2006 年 19 巻 1 号 p. 25-28
In brain tumor surgery using the ultrasonic monitoring technique, surgical instruments such as microdissectors and suction tubes create imaging artifacts. In addition, recognition of the correct position of the suction tube tip under ultrasonic monitoring is difficult because conventional 2D ultrasound creates similar images regardless of the scanning position along the tube. The backscattering-like artifact from these surgical instruments is caused by ringing vibrations generated on the tube by the ultrasonic monitoring pulse. We have attempted to suppress this type of artifact in vivo using a suction tube covered with a high-attenuation heat-shrinkable coating devised on the basis of in vitro experiments, and confirmed that this was effective. To identify the position of the suction tip on the ultrasound image, 1.4-μm-radius microcapsules having a hard plastic shell were attached to the metal tube tip. The microcapsules vibrate in synchronization with the ultrasound monitoring pulse and regenerate harmonic signals, based on the same principle as contrast agents used in ultrasound imaging. By using the 2nd harmonic imaging method, the metal tube tip was found to be selectively emphasized on the ultrasound image. It is anticipated that these improvements will make intraoperative ultrasonic monitoring a more powerful tool for brain tumor surgery.
