Early Assessment of Treatment Response in Takayasu Arteritis An 18FDG PET Procedure

Purpose: To describe a procedure allowing early assessment of treatment response in Takayasu arteritis (TA) patients by averaging the standard uptake value obtained from N hottest voxels irrespective of their location within the F-18-FDG-positive vessel walls (SUVmax-N). Methods: The procedure is illustrated in a score-V TA patient before and after 1 and 3 months of glucocorticoid treatment (scans 0-1-3, respectively). Comparison between scans was made by using SUVmax-N repeatability percentages with 95-99-99.9% reliability. Results: No significant difference in SUVmax (ie, N = 1) was found between scan 0 and 1, and between scan 1 and 3, with 95% reliability. A significant difference in SUVmax-N was found with 99.9% reliability for each scan pair by averaging N = 4100-515 hottest voxels (total hottest volume of 100.0-12.6 mL), respectively. Conclusions: The proposed SUVmax-N procedure may be an efficient tool to early assess treatment response in TA patients. Further studies involving series of patients with large vessel vasculitis are warranted to investigate its usefulness in their management.