Development and Performance Characterization of Intraoperative Positron Probes for Tumor Surgery

The emergence of promising specific tumor-seeking agents labeled with positron emitters is giving rise to a renewed interest for radioguided surgery using beta probes. Intraoperative positron probes present intrinsic advantages over gamma detection to provide real time information about the tumor extend and the assessment of reasonable surgical resection margins. In that context, we are currently developing two different intraoperative positron probes based on SiPM photosensors: a small positron imaging probe to perform tumor localization and post-operative control of the surgical cavity, and a miniaturized counting probe to guide in real time the excision of the lesion. We report here design and characterization of the performance of these probes. The imaging probe consists of the stack of two SiPM arrays coupled to a plastic and a GSOZ scintillators in order to remove the gamma ray background noise with a subtraction method. The counting probe is built around seven detection elements, each composed of a plastic scintillating fiber and a SiPM, and is designed to be directly coupled to an excision tool. We show that the imaging probe offers submillimetric intrinsic resolution and bias over its usable field of view. These performances are insensitive to temperature variations due to a real-time temperature-compensated circuit integrated in the readout electronics. The positron sensitivity measured with 18F-FDG (12.6 cps/nCi) is superior to those of the best positron probes reported. Detailed description of the first prototypes of the two positron probes as well as complete characterization of their performances, including evaluation of the gamma ray rejection efficiency with realistic phantoms, will be presented at the conference