Impact of delineator and delineating criteria on the target delineation of the peripheral lung cancer based on four-dimensional computed tomography / 中华放射医学与防护杂志

ABSTRACT

Objective To investigate the impact of delineator and delineating criteria on the target delineation of the peripheral lung cancer based on four-dimensional computed tomography (4D-CT).Methods The 4D simulation CT images of twelve patients with peripheral lung cancer were selected.Before and after the establishment of the target delineation criteria,six radiation oncologists were asked to delineate the targets based on 4D-CT images at the end-inhalation phase (0％),end-exhalation phase (50％),and three-dimensional computed tomography (3D-CT) images respectively.The delineated targets were denominated as GTV0,GTV50,GTV3D.IGTVIN+Ex was created by combining GTV0 and GTV50.IGTVMIP was delineated based on the maximum intensity projection (MIP) of 4D-CT.The interand intra-observer variability before and after the establishment of the delineation criteria was compared.Results The mean coefficients of variation of GTV0,GTV50,GTV3D,IGTVMIP and IGTVIN+Ex delineated by the six delineators before and after the establishment of the delineation criteria were 0.50 ± 0.25 vs 0.24 ±0.10,0.52 ±0.38 vs 0.26 ±0.12,0.45 ±0.19 vs 0.20 ±0.07,0.54 ±0.27 vs 0.23 ±0.09 and 0.44±0.23 vs 0.26 ±0.09,respectively.The differences were statistically significant(t =3.38,2.44,3.60,4.20,3.11,P ＜ 0.05).No statistically significant difference was found in the volume of the same target for GTV0,GTV50,GTV3D,IGTVMIP and IGTVIN+Ex delineated by the six oncologists before and after the establishment of the delineation criteria.For delineator 3 and 6,the differences of GTV0,GTV50,IGTVIN+EX before and after establishment of the delineation criteria were statistically significant(t =2.46,2.91,3.28,P ＜0.05 ;t =2.40,2.79,3.22,P ＜0.05).For delineator 4,the differences of GTV0,GTV50,IGTVIN+EX,IGTVMIP,GTV3D before and after establishment of the delineation criteria were statistically significant (t =2.70,3.21,3.04,3.99,3.00,P ＜ 0.05).Conclusions The unified delineation criteria can significantly reduce the inter-observer variability in delineating the GTVs based on 3D-CT or 4D-CT images,and in delineating the IGTVMIP based on 4D-CT images of peripheral lung cancer patients.However,regarding the same delineator,various influences of the unified delineation criteria on the target delineation are observed.