PET mit einer doppelkopf-koinzidenzkamera: Untersuchungen zum streu- und störstrahlungsanteil unter simulierten klinischen bedingungen

The use of dual coincidence cameras for positron emission tomography (PET) allows to register extensive regions of the patient's body due to the large field of view (FOV). However, this increases the probability of detecting disturbing radiation from outside the FOV, including scatter and random coincidence. These factors cause reduced image contrast, system resolution, and, consequently, image quality. The aim of this study was therefore to quantify these fractions of detected radiation using an especially constructed whole-body phantom which simulates the accumulation of ¹⁸F in a tumor as well as in brain and bladder outside the FOV. In this set-up, different evaluation parameters were used, as well as two PET camera head fixtures with or without transversally oriented septa (axial frame, AF; or open frame, OF, respectively). Our investigations showed that the use of OF consistently results in the detection of a large fraction of quality reducing radiation. In addition, there was a marked dependence on evaluation parameters, which was not as pronounced in the case of AF. Thus, we recommend the use of AF in the majority of the cases, in spite of the observed lower sensitivity of the system.