A comparison of ferumoxytol with gadolinium as contrast agents for the diagnostic magnetic resonance imaging of osteomyelitis

Background: Ferumoxytol, an FDA-approved superparamagnetic iron oxide nanoparticle (SPION) preparation used for the treatment of iron deficiency anemia, is also known to be taken up by macrophages in areas of infection or in- flammation, where it produces negative contrast changes on T2-weighted MR images. Purpose: We sought to compare Ferumoxytol-induced MRI contrast changes with those observed using standard-of-care Gadolinium in patients presenting with symptoms suggestive of osteomyelitis. Subjects: Out of eighteen enrolled patients, 15 had MR imaging with both ferumoxytol and gadolinium. Based on clinical and/or pathologic criteria, 7 patients were diagnosed with osteomyelitis, 5 patients had osteomyelitis ruled out, and in 3 patients a definitive diagnosis could not be made. Field strength: 1.5 Tesla. Sequences: Used included STIR, T1-weighted and T2-weighted spin echo. Assessment: The mean contrast changes upon ferumoxytol and gadolinium administration were measured from lesion regions of interest and compared with control regions. Statistical tests: Student's t-test, propagation of errors. Data are reported as means +/- S.E. Results: The mean contrast changes, Delta C, associated with a diagnosis of osteomyelitis were found to be Delta CFe = -2.7 +/- 0.7 when Ferumoxytol and T2w imaging sequences were used and Delta CGd = +3.1 +/- 1.1 (P < 0.001) when Gadolinium and a T1 w imaging sequence was used. The MRI contrast changes for both agents correlated with systemic markers of inflammation, such as the erythrocyte sedimentation rate. In patients without osteomyelitis, no significant contrast changes were observed in T2-weighted, Ferumoxytol-contrasted MRI. The macrophages in osteomyelitic lesions were found to take up at least 16 times as much iron as benign bone marrow. Data conclusion: We conclude that in terms of its MRI diagnostic accuracy for osteomyelitis Ferumoxytol-contrasted MRI is a promising approach for diagnosing osteomyelitis that merits further study.