[MRI of intraosseous fistulous systems and sequesters in chronic osteomyelitis with standard spin echo sequences, highly selective chemical-shift imaging, diffusion weighted imaging, and magnetization-transfer].

PURPOSE

To study and test the impact of modern MRI techniques in diagnostic imaging in the evaluation of intra-osseous fistulous systems and sequesters.

MATERIALS AND METHODS

In a prospective study, nine patients with chronic osteomyelitis of the legs were examined by MRI. Patients with clinical signs of osteomyelitis requiring surgery were included in the study. T1-weighted spin echo (SE) sequences, proton density (PD) and T2-weighted fast spin echo (FSE) sequences, water- and fat-selective FSE sequences, and diffusion weighted (DW) PSIF sequences were used preoperatively. Furthermore, magnetizing transfer (MT) with gradient echo (GRE) sequences was evaluated.

RESULTS

Water selective sequences revealed the highest sensitivity for the detection of fistulas (100%), providing the best delineation of the extent of the entire fistulous systems. Fat-selective sequences (sensitivity 55.6%) and T1-weighted sequences (sensitivity 77.8%) displayed fistulas as hypointense bands, which, however, cannot be well differentiated from cortical bone in the transcortical areas. PD and T2-weighted images were found to have a poor sensitivity (55.6% and 66.7%) for fistulas in any location. The sensitivity of water-selective sequences to demonstrate intraosseous sequesters was 100%. The sensitivity was low for the other sequences. In 4 of 5 patients with surgically proven infection, DW and MT revealed an abnormal spatial distribution, with high diffusion in the central parts of the fistulas and high MT effect peripherally surrounding a weak MT effect centrally.

CONCLUSION

Water-selective sequences are superior when demonstrating fistulous systems and intraosseous sequesters. The combined use of MT and DW sequences seems to allow a differentiation between solid granulation tissue and liquid pus.