Intraoperative ultrasound imaging: practical applicability as a real-time navigation system.

Experience with the use of Intaoperative Ultrasound (US) imaging as real time navigation system in neurosurgery is presented and discussed. Since 1987 we have performed US routinely in a wide variety of intracerebral and intramedullar pathologies. In this analysis we define useful intraoperative applications. Accurate definition of deep-seated lesions and their delineation from surrounding anatomical structures is possible with an US frequency of 5 MHz. Small subcortically located lesions can clearly be visualized with a high frequency probe. Differentiation between solid tumor, cyst and necrosis can be delineated. Identification of residual tumor is difficult. Dural sinuses and eventual invading tumor can be visualized by a 10 MHz probe. US guidance can be helpful for puncturing with a catheter, needle or endoscope. Postoperative percutaneous US imaging through a burr hole did not prove to be useful. The intraoperative use of US imaging is a reliable method for determining the size, shape and localization of lesions. It can be used as a practicable, cost effective and timesaving real time navigation system.