A standard dosimetry procedure for 192Ir sources used for endovascular brachytherapy

Abstract

The experimental dosimetry of a high dose rate (HDR) 192Ir source used for the brachytherapy of peripheral vessels is reported. The direct determination of the reference air kerma rate K̇r agrees, within the experimental uncertainty, with the results obtained by a well ionization chamber calibrated at the NIST and the manufacturer's certification. A highly sensitive (HS) radiochromic film (RCF), that presents only one active layer, was used for the source dosimetry in a water phantom. The adopted experimental set-up, with the source in its catheter positioned on the RCF plane, seems to have given better accuracy of the RCF optical density measurements. The agreement between the measurement of the dose rate constant DKr(10 mm, π/2) and the literature data confirmed the coherence of the HS RCF calibration obtained by the kerma in air measurements. The RCF measurements supplied dosimetric information about the dose to water per reference air kerma rate Ḋ(r, θ)/K̇r along the source transverse bisector axis, the radial dose function g(r) and the anisotropy function F(r, θ). The value Ḋ(2 mm, π/2)/K̇r = 22.4 ± 1.2 cGy h−1/(μGy h−1) is supplied with a dose uncertainty that is essentially due to the indeterminacy of the source position in the catheter. The data of the radial and anisotropy functions have been compared with Monte Carlo determinations reported in the literature.