Patent Publication Number: US-11647907-B2

Title: Surgical devices and methods utilizing optical coherence tomography (OCT) to monitor and control tissue sealing

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 16/275,913, filed on Feb. 14, 2019, which is a continuation of U.S. patent application Ser. No. 14/052,827, filed on Oct. 14, 2013, now U.S. Pat. No. 10,206,583, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 61/720,817, filed on Oct. 31, 2012. The entire contents of each of the foregoing applications are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to surgical forceps having optical components for monitoring and controlling tissue sealing. More particularly, the present disclosure relates to open or endoscopic forceps that incorporates Optical Coherence Tomography (OCT) system components to monitor and to provide feedback for controlling a tissue sealing. 
     Description of Related Art 
     Existing energy-based tissue-sealing surgical forceps use different types of energy to heat tissue. The different types of energy used to heat tissue include direct heat conduction from a heating element, RF current, ultrasound, and light. A typical energy-based tissue-sealing surgical forceps includes jaw members for grasping and compressing the tissue and applying energy to the tissue. 
     During a surgical procedure, it is important for a surgeon to be able to determine the status of a tissue seal, e.g., the quality of a tissue seal. This feedback allows a surgeon to appropriately operate the tissue-sealing surgical forceps to create a high-quality tissue seal. Existing tissue-sealing surgical forceps and associated systems may not provide sufficient information about the status of a tissue seal. 
     SUMMARY 
     As used herein, the term “distal” refers to that portion that is further from an operator while the term “proximal” refers to that portion that is closer to an operator. As used herein, the term “treat” refers to performing a surgical treatment to tissue including, but not limited to heating, sealing, cutting, sensing, and/or monitoring. 
     As used herein, the term “light source” broadly refers to all types of devices or elements that generate or transmit light for medical use (e.g., tissue treatment). These devices include lasers, light emitting diodes (LEDs), lamps, and other devices that generate light having a wavelength that is within the light spectrum (e.g., from infrared light to ultraviolet light). Also, the light sources described herein may be used interchangeably. For example, an LED light source may be used interchangeably with a laser light source. 
     As described in more detail below with reference to the accompanying figures, the present disclosure relates to open or endoscopic surgical forceps that incorporates optical and electrical components for performing Optical Coherence Tomography (OCT) to image tissue for diagnostic or identification purposes, or to image a tissue seal after a tissue sealing cycle to determine the quality of the tissue seal. In some embodiments, the optical components use broadband, infrared light having a wavelength of between 800 and 1550 nm to image subsurface tissue structures at depths of a few millimeters and with a resolution on the order of micrometers. 
     The optical components may include reference arm optics disposed in a first jaw member of the surgical forceps and sample arm optics disposed in a second jaw member opposite the first jaw member. The optical components also include a light source configured to generate broadband light and transmit the broadband light to the reference arm and the sample arm. The optical components further include a light detector that detects an interference pattern in the broadband light that is reflected back from the reference arm optics and the sample arm optics. The electrical components may include a signal processor that processes the detected interference pattern and displays an image of the sealed tissue on a display device. 
     The optical components may further include a aiming light source for generating an aiming beam and an optical coupler that optically couples the aiming beam to the broadband light before the resulting light is transmitted to the reference arm optics and the sample arm optics. 
     The OCT system may incorporate polarization optics to measure birefringence to determine whether collagen has been denatured. In other embodiments, the OCT system may be configured to perform optical coherence microscopy using a high numerical aperture for histology or tissue diagnostics. The numerical aperture (NA) refers to the resolving power of a lens. Values of NA that are greater than 1.2 may be considered high. The optical resolution is proportional to λ/(2×NA), where λ is the wavelength of the light. 
     The OCT system may be configured to perform color Doppler coherence tomography to measure tissue perfusion. 
     In one aspect, the present disclosure features a surgical device. The surgical device includes a housing and an end effector assembly operably coupled to the housing. The end effector assembly includes first and second jaw members that each have a tissue contacting surface. At least one of the first and second jaw members is movable between a first, spaced-apart position and a second proximate position. The end effector assembly further includes a sample arm optical assembly of an interferometer coupled to the first jaw member. The sample arm optical assembly transmits a first light beam to tissue grasped between the first and second jaw members and receives at least a portion of the first light beam reflected from the tissue. 
     The end effector assembly also includes a reference mirror of the interferometer coupled to the second jaw member. The end effector assembly further includes a reference arm optical assembly of the interferometer coupled to the second jaw member. The reference arm optical assembly transmits a second light beam to the reference mirror and receives at least a portion of the second light beam reflected from the reference mirror. 
     The sample arm optical assembly may include movable sample arm optics that scan the first light beam across the tissue. The sample arm optical assembly may include a light guide operable to translate and rotate with respect to a longitudinal axis of the first jaw member to scan the tissue. 
     The reference arm optical assembly may translate along a longitudinal axis of the second jaw member. Alternatively, the reference mirror may translate along a longitudinal axis of the second jaw member. 
