食管癌CT扫描在放射治疗中的价值

Value of CT Scan on radiotherapy of esophageal cancinoma

目的研究CF扫描所示肿瘤大小的准确性，依此以肿瘤为射野中心，采用合理的照射野方法1993－12／1996－12病理和CT扫描的食管癌患者77例.取3个层面，绘制并测量相应照射野的大小及正常组织的受量．结果CT所示肿瘤的大小与手术标本比较P＞0．05.放疗组的肿瘤各径线均大于手术组.非对称性浸润，以管腔为射野中心，经典的照射野大小（前宽6．0cm，后斜野5．0cm），≥35．1％的患者90％的等剂量曲线不能包全肿瘤.如以肿瘤为射野中心，前野宽7．0cm，两后斜野为6．0cm，80．7％的患者80％～90％的等剂量曲线包全肿瘤、剂量分布均匀．如肿瘤直径＞5．1cm，先前后对穿野尔后采用分野的照射技术．采用容积-剂量百分比直方图，50％，20％肺最大受量体积分别为18％，49％该剂量临床上很少发生急性放射性肺炎结论证实了食管癌CT扫描的准确性和可靠性，应作为放疗前常规检查方法之一.定位应以肿瘤为中心，确保80％～90％的等剂量曲线包全肿瘤.应据CT所示肿瘤大小，外侵形状，灵活选择照射野.

AIM To use adequate irradiation Portals with the knowledge of tumors extent and pattern of invasion as shown on CT scans.METHODS From Dec. 1993 to Dec, 1996, 77 patients with pathologically proved esophageal cancer who had.pre-irrediational CT scans were treated. 9o% isodose curves were done on three CT sections.RESULTS The difference in dimension of the resected speimens and those shown on CT sections was insignificant statistically P > 0.05. When the esophageal lumen was taken as portal center with tumors unsymtrical invasion, the 90% isodose curves of the conventional portals in more than 35. 1% patients (anterior 6 cm, posterior oblique 5 cm) were unable to cover the whole lesion. With taking the tumor as the portal center, the width of the anterior portal should be 7cm, posterior oblique 6 cm, the 80% ~ 90% isodose curves in 80.7% petients were able to encompess the whole tumor. If the tumor size was > 5. 1cm,PerPendicular AP portals were ued first to deliver Dt 36Gy - 4oGy. Then, a rational converging beam technic was adapted. The 50%. and 20% doses received by the lung were 18% and 49% by volumepercent dose chart.CONCLUSION CT scan in esophageal carcinoma is reliable and accurate. The tumor center should be taken oo simulation in order to encompess tbo whole tumor by the 80% ~ 90% isodose curves. Selection of irradiation portal should be done according to the size and the silhouette of the tumor,