Intracranial blood vessel OCT imaging catheter based on 3D printing superlens

Abstract

The application discloses an intracranial blood vessel OCT imaging catheter based on a 3D printing superlens, and belongs to the technical field of medical devices and optical imaging technology. The catheter comprises an outer wall encapsulation sleeve, a single-mode optical fiber and an optical structure integrated on the distal end face of the single-mode optical fiber and directly constructed by using an additive manufacturing process. The optical structure is a 3D printed optical structure or a superlens structure, which is configured to realize spatial focusing of a light beam and deflection of a propagation direction, so that the outgoing light beam is laterally emitted from the catheter side wall area at a preset inclination angle and aberration caused by the catheter polymer material and the internal lubricating medium is compensated. The multifunctional optical element is directly integrated on the optical fiber end, so that compact and integrated optical path design is realized, high-precision focusing, controllable lateral emission and multi-medium interface aberration robust compensation are simultaneously realized under the constraint of a catheter outer diameter of ≤0.7 mm, and the intracranial distal blood vessel OCT imaging quality and clinical applicability are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of medical device and optical imaging technology, specifically relating to an intracranial vascular OCT imaging catheter based on a 3D-printed superlens. Background Technology

[0002] With the increasing precision of neurointerventions, there is an urgent need for high-resolution imaging of small intracranial vessels (<2mm in diameter). OCT, with its micron-level resolution, has become an important tool for assessing the microstructure of vessel walls. However, its imaging catheter core + distal optical structure + traditional methods suffer from low mechanical rotation reliability and difficulties in lens assembly. In recent years, direct fabrication of micro-optical structures and superlenses at fiber optic endfaces have provided new ideas for miniaturization design. However, intracranial applications require traversing tortuous paths, and the spherical aberration and coma introduced by multi-media interfaces (blood, vessel wall, lubricating fluid) significantly affect image quality. Existing correction methods struggle to balance miniaturization and robustness.

[0003] Existing intracranial vascular OCT imaging catheters still have several key technical deficiencies in terms of optical design and clinical adaptability. It is difficult to simultaneously achieve high-precision focusing, controllable lateral emission, wide-band low-loss transmission, and robust compensation for multi-media interface aberrations while ensuring that the outer diameter of the catheter is ≤0.7 mm. This seriously restricts the clinical applicability and image diagnostic value of OCT in minimally invasive interventional diagnosis and treatment of distal intracranial vessels. Summary of the Invention

[0004] This invention provides an intracranial vascular OCT imaging catheter based on a 3D-printed superlens, comprising an outer encapsulation sleeve for confining and protecting the internal optical fiber and optical structure, a single-mode optical fiber, and an optical structure integrated into its distal end face. The single-mode optical fiber transmits the near-infrared broadband light beam output by the OCT system and outputs diverging light at its distal end. The optical structure, integrated into the distal end face of the single-mode optical fiber, is directly constructed on the fiber end face using an additive manufacturing process; the optical structure is a 3D-printed optical structure or a superlens structure.

[0005] The optical structure is configured to receive diverging light from a single-mode optical fiber and achieve spatial focusing and deflection of the beam's propagation direction through its geometry or subwavelength structure, so that the emitted beam is laterally emitted from the catheter sidewall region at a preset tilt angle, and the focal point is located at a set working distance near the central axis of the blood vessel lumen.

[0006] The optical structure is also used to compensate for spherical aberration, coma, and refractive shift caused by the polymer material of the conduit and the transparent lubricating medium filling it.

[0007] When the OCT beam is transmitted to the far end via a single-mode fiber, the optical structure first completes the beam shaping, focusing and lateral deflection. Then, it penetrates the sidewall of the catheter and enters the tissue inside the blood vessel. The reflected signal returns along the original optical path and is captured by the detection system, thus forming a high-resolution cross-sectional image.

[0008] Optionally, the 3D-printed optical structure adopts a dual-region composite design: the near-end region is a rotationally symmetric aspherical lens, the surface profile of which is determined by a polynomial equation.

[0009] Defined as follows: z is the surface profile function, r is the surface radius, c is the curvature, k is the conic coefficient, and A4 and A6 are higher-order aspherical coefficients, used to focus the diverging light output from the single-mode fiber to the central focal point; the far-end region is provided with an inclined refractive surface, used to deflect the focused beam to the side and emit it at an angle of 84°-96° with the axis of the guide tube.

