GE CT-9800

GE MEDICAL SYSTEMS CT 9800 QUICK SYSTEM
Rev. 19 Direction 18000
6-9A-14B
detector type XENON HILIGHT
low limit 115,000 80,000 counts
high limit 158,000 185,000 counts
channels 2-3 2,3
and 734-736 748-750
Note: Channel 1 will, have an output approximately 55% to 60% of the 5 reference channel average.
If the average of the 5 reference channels is LOW, then the tube or detector should be replaced because system
performance will be compromised.
If the average of the 5 reference channels is HIGH, then the tube should be replaced because the tube output is
excessive.
Note: HILIGHT detectors should not be replaced for ’low output’ until the DOSE MEASUREMENT has been
completed. (Refer to the CT GUIDE to Trouble-Shooting LOW SIGNAL OUTPUT from SN T-1205).
Notes:
The test is provided as an early staging or trouble shooting tool to verify the integrity of the data channel signal
paths. This is accomplished by collecting data with a uniform x-ray flux across the detector and confirming that all
data channels are functioning normally. A range of DAS count limits are provided as a guideline, but there may be
cases where an unusual channel to channel variation but within the range limits could be a clue to a potential
problem. To augment the numerical guidelines, a plot of the output file to visually inspect the data for suspect
channel patterns is a suggested practice.
9A-7-2 DATA Channel Output Verification
Complete the previous section. Then:
[CANCEL] read the means of non-reference channels
[CANCEL] return to the main menu
The system passes the DATA channel output test if the ’means’ lie between the following limits.
(where: ’means’ = ’signal count’ view average)
detector type XENON HILIGHT
channels all center 1mm outer 2mm
low limit 40% of ’reference’ 25,000 60,000 counts
high limit 60% of ’reference’ 157,000 230,000 counts
channels 4-730 65-688 4-64, 689-747
The data may also be plotted for visual perusal as follows:
R
AN (CR) Analysis
D (CR) Diagnostic Data functions
1 (CR) type/print
E (CR) (CR) EDIT, default, default
P (CR) plot
1 (CR) first channel
750 (CR) last channel
M (CR) means or std. dev.
(CR) (CR) default 2 more
A (CR) erase
(CR) continue = PLOT
Note: COMPARE to absolute limits, lists channels ’OUTSIDE’ these limits
This may be used to verify that there is nothing partially blocking any channels.