Discovery QDR Series Technical Manual
4-33
3. Perform one Whole Body air scan (a scan with nothing on the table). Do NOT
interrupt the scan for any reason. Select Exit Exam when complete. Do not ana-
lyze the scan you just performed.
4. From the Discovery Main Menu screen, select Utilities|Service Utili-
ties|Table Top Radiographic Uniformity.
5. Select the Whole Body scan and click the Next> button.
6. Table Top Radiographic Uniformity results tabs are now displayed. Select the
Low Air Tab.
7. If the Global Stats S.D. (2) is less than 2.0, the instrument is properly
aligned. Print a copy of the test results and include it with the other paperwork
being returned to Hologic.
If the Global Stats S.D. is greater than or equal to 2.0, then the machine is not aligned
properly. Check the following:
• If the image appears "streaky" or "banded", check for loose wires or other debris
between the table and the tank.
• Check the “Aperture Calibration ” on page 4-9.
• Check AC Line voltage.
• Check +/- 15V Power Supply
• Check “Detector Flattening ” on page 4-29.
• Re-run daily QC (see the Discovery User's Guide).
After realignment, repeat the Table Top Radiographic Uniformity test. If the global S.D. is
less than 2.0, print a copy of the test results and include it with the other paperwork being
returned to Hologic.
If the global S.D. if equal or greater than 2.0, the non-uniformity may be attributed to the
table itself. If so, continue with this procedure. Make sure that the machine has body
composition loaded. If it does, then follow the appropriate procedure in 4.12.1 or 4.12.2.
4.12.1 Instruments using Body Composition Analysis (BCA)
Instrument performing BCA must have a global S.D. of less than 2.0. If the realignment
and recalibration procedures above have been performed and an S.D. of less than 2.0
cannot be obtained, then the tabletop must be replaced.
Note: Archive the airscans you have acquired and either e-mail or FEDEX them to a
Technical Support Specialist at Hologic headquarters for final evaluation.
4.12.2 Instruments using BMD Whole Body Analysis
Instruments using only BMD Whole Body measurements can tolerate a larger S.D. If the
global S.D. is less than 3.0, then you are done. If the S.D. is equal or greater then 3.0, then
the tabletop must be replaced.
Note: Archive the airscans you have acquired and either e-mail or FEDEX them to a
Technical Support Specialist at Hologic headquarters for final evaluation.
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