Patent Application
20120330101
In various embodiments, the present invention relates to endoscopic imaging probes, and, in particular, to handheld probes suitable for use in surgical procedures and for integration into surgical instruments.
Advances in minimally invasive surgical procedures and the development of novel surgical instruments have enabled surgeons to access delicate areas of the body that were previously off-limits or only accessible through highly invasive procedures. These innovations have resulted in significant improvements in treatment options and patient outcomes for a variety of maladies. In addition, new diagnostic techniques—including new or improved imaging modalities—provide surgeons with more information and a better understanding of the area being treated, enabling them to collect, for example, real-time and non-destructive biopsies including analysis of regions that are typically difficult to access. One such useful diagnostic technique is optical coherence tomography (OCT), an interferometric technique for noninvasive diagnosis and imaging utilizing (typically infrared) light. OCT has transformed the field of ophthalmology and promises to have a similar impact on a variety of other medical specialties. OCT systems have become a mainstay in hospitals and ophthalmology clinics for diagnostic evaluation and imaging purposes. Furthermore, advances in technology have enabled smaller imaging device, such as, e.g., handheld endoscopic probes, that provide minimally invasive imaging of regions of interest not accessible using external imaging devices. Endoscopic probes are, during use, at least partially inserted into the patient's body. As will be appreciated by one of skill in the art, such probes impose particularly stringent requirements on size and maneuverability.
A particular mode of OCT, termed “A-scan,” provides one-dimensional axial depth scans of the tissue of interest, thus providing information on the identity, size, and depth of subsurface features. A series of spatially adjacent A-scans (typically lying in a straight line) may be combined to form a two-dimensional reconstructed image of the imaged area (termed a “B-scan”), and three-dimensional images, termed “C-scans,” may be formed by “stacking” multiple B-scans. B-scan formation typically requires the scanning of the optical beam across the surface of interest. For example, a surgeon may hold an OCT probe (from which the optical beam emanates) and move his or her hand to sweep the optical beam across the sample of interest. Alternatively, the probe may remain stationary while the beam direction is varied relative to the probe. In one configuration used for this purpose, the beam is deflected by 90° and the probe is rotated, causing a circular scan pattern in a plane perpendicular to the probe axis. Side-scanning in this manner is useful for imaging tubular organs, such as blood vessels or the esophagus. Another configuration, which facilitates forward-scanning, utilizes a pair of angle-cut rotating lenses that produce, in good approximation, a straight-line scan when rotating in opposite directions at the same angular speed. Alternative configurations for forward and/or side scanning utilize, e.g., a microelectromechanical-systems (MEMS) mirror to deflect the beam, or a piezo element to move the lens inside the probe.
In both side-scanning and forward-scanning probes, the lenses are optically coupled to a stationary external imaging console via optical fibers. In configurations that rely on lens rotation, two fibers, coupled by a rotary joint, are generally used to facilitate rotation of the lens relative to the console. Commercially available (“off-the-shelf”) rotary joints are, however, expensive. Moreover, their size precludes integration into the smaller, handheld probes (e.g., probes utilizing a 23-gauge needle) that are required, for example, for retinal surgery or similarly delicate procedures. Similarly, MEMS mirrors and piezo elements generally do not fit within a 23-gauge needle. Consequently, these components are typically mounted externally, placing constraints on the positioning and movement of the probe.
The positioning and orientation of the imaging probe is typically also subject to anatomical constraints. For example, retinal surgical procedures are typically performed via ports or cannulated incisions in the eye near the periphery of the cornea, as illustrated in
Further, as the number of tools to diagnose and treat the underlying condition expands, their combined utility is often curtailed by anatomical constraints. Retinal surgery, for example, generally relies on a variety of instruments (including, e.g., an illuminating light source, a treatment laser, a vitrector, an aspirator, etc.), which cannot all be introduced through the cannulated incisions into the eye simultaneously. Similarly, orthopedic procedures (e.g., knee reconstruction) typically involve a variety of instruments and tools, of which only a limited number can be inserted into the patient for access to the surgical site at any particular moment. The need to constantly swap out instruments because of limited access to the surgical site is frequently a problematic and time-consuming distraction to the surgeon.
In view of the various limitations of existing endoscopic imaging probes, there is a need for more compact (and, desirably, less costly) imaging probes that circumvent anatomical constraints, as well as for integrated devices that provide both imaging and treatment functionalities.
