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

Qiao Y, Hallock KJ, Hamilton JA - J Cardiovasc Magn Reson (2011)

Bottom Line: 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%).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118-2526, USA.

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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Muti-contrast MR images of fibroatherma correlated with histology. A, T1W image. B, T2W image. C, MTC, fibrous tissue is hypointense (arrow) and lipid is hyperintense (arrow head). D, DWI image. E, Polarized light microscopy (PLM) image of relevant unstained section, and bright signals indicate lipids (arrow head). F, Trichrome staining.
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Figure 3: Muti-contrast MR images of fibroatherma correlated with histology. A, T1W image. B, T2W image. C, MTC, fibrous tissue is hypointense (arrow) and lipid is hyperintense (arrow head). D, DWI image. E, Polarized light microscopy (PLM) image of relevant unstained section, and bright signals indicate lipids (arrow head). F, Trichrome staining.

Mentions: Thirty-four CEA specimens were classified according to a modified AHA classification based on histology [19]. The lesions consisted of 12 atheromatous and fibroathermatous plaques (type IV-V), 13 complex lesions with possible surface defects, and IPH (type VI), 7 calcified plaques (type VII), and 2 fibrotic plaques without a lipid core but with possible micro-calcifications. Figures 3, 4, 5 and 6 compare MTC images with other contrast mechanisms (T1W and T2W) for detecting organized proteins in different types of plaques.


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

Qiao Y, Hallock KJ, Hamilton JA - J Cardiovasc Magn Reson (2011)

Muti-contrast MR images of fibroatherma correlated with histology. A, T1W image. B, T2W image. C, MTC, fibrous tissue is hypointense (arrow) and lipid is hyperintense (arrow head). D, DWI image. E, Polarized light microscopy (PLM) image of relevant unstained section, and bright signals indicate lipids (arrow head). F, Trichrome staining.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3278375&req=5

Figure 3: Muti-contrast MR images of fibroatherma correlated with histology. A, T1W image. B, T2W image. C, MTC, fibrous tissue is hypointense (arrow) and lipid is hyperintense (arrow head). D, DWI image. E, Polarized light microscopy (PLM) image of relevant unstained section, and bright signals indicate lipids (arrow head). F, Trichrome staining.
Mentions: Thirty-four CEA specimens were classified according to a modified AHA classification based on histology [19]. The lesions consisted of 12 atheromatous and fibroathermatous plaques (type IV-V), 13 complex lesions with possible surface defects, and IPH (type VI), 7 calcified plaques (type VII), and 2 fibrotic plaques without a lipid core but with possible micro-calcifications. Figures 3, 4, 5 and 6 compare MTC images with other contrast mechanisms (T1W and T2W) for detecting organized proteins in different types of plaques.

Bottom Line: 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%).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118-2526, USA.

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.

Show MeSH
Related in: MedlinePlus