Contribution from random coincidences to PET images: the effect of detector "wobbling"

The effect of gantry "wobbling" motion on the distribution of random coincidences was examined in a ring positron emission tomograph. It was shown by computer simulations and by experiments using a single photon emitter that an asymmetric source distribution may lead to characteristic ripples in the projections, appearing as ring artifacts in the images. A new correction scheme is proposed, in which the wobbling effect on the random distribution is estimated in peripheral detector channels.