GE Versana Essential Technical Publication page 241

Acoustic Output Display Specifications (continued)
Mechanical Index
Changing the Thermal Index Type
TI and MI Display Accuracy
Ispta
Controls Affecting Acoustic Output
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Versana Essential
5759238-100 English Rev. 2
MI recognizes the importance of non-thermal processes,
cavitation in particular, and the Index is an attempt to indicate
the probability that they might occur within the tissue.
You can select the displayed TI type on Utility -> Imaging ->
B-Mode. This preset is application dependent so each
application could specify a different TI type.
When display MI>= 0.6, TI>= 3.6, the displayed values of MI and
IT is not lower than 50% or higher than 150% of the measured
value.
When display MI < 0.6, TI < 3.6, the absolute error of MI <= 0.3,
the absolute error of TI <= 1.8.
The Ispta is the Spatial Peak Temporal Average Intensity. The
absolute maximum regulatory limit of Ispta is 720 mW/cm
set by the FDA 510(k) guidance of September 9, 2008.
The potential for producing mechanical bioeffects (MI) or
thermal bioeffects (TI) can be influenced by certain controls.
Direct. The Acoustic Output control has the most significant
effect on Acoustic Output.
Indirect. Indirect effects may occur when adjusting controls.
Controls that can influence MI and TI are detailed under the
Bioeffects portion of each control in the Optimizing the Image
sections.
Always observe the Acoustic Output display for possible effects.
User Guide
Safety Precautions
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