Hypointensity on Carotid Plaque MRI and Its Relationship to Calcification: Histopathologic Validation With...

Area of Science:

• Biomedical Imaging
• Medical Diagnostics
• Cardiovascular Research

Background:

• Conventional carotid plaque MRI often misidentifies hemosiderin as calcification due to similar signal characteristics.
• This ambiguity raises concerns about the accuracy of substrate characterization in atherosclerotic plaques.

Purpose of the Study:

• To assess the ability of quantitative susceptibility mapping (QSM) to differentiate hemosiderin from calcification in carotid atherosclerotic plaques.
• To validate QSM findings against direct histopathologic correlation using ex vivo MRI.

Main Methods:

• Ex vivo MRI of 24 carotid endarterectomy specimens using 3T MRI, including multi-echo FLASH-based QSM.
• Histopathologic analysis with hematoxylin-eosin, von Kossa (calcification), and Berlin blue (hemosiderin) staining.
• Comparison of contrast-to-noise ratios (CNR) on conventional sequences and relative susceptibility values (rSV) on QSM.

Main Results:

• Conventional MRI sequences showed significant signal overlap between calcification and hemosiderin.
• QSM demonstrated distinct susceptibility values: positive rSVs for hemosiderin (506.8 ± 320.5 ppb) and negative rSVs for calcification (-440.5 ± 296.3 ppb).
• No polarity overlap was observed between hemosiderin and calcification using QSM, with statistically significant group differences.

Conclusions:

• Hypointensity on conventional MRI is not a reliable indicator of calcification at the substrate level in carotid plaques.
• Quantitative susceptibility mapping (QSM) provides robust differentiation between calcification and hemosiderin, validated by histopathology.