KermaX-plus
®
Chamber | Quality Assurance | 33
6.2.2. Calibration Check procedure
1. Switching on the X-ray machine, the KermaX-plus
®
system is switched on simultaneously
(depending on the wiring/connecting of the system), and is able to measure after about 20 seconds.
Only after the specified stabilization time period, the system measures within the specifications
2. Perform a stability check as described in previous chapter 6.1 System Test (Stability Check).
3. Irradiated field size parameters should be set at the control console resp. collimator device. It is
recommended to collimate an average size of the irradiated field of the active chamber surface.
4. Determine the reference field area. It is the size of the surface area on the reference point level (e.g.
table top, grid assembly) which is orthogonal to the central beam direction. This is the location of the
reference dosimeter.
For a more accurate field size determination, it is recommended to exposure an X-ray film or a
fluoroscopic screen.
If an iris shutters / collimators are used, the area formula for regular polygons shall be applied.
5. Put the reference dosimeter on the reference point level.
6. Exposure parameters should be set at the control console and an X-ray exposure released. In order
to make a valid comparison with the manufacturer’s calibration (see Table above, reference
conditions), the radiograph must be made using 100 kV.
7. After the exposure has been released, read and take note of the results displayed on both measuring
devices.
e.g. reference dosimeter display: 2703 µGy
KermaX-plus
®
: 33.90 µGym²
8. Comparison of the reference dose area product (reference dose x reference field area) and KermaX-
plus
®
measured dose area product:
μ
μ
KermaX-plus
®
value which are about 4.51% higher which is still within tolerance. The manufacturer’s
tolerance is ± 5%.
IMPORTANT NOTICE
AIR DENSITY CORRECTION
Due to variable reference sensors, air density correction for the chamber and / or
the reference detector may be indicated for best accurateness (section 7 Air
Density Correction).
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