Experimental determination of dosimetry parameters for Sinko ¹²⁵I seed source using thermoluminescent dosimeter

Objective: To study the dosimetry parameters of ¹²⁵I seed source (type Sinko BT-125-1) with thermoluminescent dosimeter (TLD) in the phantom. Methods: The new type of phantom was modified to suit to measurement of a common type of ¹²⁵I seed source. The AAPM TG43 protocol recommended measurements of dose-rate constant (Λ), radial dose function (gL (r)), and anisotropy function (F (r, θ)) have been performed in the phantom with TLD.Results The Λ was 0.928 cGyh-1 U-1. The gL(r) was determined at different radial distances r ranging from 1.0 to 10.0 cm with an interval of 1.0 cm; and F (r,θ) at angles from 0° to 90° in 10° increments. The gL (r) of ¹²⁵I seed source showed a difference of 9.6% at the most in comparison to the corresponding values of ¹²⁵I seed source (type Amersham 6711). The difference in F(2 cm, θ) of ¹²⁵I seed source and Amersham 6711 was up to 10.2% near the source end. With the phantom the combined standard uncertainty in the whole measurement was less than 6.0%. Conclusions: The experimental results exhibit fairly small measurement uncertainties and good self-consistency. It's feasible to measure the dosimetry characters of permanent implant seeds in the modified phantom. (authors)