Study On Ferric Ion Diffusion Limitation Of Frcike Gel Dosimeter

Accurately measuring and delivering the target dose in radiotherapy is essential to improvement on the therapy efficient for extending the life of the tumor patients.Nowadays three-dimensional dosimeter,which can record the spatial distribution of the absorbed dose in target organs,is a hot topic in radiation field.Fricke gel dosimeters are based on the oxidation of ferrous ions(Fe²⁺)into ferric ions(Fe³⁺)during irradiation.Thus,quantification of the concentration of ferric ions is able to display the spatial dose distribution.However,due to the gradient in the ferric ion distribution,the ferric ions diffuse throughout the gel matrix,resulting in the vague in the dose distribution.The ion diffusion is a issue which limits the application of a Fricke gel dosimeter system.In the thesis,we proposed a technique for PVA microsphere fabrication,and obtained a PDMS-coated PVA microspheres,which were used in Fricke dosimeter with the capability of inhibiting the diffusion of Fe³⁺.In addition,we had synthesized amphiphilic poly copolymers,and then formed the polymers into W₁/O/W₂ multiple emulsions which containing Fricke solution,achieved limiting the diffusion of Fe³⁺on a smaller scale.Our researches include:1.A technique was proposed of using liquid nitrogen frozen to prepare microspheres.The microspheres with small size were well shaped,and high quality in mechanical properties.2.The PDMS-coated PVA microsphere dosimeter was prepared and the limiting diffusion behavior of Fe³⁺was studied.After irradiation,the result of Fe³⁺diffusion of PDMS-coated PVA microsphere dosimeter is consistent with the result of finite element analysis,indicating that this dosimeter is able to inhibit the diffusion of Fe³⁺?3.A new amphiphilic poly copolymer was synthesized and used to form a W₁/O/W₂ vesicle structure in Fricke dosimeter.The diffusion coefficient of the ferric ions in the Fricke dosimeter was0.17mm²h^-1,while it is 0.23mm²h^-11 in the traditional Fricke dosimeter.