ATS 535-H, Руководство пользователя

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AXIAL AND LATERAL RESOLUTION
Description and Reason For Testing
Resolution is the minimum reflector 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 findings.
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 condition of the transducer.
Resolution perpendicular to the axis of the sound beam is termed Lateral Resolution. Lateral Resolution
is dependent upon the beam width, increased beam width will reduce the Lateral Resolution.
Testing Procedure
In the Model 535-H scan surface #1 and #3 are used to evaluate axial resolution at depths of 5.5 and 11
cm. To evaluate lateral resolution, scan surfaces #2 and #4 are used, at depths of 4.5 and 16.5 cm.
The interval spacing of the line targets are 5, 4, 3, 3, and 1 mm. Each target is spaced 1 mm laterally to
avoid over shadowing of the adjacent targets.
1. Place the phantom on a clean, flat 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, fill the
scanning well slowly to avoid introduction of air bubbles.
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 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 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
specification drawing). Obtain a hard copy of the display.
6. Document all observations made on the quality assurance record.
7. Position the phantom with scan surface #3 ready for use. Repeat steps 2-5.
8. Repeat steps 1-6 for scan surfaces #2 and #4 to obtain measurements of the lateral resolution.
Results
The system's ability to resolve the array targets at all four depths should remain consistent from week to
week when using the same instrument settings and the Model 535-H phantom. Compare the test results
obtained with a baseline or previous test. If the current image demonstrates changes in the system's
ability to resolve these targets, corrective action should be considered.
FOCAL ZONE
Description and Reason For Testing
The focal zone is the region surrounding the focal point in which the intensity and the lateral resolution is
the greatest. Clinically, structures examined within the focal zone will provide the best diagnostic
information obtainable. The focal zone can be affected by changes in the pulsing/receiving section of the
imaging system or damage to the transducer.