X-ray spectra emitted by the electronic brachytherapy unit Papillon 50 measured with a CdTe spectrometer

The aim of this paper was to present the measured photon fluence spectra emitted by the electronic brachytherapy (eBT) unit Papillon 50.

Spectra were collected with a compact CdTe spectrometer in air at a distance of 52 cm from the unit output window, for three different applicators attached to the unit and at several angles with respect to the beam axis.

The fluence spectra recorded for this device showed lower energy of the photon spectrum end-point than anticipated. The end-point energy was found to be (47.6 ±0.2) keV for the nominal high voltage bias of 50 kV set by the operator. Full-energy peaks in the spectra identified characteristic photons emitted by the rhenium anode, and by molybdenum and silver supposedly present in the inner coating of the applicators. An asymmetry in the half-value layer values of measured spectra was observed.

The presented work provides a comprehensive dataset of photon fluence spectra for traceable dosimetry using the Papillon 50 eBT device, which is required, for example, for correcting the energy dependence of detectors or as an input for Monte Carlo calculations. Spectrometry and dose characterization studies are needed for eBT systems.