P/N 9-500-0255 4-23
Service Manual
Chapter 4: Calibrations and Performance Checks
Automatic Exposure Control System Calibration
Table 4-7: AEC Performance Worksheet—Large Focal Spot, Rh Filter
5.10 Initial Calibration—Small Focal Spot (Mo)
This procedure will make gain and offset adjustments to the automatic exposure control
system for small focal spot exposures. Exposures used to adjust the offset must be taken
between 65 mAs and 130 mAs, and exposures used to adjust the gain must be taken
between 6 mAs and 14 mAs. Always take sample exposures, then adjust the amount of
attenuation to achieve the proper mAs before making gain or offset adjustments.
Note… Before starting this procedure, select the small focal spot, then set the Gain
and Offset values to the values used at 25 kV for the Large Focal spot.
1. Remove the Bucky device and install the Magnification Table. Always use the same cas-
sette for all AEC calibrations.
2. Set the unit for an exposure at 25 kV, Small focal spot, Mo filter, Mag Auto-Time.
3. Place 2.0 cm of BR-12 or PMMA on the breast platform, centered laterally, and extend-
ing 1.0 cm over the chest wall edge. Place the AEC detector in the position closest to the
chest wall.
4. Place the AEC detector in the position closest to the chest wall. Take an exposure,
develop the film, then measure the optical density (OD).
Note… Always measure the Optical Density with the lower edge of the film flush
with the front edge of the Densitometer and centered side-to-side
(approximately 5.0 cm into film plane).
5. Make Gain adjustments to calibrate the Optical Density to the value requested by the
customer. Increase the Gain value if the density is too high. To maintain mAs require-
Large Focal Spot
0.025 mm Rhodium Filter
SRL 2000 Bucky/
Paddle/BR-12
KODAK MIN-R-2000
Film/Cassette
Gain - Lower Thickness = 40 to
80 mAs
Offset - Higher Thickness = 240
to 350 mAs
kV mA Recommended
Thickness
mAs OD Gain/Offset Max/-1.0 cm mAs OD
28 100 4.5 cm G=
6.0 cm
28 100 7.0 cm O=
29 100 4.5 cm G=
6.5 cm
29 100 7.5 cm O=
30 100 5.0 cm G=
7.0 cm
30 100 8.0 cm O=
31 100 5.0 cm G=
7.0 cm
31 100 8.0 cm O=
32 100 5.5 cm G=
7.5 cm
32 100 8.5 cm O=
Note… Adjust thickness as necessary to achieve desired results.
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