Utility of Fluorescence Lifetime Imaging Microscopy in the Detection of Atherosclerosis

Background: Atherosclerosis is a chronic disease that is an important public health problem. Early diagnosis of this disease can prevent serious consequences. Fluorescence lifetime imaging microscopy (FLIM) is a new method of imaging that utilizes the intrinsic fluorescence of tissues. In this study, the utility of FLIM in classifying various regions of atherosclerotic plaques was studied as a potential method of early diagnosis.

Methods: Atherosclerotic plaques from carotid arteries obtained surgically were imaged using FLIM. Regions of the plaque rich in specific substances were classified according to their fluorescence lifetime and the lifetime of each tissue was calculated. Additionally, lifetimes of certain region types within each tissue were calculated. The diverse tissue types identified by FLIM were confirmed by conventional histological methods.

Results: The following lifetimes were calculated for various tissue types: Fibrous capsules 989 ± 244 ps ; fibrin rich regions 936 ± 126 ps; lipid rich regions 333 ± 86 ps. Certain runs showed contrast in the FLIM image but not in the intensity image. Histopathology concurrence with FLIM results was 100%.

Conclusions: These results support the utility of FLIM for the diagnosis of atherosclerosis. The average lifetimes for fibrin rich and lipid rich regions being significantly different from that of whole tissue has important implications in clinical imaging. It has potential for the detection of macrophage infiltration in atherosclerotic lesions, a key marker of plaque vulnerability. Therefore, FLIM offers a new method of contrast for the diagnosis of atherosclerosis that has wide applicability in clinical preventive medicine.