In addition to seed implantation, which is often used for prostate cancer, there is also the afterloading procedure.
Seed implantation (low dose rate = LDR)
The number of radiation sources (so-called “seeds” = 0.5 cm long iodine particles) to be used is determined by the physicist during an ultrasound scan. These seeds are subsequently inserted under full anaesthetic using a cannula. The exact position of the seeds is again determined during the post-planning phase. The seeds remain permanently in position. It takes around 20 days for half of the radiation dose to be released.
Afterloading (high dose rate = HDR)
With temporary afterloading implantation with Iridium-192, applicators in the form of metal or plastic needles or tubes are inserted and secured in the tissue to be treated (tumour), after the usual radiation plan has been calculated and the optimal positioning of the radioactive sources has been determined. Following this, the afterloading device is connected. The radioactive isotope is located in the device’s so-called “safe”. It sits at the tip of a wire, which is then inserted into the applicator where it remains for a predetermined period of time (usually only a few minutes). The wire is then pulled back into the safe and the patient is mobile again until the next session. With the help of computed tomography controlled implantation techniques, the applicators can be inserted in almost any region of the body.