Patent Application
20160070070
The present disclosure relates to optical coherence tomography (OCT), and in particular relates to an integrated torque assembly for OCT that uses an optical fiber cable, and related methods.
The entire disclosure of any publication or patent document mentioned herein is incorporated by reference, including U.S. Patent Application Publication No. 2013/0223787 and the article entitled “Optical coherence tomography,” by Huang, et al., Science 254, New Series, no. 5035 (Nov. 22, 1991): 1178-1181.
Optical coherence tomography (OCT) is used to capture a high-resolution cross-sectional image of scattering biological tissues using fiber-optic interferometry. The core of an OCT system is a Michelson interferometer, wherein a first optical fiber is used as a reference arm and a second optical fiber is used as a sample arm. The sample arm includes the sample to be analyzed as well as an optical probe that includes optical components. An upstream light source provides the imaging light, which has an OCT imaging wavelength. A photodetector is arranged in the optical path downstream of the sample and reference arms.
Optical interference of light the sample arm and the reference arm is detected by the photodetector only when the optical path difference between the two arms is within the coherence length of the light from the light source. Depth information from the sample is acquired by axially varying the optical-path length of the reference arm and detecting the interference between light from the reference arm and scattered light from the sample arm that originates from within the sample.
A three-dimensional image requires high-speed rotation as well as axial translation of the optical probe. This rotation and axial translation is carried out in conventional OCT systems through the use of a metal torque tube that is mechanically connected to the probe at a distal end, The torque tube is threaded through a guide tube, which is referred to in the art as an “inner lumen.” The torque tube is driven to rotate and axially translate at its proximal end by a rotary and axial translation actuator and transmits the rotational and axial translation motion to the optical probe at the distal end.
Conventional torque tubes are made of stainless steel and have a multi-coil spring assembly, which is a relatively complex design and does not offer very good dimensional control, Further, the torque tube must be feed into the inner lumen over long distances, which is difficult to do because of the flexibility of the spring coil. In addition, a large amount of surface-area contact can occur between the torque tube and the inner lumen. This surface-area contact is a source of friction that impacts the rotation and axial translation of the optical probe.
It is therefore desirable to simplify the mechanism used to impart rotation to the optical probe so that the OCT system is less expensive and easier to use while the potential contact area and frictional forces that can adversely impact performance are also reduced.
Integrated torque assemblies and methods for optical coherence tomography are disclosed. The integrated torque assembly includes an optical-fiber cable having an optical fiber surrounded by an outer jacket. An optical probe is operably attached to a distal end of the optical-fiber cable. The outer jacket has a main body with a plurality of outwardly extending protrusions. The optical-fiber cable and optical probe are optically disposed within an interior of a guide tube in a close-fit configuration to form the assembly. The protrusions serve to reduce the amount of surface area the optical fiber cable presents to an inner surface of the guide tube as compared to an optical fiber cable having a circular cross-section. This serves to reduce the amount of friction between the optical fiber cable and guide tube during rotation and translation of the optical fiber cable when OCT imaging is performed. The systems and methods disclosed herein can be used generally for OCT, e.g., for time-domain or frequency-domain OCT.
An aspect of the disclosure is an integrated torque assembly for use with a guide tube of an OCT system that utilizes a rotating optical probe. The assembly includes: a flexible guide tube having an inside surface that defines a guide tube inner diameter and a guide tube interior, with at least a portion of the guide tube being transparent to light at an OCT imaging wavelength; an optical fiber cable having an optical fiber surrounded by a jacket and having a length, the optical fiber cable having a proximal end and a distal end, wherein the jacket has a plurality of outwardly extending protrusions; an optical probe operably connected to the distal end of the optical fiber cable; and wherein the optical fiber cable and optical probe are operably disposed within the guide-tube interior in a close-fit configuration wherein the optical fiber cable can rotate and be axially translated within the interior of the flexible guide tube while the optical fiber cable only contacts the inner surface of the guide tube at the protrusions of the jacket.
