PD Mode
9.2.4 Frequency
The selection of the transmit frequency depends also on the PD-Box position. It is common to use 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 center frequency desired.
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!
9.2.5 WMF
Wall motion filters are used to eliminate vessel wall motion noise that is low in frequency but high in
intensity. Use a wall filter that is high enough to remove the audible thumping of vessel walls, but that
is sensitive enough to retain grayscale spectral information. The WMF control is used to change the
wall motion filter.
The settings are: low1, low2, mid1, mid2, high1, high2 and max.
Adjust the Wall motion filter by switching the [WMF] control toward up to increase the
filter, by switching down to decrease it.
Remarks:
* The Wall Motion Filter is user-selectable but the actual cutoff frequencies vary depending on the
[PRF] control setting. The lowest wall motion filter cutoff frequencies cannot be used with the
higher PRF setting. Likewise, the highest wall motion filter cutoff frequencies cannot be used
with lower PRF setting.
* Changing the WMF is only possible in write mode!
* The suitable WMF-filter is automatically calculated and adjusted when the PRF is changed.
Voluson® 730Pro - Basic User Manual
9-6 105831 Rev. 0
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