Abstract: A greatly reduced number of scintillation cyrstal/PMT gamma ray detectors are employed in a ring array about a PET image volume. Because of the relatively small number of such detectors, the complexity and expense of associated electronic signal processing channels is greatly reduced (even if each such channel is provided with sophisticated time of flight capabilities). Similarly, because relatively fewer crystals are employed, it becomes possible to use much larger and faster response time scintillation crystals so as to greatly increase gamma ray detection efficiency and scatter rejection while also permitting the electronic circuits to better reject random events and to provide effective time of flight image data filtering.