A Preliminary Study On Target Motion Of Esophageal Cancer During Normal Respiration With Four-dimensional Computed Tomography

Objective:To investigate the motion characteristics of cervical and upper chest primaryesophageal cancer with four-dimensional computed tomography.Methods:Twenty patients with esophageal carcinoma underwent respiration-synchronized4D-CT simulation during free breathing,mapping the GTV0-GTV90,lung and hearton every patient,s each subsequent CT image of10images in the full-respiratoryphase,and measuring the displacement of each center of GTV,the volume of the GTVand lung.These displacements and direction were analyzed on different segments ofesophagus.Results:The average movement amplitude of GTV centroid were（0.169±0.083）cm,（0.167±0.095） cm and(0.521±0.319)cm in right-left,anterior-posterior,superior-inferior direction,respectively(H=24.198,P=0.000).Themotion in right-left, anterior-posterior,superior-inferior direction were（0.110±0.040）cm,（0.083±0.0379）cm and（0.143±0.115）cm in the cervical segment（H=0.829，P=0.661),（0.108±0.054）cm,（0.164±0.089）cm and（0.408±0.171）cm in theupper segment（H=9.360，P=0.009),（0.209±0.078）cm,（0.189±0.100）cm and（0.663±0.309）cm in the middle segment respectively（H=21.500，P=0.000).Thedisplacement of cervical and upper chest esophageal tumor in superior-inferiordirection is more notable than in right-left and anterior-posterior direction in eachsegment (P＜0.05).The displacement of cervical and upper chest esophageal tumor inright-left, anterior-posterior and superior-inferior direction is different in differentsegment of esophageal carcinoma(P＜0.05). The displacement of GTV centroid ineach direction is not entirely consistent.The maximum displacement of GTV centroidin each direction was in T50(end-expiratory) phase when T0(end-inspiratory) phaseas the reference phase.Conclusions:(1) The displacement of cervical and upper chest tumor in superior-inferiordirection is more notable than in right-left and anterior-posterior directions.(2) Thedisplacement of tumor in different directions in the same segment of esophagealcarcinoma is different. While the displacement of tumor in the same directions is different in different segment of esophageal carcinoma. So individual and segmentalis necessary for definition of internal target volume margin for esophagealcarcinoma.(3) The maximum displacement of GTV in each direction was in T50(end-expiratory) phase when T0(end-inspiratory) phase as the reference phase.