CFM Mode
8.2.5 Velocity Range (PRF)
The velocity range of the display is governed by the pulse repetition frequency (PRF). The [PRF]
control changes the display range. As you increase the velocity range by that control, the PRF
increases. As the display scale increases, the maximum Doppler shift information that can be
displayed without aliasing also increases.
Use the [PRF] flip switch to adjust the velocity range.
Switching up - the PRF increases.
Switching down - the PRF decreases
Depending on the Box depth the maximum sampling frequency will be automatically reduced.
(If the sampling frequency is no more suitable for the selected depth.)
Changing the PRF display unit from kHz to m/s or cm/s be done in the CFM Sub Menu
(chapter 8.3).
Remarks:
* The current sampling frequency is displayed on the screen [PRF ...]
* Changing the velocity range is only possible in write mode!
8.2.6 Frequency
This control serves for selection of the Transmit Frequency which also depends on the CFM box
position. It is common to work with the Transmit Frequency which is the center frequency (Frequency
mid) of the ultrasound crystal.
With a higher Transmit Frequency (Frequency high) the amplitude of the Doppler spectrum is
displayed larger (advantage: better display of lower flow velocities), but the penetration depth is
reduced.
With a lower Transmit Frequency (Frequency low) the amplitude of the Doppler spectrum is displayed
smaller (advantage: display of higher flow velocities), but the penetration depth is increased (higher
sensitivity).
Switch the [Frequency] key and select the suitable transmit frequency.
low: The transmit frequency is lower than the center frequency of the crystal.
mid: The transmit frequency is the center frequency of the crystal.
high: The transmit frequency is higher than the center frequency of the crystal.
Information of frequencies review: Probes and Biopsy
(chapter 20).
Remarks
:
* Changes are only possible in write mode.
Voluson® 730Pro - Basic User Manual
8-6 105831 Rev. 0
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