GE Logiq 500, User Manual

Page: 111 / 579

B–Mode
LOGIQ 500 Basic Users Manual
2233658–100 Rev. 0
5–10

Controls
Acoustic Output TGC
Description Allows for varying the power output of the
transmitted sound wave.
Follow the principle of “as low as reasonably
achievable” (ALARA) when scanning patients.
Always use the least amount of acoustic output
possible to obtain an optimal image.
Amplifies returning signals to
correct for the attenuation caused
by tissue at increasing depths.
The individual eight slide pots
correspond to the maximum
display depths for each probe.
Accessing/
Changing
NOTE: Always optimize gain before increasing
the acoustic output.
Clockwise rotation increases the acoustic output
level. Counterclockwise rotation decreases the
acoustic output level.
NOTE: Active slide pots backlight.
Benefits Optimizes the image quality thereby minimizing
exposure time to the patient while maximizing
penetration and echo return. Balances the image so that the
density of echoes is the same
throughout the image.
Values The mid-range acoustic output setting is factory
preset to be a reasonable setting for each type of
exam category.
Acoustic output levels are returned to the factory
preset value when changing the following:
S
Probe
S
Exam category
S
New patient
When display depth is changed,
TGC is rescaled to affect the new
depth range. Each TGC pot is
proportionally scaled across the
display depth range as shown in
Figure 5–5 on
5–11.
Affects on
Other Controls Acoustic output and gain interact to affect acoustic
output exposure. To a point, gain can be
increased to compensate for a reduction in
acoustic output. This minimizes acoustic output
exposure. In Zoom, the TGC adjusts
automatically if the “TGC Depth
Remap” preset, on Custom Display
page 10, is set to ON. Only the
TGC pots that affect the zoomed
region of interest will be lighted.
Bioeffects
Acoustic
Output
Hazard
Increasing acoustic output increases Mechanical
and Thermal Index values; decreasing acoustic
output decreases Mechanical and Thermal Index
values.
However, the improvement in image quality
should allow the patient exposure time to be
decreased.
CAUTION
Observe the effect of
CAUTION
Observe the effect of
acoustic output
adjustment on the TI/MI
display. Increasing the
index values to levels
greater than 1.0 should
take into account the
risk/benefit potential.