[0010] Optionally, the tilt angle of the tilted refractive surface is 42°-48°. This structure enables the beam to be laterally focused within a working distance of 0.5mm-2mm, and the lateral emission angle is adapted to the diameter range of intracranial blood vessels, ensuring that the imaging field of view covers the entire circumferential area of ​​the vessel wall.

[0011] Optionally, the material of the 3D printed optical structure is a high-transparency photosensitive resin with a refractive index controlled in the range of 1.52-1.58, forming a gradual refractive index transition between the single-mode fiber end face and the conduit shell material, reducing Fresnel reflection loss between multi-layer interfaces. The outer surface of the 3D printed optical structure is coated with an anti-reflection coating with a thickness of 100nm-300nm.

[0012] Optionally, the optical structure is a superlens structure, which is composed of a subwavelength scale nanopillar array. The nanopillar units are arranged in a hexagonal periodic pattern. Each nanopillar has a height of 800nm-1200nm and a diameter of 200nm-400nm. The size parameters are adjusted by changing the radial position to achieve spatially varying phase delay, thereby constructing a wavefront modulation capability that conforms to the generalized Snell's law.

[0013] Optionally, the superlens structure is used to accurately correct systematic aberrations caused by the duct wall thickness of 0.08mm-0.15mm and the refractive index of the lubricating medium of 1.38-1.42, with the point spread function half-width at half-maximum kept below 10μm, significantly improving the consistency of axial and lateral resolution.

[0014] Optionally, the sidewall of the conduit corresponding to the beam emission area is provided with a local thinning structure with a thickness of 0.05mm-0.08mm, and this area is made of polyether block amide material with low birefringence performance to reduce polarization distortion and optical path difference at the emission window. The local thinning structure is combined with the pre-compensation design of the optical structure to jointly suppress the aberration superposition effect caused by material anisotropy and interface bending, and ensure that the imaging quality remains uniform and stable at different azimuth angles.

[0015] Optionally, the single-mode fiber and the optical structure are precisely coupled at the submicron level through an ultraviolet curing alignment process: the fiber end face is precisely cut and placed on a three-dimensional micro-nano printing platform, and the optical structure is constructed layer by layer using femtosecond laser two-photon polymerization technology. During the construction process, the light spot morphology is monitored in real time to adjust the printing path, ensuring that the final optical structure and the fiber mode field achieve optimal matching, improving the optical coupling efficiency to over 90%, reducing power loss and heat accumulation, and ensuring the safety of long-term in vivo operation.

[0016] Optionally, the superlens structure can be used in combination with the local thinning structure, or the superlens structure can be used in combination with the anti-reflective coating, to further improve imaging stability and light energy utilization efficiency under complex physiological environments.

[0017] Optionally, the OCT imaging guide is used in the preparation of an intracranial vascular optical coherence tomography (OCT) imaging device.

[0018] The present invention has the following beneficial effects: (1) By directly integrating 3D printed optical structures or superlenses onto the far end face of a single-mode fiber and using additive manufacturing process to form an integrated structure, while achieving efficient beam focusing and lateral emission, the problems of large size, difficult alignment and poor mechanical reliability caused by the assembly of traditional discrete optical components are fundamentally solved, so that the outer diameter of the catheter can be controlled below 0.7mm, meeting the needs of intracranial small blood vessel intervention.

[0019] (2) By utilizing the optical structure to precisely control the beam wavefront, the spherical aberration, coma, and optical path offset introduced by the multi-layer refractive index mismatch interface of the catheter polymer material and internal lubricating medium are pre-compensated, so that the point spread function half width at half maximum is kept below 10 μm, significantly improving the imaging resolution and focus positioning accuracy, and realizing high-definition and high-stability intravascular OCT imaging. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the OCT imaging catheter structure described in Embodiment 1 of the present invention.

[0022] Figure 2 This is a schematic diagram of the OCT imaging catheter structure with an anti-reflection coating as described in Embodiment 2 of the present invention.

[0023] Figure 3 This is a schematic diagram of the OCT imaging catheter structure based on a superlens as described in Embodiment 3 of the present invention.

[0024] Figure 4 This is a schematic diagram of the sidewall of the catheter with a localized thinning structure as described in Embodiment 4 of the present invention.