The present invention provides, in various embodiments, endoscopic imaging probes, and methods of operating them, that facilitate imaging an anatomic region of interest perpendicularly to the tissue surface while allowing the probe to be oriented at an angle to the surface. This flexibility is accomplished with an angle-cut lens, prism, or other structure that deflects the optical beam, typically by less than 90°, and focuses the light off-axis. Using a suitable actuation system, the lens may be rotated back and forth to scan the focus across the surface, resulting in a scan path following an arc segment. As long as the angle of rotation does not exceed a set threshold (e.g., 60°, or some other angle, depending on the particular application), the arc segment approximates a desired straight-line scan sufficiently for practical purposes.
In certain embodiments, the probe includes a single lens, which is connected to an exterior imaging console via an optical fiber. A rotary joint is not required since, in the intended mode of operation, the lens and fiber do not undergo full 360°-rotation, let alone multiple rotations in the same direction, but rotate by less than 180° (preferably by no more than 90°, and in certain embodiments by only 30° or less) in each direction. The simplified design of such a single-lens probe—compared, e.g., with that of a paired-angle-rotation scanning (PARS) probe as described above—renders it particularly suitable for small hand-held probes as well as, as a result of the reduced cost, for disposable probes. However, it is also possible to operate a dual-lens probe in a manner that achieves off-axis scanning and avoids the need for a rotary joint: by rotating only one of the lenses while keeping the second lens, which is coupled to the optical fiber, still.
For some applications, it is desirable to facilitate larger-angle rotations of the lens(es) and/or continuous rotation in the same direction, which generally requires a rotary joint. Various embodiments of the invention are directed to rotary joints that, due to greater compactness compared with that of off-the-shelf joints, can be integrated into the imaging probes, specifically, into tubular needles into which the lenses are assembled. In one embodiment, the fiber coupled to the lens and the fiber coupled to a fiber connector interfacing with the imaging console are aligned and held in place by a fiber ferrule and butt-coupled against each other. In another embodiment, the two fibers are coupled to each other via a pair of lenses that can rotate relative to one another. The small gap between the two fiber ends or the two coupling lenses, respectively, may be filled with an index-matching gel.
In addition to imaging probes with advantageous features, the present invention provides, in several embodiments, integrated probes having both imaging and treatment functionalities. One embodiment, for example, is directed to a vitrector, i.e., a surgical tool for extracting vitreous from the eye. (Consistently with its usage in the medical community, the term “vitreous” is, herein, used as a noun, denoting material from the vitreous body of the eye.) The vitrector includes an outer tube with a side window through which vitreous can enter, and an interior rotating or reciprocating cutter tube that provides the necessary shear forces for cutting the vitreous. An integrated imaging probe, including a lens mounted to the distal end of the cutter tube and moving along with the tube and an optical fiber run through the cutter tube, enables imaging the vitreous during the surgical procedure. Another embodiment is directed to an injection device that includes a fluid-delivery tube with integrated imaging components. Yet another embodiment provides a surgical drill device with a hollow core housing an optical fiber and lens. These hybrid devices facilitate monitoring the effect of the treatment procedure in real-time, and avoid the need to swap instruments. Further, in certain embodiments, they synergistically utilize the same actuation system to rotate or translate both the surgical tool and the imaging lens.
Accordingly, in a first aspect, the invention provides a scanning imaging probe including an optical fiber, and a lens assembly including a single lens structure (e.g., a gradient-index lens) mounted in a tube surrounding the fiber. The lens structure is placed at a distal end of the tube, optically coupled to the fiber, and shaped so as to deflect light coupled from the fiber into the lens structure and focus the light off-axis beyond the distal end. For example, the lens structure may consist of an angle-cut lens, or include or consist of a prism. The lens structure and the optical fiber may be aligned co-axially with each other. In some embodiments, the fiber is fused to the lens structure; in other embodiments, it is coupled to the lens structure via a fiber ferrule.
The imaging probe further includes an actuation mechanism for moving the lens assembly so as to scan the focus along a line. (As used herein, the term “line” is not limited to straight lines, but includes, e.g., arc segments or other curved lines. However, the term “linear” is, consistently with its usage in the technical field, used in reference to a straight-line scan.) In some embodiments, the actuation mechanism causes rotation of the lens assembly around an axis of the assembly (i.e., an axis of the tube). The rotation may be reciprocating and not exceed 90° (or, in some embodiments, 60° or 30°) in each direction. In some embodiments, the actuation mechanism causes reciprocation of the lens assembly along an axis of the assembly. The actuation mechanism may be a pneumatic, hydraulic, electromagnetic, or motor-driven mechanical actuation mechanism. In certain embodiments, the mechanism includes a transmission reconfigurable to dynamically alter the speed and/or the direction of actuation.