     The first jaw member may be a top jaw member and the second jaw member may be a bottom jaw member. 
     The surgical device may further include an optical coupler optically coupled to the sample arm optical assembly and the reference arm optical assembly. The optical coupler may provide a first light beam through a first output of the optical coupler to the sample arm optical assembly and may provide a second light beam through a second output of the optical coupler to the reference arm optical assembly. 
     The surgical device may include an imaging light source that generates imaging light. The imaging light source may be optically coupled to an input of the optical coupler. 
     The surgical device may further include a visible light source that generates visible light and a second optical coupler having a first input, a second input, and an output. The first input of the second optical coupler may be optically coupled to the imaging light source and the second input of the second optical coupler may be optically coupled to the visible light source. The second optical coupler may combine the imaging light and the visible light and to transmit the combined light out of the output of the second optical coupler. 
     A portion of the housing of the surgical device may form a handle and the imaging light source and the visible light source may be disposed within the handle. 
     The sample arm optical assembly may include polarization optics to allow for birefringence. Alternatively, the sample arm optical assembly and the reference arm optical assembly may be configured for optical coherence microscopy using a high numerical aperture. 
     In another aspect, the present disclosure features a system for treating tissue. The system includes a surgical device and a processor. The surgical device includes a housing and an end effector assembly operably coupled to the housing. The end effector assembly includes first and second jaw members that each have a tissue contacting surface. At least one of the first and second jaw members is movable between a first, spaced-apart position and a second proximate position. The end effector assembly further includes a sample arm optical assembly of an interferometer coupled to the first jaw member. The sample arm optical assembly transmits a first light beam to tissue grasped between the first and second jaw members and receives at least a portion of the first light beam reflected from the tissue. 
     The end effector assembly also includes a reference mirror of the interferometer coupled to the second jaw member. The end effector assembly further includes a reference arm optical assembly of the interferometer coupled to the second jaw member. The reference arm optical assembly transmits a second light beam to the reference mirror and receives at least a portion of the second light beam reflected from the reference mirror. 
     The end effector assembly further includes a light detector that detects at least a portion of the first light beam reflected from the tissue and at least a portion of the second light beam reflected from the reference mirror and generates a light detection signal. The processor of the system for treating tissue is coupled to the light detector and is configured to process the light detection signal to obtain interference pattern data. The processor may be configured to generate an image signal based on the interference pattern data and to transmit the image signal to a display device. 
     The system may further include an energy source coupled to at least one of the first and second jaw members and a controller coupled to the light detector and the energy source. The energy source delivers energy to the at least one of the first and second jaw members to seal tissue and the controller controls the energy source based on the at least one measured property of the light energy passing through the tissue. At least one of the energy source and the controller may be disposed within the housing. 
     In yet another aspect, the present disclosure features a method of determining properties of tissue in an energy-based medical device. The method includes grasping tissue between first and second jaw members of an energy-based medical device by moving at least one of the first and second jaw members between a first, spaced-apart position and a second proximate position. The method further includes directing a first light beam to the tissue grasped between the first and second jaw members, receiving at least a portion of the first light beam reflected from the tissue, directing a second light beam to a reference mirror, receiving at least a portion of the second light beam reflected from the reference mirror, combining the at least a portion of the first light beam reflected from the tissue and the at least a portion of the second light beam reflected from the reference mirror to form an interference light beam, detecting the interference light beam, and determining at least one tissue property based upon the detected interference light beam. 
     Determining at least one tissue property may include forming an image of the tissue based upon the detected interference light beam. The method may further include controlling the energy applied to the tissue by the energy-based medical device based upon the at least one tissue property. The method may further include determining tissue seal quality, identifying the tissue, or diagnosing the tissue based upon the at least one tissue property. 
     In one aspect, the present disclosure features a surgical device. The surgical device includes a shaft, an end effector assembly operably coupled to the shaft, and a controller. The end effector assembly includes first and second jaw members, each of which has a tissue-contacting surface. At least one of the first and second jaw members is movable between a first, spaced-apart position and a second proximate position. The end effector assembly further includes a tissue-sealing energy source disposed within at least the first jaw member. The tissue-sealing energy source is configured to provide tissue-sealing energy to tissue disposed between the first and second jaw members. 
     The end effector assembly further includes an OCT probe configured to sense properties of tissue disposed between the first and second jaw members. The controller is coupled to the OCT probe and the tissue-sealing energy source so that the controller can control the tissue-sealing energy generated by the tissue-sealing energy source based upon the structural density of the vessel sensed by the OCT probe. 
     The OCT probe may be embedded within the second jaw member. Further, at least a portion of the tissue-contacting surface of the first jaw member may include a transparent optical element that allows light to pass between the OCT probe and the tissue. Still further, the tissue-sealing energy source may generate tissue-sealing light and a reflective element may be disposed on the surface of the transparent optical element to prevent the tissue-sealing light from passing through the transparent optical element. 
