The Application Of Radiobiological Models In The Evaluation Of Plan Quality For SBRT

The main purpose of radiotherapy is to increase the dose distribution in the target area,and reduce the radiation damage to the normal tissue,so as to improve the rate of tumor control and the survival rate of patients.Stereotactic radiotherapy(SBRT)is more and more widely used in clinical radiotherapy.However,radiation exposure to the tumor will also increase the false exposure of surrounding normal tissues,thus causing complications of radiotherapy.In this paper,biological models were applied to the evaluation of radiation plan,including the equivalent uniform dose(EUD),tumor control rate(TCP)and normal complication model(NTCP)were applied to the evaluation of SBRT program.Firstly,EUD,TCP and NTCP formulae were converted by suing biologically effective dose(BED)so that they could be applied in the SBRT plan with single large dose.The physical dose of high perfraction dose was converted to the dose of a single 2Gy through the biologically effective dose.Then,the application of models in the plan evaluation of prostate cancer,prostate cancer,head tumor and bilateral lung tumor was studied,and the parameters of each model in different tumors and normal tissues were obtained through literature research.For prostate and pancreatic cancer,through the analysis of dosimetric and biological index data to evaluate different SBRT plans in Cyber Knife and EDGE system,EDGE plan is considered safer than CK plans for the clinical effect of patients with prostate plan expected,while the CK plans for pancreas cancer showed more security;For head tumors,biological indicators were mainly used to evaluate the cyberknife plan for different normalized isodose lines(IDL).According to the experimental data,the superior dose line of head tumors were in 70%~75% that showed relatively good protection for normal tissues.For bilateral lung tumors,the difference of dosimetric and biological indicators were mainly evaluated when the single plan and the double plan were used.The results showed that the double plan was better for the protection of normal tissues and safer,but the treatment time was relatively long.By applying the biological model in the SBRT program evaluation of different tumor patients,the evaluation results are consistent with the dosimetric parameters,while the biological model indicators link the physical dose with the expected clinical efficacy,so as to provide a more comprehensive program evaluation method for doctors and physicists.