POCI:: A compact high resolution γ camera for intra-operative surgical use

The development of a hand-held gamma imaging probe for inside body localization of small tumors is of first interest for radio-guided operative cancer surgery. In that context, we have developed a sub-millimeter spatial resolution, small field of view, gamma per-operative compact imager (POCI). It consists of a head module composed of a high resolution tungsten collimator and a YAP:Ce crystal plate, optically coupled to an intensified position sensitive diode (IPSD). We report here the essential imaging performance characteristics of the POCI camera (spatial resolution, position linearity, efficiency and energy response). These were obtained by studying the influence of the collimator and the crystal design to evaluate the optimal configuration. The present version of POCI has a 24 mm diameter usable field of view and an intrinsic spatial resolution of 0.9 mm to 1.2 mm FWHM at 120 keV. These good detection performance characteristics combined with the small size of the camera make the device well suited to provide intra-operative monitoring in several medical procedures, such as thyroid and breast tumor removal.