Bone formation rather than inflammation reflects ankylosing spondylitis activity on PET-CT: a pilot study

Area of Science:

• Nuclear Medicine
• Radiology
• Rheumatology

Background:

• Ankylosing Spondylitis (AS) diagnosis and activity assessment can be challenging.
• Positron Emission Tomography - Computer Tomography (PET-CT) offers advanced imaging capabilities.
• [18F]FDG, [11C](R)PK11195, and [18F]Fluoride are PET tracers with potential for visualizing AS.

Purpose of the Study:

• To evaluate the utility of different PET tracers for imaging AS activity.
• To compare PET-CT findings with Magnetic Resonance Imaging (MRI) and conventional radiographs.
• To determine if AS activity is primarily reflected by inflammation or bone formation.

Main Methods:

• Ten AS patients underwent whole-body [18F]FDG and [11C](R)PK11195 PET-CT scans.
• Two additional AS patients received [18F]Fluoride PET-CT scans.
• All patients had MRI and conventional radiographs of the spine and sacroiliac joints for comparison.

Main Results:

• [18F]FDG and [11C](R)PK11195 PET-CT showed no significant uptake in AS patients.
• [18F]Fluoride PET-CT identified increased uptake in the vertebral column and sacroiliac joints, correlating with MRI and radiographic findings.
• MRI detected bone edema, while [18F]Fluoride PET-CT highlighted bone formation activity.

Conclusions:

• AS activity appears to be primarily associated with bone formation rather than inflammation.
• [18F]Fluoride PET-CT demonstrates significant potential for imaging AS bone activity.
• Inflammation-targeting tracers ([18F]FDG, [11C](R)PK11195) are less effective for AS imaging compared to active Rheumatoid Arthritis.