Dosimetric Study Of Helical Tomotherapy,Step And Shoot Intensity-modulated Radiotherapy And Three-dimensional Conformal Radiotherapy As Well As Different Amounts Of Fields In3D-CRT For Liver Tumor

[Object]①The purpose of this study is to investigate the dosimetric characteristics andthe differences between the protection of normal tissues of HT, SaS-IMRT and threedimensional conformal radiotherapy (3D-CRT) in the treatment of liver tumour.②Toinvestigate the dosimetric characteristics and the differences between the protection oforgans at risk in different amounts of fields of3D-CRT in the treatment of liver tumour.[Methods]①The target regions of16patients with liver tumour in our department weredelineated by one doctor and every patient was given HT, SaS-IMRT and3D-CRT(fivefields) treatment plan. The prescribed dose for every plan was60Gy/20fractions.②CTimages of18patients with liver tumour in our department were chosen and each ofthem was given2fields,3fields and5fields treatment plans. CI, HI,95%and100%prescribed dose coverage of the target volume as well as irradiation doses and volumeof liver, stomach, right-kidney and spinal cord were evaluated through DVH.[Results]①The CI and HI of HT, SaS-IMRT and3D-CRT groups were0.796±0.076and1.044±0.019、0.663±0.108and1.059±0.164、0.540±0.075and1.077±0.010(P=0.000). The average dose and V10,V20,V30,V40, V50of liver of HT group were lowerthan those of other two groups and3D-CRT had the highest results (P=0.024andP=0.000). The average and the maximum dose of right kidney and stomach and themaximum dose of spinal cord in HT group were lower than the other two groups and3D-CRT still had the highest results.②PTV95%and PTV100%in2-fields,3-fields and5-fields groups were95.37±1.36%and95.17±0.76%、96.51±1.03%and95.19±0.69%、97.42±1.32%and95.20±0.62%(P=0.0000and P=0.8912), respectively. The CI andHI of2-fields,3-fields and5-fields groups were0.43±0.117and1.096±0.018,0.53±0.065and1.077±0.018,0.610±0.105and1.073±0.026(P<0.05). The volumes of normal tissues receiving low doses were larger and the maximum dose of spinal cordwas lower in2-fields group than the other two groups.[Conclusion]①In liver tumor radiotherapy, HT had larger advantages in the prescribeddose coverage of the target volume, CI, HI as well as the protection of normal tissuesthan SaS-IMRT and3D-CRT had the least.②In the liver tumor radiotherapy, theadvantages of PTV95%and PTV100%, CI, HI and high-dose region in5-fields group arethe best, followed by3-fields groups. The V10,V20of liver, the V10,V20,V30of right kidney,the average dose and the maximum dose of spinal cord were the lowest in2-fields group.But the V30,V40,V50of liver and stomach in5-fields group were the smallest.