Predictive value of semi-quantitative index from F-18-fluoride PET/CT for treatment response in patients with ankylosing spondylitis.

Purpose: We aimed to investigate whether the lesion-to-background ratio (LBR) of the whole spinal column in ankylosing spondylitis (AS) patients based on baseline F-18-fluoride positron emission tomography/computed tomography (PET/CT) is associated with treatment response.

Methods: Twenty-eight male patients with a wide range of disease activity were included in this study. Abnormal bone metabolic lesions on baseline F-18-fluoride PET/CT were visually assessed in three areas: anterior discovertebral units (DVUs) and posterior joints (cervical, thoracic, and lumbar facet joints, costovertebral joints, and costotransverse joints) of vertebrae and sacroiliac joints of the sacrum.