gms | German Medical Science

Recently, a variety of image guided ultrasound systems has been developed. Technically, so called two platform solutions with an external high-end ultrasound system introduced into neuronavigation systems offer an optimum of intraoperative images (fused to preoperative data sets). However, the fused images of such systems consist of a gray-scale to gray-scale fusion and thus provide only restricted intraoperative information, because the surgeon may not be able to judge which part of a fused image is derived from a preoperative data set and which part may be related to the intraoperative ultrasound image. Therefore, we developed a novel one platform image guided ultrasound system that addresses this problem. This report describes our experience with its use for the treatment of subcortical lesions.

The ultrasound system is directly integrated into the neuronavigation system (VectorVision², BrainLAB, Germany) by the navigation software (VV Cranial, BrainLAB, Germany). Its probe has a frequency range from 5.0 to 7.5 MHz and a penetration depth up to 120mm (IGsonic, BrainLAB, Germany). A precalibrated array is mounted to the probe and tracks the the ultrasound image plane. The preoperative gray-scale data set is fused to intraoperative green-scale ultrasound images.

We operated on 22 patients suffering from cortical or subcortical lesions (14 gliomas, 8 cavernomas) using the above described technique. The novel ultrasound probe visualized all tumors. The fusion to the preoperative images was carried out without technical problems. In 7 patients with low grade gliomas and 2 patients with high grade gliomas the fused images were difficult to read, when a gray-scale to gray-scale fusion was carried out. In 7 of these difficult 9 patients and the 13 other patients a gray-scale to green-scale fusion delivered highly optimized images that contributed to the (1) tumor margin definition, (2) transsulcal approach planning, and (3) tumor resection control. In 20 of 22 patients (91%) a gray-scale to green-scale fusion offered highly valuable intraoperative images.

Gray-scale to green-scale fusion offers additional intraoperative image information in the majority of cortical and subcortical tumors, particularly during surgery for low grade gliomas. Once introduced into clinical practice, it may routinely contribute to more individually tailored approaches and an optimized tumor resection.