美国报告儿童原发性恶性脑瘤发病率从1973年到1994年增长了35％。这引起了公众对环境中化学物质作用的关注，而另一解释就是从1985年后影像诊断技术的进步及广泛应用。Smith（JNailCancerlust1998；90：1269－1277）研究报告的1973年至1994年的发病率，认为这种增长最好的解释 The United States reported a 35% increase in the incidence of primary malignant brain tumors in children from 1973 to 1994. This has aroused public concern about the role of chemicals in the environment. Another explanation is that since 1985, advances in imaging diagnostic techniques have been widely used. Smith (JNail Cancer 1998; 90: 1269-1277) reported the incidence of the disease from 1973 to 1994 and considered this explanation of the best growth