GE LOGIQ 500 Advanced Reference Manual page 191

Acoustic output (cont'd)
Operator intervention
LOGIQ 500 Advanced Reference Manual
2276614–100 Rev. 0
Tissue heating is more of a concern when the acoustic beam is
stationary, so the thermal index is likely to increase when
Doppler or M-Modes are selected. The influence of specific
operator controls on acoustic output is described along with the
functional purpose of the control throughout the user manual
and a summary is provided in Safety .
The operator now has easy access to the status of acoustic
output and, when combined with the knowledge of tissue
characteristics and beam location, the risk of potential bioeffect
can be readily assessed. This display conforms to the
AIUM/NEMA Output Display Standard [1] for ultrasound
imaging equipment.
When conditions indicate a potential for harmful bioeffect, the
operator should take action promptly to reduce the risk by
changing equipment settings or altering procedural techniques:
S
Output display index values much greater than 1.0
represent an increased risk for tissues in particular beam
locations. The potential for heating will normally only occur
near the surface or at the focus, while the potential for
cavitation is reduced away from the focus. Selecting
non-scan operating modes such as PW or CW Doppler and
M-Mode will significantly increase the thermal index
because the beam is stationary.
S
Optimize gain and other image enhancement features
before increasing the acoustic output control or other
equipment controls that significantly affect the output level.
Become thoroughly familiar with all controls that affect
output and observe the output display for results. Controls
affecting output are described throughout the user manual.
Bioeffects
6–7