Coplanar Indirect-Navigated Intraoperative Ultrasound: Matching Un-navigated Probes With Neuronavigation During Neurosurgical Procedures. How We Do It.

BACKGROUND: Intraoperative ultrasound (IOUS) is becoming more and more adopted in neurosurgery, since it has been associated to greater extent of resection (EOR) and to gross total resection (GTR) during brain tumor surgery. IOUS main limitations are spatial resolution, width and orientation of the field of view and scan quality, which are operator-dependent. Furthermore, most neurosurgeons are not confident with this technique, which needs a long learning curve in order to identify and interpret anatomic structures.
OBJECTIVE: To describe an effective procedure to take advantages of both IOUS and neuronavigation in case of lack of a navigated ultrasound system.
METHODS: We propose a reliable "indirect-navigated" technique which is based on the optical tracking of un-navigated IOUS probe by the use of a multipurpose passive tracker and a proper configuration of common neuronavigation system.
RESULTS: Navigated IOUS is not available in all neurosurgical operating rooms but ultrasound systems are common tools in many hospital facilities and neuronavigation systems are common in almost all the neurosurgical operating rooms. The proposed indirect-navigated technique shows some paramount advantages: since almost all the neurosurgical operating rooms are provided with a neuronavigation system, the only tool needed is the ultrasonography. Therefore, this procedure is largely accessible and costless, reliable, and may improve the neurosurgeon's ability in ultrasonographic anatomy.
CONCLUSION: This technique is based on the coplanar and coupled use of both un-navigated IOUS probe and standard optical neuronavigation, in order to allow the intraoperative navigation of IOUS images when a navigated ultrasound system is not available. © Congress of Neurological Surgeons 2021.