Supercollimating photonic crystal scintillators We demonstrate that nanophotonic scintillators based on three-dimensional (3D) photonic crystals can overcome the longstanding tradeoff between spatial resolution and light yield in X-ray imaging. By engineering supercollimation, which is light propagation without angular spreading, within the emission spectrum, we strongly shape the angular emission profile of the scintillator, dramatically reducing blurring at large thicknesses. Our theoretical and numerical results, using realistic scintillator and photonic crystal parameters, show that this improves the Detector Quantum Efficiency (DQE) by up to several orders of magnitude at high spatial frequencies, enabling sharper images and reduced X-ray dosages. This approach offers a new path toward high-resolution, low-dose X-ray imaging systems. PC13910 SPIE