Doppler Instrumentation Part Two

Signal processing to identify the forward and receive components of the complex Doppler signal.

• Varies the power applied to a txdr.
• Higher power setting result in larger amplitude signals and increased acoustic exposure to patients.

• Adjusts the amt of amplification or gain of the receive signals.
• Does not increase patient exposure.
• Increases the brightness of the spectrum; the brightness can be referred to as the magnitude or amplitude.

Adjusts the volume of the Doppler audio.

• This controls the PRF and therefore the velocity limits of the display.
• Uses a higher PRF to detect higher velocities
• Uses a lower PRF to detect lower velocities.

• It removes these low frequency signals from the display. 
• It does not affect the higher peak Doppler shifts.

• The depth, size and position of the range gate is adjustable.
• It is determined by: beam width, gate length and pulse length.

• Angle cursor is positioned by the operator so that it follows the direction of flow (parallel to vessel wall).
• Angle correction bar is seen diagonally through the range gate relatively parallel to the vessel walls.

• Adjusts the scrolling speed of the Doppler spectrum.
• Adjusts the horizontal axis (time) of the spectral display.