MRI of macrophages in infectious knee synovitis.

Abstract

OBJECTIVE:

The objective of our study was to prospectively evaluate macrophage imaging using ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI to depict bacterial knee infection in an experimental rabbit model.

SUBJECTS AND METHODS:

Unilateral knee infection was induced by intraarticular injection of Staphylococcus aureus in eight rabbits. The contralateral knees were used as internal controls. After a mean interval of 3 days, two MRI sessions (3-T MRI) were performed before and 24 hours after IV administration of USPIO. The protocol included T1-weighted spin-echo, T2-weighted spin-echo, and T2*-weighted gradient-echo images. A gadolinium-enhanced T1-weighted sequence was also performed in the first session to optimize detection of synovial hyperplasia. MR data were analyzed qualitatively and quantitatively and compared with histopathologic findings (H and E stain and Perls Prussian blue stain). Signal-to-noise ratio changes after USPIO administration were compared using Wilcoxon's signed rank test.

RESULTS:

All inoculated knees presented infectious synovitis with intense infiltration of iron-loaded macrophages. In these infected knees, signal loss was determined visually and quantitatively on T1-weighted (p < 0.01), T2-weighted (p < 0.01), and T2*-weighted images (p < 0.01) 24 hours after USPIO administration, reflecting the presence of USPIO-loaded macrophages in the synovium. In contrast, no significant MR signal changes were observed in the control knees (p = 0.07-0.48), which presented a normal synovium without infiltration of iron-loaded macrophages.

CONCLUSION:

Macrophage imaging using USPIO-enhanced MRI can depict infectious knee synovitis.

• Authors: Guillaume Bierry, François Jehl, Agnès Neuville, Sophie Lefevre, Philippe Robert, Stéphane Kremer, Jean-Louis Dietemann
• Journal: AJR. American journal of roentgenology (AJR Am J Roentgenol) Vol. 194 Issue 6 Pg. W521-6 (Jun 2010) ISSN: 1546-3141 [Electronic] United States
• PMID: 20489072 (Publication Type: Journal Article)

Chemical References

• Contrast Media
• Dextrans
• Magnetite Nanoparticles
• Organometallic Compounds
• ferumoxtran-10
• Meglumine
• gadoterate meglumine
• Ferrosoferric Oxide

Topics

• Animals
• Contrast Media
• Dextrans
• Disease Models, Animal
• Ferrosoferric Oxide
• Image Processing, Computer-Assisted
• Knee Joint (pathology)
• Macrophages (pathology)
• Magnetic Resonance Imaging (methods)
• Magnetite Nanoparticles
• Meglumine
• Organometallic Compounds
• Prospective Studies
• Rabbits
• Statistics, Nonparametric
• Synovitis (microbiology, pathology)