Magnetization transfer magnetic resonance of human atherosclerotic plaques ex vivo detects areas of high protein density

Ye Qiao, Kevin J. Hallock, James A. Hamilton

Research output: Contribution to journalArticle

Abstract

Background: Proteins are major plaque components, and their degradation is related to the plaque instability. We sought to assess the feasibility of magnetization transfer (MT) magnetic resonance (MR) for identifying fibrin and collagen in carotid atherosclerotic plaques ex vivo. Methods. Human carotid artery specimens (n = 34) were obtained after resection from patients undergoing endarterectomy. MR was completed within 12 hr after surgery on an 11.7T MR microscope prior to fixation. Two sets of T1W spoiled gradient echo images were acquired with and without the application of a saturation pulse set to 10 kHz off resonance. The magnetization transfer ratio (MTR) was calculated, and the degree of MT contrast was correlated with histology. Results: MT with appropriate calibration clearly detected regions with high protein density, which showed a higher MTR (thick fibers (collagen type I) (54 8%)) compared to regions with a low amount of protein including lipid (46 8%) (p = 0.05), thin fibers (collagen type III) (11 6%) (p = 0.03), and calcification (6.8 4%) (p = 0.02). Intraplaque hemorrhage (IPH) with different protein density demonstrated different MT effects. Old (rich in protein debris) and recent IPH (rich in fibrin) had a much higher MTR 69 6% and 55 9%, respectively, compared to fresh IPH (rich in intact red blood cells)(9 3%). Conclusions: MT MR enhances plaque tissue contrast and identifies the protein-rich regions of carotid artery specimens. The additional information from MTR of IPH may provide important insight into the role of IPH on plaque stability, evolution, and the risk for future ischemic events.

Original languageEnglish (US)
Article number73
JournalJournal of Cardiovascular Magnetic Resonance
Volume13
Issue number1
DOIs
StatePublished - 2011
Externally publishedYes

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Atherosclerotic Plaques
Magnetic Resonance Spectroscopy
Hemorrhage
Proteins
Fibrin
Carotid Arteries
Collagen Type XI
Endarterectomy
Collagen Type I
Calibration
Histology
Collagen
Erythrocytes
Lipids

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology
  • Family Practice
  • Medicine(all)

Cite this

Magnetization transfer magnetic resonance of human atherosclerotic plaques ex vivo detects areas of high protein density. / Qiao, Ye; Hallock, Kevin J.; Hamilton, James A.

In: Journal of Cardiovascular Magnetic Resonance, Vol. 13, No. 1, 73, 2011.

Research output: Contribution to journalArticle

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abstract = "Background: Proteins are major plaque components, and their degradation is related to the plaque instability. We sought to assess the feasibility of magnetization transfer (MT) magnetic resonance (MR) for identifying fibrin and collagen in carotid atherosclerotic plaques ex vivo. Methods. Human carotid artery specimens (n = 34) were obtained after resection from patients undergoing endarterectomy. MR was completed within 12 hr after surgery on an 11.7T MR microscope prior to fixation. Two sets of T1W spoiled gradient echo images were acquired with and without the application of a saturation pulse set to 10 kHz off resonance. The magnetization transfer ratio (MTR) was calculated, and the degree of MT contrast was correlated with histology. Results: MT with appropriate calibration clearly detected regions with high protein density, which showed a higher MTR (thick fibers (collagen type I) (54 8{\%})) compared to regions with a low amount of protein including lipid (46 8{\%}) (p = 0.05), thin fibers (collagen type III) (11 6{\%}) (p = 0.03), and calcification (6.8 4{\%}) (p = 0.02). Intraplaque hemorrhage (IPH) with different protein density demonstrated different MT effects. Old (rich in protein debris) and recent IPH (rich in fibrin) had a much higher MTR 69 6{\%} and 55 9{\%}, respectively, compared to fresh IPH (rich in intact red blood cells)(9 3{\%}). Conclusions: MT MR enhances plaque tissue contrast and identifies the protein-rich regions of carotid artery specimens. The additional information from MTR of IPH may provide important insight into the role of IPH on plaque stability, evolution, and the risk for future ischemic events.",
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