!
Gray Scale & Displayed Dynamic Range
Description and Reason for Testing
Gray scale or gray scale processing uses the amplitude of the echoes received to vary the degree of
brightness of the displayed image. The adjustment of the echo signal required to go from a just
noticeable (low gray scale level) echo to the maximum echo brightness is referred to as the displayed
dynamic range. Clinically, gray scale processing and displayed dynamic range allow echoes of varying
degrees of amplitude to be displayed in the same image.
Test Procedure
1. Place the phantom on a clean, flat surface with the scan surface positioned for use.
2. Apply an adequate amount of low viscosity gel to the scan surface.
3. Adjust the instrument settings (TGC, output, etc) to establish baseline values for “normal” liver
scanning. If the bottom of the phantom is seen, adjust the gain setting until the image goes entirely
black. Record these settings on the quality assurance record. These settings should be used for
subsequent testing.
4. Position the transducer over the gray scale target group until a clear image is obtained.
5. Freeze image and obtain a hard copy.
6. Examine the image. The targets should appear circular in shape, with clear sharp edges and vary in
the degree of brightness ranging from low to high levels of contrast. The presence or absence of any
shadowing behind the structures should be noted.
7. All findings should be documented on the quality assurance record.
Results
This target group varies in echogenicity and provides a good indication of the performance of the gray
scale processing and displayed dynamic range. The test should be compared with a baseline test using
the same instrument settings, to determine if any change in the characteristics of the target group has
occurred with time. If changes are noted, they should be investigated.
