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Diagnostic Tool Uses NIR to Detect Risk of Heart Attack, Stroke

Photonics.com
Aug 2017
COVENTRY, England, and MELBOURNE, Australia, Aug. 21, 2017 — When scientists increased the wavelength in a tool for detecting fatty deposit build-up in arteries from IR to NIR, they found that they could use it to selectively identify plaques with internal bleeding, which are typically associated with high-risk plaque deposits.

To investigate human atherosclerotic plaques, 50 samples were obtained exhibiting a mixture of advanced atherosclerosis including histological characteristics of unstable as well as stable plaque pathology.

Using near-infrared autofluorescence (NIRAF) for the identification of high-risk atherosclerotic plaques, researchers demonstrated that autofluorescence in the NIR range could uniquely characterize atherosclerotic plaques with intraplaque hemorrhage, and could potentially allow classification of atherosclerotic plaques into lesions indicating a low or high risk for future cardiovascular events.

Current imaging techniques are able to identify some characteristics of high-risk plaques, but none are generally accepted as reliable methods for selectively detecting the dangerous plaques.

“Despite the millions of dollars spent each year particularly on heart imaging, there still isn’t a reliable way of identifying these unstable plaques,” said professor Karlheinz Peter of Australia's Monash University. 

Researchers used Raman spectroscopy to identify the cause of fluorescence, believed to be a mixture of heme products formed during the degradation of red blood cells. These products were only observed in the unstable plaques with internal bleeding, and not observed in the more stable fatty deposits.

“We can use laser light to shine up the plaques that are unstable, and it’s very characteristic,” said Peter.

Fluorescence measurements of atherosclerotic plaques in the NIR range (650 to 900 nm) demonstrated substantial technical advantages compared to lower wavelength (325 to 475 nm) imaging, including less photon absorption, better tissue penetration and less background autofluorescence of tissues.

Because NIRAF allows in vivo monitoring of intraplaque hemorrhage, it establishes a preclinical technology to assess and monitor plaque instability and thereby test potential plaque-stabilizing drugs. After further investigation through clinical trials, this imaging technique could be used to assess unstable fatty arterial plaques and to monitor the effectiveness of the drugs used to prevent heart attacks or strokes.

“What we have done uses innovative, materials-based techniques to assist in the development of new diagnostic tools,” said Tara Schiller. “This could help us to detect the threat of an imminent heart attack and result in a decrease of the mortality rates.”

The research was performed at the University of Warwick, Monash University, Baker IDI Heart & Diabetes Institute, The Alfred Hospital, Victor Chang Cardiac Research Institute, Hudson Institute of Medical Research, and the University of New South Wales.

The research was published in Nature Communications (doi:10.1038/s41467-017-00138-x). 

Research & TechnologyeducationEuropeAsia-Pacificimaginglight sourcesfluorescence imaginglasersmedicalmedicineNIRmyocardial infarction

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