Dose measurement of ophthalmic Ru-106/Rh-106 applicators with a diamond detector calibrated in a clinical megavoltage electron beam.

Abstract

Objective.Uveal melanomas and retinoblastomas can be treated with ophthalmic beta-emitting ruthenium-106/rhodium-106 applicators. The applicator manufacturer provides a datasheet of the dosimetric properties of each applicator set, but the source strengths and 3D dose distributions should be verified by the end user with independent measurements.Approach.The purpose of this work was to calibrate diamond detector against low energy electron beam and determine necessary correction factors in the geometry of ophthalmic applicators to be able to perform quality assurance (QA) measurements for the applicators. Two separate sets of applicators were evaluated.Main results.The results showed good agreement with manufacturers' specifications. An average agreement of 3% to the manufacturer's reference data was observed: measured dose rate/reference = 0.97 ± 0.04 (mean ± SD), range 0.90-1.05.Significance.It can be concluded that megavoltage electron beam is suitable for calibration of a diamond detector. After calibration, detector can be used for an absolute dose measurement of a ruthenium-106/rhodium-106 applicator with sufficient performance to detect deviations larger than 10% in the QA before clinical use.