D
IRECTION FR091521, REVISION 1VIVID S60N/VIVID S70N BASIC SERVICE MANUAL
Chapter 4 - General Procedures and Functional Checks 4-33
PRELIMINARY
4-3-7-3 Using TVI
1) While in 2D mode press TVI on the control panel.
2) Use the trackball (assigned function: Pos) 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.
4-3-7-4 Optimizing TVI
The use of preset gives optimum performance with minimum adjustment. If necessary, the following
controls can be adjusted to further optimize the TVI display:
• 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 value.
NOTE: The Scale value also affects the frame rate. There is a trade off between the frame rate and
quantification noise.
• TVI 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). To obtain radial or circumferential tissue velocities, a
parasternal view must be used. However, from this window the beam cannot be aligned to the
muscle for all the parts of the ventricle.
NOTE: PW will be optimized for Tissue Velocities when activated from inside TVI.
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