16
Appendix 1 – Ion chamber energy correction factors
for Cu
An investigation has been conducted to cover the energy dependence of RTI’s
solid state detectors compared to presently used ion chambers when the
detectors are used on vascular systems (when the beam is filtered by cupper).
The result explains why the X-ray systems sometimes fail the pass/fail criteria
when using the RTI detectors.
An example:
When comparing the Dose Probe from RTI to a Radcal 180 cc at RQC 5 (70 kV
and 2.83 mm Al + 1.5 mm Cu) a relative difference of 8 % (1.02 - 0.94) can be
read out from the graph above. An additional 6 % is added due to the scattered
radiation that is not registered by the Dose Probe. In this case, when comparing
the two detectors, the reading from the ion chamber will be 14 % higher than the
reading from the Dose Probe.
Piranha Dose Probe Holder User’s Manual
2009-09/1.0B
65
70
75
80
85
90
95
100
105
110
0,9
0,95
1
1,05
Energy correction RQC 5 & 8 normalized to RQR 5.
Measured against a NE2530, calibrated 2009-02-23 at PTB for the RQC beam qualities.
PDP
Radcal 60
Radcal 180
Keithley 15
Keithley 150
R100B
kV
N
or
m
al
ize
d
to
R
Q
R
5