ATS 535-H, Руководство пользователя

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DEAD ZONE
Description and Reason For Testing
The dead zone is the distance from the front face of the transducer to the first identifiable echo at the
phantom/patient interface. In the region of the dead zone no clinical data can be collected. The dead zone
occurs because an imaging system cannot send and receive data at the same time. The depth of the
dead zone depends upon the frequency and performance of the transducer and the pulsing/receiving
section of the system.
Testing Procedure
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.
3. Adjust the instrument settings (TGC, output, etc.) to establish baseline values for "normal"
liver scanning. If the bottom of the phantom is visualized, adjust the gain settings until the
image goes entirely black. Record these settings on the quality assurance record. These
setting should be used for subsequent testing.
4. Scan the phantom until the dead zone target group is clearly displayed. Freeze this image.
5. This group is composed of 9 line targets. The first target is positioned 2 mm below the scan
surface. Subsequent targets are spaced 1 mm apart, to a depth of 10 mm.
6. Using the electronic calipers, measure the distance between the first target imaged and the
echo produced by the scan surface. The resulting value will be the depth of the dead zone.
7. Document the depth measurement on the quality assurance record.
Results
If the depth of the dead zone is greater than 10.0 mm, corrective action should be considered by the
individual Ultrasound Department.
VERTICAL MEASUREMENT CALIBRATION
Description and Reason For Testing
Vertical distance measurements are obtained along the axis of the sound beam. Proper diagnosis is
dependent upon accurate representation of the size, depth and volume of structures being examined.
Most imaging systems use depth markers and/or electronic calipers to obtain these measurements. The
vertical line targets are scanned and a distance measurement obtained. The resulting measurement is
then compared to the known distance between the line targets in the phantom. The accuracy of vertical
distance measurements is dependent upon the integrity of the timing circuitry of the imaging system.
Testing Procedure
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 the image
goes entirely black. Record these settings on the quality assurance record. These setting
should be used for subsequent testing.
4. Position the transducer over the vertical group of line targets until a clear image is obtained.
Freeze the display.