نتایج جستجو برای: ultrasound estimation
تعداد نتایج: 369431 فیلتر نتایج به سال:
BACKGROUND Prostate volume can affect whether patients qualify for brachytherapy (desired size ≥20 mL and ≤60 mL) and/or active surveillance (desired PSA density ≤0.15 for very low risk disease). This study examines variability in prostate volume measurements depending on imaging modality used (ultrasound versus MRI) and volume calculation technique (contouring versus ellipsoid) and quantifies ...
تخمین دقیق مشخصات کانال در سیستم های مخابراتی یک امر مهم محسوب می گردد. این امر به ویژه در کانال های بیسیم با خاصیت فرکانس گزینی و زمان گزینی شدید، چالش بزرگی است. مقالات متعدد پر از روش های مبتکرانه ای برای طراحی و آنالیز الگوریتم های تخمین کانال است که بیشتر آنها از روش های خاصی استفاده می کنند که یا دارای عملکرد خوب با پیچیدگی محاسباتی بالا هستند و یا با عملکرد نه چندان خوب پیچیدگی پایینی...
Introduction: Fetal abdominal circumference (AC) is utilised in calculations for the estimation of fetal weight (EFW) and has been proposed as a method of monitoring diabetic pregnancies. We evaluated true ultrasound accuracy by comparing fetal AC biometry with neonatal anthropometry and compared this with standard ultrasound estimations of fetal weight. Methods: A prospective observational stu...
Estimation of blood velocities using ultrasound and time-domain cross-correlation is investigated. The measurement principle is introduced and the basic properties of the cross-correlation function is discussed. Expressions for the variance of the estimates of the peak location are given showing the innuence of integration time, transducer bandwidth and signal-to-noise ratio. It is also shown t...
One of the important tasks in optoacoustics today is development methods and tools for generating high-frequency ultrasound (above 1 MHz) liquids other media. To expand frequency range ultrasound, it was proposed to use coatings consisting focusing spheres on a fiber tip. The methodology calculating spectra depending sphere size, index refraction, parameters laser radiation developed. Two cases...
Acousto-optic imaging (AOI) enables optical-contrast deep inside scattering samples via localized ultrasound-modulation of scattered light. While AOI allows optical investigations at depths, its resolution is inherently limited by the ultrasound wavelength, prohibiting microscopic investigations. Here, we propose a computational approach that diffraction-limited using conventional system. We ac...
An analytic model is developed for the time-dependent ultrasound field reflected off a randomly rough vibrating surface for a continuously scanning ultrasound vibrometer system in bistatic configuration. Kirchhoff's approximation to Green's theorem is applied to model the three-dimensional scattering interaction of the ultrasound wave field with the vibrating rough surface. The model incorporat...
A key aspect for virtual-reality based ultrasound training is the plausible simulation of the characteristic noise pattern known as ultrasonic speckle. The formation of ultrasonic speckle can be approximated efficiently by convolving the ultrasound point-spread function (PSF) with a distribution of point scatterers. Recent work extracts the latter directly from ultrasound images for use in forw...
The article deals with a comparison of two methods for a detection of artery section area in medical B-mode ultrasound video sequence. Both methods use similar principle for video sequence analysis: the technique of optical flow estimation in selected significant features to track. The difference between the initialization of such points produces results, cardiac cycle curves, which has to be n...
Phase aberration due to tissues with inhomogeneous acoustic speeds is a major source for image degradation in medical ultrasound. In most phased array pulse-echo ultrasound systems, the delay used to steer and focus the beams are calculated assuming constant speed. In practice, however, the acoustic speed varies for different types of tissue. In this paper, we present a method to estimate the p...
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