Scanning Modes
Vivid S5/Vivid S6 User Manual 181
R2424458-100 Rev. 2
Power
Controls the amount of acoustic power applied. When power is
reduced the signal to noise ratio is reduced, so that the image
may become noisier.
Cine Compound (Freeze only)
Calculates and displays cineloops generated from a temporal
averaging of multiple consecutive heart cycles. The number of
cycles averaged is controlled from the Soft menu rocker. The
number of averaged cycles displayed on the top left corner.
Using Strain rate
1. From TVI Mode, press ALT on the control panel and press
STRAIN RATE.
2. Use the trackball to position the ROI frame over the area
to be examined.
The assignable con-
trols of the trackball
are displayed in the
trackball status bar
in the bottom right
corner of the screen.
3. Press SET. The instruction Size should be highlighted in the
trackball status bar. If not, press
SET again to select Size.
Note: If the trackball control Pointer is selected, press
TRACKBALL to be able to select between Position and Size
controls.
4. Use the trackball to adjust the dimensions of the ROI.
Optimizing Strain rate
• To reduce quantification noise (variance), the Nyquist limit
should be as low as possible, without creating aliasing. To
reduce the Nyquist limit, reduce the scale while in TVI.
• To check for aliasing, freeze the loop and apply velocity
trace (Press
FREEZE and Q-ANALYSIS), see also Chapter 8,
"Quantitative Analysis" on page 375).
• Strain rate provides velocity information only in the beam
direction. The apical view typically provides the best
window since the beams are then approximately aligned to
the longitudinal direction of the myocardium (except near
the apex).
• There is a trade-off between noise and spatial resolution
controlled by the Strain length. To minimize noise the
Strain length should be maximized. A value of 12mm is
typical for adult cardiac patients.
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