Another aspect of the disclosure is an OCT assembly that includes the integrated torque assembly described immediately above, and a rotary and axial translation actuator operably attached to the proximal end of the optical fiber cable.
Another aspect of the disclosure is an integrated torque assembly for use with a guide tube of an OCT system that utilizes a rotating optical probe. The assembly includes: a flexible and transparent guide tube having an inside surface that defines a guide-tube inner diameter and a guide-tube interior; an optical fiber cable having an optical fiber having a proximal end and a distal end, and having a jacket that includes a main body and a plurality of protrusions that outwardly extend from the main body, with the protrusions and the inner surface of the guide tube defining a contact-area ratio RC 50%; an optical probe operably connected to the distal end of the optical fiber cable. The optical fiber cable and optical probe are operably disposed within the guide-tube interior in a close-fit configuration such that the optical fiber cable can rotate and be axially translated within the interior of the flexible guide tube.
Another aspect of the disclosure is an OCT assembly that includes the integrated torque assembly described immediately above, and a rotary and axial translation actuator operably attached to the proximal end of the optical fiber cable.
Another aspect of the disclosure is a method of rotating and axially translating an optical probe in an OCT system. The method includes: operably connecting an optical probe to a distal end of an optical fiber cable having a proximal end and an outer jacket with a main body and a plurality of outwardly extending protrusions each having an outermost portion; inserting the optical fiber cable and probe into an interior of a flexible guide tube having an inner surface to define a close-fit configuration between the optical fiber cable and the guide tube; and causing a rotation and an axial translation of the optical fiber cable at the proximal end so that the optical fiber cable and optical probe rotate and axially translate within the interior of the flexible guide tube while the optical fiber cable only contacts the inner surface of the guide tube at the outermost portions of the protrusions of the jacket.
Additional features and advantages are set forth in the Detailed Description that follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following Detailed Description are merely exemplary and are intended to provide an overview or framework to understand the nature and character of the claims.
The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the Detailed Description serve to explain principles and operation of the various embodiments. As such, the disclosure will become more fully understood from the following Detailed Description, taken in conjunction with the accompanying Figures, in which:
Reference is now made in detail to various embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same or like reference numbers and symbols are used throughout the drawings to refer to the same or like parts. The drawings are not necessarily to scale, and one skilled in the art will recognize where the drawings have been simplified to illustrate the key aspects of the disclosure.
The claims as set forth below are incorporated into and constitute a part of this Detailed Description.
The entire disclosure of any publication or patent document mentioned herein is incorporated by reference.
An end portion 22 of probe 20 is attached to an end portion 42 of torque tube 40. In an example, end portion 22 of probe 20 is made of metal, e.g., stainless steel. The torque tube 40 resides within a guide tube (or inner lumen) 50 and is free to rotate and axially translate therein, though there is typically some contact between the torque tube and the guide tube, i.e., there is a close-fit between the torque tube and the guide tube. The torque tube 40 has a constant diameter and thus represents a configuration that presents a maximum amount of surface area to guide tube 50, i.e., that can contact the guide tube.
The guide tube 50 is transparent to an OCT imaging wavelength of light 60 at least at probe-end portion 22. In an example, a (transparent) balloon (not shown) is used to create space for probe-end portion 22 within tissue or vessel 70. The probe-end portion 22 of OCT system 10 is inserted into a catheter or endoscope (not shown) for insertion into the body to be examined.
The light 60 originates from a light source (not shown) and travels down optical fiber 30 to end 32. This light 60 exits end 32 of optical fiber 30 and is directed by probe 20 to the surrounding tissue or vessel 70. The light 60 generates scattered light 60S from tissue or vessel 70, and some of this scattered light returns to and is captured by probe 20 and directed back to optical fiber end 32. The returned scattered light 60S travels back down optical fiber 30 toward the light source and is then interferometrically processed to generate the OCT image at the OCT imaging wavelength according to methods known in the art.
