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Safety
Vivid i User’s Manual
353
2378958-100 Rev. 02
Acoustic output
Definition of the acoustic output
parameters
Thermal Index
TI is an estimate of the temperature increase of soft tissue or
bone. There are three thermal index categories:
• TIS: Soft tissue thermal index. The main TI category. Used
for applications that do not image bone.
• TIB: Bone thermal index (bone located in a focal region).
Used for fetal application.
• TIC: Cranial bone thermal index (bone located close to the
surface). Used for transcranial application.
Mechanical Index
MI is the estimated likelihood of tissue damage due to
cavitation. The absolute maximum limits of the MI is 1.9 as set
by the FDA 510(k) guidance of 1997.
Ispta
The Ispta is the Spatial Peak Temporal Average Intensity. The
absolute maximum limit of Ispta is 720 MW/cm
2
as set by the
FDA 510(k) guidance of 1997.
Acoustic output and display on the
Vivid
i
In the title bar, two fields are allocated for the display of power
values as shown in Figure 14-1.
Figure 14-1: The display of MI and TI on the screen
1. Title bar
2. MI
3. TI