P33
Bone at Focus
(Cranial bone)
TIS at Surface
TIB
Bone at Surface
TIC
TIC
The TI informs the user about the conditions that exist that might lead to an increase in temperature at
the surface of the body, within the body tissue, or at the point of focus of the ultrasound beam on bone.
That is, the TI informs the user of the potential for temperature rise in body tissue. It is an estimate of
temperature increase in body tissue with specific properties. The actual amount of any temperature
rise is influenced by factors such as tissue type, vascularity, mode of operation, and others. The TI
should be used as a guide for implementing the ALARA principle. The bone thermal index (TIB) informs
the user about potential heating at or near the focus after the ultrasound beam has passed through
soft tissue or fluid; for example, at or near second- or third-trimester fetal bone. The cranial bone
thermal index (TIC) informs the user about the potential heating of bone at or near the surface; for
example, cranial bone. The soft tissue thermal index (TIS) informs the user about the potential for
heating within soft homogeneous tissue. You can choose to display TIS, TIC, or TIB.
Controls Affecting the Indices
B mode Controls
•
Transducer Frequency
Color
Controls
•
Color Sector Width: Narrower color sector width will increase color
frame rate and the TI will increase. The system may automatically
decrease pulse voltage to stay below the system maximum. A decrease
in pulse voltage will decrease the MI.
•
Color Sector Depth: Deeper color sector depth may automatically
decrease color frame rate or select a new color focal zone or color
pulse length. The TI will change due to the combination of these
effects. Generally, the TI will decrease with increased color sector
depth. MI will correspond to the MI of the dominant pulse type which
is a color pulse.
Other
Control Effects
•
B mode Depth: An increase in 2D depth will automatically decrease the
2D frame rate. This will decrease the TI. The system may also
automatically choose a deeper 2D focal depth. A change of focal depth
may change the MI. The MI displayed is that of the zone with the
largest MI value.
•
Application: Acoustic output defaults are set when you select an
application. Factory defaults vary with transducer, application, and
mode. Defaults have been chosen below the Intended use.
•
Imaging Mode Controls: When a new imaging mode is selected, both
the TI and MI may change to default settings. Each mode has a
