3D ultrasound based neuronavigation in neurosurgery: A Clinical Evaluation

Abstract

  Background and objectives:

Intraoperative ultrasound has been used for decades in neurosurgery for localization and characterization of pathology, particularly tumors. Furthermore, with Doppler imaging localization of vascular structures is also possible. Neuronavigation was developed as a tool for planning neurosurgical procedures and localization of lesions during surgery. Displacement of brain tissue during the course of surgery, called brain shift, is however recognized as a major source of inaccuracy in neuronavigation, and because of this intraoperative imaging is important for maintaining application accuracy in neuronavigation. A neuronavigation system with integrated 3D ultrasound, enabling intraoperative ultrasound imaging for use in navigation has been developed. The aims of this dissertation were to assess the clinical value of neuronavigation based on intraoperative 3D ultrasound and explore different applications of the technology.

Methods:

Five studies were performed, resulting in five papers (1-5):                                                                                                                                                                  

1. A study comparing 3D ultrasound image findings with histopathology in the tumor border zone in three subsequent phases of tumor resection.                                                                                                                                                              2. A study assessing the use and value of 3D ultrasound angiography in patients with supratentorial tumors.                                                                                                                                                                                                                                      3. A study exploring the feasibility and technical aspects of navigated 3D ultrasound for image guidance in spinal cord surgery.                                                                                                                                                                         4. A study evaluating navigated 3D ultrasound for image guidance of neuroendoscopic procedures.                                                                                                                                                                     5. A study exploring stereoscopic display in image guided AVM surgery, using preoperative MRI angiography and intraoperative 3D ultrasound angiography.

 

Results:

 

 • 3D Ultrasound was found to accurately delineate tumor borders prior to resection, but it tended to overestimate tumor during resection and underestimate tumor after having completed the resection. On the other hand, residual tumor was rarely missed during resection.

 •The application of navigated 3D ultrasound angiography was found useful in tumor cases with important vessels close to the tumor.

•Navigated 3D ultrasound was found feasible for the use in spinal cord tumor surgery.

•In neuroendoscopic procedures, image guidance based on intraoperative 3D ultrasound was found useful, particularly for inserting the endoscope in cases with small and narrow ventricles and orientation in cases with anomalous anatomy.

•Stereoscopic display of AVMs using 3D ultrasound angiography image data in some cases was of sufficient quality for interpretation. Updated imaging with 3D ultrasound angiography allowed for more accurate localization of feeder vessels and in one case residual AVM was identified.

 

Conclusions:

In this thesis, neuronavigation based on intraoperative 3D ultrasound and 3D ultrasound angiography has been evaluated in different clinical settings. Some limitations of the current ultrasound technology have been identified for delineation of tumor borders in subsequent stages of resection. Neuronavigation based on intraoperative 3D ultrasound angiography may have a place in some brain tumor cases, and in AVM surgery although further development is needed to increase image quality, particularly in the latter case. In spinal cord tumor surgery, neuronavigation with 3D ultrasound is feasible. Image guidance by intraoperative 3D ultrasound may increase safety in some neuroendoscopic procedures with small and narrow ventricles and anomalous anatomy.

Overall, 3D ultrasound in neuronavigation seemed to be useful in a range of clinical settings. Some limitations and issues for further development and research have been identified. With knowledge of the limitations, and in selected cases, neuronavigation based on 3D ultrasound may serve to increase the safety of the procedure and improve patient outcome.