Photoacoustics Exposes Arterial Plaques

Measuring ultrasound signals generated by a fast-pulsing laser inside an artery could advance diagnosis of cardiovascular disease.

A new technique called intravascular photoacoustic imaging takes precise 3-D images and reveals the presence of carbon-hydrogen bonds making up lipid molecules in arterial plaques that cause heart disease.

Researchers from Purdue University developed the technology in collaboration with the Indiana University School of Medicine, the University of California, Davis, the University of California, Irvine, and startup company Spectral Energies.

This cross section of an artery shows lipid deposits in green. Courtesy of Ji-Xin Cheng/Purdue University Weldon School of Biomedical Engineering.

The system uses a Raman laser that produces 2000 near-infrared pulses per second.

“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 Indiana professor Dr. Michael Sturek. “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.”

The laser causes tissue to heat and expand, generating pressure waves at the ultrasound frequency that can be picked up with a transducer device. The process does not damage tissue.

The technique does not require samples to be marked with dyes, making it well suited for diagnostic applications, and the laser is small enough to be incorporated into an endoscope to put into blood vessels using a catheter, said Purdue professor Dr. Ji-Xin Cheng.

This study was conducted on intact pig tissue; the researchers hope to expand it with live animals and ultimately in clinical studies with humans.

The technology will be commercialized by Vibronix Inc., co-founded by Cheng and Pu Wang, a postdoctoral research associate at Purdue. A U.S. patent application has been filed by the Purdue Office of Technology Commercialization.

The work was funded by the National Institutes of Health and the American Heart Association. The research was published in Scientific Reports (doi: 10.1038/srep06889).

For more information, visit www.purdue.edu.