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Updated: Sep 18, 2026
Registered Bioimaging of Nanomaterials for Diagnostic and Therapeutic Monitoring
Published on: December 9, 2010
Dose and scanning delay using USPIO for central nervous system macrophage imaging
V Dousset1, C Gomez, K G Petry
1Laboratoire de Neurobiologie et Neuroimagerie Expérimentales, Université Victor Segalen Bordeaux 2, France. vincent.dousset@chu-aquitaine.fr
Rationale And Objectives:
In experimental allergic encephalomyelitis (EAE), central nervous system (CNS) macrophage imaging is achievable by MRI using AMI-227 an ultra-small particle iron oxide contrast agent at a dose of 300 micromol/kg Fe. The objective was to test the feasibility at the human recommended dose of 45 micromol/kg Fe.
Methods:
Two groups of EAE rats were tested with AMI-227 using 45 and 300 micromol/kg Fe respectively. Following i.v. injection of AMI-227, they were scanned after a delay of 4-6 and 20-24 h.
Results:
With a high dose of AMI-227, all animals showed low signal intensity related to iron-loaded macrophages in the CNS. At low dose no abnormalities were found in the CNS. Furthermore, a delay of 4-6 h failed to demonstrate abnormalities even at high dose.
Conclusions:
Dose, scanning delay after administration and blood half-life are major parameters for T2* CNS macrophage imaging.
Insights
Central nervous system (CNS) macrophage imaging using AMI-227 requires higher doses and longer delays than tested. Lower doses and shorter scan times failed to detect macrophages in experimental allergic encephalomyelitis (EAE) models.
Area of Science:
- Neuroimaging
- Immunology
- Radiology
Background:
- Experimental allergic encephalomyelitis (EAE) is a model for CNS inflammatory diseases.
- Iron oxide nanoparticles, like AMI-227, can be used for macrophage imaging via MRI.
- Previous studies showed feasibility of CNS macrophage imaging with AMI-227 at 300 micromol/kg Fe.
Purpose of the Study:
- To evaluate the feasibility of CNS macrophage imaging using AMI-227 at the human-recommended dose of 45 micromol/kg Fe.
- To determine optimal scanning parameters for AMI-227-based macrophage imaging in EAE.
Main Methods:
- Two groups of EAE rats were administered AMI-227 at doses of 45 micromol/kg Fe and 300 micromol/kg Fe.
- MRI scans were performed at 4-6 hours and 20-24 hours post-injection.
Main Results:
- High-dose AMI-227 (300 micromol/kg Fe) resulted in low signal intensity in the CNS, indicating iron-loaded macrophages.
- Low-dose AMI-227 (45 micromol/kg Fe) did not reveal any CNS abnormalities.
- A scanning delay of 4-6 hours was insufficient to detect abnormalities, even at the high dose.
Conclusions:
- The dose of AMI-227 is a critical factor for successful CNS macrophage imaging.
- Scanning delay post-administration significantly impacts the detection of iron-loaded macrophages.
- Blood half-life and imaging parameters are crucial for T2* CNS macrophage imaging.
