Comparison of ¹⁸F-FDG and ⁶⁸Ga PET imaging in the assessment of experimental osteomyelitis due to Staphylococcus aureus

Although positron emission tomography (PET) using 2-[¹⁸F]fluoro-2-deoxy-D-glucose (¹⁸F-FDG) is a promising imaging modality for bone infections, the technique may still give false-positive results due to unspecific uptake in healing bone. This experimental study compared ¹⁸F-FDG and ⁶⁸Ga in PET imaging of osteomyelitis and normal bone healing.

A diffuse osteomyelitis model of the tibia was applied in the rat (n=50). Two weeks after operation, PET imaging with ¹⁸F-FDG and ⁶⁸Ga was performed, followed by peripheral quantitative computed tomography (pQCT) and radiography. Osteomyelitis was verified by quantitative bacteriology. In addition to in vivo imaging, ex vivo measurements of tissue radioactivity were performed to verify uptake of the tracers.

Compared with controls with normal bone healing, the osteomyelitic tibias showed increased SUV ratios (i.e. radioactivity ratios between the operated and non-operated sides) for both ¹⁸F-FDG (1.74±0.37) and ⁶⁸Ga (1.62±0.28) (P<0.001). Ex vivo measurements also showed increased tracer accumulation in the infected bone (P=0.003 for ¹⁸F-FDG and P<0.001 for ⁶⁸Ga). The intensity of ⁶⁸Ga uptake reflected pathological changes of osteomyelitic bones measured by pQCT. The uptake of ¹⁸F-FDG, however, did not show as close a correlation with the anatomical changes. The healing bones without infection exhibited slightly elevated uptake of ¹⁸F-FDG (SUV ratio 1.16±0.06), but ⁶⁸Ga did not accumulate in the healing bone, as judged on the basis of both in vivo imaging (SUV ratio 1.02±0.05) and ex vivo measurements (SUV 0.92±0.21) (P=0.003 and P=0.022 compared with ¹⁸F-FDG uptake, respectively).

This study suggests the feasibility of ⁶⁸Ga PET imaging of bone infections. However, further studies are needed to clarify the value of ⁶⁸Ga PET for clinical purposes.