Abstract: A pulse transmission scintigraphic imaging system for providing image data for attenuation correction and fiducial alignment. The system includes a shuttered photon flood transmission source, secured opposite an Anger gamma scintillation camera by an adjustable armature, a motorized photon-occluding shutter mechanism for producing photon pulses from the photons emitted by the flood source and a gating system for providing a signal to the gamma camera indicative of the presence of a photon pulse (shutter mechanism open) or the absence of a photon pulse (shutter mechanism closed).