ABSTRACT
A variety of catheter-based techniques have been investigated for the detection of unstable plaque. Recent advances in intravascular ultrasound (IVUS), including the use of high-frequency transducers11, radiofrequency signal processing12 and integrated backscatter IVUS13, have improved the capability of IVUS for the assessment of plaque components. Studies have also demonstrated the capability of intravascular MRI in plaque characterization14. However, the limited resolution of both IVUS and intravascular MRI inhibits the evaluation of microstructural features such as fibrous caps. Recent advances in optical diagnostic techniques have demonstrated the use of light for plaque characterization. Infrared and Raman spectroscopy evaluate the spectrum of light reflected from the vessel wall to provide spectroscopic information about lipid, collagen and cholesterol crystals15,16. These methods provide composite information of bulk plaque constituents by averaging the detected signal measured over the illuminated volume. Due to the large amount of optical scattering by atherosclerotic plaque tissue, high-resolution depth-resolved information is difficult to obtain with these techniques.
