Positron emission tomography: a horse in the musculoskeletal imaging race.

Positron emission tomography (PET) has established itself as a pertinent tool in equine musculoskeletal imaging in the last few years. With the ability to provide functional information regarding both bone and soft tissues, PET has found several clinical applications in horses. PET is currently used in horses as an enhanced bone scan, providing high-resolution 3-dimensional information, in particular for imaging of the racehorse fetlock. Combined with CT and MRI, PET is particularly pertinent in horses for the assessment of subchondral bone and enthesis. The development of a dedicated PET scanner to image the distal limb of horses with standing sedation led to new applications, where PET is used as a first-line advanced imaging tool, in particular for foot, fetlock, and tarsal imaging. A complimentary clinical review of when to seek advanced imaging in equine athletes can be found in the companion Currents in One Health by Garrett in the July 2022 issue of the Journal of American Veterinary Medical Association. The clinical use of PET in human medicine remains mainly focused on oncological imaging; however, numerous small-scale clinical studies have demonstrated valuable applications for musculoskeletal imaging. These include assessment of foot and ankle pain, osteoarthritis of the knee and hip, osteoporosis, response to bisphosphonates, and chronic osteomyelitis. The use of musculoskeletal PET in dogs remains quite limited, but a few studies have recently been published and clinical interest is growing. The available research data and clinical applications between horses, humans, and dogs are currently quite disparate, but all suggest great promises for earlier and more accurate clinical diagnosis, as well as better understanding of pathophysiology and response to treatment. Translating knowledge from a species to another will undoubtedly help further growth of musculoskeletal PET.