二次污染物
脑转移瘤好发于 ["A．大脑皮层","B．小脑皮层","C．大、小脑皮层","D．脑髓质","E．皮髓质交界区"]
一次污染物
女，25岁，癫痫，CT示侧脑室旁多发低密度灶，结节样或块状增强。最大可能是 ["A．转移瘤","B．脑囊虫","C．脑脓肿","D．多发性硬化","E．髓鞘形成异常"]
男，36岁，头痛，癫癎，CT示脑实质多数高密度点状影和0．5～1cm圆形低密度灶，呈环形增强。最可能的诊断是 ["A．多发性硬化","B．脑脓肿","C．结节性硬化","D．脑囊虫病","E．病毒性脑炎"]
污染物的转化
