Internal clinical acceptance test of the dose rate of 106Ru/106Rh ophthalmic applicators

For the last forty years or so, episcleral brachytherapy using 106Ru/106Rh ophthalmic applicators has been a proven method of therapy for uveal melanomas, sparing the globe and in many cases conserving the vision. In episcleral brachytherapy, a radioactive 106Ru/106Rh ophthalmic applicator (BEBIG Co., Berlin, Germany) is temporarily fixed on the surface of the bulbus oculi, whereby the intraocular tumour gets irradiated protractedly through the sclera. 106Ru/106Rh ophthalmic applicators are primarily beta sources, i.e. they generate a local dose escalation both in the vessels supplying the tumour and in the tumour itself, while simultaneously sparing the risk structures. In its certificates, BEBIG, the manufacturer of the product, indicates a dose rate for the 106Ru/106Rh ophthalmic applicators at a dose specification reference point which ensures traceability to the NIST standard (12/2001). The dose specification reference point is situated at a distance of 2 mm from the middle of the inner (concave) surface of the applicators, and the dose rate was measured with a scintillation detector (diameter 1 mm, height 0.5 mm). The manufacturer indicates for this dose rate at the dose specification reference point a relative measurement uncertainty of ±20% within the 95% confidence interval. Since the introduction of the NIST calibration, the quality of the calibration passed on by BEBIG to the user has been examined for n=45 ophthalmic applicators