GE LOGIQ 200 Quality Assurance Manual page 84

GE MEDICAL SYSTEMS
REV 1
4-2 Probe Q/A – System Performance Test (cont'd)
4. Maximum Penetration – Obtain an image that displays the maximum penetration for the probe under
test.
TERMS: Penetration is expressed in centimeters of displayed imaged depth. It is probe dependent, and
heavily dependent on the FP Settings of Transmit Power, TGC (DGC) and Master Gain (2D Gain). It
is somewhat dependent on settings for Pre-Processing and Post Processing. On most systems these
parameters are reported on the screen and should be recorded on your test film for reproducibility.
ACQUISITION: For the Probe under Test, Adjust Transmit Power to Maximum – Adjust FOV or Depth
to the maximum applicable for the probe under test. Adjust Master Gain (2D Gain) and TGC (DGC)
to the point where no more of the tissue equivalent material is visible. Once this image is acquired,
Freeze the Image.
Make a measurement from the skin line to the point furthermost in depth, where tissue echoes
disappear. Choice of this point may appear to be arbitrary, but there will be a point where the image
falls off to nothing but the phantom pins, and perhaps some background noise. If the image field is still
filled with echoes, adjust the displayed depth higher, and rescan.
Make a hard copy of this measurement, along with any changes to image controls not noted on the
screen.
5. System Noise Level – Determine the maximum TGC / Master Gain combination that produces a clean
image.
TERMS: Noise and Artifact can come from many sources, and can indicate system problems. At the
same time, Ultrasound receivers are responsible for providing broad and narrow band amplification for
returning echoes in the range of a few micro-volts. By choosing the correct application of an individual
probe, and the best system settings for the application, the technician is capable of maximizing the
ratio of true signal to noise.
However, Image degradation can occur due excess noise that can come from many sources. While
this goes beyond the scope of this document, Noise level verification on a working system can provide
troubleshooting information for problems that may occur at a later date. For example, if your last PM
records indicated a noise free scan at MID range on the gain controls, and the image now fills with noise
at 25% of maximum, a problem is indicated.
ACQUISITION: Wipe all the gel from the probe face, and set the probe in its holder. With transmit power
at a fixed value, adjust the overall gain, until the far field image (beyond 3cm) begins to fill with noise.
Reduce the overall gain until the last of those noise "speckles" disappear. Note the gain level on film
and make a hard copy.
6. Cystic Structures – Record and Image that captures the smallest visible cystic structure for the probe
under Test.
TERMS: Depending on your phantom there will be rows or several rows of cystic structures (Clear) of
varying sizes. While these structures are physically "echo-free", there are conditions in which those
cysts may not appear clear. The sources for those artifacts are beyond the scope of this document,
but a good test film on a working system can provide troubleshooting information, and is a good indicator
of system performance.
ACQUISITION: For the probe under test, adjust the system gain, TGC, Transmit Power and Focus, to
produce a uniform image of the material surrounding the cystic structures. Use the ZOOM controls and
change the display depth to help visualize this . The goal is to try to demonstrate on hard copy the
minimum visible cyst that is clear.
ULTRASOUND QUALITY ASSURANCE REFERENCE MANUAL
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