The outer diameter of the tube may less than 1 mm; in some embodiments, it is less than 520 μm. The tube may include or consist of a hypodermic needle, e.g., a 20-gauge needle, 23-gauge needle, a 25-gauge needle, or a 31-gauge needle. The probe may include an additional, outer tube surrounding the lens assembly, which remains stationary when the lens assembly moves. The probe may be a handheld probe, i.e., it may be sized for hand operation and, for example, include a handle having a shape and/or texture that facilitates a secure grip.
In a second aspect, the invention relates to a method of scanning tissue at a surface of the tissue, using an imaging probe that includes a rotatable lens structure shaped so as to focus a light beam exiting the lens structure off-axis beyond a distal end of the probe. The method involves positioning the probe such that the light beam, at a first rotational position of the lens structure, is incident on the tissue surface substantially perpendicularly, and scanning the tissue along an arc-shaped path by rotating the lens from a second rotational position to a third rotational position, wherein the second and third rotational positions are selected such that the lens structure passes through the first rotational position during the rotation. In some embodiments, the lens is rotated between the second and third positions in one rotational direction, and then back from the third to the second position in the opposite rotational direction. The rotation may be limited to (i.e., not exceed) a 90° angle, or, in some embodiments, a 30° angle. In certain embodiments, the method is practiced with an imaging probe that includes a second lens structure proximal to the rotatable lens structure, which couples light from an optical fiber to the rotatable lens structure; in this case, the method further includes keeping the second lens structure stationary while rotating the rotatable lens structure.
In a third aspect, a scanning imaging probe including two lens assemblies is provided. The first lens assembly includes a first tube and, mounted therein at a distal end, a first deflecting lens structure. The second lens assembly is coaxially disposed inside the first tube proximal to the first lens, and includes a second tube and, mounted therein at a distal end, a second deflecting lens structure. The second lens assembly is rotatable relative to the first tube. The probe includes actuation mechanisms associated with the first and second deflecting lens assemblies for rotating the lens assemblies independently of one another, The first and second lens assemblies are configured such that, when they are rotated, light is focused beyond the distal end of the first lens assembly and the focus is moved along a scan pattern. In some embodiments, the first and second deflecting lens structures are angle-cut lenses. The probe may further include an outer tube surrounding the first and second lens assemblies, the outer tube remaining stationary when the lens assemblies rotate.
The probe further includes a rotary joint disposed inside the second tube proximal to the second deflecting lens structure, and an optical fiber, coaxially disposed inside the second tube and optically coupling the rotary joint to the second deflecting lens structure, for coupling light into the second deflecting lens structure. In some embodiments, the rotary joint couples the optical fiber to a second optical fiber connectable to an imaging console, the second optical fiber remaining stationary when the second lens assembly rotates. The optical fiber and the second optical fiber may be axially aligned in a fiber ferrule and butt-coupled against each other (such that the coupling region and fiber ferrule collectively form the rotary joint). Alternatively, the two optical fibers may be coupled via a co-axial pair of collimating or converging lenses, which may be butt-coupled against each other. The gap between the two optical fibers or between the collimating lenses, respectively, may be filled with index-matching gel. In certain embodiments, the distance between the second deflecting lens structure and the rotary joint exceeds the coherence length of the light (which depends on the light source used).
A fourth aspect of the invention relates to a vitrector with integrated imaging capability. The vitrector includes a vitrector tube with a side port at a distal end through which vitreous can be admitted, and a suction mechanism associated with the vitrector tube, which draws the vitreous towards the proximal end of the vitrector tube. Further, the vitrector includes a tubular cutter, coaxially disposed in the vitrector tube, and, associated with the cutter, an actuation mechanism for moving the cutter relative to the vitrector tube so as to cut the vitreous for suctioning by the suction mechanism. The vitrector also includes an optical fiber coaxially disposed in the cutter, and a lens structure, disposed at a distal end of the tubular cutter and optically coupled to the optical fiber, for focusing light coupled into the lens structure from the optical fiber beyond the distal end so as to image a region about the focus.
The lens structure may be shaped to deflect the light and focus it off-axis (e.g., it may include or consist of an angle-cut lens), such that movement of the cutter simultaneously causes the focus to be scanned along a line. In some embodiments, the actuation mechanism is a rotary mechanism, causing the focus to be scanned along an arc segment. In other embodiments, the actuation mechanism is a reciprocating mechanism, causing the focus to be scanned along an axis parallel to an axis of the vitrector tube. The actuation mechanism may be or include a pneumatic, hydraulic, electromagnetic, or motor-driven mechanical actuation mechanism.
