3D-printed micro-axicon enables extended depth-of-focus intravascular optical coherence tomography in vivo

A fundamental challenge in endoscopy is how to fabricate a small fiber-optic probe that can achieve comparable function to devices with large, complicated optics. To achieve high resolution over an extended depth of focus (DOF), the application of needle-like beams has been proposed. However, existing methods for miniaturized needle-beam designs fail to adequately correct astigmatism and other monochromatic aberrations, limiting the resolution of at least one axis. Here, we describe an approach to realize freeform beam-shaping endoscopic probes via two-photon polymerization three-dimensional (3D) printing. We present a design achieving <8 μm lateral resolution with a DOF of ∼800 μm. The probe has a diameter of <260 μm (without the torque coil and catheters) and is fabricated using a single printing step directly on the optical fiber. The probe was successfully utilized for intravascular imaging in living diabetic swine at multiple time points, as well as human atherosclerotic plaques ex vivo. To the best of our knowledge, this is the first report of a 3D-printed micro-optic for in vivo imaging of the coronary arteries. These results are a substantial step to enable the clinical adoption of both 3D-printed micro-optics and beam-tailoring devices.