WO2019140152A1

WO2019140152A1 - System and apparatus for forward-view imaging

Info

Publication number: WO2019140152A1
Application number: PCT/US2019/013141
Authority: WO
Inventors: Guillermo J. Tearney; Adel ZEIDAN
Original assignee: The General Hospital Corporation
Priority date: 2018-01-11
Filing date: 2019-01-11
Publication date: 2019-07-18

Abstract

An imaging apparatus includes an illumination probe and a detector. The detector includes a plurality of light collectors. Each of the plurality of light collectors extends from a proximal end to a distal end and has a longitudinal axis. At least one of the light collectors has the distal end formed with an acute angle with respect to the longitudinal axis. The distal ends of the plurality of light collectors at least partially surround the illumination probe and the proximal ends of the plurality of light collectors form a linear array.

Description

SYSTEM AND APPARATUS FOR FORWARD-VIEW IMAGING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on, claims priority to, and incorporates herein by reference in their entirety U.S. Serial No. 62/769,046 filed November 19, 2018, and entitled "Megapixel Forward- Viewing Spectrally Encoded Probe," and U.S. Serial No. 62/616,081 filed January 11, 2018, and entitled "System, Method and Computer Accessible Medium For

Fabrication of Miniature Endoscope For Forward- View Imaging."

BACKGROUND

[0002] The present disclosure relates generally to a system and apparatus for endoscopy and more particularly to spectrally encoded endoscopy probes for obtaining information in a forward direction.

[0003] Medical probes have the ability to provide images from inside the patient's body.

Considering the potential damage to the human body caused by the insertion of a foreign object, it is preferable for the probe to be as small as possible. Additionally, the ability to image within small pathways such as small vessels, small ducts, small needles, cracks, etc. requires a small probe size. Traditional endoscopy procedures have limited access to narrow anatomical structures in various organs of the human body.

[0004] One type of medical probe employs spectrally encoded endoscopy ("SEE"), which is a miniature endoscopy technology that can conduct high-definition imaging through a sub-mm diameter probe. With SEE, broadband light is diffracted by a grating at the tip of the fiber, producing a dispersed spectrum on the sample. Light returned from the sample is detected using a spectrometer; and each resolvable wavelength corresponds to reflectance from a different point on the sample. The principle of the SEE technique and an SEE probe with a diameter of 0.5 mm, i.e., 500 pm have been described in D. Yelin et al., Nature Vol. 443, 765-765 (2006). SEE can produce high-quality images in two- and three- dimensions.

[0005] A SEE probe may be designed with large side-viewing angles that images, for example, the walls adjacent to the SEE probe. However, the side-viewing angles limit the use of the probe for any application that requires navigation through confined cavities because the area in front of the probe is not imaged. One of the technical challenges for fabricating SEE probes has been to conduct forward-view SEE imaging (also called front-view SEE imaging). Forward view SEE imaging is preferable for many applications and provides a look ahead that can facilitate navigation and surveillance of a wider field of view. Forward view SEE imaging is particularly advantageous for applications such as orthopedics, ear, eye and sinuses (EENT), laparoscopy, and pediatric surgery.

[0006] Therefore, there is a need for improved systems and apparatus for forward-view

SEE imaging.

SUMMARY

[0007] In accordance with an embodiment, an imaging apparatus includes an

illumination probe and a detector. The detector includes a plurality of light collectors. Each of the plurality of light collectors extends from a proximal end to a distal end and has a longitudinal axis. At least one of the light collectors has the distal end formed with an acute angle with respect to the longitudinal axis. The distal ends of the plurality of light collectors at least partially surround the illumination probe and the proximal ends of the plurality of light collectors form a linear array.

[0008] In accordance another embodiment, an imaging system includes a light source, an illumination probe coupled to the light source, a rotary junction coupled to the illumination probe and configured to rotate the illumination probe, a detector and a processor coupled to the detector and configured to receive data from the detector and process the data to generate an image. The detector includes a plurality of light collectors. Each of the plurality of light collectors extends from a proximal end to a distal end and has a longitudinal axis. At least one of the light collectors has the distal end formed with an acute angle with respect to the longitudinal axis.

The distal ends of the plurality of light collectors at least partially surround the illumination probe and the proximal ends of the plurality of light collectors form a linear array.

[0009] The foregoing and other advantages of the present disclosure will appear from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. The patent or application file contains at least on drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request the payment of the necessary fee.

