GE CT-9800

GE MEDICAL SYSTEMS CT 9800 QUICK SYSTEM
Rev. 12 Direction 18000
6-9A-24
4. Review CBF projection
• CBF must equal Isocenter ± 0.20 channels.
• If OK, this procedure is done, otherwise proceed to Step 5.
5. At gantry
• Check for 0° tilt and table at load home normal
• Remove side covers
• Turn off scan drive switch
• Flip over top cover
• Swing out front cover
• Rotate gantry to 270° (Collimator at 3:00 O’clock).
• Install dial indicator and shift collimator the specified amount per Step 3. Refer to Section 9A-2-2 for
collimator positioning.
• Close front cover
• Arm scan drive switch
6. Call Data Collection (DC) program
• (DC) Automatic down load
• Repeat CBF scan, Step 2
9A-9 System Sag
The sag program measures the change in alignment during a rotating scan. It reports the peak amplitude
difference in channel numbers as well as the hysteresis or difference in channel numbers between first and last
views of a scan.
Refer to Illustration 6-9A-15 for the procedure flow.
1. Use the calibration scan ISOCAL from Section 9A-7, Step 1.
2. Use the CBF scan from Section 9A-8, Step 2.
3 Analyze the SAG run using the alignment program.
Enter CTDS
• (AL) Alignment
• (3 ) SAG
• (xx) Select Exam # recorded in step 2 for CBF.
• (yy) Enter ISOCAL for calibration filename.
The program will calculate and display the maximum channel difference, the azimuthal location of the
channel difference, and the difference between first and last views in channels. Record the information
and then exit the Alignment program.