GE Vivid S70, Руководство пользователя

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Strain rate
Vivid S70 / S60
–
User Manual
5-31
BC092760-1EN 01
Using Strain rate
1. From TVI Mode, press Strain rate .
2. Use the trackball to position the ROI frame over the area to
be examined.
3. Press Select . The instruction
Size
should be highlighted in
the trackball status bar.
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 dimension 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
‘Quantitative Analysis’ on
page 9-1
).
• Strain rate provides 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 control. To minimize noise
the Strain length should be maximized.
• The maximum Strain rate that is color-coded can be
adjusted using the
SRI scale control. If set too low, most of
the wall will show the color indicating maximum Strain rate.
If set too high, the maximum Strain rate color is never
reached.
• Low strain rates may be masked out with a green color
using the
SRI Reject control.