Highly sensitive photoacoustic catheter probe could better identify heart disease

A new photoacoustic imaging catheter can reveal fatty arteries caused by a major form of cardiovascular disease with much better detail.

An international team of researchers from Purdue University (West Lafayette, IN), the Indiana University School of Medicine (Indianapolis, IN), and the Shanghai Institute of Optics and Fine Mechanics (Shanghai, China) has developed an intravascular photoacoustic (IVPA) imaging catheter design with collinear overlap between optical and acoustic waves with a tiny probe. The design can greatly improve the sensitivity and depth of IVPA imaging, revealing fatty arteries caused by atherosclerosis (a major form of cardiovascular disease) with much better detail. The team's system meets clinical requirements while illuminating arteries to a useful depth and at quick-enough speeds, which has been challenging to address until now.

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The collinear design of the catheter enables the IVPA imaging system to see much deeper and much more lipid information in the arteries, which could allow doctors to better identify and diagnose the plaque vulnerability in patients, explains Yingchun Cao, a postdoctoral fellow in Professor Ji-Xin Cheng's group at Purdue University and first author of the paper describing the work.

IVPA imaging works by measuring ultrasound signals from molecules exposed to a light beam from a fast-pulsing laser. The new probe allows the optical beam and sound wave to share the same path all the way during imaging (collinear overlapping) rather than cross-overlap as in previous designs. This 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 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 the clinic. The team came up with the current design by transmitting the optical wave while reflecting the sound wave on an angled surface.

The research team will present their study at the Conference on Lasers and Electro-Optics (CLEO), to be held June 5-10, 2016, in San Jose, CA. The study, titled "Highly Sensitive Intravascular Photoacoustic Imaging with a Collinear Catheter Probe," will be presented from 5:45-6 p.m. on Thursday, June 9th in the Salon I and II of the Marriott San Jose hotel.

The study has also been published in the journal Scientific Reports; for more information, please visit http://dx.doi.org/10.1038/srep25236.

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