Characterization of plaque components and vulnerability with intravascularultrasound elastography

Intravascular ultrasound elastography is a method for measuring the local e lastic properties using intravascular ultrasound (IVUS). The elastic proper ties of the different tissues within the atherosclerotic plaque are measure d through the strain. Knowledge of these elastic properties is useful for g uiding interventional procedures (balloon dilatation, ablation) and detecti on of the vulnerable plaque. In the last decade, several groups have applie d elastography intravascularly with various levels of success. In this pape r, the approaches of the different research groups will be discussed. The f ocus will be on our approach to the application of intravascular elastograp hy, Elastograms were acquired in vitro and in vivo using the relative local dis placements between IVUS images acquired at two levels of intravascular pres sure with a 30 MHz mechanical or a 20 MHz array echo catheter. These displa cements were estimated from the time shift between gated radiofrequency ech o signals using cross-correlation algorithms with interpolation around the peak. Experiments on gel-based phantoms mimicking atherosclerotic vessels demonst rated the capability of elastography to identify soft and hard tissues inde pendently of the echogenicity contrast. In vitro experiments on human arter ies have demonstrated the potential of intravascular elastography to identi fy different plaque types based on their mechanical properties. These plaqu es could not be identified using the IVUS image alone. In vivo experiments revealed that reproducible elastograms could be obtained near end-diastole. Partial validation using the echogram was performed. Intravascular elastography provides information that is frequently unavaila ble or inconclusive from the IVUS image and which may therefore assist in t he diagnosis and treatment of atherosclerotic disease.