[0025] Reference numerals: 101, single-mode optical fiber; 102, 3D printed optical structure; 102a, aspherical lens; 102b, reflecting surface; 201, anti-reflection coating; 301, superlens; 401, locally thinned structure. Detailed Implementation

[0026] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed merely to enable those skilled in the art to better understand and implement the subject matter described herein, and are not intended to limit the scope, applicability, or examples set forth in the claims. The function and arrangement of the elements discussed may be changed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the various examples. For example, the described methods may be performed in a different order than described, and steps may be added, omitted, or combined. Furthermore, features described in some examples may be combined in other examples.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0028] Example 1 See Figure 1This embodiment provides a catheter for optical coherence tomography (OCT) imaging within intracranial blood vessels. The OCT imaging catheter includes: an outer sheath for confining and protecting the internal optical fiber and optical structure; a single-mode fiber 101 for transmitting a near-infrared broadband light beam output from the OCT system with a center wavelength of approximately 1310 nm, and outputting divergent light with a divergence angle of ±6° at its distal end; and a 3D-printed optical structure 102, constructed layer by layer directly on the distal end face of the single-mode fiber 101 using a femtosecond laser two-photon polymerization additive manufacturing process, forming an integrated micro-composite lens structure.

[0029] The 3D-printed optical structure 102 includes two functional regions: the near-end region is a rotationally symmetric aspherical lens 102a, the surface profile of which is determined by a polynomial equation.

[0030] Defined as follows: z is the surface profile function, r is the surface radius, c is the curvature, k is the conic coefficient, and A4 and A6 are higher-order aspherical coefficients used to focus the diverging light to the central focal point; a reflective surface 102b with an inclination angle of 42°-48° is provided in the far-end region. This reflective surface causes the focused beam to be reflected and finally emitted laterally from the sidewall region of the duct at an angle of 84°-96°, thereby achieving ring scanning without rotating the probe.

[0031] The focal point of the emitted light beam is located at a working distance of 0.8mm-1.6mm from the outer wall of the catheter, which is suitable for typical intracranial blood vessel diameters of 2-4mm, ensuring that the imaging field of view covers the entire circumferential area of ​​the vessel wall. The 3D printed optical structure 102 is made of high-transparency photosensitive resin IP-Dip, which has a refractive index of 1.55 and a transmittance of more than 90% in the visible to near-infrared band.

[0032] When the OCT beam is transmitted to the far end via the single-mode optical fiber 101, the beam is first shaped and deflected by the 3D-printed optical structure 102. Then, it penetrates the sidewall of the catheter and enters the tissue inside the blood vessel. The reflected signal returns along the original optical path and is captured by the detection system, thereby forming a high-resolution cross-sectional image.

[0033] The feasibility of achieving lateral emission and focusing through an integrated 3D-printed optical structure at the far end of the fiber optic cable was verified. Stable focusing within a working distance of 0.8-1.6 mm was achieved under an outer diameter constraint of 0.7 mm, and the circumferential imaging area of ​​the blood vessel wall could be covered without the need for a rotating mechanism.

[0034] Example 2 See Figure 2This embodiment provides an intracranial vascular OCT imaging catheter based on a 3D-printed superlens, further optimizing the light energy utilization and anti-reflection performance of the optical interface based on Embodiment 1. The outer surface of the 3D-printed optical structure 102 is coated with a 200nm thick anti-reflection coating 201, which consists of alternating deposited silicon dioxide (SiO2) and niobium pentoxide (Nb2O5) nanofilms, with a total of 8 layers. The thickness of each layer is optimized according to the target wavelength of 1310nm and the incident angle to achieve a wide-angle, wide-bandwidth anti-reflection effect, further reducing the scattering loss of light energy during transmission and improving the effective illumination intensity and signal-to-noise ratio.

[0035] The anti-reflective coating 201 can reduce Fresnel reflection loss between multi-layer interfaces to below 1.5%, increasing the effective illumination intensity by approximately 40% compared to the uncoated state. Furthermore, the refractive index 1.55 of the 3D-printed optical structure 102 is between the 1.46 refractive index of the single-mode fiber quartz core layer and the 1.48 refractive index of the conduit shell polyether block amide (PEBA), forming a gradient refractive index transition, further suppressing interface reflection and scattering.

[0036] The single-mode optical fiber 101 and the 3D-printed optical structure 102 are precisely coupled at the sub-micron level through a UV curing alignment process. On a 3D micro-nano printing platform, the fiber end face is precisely cut and fixed to a six-degree-of-freedom adjustable fixture. A confocal microscope system is used to monitor the spot morphology in real time and adjust the printing path accordingly, ensuring that the final lens structure achieves optimal matching with the fiber mode field diameter of 9μm. This coupling method achieves an optical coupling efficiency of 92%, significantly reducing power loss and thermal accumulation, and ensuring safety during long-term in-vivo operation.

