Atherosclerotic plaque characterization with optoacoustic imaging

The developing realization that acute coronary events, such as myocardial infarctions, can be caused by the sudden disruption of relatively small, rupture-prone plaques has led to increased exploration of clinical techniques that identify "vulnerable plaque" and differentiate it from "stable" plaque. Intravascular optoacoustic imaging promises to be such a technique. It has the capability of measuring the thickness of the plaque cap, the size of the underlying lipid reservoir, and other structural features known to be related to the vulnerability of the plaque. Inside an artery, optoacoustic imaging must necessarily be done in the backward mode, with irradiation and detection close to the same site on the tissue surface. With test phantoms simulating the optical and acoustic properties of the arterial wall, we have been able to show that backward-mode imaging is feasible. Modification of the ultrasonic detector used to allow irradiation and detection at the same point on the same surface affects the signal in a predictable way. The effect of the probe on the signal can reliably be removed by deconvolution of the measured signal to take into account the detector response.