A method and system for nuclear imaging normally involves detection of energy by producing bursts of photons in response to interactions involving incident gamma radiation. The detector sensitivity is increased by as much as two orders of magnitude, so that some excess sensitivity can be exchanged to achieve unprecedented spatial resolution and contrast-to-noise (C/N) ratio comparable to those in CT and MRI. Misplaced pileup events due to scattered radiation are rejected for each of the central groups to reduce image blurring, thereby further improving image quality. The reduction in detector thickness minimizes depth-of-interaction (DOI) blurring as well as blurring due to Compton-scattered radiation. The spatial sampling of the detector can be further increased using fiber optic coupling to reduce effective photodetector size. Fiber-optic coupling also enables to increase the packing fraction of PMTs to 100% by effectively removing the glass walls.