Delineation of brain tumor margins using intraoperative sononavigation: implications for tumor resection

Sonography has been employed for real-time intraoperative delineation of tumor boundaries during resection of brain tumors. However, the variably hyperechoic appearance of brain edema or gliosis surrounding the brain may interfere with accurate depiction of tumor margins. The goal of the present study was to use sononavigation, which provides coregistration between real-time sonograms and MRI scans, to assess the accuracy of sonographic determination of tumor margins.

Sononavigation was performed on 12 brain tumors (7 metastatic brain tumors, 2 meningiomas, 1 anaplastic oligodendroglioma, 1 anaplastic pilocytic astrocytoma, and 1 anaplastic astrocytoma). Sonograms of tumor margins were categorized into 1 of 3 types: in type 1, the tumor margin was clearly visualized and corresponded to the margin of the enhanced lesion on MR scan in all areas; in type 2, the tumor margin was clearly seen in some areas but was obscure in others due to hyperechoic edema; and in type 3, the tumor margin was indistinguishable from surrounding tissues in all areas.

Three metastatic brain tumors and 1 meningioma were categorized as type 1. Three metastatic brain tumors, 1 meningioma, and 1 anaplastic oligodendroglioma were categorized as type 2. The anaplastic pilocytic astrocytoma, 1 metastatic brain tumor (which consisted mainly of necrotic tissue), and the anaplastic astrocytoma were categorized as type 3. These data assist in determining whether the sonographic appearance of tumor margins is accurate and whether to rely on information from either sonography (type 1) or the sononavigation system when resecting tumor types 1, 2, and 3.

Sononavigation can help categorize the sonographic tumor margins into 3 different patterns, and this categorization can assist in determining which imaging modalities are needed to better delineate the tumor margins for subsequent resection.