To investigate the use of a thick microchannel plate as a converter to detect and locate 511 keV photons, we have performed model calculations to optimize hole size, spacing and glass material. The results indicate a potential for greater than 10% detection efficiency for microchannel plates of 1 cm thickness and 50% lead content, with 75 μm holes spaced on a lattice of 100 μm. Higher efficiency would be achieved with higher lead content. Such detectors would be operated in a low gain mode with a conventional microchannel plate of gain about 10 5 in proximity. This detector system should be capable of millimeter spatial resolution and nanosecond timing accuracy. These results are sufficiently promising that we suggest a small scale prototype be developed to explore applications in physics and in medical imaging.