[0011] FIG. l is a diagram of a forward-view SEE imaging apparatus in accordance with an embodiment;

[0012] FIG. 2 is a diagram of an illumination probe for a forward— view SEE imaging apparatus in accordance with an embodiment;

[0013] FIG. 3 is a diagram of a detector for a forward-view SEE imaging apparatus in accordance with an embodiment;

[0014] FIGs. 4A-4E show end views of an illumination probe and detector in accordance with an embodiment;

[0015] FIG. 5 shows an end, cross-sectional view of a detector in accordance with an embodiment;

[0016] FIG. 6 shows a light collector of a detector in accordance with an embodiment;

[0017] FIG. 7 shows a resulting detection field of view using the light collector of FIG. 6 in accordance with an embodiment;

[0018] FIG. 8A is a diagram showing a cross-sectional view of a detector surrounding an illumination probe before a heat shrink process in accordance with an embodiment;

[0019] FIG. 8B is a diagram showing a cross-sectional view of a detector surrounding an illumination probe after a heat shrink process in accordance with an embodiment; and

[0020] FIG. 9 is a block diagram of a forward-view SEE imaging system in accordance with an embodiment.

DETAILED DESCRIPTION

[0021] FIG. l is a diagram of a forward-view SEE imaging apparatus in accordance with an embodiment. Imaging apparatus 100 includes an illumination probe 102 and a detector 110. The illumination probe 102 includes a lens 104, a spacer 106 and a grating 108. A first fiber 112 couples the illumination probe 102 to a rotary junction 114. A second fiber 115 couples the rotary junction 114 to a light source 116. The first fiber 112 and the second fiber 115 may be, for example, a single-mode fiber, a multi-mode fiber or a double-clad fiber. In an embodiment, light source 116 is a broadband light source that may provide light radiation that is a mixture of various wavelengths that is generally in the visible spectrum, and may also extend to the UV or IR, as well as into other ranges. In one embodiment, the range of wavelengths is from, for example, 420 nm to 820 nm. In other embodiments, multiple radiation bands may be provided in one or more fibers to provide color SEE. The broadband light (or other electromagnetic radiation) from the light source 116 is provided into the second fiber 115 and goes through the rotary junction 114 to the first fiber 112. The light then travels to the illumination probe 102 via the first fiber 112.

[0022] FIG. 2 is a diagram of an illumination probe for a forward-view SEE imaging apparatus in accordance with an embodiment. Light, after exiting the rotary junction 114, is sent through the first fiber 112. The light then enters the lens 104 of the illumination probe 102. The lens 104 may be, for example, a gradient index (GRIN) lens. The illumination probe 102 or a portion of the illumination probe 102 (e.g., the lens 104 or spacer 106) may be rotated by the rotary junction 114. The rotary junction 114 may include, for example a DC motor (not shown) and the apparatus may also include a drive coil shaft (not shown) to drive the rotation of the illumination probe 102. In an embodiment, the illumination probe 102 is rotated while the detector 110 (shown in FIG. 1) is stationary. The light then passes through a spacer 106 which has a grating 108 located on a distal surface of the spacer 106. The light reflects off of a reflective surface 118 (e.g., a mirrored surface) of the spacer 106 and becomes incident on the grating 108. The reflective surface 118 may be angle-polished and may include, for example, a metallic or dielectric coating to increase the reflectivity thereof. The grating 108 separates the light into the various wavelengths which are directed to a sample 120. Sample 120 may be an object or an in vivo sample, such as an organ or tissue. In one embodiment, the grating 108 may be, for example, a 2000 lines/mm grating. The various excitation wavelengths (li, l₂, and l₃) of the light diffracted by the grating 108 impinge on the sample 120 at locations Ci, X2, and X3. Accordingly, the light can be focused into a line 121 (e.g., a spectrally encoded line). As the rotary junction 114 rotates the illumination probe 102, the light on the sample also rotates, where light at position Xi makes a small diameter ring on the sample 120 and light at position X3 makes a ring having a larger diameter. In an embodiment, the illumination probe provides light to a sample in a forward view configuration. Particularly, at least one diffracted light wavelengths propagates from the grating of the illumination probe substantially along or parallel to an optical axis of the probe, where the optical axis of the probe is the axis extending along the direction of propagation of a light provided from the first fiber through the lens.

