17 Vibrational Microspectroscopy for Analysis of Atherosclerotic Arteries
521
like intraplaque hemorrhage and thrombotic plaques (plaques exhibiting a luminal thrombus) are considered as having a huge impact on plaque vulnerability (see
Chap. 3.2.1.2.) [47, 86].
In Search of vulnerable plaque spectroscopic features
one of the most important goals of Raman spectroscopy is the identification and detection of unstable, vulnerable plaque. In order to do this, the morphological markers of vulnerable atherosclerotic plaque should be described [102]. Both IR [73,
103] and Raman [47, 86, 104, 105] spectroscopies were developed for studying the
composition of plaque and detecting vulnerable plaque. As shown previously, the
chemical composition along with the morphology can provide more information
about plaque stability than the degree of stenosis [87, 106]. therefore, it seems
that the combination of vibrational spectroscopy with staining should be the perfect
solution to this problem.
the most basic statement claims that unstable plaque is defined as a thin fibrous
cap overlying a large pool of necrotic lipid-rich material with high risk of rupture
[2, 73, 82, 87, 105, 107, 108] (see Chap. 4.2.). It has been shown that such features
as intraplaque hemorrhages and thrombotic plaques (plaques exhibiting a luminal
thrombus) are also considered to have a considerable impact on plaque vulnerability [73, 109]. other possible observations are the activated macrophages near the
fibrous cap, inflammation, reduced collagen synthesis, local overexpression of collagenase and smooth muscle cell apoptosis [105].
Such a description clears up why the evaluation of vulnerable plaque was not
encountered during in vitro studies. this is explained by the fact that some species,
like intraplaque hemorrhagic and hemoglobin concentration in plaque, have a huge
role in defining vulnerable plaque and can be correctly observed only in vivo [47].
Raman spectroscopy allows for the detection not only of the cholesterol and
calcium mineralization, but [86, 110] also such morphologic features as fibrous cap
[111], necrotic core/foam cells [73], ceroid presence and its formation [112, 113],
hemoglobin (Hb), β-carotene (not present in all plaques [114]) and thrombus on the
surface of plaque [73, 105]. the ability to detect this wide array of features makes
Wa v e n u m -
ber [cm
−1
]
mode assignment
Compound
assignment
Aorta/plaque part
Ref.
2870
Ch 3 symmetric
stretching
Crystalline cholesterol—unesterfied
(free) cholesterol
Foam cells/necrotic
core
[93, 101]
2885
Fermi resonance
Ch 2 stretching
Cholesterol esters
Foam cells/necrotic
core
[93]
2933–2945 symmetric Ch 3 /assymmetricCh 2 /out-ofplane chain
Crystalline cholesterol—unesterfied
(free) cholesterol
Foam cells/necrotic
core
[93, 101]
Table 17.1 (continued)
521
like intraplaque hemorrhage and thrombotic plaques (plaques exhibiting a luminal thrombus) are considered as having a huge impact on plaque vulnerability (see
Chap. 3.2.1.2.) [47, 86].
In Search of vulnerable plaque spectroscopic features
one of the most important goals of Raman spectroscopy is the identification and detection of unstable, vulnerable plaque. In order to do this, the morphological markers of vulnerable atherosclerotic plaque should be described [102]. Both IR [73,
103] and Raman [47, 86, 104, 105] spectroscopies were developed for studying the
composition of plaque and detecting vulnerable plaque. As shown previously, the
chemical composition along with the morphology can provide more information
about plaque stability than the degree of stenosis [87, 106]. therefore, it seems
that the combination of vibrational spectroscopy with staining should be the perfect
solution to this problem.
the most basic statement claims that unstable plaque is defined as a thin fibrous
cap overlying a large pool of necrotic lipid-rich material with high risk of rupture
[2, 73, 82, 87, 105, 107, 108] (see Chap. 4.2.). It has been shown that such features
as intraplaque hemorrhages and thrombotic plaques (plaques exhibiting a luminal
thrombus) are also considered to have a considerable impact on plaque vulnerability [73, 109]. other possible observations are the activated macrophages near the
fibrous cap, inflammation, reduced collagen synthesis, local overexpression of collagenase and smooth muscle cell apoptosis [105].
Such a description clears up why the evaluation of vulnerable plaque was not
encountered during in vitro studies. this is explained by the fact that some species,
like intraplaque hemorrhagic and hemoglobin concentration in plaque, have a huge
role in defining vulnerable plaque and can be correctly observed only in vivo [47].
Raman spectroscopy allows for the detection not only of the cholesterol and
calcium mineralization, but [86, 110] also such morphologic features as fibrous cap
[111], necrotic core/foam cells [73], ceroid presence and its formation [112, 113],
hemoglobin (Hb), β-carotene (not present in all plaques [114]) and thrombus on the
surface of plaque [73, 105]. the ability to detect this wide array of features makes
Wa v e n u m -
ber [cm
−1
]
mode assignment
Compound
assignment
Aorta/plaque part
Ref.
2870
Ch 3 symmetric
stretching
Crystalline cholesterol—unesterfied
(free) cholesterol
Foam cells/necrotic
core
[93, 101]
2885
Fermi resonance
Ch 2 stretching
Cholesterol esters
Foam cells/necrotic
core
[93]
2933–2945 symmetric Ch 3 /assymmetricCh 2 /out-ofplane chain
Crystalline cholesterol—unesterfied
(free) cholesterol
Foam cells/necrotic
core
[93, 101]
Table 17.1 (continued)