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ObjectiveTo investigate the infra-fractional motion characteristics of thoracic primary esophageal carcinoma in the upper,middle and below segment with four-dimensional computed tomography (4DCT),and provide sufficient data to make reasonable internal target volume(ITV) of primary esophageal carcinoma and clinical target volume(CTV).Materials and methods1.From May2009to Feb2011, Twenty-five patients with thoracic primary esophageal carcinoma (7upper,13middle,5below) proved by histology or cytology, received respiratory gated4D CT imaging with Real-time Position Management system under quier respiration, then ten images reconstructed under the guide of respiratory signal and transmitted to the Varian Eclipse8.6treatment-planning system. Then one single radiation oncologist to map the gross tumor volume (GTV) on each subsequent CT image of10images in the full-respiratory phase based on standard of esophageal wall≥5mm, then set up one bone-reference point easy to be identified and measuring the displacement of each centre of GTV relative to the bone-reference point. These peak displacements and directions were analized correlation with patient tumor and respiratory characteristics.2.From May2010to April2010, Six patients with normal esophagus received respiratory gated4D CT imaging with Real-time Position Management system under quier respiration.Then seven point of thoracic esophagus was selected to measure the motion of each centre of point as oppose to the mean value, record the peak displacement of x,y and z axis and analyse characteristics of seven points’ displacement,so as to know the extent of normal esophgus’movement for supporting the making of reasonable ITV for the CTV or shrunken GTV.Results1.The mean total lung volume was3301.47±926.01cm3and2708.78±827.26cm3in the male and female, and3010.17±934.25cm3、3334.97±947.95cm3respectively on end-expiration and end-inspiration(significant difference statistically).The mean total lung volume was2918±508.25cm3,3192.35±481.5cm3;3128.11±1076.36cm3,3499.36±1103.77cm3and2832.56±1035.5cm3,3107.21±1003.02cm3respectively on end-expiration and end-inspiration in the upper segment, middle segment and below segment(significant difference statistically).The mean total gross tumor volume(GTV) was39.03±35.27cm3and22.71±15.96cm3in the male and female, and35.29±32.7cm3、34.76±32.3cm3respectively on end-expiration and end-inspiration (no significant difference statistically t=-0.82,P=0.935).The total mean peak to peak displacement of thoracic primary GTV was0.67±0.58mm,0.53±0.3mm,1.67±1.17mm respectively in the x-axis, y-axis and z-axis. The most displacement is5.38mm in the z-axis.The motion of x-axis, y-axis and z-axis in the upper segment is0.36±0.16mm,0.43±0.33mm and0.75±0.64mm,0.64±0.39mm,0.56±0.29mm,1.8±0.98mm in the middle segment,1.16±0.99mm,0.59±0.3mm,2.65±1.3mm in the below segment. The displacement of left, right, anterior, posterior, superior and inferior is0.32±0.16mm,0.41±0.17mm,0.44±0.4mm,0.41±0.29mm,0.89±0.81mm,0.61±0.45mm in the upper,0.73±0.47mm,0.54±0.28mm,0.54±0.3mm,0.57±0.29mm,1.93±0.96mm,1.66±1.03mm in the middle, and1.01±0.65mm,1.31±1.32mm,0.6±0.28mm,0.58±0.36mm,2.51±1.17mm,2.79±1.55mm in the below. The motion of upper,middle and below is0.36±0.16mm,0.64±0.39mm, and1.16±0.99mm in the x-axis,0.43±0.33mm,0.56±0.29mm, and0.59±0.3mm(F=1.082, P=0.347) in the y-axis, and0.75±0.65mm,1.8±0.98mm, and2.65±1.3mm in the z-axis.2.The total mean peak to peak displacement of thoracic normal esophagus was1.44±1.34mm,1.42±1.21mm,3.73±2.77mm respectively in the x-axis, y-axis and z-axis. The total displacement of left, right, anterior, posterior, superior and inferior is1.32±0.83mm,1.58±1.7mm,1.46±1.44mm,1.37±0.92mm,3.69±2.39mm,3.77±3.13mm in the thoracic normal esophagus.Point one:The mean peak to peak displacement of esophagus was 