ABSTRACT
Objective The objective of this study was to study the dosimetric characteristics and advantages of Non-coplanar IMRT techniques stereotactic body radiation therapy(SBRT)in the early stage of NSCLC.Methods Ten patients were selected with early stage of NSCLC.Treatment planning designed 9 fields coplanar IMRT and 9 fields Non-coplanar IMRT,respectively.Non-coplanar plans include five coplanar fields and four non-coplanar fields.Two group patients' plans compared V2.5,V5,V20,V25 of the whole lung,the average exposure doses of the whole lung,and the average exposure doses of the contralateral lung.The comparison of the other OARs include:spinal cord Dmax,heart Dmax,esophagus Dmax,trachea Dmax,chest wall Dmax and V30 of chest wall.At the meantime,we compared the conformal index of PTV(CI)and the homogenization index of PTV(HI).Results Non-coplanar plans reduced V20 of the whole lung(P=0.001),the average exposure dose of the contralateral lung(P=0.001),but V5 of the whole lung non-coplanar plans were increased than that in coplanar plans(P=0.002).Non-coplanar technology reduce max dose of spinal cord,esophagus,trachea,chest wall and V30 of chest wall(P=0.026,0.001,0.026,0.008,0.016).Heart Dmax of the non-coplanar plans was high in coplanar plans with no statistical significance difference(P=0.296).The conformal index of PTV of the non-coplanar plans was better(P=0.036),there was no difference in the homogenization index of PTV(P=0.254).Conclusion The stereotactic body radiation therapy of the early stage of NSCLC,the non-coplanar technology can effectively reduce exposure doses of the lung tissue and the other most OARs,also improve the conformal index of the PTV.The non-coplanar technology have possibility in reducing complications when compared with the coplanar technology and therefore has certain dosimetry advantage.