EVALUATION OF A RABBIT MODEL FOR OSTEOMYELITIS BY HIGH-FIELD, HIGH-RESOLUTION IMAGING USING THE CHEMICAL-SHIFT-SPECIFIC-SLICE-SELECTION TECHNIQUE

The rabbit model of osteomyelitis introduced by C.W. Norden, based on injection of an infecting solution (Staphylococcus aureus, sodium morr huate) into the tibia, was studied at 4.7 Tesla with a time-efficient chemical shift selective imaging technique, Chemical Shift Specific Sl ice Selection (C4S). The evolution of the disease over several weeks w as followed on water-selective, fat-selective, and sum images obtained simultaneously with this imaging sequence. Experiments were performed either on different groups of rabbits at different times after infect ion with subsequent sacrifice of the animal and microbiological analys is of the infected tibia or on the same group of animals imaged severa l times after infection. Associated analysis of the water and fat sele ctive images revealed marrow modifications very early (Day 5 after ino culation) demonstrating the high sensitivity of the employed imaging t echnique. Later on; bone modifications were best identified on the sum images. Additional experiments performed on animals injected with a n oninfecting solution containing only sodium morrhuate showed however t hat the sclerosing agent alone can yield images similar to those produ ced by infection at early stages after inoculation. Therefore, the Nor den model would not be suitable for monitoring quantitatively outcome of therapy by magnetic resonance imaging. It is however well adapted f or the evaluation and optimization of MRI techniques or protocols inte nded to detect early changes of bone marrow produced by septic or asep tic infarct.