1.78±3.04mm,0.43±0.23mm, Omm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is0.95±0.71mm,2.61±4.26mm,0.39±0.24mm,0.48±0.24mm, Omm, Omm in the first point of thoracic normal esophagus.Point two:The mean peak to peak displacement of esophagus was1.12±0.45mm,1.5±2.27mm,3.17±3.41mm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is1.19±0.6mm,1.05±0.29mm,2.0±3.25mm,1.0±0.43mm,3.12±2.82mm,3.21±4.19mm in the second point of thoracic normal esophagus.Point three:The mean peak to peak displacement of esophagus was1.5±0.8mm,0.98±0.64mm,2.68±0.92mm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is1.72±0.98mm,1.28±0.57mm,0.85±0.32mm,1.1±0.87mm,2.72±0.83mm,2.63±1.08mm in the third point of thoracic normal esophagus.Point four:The mean peak to peak displacement of esophagus was1.2±0.73mm,1.29±0.67mm,3.75±0.89mm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is0.99±0.74mm,1.42±0.72mm,1.31±0.58mm,1.27±0.81mm,3.45±0.7mm,3.7±1.11mm in the fourth point of thoracic normal esophagus.Point five:The mean peak to peak displacement of esophagus was1.31±0.92mm,1.25±0.39mm,5.57±2.62mm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is1.3±0.87mm,1.32±1.06mm,1.14±0.34mm,1.36±0.44mm,5.11±1.3mm,6.02±3.59mm in the fifth point of thoracic normal esophagus.Point six:The mean peak to peak displacement of esophagus was1.34±0.61mm,2.69±1.16mm,6.58±2.35mm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is1.04±0.33mm,1.65±0.7mm,2.57±1.29mm,2.81±1.12mm,6.28±1.86mm,6.89±2.91mm in the sixth point of thoracic normal esophagus.Point seven:The mean peak to peak displacement of esophagus was1.88±1.06mm,1.77±0.42mm,4.55±1.43mm respectively in the x-axis, y-axis and z-axis. The mean peak to peak displacement of left, right, anterior, posterior, superior and inferior is2.05±1.1mm,1.72±.1.11mm,1.97±0.42mm,1.57±0.33mm,5.18±1.14mm,3.93±1.51mm in the seventh point of thoracic normal esophagus.The mean peak to peak motion of point one, point two, point three, point four, point five, point six and point seven of normal thoracic esophagus is1.78±3.04mm,1.12±0.45mm,1.5±0.8mm,1.2±0.73mm,1.31±0.92mm,1.34±0.61mm and1.88±1.06mm in the x-axis,0.43±0.23mm,1.5±2.27mm,0.98±0.64mm,1.29±0.67mm,1.25±0.39mm,2.69±1.16mm, and1.77±0.42mm in the y-axis, and Omm,3.17±3.4mmmm,2.68±0.92mm,3.58±0.89mm,5.57±2.62mm,6.58±2.35mm and4.55±1.43mm in the z-axis.The data of normal esophagus showed that the peak to peak displacement is similar in the x-axis,is more notable in the point six and point seven in the y-axis,is more notable in the point five and point six in the z-axis.And will be more helpful in making reasonable inner tumor volume of clinical tumor volume or shrunken gross tumor volume,be hopeful in decreasing total radiation dose of organ at risk.Conclusions4DCT can provide more precise results of inner tumor volume when measuring the motion of esophageal tumor. The displacement of z axis is more notable than x, y axis. The closer to abdomen,the greater the displacement of esophageal primary carcinoma. The motion of x axis and z axis should be more taken into account in making inner tumor volume of thoracic esophageal carcinoma. And more consideration, including4DCT or other imaging methods, should be given in defining reasonable and individual ITV for precise radiotherapy of thoracic esophageal carcinoma.It is different in the motion of different point in the normal thoracic esophagus,and data showed the displacement is more notable than the esophageal primary carcinoma’s, especially more greater near the diaphragma in the y axis and z axis.When making the ITV of GTV, the displacement of normal esophagus should be considered as the ITV of CTV or shrunken GTV at the same time,so the data about the displacement of normal esophagus would greatly support the more reasonable and more individual ITV of CTV or shrunken GTV, hopeful to decline the side-effect of radiation therapy in the esophageal carcinoma.
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