Background: Intraoperative ultrasound (iUS) imaging has emerged as a promising adjunct in glioma surgery with both, 2-dimensional (2D) as well as navigated 3-dimensional (n3D), modes increasingly being used.
Methods: We analyzed our decade-long experience of 1075 brain tumor (807, 75% gliomas) cases operated using iUS. A retrospective chart and electronic records review was performed. The primary aim was to understand the patterns of use of iUS mode and its purpose of application (as a localizing tool or as a resection control modality) as well as to evaluate its impact on the extent of resection.
Results: The use of iUS increased over time, especially with the introduction of n3DUS though 2DUS remained the more commonly used mode (63%) overall during this period. For biopsies (156 cases), both 2D, as well as n3D iUS, were used as a localizing tool only. Lesion localization was the major purpose for use of iUS even for tumor resections (61%). Resection control was performed more often for gliomas (46.5% compared to 16.5% in non-glial tumors). n3DUS was the preferred modality as a resection control tool irrespective of histological class. GTR (gross total resection) was achieved in 53.1% cases overall, while in glial and non-glial tumors it was 44.7% and 80.7%, respectively. GTR was higher when iUS was used as a resection control modality. The US and MR defined EOR (extent of resection) showed substantial agreement (κ = 0.678) with high diagnostic accuracy of 84% for glial tumors. In glial tumors, iUS was used more often in eloquent tumors and GTR rates were slightly higher than when iUS was not used.
Conclusion: iUS is a versatile tool and is a useful surgical adjunct for glioma surgeons. Besides its proven benefit as a localizing tool, when used as a tool for resection control it improves the resection rates. n3DUS may offer benefits over 2DUS as a resection control modality, though the evidence is still evolving.
Keywords: 2D ultrasound; Intraoperative ultrasound; clinical utility; extent of resection; glioma; navigated ultrasound.