[0023] Returning to FIG. 1, imaging apparatus 100 also includes a detector 110 made up of a plurality of light collectors, for example, detection fibers, forming a fiber ring that circles the optical elements of the illumination probe 102. As mentioned above, on an embodiment, the detector 110 is stationary. Each detection fiber in the detector 110 may be, for example, a multi- mode fiber. In an embodiment, the plurality of light collectors (e.g., detection fibers) cover the entire field of view of the illumination probe. The detector 110 may optionally be encased or surrounded by an outer sheath (not shown) to protect the detection optics. This may be formed, for example, by using heat shrink tubing. FIG. 3 is a diagram of a detector for a forward-view SEE imaging apparatus in accordance with an embodiment. As shown in FIG. 3, after collection of the light from the sample through the detector 110 (e.g., a fiber ring), the detector 110 changes shape and becomes a linear array 122 of detection fibers (e.g., multi-mode fibers) that terminate in a line. The linear array 122 of detection fibers may be, for example, a single fiber thick (e.g., the 14x1 fiber area in FIG. 3, 122). In other embodiments, the linear array 122 may be two or more fibers thick. Light from this linear array 122 of detection fibers is collimated by a collimation lens 124 and sent through a grating 126 and a focusing lens 128 before impinging on a sensor such as, for example, line scan camera 130.

[0024] The grating 126 has a grating vector 132 which is shown as an arrow on the grating. The collimating lens 124, grating 126 and focusing lens 128 may comprise a

spectrometer 134 where the linear array 122 of detection fibers terminates at the spectrometer entrance. Other configurations of spectrometers may also be used in accordance with various embodiments. The linear array 122 of detection fibers may cover the majority of or the entire entrance slit of the spectrometer 134. This may help in maintaining spectral resolution of the spectrometer utilizing the most of the collected light. The spectral resolution corresponds to image resolution in a spectral encoded endoscope.

[0025] As mentioned, detector 110 may include a plurality of light collectors, e.g., detection fibers, that are disposed around the illumination probe 102 (shown in FIG.s 1 and 2) in, for example, a ring. FIGs. 4A-4E show end views of an illumination probe and detector in accordance with an embodiment. In one embodiment, the detection fibers 136 completely surround the illumination probe 102 (FIG. 4(A)) and form a fiber ring 110. In other

embodiments, several fibers 136 may be equally spaced around the illumination probe 102 (FIGs. 4(B) and 4(C)) to form the plurality of light collectors. In other embodiments, (FIG. 4(D)), the plurality of detection fibers 110 mostly surround the illumination probe 102, but have a space or channel(s) 138. The space or channel 138 can be used, for example, for one or more endoscopic tool(s). In other embodiments, the detection fibers 110 will not be equally spaced or have an unsymmetrical distribution around the illumination probe 102 (FIG. 4E).

[0026] FIG. 5 shows an end, cross-sectional view of a detector in accordance with an embodiment. The detector 110, including detections fibers (or light collectors) 136 are formed around an inner tubing 142. In FIG. 5, sixteen detection fibers 136 are shown and cover the circumference of the inner tubing 142 and the illumination probe (not shown). In one embodiment, all of the detection fibers 136 used in the detector 110 may be used to cover the imaging field of view of the illumination probe. In another embodiment, a subset of the detection fibers 136 in the detector 110 may be used to fully cover the imaging field of view.

For example, in the embodiment shown in FIG. 5, the light from eight of the detection fibers 136 may be detected. The inner tubing 142 has an inner channel or space 140 configured to house the illumination probe 102 (not shown). The illumination probe 102 (not shown) may be inserted into the inner channel 140. An outer tubing 144 may be provided around an outer diameter of the ring of detection fibers 136 to protect and hold the detection fibers 136. An exemplary process of forming the ring of detection fibers 136 is discussed below with respect to FIGs. 8 A and 8B. The use of a plurality of detection fibers (e.g., multi-mode fibers), increases light collection by the detector 110. A greater number of detection fibers may provide greater reduction in speckle and may increase the signal into the detector 110. In some embodiments, the detection fibers may be packed closely in the ring around the illumination probe. In some embodiments, cladding around the distal end of the detection fibers is removed to increase the packing density of the detection fibers around the illumination probe. Thus, the outer dimeter of the illumination probe including any protective cladding not removed, limits the number of detection fibers that can form the fiber ring. For example, with a 50 pm tubing wall thickness for the illumination probe, and a 145 pm detection fiber diameter (including cladding), with a 6 pm tolerance, there can be 18 fibers surrounding the ring. For 185 pm detection fiber diameter (including cladding), with a 20 mih tolerance, there can be 14 fibers surrounding the ring. For the same detection fibers but with a 100 gm tubing wall thickness for the illumination probe, there can be 20 and 15 fibers, respectively. In some embodiments, there may be two or three rows of rings around the illumination element. Speckle may be reduced by using more than on detection fiber because the detection fibers will be arranged at a different position with respect to the illumination fiber, such that they collect light from the same point on the object with different optical path length. In another embodiment, speckle may be reduced by separating the multiple detection fibers apart as much as possible (bit within the parameters need for a small diameter probe.

