Abstract
Lipid deposition inside the arterial wall is a hallmark of plaque vulnerability. Based on overtone absorption of C-H bonds, intravascular photoacoustic (IVPA) catheter is a promising technology for quantifying the amount of lipid and its spatial distribution inside the arterial wall. Thus far, the clinical translation of IVPA technology is limited by its slow imaging speed due to lack of a high-pulse-energy high-repetition-rate laser source for lipid-specific first overtone excitation at 1.7 μm. Here, we demonstrate a potassium titanyl phosphate (KTP)-based optical parametric oscillator with output pulse energy up to 2 mJ at a wavelength of 1724 nm and with a repetition rate of 500 Hz. Using this laser and a ring-shape transducer, IVPA imaging at speed of 1 frame per sec was demonstrated. Performance of the IVPA imaging system's resolution, sensitivity, and specificity were characterized by carbon fiber and a lipid-mimicking phantom. The clinical utility of this technology was further evaluated ex vivo in an excised atherosclerotic human femoral artery with comparison to histology.
Highlights
The majority of fatal acute coronary syndromes are due to plaque rupture and thrombosis [1,2,3,4]
Based on overtone absorption of C-H bonds, intravascular photoacoustic (IVPA) catheter is a promising technology for quantifying the amount of lipid and its spatial distribution inside the arterial wall
The clinical translation of IVPA technology is limited by its slow imaging speed due to lack of a high-pulse-energy high-repetition-rate laser source for lipid-specific first overtone excitation at 1.7 μm
Summary
The majority of fatal acute coronary syndromes are due to plaque rupture and thrombosis [1,2,3,4]. Among the current interventional imaging approaches, intravascular ultrasound (IVUS) lacks the chemical selectivity to determine the lipid-composition of the vessel wall [8], even for the most recently demonstrated multi-frequency IVUS method [9]. Intravascular optical coherence tomography accurately detects the surface layer of arterial wall with micron-scale resolution, but has neither sufficient imaging depth nor chemical selectivity to determine plaque composition [13]. These limitations highlight an unmet clinical need for a novel intravascular imaging system maintaining both chemical selectivity and depth resolution
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