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 V_2.5,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 D_max,heart D_max,esophagus D_max,trachea D_max,chest wall D_max 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 D_max 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.

Key words: Non-coplanar, Stage Ⅰ NSCLC, Stereotactic body radation therapy