Experimental measurements of dosimetric parameters of Ir-192 new source / 中华放射肿瘤学杂志

ABSTRACT

Objective To perform thermoluminescent measurements of radial dose function and anisotropy function of a newly designed 192Ir microSelectron-HDR source, and establish evaluation methods for HDR dosimetry.Methods A polystyrene phantom with sylindrical holes in different measure positions was designed to accommodate thermo luminescent dosimeter (TLD) rods and radiation source.TLD rods with similar sensitivity were placed on a semicircle around the source center which had been precisely localized by either radiographic means or dose measurement.Dose-rates were measured at θ = 90° and r = 1-14 cm to calculate radial dose function (gL (r)), while measured along polar angles θ = 0° -165°(interval 15°) at radial distances r = 1 cm, 3 cm and 5 cm to calculate anisotropy function (F(r,θ)).All data were compared with those calculated by Monte Carlo (MC) method.The t-test was used for the statistics.Results The values of gL (r) were 1.007 -0.681 by calculation and 1.007 -0.598 by measurement with r = 1 - 14 cm(t = 0.00 - 2.89, all P > 0.05).The values of F (r,θ) were 0.631 - 1,0.660 - 1 and 0.696 - 1 by calculation, while 0.701 - 1, 0.668 - 1 and 0.629 - 1 by measurement at 1 cm, 3 cm and 5 cm with θ=0° -165°(t=0.40 -1.63, 0.02 -2.10, 0.08 -2.03, all P>0.05).Conclusions The results of radial dose function and anisotropy function measured by TLD measurement are in consistent with those calculated by MC calculations, which can be applied in treatment planning system as original input.