GE CT-9800

GE MEDICAL SYSTEMS CT 9800 QUICK SYSTEM
Rev. 16 Direction 18000
6-9A-20
This procedure aligns the tube focal spot with the detector center. Refer to Illustration 6-9A-13 for procedure flow
and perform the following calibration scan.
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. With nothing in the gantry, perform the following calibration scan: This should be CTDS default scan #5;
“ISOCENTER CAL”.
Enter CTDS
• (DC) Data Collection
• (9) Select Default
• (5) Default #5; “ISOCENTER CAL”
• (2) Offset Correct & Normalize
• (ISOCAL) Output Filename
• (CR) Run Description (Default)
• (CR) Enter to proceed.
Perform the calibration scan.
2. At the table
Install phantom holder to cradle
Locate 1/8” diam steel pin to phantom holder
• Suggest Craftsman #0 Phillips screwdriver secured with masking tape. Pin must be perpendicular to
scan plane.
• Use alignment lights to position the pin about 1.5” to the right and 1.5” above Isocenter.
• Turn alignment lights off
NOTE: Always use a 1/8 inch pin when doing ISO alignment or an ISO alignment check. The result of using
a larger diameter pin will cause shadowing over more detector channels than the alignment program
is capable of calculating accurately. The program will report an inaccurate channel number and
cause the alignment to be in error by almost 20 times the spec of +/- .02 channels.
3. Scan pin in space. This should be CTDS default scan #6; “ISOCENTER SCAN”.
Enter CTDS
• (DC) Data collection
• (9) Select Default
• (6) Default #6; “ISOCENTER SCAN”
• (N) Cal Phantom Type
• (N) Reduced F.O.V. (Default)
• (1) Number of Scans
• (ISO) Run Description
• (CR) Enter to proceed
Perform the scan and record the exam number assigned. Exit scan program.