PET/MRI of the heart.

Hybrid imaging devices including PET/CT and SPECT/CT have seen a great success in clinical routine, especially in the field of oncology. With the recent advent of PET/MRI scanners, expectations that PET/MRI would replicate that success were accordingly high. The combination of molecular imaging with a variety of very specific PET tracers and the high spatial resolution of MRI are expected to result in increased diagnostic accuracy or even in the creation of additional demands for hybrid imaging. However, as these systems have entered the market just recently, experience in the field of nuclear cardiology is limited and some applications still need to be validated. Owing to the profound technical differences between CT and MRI, which influences not only the estimation of the photon attenuation but also causes marked differences in the workflow, particularly in cardiovascular studies (such as the need for special personnel training and interaction between nuclear medicine specialists, radiologists, and physicists), the "familiarization phase" with this new technique also seems to be extended. However, the approach to study various conditions such as perfusion, viability, and atherosclerosis in a single imaging examination session using PET and MRI offers advantages. Although MRI allows for a detailed morphologic characterization of the studied tissue, PET adds the information on functional biological markers that are not (or at least not fully) measurable by MRI. Thus, this combined imaging approach will prove valuable in distinct cardiac diseases (such as myocarditis and cardiac sarcoidosis) and will offer vast research opportunities.