GE CT-9800

GE MEDICAL SYSTEMS CT 9800 QUICK SYSTEM
Rev. 19 Direction 18000
6-9A-14C
9A-7-3 Channel Output Failure action
Possible causes for channels falling outside the expected range could be:
Too low:
No Xray
open or shorted detector channels
open, shorted, or mis-registered flex
bad DAS channel.
Too high:
Shorted detector channel
shorted or mis-registered flex
bad DAS channel.
(Note: A short in the signal path could cause the DAS output to go high or low, depending on the front
end offset voltage polarity.)
Check that the prerequisites are OK
(Note that many of these are also part of the trouble-shooting GUIDE)
Troubleshoot and fix any faulty channels. Reference Direction 18008, RDCS manual.
Refer to the ”CT Guide to Trouble-Shooting LOW SIGNAL OUTPUT”
9A-7-4 Tube X-RAY OUTPUT (DOSE MEASUREMENT) check
The Tube X-RAY OUTPUT procedure for XENON detectors is the REFERENCE CHANNEL OUTPUT
Verification procedure previously outlined.
The following is a separate procedure for DOSE MEASUREMENT for HILIGHT detectors, which is essentially
one of the QA phantom image noise measurements. ( ref. OMB98901)
Center the QA phantom (water portion) in the aperture.
Axial Scan:
GE - QA head phantom
120KVP, 340 mas = 170 ma x 2 sec. scan ( published dose = 4 RADS )
10 mm. aperture, SMALL (25 cm FOV), 512x512 matrix
Peristaltic reconstruction option
References:
CT9800: manual, analyze with ”CTDS / QA PHANTOM”
Display the image of the QA phantom
Measure: QA PHANTOM, image noise, in 2cm x 2cm ROI,
at phantom center (51x51 pixels)
The DOSE measurement is LOW if the ’noise’ is less than 3.15
The DOSE measurement is HIGH if the ’noise’ exceeds 3.85
9A-7-5 DOSE MEASUREMENT Failure action
Check that the prerequisites are OK
Refer to the “CT Guide to Trouble-Shooting LOW SIGNAL OUTPUT”
If Dose Measurement is still LOW then tube output is excessive.
Replace the tube
If Dose Measurement is still HIGH and there are no measurable artifacts then tube output is low.
Replace the tube to improve system performance.
If Dose Measurement is still HIGH and there are still measurable artifacts then run the DATA CHANNEL
OUTPUT check.
If nothing is changed, or the problem still exists, then call the National Support Center.