052 non invasive high resolution detection
- 1. Non-Invasive High Resolution Detection of Active Atherosclerotic Plaque in ApoE Deficient Mice by Magnetic Resonance Imaging after Injection of Super Paramagnetic Iron Oxide (SPIO) Center for Vulnerable Plaque Research University of Texas at Houston Texas Heart Institute
- 2. A B
- 3. l>Macrophages infiltration l>Extensive angiogenesis and vasa vasorum leakage
- 4. Plaque Morphology vs. Plaque Activity Why do we need both? The short answer is: because not all plaques with similar morphology would result in similar outcome.
- 5. Morphology vs. Activity Imaging Inactive and non-inflamed plaque Active and inflamed plaque Appear Similar in IVUS OCT MRI w/o CM Morphology Show Different Activity Thermography, Spectroscopy, immunoscintigraphy, MRI with targeted contrast media…
- 6. Current Methods for DetectionCurrent Methods for Detection of Vulnerable Plaquesof Vulnerable Plaques lOptical coherence tomography lRadioscintigraph lThermography lNear infrared spectroscopy lMagnetic resonance imaging
- 7. Human Carotid Plaque Courtesy of Dr. Chun Yuan University of Washington
- 8. We need MRI with vulnerable plaque targeted contrast media that identifies: 1- Inflammation (macrophage infiltration), 2- Fissured/Permeable Cap, 3- Leaking Angiogenesis and 4- Intra-Plaque Hemorrhage 5- …
- 9. SuperparamagneticSuperparamagnetic andand Ultra-superparamagneticUltra-superparamagnetic Iron OxideIron Oxide lBlood pool Magnetic resonance (MR) imaging contrast media with a central core of iron oxide generally coated by a polysaccharide layer lShortening MR relaxation time lEngulfed by and accumulated in cells with phagocytic activity
- 10. Particle Core Size Particle Size Blood (nm) (nm) Half-life Combidex 5-6 20-30 8h Feridex 4-6 35-50 2.4±0.2h DDM 43/34/102 6.4 20-30 6h Clariscan MION 4-6 17 varies Feruglose --- --- --- --- Examples of commercially available SPIOs
- 11. Current applications of SPIO in MR imaging: -Detection of Hepatic Lesions (primary and metastatic cancers) -Experimental Nephritic syndrome in Laboratory animals -Monitoring rejection of transplanted heart or kidney in the animal model of allograft transplantation. -Experimental detection of CNS lesions in laboratory animals.
- 12. USPIOs Enter the AtheroscleroticUSPIOs Enter the Atherosclerotic Plaque ThroughPlaque Through lMacrophages that engulfed them lFissured or thin cap l Extensive angiogenesis l vasa vasorum leakage l Intra plaque hemorrhage
- 13. In-vitro Study of Macrophage SPIO Uptake In a series of in-vitro studies we have tested the rate of SPIO uptake by human activated monocytes in different conditions regarding incubation time and concentration of SPIO. All SPIO were labeled by a fluorescent dye (DCFA).
- 14. FL-labeled SPIO Incubated Macrophages 24hr
- 15. Double DAPI Staining with Fluorescence-labeled SPIO Macrophages after 24hr Incubation
- 16. HypothesisHypothesis Active macrophages residing inside the inflamed vulnerable plaques can be visualized following injection of SPIO or USPIOs into the systemic circulation by virtue of a decrease in the magnetic resonance signal intensity of the plaque,and correlate with histopathologic characteristics of vulnerability to rupture.
- 17. vasa vasorum Over magnification is a major advantage of SPIO Darkening property of SPIO in the white background of fat and water of plaque is another advantage
- 18. SPIO and T2 Effect In-vitro study to show the effect of macrophage SPIO uptake on their T2 relaxation time
- 20. 0 10 20 30 40 50 60 70 80 90 50 250 control 20 min 60 min 6 hours 24 hours Macrophage Uptake of Feridex with Time and Concentration Shown by T2 Reduction Concentration µmol/ml
- 21. In-vivo distribution of SPIO in ApoE deficient and wild type mice: •For the initial study, we use the mouse model of atherosclerosis. • •ApoE deficient mouse has similar atherosclerotic lesions to human and the lesions are more common in the aortic arch and thoracic aorta. • We used ApoE deficient mice and normal variant (C57BL mice) as control. •The SPIO that we used was Feridex (Berlex) injectable solution. •Animals were sacrificed on day 3 and 5 after injection.
