This issue of PET Clinics focuses on PET/MRI: Advances in Instrumentation and Quantitative Procedures. Articles will include: Advances in clinical PET/MRI instrumentation; Magnetic resonance imaging-guided attenuation correction of positron emission tomography data in PET/MRI; Magnetic resonance imaging-guided partial volume correction of positron emission tomography data in PET/MRI; Magnetic resonance imaging-guided derivation of the input function for PET kinetic modeling; Innovations in small-animal PET/MRI instrumentation; Dual-modal PET/MRI molecular imaging probes; Magnetic resonance imaging-guided motion compensation of positron emission tomography data in PET/MRI; Attenuation correction for MR coils in combined PET/MR imaging; and more!