Son SM, et al. - A retrospective cohort study was conducted to analyze fluorine-18 sodium fluoride (¹⁸F-NaF) PET/computed tomography (PET/CT) findings in patients with inflammatory low back pain and evaluate the utility of this modality in the diagnosis of ankylosing spondylitis (AS) according to the Assessment of SpondyloArthritis International Society (ASAS) criteria. Researchers recruited a total of 68 individuals who had undergone ¹⁸F-NaF PET/CT imaging between April 2015 and April 2017 for evaluation of inflammatory low back pain. Researchers characterized AS-positive lesions on PET/CT as symmetric sacroiliac joint uptake that suggests sacroiliitis, syndesmophytes on the spine, and enthesopathy at any site. They applied ASAS criteria to examine all individuals and these were assigned to either the AS or the control group. The study defined diagnostic criteria of AS on PET/CT images as ¹⁸F-NaF PET/CT images with at least one of AS-positive findings. The results of this study displayed that ¹⁸F-NaF PET/CT showed significantly different findings between the two groups according to the ASAS criteria and is beneficial for diagnosing AS.