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Objective: To use the simulation is repeated CT scans to evaluate the three-dimensional suitable for the treatment of non - small cell lung cancer radiotherapy , primary tumor tumor volume size , shape and surrounding tissue changes , to analyze the basic law of the tumor volume of the primary tumor in radiotherapy treatment its law curve . Provide the basis for the clinical treatment of lung cancer enhance target radiotherapy dose and reduce normal tissue dose . Methods : 14 cases from 2009.10-2010.09 pathologically or cytologically confirmed locally advanced non-small cell lung cancer (NSCLC) patients with a median age of 59.5 years (47 to 83 ) , 12 males and 2 females , clinical stage Ⅲ a- III B ; split dose of 2.0 ~ 2.2Gy / times / day , 5 times / week , median total dose of 60Gy ( 58 to 64) . All patients after three simulated CT scan . First repeat scan a median dose of 30Gy (26 ~ 34), the second repeat scan median dose 50Gy (46 ~ 50.6). Recording each scan when the primary foci tumor volume and treatment time . :0-30Gy ,30-50Gy ,0-50Gy average retreat during volume was (35.23 ± 43.36), (22.38 ± 22.07), (57.60 ± 56.07) cm3. 0-30Gy ,30-50Gy ,0-50Gy during daily average retreat volume (cm3 / d) , respectively ( 1.70 ± 2.10) , ( 1.75 ± 1.48 ) , ( 1.74 ± 1.77 ) cm3 / d . 0-30Gy ,30-50Gy ,0-50Gy during the retreat average percentages were ( 25.74 ± 18.69 ) , ( 17.46 ± 10.98 ) , ( 43.24 ± 15.72 ) % . 0-30Gy ,30-50Gy ,0-50Gy average retreat rate (% / d) for the period were ( 1.24 ± 0.95 ) , ( 1.39 ± 0.79 ) , ( 1.28 ± 0.48 ) % / d . Paired T-test , patients enrolled in the 0-30Gy during withdrawal volume ( cm3 ) during the 30-50Gy , the average daily withdrawal volume ( cm3 / d ) flinch percentage (% ) flinch rate (% / d) there is no difference , T values ??were 1.21, -0.12,1.18 , -0.38 , P value 0.25,0.91,0.26,0.71 . Conclusion: The patients enrolled during the 0-30Gy flinch rate ( % / d ) during the 30-50Gy flinch percentage ( % ) , the shrinking volume ( cm3 ) flinch volume / day (cm3 / d) there is no difference . Found that three-dimensional conformal radiotherapy in the average tumor volume of the primary tumor progressive decline at a constant rate , when these changes occur , can be timely modify the treatment plan to improve the therapeutic gain ratio .
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