PET/MR Tomographs: A Review with Technical, Radiochemical and Clinical Perspectives

In the last decade, an increasing number of positron emission tomography / magnetic resonance (PET/MR) tomographs were installed and many clinical studies were performed in the neurological field.Although PET/MR has many favorable properties to support the application in brain imaging, attenuation correction, and therefore accurate quantification, is a problem that still requires optimal solution.In this review we have summarized the three main methods that are currently used to correct attenuation in PET/MR, namely atlas- or template-based methods, segmentation-based methods, and reconstruction-based methods. There is currently active ongoing research to refine available methods and improvements are reasonably expected in the next years. Clinical studies using PET/MR focused mainly on neurodegenerative and neurooncological disorders. PET/MR hybrids tomographs provided promising scientific results and were logistically more convenient for patients. Additionally, in order to explore all potential clinical benefits of this hybrid technology, the design and development of multimodal contrast agents has constantly increased the attention of radiochemists. Many PET/MR dual probes have been already devised, particularly in the nanotechnology field, sometimes preceding the identification of a clear diagnostic application in medicine.In the near future, we predict more clinical studies as the availability of PET/MR will further increase and new tracers for neurodegenerative disorders will accept broader clinical acceptance.