◽  
...  
Keyword(s):  
Blood Flow ◽  
Coronary Sinus ◽  
Improved Method ◽  
Doppler Technique ◽  
Flow Monitoring ◽  
Coronary Sinus Blood ◽  
Coronary Sinus Blood Flow

Effects of prior heavy-intensity exercise during single-leg knee extension on v̇o2 kinetics and limb blood flow

2005 ◽  
Vol 99 (4) ◽  
pp. 1462-1470 ◽  
Author(s):  
Nicole D. Paterson ◽  
John M. Kowalchuk ◽  
Donald H. Paterson
Keyword(s):  
Blood Flow ◽  
Phase Ii ◽  
Time Course ◽  
Muscle Blood Flow ◽  
Knee Extension ◽  
Phase Iii ◽  
Limb Blood Flow ◽  
Heavy Exercise ◽  
Pulsed Wave Doppler ◽  
Young Subjects

The effects of prior heavy-intensity exercise on O2 uptake (V̇o2) kinetics of a second heavy exercise may be due to vasodilation (associated with metabolic acidosis) and improved muscle blood flow. This study examined the effect of prior heavy-intensity exercise on femoral artery blood flow (Qleg) and its relationship with V̇o2 kinetics. Five young subjects completed five to eight repeats of two 6-min bouts of heavy-intensity one-legged, knee-extension exercise separated by 6 min of loadless exercise. V̇o2 was measured breath by breath. Pulsed-wave Doppler ultrasound was used to measure Qleg. V̇o2 and blood flow velocity data were fit using a monoexponential model to identify phase II and phase III time periods and estimate the response amplitudes and time constants (τ). Phase II V̇o2 kinetics was speeded on the second heavy-intensity exercise [mean τ (SD), 29 ( 10 ) s to 24 ( 10 ) s, P < 0.05] with no change in the phase II (or phase III) amplitude. Qleg was elevated before the second exercise [1.55 (0.34) l/min to 1.90 (0.25) l/min, P < 0.05], but the amplitude and time course [τ, 25 ( 13 ) s to 35 ( 13 ) s] were not changed, such that throughout the transient the Qleg (and ΔQleg/ΔV̇o2) did not differ from the prior heavy exercise. Thus V̇o2 kinetics were accelerated on the second exercise, but the faster kinetics were not associated with changes in Qleg. Thus limb blood flow appears not to limit V̇o2 kinetics during single-leg heavy-intensity exercise nor to be the mechanism of the altered V̇o2 response after heavy-intensity prior exercise.

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