Abstract：Objective To investigate the setup errors of super chest segment of esophageal cancer patients before radiotherapy delivery by KV cone beam CT, and evaluate the margin from CTV to PTV. Methods From 2010 to 2012, 13 patients with super chest segment of esophageal cancer whose IMRT planning CT images were included in this study. Delineate target on the CT images of treatment planning and enlarge the margin of CTV to form ITV,then enlarge the margin of ITV gradually 10 times by 1 mm each time to form varied PTV,and create the plan according to the size of the PTV, simulate setup errors in the new plan to obtain the simulation of the actual exposure curve and find a suitable PTV to assure 95% ITV volumeas ever to approach the prescription dose, obtained the outside enlarge distance of CTV→PTV. ResultsThe maximum setup errors in the direction of the anterior and posterior positioning was (3.42±2.19) mm. The margin of ITV→PTV is 5 mm which was figured out by PTV enlarging method. Compared to the original plan that under the condition of draw up the radiotherapy plan that based on the method of PTV enlarging obtained the CTV→PTV and simulate the actual dose distribution according to the setup errors:total lung V5, spinal cord D1cm3 ,increased by about 0.87%, 4.95 Gy, heart V40, PTV D95, PTV V100, ITV D95, ITV V100 were reduced about 0.62%, 4.95 Gy, 8.38%, 1.84 Gy, 1.87%, all of them have statistically difference. Conclusions Range of external expansion of the left to right, superior to inferior and anterior to posterior is 7 mm,8 mm and 7 mm respectively, according to the method of PTV enlarging obtained the margin of CTV→PTV of super chest segment of esophageal cancer patients.
ZHANG Yong-xia,ZHAI Fu-shan,LIU Ming et al. The setup errors and reasonable target margin in radiotherapy of superior chest segment esophageal carcinoma[J]. Chinese Journal of Radiation Oncology, 2013, 22(6): 489-492.
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2013, Vol. 22 
