Intravascular Photoacoustic Imaging Technology Designed for Diagnosing Heart Disease

The system captures precise three-dimensional (3D) images of plaques lining arteries and identifies deposits that are prone to rupture and cause heart attacks, according to Ji-Xin Cheng, a professor in Purdue University’s (West Lafayette, IN, USA) Weldon School of biomedical engineering and department of chemistry.

The imaging technique reveals the presence of carbon-hydrogen bonds comprising lipid molecules in arterial plaques that cause heart disease. The research findings were published October 29, 2014, in the Nature journal Scientific Reports. “This allows us to see the exact nature of plaque formation in the walls of arteries so we can define whether plaque is going to rupture,” said Michael Sturek, coauthor of the study, and a professor and chair of the department of cellular and integrative physiology at Indiana University School of Medicine (Indianapolis, IN, USA). “Some plaques are more dangerous than others, but one needs to know the chemical makeup of the blood vessel wall to determine which ones are at risk of rupturing.”

Research in the area has been hampered by the inability to perform high-speed imaging in tissue. The researchers resolved this hurdle by developing a Raman laser using a laser that produces 2,000 pulses per second, each pulse capable of generating an image, representing a 100-fold increase in the imaging speed of the new technology, called intravascular photoacoustic imaging. “This innovation represents a big step toward advancing this technology to the clinical setting,” Dr. Cheng said.

The study was authored by researchers from Purdue, Indiana University School of Medicine, the University of California, Davis (USA), the University of California, Irvine (USA), and startup company Spectral Energy (Dayton, OH USA). The imaging technique is “label-free,” meaning it does not require samples to be marked with dyes, making it appealing for diagnostic applications.

The technology is being marketed by the company Vibronix, Inc. (West Lafayette, IN, USA). The laser, which pulses in the near-infrared range of the spectrum, causes tissue to heat and expand locally, generating pressure waves at the ultrasound frequency that can be captured with a device called a transducer.

The system is small enough to be integrated into an endoscope to place into blood vessels using a catheter, according to Dr. Cheng. The near-infrared laser causes enough heating to generate ultrasound but not enough to damage the tissues. The research was conducted with intact pig tissue and will expand to research with live animals and then clinical studies in humans.

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