Identifying inflamed carotid plaques using in vivo USPIO-enhanced MR imaging to label plaque macrophages
Rikin A Trivedi1, Chinthake Mallawarachi, Jean-Marie U-King-Im
1University Department of Radiology, Addenbrooke's Hospital, Cambridge, UK. rt256@radiol.cam.ac.uk
Background:
Inflammation within atherosclerotic lesions contributes to plaque instability and vulnerability to rupture. We set out to evaluate the use of a macrophage labeling agent to identify carotid plaque inflammation by in vivo magnetic resonance imaging (MRI).
Methods And Results:
Thirty patients with symptomatic severe carotid stenosis scheduled for carotid endarterectomy underwent multi-sequence MRI of the carotid bifurcation before and after injection of ultrasmall superparamagnetic particles of iron oxide (USPIOs). USPIO particles accumulated in macrophages in 24 of 30 plaques (80%). Areas of signal intensity reduction, corresponding to USPIO/macrophage-positive histological sections, were visualized in 24 of 27 (89%) patients, with an average reduction in signal intensity induced by the USPIO particles of 24% (range, 3.1% to 60.8%).
Conclusions:
USPIO-enhanced MRI can identify plaque inflammation in vivo by accumulation of USPIO within macrophages in carotid plaques.
Insights
Ultrasmall superparamagnetic particles of iron oxide (USPIO) enhanced MRI effectively identifies carotid plaque inflammation by targeting macrophages. This imaging technique visualizes inflammation in 89% of patients, aiding in assessing plaque vulnerability.
Area of Science:
- Cardiovascular Imaging
- Atherosclerosis Research
- Molecular MRI
Background:
- Inflammation in atherosclerotic lesions increases plaque instability and rupture risk.
- Accurate identification of plaque inflammation is crucial for risk stratification.
- In vivo imaging of macrophage-rich inflammation is an unmet clinical need.
Purpose of the Study:
- To evaluate ultrasmall superparamagnetic particles of iron oxide (USPIO) for in vivo magnetic resonance imaging (MRI) of carotid plaque inflammation.
- To assess the accumulation of USPIO in macrophages within atherosclerotic plaques.
- To correlate imaging findings with histological confirmation of inflammation.
Main Methods:
- Thirty patients with severe symptomatic carotid stenosis underwent multi-sequence MRI before and after USPIO injection.
- USPIO accumulation in macrophages was assessed using MRI signal intensity changes.
- MRI findings were correlated with histological analysis of carotid endarterectomy specimens.
Main Results:
- USPIO particles accumulated in macrophages in 80% of carotid plaques.
- MRI visualized USPIO/macrophage-positive areas in 89% of patients, showing an average signal intensity reduction of 24%.
- A significant correlation was observed between USPIO uptake and macrophage presence on histology.
Conclusions:
- USPIO-enhanced MRI is a viable method for in vivo detection of carotid plaque inflammation.
- USPIO accumulation within macrophages accurately identifies inflammatory sites in atherosclerotic plaques.
- This technique holds promise for assessing plaque vulnerability and guiding treatment decisions.
