PubMed · 575813
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
D R Dietz, S I Parks, M Linzer. 1979. Expanding-aperture annular array.. https://doi.org/10.1177/016173467900100105
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Determination of a complete set of sonographic exposure parameters is desirable for any clinical ultrasound unit and is particularly important in controlled studies of biologic effects. When the exposure system is a diagnostic real-time scanner operating in autoscan mode, the determination of two of these parameters, the spatial average-temporal average (SATA) and the spatial average-pulse average (SAPA) intensities, is not straightforward because of the spatial overlap of successive propagating pulses. A method is described for determining these intensities for autoscan operation. The primary tool in the method is a digital oscilloscope, which supports pretrigger recording and configuring of the oscilloscope's memory into segments that can record rapidly occurring successive pulses, each segment recording one pulse. Results for a few commercially available real-time scanning systems are presented.
Doppler ultrasonography (US) is an invaluable tool in the diagnosis of occlusive vascular disease and is assuming increasing importance in the diagnosis of abdominal, pelvic, and fetal disorders. The author presents for new users the basic physics principles of Doppler US in his discussions of the Doppler principle, instrumentation, signal processing and display, artifacts, and interpretation of data. An understanding of these principles will assist radiologists in using the full potential of Doppler US in the diagnostic workup.
Two new methods for estimating frequency-dependent attenuation are proposed which improve the compromise between the estimation variance of this parameter and the analyzed tissue volume: 1) parametric spectral estimation of the demodulated signal, based on fast Kalman filtering (ARC), 2) implementation of a new mean frequency estimator derived from all the available autocorrelation lags (ACn) of the demodulated signal. Both methods are applied to simulated echo signals. The results are compared to those of other already existing estimators. Both ARC and ACn methods provide equivalent results and a better estimation of attenuation (accuracy ranging from 1.3 to 8%) than the previous methods do (accuracy ranging from 4 to 66%), for analysis windows ranging from 1.5 to 20 microseconds.