Three methods for accurate quantification of plaque volume in coronary arteries.

The coronary atherosclerotic process evolves to an occlusive disease that causes chronic angina and acute coronary syndromes, such as myocardial infarction and sudden death. An important milestone in the understanding of the atherosclerotic process is the development of tools for quantitative assessment of disease progression or regression. A new methodology to analyze the coronary vessel lumen and plaque morphology in 3-D is based on the fusion of intravascular ultrasound (IVUS) and biplane X-ray angiography, which results in a geometrically correct representation of coronary vessels. A comparison of three volume quantification methods: polytope, Watanabe, and Simpson's rule is reported for quantifying the amount of plaque accumulation. The three methods allow local estimation of plaque volume. To determine volumetric indices, the space between the luminal and adventitial surfaces is first subdivided and then each of the volume elements is considered individually to achieve volume quantification. Polyhedral volume elements are employed and the volume of every element is estimated by each of the three approaches. The volume quantification methods were validated in 314 computer-generated shapes. All three methods are highly accurate, providing a mean error of 0.138 +/- 0.049%, 0.139 +/- 0.049%, and 0.832 +/- 0.203% for the polytope, Watanabe, and Simpson-rule methods, respectively. Nevertheless, the polytope and Watanabe methods are statistically significantly more accurate than the Simpson-rule approach (p < 0.001). The volumetric quantification methods were also tested using seven in vivo coronary arterial datasets from seven patients undergoing coronary angioplasty. While the polytope and Watanabe approaches are statistically significantly more accurate compared to the Simpson's rule method, accuracy of either of the tested method is sufficient for all practical purposes. Yet, the methods are not interchangeable and a single technique should be used in comparative volumetric studies.