Fig. 3

Macrophage activation determined in untreated animals with osteoarthritis (OA) (circles) and triamcinolone acetonide–treated animals (squares) after injection of ¹¹¹In-EC0800 using single-photon emission computed tomography/computed tomography (SPECT/CT). a Quantitative outcome of measured radioactivity in the healthy joints (blank boxes) and OA joints (grey boxes) normalized to the size of the analyzed cylindrical region of interest (in kilobecquerels per cubic millimetre). Absolute differences per animal were calculated (in kilobecquerels per cubic millimetre) to correct for differences in biodistribution of ¹¹¹In-EC0800 (black boxes). High radioactivity is related to more macrophage activation. b Ectopic bone formation (in kilobecquerels per cubic millimetre) as a measure for osteophyte development was quantified on longitudinal bone micro–computed tomographic (μCT) scans. c Sagittal SPECT/CT images of knee joints from representative animals. μCT images shown in black and white were used for anatomical reference. The SPECT/CT images are shown in colour. Transaxial images from patellar bone extracted from binary μCT images show ectopic bone formation (red). *p < 0.05, **p < 0.01, ***p < 0.001. Error bars indicate 95 % confidence intervals