Siemens AG SPR8-230.831.30.03.02 MOBILETT XP Digital
11.05 CS SD 24
Inspection and maintenance 65
Page 65 of 74
Medical Solutions
3.8 Reproducibility test (USA only)
Requirement:
The coefficient of variation for the radiation dose for any combination of exposure param-
eters does not exceed 0.045. This requires operation at the line voltage compliant with
Siemens specifications.
NOTE
In the following test, 10 sequential exposures are taken within one
hour.
The exposure parameters should be briefly set to different values
following each measurement.
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
• Initiate 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
Coefficient of variation C is determined for a series of 10 dose measurements with the fol-
lowing formula:
Fig. 31:
s = Standard deviation resulting from the measurements
_
x = Average measurement of the series
x
i
= i. measurement of series
n = Number of individual measurements in series
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