Multispectral photoacoustic analysis of intraplaque hemorrhage in human carotids

Carotid intraplaque hemorrhage (IPH) is a significant risk factor for cardiovascular events, including stroke, alongside the carotid morphology, such as plaque thickness and stenosis severity. Although MRI is effective in identifying IPH and assessing carotid morphology, its high cost and long examination time hinder its use for early diagnosis. To overcome these limitations, we employed a multispectral photoacoustic and ultrasound (PA/US) imaging system to visualize and evaluate IPH and carotid morphology noninvasively. Multispectral PA imaging measured mean PA amplitude (PAmean), PA IPH area size (PAIPH_area), and PA percent concentration of methemoglobin (PAPCmet), while US imaging assessed plaque thickness and stenosis severity. Patients with US plaque thickness ≥2 mm underwent PA/US imaging. PA analyses identified IPH using PAmean and PAIPH_area and determined its stages with PAPCmet. These results were compared with US-based morphological features and validated against MRI findings. We reveal that carotids with IPH exhibited significantly greater US plaque thickness. PAPCmet is positively correlated with USstenosis_severity, PAmean, and PAIPH_area. Validation with MRI-based diagnosis demonstrated strong agreement for IPH detection, no significant difference in IPH area measurement, a significant correlation between PAPCmet and MRI-based IPH stage estimation, equivalent diagnosis performance for stenosis severity, plaque thickness, and calcification detection. These results suggest multispectral PA/US imaging offers a reliable and cost-effective alternative to MRI for carotid IPH and morphology diagnosis. It provides strong correlations with morphological characteristics and enhances early and precise assessment of carotid atherosclerosis progression.