GE CT-9800

GE MEDICAL SYSTEMS CT 9800 QUICK SYSTEM
Rev. 16 Direction 18000
6-9-11
9-4 Plane Of Rotation (Requires a cold tube)
This procedure checks and adjusts the plane of rotation of the X-Ray fan beam so that it is perpendicular to the
axis of gantry rotation within 0.010” (0.25mm) across the largest reconstruction circle (48cm). This procedure
offsets the fan beam to account for the slight shift that occurs with heating of the X-Ray tube.
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.
NOTE: An accurate POR is fundamental in the tube replacement process. Failure to do an accurate POR
will result in faint rings in 3.0 and 1.5 mm bone algorithm reconstructions
1. Place the phantom holder and 48cm PE phantom on the cradle.
2. Tape a type 52 film at 3:00 o’clock position on the outside edge of the 48cm phantom, so that the film
projects into the gantry as in Illustration 6-9-9. The side of the film marked “This side toward lens” should be
towards isocenter. When exposed and developed, the film will show the alignment of the two beams with the
table at the left as viewed from the X-Ray tube at the 3:00 o’clock position.
3. Turn on the alignment lights, advance the cradle and position the film for an exposure near the image center
mark on the film pack.
4. Use (DC) Data Collection (within CTDS) and perform an axial scan (X-Ray) ON with the following parameters:
This should be CTDS default scan #1; “POR 10MM”
FILTER APERTURE KVP mA SCAN SPEED X-Ray ON X-Ray OFF
Body 10mm 80 40 4 sec. 0 360
ILLUSTRATION 6-9-9 ILLUSTRATION 6-9-10 A ILLUSTRATION 6-9-10 B
BAD P.O.R. GOOD P.O.R.