Brain operations guided by real-time two-dimensional ultrasound: new possibilities as a result of improved image quality

In 1995, a project was initiated in Trondheim, Norway, to investigate various possibilities for more frequent use of ultrasound in brain surgery. Since that time, the quality of ultrasonic images has improved considerably through technological adjustment of parameters. The objective of the present study was to explore essential clinical parameters required for the successful use of ultrasonic guidance in brain surgery. During the study period, several surgical setups designed to optimize the use of intraoperative real-time two-dimensional ultrasonic imaging were explored. These included various positions of the ultrasound probe in relation to both the operation cavity and the lesion, as well as the position of the operation channel in relation to the gravity line. All lesions from the latest period (1997-2001; n = 114) were depicted well by ultrasound imaging, with the exception of two cases. High image quality and direct image guidance of the tool were maintained best throughout the operation by imaging through an intact dura and at an angle relative to a vertical operation channel. All tumor operations were performed without complications, and ultrasound imaging was found to be an important factor in the detection of remaining tumor tissue at the conclusion of surgery. For 14 low vascular tumors, the operation was guided only by ultrasound imaging. No bleeding complications occurred. A method of minimally invasive ultrasound-guided evacuation of hematomas was developed. In 19 patients, the method was found to be efficient (i.e., >90% of the hematoma was evacuated) and without complications, except for one patient who experienced rebleeding. With proper planning and surgical setup, ultrasound imaging may provide acceptable image quality for use in image-guided brain operations.