INTRODUCTION
This white paper discusses how to perform X-ray tube leakage measurements with survey meters, in relation to relevant standards and regulations.
X-ray tube leakage measurements are performed to find potential leakage of ionizing radiation from X-ray tubes. It is part of the radiation safety procedures at hospitals and manufacturers of X-ray machines. During a leakage measurement, the X-ray machine is operated with the radiation on and the collimator closed. The person who performs the measurement uses a survey meter to examine the area around the X-ray tube at a specific distance. The position where the leakage dose is the highest is identified and quantified, as is the number of exposures that could be performed during one hour in the lab. The result is compared to an upper dose limit, provided in standards and regulations, to determine if the X-ray machine passes or fails.
International standards1 and local regulations2 provide guidelines on:
- The upper limit for dose measured in one hour
- The area over which the dose measurement should be averaged
- At what distance the limit is valid, either from the X-ray focal spot or from the X-ray tube housing
The numbers provided in standards and regulations often raise practical questions about the measurement procedure, and how the design of the survey meter may affect the measurements. This white paper discusses the interpretation of the referred standards and regulations, with focus on:
- the X-ray modality, such as fluoroscopy or radiography
- a homogeneous versus a non-homogeneous X-ray field
- the size of the active sensor area of the survey meter
- the distance to the X-ray source or tube housing
The paper ends with a discussion of how different survey meter properties affect accuracy and practicalities at measurements.