Ultrasound and Doppler Principles

These flashcards cover key terms and definitions relevant to ultrasound and Doppler principles.

Demodulation

The process of extracting information from a modulated carrier wave.

Doppler Shift

A change in frequency resulting from the movement of a source relative to an observer.

Reynolds Number

A dimensionless quantity used to predict flow patterns in different fluid flow situations.

Continuous Wave

A form of wave where the signal is continuously transmitted, allowing for high velocity measurements without aliasing.

Pulse Wave

A wave that sends out pulses and waits for the echoes, allowing for range resolution in imaging.

Range Resolution

The ability to detect the distance or depth of an object based on the time it takes for an echo to return.

Alias

An error in frequency measurement due to overlapping signals in Doppler ultrasound.

Laminar Flow

A smooth, orderly flow of fluid characterized by layers that slide past one another.

Turbulent Flow

An irregular flow pattern characterized by swirling motions and eddy currents.

Spectral Broadening

Widening of the Doppler spectral waveform, indicating varying velocities within the sample volume.

Bernoulli Effect

Describes how an increase in the speed of a fluid occurs simultaneously with a decrease in pressure.

Grading Lobes

Side lobes produced by array transducers that can lead to unwanted artifacts.

Autocorrelation

A method used in color Doppler to quantify mean velocities of reflected signals.

Fast Fourier Transform (FFT)

A mathematical technique used to analyze the frequency content of signals, providing detailed spectral information.

Transmural Pressure

The pressure difference between the inner and outer walls of a blood vessel.

Wall Filter

A filter that eliminates low-frequency signals to enhance the display of blood flow velocities.

Velocity Map vs. Variance Map

A velocity map indicates flow direction and speed, while a variance map also differentiates between laminar and turbulent flow.

Power Doppler

A technique that detects the presence of blood flow without regard to direction and is sensitive to slower flows.

Harmonic Frequency

A frequency that is an integer multiple of a fundamental frequency, which improves image resolution in ultrasound.

Nyquist Limit

The maximum frequency that can be accurately represented in a digital system, related to the sampling rate.

Packet (Ensemble)

Multiple pulses sent down a scan line in color Doppler to measure velocities more accurately.

Color Bleeding Artifact

Unwanted color that appears outside of blood vessels in color Doppler imaging due to wall motion.

Dynamic Range

The ratio of the largest to smallest values of a physical quantity that a system can process.