A new non-invasive technique that could identify early signs of heart disease has been developed by scientists.
People who suffer a heart attack have non-calcified plaque, a build-up of soft deposits embedded deep within the walls of the heart's arteries, undetectable by angiography or cardiac stress tests, and prone to rupture without warning.
The new study led by a team from Beth Israel Deaconess Medical Centre (BIDMC) used voxel analysis in combination with MDCTA (multi-detector computed tomography angiography)
The technique was shown to be equally as effective as catheter coronary angiography in identifying patients at risk for heart disease.
The researchers believe that the new results may help doctors monitor the effects of medical treatment to reduce patients' risk of atherosclerosis and heart disease.
"The importance of quantifying plaque is critical because total plaque burden is considered the most important predictor of coronary events," said the study's senior author Dr Melvin Clouse, Emeritus Chairman of the Department of Radiology and Director of Radiology Research at BIDMC and Deaconess Professor of Radiology at Harvard Medical School.
"Furthermore, the rupture of soft non-calcified plaque has been implicated as the cause of heart attack," he added.
Exercise stress testing and coronary angiography, the standard methods for diagnosing atherosclerosis and heart attack risk, both work by visualizing the lumen, the channel through which blood flows.
As lumen increases in size as plaque progresses, conventional angiography and stress tests fail to provide a complete picture of plaque accumulation.
The CT scanning method with 64 separate scans, provides a detailed cross-sectional view of the blood vessel wall based on the amount and volume of blockage present.
Its ability to differentiate plaque density makes it particularly useful in distinguishing between stable plaque and unstable plaque.
"The latest MDCT scanners have made it possible to detect non-calcified plaque," said Clouse.
The researchers analysed 41 normal and eight abnormal arterial cross sections with non-calcified plaque selected from 10 patients undergoing MDCTA.
"Voxel analysis estimates the volume of plaque in a blood vessel based on a range of volumetric densities," said Clouse.
Within the selected volume, the number of voxels having a density within the range of plaque is established, from which the volume of plaque is then estimated. (In CT scans, voxel values are Hounsfield units, which give the opacity of material to X-rays). The detailed measurements, nearly 2,300 in total, provided physicians with a detailed picture of the coronary arteries and surrounding areas.
"By plotting a voxel histogram across the arterial wall, we were able to measure the amount of plaque, as well as the narrowing of the artery," Clouse added.
Clouse believes that using this new method, they would be able to better assess the effects of medication treatment and lifestyle interventions in treating atherosclerosis.
The findings are reported in the June 2008 issue of the American Journal of Roentgenology (AJR).