NaF PET fused with MRI, metacarpophalangeal joint, horse

Transverse (left), sagittal (middle) and dorsal (right) plane images of a sodium fluoride positron emission tomography (NaF PET) evaluation coregistered with an MRI of the metacarpophalangeal joint in a horse that responds to low 4-point diagnostic analgesia. Lateral is to the left of the transverse and dorsal plane images. Dorsal is to the left of the sagittal image. Note the rounded region of avidity in the axial aspect of the subchondral bone of the palmaromedial MCIII condyle, compatible with subchondral bone injury. This lesion may have been visualized on specialized radiographic projections but likely incompletely characterized. This lesion was detected on the MRI; however, the PET evaluation indicates that this lesion has an active component and was ultimately confirmed to be the cause of this patient’s lameness.