EVALUATION OF A NEW BRACHYTHERAPY I-125 SOURCE BY AAPM TG43 FORMALISM

Dosimetric measurements were performed to characterize a new I-125 sou rce that is similar in design to existing sources and that has applica tion in interstitial brachytherapy. Thermoluminescent dosimeters were placed in phantom to measure transverse-axis and angular dose profiles over a range of distances from 0.5 to 7 cm. The data were analyzed in terms of parameters recommended by AAPM Task Group #43. Tabular data evaluated in liquid water are provided for the dose-rate constant, Lam bda, radial dose function, g(r), the anisotropy function, F(r,theta), the anisotropy factor, phi(an)(r), the point-source approximation anis otropy constant, <(phi)over bar (an)> and the point-source average dos e rate times the square of distance for unit air kerma strength, r(2)D (r). The new source is compared to the model 6702 I-125 source design, demonstrating similar dose-rate constant, Lambda, and radial dose fun ction, g(r). Differences in the anisotropy of the dose distributions a re discussed. Finally, a comparison of the radial dose distribution is made between Liquid water and tissue equivalent materials. (C) 1998 A merican Association of Physicists in Medicine. [S0094-2405(98)01811-2] .