胰腺癌的预后比较差，其外科治疗是目前唯一有效的方法，但是许多病人已处于晚期阶段。在手术中常可见到肿瘤侵犯到后腹膜和肠系膜上静脉（SMV）或门静脉（PV），这种侵犯影响了治疗效果。因此在外科手术前判断肿瘤是否已侵犯到PV／SMV及侵犯的程度是很重要的。螺旋CT是一种新 The prognosis of pancreatic cancer is relatively poor, and its surgical treatment is currently the only effective method, but many patients are already in advanced stage. During surgery, tumors often invade the posterior peritoneum and superior mesenteric vein (SMV) or portal vein (PV). This violation affects the therapeutic effect. Therefore, it is important to judge whether the tumor has invaded PV/SMV and the degree of invasiveness before surgery. Spiral CT is a new