由 Carol Ko
, Staff Writer | November 14, 2013
A novel imaging technique that identifies high-risk plaque associated with heart attacks made headlines this week — but this technology is just one of several such tests in the works.
Researchers at the University of Edinburgh in Scotland tested the use of PET/CT with radioactive tracer sodium fluoride (NaF) to identify high-risk plaque that had either already ruptured or was at risk for rupture.
"It's the first study that shows that with a simple hour and a half test, we could evaluate the blockages that are at the highest risk of rupturing and worsening," said Dr. Gregory Thomas, medical director for the MemorialCare Heart & Vascular Institute at Long Beach Memorial in California, who authored an editorial on the Edinburgh study.
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But this isn't the only plaque imaging technique of its kind — near infrared spectroscopy and optical coherence tomography also aim to identify high-risk plaque and help doctors prevent heart attacks before they occur.
What complicates comparisons between these different tests is that scientists still haven’t reached full consensus on what constitutes high-risk plaque.
While scientists are able to identify certain common characteristics in unstable plaque — such as elevated levels of microcalcification, inflammation and cell injury and death — they are still unable to pinpoint what exactly causes this culprit plaque to rupture.
Furthermore, it’s very difficult to establish whether this plaque is definitively responsible for causing heart attacks, since scientists can only identify and study the plaque before and after the cardiac event, not during.
For example, prior autopsy studies had established that ruptured lipid core plaque, a type of high-risk plaque, was present in most heart attack patients and was strongly suspected to be the cause of heart attacks.
But in July, DOTmed News reported
on a study in which researchers were able to spot lipid core plaque in living patients for the first time using a technique called near infrared spectroscopy. However, further studies need to be done before researchers are able to establish that lipid core plaque imaging can accurately predict heart attacks.
The advantage of this test lies in its speed and automation — the image is available within seconds after pullback from the artery. It’s also easy to read.
Another imaging technique called optical coherence tomography takes a different approach to vulnerable plaque imaging by enabling doctors to assess the thickness of the fibrous cap, a layer of connective tissue found in high-risk plaque which is prone to rupture and instability. Unlike near infrared spectroscopy, however, accurate reading of the images largely depends on the skill and experience of the observer.