Brain Iron Distribution after Multiple Doses of Ultra-small Superparamagnetic Iron Oxide Particles in Rats.

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Toxicology

Background:

• Ultra-small paramagnetic iron oxide (USPIO) nanoparticles are utilized in neuroimaging.
• Understanding the long-term effects of high cumulative doses of USPIO is crucial for safety assessments.

Purpose of the Study:

• To investigate the impact of high cumulative doses of two USPIO compounds on rat brains.
• To evaluate iron deposition and associated changes in neuroimaging parameters.

Main Methods:

• Male Sprague-Dawley rats received daily intravenous injections of USPIO compounds for 4 weeks.
• Magnetic Resonance Imaging (MRI) including multiecho gradient-echo sequences, serum iron level analysis, and histology were performed.
• Quantitative susceptibility mapping (QSM) and R2* mapping were used to assess iron accumulation.

Main Results:

• Iron accumulation was observed in brain ventricles, detectable by R2* maps and QSM.
• Ventricular iron concentration was comparable to or higher than serum iron levels.
• Histology revealed choroid plexus hemosiderosis and midbrain vacuolation, but no parenchymal iron deposition.
• Serum iron levels increased, with a 7-day washout period reducing levels for only one USPIO compound.

Conclusions:

• High cumulative USPIO doses can lead to iron deposition in brain ventricles, causing persistent signal loss in T2*-weighted images.
• QSM is effective in quantifying iron biodistribution in such scenarios.
• Further research is needed to understand the long-term implications and safety of frequent, high-dose USPIO administration.