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.
ABSTRACT
Objective To investigate three-dimensional dose distribution for 103Pd radioactive stent.Methods The surface dose,the axial dose and radial dose in surface for 103pd stent (3 mm × 13 mm) were estimated by experimental simulating method, analytic function and MCNP4b code. Three-dimensional dose distribution was calculated by MCNP4b code. Results The surface dose of 103pd stent was 0. 109 and 0. 106 Gy estimated by experimental simulating method and MCNP4b code,between which the difference was less than 3%. The axial dose calculated by analytic function and MCNP4b code was well consistent,and so was the radial dose estimated by the three methods. Dose rate table were estimated by MCNP4b code. Conclnsions Dose distribution for 103 Pd stent estimated by the three methods is relatively accurate. Three-dimensional dose table estimated by MCNP4b may be used to calculate dose for 103Pd stent in animal experiment and clinical application.
ABSTRACT
Objective To calculate the mean absorbed doses at celluar and subcellular levels for uniformly and non-uniformly distributed Auger electron emitters. Methods The energy deposited in cell or nucleus by Auger electrons was analytically calculated using the polynomial representation of energy loss.S-values were subsequently computed for several target-source combinations.The absorbed dose and dose distribution were calculated for spherically symmetric radionuclide distributions depending linearly and exponentially on the radial position.The dose profile as a function of the source radial coordinate was also evaluated for typical cell sizes.The contributions of photon radiation to absorbed dose in cells were ignored. Results The mean absorbed dose and dose distribution depend largely on the size of target cells,the radiation spectrum and intracellular localization and distribution of radionuclides.The contribution of intranuclear radionuclides to mean absorbed dose was larger than that of extranuclear ones. Conclusion Auger electrons can produce high local energy deposition in cells because of their very low energies and extremely short ranges.Our dose calculation method is simple.The results are reliable and can be used in many fields.