As noted above, this configuration based on the use of torque tube 40 and guide tube 50 is relatively complicated and produces frictional forces between the torque tube and the guide tube that adversely affect the operation of OCT system 10.
The cable 110 includes a proximal end 116 that is operably connected to a rotary and axial translation actuator (“actuator”) 160 and a distal end 118 that is operably connected to back-end portion 22 of probe 20.
In an example, jacket 114 can be considered as including a main body 121 and a plurality of protrusions 122 that outwardly extend from the main body. In an example, protrusions 122 outwardly (e.g., radially) extend with respect to jacket central axis AJ. In examples of jacket 114, protrusions 122 are rounded. In other examples of jacket 114, protrusions 122 have partial circular cross-sections. In the example of jacket 114 as shown in
In an example, jacket 114 includes an integer number N of protrusions 122, wherein in one example 3≦N≦10, while in another example 4≦N≦8. In an example, protrusions 122 run the entire axial length of cable 110.
An example jacket 114, such as shown in
The cable 110 has a maximum lateral dimension DC similar to the diameter of a cable having a circular cross-section (see
The cable 110 can be formed using processes that are known in the art. In particular, cable 110 can be formed using a manufacturing operation that simultaneously forms optical fiber 112 and jacket 114, i.e., a drawing operation that forms the optical fiber and a coating operation that forms the jacket on the optical fiber. In an example, jacket 114 is formed from a single dielectric material. In an example embodiment, the formation of jacket 114 includes an extrusion process that employs an extrusion die having the desired cross-sectional shape. In an example, the extrusion process takes into account changes in the shape and size of jacket 114 after extrusion, e.g., contraction due to cooling of the jacket material.
As noted above, guide tube 50 has inner surface 52, which defines interior 54 as having a generally circular cross-section and inner diameter DG. The cable diameter DC, as defined by the one or more protrusions 122, is slightly smaller than inner diameter DG of guide tube 50 so that cable 110 defines a close fit within interior 54 of the guide tube. The combination of guide tube 50 and cable 110 operably disposed within guide tube interior 54 defines integrated torque assembly 150.
The clearance CL=(DG−DC) of cable 110 within guide tube 50 (see
Thus, in the close-fit configuration, cable 110 is loosely arranged within interior 54 of guide tube 50 with only protrusions 122 being able to come into contact with inner surface 52 of the guide tube. The amount of area presented by protrusions 122 to inner surface 52 of guide tube 50 is substantially less than for the prior-art torque tube 40 discussed above, which has circular cross-sectional shape. Thus, protrusions 122 can be thought of as stand-off features that prevent the entire outer surface 120 of jacket 114 from being able to make contact with inner surface 52 of guide tube 50. This configuration serves to reduce the amount of friction that can occur between cable 110 and guide tube 50 during rotation and axial translation of the cable during an OCT procedure.
In an example, the outermost portions of protrusions 122 are rounded. In an example, protrusions 122 are configured to allow for only a relatively small portion of outer surface 120 of jacket 114 to contact inner surface 52 of guide tube 50. Another way to state this condition is that a relatively small area defined by inner surface 52 of guide tube 50 is subject to contact by jacket 114. This is best illustrated in the front-on view of integrated torque assembly 150 of
The total protrusion contact area AT for the example integrated torque assembly 150 of
The amount of total protrusion contact area AT will depend on a number of factors, such as the number of protrusions 122, the size of the protrusions, the hardness of the material making up jacket 114, the hardness of guide tube 50, the amount of force with which cable 110 contacts inner surface 52 of the guide tube, etc. In various examples of integrated torque assembly 150, the contact-area ratio RC≦50%, or RC≦25%, or RC≦20%, or RC≦10%, or RC≦5%, or RC≦2% or RC≦1%.
