Simultaneous MRI water-fat separation and quantitative susceptibility mapping of carotid artery plaque pre- and post-ultrasmall superparamagnetic iron oxide-uptake.

Abstract

PURPOSE:

Imaging carotid artery plaques to identify features of vulnerability typically requires a multicontrast MRI protocol. The identification of regions of inflammation with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles requires separate pre- and postcontrast scans. We propose a method of joint water-fat separation and quantitative susceptibility mapping (QSM) to aid classification of atherosclerotic plaques and offer a positive contrast mechanism in USPIO-imaging.

METHODS:

Ten healthy volunteers (3 women and 7 men; aged, 30.7 ± 10.7 years) were imaged at 1.5T to develop an acquisition and postprocessing protocol. Five patients (1 woman and 4 men; mean age, 71 ± 7.5 years) with moderate to severe luminal stenosis were imaged pre- and postadministration of a USPIO contrast agent. We used a multiecho gradient echo acquisition to perform water/fat separation and subsequently QSM. The results were compared with a conventional multicontrast MRI protocol, CT images, and histopathology data.

RESULTS:

In the volunteer scans, a multiecho gradient echo acquisition with bipolar readout gradients demonstrated to be a reliable acquisition methodology to produce high-quality susceptibility maps in conjunction with the proposed postprocessing methodology. In the patient study, water/fat separation provided a tool to identify lipid-rich necrotic cores and QSM provided a qualitative and quantitative evaluation of plaque features and positive contrast when evaluating USPIO uptake. Plaque calcification could be identified by strong diamagnetism (-1.27 ± 0.71 ppm), while USPIO uptake demonstrated a strong paramagnetism (1.32 ± 0.61 ppm).

CONCLUSION:

QSM was able to identify multiple plaque features in a single acquisition, providing positive contrast for plaques demonstrating USPIO uptake and negative contrast for calcification.

• Authors: Pascal P R Ruetten, Alison D Cluroe, Ammara Usman, Andrew N Priest, Jonathan H Gillard, Martin J Graves
• Journal: Magnetic resonance in medicine (Magn Reson Med) Vol. 84 Issue 2 Pg. 686-697 (08 2020) ISSN: 1522-2594 [Electronic] United States
• PMID: 31961969 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2020 International Society for Magnetic Resonance in Medicine.

Chemical References

• Contrast Media
• Dextrans
• Magnetite Nanoparticles
• ferumoxtran-10
• Water

Topics

• Aged
• Carotid Stenosis (diagnostic imaging)
• Contrast Media
• Dextrans
• Female
• Humans
• Magnetic Resonance Imaging
• Magnetite Nanoparticles
• Male
• Middle Aged
• Water