Dose Rate At The Image Intensifier Input; Deviation Of The Dose Rate Value From The Set Values At The Image Intensifier Input - Siemens ARCADIS Varic Operator's Manual

Technical Data
Deviation calculation
Setting the dose rate
value
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Dose rate at the image intensifier input

The dose rate is factory-set between 0.11 µGy/s and 0.44 µGy/s depending on
the I.I. format, measured behind the scattered radiation grid at the I.I. input.
Using a test phantom, the dose rate was set in a kV range between 70 kV
and 80 kV. The iris diaphragm is maximally opened for this.
Deviation of the dose rate value from the set values at the
image intensifier input
Depending on the examined object, different fluoroscopy data (kV, mA) are set.
The sensitivity of the image intensifier is influenced by beam quality (kV).
As a consequence, different dose rates may result at the I.I. input screen for the
same luminance at the I.I. output screen.
When examining a patient in fluoroscopy mode, additional scatter radiation val-
ues are produced in comparison to the phantom values, affecting the dose rate
at the image intensifier input.
Using K as a correction value, (refer to diagram), the approximate deviation value
from the set dose rate can be calculated.
K
2,5
2
1,4
1,0
70
50 60
Calculation example: With 70 kV the correction value is 1.4. That is, if the set dose
rate value is 0.22 µGy/s, the actual value is approx. 0.22 µGy/s x 1.4 = 0.308 µGy/s.
If desired, the preferential position for the dose rate can be reprogrammed.
80 90 100 110
120 130
kV
Operator Manual
SPR2-310.620.30.02.02
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