Quality control of nuclear medicine equipment – Definition of action levels and tolerance limits

Pursuant to § 83 subsection (5) of the Radiation Protection Ordinance (StrlSchV) all equipment used in nuclear medicine for examination or treatment purposes must be subject to internal quality control. At the technical level, all equipment is required to undergo an acceptance test when it is put into service and regular constancy tests afterwards. This serves to ensure proper functioning and to detect without delay deviations from an initial or target value (reference value) during operation.

As there are not yet any binding rules governing action levels and tolerance limits, the SSK has proposed values that would allow users and manufacturers to implement the quality assurance system described in the amended guideline on radiological protection in the medical field (Richtlinie "Strahlenschutz in der Medizin").

Action levels are values used in constancy tests. If they are exceeded, an investigation must be conducted in the framework of the quality assurance system into the underlying cause, and a previously defined course of action is triggered. Their purpose is, in particular, to prevent tolerance limits being exceeded during normal operation. At the same time, they are important tools for optimising radiation protection.

When tolerance limits are exceeded, the use of the equipment on patients is not allowed or only possible with restrictions until the cause has been found and the problem solved. Violations of tolerance limits, their causes and consequences must be documented in the log book stipulated in §34 of the Radiation Protection Ordinance (StrlSchV). Action levels and tolerance limits may be set at the same values, especially for older equipment.