A fifth aspect of the invention relates to an injection device with integrated imaging capability. The injection device may include a hollow, tubular needle for piercing an injection site and delivering fluid to the site; an optical fiber disposed in parallel to the needle; and a lens, mounted at a distal end of the needle and optically coupled to the optical fiber, for focusing light coupled into the lens from the optical fiber at a focus beyond the distal end so as to image a region about the focus. In certain embodiments, the lens may be shaped so as to deflect the light and focus it off-axis. The device may further include an actuation mechanism for rotating and/or reciprocating the lens.
The optical fiber and the lens may be disposed inside and co-axially with the needle. In some embodiments, the needle includes a porous structure proximal to the lens that allows fluid egress from the needle. In alternative embodiments, the lens may be of a diameter that facilitates fluid flow around the lens to an opening at the distal end of the needle. In yet another embodiment, the optical fiber and lens are disposed along an outer wall of the needle. The lens is recessed from a tip of the needle. The device of claim 33, further comprising a plunger for ejecting the fluid.
A sixth aspect of the invention relates to an alternative injection device with integrated imaging capability. The device includes a hollow, tubular needle for piercing an injection site and delivering fluid to the site; an optical fiber coaxially disposed inside the needle; and a lens optically coupled to the optical fiber and movable inside the needle from a position proximate a proximal end to a position proximate a distal end. The lens is configured such that it, when positioned at the distal end, focuses light coupled into the lens from the optical fiber distally to the distal end so as to image a region about the focus. The injection device may include a plunger for ejecting the fluid and pushing the lens towards the distal end.
A seventh aspect of the invention relates to a surgical drill with integrated imaging capability. The surgical drill includes a drill bit with a bore along its axis; an optical fiber disposed in the bore; and, mounted in the bore at a distal end of the drill bit, a lens for focusing light coupled into the lens from the optical fiber to a focus beyond the distal end so as to image a region about the focus. The lens may be shaped so as to deflect the light and focus it off-axis, rotation of lens with the drill causing the focus to scan along a circular path. The surgical drill may further include a tube disposed in the bore and rotatable relative to the bore, and a second lens, mounted in the tube at a distal end thereof, for coupling the light from the optical fiber into the lens at the distal end of the drill bit. Both lenses may be angle-cut lenses that deflect the light, such that simultaneous rotation of the drill bit and the tube causes the focus to be moved along a scan pattern.
In an eighth aspect, the invention provides a system for endoscopically scanning a tissue sample. The system includes a light source, a detector, an interferometer in optical communication with the light source and the detector, a handheld endoscopic imaging probe located in a sample arm of the interferometer, and an imaging engine, in communication with the detector, for processing an interferometric signal received from the detector. The imaging probe serves to communicate an optical beam from the light source to the sample; it includes one or more lens structures shaped so as to direct the beam to an off-axis focus, and an associated actuation mechanism for scanning the focus laterally along the sample. The imaging engine may, in response to a user request, captures an image or a video of the sample and store the image or video for later viewing.
Where, in the above description of aspects of the invention, various features of embodiments are mentioned with respect to one aspect, such features may also be applicable to and used in one or more other aspects, as will be readily appreciated by a person of skill in the art from the summary and the following detailed description of the invention.
The foregoing will be more readily understood from the following detailed description of the invention, in particular, when taken in conjunction with the drawings, in which:
The shadings in the drawings are generally used for illustrative convenience, and not intended to denote any particular material.
1. Systems and methods for endoscopic imaging 1.1. OCT imaging systems
Imaging probes in accordance with various embodiments may be used with a variety of imaging modalities, including, for example, optical coherence tomography (OCT), confocal microscopy, fluorescence imaging, two-photon fluorescence imaging, Raman imaging, and coherent anti-Stokes Raman spectroscopy. Imaging systems that support these modalities are well-known to those of ordinary skill in the art of imaging (in particular, medical imaging). To provide just one example, and illustrate where the probe fits within the larger imaging system, an OCT system is described in the following. OCT imaging can provide one-, two-, or three-dimensional scans of biological tissues at sub-micrometer axial and/or lateral resolution. The advantages of OCT include high imaging resolution, real-time imaging, non-invasiveness, and compact size.
Various features of sample 240 reflect the light in different amounts or from different depths. The reflected light is combined with light reflected by the reflector 220 (which typically includes or consists essentially of a mirror). Light reflected from features in the vicinity of the focus remains coherent, resulting in an interference pattern that provides information about the spatial dimensions and location of these features within sample 240. Light scattered off features that are located more than a coherence length away from the focus, on the other hand, are effectively filtered out by the interferometer 210. The interference pattern is captured with the photodetector 260, and processed by the imaging engine 270.
