A system and method for imaging a subject includes a clock that generates
a clock signal and a radiation source that directs photons through the
subject in response to the clock signal. A detector system is included
that detects the photons and a memory module records a time of detection
of the photons by the detector system with respect to the clock signal.
The system includes a processor that calculates a time of flight (TOF) of
the photons from the radiation source to the detector system and compares
the TOF to a reference TOF to determine a delay in the TOF attributable
to the photons passing trough the subject.