| Objective: the aim of this study is To evaluate the contribution of three exposure methods of esophageal cancer radiotherapy, Comparising routine three field iso-center irradiation(RT),three dimensional conformal radiotherapy(3D-CRT)and intensity medulated radiotherapy (IMRT) in the control of target area exposure dose and protection of perifocal normal tissues by using three dimensional treatment plan system(3D-TPS).And use kodak EDR2 film,Verifing esophageal cancer conformal and intensity modulated radiation therapy treatment planning target tumor dose distribution, comparing the advantages and the feasibility of the two planning.Methods: Twelve patients with pathologically proved mid-lower esophageal cancinoma underwent RT,3D-CRT and IMRT with total dose of 50Gy,above three kinds of radiotherapeatic methods were designed based on CT locating images.the difference of exposure doses between target area and critical organ was compared by treatment plan(TP)and dose volume histogram(DVH). use somatic me,CT scan simulation positioning system and TPS treatment plans ,the three planning are developed. Patients use his hands to cling to first, is fixed with stereotactic frame and vacuum bag , marked In the surface , enhanced CT scan. In order to more clearly show lesions before scanning oralling diluted meglumine diatrizoate about 50 ml, 5 mm slice thickness throughout the mediastinum continuous scanning. CT images via CD-ROM input Sichuan University Fonics C TPS treatment planning system (TPS). At the same time referencing light-barium esophagus and Esophagoscopy examination records,physicians, physical division and the CT diagnosis of doctors Outlined gross tumor volume (GTV), and the clinical target volume (CTV), the plan target volume (PTV) and the organs at risk (OAR). For Conformal and intensity modulated designed 5 ~ 8 coplanar or nocoplanar conformal field, with 90% isodose curve including PTV and this as a prescription dose ,the dose of PTV internal differences≤±5%, dose of threatening organ in its tolerance limits. And implementing 3D-CRT and IMRT planning in the linear accelerator, in the plexiglass phantom centre Shooting films of field test, comparing the relative level of centres dose distribution.Results: The results of conventional (RT), 3-dimensional conformal (3D-CRT), intensity modulated conformal radiation therapy (IMRT) 95% of the volume PTV were 41.55±3.62Gy, 44.45±2.14 Gy, 46.36±2.49 Gy, p <0.05 , there are statistically significant, 95% volume GTV doses of 42.04±1.90 Gy, 46.42±1.62 Gy, 49.25±1.43 Gy, P <0.05, there are statistically significant, 3D-CRT and IMRT than conventional radiotherapy; three radiotherapy plan target conformal index were 0.41±0.03,0.72±0.04,0.95±0.03, to IMRT for the best (P <0.05); three plans PTV dose variability index for 7.74±0.66,4.50±0.50,3.20±0.47 to variation of intensity modulated minimum, P <0.05; dose prescription coverage GTV volume percentage of the size of 26.41±5.61%, and 53.41±7.28%, and 77.36±6.20%, to plan for the intensity-modulated best, is significant, P <0.05; three plans lung V20 volume ratio were 19.63±1.92%, and 12.59±2.66%, and 10.75±2.30%, 3D-CRT, IMRT reduced the lungs V20 (P <0.05). Three of the spinal cord plan by the largest volume of 21.93±9.67 Gy, 18.06±9.17 Gy, 16.74±8.77 Gy to IMRT for the smallest, but P> 0.05, no significant; heart 1 / 3 by volume respectively 15.15±9.60 Gy, 9.75±6.78 Gy, 9.15±7.41 Gy, both in the tolerance range , IMRT for the smallest, P> 0.05, with no statistical significance. Test results showed that: conformal and intensity modulated can better protect organs at risk, for intensity modulated to best, target dose distribution for the intensity-modulated, and intensity of superior conformal.Conclusion: for the target conformal degree and target dose ,3D-CRT and IMRT are superior to RT and can reduce the exposure dose of perifocal sensitive organs. simultaneously, can limit the exposure dose of normal tissue into tolerant range,and IMRT are the best.
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