KEYWORDS: Phased arrays, Imaging systems, Digital signal processing, Transducers, Ultrasonography, Silicon carbide, Analog electronics, Human-machine interfaces, Nondestructive evaluation, Control systems
Phased array imaging systems provide the features of electronic beam steering and dynamic depth focusing that cannot
be obtained with conventional linear array systems. This paper presents a system design of a digital ultrasonic imaging
system, which is capable of handling a 64-element 35MHz center frequency phased array transducer. The system
consists of 5 parts: an analog front-end, a data digitizer, a DSP based beamformer, a computer controlled motorized
linear stage, and a computer for post image processing and visualization. Using a motorized linear stage, C-scan images,
parallel to the surface of scanned objects may be generated. This digital ultrasonic imaging system in combination a 35
MHz phased array appears to be a promising tool for NDT applications with high spatial resolution. It may also serve as
an excellent research platform for high frequency phased array design and testing as well as ultrasonic array signal
algorithm developing using system's raw RF data acquisition function.
We report on the development of a multimodal optical coherence tomography (OCT) - ultrasound (US)
system and miniaturized OCT-US probe for intravascular imaging. Both OCT optical components and a US
transducer were integrated into a single probe, enabling both OCT and US imaging at the same time. A
miniaturized OCT-US probe using a single element transducer was designed with a maximum outer diameter
of 0.8 mm, which is suitable for in vivo intravascular imaging. The integrated OCT-US imaging system
adopted a two-channel data acquisition card to digitize both OCT and US signals. Simultaneous OCT and US
data processing and image display were also achieved using our home-developed software. In vitro OCT and
US imaging of human aortic tissue was performed using this multimodal imaging system, which
demonstrated the feasibility of the OCT-US system in intravascular imaging and its potential in detection of
atherosclerotic plaques.
Optical coherence tomography (OCT) and intravascular ultrasound (IVUS) are considered two complementary imaging
techniques in the detection and diagnosis of atherosclerosis. OCT permits visualization of micron-scale features of
atherosclerosis plaque, and IVUS offers full imaging depth of vessel wall. Under the guidance of IVUS, minimal amount
of flushing agent will be needed to obtain OCT imaging of the interested area. We report on a dual-modality optical
coherence tomography (OCT) - ultrasound (US) system for intravascular imaging. To the best of our knowledge, we
have developed the first integrated OCT-US probe that combines OCT optical components with an ultrasound transducer.
The OCT optical components mainly consist of a single mode fiber, a gradient index (GRIN) lens for light beam
focusing, and a right-angled prism for reflecting light into biological tissue. A 40MHz PZT-5H side-viewing ultrasound
transducer was fabricated to obtain the ultrasound image. These components were integrated into a single probe,
enabling both OCT and ultrasound imaging at the same time. In vitro OCT and ultrasound images of a rabbit aorta were
obtained using this dual-modality imaging system. This study demonstrates the feasibility of an OCT-US system for
intravascular imaging which is expected to have a prominent impact on early detection and characterization of
atherosclerosis.
Building photoacoustic imaging systems by using stand-alone ultrasound (US) units makes it convenient to take
advantage of the state-of-the-art ultrasonic technologies. However, the sometimes limited receiving sensitivity and the
comparatively narrow bandwidth of commercial US probes with elements driving long cables may not be sufficient for
high quality photoacoustic imaging. In this work, a high-speed photoacoustic tomography (PAT) system has been
developed using a commercial US unit and a custom built 128-element PVDF transducer array. Since the US unit
supports simultaneous signal acquisition from 64 parallel receive channels, PAT data for synthetic image formation from
a 64 or 128 element array aperture can be acquired after a single or dual laser firing, respectively. The PVDF array
provides satisfactory receiving sensitivity and uniquely broad detection bandwidth, which enables good image quality
for tomographic photoacoustic imaging. A specially designed
128-channel preamplifier board that connects the preamps
directly to the PVDF elements not only enables impedance matching but also further elevates the signal-to-noise ratio in
detecting weak photoacoustic signals. To examine the performance of this imaging system, experiments on phantoms
were conducted and the results were compared with those acquired with commercial US probes.
We report on a dual-modality optical coherence tomography (OCT) ultrasound (US) system for intravascular imaging. To the best of our knowledge, we have developed the first integrated OCT-US probe that combines OCT optical components with an US transducer. The OCT optical components mainly consist of a single-mode fiber, a gradient index lens for light-beam focusing, and a right-angled prism for reflecting light into biological tissue. A 40-MHz piezoelectric transducer (PZT-5H) side-viewing US transducer was fabricated to obtain the US image. These components were integrated into a single probe, enabling both OCT and US imaging at the same time. In vitro OCT and ultrasound images of a rabbit aorta were obtained using this dual-modality imaging system. This study demonstrates the feasibility of an OCT-US system for intravascular imaging, which is expected to have a prominent impact on early detection and characterization of atherosclerosis.
In this paper, the development of a 35 MHz 64-channel Piezoelectric Composite based Micromachined Ultrasound
Transducer (PCMUT) phased array for NDE ultrasound application is presented. A 35 MHz PMN-PT single crystal 1-3
composite based PC-MUT phased array was designed with extensive acoustic field and 1D modeling. The initial
modeling results demonstrated that the focused detection resolution (10% of -3 dB beam width) could be as small as 30
μm in the azimuth direction. The maximum imaging depth for ceramic samples is around 20 mm. The PC-MUT array
being developed will extend the state-of-art NDE phased array technology from approximately 20 MHz to 35 MHz,
which will greatly enhance the imaging resolution for a broad range of NDE ultrasound applications.
A kerfless eight element high frequency ultrasound annular array transducer using 9 μm P(VDF-TrFE) bonded to a high density flexible interconnect was fabricated. The flexible circuit composed of Kapton polyimide film with gold electrode pattern of equal area annuli apertures on the top side of a 50 μm thick Kapton polyimide film. Each element had several 30 μm diameter electroplated vias that connected to electrode traces on the bottom side of the Kapton polyimide film. There was a 30 μm spacing between elements. The total aperture of the array was 3.12 mm. The transducer's performance has been modeled by implementing the Redwood version of the Mason model into PSpice and using the Krimholtz, Leedom and Matthaei (KLM) model utilized in the commercial software PiezoCAD. The transducer’s performance was evaluated by measuring the electrical impedance with a HP 4194 impedance analyzer, pulse echo response using a Panametrics 5900 pulser/receiver and crosstalk measurement for each element in the array. The measured electrical impedance for each element was 540 Ω and -84° phase. In order to improve device sensitivity an inductor was attached in series with each element to reduce the insertion loss to 33 dB. The measured average center frequency and bandwidth of each element was 55 MHz and 50% respectively. The measured crosstalk at the center frequency was -45 dB in water.
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