Raman spectroscopy for quantifying cholesterol in intact coronary artery wall

Area of Science:

• Biomedical Engineering
• Chemical Pathology

Background:

• Vascular lesion chemical composition impacts plaque progression and rupture.
• Current in vivo methods cannot determine plaque composition.
• Raman spectroscopy shows promise for quantifying lipids and calcium in homogenized tissue.

Purpose of the Study:

• To determine the relationship between relative cholesterol content and depth in intact arterial walls.
• To assess cholesterol signal attenuation by overlying tissue using Raman spectroscopy.
• To validate Raman spectroscopy for in vivo cholesterol quantification in atherosclerotic plaques.

Main Methods:

• Raman spectra of human atherosclerotic plaques were analyzed after sequential tissue layer removal.
• Relative cholesterol content was calculated from spectral data.
• Intact plaque samples were spectroscopically analyzed, sectioned, stained for cholesterol, and imaged.
• Spectroscopic and digital microscopy data were compared, accounting for tissue depth.

Main Results:

• A decaying exponential curve (r2 = 0.97) demonstrated that ~300 microm of tissue attenuates cholesterol signals by 50%.
• Spectroscopically-determined cholesterol amounts strongly and linearly correlated with digital microscopy results (r2 = 0.94) in intact plaques.
• Cholesterol content can be accurately determined by accounting for tissue depth.

Conclusions:

• Raman spectroscopy, with depth-correction, can quantify cholesterol in arterial lesions.
• This technique offers potential for mapping the chemical composition of artery walls in vivo.
• Combining Raman spectroscopy with other methods could enable comprehensive arterial wall chemical mapping.