颈、胸上段食管癌MLC照射野的剂量学研究

Assessment of Dose Distribution of the Cervical and Upper Thoracic Esophageal Cancer in the Treatment Using the Multileaf-collimater

目的研究颈、胸上段食管癌使用MLC技术照射的剂量学特点。方法14例经病理证实的颈、胸上段食管癌患者,行常规模拟定位制定常规治疗计划,并以此计划的照野中心为中心行CT扫描,用MLC技术设计第2种方案,同时将资料传入ADAC计划系统设计三维适形方案。将此3种方案的有关参数进行比较。结果肿瘤长度的检查结果:钡透和内镜结果相近(P=0.108)、与CT比较有差异。常规模拟定位的中心与肿瘤的GTV中心在X、Y、Z轴上相差3.4、8.1、5.9 mm。以等中心点归一,给与处方剂量60 Gy/30F,3种照野所覆盖的肿瘤体积占GTV的36%、94%、100%,占CTV 23%、85%、92%。3种照野的100%GTV体积剂量分别为45、586、2 Gy。V 20分别为13.6%、13.5%、12.7%。结论常规模拟定位难以满足颈、胸上段食管癌放疗的剂量要求。使用MLC技术的照野可以达到和适形照野相同的靶区剂量分布,建议使用但应注意脊髓的剂量。

Objective To evaluate the dose distribution by the treatment using multileaf-collimater beams on the patient of the cervical and upper thoracic esophagral cancer. Methods Forteen cervical and upper thoracic esophageal cancer patients, who were diagnosed with endoscopy, biopsy and x-ray, were immobilized and simulated by conventional simulator and CT simulator, the centres of the conventional fields（planl） were marked and were compared to those of the GTVs which were delineated on the CT simulator. At the same time the beams（plan2） decided with CT-sim and using multileaf-collimater were set. so did the three dimensional conformal radiationtreatment （plan3） which were made on ADAC system with the images transferred through the LANTIS local network from the CT-sim, then assess the outcomes. Results The lenth are differed by examinations with x-ray,endoscopy and CT scan, the deviations of the centre of field along X, Y and Z axis are 3.4,8, 1 and 5.9 mm. by prescription dose 60 Gy/30F, the covered part of GTV and CTV are 36% ,94% ,23% and 85% ,92%,100%. The 100% volume dose of GTV are respectively 45,58, 62 Gy. the V20 of the lung are 13.6 %, 13,5%, 12, 7%. Conclusion Conventional simulation cannot reach the desire of dose distribution, the beam using multileaf-collimater are suggested because the dose distribution can match that of the three dimensional conformal radiationtreatment＇s,but it＇s high dise on spinal cord should be mentioned the same time.