     The OCT probe may be rotatably coupled to the second jaw member so that the OCT probe moves between a position parallel to the longitudinal axis of the second jaw member to a position perpendicular to the longitudinal axis of the second jaw member. Alternatively, the OCT probe may be movably coupled to the shaft so that the OCT probe can move out of the shaft between the first and second jaw members. 
     The surgical device may further include a second tissue-sealing energy source disposed within the second jaw member. The second tissue-sealing energy source may be configured to provide tissue-sealing energy to tissue disposed between the first and second jaw members. 
     The tissue-sealing energy source may generate electrical energy or ultrasonic energy. 
     The controller may be configured to operate the OCT probe to sense a tissue property prior to activating the tissue-sealing energy source. The controller may be additionally or alternatively configured to operate the OCT probe to sense a tissue property while operating the tissue-sealing energy source. 
     The OCT probe may sense the structural density of the tissue disposed between the first and second jaw members. The controller may correlate the sensed structural density of the tissue to the amount of collagen contained within the tissue disposed between the first and second jaw members. 
     In another aspect, the present disclosure features a method of sealing tissue. The method includes grasping tissue between first and second jaw members of a surgical device, sensing the structural density of the tissue disposed between the first and second jaw members using an OCT probe, determining parameters for tissue-sealing energy based upon the structural density of the tissue sensed by the OCT probe, and providing the tissue-sealing energy to the tissue based upon the determined parameters of the tissue-sealing energy. 
     The method of sealing tissue may also include inserting the OCT probe in between the first and second jaw members so that the distal end of the OCT probe is close to the tissue after the tissue is grasped between the first and second jaw members. The method may further include retracting the OCT probe from in between the first and second jaw members after the OCT probe completes sensing the structural density of the tissue grasped between the first and second jaw members. 
     The method may include sensing the structural density of the tissue disposed between the first and second jaw members using an OCT probe after providing the tissue-sealing energy to the tissue, and determining the quality of the tissue seal based upon the sensed structural density of the tissue. 
     The method may include rotating the OCT probe from a first position parallel to the longitudinal axis of the second jaw member to a second position perpendicular to the longitudinal axis of the second jaw member prior to activating the OCT probe to sense the structural density of the grasped tissue. 
     The tissue-sealing energy may be electrical energy or ultrasonic energy. The method may include simultaneously operating the OCT probe to sense the structural density of the tissue and to provide tissue-sealing energy to the tissue. The method of sealing tissue may include correlating the sensed structural density of the grasped tissue to the amount of collagen and/or elastin contained within the grasped tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the subject instrument are described herein with reference to the drawings wherein: 
         FIG.  1 A  is a perspective view of an endoscopic forceps having an end effector assembly, which incorporates all or a portion of the components of an OCT system, attached to a distal end of the forceps according to some embodiments of the present disclosure; 
         FIG.  1 B  is a perspective view of a battery-operated endoscopic forceps having an end effector assembly, which incorporates all or a portion of the components of an OCT system, attached to a distal end of the forceps according to another embodiment of the present disclosure; 
         FIG.  2    is a schematic side, cross-sectional view of an end effector assembly incorporating optical components of an OCT system according to embodiments of the present disclosure; 
         FIG.  3    is a schematic diagram of a surgical system incorporating an OCT system according to other embodiments of the present disclosure; 
         FIG.  4    is a schematic diagram of a surgical system incorporating a fiber-optic OCT system according to yet other embodiments of the present disclosure; 
         FIG.  5    is a flow diagram of a method of determining properties of tissue in an energy-based medical device according to embodiments of the present disclosure. 
         FIG.  6    is a schematic diagram of a surgical system according to embodiments of the present disclosure; 
         FIG.  7    is a schematic diagram of a surgical system incorporating a fiber-optic OCT system and a light energy delivery system according to embodiments of the present disclosure; 
         FIGS.  8 A and  8 B  are schematic diagrams of surgical systems incorporating a fiber-optic OCT system and a light energy delivery system according to other embodiments of the present disclosure; 
         FIG.  9    is a schematic diagram of a surgical system incorporating a fiber-optic OCT system and a light energy delivery system according to yet other embodiments of the present disclosure; 
         FIG.  10    is a flow diagram of a method of sealing tissue with an energy-based medical device according to embodiments of the present disclosure; and 
         FIG.  11    is a flow diagram of a method of sealing tissue with an energy-based medical device according to other embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently-disclosed surgical instrument are described in detail with reference to the drawings wherein like reference numerals identify similar or identical elements. 
       FIG.  1 A  shows an endoscopic surgical forceps  10  that incorporates the OCT systems described below. In  FIG.  1 A , forceps  10  is coupled to an energy source (e.g., a generator  40 ) for generating energy, such as electrical energy, ultrasonic energy, or light energy configured to seal tissue. The energy source (e.g., generator  40 ) is configured to output energy having desired characteristics. Forceps  10  is coupled to the generator  40  via a cable  34  that is configured to transmit energy and control signals between the forceps  10  and the generator  40 . Various embodiments of the forceps  10  using various types of energy are described below. 
