High-speed intravascular photoacoustic imaging of lipid-laden atherosclerotic plaque enabled by a 2-kHz barium nitrite Raman laser

Authors:  P. Wang, T. Ma, M. N. Slipchenko, S. Liang, J. Hui, K. K. Shung, S. Roy, M. Sturek, Q. Zhou, Z. Chen and J.-X. Cheng

Journal:  Scientific Reports 4: 6889 (2014)

SUMMARY

An unmet clinical need exists to detect unstable plaque in cardiovascular disease, the number one cause of death in the United States. Vulnerable plaques have a high risk of rupture and thrombosis which account for the majority of fatal acute coronary syndromes. Currently, no imaging tools exist to reliably and accurately diagnose a vulnerable plaque in live patients; instead, only autopsies can reveal ruptured lipid-laden thin fibrous cap atheromas. Current interventional imaging procedures include: intravascular ultrasound, intravascular near-infrared spectroscopy, intravascular fluorescence imaging, and intravascular optical coherence tomography.

Photoacoustic endoscopy, which utilizes the optical absorption properties of tissue composition as contrast, could bridge the unmet need for a novel intravascular imaging system which possesses chemical selectivity and depth resolution. Using a 2-kHz barium nitrite Raman laser, the authors built a high repetition rate laser system that enabled intravascular photoacoustic (IVPA) imaging of lipid-laden plaque with a 1Hz frame rate, which is nearly two orders of magnitude faster than other reported systems.

IMPACT

Lipid deposition inside the arterial wall is a key indicator of plaque vulnerability. An intravascular photoacoustic (IVPA) catheter is considered a promising device for quantifying the amount of lipid inside the arterial wall. Thus far, IVPA systems suffered from slow imaging speed due to the lack of a suitable laser source for high-speed excitation of molecular overtone vibrations. The authors report on an improvement in IVPA imaging speed by two orders of magnitude enabled by a custom-built, 2-kHz master oscillator power amplifier (MOPA)-pumped, barium nitrite Raman laser. This advancement narrows the gap in translating IVPA technology to the clinical setting.