Gadolinium dose enhancement determination by unlaminated EBT3 films irradiated with 192Ir brachytherapy source

An Optimized Method for Evaluating the Potential Gd-Nanoparticle Dose Enhancement Produced by Electronic Brachytherapy

“…Previously reported methods found in the literature that involve the delamination and subsequent resealing of EBT3 films limited the dosimetry measurement in water of the dose enhancement produced by nanoparticles to exclusively gamma photons and medium-energy X-rays (>80 kV according to the IAEA TRS-398 protocol), which were capable of generating photoelectrons of energies greater than 25 keV that managed to pass through the thin film used in the resealing process (10-times thinner than the original laminate) [ 47 ], preventing the use of this methodology for the low-energy beams (<80 kV) employed by eBT and IORT units. The method proposed in this work used a filter that was five-times thinner (2.5 m) than that of the previous procedure, since its function was limited to being a waterproof barrier between the radiosensitive substrate present in the film and the water that contained the Gd suspension, thus removing the mechanical strength and elasticity that was required of the filters, in both the resealing process and the subsequent immersion of the film in water, damaging the latter due to the entry of water into the active substrate and resulting in a greater dispersion and uncertainty in its reading.…”

“…Gafchromic ® EBT3 films (Ashland Advanced Materials, Bridgewater, NJ, USA) were meticulously delaminated based on the method described by [ 47 ]. The opening of the first 125 m layer of polyester was carried out employing a surgical scalpel and applying a constant traction force achieved through the use of a controlled mechanical device.…”

“…Consequently, interventions are limited to delamination followed by the application of a new waterproof element with a thickness that enhances the detection of low-energy electrons. Recently, the possibility of altering EBT3 dosimetric films by delaminating and resealing them using materials with thicknesses of 12 m to maintain their water immersion properties has been reported [ 47 ]. The dosimeters evaluated after the intervention maintained their dosimetric properties unaltered, allowing the recording of photoelectrons of energies greater than 25 keV, generated by a 192 Ir brachytherapy source in a phantom with Gd suspensions and dose enhancement values of 15%, compatible with Monte Carlo simulations and previous measurements.…”