An Intraoperative $\beta ^{-}$ Detecting Probe for Radio-Guided Surgery in Tumour Resection

The development of the β <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> based radio-guided surgery aims to extend the technique to those tumours where surgery is the only possible treatment and the assessment of the resection would most profit from the low background around the lesion, as for brain tumours. To validate the technique, prototypes of the intraoperative β <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> probe have been developed. This paper discusses the design details of one of the prototypes and its tests performed in laboratory. In such tests particular care has to be taken to reproduce the surgical field conditions. The tests showed that the prototype under study has 70% efficiency on electrons with an energy threshold at 540 keV, a point-like resolution of 2.8±0.1 mm, and a sensitivity to photons lower than 1%. The tests also demonstrated, with an innovative technique to produce specific phantoms, that 0.5 ml residuals can be safely identified in 1 s with tumor-non-tumor ratio equal to 10.