[0027] FIG. 6 shows a light collector of a detector in accordance with an embodiment. In

FIG. 6, a light collector 136, for example a detection fiber, has a distal end 150, a proximal end 154 and a longitudinal axis 156. The distal end of the detection fiber 136 has an acute angle 152 with respect to the longitudinal axis 156. The distal end 150 may be, for example, angle- polished to form the acute angle 152. In an embodiment, the acute angle 152 is less than 70 degrees. In one embodiment, the size of the acute angle 152 may be based on the material and numerical aperture (NA) of the detection fiber 136. Forming an acute angle 152 on the distal end of the detection fiber creates a larger detection field of view by, for example, elongating the detection spot as illustrated in FIG. 7. The exemplary detection field of view 160 shown in FIG.

7 results from angle-polishing a distal end of a detection fiber and is elongated (e.g., an elongated detection spot). The density distribution of the detection spot 160 is non-uniform with a denser detection density at the center 162 than at the edge 164. In one embodiment, each detection fiber 136 in the detector 110 (shown in FIG. 5) has an angled distal end. In other embodiments, a subset of the plurality of detection fibers 136 included in a detector 110 has an angled distal end.

[0028] FIG. 8A is a diagram showing a cross-sectional view of a detector surrounding an illumination probe before a heat shrink process in accordance with an embodiment and FIG. 8B is a diagram showing a cross-sectional view of a detector surrounding an illumination probe after a heat shrink process in accordance with an embodiment. In FIG. 8 A, an inner tubing 170 is inserted within a stationary tubing 172. The inner tubing may be, for example, a hypotube and the stationary tubing may be, for example, a polyimide tubing. After the ring of detection fibers 110 is placed around the circumference of the inner tubing 170 and the stationary tubing 172, an outer tubing 174 is placed around the detector 110. The outer tubing is, for example, a heat shrink tubing. In FIG. 8B, an illumination probe 102 with a surrounding rotating tubing 176 are inserted within the stationary tubing 172 after removal of the inner tubing (e.g., the hypotube) 170. The rotating tubing may be, for example, a polyimide tubing. Heat may be applied to the outer heat shrink tubing 174 to fix the outer tubing 174 to the detector 110.

[0029] FIG. 9 is a block diagram of a forward-view SEE imaging system in accordance with an embodiment. The system includes a light source 116 and a fiber 115 coupling the broadband source 116 to a rotary junction 114. Light is provided from the rotary junction 114 and through a fiber 112 to the illumination probe 102. The rotation of the illumination probe 102 is depicted with the circular arrow and the spectrum of light from the illumination probe 102 is incident on a sample (not shown). A detection element 110 is shown as a cross-section, for example, the detector 110 as described above with respect to FIGs 1, 3 and 5-7 above. The light detected by detector 110 is transmitted through fibers 122 and lined up in a linear array at the entrance slit to a spectrometer 134. The spectrometer 134 may be used to detect the intensity of selected wavelengths. The light may then be imaged on a sensor 180. In some embodiments, the sensor 180 is a line scan sensor, such as a line scan camera. The line scan sensor may be a rectangular pixel element having longer dimension of the sensor pixels perpendicular to the grating vector 132 (shown in FIG. 3) of a grating 126 (shown in FIG. 3) in the spectrometer 134. It can also maintain spectral resolution by covering small wavelength width with a shorter dimension of the pixel in the opposite dimension. The line scan sensor may be, for example, a single pixel wide, 2 pixels wide 5 pixels wide, or more, as long as the line scan sensor is rectangular. A computer 182 may be coupled to the sensor 180. The computer 182 may include, for example, a processor, a memory and an input/output interface. Computer 182 may be configured to receive data from the sensor 180, store the data and to perform image processing such as, for example, noise reduction, coordinate distortion correction, contrast enhancement and so on. In addition, the computer 182 may be configured to provide control signals to the various devices in the system, for example, the light source 116, the detector 110, the illumination probe 102 and the rotary junction 114. Commands may be received from a user via a user interface 184, for example, a touch screen, keyboard, mouse, joystick, ball controller or foot pedal. Data and images generated by the system may by displayed on a display 186.

[0030] More specific examples will be explained in the following embodiments. EXAMPLE

[0031] A forward-viewing SEE imaging apparatus was formed using a 500-pm monolithic illumination probe and a detector using light from eight multimode detection fibers. Each of the eight detection fibers had a distal end polished at a 17 degree angle. This design resulted in a lateral resolution of 22.1 pm, a total angular field of view of 100 degrees, and an effective number of imaging elements of 1.1 megapixels. The SEE imaging apparatus was used for preclinical imaging of a swine joint ex vivo.

