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Functional-morphologic MR imaging with ultrasmall superparamagnetic particles of iron oxide in acute and chronic
Achim H Kaim1, Gernot Jundt, Thorsten Wischer
1Department of Diagnostic Radiology, University Hospital Basel, Switzerland. akaim@uhbs.ch
Purpose:
To investigate the use of magnetic resonance (MR) imaging enhanced with ultrasmall superparamagnetic particles of iron oxide (USPIO) to identify acute, early chronic, and late chronic abscess formation in an experimental model of soft-tissue abscess.
Materials And Methods:
Experimental soft-tissue infection in 15 rats was imaged with an MR imaging unit on days 1 and 2 (acute), days 5 and 6 (early chronic), and days 8 and 9 (late chronic) after inoculation of the infectious agent. All animals were imaged without contrast enhancement and immediately and 24 hours after USPIO administration. MR and histopathologic findings were compared. The changes in relative signal intensity (SI) and in the extent and pattern of contrast enhancement (macrophage distribution) between the animal groups were analyzed. Statistical testing was performed with Kruskal-Wallis analysis of variance and the chi2 test.
Results:
At 24 hours after USPIO administration, the relative SI of the abscess wall and the relative macrophage extent were 0.50 (0.33-0.73) and 1.03 (0.90-1.08), respectively, for acute infection; 0.11 (0.10-0.18) and 0.94 (0.93-1.01) for early chronic infection; and 0.53 (0.44-0.58) and 0.80 (0.77-0.83) for late chronic infection. The changes in enhancement pattern (P <.001), relative SI (P <.001), and relative macrophage extent (P <.05) with time were significant.
Conclusion:
The macrophage distribution pattern increases the specificity of MR findings in chronic infection and allows differentiation between areas with active inflammation and areas of reparative granulation tissue.
Insights
Magnetic resonance imaging with ultrasmall superparamagnetic iron oxide particles can differentiate acute, early chronic, and late chronic soft-tissue abscesses. This technique aids in distinguishing active inflammation from reparative tissue in chronic infections.
Area of Science:
- Radiology and Imaging
- Medical Diagnostics
- Infectious Disease Research
Background:
- Accurate characterization of soft-tissue abscesses at different stages is crucial for effective treatment.
- Traditional imaging methods may have limitations in differentiating between active infection and healing processes.
- Ultrasmall superparamagnetic particles of iron oxide (USPIO) offer potential for enhanced contrast in magnetic resonance (MR) imaging.
Purpose of the Study:
- To evaluate the efficacy of USPIO-enhanced MR imaging in identifying acute, early chronic, and late chronic soft-tissue abscesses.
- To assess the ability of this imaging technique to distinguish between different phases of abscess formation in an experimental model.
Main Methods:
- Soft-tissue abscesses were induced in 15 rats and imaged using MR on days 1-2 (acute), 5-6 (early chronic), and 8-9 (late chronic).
- Imaging was performed without contrast and at immediate and 24 hours post-USPIO administration.
- MR findings were correlated with histopathologic results, analyzing signal intensity and contrast enhancement patterns reflecting macrophage distribution.
Main Results:
- Significant differences in enhancement patterns, relative signal intensity, and macrophage extent were observed over time (P <.001).
- USPIO-enhanced MR imaging demonstrated distinct signal intensity and macrophage distribution patterns for acute, early chronic, and late chronic abscesses.
- The relative signal intensity of the abscess wall and relative macrophage extent varied significantly across the different infection stages.
Conclusions:
- USPIO-enhanced MR imaging effectively differentiates between acute, early chronic, and late chronic soft-tissue abscesses.
- The macrophage distribution pattern observed with this technique increases the specificity of MR findings in chronic infections.
- This method allows for differentiation between areas of active inflammation and reparative granulation tissue, aiding in diagnosis and management.
