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In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis
Published on: October 20, 2013
MRI of macrophages in infectious knee synovitis
Guillaume Bierry1, François Jehl, Agnès Neuville
1Department of Radiology, University Hospital of Strasbourg, 67098 Strasbourg, France. guillaume.bierry@chru-strasbourg.fr
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.
Insights
Macrophage imaging with ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI effectively depicts bacterial knee infection. This technique visualizes USPIO-loaded macrophages in infected synovium, offering a promising diagnostic tool for infectious synovitis.
Area of Science:
- Biomedical Imaging
- Infectious Diseases
- Orthopedics
Background:
- Bacterial knee infections, or infectious synovitis, pose diagnostic challenges.
- Accurate and early detection is crucial for effective treatment and preventing joint damage.
- Current diagnostic methods may have limitations in specificity and sensitivity.
Purpose of the Study:
- To prospectively evaluate macrophage imaging using ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI.
- To assess the capability of USPIO-enhanced MRI in depicting bacterial knee infection in an experimental rabbit model.
- To correlate MRI findings with histopathologic results.
Main Methods:
- A rabbit model of Staphylococcus aureus knee infection was established.
- Magnetic Resonance Imaging (MRI) was performed before and after USPIO administration.
- T1-, T2-, and T2*-weighted sequences were utilized, alongside gadolinium enhancement for synovial hyperplasia assessment.
- Histopathology (H&E and Perls Prussian blue stains) served as the gold standard.
Main Results:
- Infected knees showed intense infiltration of iron-loaded macrophages.
- Significant signal loss was observed on T1-, T2-, and T2*-weighted MRI in infected knees post-USPIO administration (p < 0.01).
- Control knees without infection exhibited normal synovium and no significant MR signal changes after USPIO administration (p = 0.07-0.48).
Conclusions:
- Macrophage imaging using USPIO-enhanced MRI is effective in depicting infectious knee synovitis.
- USPIO-enhanced MRI can visualize USPIO-loaded macrophages within the synovium of infected joints.
- This technique holds potential as a sensitive diagnostic tool for bacterial knee infections.
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