Synchrotron radiation micro-CT imaging of the mouse brain (original) (raw)

Abstract

ABSTRACT PURPOSE MRI coupled with the injection of Ultrasmall particles of iron oxide (USPIO) has been successfully applied for pre-clinical and clinical studies of cerebral inflammation following stroke. Current limitations of this approach are represented by the difficulty of interpreting MR signal changes in terms of exact localization and quantification of USPIO. To overcome this limitation, Synchrotron Radiation phase micro computerized tomography (SR-PCT) was proposed as a new method to visualize USPIO distribution into the whole brains of mice. METHOD AND MATERIALS The following samples were imaged : i) USPIO phantoms with concentrations in the range 0,15 nM – 1500 µM ii) 16 post-mortem brains with intracerebral injections of iron concentrations [15-1,500] µmol Fe/l and iii) 8 post-mortem brains of mice having received intravenous injection of USPIO after induction of experimental stroke. The X-ray beam transmitted through the specimen was acquired on a detector using a LuAg scintillator screen, visible light optics and a 2048x2048 CCD detector. The pixel size was set to 8µm, which provides a field of view of 16 mm3. For each scan, 1999 radiographs were taken at different angles evenly distributed between 0 and 360 degrees. Finally, the Fil-tered Back Projection algorithm was applied to obtain a reconstructed 3D volume, i.e. a stack of 2048 slices of 2048x2048. RESULTS In vitro, the relationship between iron concentrations and absorption coefficients was linear for concentrations superior to 10 µM. In stereotaxicallly injected brains, SR-PCT was able to detect hyperintense signals in all mice, while allowing an accurate localization in the brain compared to T2-weighted MRI. In stroke animals, SR-PCT provided exquisite anatomical details compared to immunohistologic slices, allowing to identify both healthy and pathological brain structures. Visualization of bright spots in the ischemic lesions co-localized with hypointense signals detected by MRI . CONCLUSION Microtomography with SR-PCT showed a good sensitivity to USPIO detection, while allowing an accurate localization. Further analysis are warranted to investigate quantitative performances of the approach. CLINICAL RELEVANCE/APPLICATION Microtomography with SR-PCT represents a promising tool for brain imaging

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