tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice
small aNimal abDomiNal UlTrasoNograPhy Peer reviewed
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signifies the direction of the US beam relative to
the image. Each machine's marker is different,
but convention states that, when the transducer is
oriented parallel to the long axis of the dog or cat,
the marker should be positioned cranially.
7. Gain Adjustment
Use the gain adjustment and TGC or DGC controls
to adjust overall image brightness (Figure 3).
However, remember that this is a postprocessing
technique that increases the overall whiteness of
the screen. It has no effect on the production,
transmission, or processing of US waves.
When using the TGC or DGC settings (Figure
4 ): Use the mid-range as a starting point for setup;
then adjust the sliders from a straight vertical
FIGURE 3. Three different images from a 0.5
dB US phantom. In A, the overall gain setting
is normal (usually around 60%). In B, the overall
gain setting is too low resulting in an overall
hypoechoic image (gain setting at 50%). In C,
the overall gain setting is too high resulting in
an overall hyperechoic image (gain setting at
78%). These gain values are specifc to your
US; therefore, ensure that the overall gain is
adjusted appropriately for your machine.
FIGURE 4. Image manipulation using the TGC
or DGC curves. In A, the near feld TGC sliders
have been moved too far to the right resulting
in a "white" near feld. In B, the near feld TGC
sliders have been backed off too much, so that
the overall echogenicity of the phantom does
not appear uniform and is too dark close to the
transducer. In C, the sliders specifc to the 1, 3,
and 4 cm distance markers have been set to the
far left, resulting in no image at all.
A
B
C
A
B
C