# Independent verification of vendor‐issued dosimetric data for 106Ru brachytherapy using diode detectors with traceability to external beam standards for absorbed dose to water

## TL;DR

This paper introduces a new method to accurately measure radiation doses from 106Ru eye treatments using calibrated detectors and simulations, ensuring safer clinical use.

## Contribution

A novel framework for traceable absolute dosimetry of 106Ru brachytherapy using diode detectors and Monte Carlo correction factors.

## Key findings

- Calibrated diode measurements agreed with NPL alanine results but were lower than manufacturer data.
- Monte Carlo simulations showed significant depth-dependent correction factors for accurate dose calculations.
- Alanine/PMMA phantom showed non-water equivalence, emphasizing the need for direct water measurements.

## Abstract

Independent verification of the manufacturer‐provided dosimetry data for 106Ru ophthalmic brachytherapy applicators is crucial for safe and accurate treatment, yet a standardized, traceable method for clinical absolute dosimetry has been lacking.

This work establishes a complete framework for traceable absorbed dose to water measurements of 106Ru eye plaques in absolute units of Gray, complementing the high‐precision BetaCheck‐106™ setup with a robust detector calibration methodology independent of the source manufacturer.

Three microSilicon diode detectors were calibrated in traceable 60Co and 6 MeV electron reference beams. Depth‐dose measurements for four CCB‐type 106Ru plaques were performed in water using the BetaCheck‐106™ setup. Monte Carlo (MC) simulations were employed to calculate depth‐dependent beam quality correction factors kQ,Q0 which account for the detector's response in the 106Ru field relative to the calibration beams. The method was validated against measurements performed at the National Physical Laboratory (NPL) using alanine dosimetry. MC simulations were also used to investigate the water‐equivalence of the NPL alanine/PMMA phantom setup.

The MC‐calculated correction factors for the diodes showed a significant depth‐dependence, underscoring the necessity of such corrections in the steep 106Ru depth‐dose gradient. The dose rates determined with the calibrated diodes were in agreement with the NPL alanine results. Both methods yielded dose rates systematically lower than those provided in the manufacturer's certificates, though generally within the stated uncertainties. The MC simulations revealed substantial non‐water equivalence correction factors for the alanine/PMMA phantom, highlighting the advantage of direct measurements in water.

We present a novel, comprehensive methodology for independent and traceable absolute dosimetry of 106Ru applicators. By combining a dedicated water phantom setup with diode detectors calibrated against external beam standards and MC‐derived correction factors, this framework empowers clinical users to perform robust verification measurements, filling a critical gap in the quality assurance of ocular brachytherapy.