The Fabrication And Property Of Fricke Gel Dosimeter With Irradiation Method

It is an important principle of radiation dosimetry to give adequate dose to the tumor region, while making the neighbor normal organs exposed least. To ensure this principle is achieved, we must adopt strict quality assurance(QA) and quality control(QC) measures, and dose verification is one of the essential process. Because of its simple preparation and the equivalence to tissue and water, Fricke gel dosimeter shows the potential as a standard 3D dose verification device. This paper studies the fabrication conditions of Fricke gel dosimeter with irradiation method, and the structure, properties of the gel dosimeter.The paper analyzes the radiation crosslinking polymerization process of acrylic monomers, and finds out that with lower Fe2+ content, higher acrylic acid content, we can increase the gel content of the sample. With acrylic acid content increasing, the water absorption of the sample will be decreasing and retention will be increasing; and with the dose increasing, the water absorption and retention of the sample will be both decreasing; at the same time the analysis of the content of Fe2+ and Fe3+ in the sample with spectrophotometry shows that ions in the sample are not easy to be washed out, and the average Fe2+/Fe3+ ratio is higher than 0.81.The paper uses FTIR, XRD, TGA and other technology to analyze the structure and stability of gel. FTIR proves the existence of 2 kinds of hydrophilic groups in the molecular chain of the polymer(OH and CO). XRD spectra shows that, under aerobic conditions, the iron ion in the material for crystal materials, is Fe3O4, and other samples without oxygen shows that there is no inorganic metal XRD peak. TGA test results show that the samples doping with Fe2+ or xylenol orange are consistent with pure polypropylene acid gel on the curve, but the thermal stability is slightly decreased. At the same time, we analysis the auto oxidation behavior of the samples, and find out that the extension of time, increasing of the concentration of Fe2+ or mixing with xylenol orange, will promote the automatic oxidation behavior, which will reduce the dose stability of samples.The paper discusses the diffusion behavior of Fe2+ in gel by means of molecular dynamics. Molecular dynamics shows that, compared with the PVA chains, the polyacrylic acid chains tend to be closer to each other, which contributes to inhibiting the diffusion of iron ions in the gel samples; the dose response relationship of Fricke gel dosimeter was analyzed, which shows that, in the dose range of clinical use, the Fricke gel dosimeter shows low dose resolution, after the addition of xylenol orange, the absorption spectra can be improved, but meanwhile the linearity is decreased.