Improvement of continuous position sensitive diode performances and associated electronics

In contrast to position segmented detectors, continuous Position Sensitive Detectors (whose localisation is based on current division) remain of interest when count rate is not critical. That is the case with several imaging applications in nuclear medicine and biology. Continuous PSDs offer large detection areas (up to 60/spl times/60 mm/sup 2/) and a spatial resolution inversely proportional to the energy deposited. Therefore, when coupled to an image intensifier tube, their spatial performances are suited to g medical diagnosis. After a brief presentation of the /spl gamma/ compact camera developed and dedicated to localised the sentinel lymph-node; we recall briefly the principle of the 3 kinds of PSD. Then, we describe a simulation model developed using CAO AWB/Cadence which taking into account both detector and readout electronics. In our application, a duo lateral photodiode filtered with a trapezoidal spectroscopy amplifier achieves the best compromise between linearity and spatial resolution. Because a signal deficit appears when PSD is coupled to a classical charge preamplifier, an impedance adaptation which improves detection performances is presented.