Researchers in the U.S. and Japan have demonstrated the first experimental cross-sectional medical image that doesn’t require tomography, a mathematical process used to reconstruct images in CT and PET scans. The work, published in Nature Photonics, could lead to cheaper, easier, and more accurate medical imaging. The advance was made possible by development of ultrafast photon detectors, said the paper’s senior author Simon Cherry, professor of biomedical engineering and radiology at the University of California, Davis. “We’re literally imaging at the speed of light, which is something of a holy grail in our field.” In the paper, researchers describe various tests they conducted with the new technique, including on a test object that mimics the human brain. They say they are confident that this procedure is ultimately scalable to the level needed for clinical diagnostics, and has the potential to create higher-quality images using a lower radiation dose. Images can also be created more quickly with this method, potentially even in real time during the PET scan, as no after-the-fact reconstruction is needed. PET scans are currently expensive and are technically limited, as the full information present in the travel time of the annihilation photons is not captured by current clinical scanners.