Technical and Methodological Aspects of Whole-body MR-PET
The diagnostic benefits of simultaneous magnetic resonance-positron emission tomography (MR-PET) have been explored since the first whole-body MR-PET scanner was installed in 2010. Since then, various clinical and research questions have been addressed and, in most cases, PET-computed tomography (CT) and sequential magnetic resonance imaging (MRI) and PET scans have been used as a reference. Multi-parametric data from both modalities complement and supplement each other for an accurate personalised diagnosis, prognosis and evaluation of therapy. In addition to processing the increased amount of information, given the accurate co-registration between the two modalities, many research studies have been devoted to exploiting MRI information to improve PET image quality compared to standalone PET systems. However, for simultaneous MR-PET studies, the combination of the PET and MRI techniques represents a challenge from both a technical point-of-view and practicability. In this chapter, we describe some of the advantages and issues for PET data corrections associated with the combination of both systems as one single scanner in whole-body studies. Some of these problems were initially solved through relatively simple approaches or simply ignored when the first MR-PET systems were established. Since then, important developments in PET data correction and image reconstruction, as well as in tailored, novel MRI sequences, have taken place and are steadily being integrated in newly installed MR-PET systems to be used in clinical routine. These advances in software development are paralleled by improvements in the scanner hardware integration.