# 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.