By overlapping the sound and optical waves, researchers have made artery imaging technology that is much more sensitive and detailed.

A team of researchers from the Shanghai Institute of Optics and Fine Mechanics and Purdue University has developed a tiny probe that can reveal fatty arteries in the heart with much greater detail than before. Their work was published in Scientific Reports.

As plaque accumulates on the inside of arteries, it can cause the arteries to thicken and harden. When that plaque ruptures, it can ultimately block blood flow and lead to a heart attack, stroke or other problems throughout the body.

The condition, known as atherosclerosis, is a major form of cardiovascular disease, which over the past century has become the leading cause of death worldwide. Currently, no imaging tools are available to consistently and accurately diagnose plaques at risk of rupturing in living patients.

A new imaging system known as intravascular photoacoustic (IVPA), however, promises to help doctors diagnose plaques on the brink of rupturing. IVPA produces 3D images of the insides of arteries. But scientists have struggled to develop imaging instruments that meet clinical requirements, while illuminating arteries to a useful depth and at quick enough speeds.

IVPA imaging works by measuring ultrasound signals from molecules exposed to a light beam from a fast-pulsing laser. The probe allows the optical beam and sound wave to share the same path all the way during imaging—the collinear overlap part—rather than cross overlap, as in previous designs.

The collinear overlap design increases the sensitivity and the imaging depth of the instrument, allowing for high-quality IVPA imaging of a human coronary artery over 6 mm in depth from the lumen, the normally open channel within arteries, to perivascular fat, which surrounds the outside of most arteries and veins.

“The most exciting part of this work … is the collinear design of the catheter that enables the intravascular photoacoustic imaging system to see much deeper and provide much more lipid information in the arteries,” said the first author Dr. Cao Yingchun, a postdoctoral fellow from Professor Cheng Ji-Xin’s group at Purdue University in the US.

“That could provide valuable help for the doctor to better identify and diagnose the plaque vulnerability in patients.”

The Cheng laboratory had previously tried a design based on a ring-shaped transducer to accomplish the same collinear overlap idea, but the size of the transducer prevented its further application in clinic.

The team came up with the current design by transmitting the optical wave while reflecting the sound wave on an angled surface.

“It wasn’t easy,” said Cheng. “We tried different fibers, micro mirrors, and various assembly methods. Fortunately, we finally got this idea to work.”
(Source: AsianScientist, May 20, 2016)