Dose warning thresholds for electronic personal dosimeters
If you want to perform dose measurements with an active electronic personal dosimeter (APD) in the field of X-ray diagnostics, you have to set an alarm threshold for the dose rate (dose per time) (see circular of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety of 29.7.2011). The reason for this measure is that the APDs indicate too low a dose when the dose rate becomes too high. The alarm triggered thus indicates that the personal dose indicated by the APD is probably too low.
The alarm threshold to be set depends on the APD used and the exposure parameters at the X-ray unit. The following table shows alarm thresholds for the "EPD Mk2" dosimeter (Thermo Electron). The alarm thresholds depend on the firmware version of the "EPD Mk2" and the shortest exposure time you use in your exposures.
If you use a different APD, a different firmware version of the "EPD Mk2" or other recording parameters, you can calculate the corresponding alarm threshold yourself using an Excel sheet ("Alarmschwelle_berechnen.xls") provided by the Materialprüfungsamt Dortmund.
Always wear the APD under protective clothing.
The set alarm threshold must be communicated to the competent authority.
The competent authority must agree to the use of the APD.
If the alarm is triggered, you must leave the controlled area and have the official dosimeter evaluated immediately.