Krem Ch5 Flashcards
Autocorrelation
A rapid technique, used in most color Doppler instruments, to obtain mean Doppler-shift frequency.
Baseline shift
Movement of the zero Doppler shift frequency or zero flow speeds line up or down on a spectral display.
Bernoulli effect
Pressure reduction in a region of high-flow speed
Bidirectional
Indicating Doppler instrument capable of distinguishing between positive and negative Doppler shift (approaching and receding flow).
Clutter
Noise in the Doppler signal that generally is caused by high amplitude, Doppler-shifted echoes from the heart or vessel walls.
Color-Doppler display
The presentation of two dimensional, real time Doppler shift information in color superimposed on a real-time grayscale, anatomic, cross-sectional image. Flow directions toward and away from transducer are presented as different colors on the display.
Compliance
Distensibility; non-rigid stretchability a vessels.
Continues-wave Doppler
A Doppler device or procedure that uses continuous wave ultrasound.
Cosine
The cosine angle A in figure C – 1 is the length of side B divided by the length of side see. Abbreviated COS.
Disturbed flow
Flow that cannot be described by straight, parallel streamlines.
Doppler angle
The angle between the sound beam and the flow direction.
Doppler effect
A change in frequency caused by reflector motion.
Doppler equation
The mathematical description of the relationship between Doppler shift, frequency, Doppler angle, propagation speed, and reflector speed.
Doppler-power display
Color Doppler display in which colors are assigned according to the strength (amplitude, power, intensity, energy) of the Doppler shifted echoes.
Doppler shift
Reflected frequency minus incident frequency; the change in frequency caused by motion.
Doppler spectrum
The rate of frequencies present and Doppler shift it echoes.
Duplex instrument
And ultrasound instrument that combines grayscale sonography with pulsed Doppler and, possibly, continuous wave Doppler.
Eddies
Regions of circular flow patterns present in turbulence.
Ensemble length
Number of pulses used to generate one color – Doppler image scan line.
Fast Fourier transform
Digital computer inflammation of the Fourier transform.
Filter
And electric circuit that passes frequency within a defined range.