Monitoring plaque inflammation in atherosclerotic rabbits with an iron oxide (P904) and (18)F-FDG using a combined
A Millon1, S D Dickson, A Klink
1Translational and Molecular Imaging Institute, Imaging Science Laboratories, Department of Radiology and Medicine, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA. antoinemillon@hotmail.com
Purpose:
The aim of this study was to compare the ability of (18)F-FDG PET and iron contrast-enhanced MRI with a novel USPIO (P904) to assess change in plaque inflammation induced by atorvastatin and dietary change in a rabbit model of atherosclerosis using a combined PET/MR scanner.
Materials And Methods:
Atherosclerotic rabbits underwent USPIO-enhanced MRI and (18)F-FDG PET in PET/MR hybrid system at baseline and were then randomly divided into a progression group (high cholesterol diet) and a regression group (chow diet and atorvastatin). Each group was scanned again 6 months after baseline imaging. R2* (i.e. 1/T2*) values were calculated pre/post P904 injection. (18)F-FDG PET data were analyzed by averaging the mean Standard Uptake Value (SUVmean) over the abdominal aorta. The in vivo imaging was then correlated with matched histological sections stained for macrophages.
Results:
(18)F-FDG PET showed strong FDG uptake in the abdominal aorta and P904 injection revealed an increase in R2* values in the aortic wall at baseline. At 6 months, SUVmean values measured in the regression group showed a significant decrease from baseline (p = 0.015). In comparison, progression group values remained constant (p = 0.681). R2* values showed a similar decreasing trend in the regression group suggesting less USPIO uptake in the aortic wall. Correlations between SUVmean or Change in R2* value and macrophages density (RAM-11 staining) were good (R(2) = 0.778 and 0.707 respectively).
Conclusion:
This experimental study confirms the possibility to combine two functional imaging modalities to assess changes in the inflammation of atherosclerotic plaques. (18)F-FDG-PET seems to be more sensitive than USPIO P904 to detect early changes in plaque inflammation.
Insights
Fluorodeoxyglucose positron emission tomography (FDG-PET) is more sensitive than ultrasmall iron oxide particles (USPIO P904) for detecting early changes in atherosclerotic plaque inflammation in rabbits treated with atorvastatin and diet.
Area of Science:
- Cardiovascular Imaging
- Molecular Imaging
- Atherosclerosis Research
Background:
- Atherosclerosis is characterized by inflammation within plaque.
- Assessing plaque inflammation is crucial for understanding disease progression and treatment response.
- Novel imaging techniques are needed to monitor these inflammatory changes non-invasively.
Purpose of the Study:
- To compare 18F-FDG PET and iron USPIO P904-enhanced MRI for assessing changes in atherosclerotic plaque inflammation.
- To evaluate the efficacy of atorvastatin and dietary changes on plaque inflammation using these imaging modalities.
- To utilize a combined PET/MR scanner for simultaneous functional imaging.
Main Methods:
- Atherosclerotic rabbits underwent baseline USPIO-enhanced MRI and 18F-FDG PET.
- Rabbits were randomized into progression (high cholesterol diet) and regression (atorvastatin and chow diet) groups.
- Imaging was repeated at 6 months, with analysis of SUVmean for FDG-PET and R2* values for USPIO-MRI, correlated with histology.
Main Results:
- Both 18F-FDG PET and USPIO-MRI detected aortic wall inflammation at baseline.
- The regression group showed a significant decrease in 18F-FDG uptake (SUVmean) and a trend towards decreased USPIO uptake (R2*).
- The progression group showed no significant changes in SUVmean.
- Imaging findings correlated well with macrophage density in histological analysis.
Conclusions:
- Combined PET/MR imaging can assess changes in atherosclerotic plaque inflammation.
- 18F-FDG PET demonstrated higher sensitivity than USPIO P904 in detecting early inflammatory changes.
- These findings support the use of 18F-FDG PET for monitoring anti-atherosclerotic therapies.
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