NIMG-66INTRAOPERATIVE UPDATE OF RESIDUAL TUMOR VOLUME WITHOUT ADDITIONAL IMAGING: A NEW SOFTWARE TOOL FOR SKULL BASE SURGERY

BACKGROUND: Intraoperative knowledge about extent of resection (EOR) and correlation with eloquent neuronal and vascular structures is important in skull base tumor surgery, especially when complete removal is not feasible and a combination with radiosurgery/radiotherapy is planned. Currently, ultrasound, computed tomography or magnetic resonance imaging (iMRI) are modalities to assess EOR during surgery. Their use, however, is restricted by limited availability and costs, interruption of workflow, and data interpretation. Purpose of this prospective single-institutional study was to objectify EOR online without the need for additional intraoperative imaging. METHODS: Adult patients undergoing neuronavigated resection of complex skull base tumors were included between September 2014 and March 2015. Entire tumor volume, anticipated residual tumor volume and risk structures were segmented on preoperative 3-dimensional high-resolution MRI. A navigated tool was used to register online the resection cavity and to update the segmented tumor objects in neuronavigation. Simulated EOR was visualized and quantified online during surgery. Data from final update were correlated with results from postoperative MRI as primary end point. Secondary end point was the surgeons' impression of the usefulness for intraoperative decision making. RESULTS: 16 patients (6 male; mean age: 54.6 years) were included (14 meningiomas, 1 clival chordoma, and 1 chondrosarcoma of the petrous bone). Segmentation of objects took 11 min/patient (median). Extent of resection was virtually determined during resection between 1 and 9 times. Complete resection was achieved in 1 patient, and between 22% to 95% tumor removal in the remainder. Correlation with postoperative MRI showed good accordance with simulated residual tumor tissues with a mean conformity index of 1 (range 0.92-2.2). CONCLUSION: The software is easy to use, offers accurate information about residual tumor volume and can be integrated smoothly into the surgical work-flow. These data can serve for online calculation of appropriate treatment plans for radiotherapy/stereotactic radiosurgery.