Monitoring the effect of surgical treatment of carotid atherosclerosis using Raman spectroscopy

Raman spectroscopy was investigated as a tool for monitoring post-operative recovery in patients suffering from carotid atherosclerosis. Principal Component Analysis (PCA) of the full Raman spectrum revealed that it is challenging to differentiate between serum samples collected before surgery and those taken 24 or 48 h after surgery. Furthermore, there was no clear separation observed between the 24-h and 48-h post-surgery samples. The first principal component (PC1) accounted for 67.52% of the total variance, while the second principal component (PC2) explained 14.22%. The loading plot for PCA demonstrated that PC1 had positive values in the spectral range of 800-1800 cm^-1 and negative values between 2800 and 3000 cm^-1, while PC2 had positive values in the 800-1600 cm^-1 and 2800-3000 cm^-1 ranges and negative values between 1600 and 1800 cm^-1. These variations highlight the molecular vibrations in proteins and lipids but did not provide clear classification based on the time points. Significant wavelength ranges were identified to distinguish biochemical changes between different time points post-surgery. For samples taken before surgery and 24 h after surgery, the most relevant intervals were 930-945 cm^-1, 982-1002 cm^-1, 2930-2954 cm^-1, and 2978-2991 cm^-1, associated with lipids, proteins, and carbohydrates. Similarly, for the pre-surgery and 48-h post-surgery comparison, slightly shifted wavelength ranges were identified, showing subtle differences that reflect recovery and tissue remodeling. Hierarchical Cluster Analysis (HCA) and PCA performed for these ranges confirmed these findings, where clear distinctions were observed for the pre-surgery and 24-h post-surgery samples, but the differentiation between the 24-h and 48-h post-surgery samples was less pronounced, indicating that the biochemical composition stabilizes after 48 h.