The`edge-ona illuminated microchannel plate (MCP) position-sensitive detector (PSD) is used for gamma-ray imaging for the "rst time. The superior position resolution of the MCP is combined with high detection e$ciency due to the`edge-ona illumination mode. The results of imaging a 15 Ci Cs source (662 keV quantum energy) are presented.2001 Elsevier Science B.V. All rights reserved. [4,5,9] are installed at the input face of the detector to provide an image of the radioactive sources. Position-sensitive photomultipliers [1,4,6}9] and charge-coupled devices (CCD) [3,5] are used as readout systems for the scintillators. Plate-like detectors are also used for the scanning and locating (but not imaging) of the radioactive sources [13].The applications of hard X-ray position-sensetive detectors (PSDs) in medicine are described in detail in review [14]. Although the parameters of E-mail address: pms@peterlink.ru (P.M. Shikhaliev).hard radiation PSDs are continuously optimized, there is a fundamental limitation: increasing the position resolution leads to decrease of detection e$ciency. At the same time, it is well known that microchannel plate (MCP) detectors provide a superior position resolution but the detection e$ciency of conventional MCP detectors is low for the hard radiation [15,16].Recently, we have suggested a novel hard X-ray detector based on MCPs that provides a higher hard X-ray detection e$ciency in comparison with conventional MCP detectors [17,18]. The`edgeona illumination of the MCP has been used to combine the superior position resolution of MCP with high detection e$ciency. It has also been predicted that the positon-sensitive performance of thè edge-ona MCP detector may be used for the hard X-ray imaging systems. Note that this`edge-ona illumination concept has also been applied for silicon strip detector [19] and CCDs [20].

The`edge-ona illuminated microchannel plate (MCP) position-sensitive detector (PSD) is used for gamma-ray imaging for the "rst time. The superior position resolution of the MCP is combined with high detection e$ciency due to the`edge-ona illumination mode. The results of imaging a 15 Ci Cs source (662 keV quantum energy) are presented.