     Forceps  10  is configured to support an end effector assembly  100 . Forceps  10  includes various conventional features (e.g., a housing  20 , a handle assembly  22 , a trigger assembly  25 , and a rotating assembly  28 ) that enable forceps  10  and end effector assembly  100  to mutually cooperate to grasp, seal, divide, and/or sense tissue. Forceps  10  generally includes a housing  20  and a handle assembly  22  that includes a moveable handle  24  and a handle  26  that is integral with housing  20 . The handle  24  is moveable relative to the handle  26  to actuate end effector assembly  100  via a drive assembly (not shown) to grasp tissue. 
     In some embodiments, trigger assembly  25  may be configured to actuate a knife blade (not shown) or another component to sever tissue after a successful seal. Forceps  10  also includes a shaft  12  having a distal portion  16  that mechanically engages end effector assembly  100  and a proximal portion  14  that mechanically engages housing  20  proximate rotating assembly  28  disposed on housing  20 . Rotating assembly  28  is mechanically associated with shaft  12  such that rotational movement of rotating assembly  28  imparts similar rotational movement to shaft  12  that, in turn, rotates end effector assembly  100 . 
     End effector assembly  100  includes two jaw members  110 ,  120  having proximal ends and distal ends (see  FIG.  1 A ). One or both jaw members  110 ,  120  are pivotable about a pin  19  and one or both jaw members  110 ,  120  are movable from a first position wherein jaw members  110 ,  120  are spaced relative to another, to a second position wherein jaw members  110 ,  120  are closed and cooperate to grasp tissue between the jaw members  110 ,  120 . 
     Each jaw member  110 ,  120  includes a tissue contacting surface disposed on an inner-facing surface thereof (see  FIG.  1 A ). Tissue-contacting surfaces cooperate to grasp and seal tissue held between the tissue-contacting surfaces. Tissue-contacting surfaces are connected to generator  40  that can transmit energy through the tissue held between the tissue-contacting surfaces. 
     First and second switch assemblies  30  and  32  are configured to selectively provide energy to end effector assembly  100 . More particularly, the first switch assembly  30  may be configured to perform a first type of surgical procedure (e.g., seal, cut, and/or sense) and a second switch assembly  32  may be configured to perform a second type of surgical procedure (e.g., seal, cut, and/or sense). It should be noted that the presently-disclosed embodiments may include any number of suitable switch assemblies and are not limited to only switch assemblies  30  and  32 . It should further be noted that the presently-disclosed embodiments may be configured to perform any suitable surgical procedure and are not limited to only sealing, cutting, and sensing. 
     The handle assembly  20  may further include one or more light transmissive elements, such as a cable or optical fibers  34  that connects the forceps  10  to the generator  40 . The cable  34  may include a plurality of optical fibers to transmit light through various paths and ultimately to the OCT system incorporated into the end effector assembly  100 , which is described in further detail below. 
     First and second switch assemblies  30  and  32  may also cooperate with a controller  42 , which may be implemented by a logic circuit, a computer, a processor, and/or a field programmable gate array. The controller  42  may automatically trigger one of the switches to change between a first mode (e.g., sealing mode) and a second mode (e.g., cutting mode) upon the detection of one or more parameters or thresholds. In some embodiments, the controller  42  is also configured to receive various sensor feedback and to control the generator  40  based on the sensor feedback. The embodiments of the present disclosure allow the jaw members  110 ,  120  to seal and/or cut tissue using any suitable form of energy. 
     In some embodiments, the controller  42  may include a feedback loop that indicates when a tissue seal is complete based upon one or more of the following parameters: tissue temperature, optical sensing, change in impedance of the tissue over time and/or changes in the optical or electrical power or current applied to the tissue over time, rate of change of these properties and combinations thereof. An audible or visual feedback monitor may be employed to convey information to the surgeon regarding the overall seal quality or the completion of an effective tissue seal. 
     Referring now to  FIG.  1 B , forceps  11  is shown having a portable configuration and includes an internal generator  50  for generating energy that is operably coupled to a battery compartment  52  via one or more wires  50   a . In some embodiments, one or more battery operated laser diodes or fiber lasers may also be used to provide a portable light energy source. The internal generator  50  may be configured to provide energy to the end effector assembly  100 . The battery compartment  52  may be configured to receive one or more batteries  54  for providing suitable energy to internal generator  50 . In embodiments, the controller  42  may also be disposed within the forceps  11  (e.g., the housing  20 ). 
     Battery compartment  52  may be defined within any suitable portion of housing  20  of forceps  11 , such as the fixed handle  26 , as shown in  FIG.  1 B . Suitable batteries may include, but are not limited to a nickel-cadmium, lithium-ion, rechargeable, or any other suitable type. The location of internal generator  50  provides an operator increased maneuverability and convenience when performing a surgical treatment with forceps  11 . 
       FIG.  2    illustrates an end effector assembly  100  according to some embodiments of the present disclosure, which is configured for use with either surgical instrument  10  or surgical instrument  11  described above or any other suitable surgical instruments. However, for purposes of simplicity and consistency, end effector assembly  100  is described below with reference to instrument  10 . 
