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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)
  • 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)
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)
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)
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)
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)
  • W Chen, S Holm
  • 2003
Szabo's models of acoustic attenuation [Szabo, J. Acoust. Soc. Am. 96(1), 491-500 (1994)] comply well with the empirical frequency power law involving noninteger and odd-integer exponent coefficients while guaranteeing causality, but nevertheless encounter the troublesome issues of hypersingular improper integral and obscurity in implementing initial(More)
BACKGROUND AND PURPOSE γ-butyrobetaine (γBB) is a metabolite from dietary Carnitine, involved in the gut microbiota-dependent conversion from Carnitine to the pro-atherogenic metabolite trimethylamine-N-oxide (TMAO). Orally ingested γBB has a pro-atherogenic effect in experimental studies, but γBB has not been studied in relation to atherosclerosis in(More)
Two methods for analyzing intracranial pressure (ICP) waveforms were compared. The frequency domain (FD) method converts the signal from the time domain to the frequency domain by a fast Fourier transform (FFT), while the time domain (TD) method calculates peak-to-peak value of the pulse waveform directly from the time samples. First, the ICP signal was(More)