GE Alpha RT 32551 Installation Instructions Manual page 90

5 Setups, alignments and adjustments
3 Draw a line between the two points and read the corresponding
GAIN for the wanted optical density. Notice that the object is to find
the right gain, so the initial gain values do not have to be 1.00 and
0.90. If the correct gain is for example 1.08, more proper gain values
would be 1.00 and 1.10.
4 Alter the AEC Gain parameter 'g' in the service program #64 to obtain
the desired O.D. Diminishing 'g' will increase the O.D and vice versa.
5 Make one control exposure with semi-automatic (A) mode the clinical
kV (for example 26kV) Molybdenum filter @40 mmAcr and measure
the O.D. to check the adjustment. Make note of the exposure time for
the thickness compensation in the next section.
Exposure time _______________
CAUTION!
The AEC Gain 'g' parameter will affect all exposures regardless of used
filter or cassette holder.
6 Make three exposures with different phantom thicknesses (for
example 20mm, 40mm, 60mm to get short, medium and long
exposure time) and record the corresponding exposure times and
O.D:s. Recommended exposure times would be appr. 500ms, 1sec
and 2 second exposures respectively.
7 Use the clinical kV (for example 26kV) and semi-Auto (A) mode for all
exposures.
8 Mark the points to the O.D vs. exposure time graph. Draw a line
through the three points. They should form a horizontal line within
±0.15 O.D. If they do not, a thickness compensation will be required.
84 GE Healthcare 32551-IMG rev 6