Utility of Quantitative and Semi-Quantitative SPECT/CT Metrics in Differentiating Mueller-Weiss Syndrome.

Background/Objectives: Mueller-Weiss syndrome (MWS) is a rare condition characterized by spontaneous adult-onset osteonecrosis of the navicular bone. This study aimed to assess the diagnostic value of quantitative and semi-quantitative standardized uptake value (SUV) measurements on Tc-99m MDP SPECT/CT for differentiating MWS from other foot pathologies. Methods: We retrospectively reviewed 21 MWS patients who underwent SPECT/CT and compared them with 10 feet from 5 non-MWS patients as controls. MWS severity was staged using the Maceira classification. Volumes of interest (VOIs) were defined in the lateral navicular and distal tibia. SUVmax values were measured for the navicular bone (N), tibial metaphysis (Tm), and diaphysis (Td). Uptake ratios (N/Tm and N/Td) were calculated for semi-quantitative comparison. Results: MWS patients showed significantly higher SUVmax in the navicular compared with controls (9.2 vs. 1.5, p < 0.001). Both N/Tm and N/Td ratios were also significantly elevated (p < 0.001). SUVmax and uptake ratios positively correlated with Maceira stage and visual navicular uptake intensity. Diagnostic thresholds of N SUVmax > 3.77 (AUC = 0.93), N/Tm > 1.139 (AUC = 0.95), and N/Td > 0.93 (AUC = 0.93) effectively distinguished MWS from non-MWS cases. Conclusions: Quantitative and semi-quantitative SUV analysis on SPECT/CT offers a reliable tool for diagnosing MWS and evaluating disease severity. Semi-quantitative ratios, by normalizing metabolic variability, provide a practical and reproducible alternative to absolute SUV measurements for early detection and treatment planning in MWS.