T.P. Wróbel et al.
530
to be influenced by iNoS, however, a protein nitration possibility was indicated in
the plaque region. the total amount of lipids in the ApoE
−/−
strain was found to be
higher, therefore showing an influence of iNoS to lesion formation. moreover, the
lipid composition balance was shifted to higher free cholesterol content in iNoS
gene deficient mice. Last article describes an ingenious experiment in which diffusion of drugs into the aorta was studied [65]. A section of tissue was placed on top
of macro-AtR crystal and time-resolved measurements were performed after adding a solution of benzyl nicotinate or ibuprofen. It was found that benzyl nicotinate
has a higher affinity toward atherosclerotic plaque than to healthy tissue. Ibuprofen
was introduced within a solution of albumin, which acted as a drug carrier, which
otherwise caused ibuprofen not to enter the tissue.
Classification Raman capabilities for in situ measurements of the aorta endoscopically inspired a similar experiments to be performed with an AtR catheter [4, 62].
the idea is to correctly classify the whole aorta to a certain grade of atherosclerosis progression based solely on a single spectrum obtained in a single measurement. this purpose requires use of more advanced multivariate techniques such
as Partial Least Squares—discriminant Analysis (PLS-dA) or mahalonobis distance—Linear discriminant Analysis (md-LdA). Both of the approaches gave
very promising results in the experiment performed on rabbit tissue [62] giving prediction accuracy of 100 %, however, no external validation set was used due to limited number of available samples. this renders the results not fully reliable, yet the
experiment show the great potential of using AtR catheters beside Raman probes.
17.4 Conclusion
this chapter constitutes the review of the selected IR and Raman publications,
which focus on atherosclerotic plaque analysis and presents couple of examples
from our studies in this field. there is no doubts, that vibrational spectroscopy is
able to distinguish morphological and biochemical changes which occurs in atherosclerotic plaques.
Ft-IR spectroscopy provides information mainly about the concentration of lipids and concentration and structure of proteins. unique profiles of amide I and II
bands allow to estimate the content of secondary structures of proteins, as well as
distinguish between collagen of type I, III and elastin. different modes of IR measurements were successfully used in atherosclerotic tissues studies (transmission,
macro-AtR and micro-AtR imaging) to determine such plaque features as protein
profiles (mainly elastin) and lipid deposits.
Raman spectroscopy provides more specific identification of plaque contents.
this method is able to distinguish such plaque features as: fibrous cap, internal
elastic lamina, collagen fibers, smooth muscle cells, adventitial fat, necrotic core/
foam cells, ceroid, thrombus on the surface of plaque, intraplaque hemorrhagic, carotene crystals, and calcification. Such recognition is based on the chemical differences between such groups of chemicals as: collagen, elastin, cholesteryl esters, free
530
to be influenced by iNoS, however, a protein nitration possibility was indicated in
the plaque region. the total amount of lipids in the ApoE
−/−
strain was found to be
higher, therefore showing an influence of iNoS to lesion formation. moreover, the
lipid composition balance was shifted to higher free cholesterol content in iNoS
gene deficient mice. Last article describes an ingenious experiment in which diffusion of drugs into the aorta was studied [65]. A section of tissue was placed on top
of macro-AtR crystal and time-resolved measurements were performed after adding a solution of benzyl nicotinate or ibuprofen. It was found that benzyl nicotinate
has a higher affinity toward atherosclerotic plaque than to healthy tissue. Ibuprofen
was introduced within a solution of albumin, which acted as a drug carrier, which
otherwise caused ibuprofen not to enter the tissue.
Classification Raman capabilities for in situ measurements of the aorta endoscopically inspired a similar experiments to be performed with an AtR catheter [4, 62].
the idea is to correctly classify the whole aorta to a certain grade of atherosclerosis progression based solely on a single spectrum obtained in a single measurement. this purpose requires use of more advanced multivariate techniques such
as Partial Least Squares—discriminant Analysis (PLS-dA) or mahalonobis distance—Linear discriminant Analysis (md-LdA). Both of the approaches gave
very promising results in the experiment performed on rabbit tissue [62] giving prediction accuracy of 100 %, however, no external validation set was used due to limited number of available samples. this renders the results not fully reliable, yet the
experiment show the great potential of using AtR catheters beside Raman probes.
17.4 Conclusion
this chapter constitutes the review of the selected IR and Raman publications,
which focus on atherosclerotic plaque analysis and presents couple of examples
from our studies in this field. there is no doubts, that vibrational spectroscopy is
able to distinguish morphological and biochemical changes which occurs in atherosclerotic plaques.
Ft-IR spectroscopy provides information mainly about the concentration of lipids and concentration and structure of proteins. unique profiles of amide I and II
bands allow to estimate the content of secondary structures of proteins, as well as
distinguish between collagen of type I, III and elastin. different modes of IR measurements were successfully used in atherosclerotic tissues studies (transmission,
macro-AtR and micro-AtR imaging) to determine such plaque features as protein
profiles (mainly elastin) and lipid deposits.
Raman spectroscopy provides more specific identification of plaque contents.
this method is able to distinguish such plaque features as: fibrous cap, internal
elastic lamina, collagen fibers, smooth muscle cells, adventitial fat, necrotic core/
foam cells, ceroid, thrombus on the surface of plaque, intraplaque hemorrhagic, carotene crystals, and calcification. Such recognition is based on the chemical differences between such groups of chemicals as: collagen, elastin, cholesteryl esters, free