Photoacoustic Imaging of Atherosclerotic Plaques

Stroke is a major cause of death and disability worldwide. Stenotic carotid arteries can lead to stroke if the cause of the stenosis is a vulnerable atherosclerotic plaque. Recent studies reveal that if a patient has a plaque in the carotid artery it is highly probable that he/she will develop plaques in other superficial arteries like the femoral artery. Currently, duplex ultrasound is used to determine the grade of stenosis and is the main criterion for intervention (endarterectomy) planning. However, the stability, or instability of the plaque cannot be determined non-invasively. Photoacoustics is a novel, non-invasive imaging modality that uses pulsed laser light to generate laser induced ultrasound in the absorbing region of the tissue. Photoacoustic imaging provides optical contrast of biological tissue chromophores with an acoustic resolution and imaging depth, which is promising for visualization of plaque composition. The advantage of photoacoustics is the use of multiple wavelengths, since different tissues respond differently to different wavelengths. Hence, non-invasive, in vivo, morphology assessment is a future application of this new modality that would improve diagnosis and clinical decision making. The drawback is the limited penetration depth of the laser light and the signals generated by surrounding tissue. A new, integrated photoacoustic device has been developed that meets all safety requirements and has an improved penetration depth, suitable for imaging of carotid arteries with the aim to distinguish between plaques with different morphology.