Dosimetric characteristics of 192Ir sources used in interstitial brachytherapy

Dosimetric quantities of 192Ir seed (5 mm length) and wire (10 mm length) brachytherapy sources have been determined. The quantities were measured based on the protocol introduced by the Radiation Therapy Committee of the American Association of Physicists in Medicine (AAPM) Task Group 43. Quantities such as dose rate constant, (Λ), radial dose function, g(r), and anisotropy function, F(r, θ) were experimentally determined and the geometry function, G(r, θ), was calculated. TLD measurements were made in a polymethyl methacrylate (PMMA) phantom of dimensions 25 cm×20 cm×5 cm by means of LiF:Mg,Ti (TLD-100) dosimeters for distances of 1–10 cm for g(r), and the same distances at angles of 0–180° for F(r, θ). Dose rate constant for 192Ir seed and wire were found to be 1.196±5 and 1.082±5% cGyh−1 U−1, respectively (1U=unit of air Kerma STRENGTH=1 μGy m2 h−1=1 cGy cm2 h−1). The obtained results for g(r), G(r, θ) and F(r, θ) are also presented and discussed.