Intravascular (IV) imaging in percutaneous coronary interventions can be invaluable to treat coronary artery disease, to facilitate decision making and to guide stent placement. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) are both established IV imaging modalities. However, achieving contrast for specific structures such as lipid plaques can be challenging; with OCT, visualisation is typically limited to tissue depths less than 2 mm. Photoacoustic (PA) imaging provides contrast that is complementary to those of IVUS and OCT, and with previous demonstrations, visualisation of lipid plaques at depths greater than 4 mm has been achieved. In this study, we developed an intravascular PA probe that comprises a commercial OCT catheter and a high sensitivity miniature fibre optic ultrasound sensor with a Fabry-Pérot cavity. This probe, which can provide both PA imaging and OCT, had a maximum width of 1.2 mm. The PA excitation sources included both pulsed and modulated lasers at different wavelengths. The omni-directionality of the US sensor allowed for three-dimensional PA images. The PA-OCT probe was characterised using a series of resolution phantoms, including fine carbon fibres. It was found that with PA imaging, the probe can provide a lateral resolution better than 25 µm and an axial resolution better than 100 µm at the optical focus. Co-registered PA and OCT images of blood vessels ex-vivo with stents and lipid injections were acquired. We conclude that PA imaging with OCT catheters is viable and that it has strong potential to guide clinical interventions.
Sunish J. Mathews, Callum Little, Chris D. Loder, Roby D. Rakhit, Wenfeng Xia, Edward Z. Zhang, Paul C. Beard, Malcolm C. Finlay, and Adrien E. Desjardins, "All-optical intravascular probe for dual-mode photoacoustic imaging and optical coherence tomography (Conference Presentation)," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 1049416 (Presented at SPIE BiOS: January 29, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2289631.5752209060001.
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