A method for measuring the variation of intima-media thickness during the entire cardiac cycle using B-Mode images

Increased intima-media thickness (IMT) has been shown to predict cardiovascular risk, and measurement of intima-media thickness has been extensively used in medical research since the mid-1990s. IMT is conventionally measured by manual tracing, however this method is very time-consuming and suffers from large inter-observer variability. Numerous methods, both semi-automatic and fully-automatic, have been suggested to limit the influence of the observer. However, most methods only report one value per cardiac cycle instead of the variation of IMT over time. We propose a new method that measures the variation of IMT during the entire cardiac cycle. The method tracks spatial variations with compensation for both longitudinal movement and angle variations. This enables detection of positions where an inaccurate measurement of IMT has occurred. These can then be removed from the calculations in order to maximize the accuracy. The method was evaluated in vivo on 20 healthy individuals (mean age 38 years, range 25-57). The overall IMT in diastole (IMTdia) was 717+/-69 mu m and the intima-media compression (IMC) was 66+/-21 mu m which corresponds to a 9.2+/-2.6% maximal compression of the arterial wall during a cardiac cycle. The CV was 3.5% for IMTdia and 9.9% for IMC. Extending traditional IMT measurement to include also the variation of IMT during a cardiac cycle may improve the individual risk classification for cardiovascular diseases.