Development of new intraoperative positron probes to guide solid tumors surgery

Excision of cancerous tumors is a common procedure for the treatment of numerous cancers. The stake is to perform the most complete excision to prevent recurrences while preserving as much as possible surrounding healthy tissues. Positron detection is a well suited imaging modality for detection of tumor remains during excision because its strong spatial selectivity makes it insensitive to the noise coming from the non-specific accumulation of the radiotracer in healthy tissues located far from the detector, leading to a better sensitivity and a better signal-to-noise ratio than gamma photon detection. Its use for the control of excision implies however strong constraints on detector dimensions which must be easy to handle by the surgeon and easy to insert in tight surgical wound. A new generation of photodetectors called Silicon Photomultipliers (SiPMs) is particularly suited for this application because they present the compactness and robustness of silicon technologies and very good detection performances. My thesis aims to develop and characterize a new generation of new positron probes based on these photodetectors. Two prototypes of detectors with complementary roles were realized: the first one is an imaging device based on the assembly of two scintillators with one or two SiPMs arrays which allows to quickly make an image of tracer distribution along a wide surface of tissues. The second detector is a counting probe made of scintillating fibers associated with individual SiPMs through clear optical fibers and can be associated to the excision tool. It guides the surgeon tool to the tissues previously localized with the imaging probe. Characterization of the imaging probe showed its ability to detect small tumor remains (15 mg) with a submillimetric resolution. The counting probe showed a detection efficiency of 80%. (author)