Tapered fiber-based intravascular photoacoustic endoscopy for high-resolution and deep-penetration imaging of lipid-rich plaque.

High-resolution intravascular photoacoustic (IVPA) imaging can potentially improve the identification of atherosclerosis plaque. However, the absorption of water and the low coupled laser energy resulted in insufficient excitation energy provided by the single-mode fiber-based IVPA endoscope to achieve high-resolution and deep-penetration plaque imaging. In this paper, we developed a 1 mm diameter IVPA endoscope assembled with a Ø25-Ø9 μm tapered fiber. Owing to high coupling efficiency and the small output facula of tapered fiber, the IVPA endoscope has an optimal lateral resolution of 18 μm and a large imaging-depth covering from the intima to the peri-adventitial adipose, as confirmed by imaging results respectively. Furthermore, IVPA imaging in the blood has confirmed that the tapered fiber-based endoscope can display the distribution and the relative concentration of lipid in ex vivo plaque precisely. By the obtained histology-like images, IVPA imaging shows great potential for accurately imaging atherosclerosis plaque.