     The end effector assembly  100  includes a first jaw member  110  that incorporates a free-space OCT system  200 . The OCT system  200  includes a light source  202 , a beamsplitter  204 , a reference mirror  206 , and a light detector  208 . The light source  202  is electrically coupled to the generator  40  to receive power and/or command signals from the generator  40 . The light detector  208  is electrically coupled the generator  40  to provide light detection signals to the generator  40  and to receive power from the generator  40 . 
     In operation, the light source  202  (e.g., a monochromatic light source) emits a source beam  212  toward the beamsplitter  204 , which is positioned diagonally with respect to the source beam  212 . The beamsplitter  204  splits the source beam  212  into two halves: a first beam  214  and a second beam  216 . The first beam  214  is transmitted through the beamsplitter  204  and then is reflected back from the tissue  205  towards the beamsplitter  204 . The second beam  216  is reflected off the beamsplitter  204  and then is reflected back towards the beamsplitter  204  by the reference mirror  206 . The back-reflected first beam  214  and the back-reflected second beam  216  are recombined by the beamsplitter  204  into a recombined beam  218  that is detected by the light detector  208 . The light detector  208  then transmits an electrical signal representing the detected recombined beam  218  to the generator  40 , which detects an interference pattern based on the electrical signal and displays an image of the tissue  205  based on the detected interference pattern. 
       FIG.  3    is a schematic diagram of a surgical system  300  incorporating an OCT system having an optical assembly  305  and an electrical assembly  310 . As shown, the surgical system  300  includes an end effector assembly  301  that incorporates the optical assembly  305  and the electrical assembly  310 . The configuration of the optical assembly  305  is similar to the configuration of the optics in  FIG.  2   , except that the reference mirror  206  is disposed on a movable element  302  that can move the reference mirror  206  along a horizontal axis  304  to perform scanning of the tissue. 
       FIG.  3    also illustrates the electrical assembly  310  of the OCT system that receives the interference signal generated by the light detector  208 . The electrical assembly  310  may be disposed in the generator of  FIG.  1   . The electrical assembly  310  includes an amplifier  312 , a demodulator  314 , and an analog-to-digital converter (ADC)  316 . The amplifier  312  amplifies the light detector signals and the demodulator  314  demodulates the amplified signals as the reference mirror  206  is moved along a horizontal axis  304 . The demodulator  314  provides scan signals to the ADC  316 , which converts the scan signals into digital scan data. The digital scan data are then provided to a computer system  320  that generates an image that is displayed on the display of the computer system  320 . In addition or in the alternative, the computer system  320  may analyze the digital scan data to identify the tissue, to determine the status of the tissue being sealed, or to determine that quality of a tissue seal. 
     In some embodiments, the computer system  320  may be incorporated into the forceps  11  of  FIG.  1 B . For example, the processor of the computer system  320  may be incorporated into the internal generator  50  of the forceps  11  and a display of the computer system  320  may be disposed on the housing  20  of the forceps  11 . 
       FIG.  4    is a schematic diagram of a surgical system  400  incorporating a fiber-optic OCT system. A first portion  445   a  of the fiber-optic OCT system is incorporated into the jaw members  110 ,  120  of the end-effector assembly  440 . The first portion  445   a  of the fiber-optic OCT system includes a sample arm  410 , which is incorporated into the first jaw member  110 , and a reference arm  420 , which is incorporated into the second jaw member  120 . Alternatively, the reference arm  420  may be incorporated into the generator  40  of  FIG.  1 A . 
     A second portion  445   b  of the fiber-optic OCT system is disposed outside of the end-effector assembly  440 . In some embodiments, the second portion  445   b  of the fiber-optic OCT system is disposed in the generator  40  of  FIG.  1 A . In other embodiments, the second portion  445   b  of the fiber-optic OCT system is disposed in the internal generator  50  of  FIG.  1 B . 
     As shown in  FIG.  4   , the second portion  445   b  of the fiber-optic OCT system includes two light sources: an imaging light source  402  and a visible light source  404 . The imaging light source  402  may be a broadband source (e.g., a broadband, near-infrared source) that generates an imaging beam to image tissue. Examples of broadband sources include super-luminescent diodes, fiber amplifiers, and femto-second pulse lasers that generate light having a wavelength that ranges between 800 and 1550 nanometers. The visible light source  404  generates a visible aiming beam. The outputs of the imaging light source  402  and the visible light source  404  are optically coupled to a 2×1 optical coupler  406 , which combines the imaging light beam with the visible light beam so that a user can see the imaging light beam. 
     The light output from the 2×1 optical-fiber coupler  406  is coupled into optical fiber  401  of the fiber-optic interferometer. The light is split into two optical fibers—a reference arm optical fiber  403  and a sample arm optical fiber  405 —using a 2×2 optical-fiber coupler  408 . The reference arm optical fiber  403  is optically coupled to reference arm optics  420 . The reference arm optics  420  includes a lens  422 , such as a convex lens, and a reference mirror  424 . The lens  422  forms a light beam from the light emitted from the reference arm optical fiber  403  and directs it to the reference mirror  424 . The light reflects off the reference mirror  424  and travels back towards the optical-fiber coupler  408  through the lens  422  and the reference arm optical fiber  403 . 