- 22. Pre and Post-SPIO Enhanced Magnetic Resonance Imaging of ApoE K/O and Wild Type Mice: We used 4.7 tesla MRI unit (University of Texas, Galveston MRI Unit, Galveston, TX) in our study. After baseline MR imaging with respiratory gating, we injected 1mMolFe/kg super paramagnetic iron oxide to six ApoE deficient and two C57bl mice through the tail vein. Post-contrast MR imaging were performed in day 5 with the same parameters (TR=2.5 sec, TE=0.012 sec, FOV=6.6 cm, slice thickness=2.0mm, flip angle (orient)=trans, and matrices=256x256). We selected the aorta at the level of kidney for comparison of the baseline and post-contrast images.
- 23. •Tissues from different organs including liver, kidneys, lung, heart, spleen and aorta (including valve region ascending, descending and abdominal) was obtained and stained. • We used Hematoxyline and Eosin (H&E), Iron, CD68 and Movat staining. • After Iron staining, aortic wall of the ApoE deficient mice and normal variant were compared based on the number of Iron particle. • Also different doses of Feridex and The timing between injection and tissue obtaining was considered.
- 24. Histopathologic study of the Mouse injected With SPIO (Thoracic Aorta) ApoE KO mouse, Movat staining, proximal aorta Coronary Cross section Atherosclerosis plaque
- 25. Histopathologic study of ApoE KO Mouse injected With SPIO (Thoracic Aorta) CD68 staining (aortic plaque) Iron Staining (aortic plaque) Iron Staining (coronary section) Iron particles Iron particles
- 26. Histopathologic study of ApoE KO Mouse injected With SPIO (Abdominal Aorta) H&E staining Iron Staining CD 68 staining Iron particles
- 27. Histopathologic study of wild type Mouse injected With SPIO (Thoracic Aorta) H&E staining CD68 stainingIron staining
- 28. Comparison of the Number of the Iron Particles (per HPF) in ApoE KO Mice Plaque vs. Normal Wall 0 5 10 15 Atherosclerotic Aorta Average number of iron particles per sample P <0.001
- 29. MR Image of Abdominal Aorta After SPIO Injection in ApoE and Control Mice ApoE deficien t mouse C57B1 (control) mouse Before Injection After Injection (5 Days ) Dark (negatively enhanced) aortic wall, full of iron particles Bright aortic lumen and wall without negative enhancement and no significant number of iron particles
- 30. Typical in vivo MR images of a live mouse at the heart (left) and renal level (right). Various vessels and aortic arch can easily e seen in these images. The slice thickness is 0.5 mm and the in-plane resolution is 50 µm (7.1 T MR system).
- 31. We chose Watanabe Hereditary Hypercholesterolemic rabbits (WHHR) and New Zealand White rabbits (NZW) for this study. We injected them with SPIO (Feridex) 1 mMol Fe/kg and obtained baseline as well as 5-day post-SPIO injection MR images of the aorta (1.5 Tesla MRI system at the University of Texas, MD Anderson,Houston,Texas). Then we compared the images in hypercholesterolemic rabbits with the normal,wild type NZW rabbits. Rabbit ex-vivo MRI studies: After the in-vivo MR images, we sacrificed the animals and excised the aorta. Then we put the isolated aorta in a gel medium, clamped both ends and any side branches and injected gadolinium inside the lumen. We did the same procedure for all rabbits. We also used 2 more rabbits, one WHHR and one NZW that were not injected with SPIO, as control, in the ex-vivo MR study. SPIO-Enhanced MRI study in rabbits
- 32. Histopathologic studies of Thoracic aorta in Watanabe Hereditary Hypercholesterolemic rabbit after SPIO injection H&E staining Iron staining Iron staining
- 33. Histopathologic studies of Thoracic aorta in Watanabe Hereditary Hypercholesterolemic rabbit after SPIO injection H&E staining Iron staining Iron staining Iron particles
- 34. Plaque Cell Density vs SPIO 0 10 20 30 40 50 60 0 10 20 30 40 50 60 70 Cell Denity in H&E staining SPIOpositivecell-Iron staining Series1 R=0.956 Correlation between Iron positive cells in Iron staining and cell density in H&E staining in rabbit atherosclerotic aorta.
- 35. MR Angiography 3D with Gadolinium-DTPA in Watanabe Rabbit Before SPIO injection After SPIO injection
- 36. Ex-vivo MR study of the thoracic aorta in Watanabe and Wild type rabbit after SPIO injection compared to control. 3D MR Angiography with Gadolinium-DTPA Watanabe rabbit Post-SPIO Watanabe rabbit control NZW rabbit control NZW rabbit Post-SPIO
- 37. Ex-vivo MR study of the thoracic aorta in Watanabe and Wild type rabbit after SPIO injection compared to control. (Gradient echo) Watanabe rabbit Post-SPIO Watanabe rabbit control NZW rabbit Post-SPIO NZW rabbit control