About the PhD thesis

Osteomyelitis (OM) is an infection of the bone marrow and adjacent bone structures, often caused by the gram-positive bacterium Staphylococcus aureus (S. aureus). OM results in progressive bone destruction and loss and may extend into surrounding soft tissues. Early identification and localization of OM are critical for timely and appropriate treatment selection. Prompt antibiotic therapy may prevent necrosis of the affected bone.

However, distinguishing between active bacterial infection and sterile inflammation using the available imaging modalities is difficult. These modalities make it possible to view morphological changes (conventional radiographic imaging, CT, and MRI) or molecular changes (SPECT/PET). Morphological imaging helps confirm and reveal the extent of OM but is not always sufficient, and supplementing with molecular imaging is often needed. Hybrid imaging (combining morphological and molecular imaging) has improved diagnostics of OM significantly, but we still have problems discriminating sterile inflammation from infection.

Therefore, we examined and developed various new radioactive tracers for detecting OM based on multiple strategies, and we hoped that these methods would make it possible to distinguish between infection and inflammation.

We designed our protocol in 2010-12, began our work in 2013, and completed scanning in 2017. We explored and developed various new tracers for detecting OM and compared them with traditional tracers. For this, it was essential to have a suitable animal model. We refined and evaluated a juvenile pig model for hematogenous S. aureus OM and focused on OM in children. We found several tracers we explored were valid candidates for molecular imaging of OM in children due to their low ionizing radiation levels and acceptable sensitivity.

Our results have been published in peer-reviewed scientific journals, of which ten publications are included in this thesis.

We succeeded in refining a juvenile porcine model so that it can be used to test radioactive tracers. Our results and the demonstrated utility of the radionuclides in imaging should stimulate further efforts to explore their role in managing infectious and inflammatory diseases in humans.