Development Of Radioluminescence Gel Materials For Radiotherapy 3D Dose Verification

Dose verification is an important section of the tumor radiotherapy.Current radiotherapy techniques have entered the era of precision radiotherapy.New radiotherapy technologies such as IMRT,IGRT,DGRT,IMAT,VMAT,take a large number of superimposed sub-fields in the implementation process,which brings dose verification some new challenges and puts forward higher demands on the resolution of dose verification devices.In the process of dose verification,the radiation response unit is one of the most critical components,which directly determines the accuracy and reliability of dose verification.At present,the dose verification materials include film,polymer gel,Fricke gel,etc.The film has poor tissue equivalence,oxygen in air may inhibit radiation-induced polymerization,while the Fricke gel has problems such as diffusion of iron ion.Therefore,a new type of dose verification material that may use for instant 3D dose verification and shorten the verification period is planned to be developed.The paper uses radioluminescence materials as radiation responsive materials and hydrogel matrix as tissue-equivalent material.The paper mainly studies composite hydrogel and nano-luminescent materials that can be used as immediate radiation responsive materials.Three types of luminescent materials have been synthesized and their physicochemical properties have been characterized.The CdS quantum dot composite hydrogel was synthesized in situ using radiation one-step method.The synthesized CdS QDs with uniform size（4.5±0.4 nm）disperse evenly in the composite hydrogel.The QDs can form the coordinate bond with amino groups of the hydrogel matrix,which may modify the quantum dots and fix the light emission positions of them.The emission peak of material locates at 640 nm under 310nm ultraviolet excitation.The luminescence intensity increases with the doping concentration,but the emission peak does not affect the emission peak.Liquid scintillation counter experiments show that the response signal of composite hydrogel to radiation is weak.ZnS:Cu and ZnS:Ag doped semiconductor nanoparticles were prepared by radiation method.Their particle sizes were 8.07±1.14 nm and 8.87±1.53 nm,respectively.Both particles can disperse in water steadily,and can be further added into the hydrogel.Characterizations by EDS and XPS proved that doping ions were incorporated into the material matrix.The excitation wavelength is 365 nm,and the emission peaks are all located at 460 nm.After doping the ions,the UV fluorescence emission intensity of the nanoparticles was enhanced,while the location of emission peak was unchanged.It shows that the emission originates from the defect state emission of ZnS,not the emission of impurity level brought by the doped ions.Liquid scintillation counter experiments show that the response signal of nanoparticles to radiation is also unideal.Gd₂O₂S:Eu and Gd₂O₂S:Tb nano-particles coated with oleic acid and oleylamine as ligands,which have good dispersion properties and uniform size（10.85+1.38 nm and9.34+0.85 nm,respectively）in cyclohexane,were prepared by thermal decomposition method.Liquid scintillation counter experiments show that the radiation response signal of nanoparticles is good.The nanoparticles were modified to be water-dispersed by ligand adsorption method.Both nanoparticles have excellent UV fluorescence properties before and after modification.Gd₂O₂S:Eu emits 625 nm red light and Gd₂O₂S:Tb emits 550 nm green light.In addition,the X-ray luminescent property of two synthesized nanomaterials was investigated.The experimental results show that the locations of emission peaks are unchanged under both X ray excitation and UV excitation.The radiation response wavelengths are visible light,which facilitates the collection of dose data.There is a good linear relationship between the Gd₂O₂S:Eu emission intensity and the intensity of X-ray.In the end,the preparation and characterization of two kinds of water-dispersed rare-earth particles composite hydrogels were studied.