Volumetric intracoronary ultrasound: methods and validation

Intracoronary ultrasound (ICUS) not only allows visualization of the vessel lumen, it gives a unique view of the transmural components of the artery wall. Analysis of lumen and plaque volume is necessary for studying atherosclerotic disease progression or regression and the mechanisms of therapeutic coronary interventions. A real-time, ICUS pull-back data acquisition scheme was developed to acquire calibrated, cardiac-gated volumetric image data sets. A semiautomated border detection scheme was implemented using dynamic programming. In phantoms, estimated area profiles were very reproducible as measured by the root-mean-square from the mean (3.8-5.9%). In phantom volume estimates, improved reproducibility (standard deviation = 1.2-3.6%) was obtained as positive and negative errors in area profiles were averaged out. Phantom volumes were also accurate when compared to true water displacement volume. The mean error ranged from -2.59 to -8.94%. When compared to quantitative single and biplane angiographic analysis, ICUS volumetric estimates tended to be superior to single plane analysis (error -5.06 +/- 2.48% vs -9.96 +/- 8.01%), but similar to optimal biplane analysis (error -5.06 +/- 2.48% vs -6.34 +/- 3.08%). In vivo reproducibility was assessed by performing multiple cardiac-gated pull-backs through experimentally induced stenosis. Over the length of the stenosis, excellent reproducibility of area profiles (+/- 5.9%) and volumes (+/- 1.9%) was obtained for cardiac-gated acquisitions. We conclude that volumetric ICUS provides accurate and reproducible estimates of lumen volume. Thus this technique may be of use in clinical trials where changes lumen volumes and vessel area profiles are of interest.