Photoacoustic imaging of the arteries can provide valuable functional information to diagnose and classify atherosclerotic plaques. When combined with ultrasound for anatomical information, photoacoustic imaging holds promise for routine monitoring and for treatment decisions. However, utilizing conventional ultrasound systems for combined photoacoustic and ultrasound imaging has not been successful for this application. In this study, we imaged two major arteries susceptible to atherosclerosis—the carotid artery and the femoral artery—using a linear array-based system. Our results demonstrate the feasibility of imaging the carotid artery at depths of up to 10 mm and the femoral arteries at up to 20 mm. The average success rates for imaging the carotid, common femoral and superficial femoral arteries in healthy volunteers were 75%, 100% and 33.3%, respectively, demonstrating potential for future studies.

Spectral photoacoustic imaging in combination with unmixing techniques may be applied to retrieve information about high-risk features present in atherosclerotic plaques, possibly providing prognostic insights into future stroke events. We present the photoacoustic spectral contrast found in 12 systematically scanned advanced atherosclerotic plaques in the near-infrared wavelength range (850–1250 nm). The main absorbers are lipid, water, and hemoglobin, with the highest photoacoustic intensities at the lipid's second overtone at 1190 and 1210 nm. Linear unmixing resulted in visualizing regions with high lipid and hemoglobin absorption, corresponding to the histological presence of lipid and intraplaque hemorrhage. A non-negative matrix factorization approach reveals differences in lipid spectral contrast, providing potential insights into the vulnerability of atherosclerotic plaque. These results provide a reference for future, more complex, in vivo photoacoustic imaging of carotid artery atherosclerosis, potentially contributing to assessing the risk of future events and treatment decision.