Imaging engine 270 may be a personal-computer-(PC)-based architecture, and may include a high-speed analog-to-digital converter (for example, on a PCI bus) that digitizes the output of photodetector 260 at a sampling rate ranging from several million samples per second to several billion samples per second. The digitized data may be processed by the PC processor based on straightforwardly implemented software instructions, e.g., instructions for performing a
Fourier transform, processing the image signals and reconstructing images therefrom, and/or deriving biometrics or other quantitative data from the image data. Alternatively to using off-the-shelf-hardware such as a PC, the image acquisition and processing functionality may be implemented in dedicated hardware, such as an application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), digital signal processor (DSP), graphical processing unit (GPU), or a combination of these devices. The imaging engine 270 may also have a customary user interface including, e.g., a monitor and/or input devices such as mouse and keyboard.
In various embodiments, the imaging engine 270 provides image reconstruction and display capabilities that enable real-time or near real-time viewing of the imaged target. For example, an LCD showing reconstructed OCT images may be mounted above a binocular microscope used by a retinal surgeon during a procedure. The surgeon can observe structures in the patient's eye (e.g., the retina) under the microscope as well as in OCT images on the display thereabove. While useful in many situations, such an arrangement may increase the risk and complexity of certain procedures that are highly sensitive to the exact position of the handheld imaging probe. For example, during a vitrectomy procedure, the surgeon may wish to image a region as close to the retina as possible (often less than one millimeter away). If the surgeon shifts focus from the view provided by the binocular microscope to the OCT display, he risks contacting and possibly damaging the patient's retina with the tip of the imaging probe. As another example, a surgeon, after having photocoagulated or ablated regions of the retina with a laser, may want to image the entire burn region to ensure that the results are satisfactory, requiring her to move the OCT probe across the area of interest. If the surgeon views the OCT image stream while scanning the probe, the probe tip may, inadvertently, contact the retina.
To avoid such problems, the imaging engine 270 includes, in various embodiments, means to capture snapshot images or videos for display over an extended period or at a later time, allowing the surgeon to image an area of interest, and then to remove the imaging probe from close proximity to the region of interest to safely view the captured image(s) immediately afterwards without risking damage to the area (e.g., the retina). For this purpose, the imaging engine 270 may include buffer memory (e.g., RAM) sufficient to store the captured image(s). In some embodiments, the surgeon may activate the capture-and-display modes by means of a footswitch or a button on the handheld probe (e.g., by pressing and holding the switch or button during capture mode and releasing it to display, or, alternatively, by pressing and releasing the button or switch once to activate the capture mode and a second time to activate the display mode). In alternative embodiments, switching between the two modes is achieved by voice activation. The images may, further, be stored long-term (e.g., in non-volatile memory) for review at a later time.
1.2. Single-lens imaging probes
Various embodiments of the present invention are directed to imaging probes including (i) a hypodermic needle or similar tubing made of, e.g., stainless steel or a biocompatible polymer such as polyimide or polyether ether ketone, (ii) a lens structure including or consisting of, e.g., a gradient-index (GRIN) lens mounted in or on the needle at the distal end, and (iii) an optical fiber (e.g., a single-mode fiber) disposed inside the needle and optically coupled to the lens structure. Optionally, the imaging probe may further include (iv) an actuation mechanism for rotating or otherwise moving the tubing and lens structure (herein collectively referred to as the “lens assembly”), and, in some embodiments, (v) an outer tube that remains stationary when the lens assembly is moved so that it isolates the surrounding tissue from the movement, and which may (but need not) include a transparent window at the distal end to further isolate the tissue from the rotating lens structure. For use as a handheld probe, the various functional components listed above are typically enclosed in and/or attached to a suitably shaped and sized casing, as illustrated below with reference to
To facilitate miniaturization of the imaging probe for better access to body tissues, the outer diameter of the tubing and the diameters of the lens and optical fiber may be on a sub-millimeter scale. For example, if a commercial hypodermic needle is used for the tubing, a needle with a gauge of 20 or higher may be used. In general, the higher the gauge number, the smaller is the outer diameter of the needle. A 20-gauge needle, for example, has a nominal outer diameter of 908 μm; 23-gauge, 25-gauge, and 31-gauge needles have nominal outer diameters of 642 μm, 514 μm, and 260 μm, respectively. Of course, hypodermic needles used in imaging probes as described herein need not have outer diameters matching these nominal values, but may be customized needles having any diameter suitable for the particular application. In one embodiment, the lens and optical fiber both have a diameter of 125 μm. The fiber and lens may be housed, for example, in a regular 31-gauge needle, whose nominal inner diameter is 133 μm.
