Abstract:

Catheter‐based intravascular ultrasound (IVUS) is one of the imaging tools for the clinical evaluation of atherosclerosis. However, histopathological information obtained with IVUS imaging is limited. We developed a combined intravascular photoacoustic (IVPA) and IVUS imaging to characterize atherosclerotic plaques. The amplitude, spectral, and temporal characteristics of the photoacoustic signal are primarily determined by optical absorption properties of different types of tissues and can be used to differentiate the lipid, blood, fibrous, and fibro‐cellular components of an inflammatory lesion. Furthermore, using bioconjugated contrast agents such as metal nanoconstructs, molecular IVPA imaging is possible since different molecules are overexpressed during various stages of atherosclerosis. Imaging experiments were performed using clinical IVUS imaging catheters interfaced with a pulsed laser system. The performance of the IVPA∕IVUS imaging was assessed using vessel‐mimicking phantoms. To detect the lipids in the plaque and to assess plaque composition, multi‐wavelength (680–950 nm) spectroscopic IVPA imaging of a normal and an atherosclerotic rabbit aorta was performed. Molecular and cellular IVPA imaging was demonstrated using intravenously injected plasmonic nanoparticles. Finally, IVPA imaging was used to visualize coronary stents within the vessel wall. Our studies suggest that plaque detection, characterization, and even treatment can be improved using the combined IVPA.