The role of FDG-PET in assessing osteoarthritis

Abstract

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Objectives: To determine the location and degree of FDG uptake on PET in knees for detecting osteoarthritis. Methods: Thirty two patients(age38-77,16M&16F) who had FDG-PET of lower extremities for evaluation of hip or knee prosthesis were included. This population(64 total knees) were divided into two groups(14 knees with prosthesis were excluded from this analysis), first group included 14 knees with osteoarthritis(OA)(based on clinical diagnosis of OA) and control group included 36 knees without OA (no clinical diagnosis of OA). FDG uptake in medial and lateral synovia, joint space and patello-femoral joint was visually assessed and compared to adjacent structures and scored 0-no uptake, 1-mild, 2-moderate and 3-severe. Maximum Standardized Uptake Value(SUVmax) in the same regions of interest including entire knee was measured in both groups. We compared qualitative and quantitative results in knees between the two groups. Results: Average(Avg) SUVmax with Standard Deviation(SD) for medial synovium was 1.1±0.3 in OA group and 0.9±0.2 in control group(p<0.05). FDG uptake in medial synovium in knees with OA was higher than in knees without OA. Avg. SUVmax±SD in lateral synovium, joint space and around entire knee in OA group was higher than that in control group, 1±0.2 versus 0.9±0.2 respectively in lateral synovium, 0.9±0.3 versus 0.7±0.2 respectively in joint space and 1.1±0.2 versus 0.9±0.2 respectively around entire knee. The comparisons did not reach statistical significance in these regions between the two groups likely due to limited population, in spite of a trend of higher values in OA group. There was no difference in avg. SUVmax±SD for patello-femoral joint between the two groups, 0.7±0.2 versus 0.7±0.3 in knees with OA versus control group respectively. With qualitative assessment there was no statistical difference between knees with OA and those without OA. Conclusions: These preliminary data suggest a trend towards increasing FDG uptake around entire knee and in particular in medial synovium in patients with OA. The lateral synovium and joint space also had increased FDG uptake in knees with OA. This is suggestive of inflammation in these structures and joint space uptake may be due to cartilage degradation and possibly secondary inflammation. Further studies are needed to determine the role of FDG-PET in this disabling disease.