Quantum ODYSSEY HF Series, Service Manual

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Chapter 3 Calibration
Revision W HF Series X-ray Generators - Service Manual
3-60
Quantum Medical Imaging, LLC
Reciprocity Calibration Procedure
The Reciprocity Calibration Screen, shown below, is used to establish rec-
iprocity failure compensation. The image receptor and chamber field set-
tings remain the same as those used in the AEC Optical Density
procedure.
This procedure requires three exposures; the first at approximately 100-
200 milliseconds, the second at approximately one second and the third
at approximately three seconds. The amount of acrylic specified in the
following steps (i.e., 15 CM) should give appropriate exposure times for
40 inch SID, 400 speed film. However, the amount of acrylic may need to
be adjusted for other film/screen combinations to compensate for differ-
ences in SID and/or film speed. For example, to calibrate at 72 inch SID,
the amount of acrylic would be reduced to 10 CM.
Figure 3-40. Reciprocity Calibration Screen
Proceed as follows:
1. Place a film cassette in the tray and collimate down to film size.
2. Place 15 cm of acrylic in the X-ray beam.
3. Verify the receptor in which the film cassette is inserted is selected as
indicated on the AEC Reciprocity Calibration screen.
4. Take an exposure at the setting indicated in the center display box
(i.e., 50 kVp, 400L mA).
5. Develop the film and measure the optical density using a calibrated
densitometer.
6. Press the up or down key located next to the Measured OD field
until the optical density value displayed equals the measured optical
density value (the Measured OD up arrow key increases the optical
density value and the Measured OD down arrow key decreases the
optical density value).
NOTE
Reciprocity
Calibration
must be
performed for
each film/
screen
combination
used with
system.
BASE
OPTICAL
DENSITY
SETTING
MEASURED
OPTICAL
DENSITY
KEYS
ENTER OD
MEASUREMENT
KEY