Random manufacturing variations in guide tube 50 and cable 110 can cause an increase in the frictional forces or an increase in the lashing of the cable within the guide tube. These variations can lead to non-uniform rotation of probe 20 and can put stress on the various components. This stress can lead to a failure of OCT system 100, e.g., probe 20 becoming disconnected from cable 110. Thus, in an example, the clearance CL=(DG−DC) is in the range from 100 μm to 150 μm to define the close-fit configuration and to reduce or minimize the adverse effects of the random manufacturing variations.
In an example, guide tube 50 can be formed using an extrusion or a drawing process. The extrusion process provides good dimensional control, thereby reducing the potential adverse effects of the aforementioned random manufacturing errors.
In an example embodiment, one or more components of OCT system 100 can include a low-friction coating.
Example low-friction materials include polytetrafluorotethylene, polyimide, polyamide, polyethylene, polysilicone, fluorosilane, fluoroether silanes, silicones, etc. In an example, jacket outer surface 120 (or low-friction coating 126 thereon) has a coefficient of static friction μS<0.5, while in another example, μS<0.1, while yet in another example, μS<0.05. In an example, low-friction coating 126 is defined as having a static coefficient of friction that is less than that of the surface to which the coating is applied.
The low-friction coating 126 can be made from any of the known low-friction materials and can be spray coated, spin coated, dipped coated, etc. In one example, a TEFLON-based low-friction coating 126 was prepared using 1% TEFLON AF in a fluoroether solvent FC-40 and combined with a solution of adhesion binder (1 wt % in HFE7200) to produce a solution that was 1 wt % total in polymer mass. The solution was filtered through a coarse paper filter prior to use. An example of using an adhesion binder and the preparation details for non-stick coating materials are described in U.S. Patent Application Publication No. 2012/0189843.
In another example, low-friction coating 126 can be made from heptadecafluoro-tetrahyd rodecyl-trichlorosilane (C10H4F17Si Cl3) by combining perfluorosilane with anhydrous heptane. The metal surfaces can then be cleaned and then immersed in the coating solution for 1 minute. Upon removal, the coated metal surfaces can be rinsed with heptane and then ethanol.
In an example, low-friction coating 126 includes one or more low-friction enhancements, such as low-friction particles and/or additives. The particles and/or additives can also be added to inner surface 52 of guide tube 50 and/or jacket 114 of cable 110 during their fabrication.
An aspect of the disclosure is a method of performing OCT by rotating and axially translating optical probe 20 in OCT system 100. The method includes providing cable 110, with optical probe 20 being operably connected to the cable at distal end 118. The cable 110 has a cross-sectional shape that includes a plurality of protrusions 122 that outwardly extend from main body 121. The protrusions 122 are configured to reduce the contact-area ratio RC as compared to a cable 110 having a circular cross-section.
The cable 110 and probe 20 are then inserted into interior 54 of flexible guide tube 50 in a close-fitting configuration to define integrated torque assembly 150. The method further includes causing a rotation and an axial translation of cable 110 at its proximal end 116, e.g., by activating actuator 160 operably connected thereto. This causes the rotation and axial translation of cable 110 and optical probe 20 attached thereto within interior 54 of flexible guide tube 50. The cable 110 transfers the torque and axial translation generated by actuator 160 at proximal end 116 of cable 110 to distal end 118, thereby causing the rotation and axial translation of optical probe 20. Only the outermost portions of protrusions 122 make contact with inner surface 52 of guide tube 50 during the rotation and axial translation of cable 110 and the transfer of the torque from cable proximal end 116 to cable distal end 118 and probe 20. In examples of the method, one or more low-friction coatings 126 are employed on at least one of: inner surface 52 of guide tube 50 and protrusions 122 of cable 110.
It will be apparent to those skilled in the art that various modifications to the preferred embodiments of the disclosure as described herein can be made without departing from the spirit or scope of the disclosure as defined in the appended claims. Thus, the disclosure covers the modifications and variations provided they come within the scope of the appended claims and the equivalents thereto.
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 62/047,947 filed on Sep. 9, 2014, the content of which is relied upon and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62047947 | Sep 2014 | US |
