Clinical beta radiation dosimetry for brachytherapy in terms of absorbed dose to water: ISO new work item proposal for international standardization.

Purpose: Beta radiation has found increasing interest in intravascular brachytherapy for successfully overcoming the severe problem of restenosis after interventional treatment of arterial stenosis. Prior to initiating procedures applying beta radiation there is a common need to specify methods for the determination and specification of the absorbed dose to water or tissue and their spatial distributions. The DIN-NAR standardization in radiology task group Dosimetry has initiated an international ad hoc working group for an ISO new work item proposal on the standardization of procedures in clinical beta radiation dosimetry.

Methods: The intent of this standard is to review methods and to give recommendations for the calibration of therapeutic beta sources, a code of practice for clinical beta radiation dosimetry and guidance for estimating the uncertainty of the absorbed dose to water delivered. The standard will be confined to "scaled" radioactive sources such as single seeds, source trains, line, shell and volume sources for which only the beta radiation emitted is of therapeutic relevance. The topics will include dosimetric quantities; source data; calibration and traceability; general principles and requirements for absorbed dose measurements; in phantom dosimetry; theoretical modeling; presentation of dose distributions; clinical dosimetry; clinical quality control; irradiation treatment planning; as well as uncertainties. The document is geared to organizations wishing to establish reference methods in dosimetry aiming at clinical demands for appropriate small measurement uncertainties. Existing normative documents as well as international recommendations, such as those from AAPM, DGMP, ESTRO, NCS, ICRU, or IAEA will be taken into account.

Results: The first meetings of the new international working group took place in March and September 2002 at Essen, Germany [IAEA-cn-96-73, 2002].

Conclusions: Based on the DGMP Report 16, the AAPM TG 60 up-date draft, other recommendations and normative documents, the DIN-NAR project has collected and prepared detailed material on the calibration and dosimetry of beta radiation brachytherapy sources in terms of absorbed dose to water. The ISO new work item proposal will be completed in spring 2003.