Iron Particle–Enhanced Visualization of Inflammatory Central Nervous System Lesions by High Resolution: Preliminary Data in an Animal Model
R.A. Linkera,c,
A. Kronera,
T. Hornb,
R. Golda,c,
M. Mäurera and
M. Bendszusb
a Clinical Research Group for Multiple Sclerosis, Julius Maximilians-Universität Würzburg, Germany
b Departments of Neurology and Neuroradiology, Julius Maximilians-Universität Würzburg, Germany
c Institute for Multiple Sclerosis Research, University of Göttingen and gemeinnützige Hertie-Stiftung, Waldweg, Germany
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Fig 1. SPIO-based macrophage imaging in EAE lesions of the rat brain by sonography. rhMOG-EAE was induced in congenic 1AV1 Lewis rats. During relapse, whole brains were removed and imaged ex vivo in a water tank by using a 13-MHz phased-array sonographic transducer 24 hours after SPIO injection. On coronal planes, sharply delineated circumscribed areas of focal echogenicity could be identified in different rats, predominantly involving the frontal, periventricular, cerebellar, and brain stem region (upper row, lesions marked by white arrows; representative images from different rats are shown), a pattern that is typical for MOG-EAE. Imaging of rat brains with injection of PBS after induction of rhMOG-EAE (middle row, anatomically equivalent areas from different rats are shown) or SPIO injection without prior induction of EAE (lower row) did not reveal similar areas with focal hyperechogenicity and served as negative controls.
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Fig 2. Comparison of SPIO-enhanced sonographic imaging of EAE lesions with MR imaging. We performed in vivo MR imaging to correlate the sonographic results with a well-established technique to monitor SPIO-particle accumulation. On coronal CISS images (D–F) corresponding to the brain regions depicted by sonography (A–C), we identified areas of focal hypointensity in the periventricular area (A, -D) and in the cerebellar (B, -E) or brain stem region (C, -F) of rat brains (lesions marked by white arrows). Hypointense areas are indicative of local SPIO-particle accumulation. Note the marked similarity of lesion distribution between sonograms and MR images (compare A–C with D–F).
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Fig 3. Histologic evaluation. Paraffin sections were cut through the lesions as detected on MR imaging and sonography. A and B, The histology corresponds to the cerebellar lesion depicted in Figs 1A and 2A. A, Staining of macrophages and activated microglia by immunohistochemistry for ED1 (bar = 50 µm). Note the massive infiltrate of brown-stained ED1–positive cells. On a consecutive section (B, bar = 15 µm), Perls blue staining was performed to detect focal iron accumulation. Note the extensive perivascular iron deposition. Perls staining of liver sections with massively iron-laden Kupffer cells served as a histologically positive control for correct intravenous SPIO-particle injection (B, inset). Combination of Perls staining with ED1 immunohistochemistry reveals a clear colocalisation (C, bar = 10 µm), thereby identifying macrophage-like cells as one of the definitively iron-laden cell types in the CNS.
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