| Objectives Based on the 4D-CT technique,the center point of the gross tumor volume(GTV)of lung cancer patients was evaluated with the displacement of respiratory movement,and the correlation between displacement and tumor location and tumor volume was discussed,providing reference for accurate delineation of the target area.The differences of maximum intensity projection(MIP)and average intensity projection(AIP)images obtained based on 4D-CT scan in the radiotherapy localization of lung cancer were compared and analyzed,and the influencing factors of the volume difference of target area were discussed.Methods Sixty patients with lung cancer were enrolled,3D-CT and 4D-CT localization scans were performed sequentially.Based on 3D-CT and 4D-CT scans,respectively,A total of 10 time-phase CT images,MIP and AIP images were obtained to sketch GTV.GTV-3D,ITV-M and ITV-A were formed respectively.The maximum movement degree of GTV center point in the direction of left and right,front and rear,head and foot was measured,and the 3D directional displacement vector was calculated.The relationship between different lung lobes and tumor volumes,their degrees of motion in different directions and their 3D displacement vectors was analyzed.The differences of target volume between different pulmonary lobes were analyzed,and the factors affecting the differences were discussed.Results 1 The minimum value of GTV center displacement of 60 patients was 0.02 cm,the maximum value was 2.30 cm,and the maximum head and foot displacement was(0.78± 0.54)cm,and the 3D displacement vector was(0.98 ± 0.55)cm.The head and foot displacement and 3D displacement vector of the lower lobe tumor were statistically significant(t=-3.09,P=0.003;t=-3.26,P=0.002);There was no correlation between 3D displacement vector and tumor volume(r=0.21,P=0.11).There were no significant differences in X-axis direction,Y-axis direction,Z-axis direction and three-dimensional displacement vectors between men and women and squamous carcinoma and adenocarcinoma carcinoma,(P>0.05).2 There were 60 patients with ITV-M/ITV-S greater than ITV-A/ITV-S,and the difference was not statistically significant(Z=-1.03,P=0.30).Volume comparison between ITV-M and ITV-S,ITV-A and ITV-S: upper lobe group:(Z=-0.27,P=0.78;Z=-0.768,P= 0.44),lower lobe group:(Z=-1.685,P=0.092,Z=-2.14,P=0.033),Comparing the volume of ITV-A and ITV-S in lower lobe group,the difference was significant.(P<0.05),the rest was not statistically significant(P>0.05).Correlation analysis was performed to find that the ratio of ITV-M to ITV-S was positively correlated with the 3D displacement vector(r=0.3,P= 0.02),and there was no significant correlation between the ratio of ITV-M to ITV-S and the volume of GTV(r=0.16,P= 0.23).Conclusions 1 The central displacement of tumor GTV in different lung lobes and directions is obviously different.The displacement of inferior lobe tumors in head-foot direction was markedly greater than that in left-right and anterior-posterior direction.2Compared with ITV-A,the volume of ITV-M is closer to that of ITV-S formed by the fusion of GTV of 10 respiratory phases obtained by 4D-CT.However,the proximity of tumor density to tumor should be taken into account,which may lead to the increase of the sketch error of target area.Figure 7;Table 8;Reference 97. |
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