摘要 :
A speckle pattern interferometric system which uses the properties of ultrasonic speckles has been studied. Traditionally, ultrasonic speckle patterns have been considered as annoyances which do not transfer useful information. Ho...
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A speckle pattern interferometric system which uses the properties of ultrasonic speckles has been studied. Traditionally, ultrasonic speckle patterns have been considered as annoyances which do not transfer useful information. However, changing this viewpoint, we have regarded speckle as containing useful information, and conceptually have examined the possibility of ultrasonic digital speckle pattern interferometry and discussed several possible setups. The suggested method of this paper needs to be proved by experimental results. If proved, this method can be applied to the analysis of material characteristics. (C) 1997 Elsevier Science B.V. [References: 14]
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Conventional ultrasound imaging probes typically comprise finite-sized arrays of periodically spaced transducer elements which, in the case of phased arrays, can result in severe grating and sidelobe artifacts. Whereas side lobes ...
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Conventional ultrasound imaging probes typically comprise finite-sized arrays of periodically spaced transducer elements which, in the case of phased arrays, can result in severe grating and sidelobe artifacts. Whereas side lobes can be effectively suppressed through amplitude apodization ("AmpA"), grating lobes arising from periodicity in transducer placement can only be suppressed by decreasing the element pitch, which is technologically challenging and costly. In this work, we present source density apodization ("SDA") as an alternative apodization scheme, where the spatial source density (and, hence, the element pitch) is varied across the imaging aperture. Using an all-optical ultrasound imaging setup capable of video-rate 2-D imaging as well as dynamic and arbitrary reconfiguration of the source array geometry, we show both numerically and experimentally how SDA and AmpA are equivalent for large numbers of sources. For low numbers of sources, SDA is shown to yield superior image quality as both side and grating lobes are effectively suppressed. In addition, we demonstrate how asymmetric SDA schemes can be used to locally and dynamically improve the image quality. Finally, we demonstrate how a nonsmoothly varying spatial source density (such as that obtained for randomized arrays or in the presence of source positioning uncertainty or inaccuracy) can yield severe image artifacts. The application of SDA can, thus, yield high image quality even for low channel counts, which can ultimately result in higher imaging frame rates using acquisition systems of reduced complexity.
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Synthetic aperture imaging employing a single active array channel in data acquisition, enables low cost systems to be realised, but produces poor image quality. An investigation is presented into a new synthetic aperture system w...
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Synthetic aperture imaging employing a single active array channel in data acquisition, enables low cost systems to be realised, but produces poor image quality. An investigation is presented into a new synthetic aperture system which uses a single active transmit element and two active receive elements to carry out data acquisition. This approach improves the image quality by suppressing the grating and sidelobes, while preserving the simplicity of the front-end hardware.
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Ultrasonic probes for high temperature measurements in immersion are presented. These probes consist of piezoelectric transducers and buffer rods, and may be operated in the pulse echo mode. The probes can operate to temperatures ...
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Ultrasonic probes for high temperature measurements in immersion are presented. These probes consist of piezoelectric transducers and buffer rods, and may be operated in the pulse echo mode. The probes can operate to temperatures as high as 215℃ without requiring a cooling system. For imaging purposes, one end of the clad buffer rod is machined into a semi-spherical concave shape, of which the purpose is to focus the ultrasound. The operating frequency is between 5 and 9 MHz. Ultrasonic images, produced using a mechanical raster scan with the probes fully immersed in silicone oil at elevated temperatures, are presented. The importance of the signal-to-noise ratio in the pulse-echo measurement is discussed.
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Spectrum analysis procedures have been developed to improve upon the diagnostic capabilities afforded by conventional ultrasonic images. These procedures analyze the frequency content of broadband, coherent echo signals returned f...
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Spectrum analysis procedures have been developed to improve upon the diagnostic capabilities afforded by conventional ultrasonic images. These procedures analyze the frequency content of broadband, coherent echo signals returned from the body. They include calibration procedures to remove system artifacts and thereby provide quantitative measurements of tissue backscatter. Several independent spectral parameters have been used to establish databases for various organs; several investigations have shown that these parameters can be used with statistical classifiers to identify tissue type. Locally computed spectra have been used to generate sets of images displaying independent spectral parameters. Stained images have been derived by analyzing these parameter images with statistical classifiers and using color to denote tissue type (e.g., cancer). This report describes spectrum analysis procedures, discusses how measured parameters are related to physical tissue properties, and summarizes results describing estimator precision. It also presents illustrative clinical results showing how such procedures are being adapted to address specific clinical problems for a number of organs. This report indicates where further developments are needed and suggests how these techniques may improve image segmentation for three-dimensional displays and volumetric assays.