[0032] The forward-viewing SEE imaging apparatus had a rotating illumination probe and a stationary detector. A broad band light source (e.g., 415 nm to 784 nm) was used to provide light to the illumination probe. The 500-pm illumination probe was designed to diffract and focus the broadband light into a spectrally encoded line centered around an optical axis. The probe included a 250-pm gradient index (GRIN) lens coupled to a 500-pm silica spacer which coupled the light through a mirror surface into a grating on the front surface of the spacer. The rigid length of this illumination probe was 3.87 mm.

[0033] The reflected light from the sample was collected through a stationary circular detector with an array of multimode fibers. The array was composed of sixteen multimode fibers arranged between two pieces of flexible tubing. Using multiple multimode fibers for light detection reduced speckle noise and increased the signal-to-noise ratio (SNR). The multimode fibers used were l85-pm fibers with a numerical aperture (NA) of 0.66. The distal end of each of the eight fibers used for light detection were angle-polished resulting in an elongated detection spot that was slightly shifted outwards from the center. A polishing angle of 17 degrees was used on the distal ends of the multimode fibers of the detector. The theoretical total angular field of view was 102.5 degrees. The multimode fibers were inserted as a circular array between an inner and an outer tubing. Each of the multimode detection fibers were aligned so that the circular edge of the detection spot pointed toward the center of the illumination field of view. A lumen of an inner tubing was used to house the illumination probe and the outer tubing was a heat shrink tub used to hold the multimode fibers. The multimode fibers were fixed by applying hot air flow to the heat shrinkable outer tubing. The resulting imaging apparatus had an overall diameter of 1.27 mm. While sixteen multimode fibers were included in the detector to fill the entire circumference of the illumination probe, eight fibers were used to cover the imaging field of view. The array of eight multimode fibers produced eight spectrally encoded lines on a sensor, which were summed at the sensor. A two-dimensional image was constructed by collecting the spectrally encoded lines at different time points, while the illumination probe was rotating, and stitching them next to each other.

[0034] The present invention has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly states, are possible and within the scope of the invention.

Claims

1. An imaging apparatus comprising:

an illumination probe; and

a detector comprising:

a plurality of light collectors, each of the plurality of light collectors extending from a proximal end to a distal end and having a longitudinal axis, at least one of the light collectors having the distal end formed with an acute angle with respect to the longitudinal axis, wherein the distal ends of the plurality of light collectors at least partially surround the illumination probe and wherein the proximal ends of the plurality of light collectors form a linear array.

2. The imaging apparatus according to claim 1, wherein the plurality of light collectors are multi-mode fibers.

3. The imaging apparatus according to claim 1, wherein the acute angle is less than 70 degrees.

4. The imaging apparatus according to claim 1, wherein the distal ends of the plurality of light collectors form a ring around the illumination probe.

5. The imaging apparatus according to claim 1, wherein at least one tubing is positioned between the illumination probe and the detector.

6. The imaging apparatus according to claim 5, wherein the at least one tubing comprises a rotating tubing and a non-rotating tubing that are positioned between the illumination probe and the detector.

7. The imaging apparatus according to claim 1, wherein the acute angle of the distal end of the at least one light collector is a polished angle.

8. An imaging system comprising:

a light source;

an illumination probe coupled to the light source;

a rotary junction coupled to the illumination probe and configured to rotate the illumination probe;

a detector comprising:

a plurality of light collectors, each of the plurality of light collectors extending from a proximal end to a distal end and having a longitudinal axis, at least one of the light collectors having the distal end formed with an acute angle with respect to the longitudinal axis, wherein the distal ends of the plurality of light collectors at least partially surround the illumination probe and wherein the proximal ends of the plurality of light collectors form a linear array; and

a processor coupled to the detector and configured to receive data from the detector and process the data to generate an image.

9. The imaging system according to claim 8, wherein the plurality of light collectors are multi-mode fibers.

10. The imaging system according to claim 8, wherein the acute angle is less than 70 degrees.

11. The imaging system according to claim 8, wherein the distal ends of the plurality of light collectors form a ring around the illumination probe.

12. The imaging system according to claim 8, wherein at least one tubing is positioned between the illumination probe and the detector.

14. The imaging system according to claim 12, wherein the at least one tubing comprises a rotating tubing and a non-rotating tubing that are positioned between the illumination probe and the detector.

15. The imaging system according to claim 8, wherein the acute angle of the distal end of the at least one light collector is a polished angle.