  X-ray is a ubiquitous imaging modality in clinical diagnostics and industrial
inspections, thanks to its high penetration power. Conventional x-ray imaging
system, equipped with energy-integrating detectors, collects approximately 1000
to 10000 counts per pixel to ensure sufficient signal to noise ratio (SNR). The
recent development of energy sensitive photon counting detectors opens new
possibilities for x-ray imaging at low photon flux. In this letter, we report a
novel photon-counting scheme that records the time stamp of individual photons,
which follows a negative binomial distribution, and demonstrated the
reconstruction based on the few-photon statistics. The projection and
tomography reconstruction from measurements of roughly 10 photons shows the
potential of using photon counting detectors for dose-efficient x-ray imaging
systems.
