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We have applied the minimum variance (MV) adaptive beamformer to medical ultrasound imaging and shown significant improvement in image quality compared to delay-and-sum (DAS). We demonstrate reduced mainlobe width and suppression of sidelobes on both simulated and experimental RF data of closely spaced wire targets, which gives potential contrast and(More)
We introduce a new statistical method, which separates and measures different types of variability between paired ordered categorical measurements. The key to the separation is a two-way augmented ranking approach of observations in a contingency table. It means that cases classified in a specific category by one rater will be internally ranked according to(More)
Recently, significant improvement in image resolution has been demonstrated by applying adaptive beamforming to medical ultrasound imaging. In this paper, we have used the minimum-variance beamformer to show how the low sidelobe levels and narrow beamwidth of adaptive methods can be used, not only to increase resolution, but also to enhance imaging in(More)
  • W Chen, S Holm
  • 2004
Frequency-dependent attenuation typically obeys an empirical power law with an exponent ranging from 0 to 2. The standard time-domain partial differential equation models can describe merely two extreme cases of frequency-independent and frequency-squared dependent attenuations. The otherwise nonzero and nonsquare frequency dependency occurring in many(More)
The classical problem of choosing apodization functions for a beamformer involves a trade-off between main lobe width and side lobe level, i.e., a trade-off between resolution and contrast. To avoid this trade-off, the application of adaptive beamforming, such as minimum variance beamforming, to medical ultrasound imaging has been suggested. This has been(More)
— A unified view of the area of sparse signal processing is presented in tutorial form by bringing together various fields in which the property of sparsity has been successfully exploited. For each of these fields, various algorithms and techniques, which have been developed to leverage sparsity, are described succinctly. The common potential benefits of(More)
— Theory for random arrays predicts a mean side-lobe level given by the inverse of the number of elements. In this paper 1 two optimization methods for thinned arrays are given: one is for optimizing the weights of each element, and the other one optimizes both the layout and the weights. The weight optimization algorithm is based on linear programming and(More)
BACKGROUND AND PURPOSE Interleukin (IL)-23 is a cytokine in the IL-12 family, mainly produced by antigen-presenting cells with a central role in inflammation. We hypothesize that IL-23 is also important in atherogenesis and investigate this in a population with carotid atherosclerosis. METHODS Plasma levels of IL-23 were measured in patients with carotid(More)
BACKGROUND We recently reported that in an experimental setting the zero pressure level of solid intracranial pressure (ICP) sensors can be altered by electrostatics discharges. Changes in the zero pressure level would alter the ICP level (mean ICP); whether spontaneous changes in mean ICP happen in clinical settings is not known. This can be addressed by(More)