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During glioblastoma surgery, delineation of the brain tumor margins is difficult because the infiltrated and normal tissues have the same visual appearance. We use a fiber-optical fluorescence probe for spectroscopic and time domain measurements to assist surgeon in differentiating the healthy and the infiltrated tissues. First study was performed on rats that were previously injected with tumorous cells. Measurements of endogenous tissue fluorescence were performed on fresh and fixed rat tumor brain slices. Spectral characteristics, fluorescence redox ratios and fluorescence lifetime measurements were analyzed. The study aimed at defining an optical index that can act as an indicator for discriminating healthy from tumorous tissue.

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The survival outcome of patients suffering from gliomas is directly linked to the complete surgical resection of the tumour. To help the surgeons to delineate precisely the boundaries of the tumour, we developed an intraoperative positron probe with background noise rejection capability. The probe was designed to be directly coupled to the excision tool such that detection and removal of the radiolabelled tumours could be simultaneous. The device consists of two exchangeable detection heads composed of clear and plastic scintillating fibres. Each head is coupled to an optic fibre bundle that exports the scintillating light to a photodetection and processing electronic module placed outside the operative wound. The background rejection method is based on a real-time subtraction technique. The measured probe sensitivity for (18)F was 1.1 cps kBq(-1) ml(-1) for the small head and 3.4 cps kBq(-1) ml(-1) for the large head. The mean spatial resolution was 1.6 mm FWHM on the detector surface. The gamma-ray rejection efficiency measured by realistic brain phantom modelling of the surgical cavity was 99.4%. This phantom also demonstrated the ability of the probe to detect tumour discs as small as 5 mm in diameter (20 mg) for tumour-to-background ratios higher than 3:1 and with an acquisition time around 4 s at each scanning step. These results indicate that our detector could be a useful complement to existing techniques for the accurate excision of brain tumour tissue and more generally to improve the efficiency of radio-guided cancer surgery.

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