| Objective: The study intends to use the4D-CT (four-dimensionalcomputed tomography) positioning technology to discuss it’s effect in thetarget region of esophageal, and compare the target volume and dosimetrydifferences between3D plan and4D plan, In the research we evaluate theadvantages of the4D plan in geometry and dosimetry, and discuss it’s clinicalsignificance in the esophageal cancer radiotherapy. At the same time, comparethe two target volume differences in the presence of oral contrast agents locaterespectively before and after scanning and then evaluate the significance of themethod in esophageal GTV sketching.Methods:19patients with staged I-III esophageal was chosen. Eachpatient completed3D-CT scan fist of all, soon afterwards oral administrationof5%iohexol, and underwent the3D-CT simulation scans followed by4D-CT simulation scans in the context of the vessel enhanced. Sketch3D planof gross tumor volume （GTV）and normal organs in the ordinary3D-CT;sketch internal gross tumor volume（IGTV）in4D-CT’s each level of10respiratory phase one by one and saved at the image of20%sequence, andregion of normal organs were delineated on the20%sequence too. Usingthree-dimensional treatment planning system based on PTV3D, PTV3DE,PTV4D, design three sets of radiotherapy plan for each patient:3D plan,3DCplan and4D plan. PTV3D and PTV3DE respectively were generated by scanCT ordinary and reinforcement CT pictures in GTV outside enlarge around0.5cm, upper and lower external3cm to CTV, and then expanded to including0.5cm,in order to contain the respiratory motion and equipment error; PTV4Dconsists of ever10CT image sequence in4D-CT phase sketch of IGTV,surrounded by expanding0.5cm,upper and lower external3cm to CTV and expanding0.5cm,to include equipment error. The prescription dose and thebeam mode of the three sets of plans are same. In the study we compare thetarget volume, target displacement and normal organ dosimetry’s differencesin the3D plan and4D plan, and compare the target dosimetry’s variation in the3D plan and3DC plan. At the same time compar to oral contrast agent volumebefore and after GTV, named GTV3D,GTV3DE respectively，the evaluate tothe method in esophageal GTV sketch of practical significance.Result:1Comparison of volume target1.1The average volume of GTV3D is46.94土34.47cm~3,GTV3DE is47.54土35.18cm~3.There were9cases of GTV3DE volume smaller than thevolume of GTV3D,10cases of GTV3DE larger than GTV3D volume. The Ztest statistics is-1.489, bilateral probability is P=0.136.According to theα=0.05, that oral administration of iohexol solution has no effect on targetvolume of esophageal carcinoma.1.2The median volume of PTV3D is178.05(115.91)cm~3,PTV3DE is175.67(127.74)cm3,PTV4D is195.19(150.80)cm3.There was1case ofPTV4D volume smaller than the volume of PTV3DE,18cases of PTV4Dlarger than PTV4D volume. The Z test statistics is-3.300, bilateral probabilityis P=0.001.According to the α=0.05,PTV4D volume larger than the volume ofPTV3D was statistically significant. The volumes of PTV4D were greater thanthe volume of PTV1.the Z test statistic is-3.823,bilateral probability isP=0.000. According to the α=0.05, PTV4D volume larger than the volume ofPTV3D was statistically significant.2Comparison of X,Y,Z direction2.1Middle esophageal carcinoma: Tumor target of respiratory movingaverage degree in X,Y,Z direction on the average displacement respectivelywas0.25土0.26cm(range:0.04-0.59cm),0.04土0.38cm(range:0.00-0.80cm)and0.10土0.15cm(range:0.00-0.37cm),the three-dimensional direction onlyX direction displacement has significantly difference(P=0.014),Y,Z directionare not statistically significant(P=0.776,P=0.932). 2.2Under esophageal carcinoma: The tumor in the X direction of mediandisplacement is0.02(0.36)cm(range:0.05-0.69cm),the Y direction on theaverage displacement is0.25土0.69cm(range：0.15-1.65cm),the Z direction ofmedian displacement is0.05(0.27)cm(range:0.00-0.87cm),but the threedirections are not statistically significant(P=0.722,0.307,0.208).3Comparison of dosimetry target area:V100-3D Plan and V100-3DCPlan respectively are95.69土0.94%、88.62(9.84)%,V100-3DC Plan ratherV100-3D Plan is reduced by9.44土7.50%（P=0.000）,there are significantdifferences.V95-3D Plan and V95-3DC Plan respectively are99.79(0.26)%，95.17(6.20)%,V95-3DC Plan rather V95-3D Plan is reduced by6.21土6.19%（P=0.001),the difference is statistically significant.V90-3D Plan andV90-3DC Plan respectively are99.99(0.03)%,97.19(3.78)%,V90-3DC Planrather V90-3D Plan is reduced by about4.26%（P=0.000）,the difference isstatistically significant.4Comparison of dosimetry lung as organ4.1V5-3D Plan<V5-4D Plan,V5-4D Plan pulmonary V5than3D planincreased by2.05％(P=0.016),there are significant differences.4.2It and V5evaluation results are similar,compare two plans V20volume percent,V20-3D Plan<V20-4D Plan,V20-4D Plan more V20-3D Planincreased by1.06％（P=0.018）,there are significant differences.4.3Comparing two plans V30volume percent,V30-3D Plan<V30-4DPlan,V30-4D Plan more V30-3D Plan increased by0.64％（P=0.083）,thereare not significant difference.4.4MLD-4D Plan more MLD-3D Plan increased by47.00士105.89cGy（P=0.069）,there are not significant difference.5Comparison of dosimetry heart as organ:MHD-4D Plan moreMHD-3D Plan increased by218.58士283.888cGy（P=0.004）,there aresignificant differences.Conclusion:1Oral contrast agent in CT simulation, can not only clearly displayed thelocation of the esophagus in the body and its corresponding structure, but also can combine the CT mage and the contrast esophagography, which provides amethod for accurate outline of target area. In addition this study showed thatthe method does not increase the volume of GTV, so it can be used in thelocalization of esophageal cancer.2Esophageal cancer radiation therapy should be considered respiratorymobility on the impact of its target area, especially may cause leakage, thePTV should include the region caused by respiratory movement ofindividualized target location to move outside the boundaries of the expansion.34D-CT positioning technology can pass the sketch within the targetarea to determine individual outside the border, and to effectively avoidmissing target, improve precision radiotherapy.4D-CT positioning technologyby setting individualized target to replace the conventional outside the targetarea, protects the lung, heart, spinal cord, groups such as radiation resistance,as far as possible ensure the tumor is not missing and developed a space fortumor dose increasing.44D-CT radiotherapy plan does not endanger organs such as lung, heart,spinal cord by volume. |
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