In brachytherapy where position information relating to a radiation source is to be generated, a guidance system is adapted to acquire and process position data or position and tissue data, so that high-precision interventional radiotherapy can be carried out, especially according to a dose plan and for intra-fraction monitoring for a therapy plan or adaptive re-planning. The data can be stored and used to refine future treatment plans and for future correlation with long-term treatment outcome, especially in context with low energy brachytherapy.
