We present a new, handheld system for in vivo detection of radiotracers. The detection is based on scintillators coupled to Silicon Photomultipliers (SiPMs) and aimed at direct positron detection. The battery-powered system is wire-lessly connected to a PC. A graphical user interface allows controlling the probe functions and monitoring count rates, battery voltage and temperature. The probe is fully compatible with standard sterilisation procedures and has been successfully used in pre-clinical trials with human cancer patients. The use of the probe requires that the patient be administered a dose of the radiopharmaceutical F-18-fluorodeoxyglucose (FDG), a beta(+) emitting glucose analogue used for detecting tumours in oncology, which can still be detected during the operation. (C) 2011 Published by Elsevier Ltd.