An intraoperative beta probe dedicated to glioma surgery:: Design and feasibility study

Surgery is considered as the primary therapeutic procedure for gliomas and several recent clinical studies have shown that total tumor resection is directly associated with longer survival when compared to subtotal resection. In order to refine the resection in the boundaries of gliomas, we are developing an intraoperative probe specifically dedicated to the localization of residual tumor labeled with positron emitters. The probe is designed to be compact and electrically safe in order to be directly coupled to the excision tool leading to simultaneous detection and removal of tumor tissues. It is built with clear and plastic scintillating fibers held in a closed packed annular arrangement ensheathing the excision tool. The annihilation - ray background is eliminated by a real-time subtraction method. Validation of the technical choice and optimization of the probe geometry were performed by preliminary measurements and Monte Carlo simulations based on the MCNP-4C code and an anthropomorphic brain phantom. The theoretical probe sensitivity was found to be 82 cps/mu Ci/ml with a gamma ray rejection efficiency of 99.6%. The expected minimum radiotracer detectable concentration for tumors labeled with F-18-FET was 0.10 mu Ci/ml. When compared to the 0.29 mu Ci/ml average concentration in the bulk of the tumor, this result demonstrate the potential ability of the probe to define more accurately the extent of brain tumor resection.