Dosimetric Comparison Between Helical Tomotherapy And Intensity-modulated Radiotherapy Of Target Area And Organs At Risk For Mid-thoracic Esophageal Carcinoma

Objective:This study analyzed and compared the dosimetric differences between intensity modulated radiation therapy(IMRT)and helical tomotherapy(TOMO)radiotherapy techniques in the target areas and organs at risk in the middle esophageal carcinoma to provide the basis for the clinical choice of treatment options.Methods:By selecting 22 patients with the middle esophageal carcinoma from May 2015 to June 2017 in the Third Affiliated Hospital of Kunming Medical University,we collected clinical data of all patients,including gender,age,general condition,tumor site(middle esophagus),pathological type,disease Stages(TNM staging),chemotherapy regimens,and courses of treatment.This study has obtained informed consent from patients.The IMRT and TOMO plans were designed for each of the 22 patients with esophageal cancer.To analyze the dosimetric characteristics of the target area and the endangered organ(main observation index)of the IMRT plan and the TOMO plan,and to compare the dosimetric differences between the two radiotherapy plans,especially the difference in the organ at risk(OAR)low dose volume.Results:1.Target areas dosimetry comparison results:PTV and PGTV in the two programs had significant differences in Dmean,D2,D50,D95,CI,HI(P<0.05).In addition to the CI values,each parameter in the MRT plan were higher than the TOMO plan.the CI values in the IMRT plan were lower than the TOMO plan;Among them,the V105(%)of the PTV in the TOMO plan was significantly lower than that of the IMRT plan.2.OAR dosimetry comparison results:(1)Left,right lung,and whole lung:There were significant differences in V5(%),V10(%),V20(%),and V30(%)in the left,right,and whole lungs of the two plans(P<0.05).The mean value of V20(%)and V30(%)in the IMRT plan was higher than that of the TOMO plan,while V5(%)and V10(%)in the IMRT plan were lower than the TOMO plan.(2)Cardiac:There were significant differences in V20(%),V25(%),V30(%),V35(%),and V40(%)between the two plans(P<0.05).Each value in the IMRT plan was higher than the TOMO plan..(3)Spinal cord:There was a significant difference between the two plans for D2(P<0.05).The D2 value in the IMRT plan were higher than that of the TOMO plan.(4)Cardiac substructure:The V35(%)and V40(%)of the left atria(LA)in the IMRT plan were higher than the TOMO plan;the left ventricle(LV)two plans No significant difference was found in all indexes(P>0.05).There was no significant difference between the two plans in all values of left ventricle(LV).The V25(%)and V30(%)of the right atrial(RA)in the IMRT plan are higher than those in the TOMO plan,(P<0.05);There were significant differences in V20(%),V25(%),and V30(%)between the two indicators of the right ventricle(RV)in both plans(P<0.05).The V25(%),V30(%)and IMRT plans of the left anterior descending artery(LAD)in both plans are significantly higher than those of the TOMO plan(P<0.05);The V20(%),V25(%),and V30(%)of the right coronary artery(RCA)in the TOMO plan were lower than those of the IMRT plan,(P<0.05).Conclusion:Compared with intensity-modulated radiotherapy,Tomotherapy for mid-thoracic esophageal carcinoma not only shows obvious advantages in conformity and uniformity of the target area,but also predominates in the protection of the organs at risk,such as heart,sub-structure of the heart,and the spinal cord;Although Tomotherapy significantly reduce the high dose volume of the left and right lungs and the whole lung,but significantly increase the low dose volume of them.Therefore,for patients with poor lung function,we should comprehensively assess and balance the relationship between high-dose volume and low-dose volume.