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The development of 3-D ultrasound imaging is a way to address the disadvantages of conventional ultrasound imaging. In this article the authors review approaches that have been attempted in the development of 3-D ultrasound imagin...
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The development of 3-D ultrasound imaging is a way to address the disadvantages of conventional ultrasound imaging. In this article the authors review approaches that have been attempted in the development of 3-D ultrasound imaging such as 3-D B-mode, color Doppler, and power Doppler systems. Acquisition, reconstruction, and rendering techniques for 3-D imaging are discussed, as well as applications and limitations.
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This paper describes the development of a miniaturized high-frequency linear array that can be integrated within a core biopsy needle to improve tissue sampling accuracy during breast cancer biopsy procedures. The 64-element linea...
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This paper describes the development of a miniaturized high-frequency linear array that can be integrated within a core biopsy needle to improve tissue sampling accuracy during breast cancer biopsy procedures. The 64-element linear array has an element width of , kerf width of , element length of 1 mm, and element thickness of . The 2–2 array composite was fabricated using deep reactive ion etching of lead magnesium niobate-lead titanate (PMN-PT) single crystal material. The array composite fabrication process as well as a novel high-density electrical interconnect solution are presented and discussed. Array performance measurements show that the array had a center frequency and fractional bandwidth ( ) of 59.1 MHz and 29.4%, respectively. Insertion loss and adjacent element crosstalk at the center frequency were and , respectively. A B-mode image of a tungsten wire target phantom was captured using a synthetic aperture imaging system and the imaging test results demonstrate axial and lateral resolutions of 33.2 and , respectively.
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Data acquisition rates in pulsed ultrasound scanners are limited by the speed of sound in the human body. This poses severe limitations to the design of future ultrasound equipment, such as 3-D imaging scanners. The authors descri...
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Data acquisition rates in pulsed ultrasound scanners are limited by the speed of sound in the human body. This poses severe limitations to the design of future ultrasound equipment, such as 3-D imaging scanners. The authors describe a technique for higher data acquisition rates based on the simultaneous transmission of multiple beams. By using a linear combination of the received beams, interbeam interference due to the sidelobe energy of the transmitting beams can be significantly reduced. The transformation coefficients are found by using a least squares minimization criterion. A simulation environment used for the evaluation of the authors' methodologies and various simulation results are presented.
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In the medical fields, ultrasound detection is often performed with piezoelectric arrays that enable one to simultaneously map the acoustic fields at several positions. In this work, we develop a novel method for transforming a si...
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In the medical fields, ultrasound detection is often performed with piezoelectric arrays that enable one to simultaneously map the acoustic fields at several positions. In this work, we develop a novel method for transforming a single-element ultrasound detector into an effective detection array by spatially filtering the incoming acoustic fields using a binary acoustic mask coded with cyclic Hadamard patterns. By scanning the mask in front of the detector, we obtain a multiplexed measurement data set from which a map of the acoustic field is analytically constructed. We experimentally demonstrate our method by transforming a single-element ultrasound detector into 1-D arrays with up to 59 elements.
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Endoscopic ultrasound (EUS), an interventional imaging technology, utilizes a circular array to delineate the cross-sectional morphology of internal organs through the gastrointestinal (GI) track. However, the performance of conve...
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Endoscopic ultrasound (EUS), an interventional imaging technology, utilizes a circular array to delineate the cross-sectional morphology of internal organs through the gastrointestinal (GI) track. However, the performance of conventional EUS transducers has scope for improvement because of the ordinary piezoelectric parameters of Pb(Zr, Ti)
$\text{O}_{{3}}$
(PZT) bulk ceramic as well as its inferior mechanical flexibility which can cause material cracks during the circular shaping process. To achieve both prominent imaging capabilities and high device reliability, a 128-element 6.8-MHz circular array transducer is developed using a Pb(Mg
$_{\text {1/3}}$
Nb
$_{\text {2/3}}$
)
$\text{O}_{{3}}$
-PbTiO
3
(PMN-PT) 1–3 composite with a coefficient of high electromechanical coupling (
${k}_{{\text {t}}} \sim 0.78$
) and good mechanical flexibility. The characterization results exhibit a large average bandwidth of 58%, a high average sensitivity of 100 mV
pp
, and a crosstalk of less than −37 dB near the center frequency. Imaging performance of the PMN-PT composite-based array transducer is evaluated by a wire phantom, an anechoic cyst phantom, and an
ex-vivo
swine intestine. This work demonstrates the superior performance of the crucial ultrasonic device based on an advanced PMN-PT composite material and may lead to the development of next-generation biomedical ultrasonic devices for clinical diagnosis and treatment.
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