Quality control of sealed beta sources in brachytherapy

At present, several types and subtypes of beta sources are in use in radiotherapy institutes in the Netherlands and Belgium. There is large variation in quality control - and more specifically in dosimetry - of these sources. In this report recommendations are presented on detectors and measurement procedures for the dosimetry of beta sources. In addition, recommendations are given on the quality control procedures for beta sources in general, as well as action levels for deviations in source strength and uniformity.

The recommendations on suitable detectors and measurement procedures are based on on-site measurements at 21 radiotherapy institutes in the Netherlands and Belgium. These experiments were performed with well-type ionization chambers, a plastic scintillator, a plane-parallel ionization chamber, radiochromic film and a diode. Based on this experience, parameters are proposed for the evaluation of source strength, non-uniformity and - in the case of ophthalmic sources - asymmetry.

Recommendations are presented for quality control of beta sources. On one hand, recommendations are given on the dosimetric parameters that should be determined and on the maximum deviations. On the other hand recommendations are given on, for example, the accuracy of source positioning, frequency of dosimetry and radiation safety aspects, such as measurements of leakage radiation.

With these recommendations it is expected that standardization of dosimetry and quality control of beta sources in the Netherlands and Belgium will improve and that the chance of treatment failure or emergency situations will reduce. With the availability of a primary standard for beta dosimetry at the Netherlands Measurements institute (NMi), physicists will be able to perform absolute measurements on beta sources using a calibrated detector.

https://doi.org/10.25030/ncs-014