Cellular imaging at 3 T: Detecting Cells in Inflammation using Active Labeling with Super paramagnetic Iron oxide Azhar Hosein Faraz Medical Biophysics Western University Robarts Research Institute Under supervision of: Dr. Paula Foster 4 th April 2012
Immune Response and Inflammation Tissue injury caused by bacteria, trauma, chemicals, or any other phenomenon –Inflammation. Walling- off Within minutes after inflammation occurs macrophages already present in the tissues (microglia, Kupffer cells,..) begins their phagocytic action. The second line of defence within the first hours of inflammation begins are the large number of neutrophils that invade the inflamed area.
In Vivo Labeling of Cells with Iron Particles Imaging Immune Cells with MRI Iron oxide contrast agent Intravenous (i.v) administration Phagocytosis Labeled cells
Iron oxide-based MRI contrast agents Adapted from Modo, M. et al. Mol. Imag, 2004 Effect of iron is to cause signal loss in MRI images Iron-labeled cells In gel
Aim of study To detect inflammatory cells in the mouse brain by in vivo 3T MRI in a model of neuroinflammation.
MRI Pre-Scan of body Normal Healthy Mouse (C57/Bl6, n=2) Iron Oxide (Fe) injected Intravenously (IV) to Mice MRI Body 24 hours Post-injection (Fe) Fe -Bone marrow -Liver -Spleen Monocytes Inject mice with : LPS (lipopolysaccharide) 48 hours Post-injection (Fe) MRI Body 6 days Post-injection (Fe) Model of Neuroinflammation -Neurotoxic -Over activation of microglia MRI Brain 9 days Post-injection (Fe) Methods
3T clinical system Solenoid radio frequency coil Custom-built high performance gradient Imaging Cells (3T cellular MRI) at Robarts -Only lab in the world -research imaging experiments at clinical magnetic strength -pulse sequence known as, bSSFP.
Image Analysis: Body Images Measuring mean signal intensity of different image slices in Liver, Bone marrow, and Spleen. Standard deviation (SD) of Noise present in each slice. SNR Signal to Noise ratio Mean signal intensity / SD of Noise Present in each scan slice
Image Analysis: Brain Images
Results
Whole Mouse Body BSSFP Images HeadTail Before Iron Injection
Post Injection Iron In vivo labelling of liver, spleen and bone marrow macrophages
Results: SNR Liver > Spleen > Bone marrow
MRI Brain Voids present in brain
Results: FSL FSL is related to the amount of Iron in discrete reigns of signal void. Can be related to the number of iron-labeled cells. FSL is related to the amount of Iron in discrete reigns of signal void. Can be related to the number of iron-labeled cells.
SUMMARY Changes in SNR suggests that cells take up iron in the liver, spleen and bone marrow - the numbers of iron-labeled cells is different for each organ and varies in mice. This work indicates that pre-labeling immune cells with iron allows us to track their involvement in inflammation in the brain This study has been done for first time
Future directions To prove that signal loss in the brain is due to the accumulation of immune cells To determine which kind of cells are presenting in brain, using histology and experiments with transgenic mice. To obtain body images over a prolonged time period, to better understand the time course of cell uptake and retention of iron.
Acknowledgment Supervisor : Dr. Paula Foster Research funding : MS society Thanking Jonatan Snir, for imaging
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