     A sample arm optical fiber  405  is coupled to the sample arm optics  410 , which transmits light to the tissue  205 . The light is reflected from the tissue  205  back into the sample arm optical fiber  405 . The light is reflected from the tissue as a result of changes in the index of refraction within the structure of the tissue, e.g., between intercellular fluid and collagen fibers. The light reflected back from the tissue  205  and the light reflected back from the reference mirror  424  are recombined within the 2×2 fiber-optical coupler  408 . 
     Because of the short coherence length of the broadband light source  402 , the light reflected from the tissue and the light reflected from the reference mirror  424  will interfere constructively and destructively only if the optical path lengths of the sample arm  410  and the reference arm  420  are matched. By changing the length of the reference arm, the tissue can be sampled at various depths. 
     The light recombined by the 2×2 fiber-optical coupler  408  is provided to the optical detector  208 , e.g., a photodiode via optical fiber  407 . The optical detector  208  detects the interference between the light reflected from the tissue and the light reflected from the reference mirror  424 . During OCT imaging, the reference mirror  424  is scanned along the longitudinal axis  425  A-A of the second jaw member  120  at a constant velocity, thus allowing depth scans of the tissue (analogous to ultrasound A-scans). 
     The sample arm optics  410  may be configured to perform lateral scans across the tissue to construct two- and three-dimensional images. In the embodiment shown in  FIG.  4   , the sample arm mirror  414  may be rotatable  415  about a transverse axis B-B of the first jaw member  110  to scan the tissue  205  along the longitudinal axis of the first jaw member  110 . The detected interference signals from this scan are then used to construct a two-dimensional cross-sectional image of the tissue  205 . 
     The optical detector  208  then transmits the detected interference signal to a processor  430 , which forms an image of the tissue based on the detected interference signal. The image is then displayed on a computer display  320 . 
     The surgical systems according to embodiments of the present disclosure may generate images of a region of tissue so that a surgeon can determine the status of the tissue after a sealing procedure. For example, the surgeon can use the generated images to verify whether or not the tissue has been sealed or to determine whether or not the tissue has been properly sealed. 
       FIG.  5    is a flow diagram of a method for determining properties of tissue in an energy-based medical device according to embodiments of the present disclosure. After starting in step  501 , tissue is grasped between first and second jaw members of an energy-based medical device in step  502 . In step  504 , a first light beam is directed to the tissue grasped between the first and second jaw members and, in step  506 , at least a portion of the first light beam reflected from the tissue is received, e.g., by a light detector. In step  508 , a second light beam is directed to a reference mirror, and, in step  510 , at least a portion of the second light beam reflected from the reference mirror is received, e.g., by the light detector. 
     In step  512 , at least a portion of the first light beam reflected from the tissue and at least a portion of the second light beam reflected from the reference mirror are combined to form an interference light beam. Finally, before ending in step  517 , the interference light beam is detected in step  514  and one or more tissue properties are determined based upon the detected interference light beam in step  516 . The tissue properties may include tissue type, cell type, disease state, or disease pathology. 
     As described herein, the energy-based medical devices may have an OCT probe embedded within the jaw members or the OCT probe may a retractable probe that is deployed from the shaft of the medical device. In these configurations, the OCT imaging may be performed prior to energy delivery when the jaw members clamp onto unsealed tissue, to determine the structural density of the tissue. The structural density information would then be relayed to a controller to adjust the temperature and/or energy to perform a tissue seal. The OCT imaging may also be performed after performing a tissue sealing procedure so that the clinician can determine the success and/or quality of the tissue seal. This type of imaging/sealing medical device would be beneficial when sealing large vessels and thick tissue masses. 
     The OCT imaging may be used in combination with any type of energy-based medical device including medical devices that treat tissue using light energy, radio frequency energy, or ultrasound energy. 
       FIG.  6    is a schematic diagram of surgical system  600  that incorporates an OCT probe. The surgical system  600  includes a controller  601 , a memory  602 , a display  603 , an OCT system  610 , and a generator or energy source  620 . The controller  601  is electrically connected to the energy source  620  to control the energy output from the energy source  620 . The energy source  620  may output light energy, electrical energy, or ultrasonic energy. The controller  601  controls the amount of energy output from the energy source  620  to achieve a desired tissue effect. For example, in the case that the energy source  620  is a light energy source, the controller  601  controls the intensity and/or other properties of the light energy, e.g., polarization, to seal tissue that is placed between the jaws of a surgical device. 
     According to the present disclosure, the controller  601  is electrically connected to the OCT system  610  to receive optical feedback information, which is used by the controller  601  to adjust the properties of the energy output from the energy source  620 . The optical feedback information includes images that indicate the structural density and/or other properties of the tissue that is placed between the jaws of a surgical instrument. As described herein, all or a portion of the surgical system  600  may be incorporated into a surgical instrument. For a portable surgical instrument, all of the components of the surgical system  600  may be incorporated into the surgical instrument. 
