Showing papers in "Ultrasonic Imaging in 1992"

TL;DR: In this paper, the authors proposed a system for measuring slow, small volume blood flow, such as that found in the capillary beds, which relies on the injection of a strongly nonlinear echocardiographic contrast agent, whose echoes are then analyzed by a modified Doppler process.

TL;DR: In this article, the design, fabrication and evaluation of two-dimensional transducer arrays for medical ultrasound imaging is described, and a 4 x 32, 2.8 MHz array was developed to use new signal processing techniques for improved B-scan imaging including elevation focusing, phase correction and synthetic aperture imaging.

TL;DR: It is indicated that the received pressure field in ultrasound B-mode images can be described by a convolution between a tissue reflection signal and the emitted pressure field by taking into account the dispersive attenuation, the temporal and spatial variation of the pulse, and the change in reflection strength and signal-to-noise ratio.

TL;DR: In this paper, a nonperturbational inverse scattering solution for the scattering integral equation (SIE) is presented, where the numerical discretization of the SIE is performed by the moment method (MM) using sinc basis functions.

TL;DR: This paper describes a method for segmenting transrectal ultrasound images of the prostate using feedforward neural networks, which was trained using a small portion of a training image segmented by an expert sonographer.

TL;DR: Two dimensional arrival time data was obtained for the propagation of ultrasound across the breasts of 7 female volunteers and the results indicate that two dimensional correction algorithms are necessary to restore the system performance losses due to phase aberration.

TL;DR: Measurements of wavefront distortion in the human female breast that indicate that refraction is the dominant distortion mechanism when the ultrasonic phased array is very large are described.

TL;DR: Experimental results verify the superiority of the proposed ML-estimator and the L-ESTimator over the straightforward choice of an arithmetic mean for speckle filtering in simulated tissue mimicking phantom ultrasound B-mode images.

TL;DR: The potential of 2-D arrays for medical imaging is assessed by simulating B-scan images of spherical lesions, both cystic and scattering, embedded in a large random scattering volume, using an 8th order sparse array pattern fabricated on a fixed-focus poly(vinylidene difluoride) transducer using photolithographic techniques.

TL;DR: In this article, a 2D transducer array with symmetric focusing was proposed to improve the image contrast between spherical cysts and the surrounding scattering media in a 3D volume.

TL;DR: This review paper discusses the basic properties of two adaptive signal processing procedures for dealing with weak scattering in a phased array transducer system and suggests that a fundamental improvement in the lateral resolution of ultrasonic echo scanners will result if the weight vector of a large phased array Transducer can be modified to account for distortion in the propagation medium.

TL;DR: In this paper, a novel technique that employs echo signals from moving diffuse targets, such as flowing blood, as an image quality factor to compensate for phase aberration is described, which can be obtained by subtracting the images of two consecutive target interrogations.

TL;DR: In this paper, the inverse scattering formulation has been modified to be applicable in the spectral domain and it implies that enlargement of the discretized cell size is a key factor in regularizing the ill-posedness.

TL;DR: Results indicate that the method uses the brightness of a moving speckle-generating target, such as blood, as a quality factor to correct for unknown phase aberrations can provide significant improvements in image quality when imaging through aberrating media.

TL;DR: Phased-array images have been obtained in vivo with a steered copolymer array operating at 2.5 MHz of the heart of a 25 year-old normal male using the Duke phased-array scanner.

TL;DR: An adaptive algorithm is derived for imaging in an aberrating medium based on wideband (time-domain) linear array data and some tomographic-like filtering schemes that can be applied to improve the quality of the image are suggested.

TL;DR: A method is introduced to evaluate the quality and robustness of estimators for a common signal space covering a wide range of realistic parameter combinations and it is concluded that the complex linear regression estimator exhibits the best quality (low variance and bias of the estimate), robustness and quality for all parameter combinations.

TL;DR: An investigation was performed to determine whether the sound-attenuation-insuspensions theory of Allegra and Hawley can be used to explain the compressional (longitudinal wave) attenuation of ultrasonically tissue-mimicking materials commonly used in phantoms for testing the performance of medical ultrasound systems.

TL;DR: In this paper, the fractal dimension is calculated from the slope of a log-log plot of scattered intensity versus the scattering vector magnitude, and the intensity is measured over a range of magnitudes of scattering vector by varying the scattering angle as well as the ultrasonic frequency.

TL;DR: In this article, a Lagrange-based filter design technique has been developed that not only satisfies the minimum energy criterion, but also constrains sidelobe levels under a certain threshold.

TL;DR: The validity of the inversion scheme to regularization of the noise effects is conformed by showing that averaging the reconstructed profile over each cell with a suitable weighting function reduces the reconstruction error to a nearly negligible value.

TL;DR: The recovery of the acoustical reflectivity function and impedance profile of a layered medium from bandlimited and noisy pulse-echo ultrasonic data is considered and the effects of the transducer and the noise are reduced using Wiener filtering.