GE LOGIQ 200 Quality Assurance Manual page 83

GE MEDICAL SYSTEMS
REV 1
4-2 Probe Q/A – System Performance Test (cont'd)
3. Measurement Accuracy – Obtain a measurement in both the Horizontal and Vertical Plane for the probe
under test.
TERMS: Every system provides some method of making measurements of linear distances in
ultrasound imaging. They are most often cursors, or calipers but are drawn OVER the U/S image in a
graphics memory plane, typically not in the ultrasound frame. While these two are typically coincident,
the processor making the measurement has to make certain assumptions. The most important one
being that 1540 meters/second is the AVERAGE speed of Ultrasound in human tissue. Keep in mind
that all instruments and all phantoms try to approximate this and may not generate exact results during
baseline tests.
ACQUISITION: The biggest variable is phantom temperature, which may demonstrate errors well in
excess of 10%. Adjust the displayed depth so that the maximum number of pins are visible in the same
axis as the probe. (vertical). Position the probe so that this row of dots is centered in the image. Freeze
this image and make a measurement from the pin closest to the probe to the last visible pin the displayed
field. Check this in the largest and the smallest displayed depth.
Rotate the phantom and repeat this on the horizontal plane. Due to errors induced by lateral resolution,
cursor placement must follow one of these two conventions: Inside to Inside, or leading edge to leading
edge. Make a hard copy of the measurements. Record the Phantom Temperature if available on the
PM/QA Checklist.
ULTRASOUND QUALITY ASSURANCE REFERENCE MANUAL
Illustration 4-2 Measurements
4-3
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