[0037] The anti-reflective coating reduces Fresnel reflection loss to below 1.5% and increases effective illumination intensity by approximately 40%; UV curing alignment and real-time spot feedback technology achieve a coupling efficiency of 92%, reduce thermal effects, and ensure safety during long-term in vivo operations.

[0038] Example 3 See Figure 3 This embodiment proposes an OCT imaging conduit based on a superlens as a performance upgrade solution for traditional 3D-printed lenses. The superlens 301 replaces the 3D-printed optical structure 102 in Embodiment 1 and is still integrated into the distal end face of the single-mode fiber 101. It is directly printed using femtosecond laser two-photon polymerization technology to form a subwavelength-scale STO nanopillar array.

[0039] The nanopillars are arranged in a hexagonal periodic pattern with a lattice constant of 350 nm. Each nanopillar has a uniform height of 1000 nm, and its diameter varies continuously in the radial direction from 250 nm to 380 nm to modulate the local phase delay distribution. By designing the geometric parameters of each nanopillar to support a specific resonance mode, a linear phase gradient conforming to the generalized Snell's law is constructed in the xy plane, achieving precise modulation of the incident light wavefront.

[0040] The superlens 301 not only possesses a focusing function with a numerical aperture (NA) of 0.35, but also simultaneously introduces lateral momentum shift, causing the emitted beam to be emitted laterally at a 90° angle perpendicular to the catheter axis, and stabilizing the focal point at 1.5 mm from the outer wall of the catheter. More importantly, the superlens 301 is pre-programmed to compensate for spherical aberration and coma caused by the 0.12 mm thick catheter wall and the 1.40 refractive index of the transparent lubricating medium filling the interior. Simulation and experimental verification show that, in the presence of multilayer media, the point spread function (PSF) maintains a full width at half maximum (FWHM) within 9.8 μm, and the lateral resolution consistency is improved by more than 35%, significantly enhancing imaging clarity and diagnostic reliability.

[0041] The superlens structure integrates focusing and deflection, and accurately compensates for aberrations at the interface of multiple media, keeping the PSF half-width within 9.8μm and improving lateral resolution consistency by more than 35%.

[0042] Example 4 See Figure 4 This embodiment optimizes the structure to address the optical distortion problem of the duct exit window. The duct sidewall corresponding to the beam exit area has a local thinning structure 401 with a thickness controlled at 0.06 mm, which is 50% thinner than the remaining 0.12 mm, in order to shorten the optical path of the beam through the duct wall and reduce material absorption and dispersion effects.

[0043] The locally thinned structure 401 is made of polyether block amide 70D material with low birefringence, and its stress-induced birefringence coefficient is less than 5 × 10⁻⁶. -5 This effectively suppresses polarization distortion. Furthermore, the region is elliptical in shape, with its major axis extending circumferentially along the guide tube, and measures 1.0mm × 0.6mm, ensuring a complete and unobstructed beam exit cross-section.

[0044] The design of the 3D-printed optical structure 102 pre-compensates for the aberration superposition effect caused by the mismatch between the interface curvature and refractive index in the window area. The synergistic effect of these two factors results in imaging resolution fluctuations of less than 5% at different azimuth angles, significantly improving image uniformity. This design is particularly suitable for continuous imaging of curved blood vessel segments, avoiding local blurring caused by changes in probe orientation.

[0045] The localized thinning structure of 0.06mm, combined with polyether block amide (PEBA) low birefringence material and pre-compensation design, ensures that the imaging resolution fluctuation is less than 5% under different azimuth angles, effectively solving the local blurring problem in the imaging of tortuous blood vessel segments.

[0046] Example 5 The technical features in the above embodiments can be combined arbitrarily without conflict. For example, the superlens 301 in Embodiment 3 can be combined with the local thinning structure 401 in Embodiment 4 to further improve imaging stability under complex physiological environments; or the anti-reflective coating 201 in Embodiment 2 can be added to Embodiment 3 to maximize light energy utilization efficiency. All combinations are within the protection scope of this invention.

[0047] The OCT imaging catheter of the present invention can be used to prepare intracranial vascular optical coherence tomography imaging equipment, and can also be extended to clinical scenarios requiring miniaturized OCT imaging catheters, such as coronary arteries, peripheral blood vessels, and the digestive tract.

