Hologic DISCOVERY A, Technical Manual

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Discovery QDR Series Technical Manual
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insure that the coefficient of variation for absolute radiation is less than 4%. The plot
screen does not readily display the coefficient of variation for absolute radiation.
You must use the formula:
coefficient of variation for absolute radiation = standard deviation (SD) x.0028
Therefore:
To do this:
1. If necessary, restart the Discovery software in Service Mode.
2. Perform 10 array spine scans (using
Utilities|Service Utilities|Autoscan
from the Discovery Main Menu screen).
3. Analyze the first scan manually.
4. Include the analyzed Scans into the QC database. On the APEX main screen,
select
QC>QC data Management>Select Scans.
In the Excluded Scans
pane, select (highlight) the ten scans just analyzed and click Include Scans. Click
OK when done.
5. Put the results in the QC database (if you have not already done so).
6. From the Discovery Main Menu, select
QC|QC Data Management|Plot
. Use
a start and end date that will only select the scans that you have just completed.
7. Select QC Parameter to Plot, HiA, and Plot.
8. Plot the data for the 10 scans in step 1.
9. Assure that the SD is 3 or less.
10. Repeat for “LoA” by repeating steps 4-7. This result must also be 3 or less.
Note: Enter this information into the Radiation Measurement Report (see example on
page 3-70).
3.5.18 Table Top Radiographic Uniformity (A, W and Wi)
This procedure verifies proper X-Ray beam alignment and the uniformity of the X-Ray
transparency of entire tabletop (for Discovery A, W and Wi models).
1. If necessary, restart the Discovery software in Service Mode.
2. Type WBAIRQC in the Patient Biography. Enter the serial number of the unit in
the Patient ID field.
Make sure that only the pad is on the table. Clear the table of anything else.
If… Then…
the Standard Deviation (SD) for both High Air
(HiA) and Low Air (LoA) is less than or equal to
14, the coefficient of variation for absolute radiation is
less than 4%.