SIMPSONS RULE FOR THE VOLUMETRIC ULTRASOUND ASSESSMENT OF ATHEROSCLEROTIC CORONARY-ARTERIES - A STUDY WITH ECG-GATED 3-DIMENSIONAL INTRAVASCULAR ULTRASOUND

Background Volumetric intravascular ultrasound (IVUS) assessment provi des complementary information on atherosclerotic plaques. The volumes can be calculated by applying Simpson's rule to cross-sectional area d ata of multiple IVUS images, acquired with a fixed sample spacing, whi ch is the distance (along the vessel's axis) between two images. Objec tive To evaluate the effect of different sample spacings on the result s of volumetric IVUS measurements. Methods A stepwise electrocardiogra phically gated IVUS image-acquisition and automated three-dimensional analysis approach was applied to 26 patients. Twenty-eight coronary se gments with mild-to-moderate coronary atherosclerosis were examined, V olumetric measurements of five images per mm (i.e. sample spacing 0.2 mm), representing a complete scanning of the coronary segment, were co nsidered the optimal standard, against which volumetric measurements o f three, one, and one-half images per mm (i.e. larger sample spacings) were compared. Results The lumen, total vessel, and plaque volumes ob tained with five images per mm were 183.3 +/- 2.8, 350.6 +/- 141.6, an d 167.3 +/- 89.2 mm(3), There was an excellent correlation (r = 0.99, P < 0.001) between these data and volumetric measurements with larger sample spacings, The volumetric measurements with larger sample spacin gs differed on average only by a little (< 0.7%) from the optimal stan dard measurements. However, a relatively small, but significant, incre ase in SD of these differences was associated with the wider sample sp acings (< 3.6%, P< 0.05). Conclusions The width of the sample spacing has a relatively small but significant impact on the variability of vo lumetric intravascular ultrasound measurements, This should be conside red when designing future volumetric studies, The electrocardiographic al ly gated acquisition of five IVUS images per mm axial length during a stepwise transducer pull-back is an ideal approach, particularly wh en addressing with IVUS volumetric changes that are assumed small, suc h as those expected in studies of the progression and regression of at herosclerosis. (C) Rapid Science Publishers.