[0048] By directly integrating multifunctional optical elements into the end of the optical fiber, this invention achieves a compact and integrated optical path design. Structurally, it avoids the problems of large size and difficult alignment caused by traditional prism or lens assembly, significantly improving the miniaturization and mechanical stability of the catheter. At the same time, through a pre-designed aberration compensation mechanism, it effectively suppresses focus drift and resolution reduction caused by refractive index mismatch at the interface of multiple transparent media, improving imaging clarity and diagnostic reliability.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A 3D-printed superlens-based intracranial vascular OCT imaging catheter, characterized in that, include: The outer wall encapsulation sleeve is used to confine and protect the internal optical fibers and optical structures within them; Single-mode optical fiber is used to transmit the near-infrared broadband light source beam output by the OCT system and output divergent light at its far end. The optical structure is integrated into the far end face of the single-mode optical fiber and is constructed directly on the end face of the optical fiber using an additive manufacturing process. The optical structure is configured to receive the diverging light from the single-mode optical fiber and achieve spatial focusing and deflection of the beam's propagation direction through its geometry or subwavelength structure, so that the emitted beam is laterally emitted from the catheter sidewall region at a preset tilt angle, and the focal point is located at a set working distance near the central axis of the vascular lumen. The optical structure is also used to compensate for spherical aberration, coma, and refractive shift caused by the polymer material of the conduit and the transparent lubricating medium filling it.

2. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 1, characterized in that, The optical structure is a 3D-printed optical structure, employing a dual-region composite design: the near-end region is a rotationally symmetric aspherical lens, whose surface profile is derived from a polynomial equation. Defined as follows: z is the surface profile function, r is the surface radius, c is the curvature, k is the conic coefficient, and A4 and A6 are higher-order aspherical coefficients. A4 and A6 are higher-order aspherical coefficients used to focus the diverging light output from a single-mode fiber to the central focal point. The distal region is equipped with an inclined reflective surface to deflect the focused beam to the side and emit it at an angle of 84°-96° with the duct axis.

3. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 2, characterized in that, The tilt angle of the tilted reflector is 42°-48°. This structure enables the beam to be laterally focused within a working distance of 0.5mm-2mm, and the lateral emission angle is adapted to the diameter range of intracranial blood vessels, so that the imaging field of view covers the entire circumferential area of ​​the vessel wall.

4. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 2, characterized in that, The material of the 3D printed optical structure is a high-transparency photosensitive resin with a refractive index controlled in the range of 1.52-1.58; the outer surface of the 3D printed optical structure is coated with an anti-reflective coating with a thickness of 100nm-300nm.

5. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 4, characterized in that, The optical structure is a superlens structure, which is composed of a subwavelength scale nanopillar array. The nanopillar units are arranged in a hexagonal periodic pattern. Each nanopillar has a height of 800nm-1200nm and a diameter of 200nm-400nm. The size parameters are adjusted by changing the radial position to achieve spatially varying phase delay, thereby constructing a wavefront modulation capability that conforms to the generalized Snell's law.

6. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 5, characterized in that, The superlens structure is used to accurately correct systematic aberrations caused by the duct wall thickness of 0.08mm-0.15mm and the refractive index of the lubricating medium of 1.38-1.42, with the point spread function half-width maintained below 10μm.

7. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 6, characterized in that, The sidewall of the conduit has a local thinning structure corresponding to the beam emission area, with a thickness of 0.05mm-0.08mm. This area is made of polyether block amide material with low birefringence performance to reduce polarization distortion and optical path difference at the emission window. The combination of the localized thinning structure and the pre-compensation design of the optical structure jointly suppresses the aberration superposition effect caused by material anisotropy and interface curvature.

8. The intracranial vascular OCT imaging catheter based on a 3D-printed superlens according to claim 7, characterized in that, The superlens structure is used in combination with the local thinning structure, or the superlens structure is used in combination with the anti-reflective coating.

9. A 3D-printed superlens-based intracranial vascular OCT imaging catheter according to any one of claims 1-8, characterized in that, The single-mode optical fiber and the optical structure are precisely coupled at the submicron level through an ultraviolet curing alignment process. After the fiber end face is precisely cut, it is placed on a three-dimensional micro-nano printing platform. The optical structure is built layer by layer using femtosecond laser two-photon polymerization technology, and the printing path is adjusted in real time by monitoring the spot shape feedback during the construction process.

10. A 3D-printed superlens-based intracranial vascular OCT imaging catheter according to any one of claims 1-8, characterized in that, Application in the preparation of intracranial vascular optical coherence tomography equipment.

Images