PET/MRI: Concepts and Clinical Applications
The concept of merging structural and molecular imaging originated in the early 1990s, nearly a decade before the advent of single photon emission computed tomography/computed tomography (SPECT/CT) in 1998 and positron emission tomography/CT (PET/CT) in 2000 [1,2]. These developments in hybrid imaging paved the way for later innovations, including PET/magnetic resonance imaging (PET/MRI). Although CT and MRI play comparable roles as structural imaging modalities within these hybrid systems, there are distinct advantages and disadvantages to each of them. MRI is favored in terms of safety, particularly in pediatric and pregnant patients, as it utilizes radiowaves and magnetism rather than ionizing radiation, thereby avoiding the potential risk of mutagenic and carcinogenic side effects. Furthermore, MRI demonstrates superior contrast for visualizing soft tissues and benets from the ability to acquire functional information through specialized techniques including diffusion-tensor imaging, diffusion-weighted imaging, MR elastography, MR spectroscopy, and perfusionweighted imaging . When combined with PET, MRI has the ability to greatly enhance image reconstruction, partial volume correction, and motion compensation. On the other hand, it also presents challenges related to electromagnetic interference between the PET and MRI systems. This chapter will briey explore the design of modern hybrid PET/MRI systems and review their potential clinical applications.