The Optimization Study Of The Time-dose Factor Based On Non-conventional Fractionation Radiotherapy

Objective:The characteristics of different radiotherapy plans, which can be used in the tumor control and normal tissue protection, are compared by the analysis of the current biological effective dose (BED), and then a new and better radiotherapy optimization plan are put forward.Methods:The Cochrane Collaboration published the report of hyperfractionated or accelerated radiotherapy for head and neck cancer by in2010. Based on the data in the report, the BED values in different radiotherapy processes of corresponding tumor tissues and normal tissues are calculated by using linear-quadratic (L-Q) mode. For the different tissues of different treatment programs, the cumulative change values of BED along with time are observed:The characteristics of different radiotherapy in tumor control and normal tissue protection are analyzed. Finally, a new radiotherapy plan, which is suitable for clinic, is put forward.Results:When the total dose is70Gy, conventional segmentation scheme, especially for the hyperfractionated accelerated radiotherapy, can give a higher BED value of the tumor during a shorter period, and can effectively reduce total BED value in the late response tissues. Piecewise hyperfractionated treatment in tumor tissue can obtain a larger BED value, and can effectively reduce the accumulated BED value of the early response tissues during the treatment. By comparing different segmentation schemes, we can sum up the concrete implementation method of the new scheme. In the new scheme, the conventional segmentation irradiation is utilized for the first10days, and the hyperfractionated radiotherapy is utilized for the next18days according to gradually increased dose.Conclusions:The L-Q model is used to calculate BED values and to analyze the different treatment plans. Moreover, the variation of BED values along with the treatment process can effectively be observed. The mathematical model is utilized to evaluate the different radiotherapy segmentation scheme, which can find a way to play a guiding role in choosing the clinical symptomatic tumors treatment. In addition, the new optimization program can synthesize the respective advantages of previous radiotherapy plans.