Detection of Lipid-Laden Plaques by Intravascular Ultrasound and Photoacoustic Dual-Modality Imaging

Coronary heart disease is the leading cause of death in the United States and incidence is projected to increase. Yet, there remains a clinical need for tools to detect vulnerable atherosclerotic plaques that can rupture and... [ view full abstract ]

Coronary heart disease is the leading cause of death in the United States and incidence is projected to increase. Yet, there remains a clinical need for tools to detect vulnerable atherosclerotic plaques that can rupture and lead to adverse cardiac events. Plaques that are most vulnerable for rupture are thin-capped fibroatheromas, which are defined by hallmarks of a thin fibrous cap, a large lipid-rich necrotic core, and inflammatory infiltrate. These plaques are non-obstructive to moderately obstructive, thus asymptomatic and unidentifiable with angiography and stress testing. Rather, their vulnerability is a product of their chemical composition, particularly the lipid core.
Here, we present a dual-mode intravascular catheter which is capable of producing co-registered cross-sectional images of arterial wall morphology and lipid core content via ultrasound and photoacoustic modes, respectively. A prototype of the catheter was used to image a carotid artery freshly harvested from an Ossabaw swine with dyslipidemia. Preliminary results show that vascular disease was unapparent with commercial intravascular ultrasound imaging alone (Fig.1A). However, when imaged with our ultrasound/photoacoustic dual-modality system, we detected a thin streak of lipid deposition adjacent to the subclavian artery branch (Fig.1B). We confirmed these results by repeating imaging with a commercial near-infrared spectroscopy system, which is also specific for lipids (Fig.1C). When compared to gold-standard histopathology, however, the thin streak of lipid we observe with ultrasound/photoacoustic imaging is in better agreement than near-infrared spectroscopy, which lacks spatial resolution (Fig.1D). Future studies will be extended to include interrogation of atherosclerotic human coronary arteries obtained at autopsy.