Cirs ATS539 - Axial and Lateral Resolution Testing

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AXIAL AND LATERAL RESOLUTION TESTING
Resolution is the minimum reector separation between two closely spaced objects
which can be imaged separately. If a system has poor resolution capabilities, small
structures lying close to each other will appear as one image, causing improper
interpretation of the ultrasound ndings.
Resolution along the axis of the sound beam is referred to as Axial Resolution. Axial
Resolution is affected by the pulsing section of the imaging system and the condi-
tion of the transducer.
Resolution perpendicular to the axis of the sound beam is termed Lateral Resolu-
tion. Lateral Resolution is dependent upon the beam width, increased beam width
will reduce the Lateral Resolution.
The Model ATS539 provides four scanning surfaces to evaluate axial-lateral resolu-
tion at four given depths. Target locations in the phantom are referenced from the
center of the array at target point 5.
The line targets are spaced at 5.0, 4.0, 3.0, 2.0 and 1.0 mm intervals both axially
and laterally. The last point of the axial array target group is also the rst target point
in the lateral array group. Testing is performed as follows:
1. Place the phantom on a clean, at surface with scanning surface #1 positioned
for use.
2. Apply an adequate amount of low viscosity gel or water to the scan surface. If
water is used, ll the scanning well slowly to avoid introduction of air bubbles.
3. Adjust the instrument settings (TGC, output, etc.) to establish baseline values
for "normal" scanning. If the bottom of the phantom is seen, adjust the
gain settings until 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 axial-lateral resolution group of line targets on
the phantom until a clear image is obtained. Freeze this image.
5. Examine the image to determine if all of the line targets within the group are
clearly displayed as separate target points. Record the closest spaced target
points which can be imaged (refer to specication drawing). Obtain a hard
copy of the display.
6. Document all observations made on the quality assurance record.
7. Repeat the above procedure for the remaining three depths, using scanning
surfaces #2, #3, and #4.