GE Healthcare Brivo XR118 Service Manual page 136

GE H
EALTHCARE
D 5461425-8EN, R
IRECTION
1.4 The use of Collimator tape (Note the difference between SID and OID)
In the calibration, you need to use collimator tape to measure SID. In the case to measure SID, you
need to consider the effect of OID (Object Image distance)
To measure the SID when use wall stand, you can use the collimator tape to measure the distance
from tube to patient barrier on Wall Stand and record it as length A. Then the SID = length A + WS
OID. WS OID=40mm.
To measure the SID when use table, you can use the collimator tape to measure the distance from
tube to table top on Wall Stand and record it as length B. Then the SID = length B + Table OID.
Table OID=50mm.
1.5 Dose control for target system
1.) Set up the x-ray technique
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Note:
2.) Start an exam to take an exposure.
3.) Open this raw image, use the annotation tool to add a ellipse in the center of the image.
4.) When you do gain calibration, you can refer this value.
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EVISION
Tape Measure to Set SID = 150cm, KVP=80, mA=50 or larger, mAs=5(It may be necessary to
place the detector on the floor to achieve 150 cm SID).
Detent the tube to center of the detector.
Fully open collimator blades.
- Above suggested mAs is based on the high frequency generator.
- For power frequency case, you may increase mAs to 15 to try firstly.
Record the mean value displayed on the right bottom of the image.
Based on this value to adjust the mAs to take another exposure until the mean value in raw
image in range from 8000 to 12000.
Record the final mAs after completing the step 3.
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RIVO ERVICE ANUAL