ABSTRACT
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In the last years, quantitative imaging for preclinical as well as for clinical use became more and more important, mainly in oncology but also in neurology and cardiology. PET and SPECT are imaging modalities facilitating quantitative in vivo measurements. For exact quantification, several effects degrading the acquired data have to be taken into account. Some of these effects, such as detector efficiency, partial volume effects, photon attenuation and scatter, are found in SPECT as well as in PET imaging. In contrast, the collimator-detector response occurs only in SPECT and random coincidences or limitations due to positron range are specific for PET. This chapter
describes these effects. Potential compensation methods are discussed in the following chapters.