As conceptually illustrated in
In use, the imaging probe is preferably positioned and oriented such that the focused beam is substantially perpendicular to the tissue surface to be imaged, e.g., such that the incidence angle, as measured between the beam and the surface normal, is less than 15°, preferably less than 5°. Advantageously, imaging probes that focus off-axis can achieve this perpendicularity, with suitably selected deflection angles, in anatomic environments that hinder introduction of the probe itself perpendicularly to the surface (as illustrated, e.g., in
Moreover, off-axis probes may provide B- and C-scanning capabilities with a single lens (or lens structure). Specifically, in various embodiments, the lens assembly (i.e., the tubing and lens structure) is rotatable around or translatable along the probe axis, which facilitates lateral scanning of the beam, i.e., scanning across the tissue surface. In a single-lens probe that focuses on-axis, by contrast, rotation does not move the beam focus, and co-axial movement only shifts the focus in the direction of the beam. Therefore, existing forward-imaging scanning probes utilize at least two lenses. Herein, reference to a “single lens,” or a “single lens structure,” indicates that the beam-focusing and -deflecting optics at the distal end of the probe includes only one (i.e., no more than one) lens and, if applicable, an attached deflection component such as a prism. It does not necessarily imply that no additional lenses are used elsewhere in the imaging probe (although, in many embodiments, the focusing lens is the only lens in the probe).
When the lens assembly is rotated, the beam sweeps along a conical surface. A full rotation by 360° creates a circular scan pattern; a rotation by less than 360° results in an arc segment. The radius and curvature of the arc segment (and the circular scan pattern) can be determined through simple trigonometry, and depend on the angle of deflection (i.e., the angle between the off-axis light beam and the probe axis) and the distance to the target, which may be chosen and optimized for a particular application. Of course, when the beam rotates around the probe axis, it generally loses its original perpendicularity to the tissue surface (although curvature of the tissue surface may, in certain configurations, somewhat compensate for this effect). In a typical usage scenario, however, the lens assembly is rotated by significantly less than 360° (e.g., by an acute angle)) in one direction, and then by the same amount in the opposite direction (whereby the beam is returned to its original position), which limits the deviation from perpendicular incidence. In various embodiments, the rotation angle is in the range from 15° to 60°; e.g., it may be about 30°. Further, the probe may be oriented such that perpendicular incidence is achieved about mid-way along the scan path, which reduces the deviation from perpendicularity to about one half (Also, non-perpendicular incidence is generally less important when the probe tip is closer to the tissue to be imaged.) Limiting the rotation of the fiber may also serve to minimize the strain on the fiber, reducing or eliminating the risk of damage to the fiber as well as undesirable effects of strain on, for example, the polarization of the light in the fiber.
Off-axis rotating scanning probes are useful in many scenarios because they allow capturing a B-scan without requiring a full rotation of the lens assembly, which would necessitate a costly and complicated fiber-optic rotary joint, as used with most existing PARS probes. As illustrated in
As each partial rotation of the lens assembly provides a separate B-scan, rotating the lens first clockwise and then by the same amount counterclockwise yields two B-scans. The imaging engine can utilize one or both of these B-scans; for example, it may display one B-scan image and discard the other, display two sequential B-scan images, or implement an averaging algorithm to combine the two B-scans to produce a single B-scan with an increased signal-to-noise ratio. The actuation of the lens assembly may be performed at a high speed, allowing for a high image-acquisition rate; for example, video-frame rates of about 25 frames per second may be supported.
In some embodiments, the lens assembly is translated forward and backward rather than rotated. For example, an off-axis probe that deflects the light beam by 45° or 90° can provide angled-scanning or side-scanning B-scan capabilities on an axis parallel with the lens assembly tubing, which may be useful for some applications. For example, in anterior eye surgery, it may be beneficial to insert the instrument in parallel to the structure of interest rather than pointing at it. Further, an imaging probe allowing B-scanning parallel to the probe axis is more suitable for incorporation into guillotine-type vitrectors, as described in detail below.
Several mechanical actuation mechanisms may be employed in scanning imaging probes to achieve the desired rotation or axial translation of the lens assembly. For example,
In an alternative embodiment, illustrated in
Yet another set of embodiments utilizes electromagnetic drive mechanisms to achieve the rotary or forward-backward mechanical actuation. For example, the probe shown in
Scanning imaging probes with a single-lens focusing optic provide cost savings and simplify manufacture and assembly, compared with multiple-lens designs as used in conventional PARS imaging probes. However, arc-shaped scan patterns (approximating the desired straight-line scan) may also be accomplished using a PARS probe or similar dual-lens design (as described in detail in the next section). PARS probes generally include two nested lens assemblies (each including a lens structure mounted to a tube) that are rotatable independently of each other, and an optical fiber that couples the inner lens to the external imaging console. Methods of using such probes to generate off-axis scan patterns generally involve rotating only the outer lens assembly, and holding the inner lens assembly, and with it the optical fiber, stationary. Although PARS probes typically include rotary joints, such a joint is not necessary if the probe is used like a single-lens probe. Even if the inner lens assembly is rotated (instead of or in addition to the outer lens), a rotary joint is not needed as long as the rotation is limited, e.g., to an acute angle in each direction.
