Reproducibility Test - Siemens MOBILETT XP Digital Installation And Startup

48

Reproducibility test

Requirement:
•
The coefficient of variation for the radiation dose for any combination of exposure pa-
rameters does not exceed 0.045. This requires operation at the line voltage compliant
with Siemens specifications.
NOTE
Required measuring instrument:
- Dosimeter
Procedure:
•
After switching the system on, wait until its temperature has stabilized. The unit is ready
for these measurements after 15 minutes.
•
X
Release the number of exposures with the specified exposure data:
- 85 kV, 1.0 mAs, 10 exposures.
•
Measure the dose for each exposure.
•
Reset the display prior to each new measurement.
Calculations: Coefficient of variation C
•
For a series of 10 dose measurements, coefficient of variation C is determined using
the following formula:
Fig. 21:
s
_
x
x
i
n
Coefficient of variation C must be ≤ 0.045.
Example for determining coefficient of variation C:
Step 1)
•
10 exposures with recorded measured values (fictitious values).
MOBILETT XP Digital
In the following test, 10 sequential exposures are taken within one
hour.
The exposure parameters should be temporarily set to different
values following each measurement.
= Standard deviation resulting from the measurements
= Average measured value of series
= i. measured value of series
= Number of individual measurements in series
SPR8-230.814.30.03.02
11.05
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