Methods Three dots was measure in the CT films by using compasses and cast to the patient head to locate the puncturable points.

• 方法利用大分规两臂张开时的跨度可容纳球形物体的凸面,从而对头颅CT片上各靶点、线间距离进行测量,并投射至患者的头颅上进行穿刺定位。