1.3. Multiple-lens imaging probes with rotary joints
Various embodiments of the present invention are directed to scanning imaging probes (e.g., handheld probes for us in medical applications) that incorporate multiple rotating angle-cut lenses (or other deflecting lens structures) which collectively enable forward-scanning as well as laterally offset scanning (e.g., under a 45° or 90° angle with respect to the probe axis). The general configuration of the main functional components of such probes is illustrated in an exemplary embodiment shown in
Depending on the relative orientations of the angled surfaces of the two lenses 706, 712, the light is focused on-axis or off-axis along a continuum of possible distances from the axis.
The inner tube 702 and the outer tube 714 are free to rotate independently of each other, thus allowing the relative lens orientations to be changed and the focus, as a result, to be moved along a scan pattern. An approximately linear (i.e., straight-line) scan pattern (i.e., in medical parlance, a typical B-scan) can be achieved by rotating the two lens assemblies at the same angular speed, but in opposite directions. A variety of other scan patterns (including, e.g., spirals and other patterns resembling Lissajous figures) can be achieved by varying the speed and/or direction of the two lens assemblies relative to each other. In typical usage, the lens assemblies may rotate a full 360° either clockwise or counter-clockwise, or they may rotate a lesser amount, e.g., 180°, in one direction and then rotate the same amount in the reverse direction. The first rotation scheme is more readily suited to a handheld probe powered by a standard motor, whereas the second rotation scheme is more readily suited to a pneumatic push-pull-driven probe (where the lens assembly is “pushed” in one rotary direction and then “pulled” in the opposite rotary direction).
Due to the rotation of the inner lens assembly, a means of providing rotation of the optical fiber 704 without interrupting or degrading the optical signal path is required. In standard dual-lens probes, a fiber-optic rotary joint is used for this purpose. However, currently available rotary joints are usually expensive, complex in design, and often engineered for long-term heavy use in extreme environments, which renders them unsuitable for disposable instruments, as are desired for some medical applications. Further, they are typically large, heavy, and bulky, and thus unsuited for incorporation into a handheld probe. To address these problems, the present invention provides, in various embodiments, simpler and smaller rotary joints that can be integrated into the handheld probe without negatively impacting signal quality.
An even simpler rotary joint 730 is shown in
Regardless of its particular embodiment, the rotary joint (e.g., joint 708 or 730) is, where feasible, preferably located at a distance from the pair of angle-cut lenses that exceeds the coherence length of the light source. This way, reflections that may occur at the rotary joint interface (e.g., the interface between the two fibers or between the two collimating lenses) are prevented from affecting the image quality. Currently available commercial light sources typically have coherence lengths in the range from about 4 mm to about 40 mm. While longer coherence lengths may be desirable for imaging within a longer range of depths, they may prevent placement of the rotary joint at a distance from the lens exceeding the coherence length (due to the limited length of the handheld probe). Thus, the selection of a light source with suitable coherence length generally involves a trade-off between image quality and the axial extent of the imaging region. In some embodiments, a light source with a coherence length in the range of 4-5 mm provides a sufficient scanning range in the axial direction, facilitating placement of the rotary joint a coherence length or more away from the lens.
In imaging probes with two or more lenses at the distal end, each lens assembly generally has its own associated actuation mechanism, although certain components of the mechanisms may be shared. Several methods of providing mechanical actuation to achieve the desired rotation are available. Some embodiments utilize one or multiple motors (e.g., DC, brushless, stepper, or servo motors), in conjunction with transmission means (such as one or more gears, a belt-drive, or a friction-based transmission) for transferring the energy from the motor to the lenses. The actuation mechanism(s) may also include a means of dynamically changing or altering the configuration during use (e.g., by including or removing gears by means of a lever that moves them into or out of place), for example, to provide variable speed or alter the direction of rotation.
