“Volume-Mapping”—A New Model for Intraoperative Data Acquisition during Endoscopic Sinus and Skull Base Surgery

Introduction: With the exception of open MRI there is one disadvantage of all intraoperative image-guided navigational systems: the situation displayed always shows the situation at the time of data acquisition prior to the surgical procedure. As of today no system exists to adapt and adjust image data displayed on the monitors, in analogy and proportional to tissue masses removed during surgery. A true intraoperative update of CT- or MRI-data has the disadvantages of either an interruption of the surgical procedure, additional irradiation dose, and/or questionable accuracy due to simultaneous display of blood, coagula, edema, and possibly, packing material. In addition, those updates might be required several times during a single procedure in one patient.

Conclusions: “Volume-Mapping” is based on a new software development: all points “visited” by the tip of navigational instruments can be marked and stored. These can be displayed on demand and shown in triplanar as well as 3-D display on the monitor on the actual scans. In an ideal situation the entire surgical field can thus be color-coded indicating with high accuracy whether or not, for instance, the periphery of a tumor has been reached and whether all niches, cells, and recessus of the paranasal sinus system have been opened. This system is not influenced by the presence of blood clot, edema, packing material, and so on. Though not 100% perfect yet, this technique at present appears to be the best way to update intraoperative image data without time loss and/or additional irradiation. The system has significantly helped to achieve complete and precise resection of adenoma, especially in endoscopic pituitary surgery, particularly when using CT- and MR-data fusion for navigation.