GE CT-9800

GE MEDICAL SYSTEMS CT 9800 QUICK SYSTEM
Rev. 12 Direction 18000
6-9-14
9-5 Xenon Detector Beam On Window (Requires a cold tube)
This procedure checks and adjusts the position of the Xenon detector window so that it intercepts the entire width
of the X-Ray fan beam under worst case conditions. This procedure offsets the beam to account for the fan
beam shift toward the table that occurs with heating of the X-Ray tube. Therefore, beam centering at the detector
is set for -0.020” (-0.5mm) with the bias towards the gantry.
Refer to Illustration 6-9-11 for procedure flow.
➤ NOTE: Verify that the Tube Unit is “cold”; i.e., that it has had no more than 25 kilojoules exposure
[KV•mA•Sec/1000] within the last 30 minutes. Wait a minimum of 90 minutes from the completion of
a generator cal or other high technic exposures. Each exposure in this procedure adds 12.8kj of heat
to the tube, exposures should be made no faster than one every 5 minutes. Tube warm-up is not
recommended prior to this procedure.
1. Turn OFF the aximuth drive switch, and open the gantry front cover. Position the Detector at the 6:00
o’clock position.
2. If this is a newly installed detector, check that the detector is plumb at its’ three shock mount locations. It
is very important that the detector window be perfectly parallel to the gantry mounting surface before
continuing. Refer to Illustration 6-9-7 and check the 1.25 + 0.05” (31.75 + 1.27mm) dimension at both
ends and center of detector.
3. For early detectors without film slots, refer to Illustration 6-9-7 and remove the detector stiffner
(twenty #10-32 x 0.75” hex sock. cap screws).
4. With the detector at the 6:00 o’clock position, place three pieces of Polaroid film on the detector as
shown in Illustration 6-9-12. Orient the film with the side marked “This side toward lens” toward the
detector.
Butt the metal strip on the film up tightly against the rotating base of the gantry.
Make a small pencil mark on both sides of the film at the edge of the detector window closest to the
table.
5. Note the position of each film and remove all three pieces of film. Press heavily on the film and draw a
line on the film between the marks you made previously. This line must show on the film after it is
developed.
Place the films back in their positions on the detector. Verify the pencil marks of step 4 align with the
detector window. Secure with masking tape.