Other embodiments utilize pneumatic power, e.g., are configured in a constant-pressure or constant-vacuum configuration or, alternately, in a push-pull configuration. For example, an external pump and controller may provide pneumatic power to the handheld probe (e.g., via one or multiple flexible tubes), which is used to turn one or multiple small turbines mounted coaxially to the lens assemblies, i.e., such that the tube of the lens assembly serves as the axis of the turbine and both rotate together when driven by the pneumatic pressure or vacuum. In one embodiment, a turbine can be mounted on both lens assembly tubes and configured such that the lens assemblies rotate in opposite directions. A similar configuration can also be achieved utilizing hydraulic power in lieu of pneumatic power. Additional embodiments incorporate drive mechanisms driven by a solenoid or other electromagnetic means, as described above with respect to
The features, structures and components described herein with respect to dual-lens imaging probes can be readily applied to probes with three or more lenses a well. A general multi-lens probe may, for example, include an arbitrary number of coaxial, nested lens assemblies, each comprising a tube and lens structure. The lens assemblies may be movable relative to one another, and any or all of them may have respective associated actuation mechanisms. One or more rotary joints as described above may be used to connect the probe, or the individual lens assemblies therein, to external equipment.
2. Integrated tools
During surgical or other medical procedures, it is often desirable to image the region undergoing treatment to optimize the procedure, monitor treatment progress in the target tissue, and avoid unnecessary invasion into or damage of surrounding tissues. In the past, physicians were often limited to intermittent imaging, alternating with treatment, as anatomical and other constraints prevented the simultaneous use of endoscopic imaging probes and treatment devices. Advantageously, various imaging probes in accordance with the present invention are suitable, due at least in part to their compactness, for integration into various surgical and similar devices, facilitating imaging simultaneously with treatment. Accordingly, in certain embodiments, the invention provides endoscopic probes that combine imaging and treatment functionality. Specific embodiments are described below.
2.1. Vitrector with integrated imaging probe
Vitrectors typically come in two general varieties: as rotating vitrectors or guillotine vitrectors. In rotating vitrectors, shown in
To provide imaging functionality in the vitrector, a lens 810 may be attached to the cutter tube 806 or 808 at the distal end, and coupled to an optical fiber 812 that is run through the cutter tube along an axis thereof The lens may be a simple forward-focusing lens that allows A-scans ahead of the probe. Such functionality is useful, for example, to detect the distance of the instrument tip to the retina and warn the surgeon (e.g., with an audio alarm) if it comes to close. Preferably, however, the lens 810 is angle-cut, as shown, or otherwise shaped to focus light off-axis. The lens 810 moves with the cutter tube, resulting in an arc-shaped scan pattern for a rotating cutter 806, and in a linear scan parallel to the probe axis for a reciprocating cutter 808. Thus, the same actuation mechanism that moves the cutter tube inherently also provides for the rotation or translation of the lens 810. This synergy between the surgical instrument and the imaging probe contributes to the compactness and small footprint of the combined device. In some embodiments, a non-moving transparent window is placed over the moving lens (e.g., mounted to the outer tube 800) to isolate the lens from the vitreous and thereby avoid spooling of the vitreous. (Note that the outer tube 800 itself is typically stationary and, thus, does not cause any spooling concerns.)
A vitrector with integrated imaging functionality is well-suited for vitreoretinal surgery, where surgeons have limited access to the surgical site in the eye, rendering multi-function devices that reduce or eliminate the need to swap out instruments highly desirable. OCT imaging is very useful both during and after a vitrectomy procedure for locating vitreous and ensuring that all excess vitreous has been removed, as unidentified vitreous can result in unintentional tears in the retina during a surgical procedure, complicating the procedure and diminishing patient outcome. 2.2. Injector with integrated imaging probe
In various embodiments, a handheld imaging probe is integrated with a syringe for administering injections (e.g., of a drug, enzyme, or biochemical marker, and provided in the form of, e.g., a solution, emulsion, colloid, etc.). In some embodiments, simple A-scan imaging (e.g., OCT or two-photon fluorescence imaging) is facilitated, whereas other embodiments also provide B-scan capabilities.
In another embodiment, illustrated in
In yet another embodiment, shown in
Integrating imaging capabilities into injection device is useful for imaging before, during, and/or after the injection, for example, to locate and target the optimal injection site, to observe the injection to verify that the desired injection site was properly targeted, to observe the effect of the injection, to monitor the physical response to the injection, etc. In many cases, this requires only A-scan capabilities. However, where B-scan capabilities are desired, they can be provided by straightforward modifications to the exemplary embodiments described above. For example, in the devices shown in
In some embodiments, an imaging probe is incorporated into a surgical drill device, as used, e.g., in orthopedic surgery.
The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. In addition, having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. For example, while various imaging probe embodiments are particularly suited for use in endoscopic devices, they may also be used in non-endoscopic applications. Further, the integration of imaging probes in accordance herewith into therapeutic devices is by no means confined to vitrectors, injection devices, and surgical drills, as were described in detail for illustrative purposes. Accordingly, the described embodiments are to be considered in all respects as only illustrative and not restrictive.
The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/489,658, filed on May 24, 2011, the entire disclosure of which is hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61489658 | May 2011 | US |
