Comparison Of Dose Distribution Etween IMRT,VMAT And HT Plans Applied To SBRT In Non-cell-small Lung Cancer

By the comparison of dosimetric differences and influencing factors between Intensity Modulated Radiation Therapy(IMRT),Volumetric Modulated Arc Therapy(VMAT)and Helical tomotherapy in stereotactic body radiation therapy(SBRT)of non-cell-small lung cancer.To provide the dosimetry reference for clinicians or radiation physicist to choose the optimal radiotherapy mode for non-cell-small lung cancer.Fifty-two patients with non-cell-small lung cancer in department of radiotherapy of Sichuan Cancer Hospital were enrolled,who underwent stereotactic body radiation therapy(SBRT)from January 2015 to December 2015.Based on ICRU 83 reports,we delineated the outline of different regions as GTV,CTV,PTV and the organs at risks.Every patient were generated three radiation treatments plans as 6 wild IMRT,half or single arc VMAT and HT.The prescription dose was peripheral 48Gy in 4 fraction and central 56Gy in 8 fraction.To strictly limit the exposure dose of the Organ at risks(OARs).According to the Dose-volume Histogram,dosimetric parameters of three treatment plans for different locations and different tumor diameters were compared to assess plan quality.The one-way ANOVA of SPSS 22 statistical software was used to analyze the dosimetric parameters of three radiotherapy plans.Multiple linear regression models was used to analyze the factors influencing the dosimetric parameters of target and OARs.All of the radiotherapy plans can meet the restrictive conditions of target area and OARs.In univariable analysis,the dosimetric parameters of CI,HI and OARs were significantly lower than other two plans in HT plan.Compared with the exposure situations in lung(such as V5,V10,V15,V20 and MLD)among three radiotherapy plans,IMRT planning was better than VMAT and HT planning,difference was statisticantly significant(P<0.05).While compared with VMAT and IMRT,HT planning showed superior V30,V40 of lung sparing.There was no significantly difference in OARs as heart,spinal cord and chest/rib between IMRT and VMAT planning,as like as HI and CI(P>0.05).In multivariable analysis,the dosimetric parameters of lung(such as V5,V20 and MLD)associated with the tumor volume(GTV),tumor maximum size,radiotherapy planning and the distance of tumor and heart.In addition,along with the tumor maximum size increase by one centimeter or tumor volume increase by one cubic centimeter,the lung V5 increased by 0.058%and 1.269%,the lung V20 increased by 0.037%and 1.087%,and the MLD increased by 0.014Gy and 0.152Gy respectively,difference was statisticantly significant.Further more,the distance of tumor and heart,central and VMAT or HT planning were risk factors of lung V5,V20 and MLD.We also found the tumor volume,tumor type,tumor maximum size,radiotherapy planning and the distance of tumor and OARs associated with the dosimetric parameters of OARs(lung excepted).Compared with IMRT planning,VMAT and HT planning were used as protective factors for the OARs(lung excepted),which can reduce the exposure dose of the OARs.In contrary,tumor volume,and tumor maximum size were used as risk factors for OARs(lung excepted).Compared with VMAT and IMRT planning,HT planning showed better dosimetric quality and more excellent OARs sparing.HT planning has advantaged in protecting the normal tissue surrounding tumor,especially the OARs that were close to the tumor.There was no significant difference in dosimetric parameters of OARs(lung excepted)between IMRT and VMAT planning.Compared with the exposure dose of lung(such as V5,V10,V15,V20 and MLD),IMRT planning showed the best than IMRT or VMAT.IMRT planning has advantage in reducing the incidence of radiation pneumonitis.Based on DVH,we found that the exposure dose of OARs(lung included)was affected by various clinical factors.Therefore,these clinical factors should be token into account to choose the optimum radiotherapy technology in clinical application.