     The controller  601 , which may be a processor, a digital signal processor, a central processing unit (CPU), or microprocessor, is coupled to the memory  602 , which may be a non-volatile memory such as ROM or NVRAM. The controller  601  may retrieve instructions from the memory  602  and may execute the instructions to control the energy source  620  based on feedback from the OCT system  610 . 
     The OCT system  610  may be coupled to a display  603  that displays images of the tissue obtained by the OCT system  610 . The display  603  may allow for an operating mode in which a user may manually adjust the amount of energy output from the energy source  610  as the user views the display  603 . 
     According to the present disclosure, the OCT probe may be embedded in a jaw member of a tissue-sealing surgical device, e.g., an optical vessel sealer, which allows for imaging of tissue to be performed before and after the tissue seal without device reconfiguration. The jaw member may include a transparent window disposed at or near the tissue-contacting surface of the jaw member to allow for imaging of tissue disposed between the jaw members of the tissue-sealing surgical device. 
       FIG.  7    is a schematic diagram of a surgical system incorporating a fiber-optic OCT probe  710  and a light-energy delivery system  720 . The fiber-optic OCT probe  710  is incorporated into the first jaw member  110  and the light-energy delivery system  820  is incorporated into the second jaw member  120 . The fiber-optic OCT probe  710  incorporates similar components as the fiber-optic OCT system shown in  FIG.  4   . The fiber-optic OCT probe  710  includes a sample arm  410  and a reference arm  420  and an optical coupler  408 . The OCT probe  710  may be optically coupled to the remaining components of an OCT system, which are illustrated above in  FIG.  4   . 
     The light-energy delivery system  720  includes a light source  721 , an optical fiber or other light waveguide  722 , and a light distribution element  723 . The light source  721  generates light having an appropriate intensity and wavelength for sealing or otherwise treating tissue disposed between the jaw members  110  and  120 . The optical fiber  722  carries the light generated by the light source  721  to the light distribution element  723 , which forms and distributes a light beam perpendicular to or substantially perpendicular to the tissue-contacting surface of the second jaw member  120 . 
     A method of using the surgical system of  FIG.  7    may include grasping tissue between the first and second jaw members  110  and  120 , sensing optical properties of the tissue using the OCT probe  710 , and delivering light to tissue using the light-energy delivery system  720  based on the sensed optical properties of the tissue. 
     Vessels containing large and small amounts of collagen show differences in structural density. Specifically, vessels with large collagen content have greater structural density than vessels with low collagen content. Thus, OCT may be used to detect the structural density of vessels, which may then be correlated to collagen content. 
     Preliminary testing has shown that vessels with a large amount of collagen content (e.g., the carotid artery) are more consistently sealed than vessels with low collagen content (e.g., the femoral artery). Since collagen has a lower denaturation temperature than elastin, tissues with higher collagen content may form seals at lower temperatures. Thus, OCT may be used to determine the collagen or elastin content of tissue, and the amount of energy delivered to the tissue may be controlled based on the collagen or elastin contents of the tissue. 
     For example, OCT may be used to determine the amount of collagen and/or elastin in a vessel disposed between the jaw members  110  and  120 . If the OCT probe  710  senses a large amount of collagen in the vessel, then the light-energy delivery system  720  may deliver less energy to the vessel as compared to another vessel having a smaller amount of collagen because collagen has a lower denaturation temperature. 
     The tissue-contacting surface  220  of the first jaw member  110  may be coated with a reflective layer  715  adjacent the light output of the sample arm  410  of the fiber-optic OCT probe  710  so that the light beam from the light-energy delivery system  720  does not damage the components of the fiber-optic OCT probe  710 . 
     In another mode of operation, the OCT probe  710  and the light-energy delivery system  720  may be operated simultaneously. In other words, the OCT probe  710  may sense optical properties of the tissue while the light-energy delivery system  720  is delivering light to the tissue. In this mode of operation, a controller (not shown) coupled to the light-energy delivery system  720  may control the intensity of the light produced by the light-energy delivery system  720 . 
       FIGS.  8 A and  8 B  are schematic diagrams of a surgical system incorporating light-energy delivery systems  720  into both the first and second jaw members  110  and  120 . Specifically, each of the first and second jaw members  110  and  120  includes a light source  721 , an optical fiber or waveguide  722 , and a light distribution element  723 . The OCT probe  710  is movably coupled to the surgical device so that it can be inserted into and remove from between the first and second jaw members  110  and  120 . 
     In an example mode of operation, tissue is grasped between the first and second jaw members  110  and  120  of a surgical device. Next, the OCT probe  710  is inserted  802  in between the first and second jaw members  110  and  120  so that the distal end of the OCT probe  710  is disposed adjacent to the tissue. Then, the OCT probe is operated to sense the properties of the tissue disposed between the first and second jaw members. A controller (not shown) coupled to the OCT probe  710  may determine parameters for light energy based upon the properties of the tissue sensed by the OCT probe  710 . 
