P0-2 Spectroscopic Intravascular Photoacoustic Imaging

Intravascular photoacoustic (IVPA) imaging has the potential to detect atherosclerotic plaques. Previously, we obtained IVPA images using a 532 nm pulsed laser and a 40 MHz intravascular ultrasound (IVUS) imaging catheter. The optical absorption of light by the plaque components was used as a contrast mechanism helpful in detecting the plaque. However, plaque differentiation requires a method to remotely assess plaque composition. We hypothesized that plaque characterization can be performed by monitoring the changes in photoacoustic response with the change in laser excitation wavelength. In this preliminary study, we performed spectroscopic IVPA imaging to analyze the change in the photoacoustic response of the aortic tissue (a rabbit aorta with plaque and a control aorta) using different laser excitation wavelengths. Specifically, we perform IVPA imaging at multiple wavelengths within 680-900 nm range. The slope of the spectral change in photoacoustic response was computed between selected wavelengths to produce a spectroscopic IVPA image. The results of our study suggest the ability of the multi-wavelength IVPA imaging to identify and differentiate the fibrous, lipid and blood components of the atherosclerotic plaque.