ABSTRACT
Department of Nuclear Medicine and European Institute of Molecular Imaging, University of Mu¨nster, Mu¨nster, Germany
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5.2 Decay correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5.3 Randoms correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.3.1 Singles-based correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.3.2 Delayed window correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5.4 Attenuation correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.4.1 Stand-alone emission tomography systems . . . . . . . . . . . . . . 77 5.4.2 PET/CT and SPECT/CT systems . . . . . . . . . . . . . . . . . . . . . 80 5.4.3 Attenuation correction artifacts . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.5 Scatter correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.5.1 Energy windowing methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5.5.2 Analytical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 5.5.3 Direct calculation methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 5.5.4 Iterative reconstruction methods . . . . . . . . . . . . . . . . . . . . . . . . 95
5.6 Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
The physical basis of both emission tomography technologies, PET (positron emission tomography) and SPECT (single photon emission computed tomography), is the fact that many atomic nuclei are not stable; they decay into other nuclei under the emission of specific radiation (radioactivity), a property that was first discovered by Henri Becquerel in 1896 while investigating the fluorescence of uranium compounds. In emission tomography, two fundamental decay modes are of particular interest: the beta+ decay for PET and the gamma decay for SPECT.
