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Calibrating and adjusting the AEC
11 - 7
Siemens AG
Register 3
SPB7-230.033.11
Page 7 of 22
M1000/3000 Nova
Medical Solutions
Rev. 06
05.06
CS PS SP
Installation and Start-Up
Correction of the measured Optical Density (O.D.)
11
Due to variations in the developing conditions (see also section "Normal developing condi-
tions") the measured optical density of one specific image might not correspond to the
adjusted optical density (sensitivity setting). Therefore the optical density has to be cor-
rected for the variations in the developing conditions.
Procedure
11
•
- For grid/no grid: cover the area far from the chestwall side with metal plate (part no.
65 52 728).
- For magnification: place metal plate (part no. 65 61 026)
inside
the magnification table
as close as possible to the cassette to prevent scattered radiation and cover the area far
from the chestwall side.
•
Develop all films with a sensitometer strip on the part that was covered by the metal plate
(part no. 65 52 728 or 65 61 062).
•
Measure the optical density in two places: OD
m
(as described in Fig. 2) and OD
strip
(on
the sensitometer strip).
•
Calculate the corrected O.D. as follows:
OD
corr
= OD
m
+ (OD
strip_ref
- OD
strip
)
Normal developing conditions
11
When measuring the O.D., it is essential that the working conditions are as close to nor-
mal as possible. There are several parameters that may effect the results:
•
Temperature of developer and dryer
•
Feeding and developing speed
•
Replenishing speed of developer and fixer (liquids)
If possible, develop the film among other films when the developer is warm and stabilized.
This correction has to be made for
1. fine setting of sensitivity correction
2. setting of sensitivity
3. final testing.
OD
m
The measured optical density in the mea-
suring point, see Fig. 2.
OD
corr
The corrected optical density.
OD
strip
The O.D. in the step of the sensitometer
strip
closest
to the O.D. of the measuring
point.
OD
strip_ref
The measured OD
strip
on first film exposed
under normal developing conditions shall
be used as OD
strip_ref
.
NOTE