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Chapter 1 Safety
Control Eect - Control aecting the Indices
As various system controls are adjusted, the TI and MI values may change. This will be most apparent as
the power control is adjusted; however, other system controls will aect the on-screen output values.
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Power
Power controls the system acoustic output. Two real-time output values are on the screen: a TI and
a MI. They change as the system responds to power adjustments.
At the same time, in combined modes, such as Color, 2D mode, and Pulsed Doppler, each mode is
added onto the total TI. One mode will be the dominant contributor to this total. The displayed MI
will be from the mode with the greatest peak pressure.
2D Mode Controls
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2D Mode Size
Narrowing the sector angle may increase the frame rate. This action will increase the TI. Pulse
voltage may be automatically adjusted down with software controls to keep the TI below the
system maximums. A decrease in pulse voltage will decrease MI.
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Zoom
Increasing the zoom magnication may increase frame rate. This action will increase the TI. The
number of focal zones may also increase automatically to improve resolution. This action may
change MI since the peak intensity can occur at a dierent depth.
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Persistence
A lower persistence will decrease the TI. Pulse voltage may be automatically increased. An increase
in pulse voltage will increase MI.
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Focal No.
More focal zones may change both the TI and MI by changing frame rate or focal depth automatically.
Lower frame rates decrease the TI. The MI displayed will correspond to the zone with the greatest
peak intensity.
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Focus
Changing the focal depth will change the MI. Generally, higher MI values will occur when the focal
depth is near the natural focus of the transducer.
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