A New Component Approach to Efficiency Normalization for 3D PET

Efficiency normalization corrects the non-uniform response of the 3D PET detector due to the scanner´s geometry, non-uniformity of the crystals, and gain variation in the photomultiplier tubes. In reviewing the literature, most component approaches to detector efficiency normalization are applied to the block design ring scanner. In this paper, we propose a new component normalization method for Philips´ non-block design ring scanner, where the normalization mainly consists of two components, the crystal efficiency and the detector geometry. The derivation is based on the physics model of the measured data, along with a wheel-sum assumption, so that the crystal efficiency is separated from the model and both terms are estimated independently. The crystal efficiency is calibrated using a uniform cylinder phantom. A minimum least-square estimation method is used to smooth the noisy crystal efficiency. The detector geometry is calibrated using a stationary uniform plane phantom, since it is independent of the projection ray´s azimuthal angle. The result is then applied with a radial solid angle correction to compensate for the unusual geometry of the plane source. Finally, this technique is validated using a uniform cylinder phantom reconstruction along with scatter and attenuation correction