     Next, as illustrated in  FIG.  8 B , the OCT probe  710  is removed  804  from in between the first and second jaw members  110  and  120 . Then, the controller (not shown) may operate the light-energy delivery systems  720  according to the determined parameters for the light energy. The controller may operate the light-energy delivery systems  720  so that they simultaneously and/or alternatively deliver light to the tissue. 
     In other embodiments, the light energy delivery systems  723  may be replaced by other energy delivery systems such as ultrasonic or electrical energy delivery systems. These alternative energy delivery systems may be operated in the same manner as described above with respect to the light energy delivery systems  720 . 
       FIG.  9    is a schematic diagram of a surgical system incorporating the light energy delivery system  720  and a rotatable OCT probe  710 . As shown in  FIG.  9   , the OCT probe  710  is rotatable  910  about the pin  901  from a first position  902  to a second position  904 . The first position  902  may be a position at which the OCT probe  710  is not used and the second position  904  may be a position at which the OCT probe  710  is operated to sense properties of the tissue disposed between the jaw members  110  and  120 . 
     Thus, according to one method of operation, the first and second jaw members  110  and  120  are operated to grasp tissue  205  and the OCT probe  710  is rotated from the first position  902  to the second position  904 . Then, the OCT probe  710  is operated to sense properties of the tissue  205 . After the OCT probe  710  senses the properties of the tissue  205 , the OCT probe  710  may be rotated back to the first position  902  before the light-energy delivery system  720  delivers light to the tissue  205 . Alternatively, the OCT probe  710  may remain in the second position  904  while the light-energy delivery system  720  delivers light to the tissue  205 . Then, the light-energy delivery system  720  delivers light to the tissue  205 . 
       FIG.  10    is a flow diagram of a method of sealing tissue using an energy-based surgical device. After starting in step  1001 , tissue is grasped between the first and second jaw members of the surgical device in step  1002 . In step  1004 , the properties of the tissue disposed between the first and second jaw members are sensed using an OCT probe. The sensed properties of the tissue may include the structural density or structural profile of the tissue. 
     In step  1006 , parameters of tissue-sealing energy are determined based upon the properties of the tissue sensed by the OCT probe. These parameters may include power, voltage, and/or current in the case of electrosurgical and ultrasonic surgical devices. In the case of light-based surgical devices, the parameters may include intensity, frequency, wavelength, and/or polarization. The parameters may also include temperature. 
     For example, if the OCT probe senses a high structural density of vascular tissue disposed between the first and second jaw members, which indicates a large concentration of collagen within the vascular tissue, the intensity and wavelength of a light beam generated by a light-based surgical instrument may be controlled so that a sufficient amount of light energy is provided to the vascular tissue to denature the collagen within the vascular tissue. 
     Before the method ends in step  1009 , tissue-sealing energy having the determined parameters is generated and applied to the tissue. 
       FIG.  11    is a flow diagram of another method of sealing tissue using an energy-based surgical device. After starting, in step  1102 , an OCT probe is inserted between first and second jaw members of a surgical device near tissue disposed between the first and second jaw members, in step  1104 . In step  1106 , the structural density of the tissue disposed between the first and second jaw members are measured using the OCT probe. In step  1108 , parameters for tissue-sealing energy to be applied to the tissue are determined based upon the structural density of the tissue measured in step  1106 . 
     After determining the parameters for the tissue-sealing energy to be applied to the tissue in step  1108 , the OCT probe is removed from between the first and second jaw member in step  1110  so that the probe is not exposed the tissue-sealing energy. Then, before the method ends in step  1114 , tissue-sealing energy having the determined parameters is generated and applied to the tissue. 
     The OCT systems described above may be modified to monitor different properties of tissue. For example, the sample arm optics  410  and the reference arm optics  420  of the OCT system could incorporate polarization-altering optics (e.g., polarized lenses, plates, or windows) to determine the tissue birefringence based upon the magnitude of the back-reflected light. 
     The OCT systems may be configured to perform optical coherence microscopy for histology or tissue diagnostics. The OCT system may incorporate optical elements to achieve resolutions comparable to confocal microscopy but with increased depth of penetration. For example, the OCT system may incorporate optical elements having a high numerical aperture (e.g., the lens  416  may have a high numerical aperture) to achieve high resolutions and a large penetration depth. 
     The surgical systems of the present disclosure (e.g., the surgical system  400  of  FIG.  4   ) may incorporate mechanisms for selectively applying different optical elements to achieve different optical effects. In some embodiments, the surgical system  400  may include a mechanism that switches between a standard optical element (e.g., the lens  416 ) and an optical element having a high numerical aperture. In other embodiments, a polarization-altering optical element may be inserted in series with the standard optical element (e.g., the lens  416 ). 
     In other embodiments, the OCT systems may be configured to perform color Doppler optical coherence tomography (CDOCT) to measure tissue perfusion, i.e., the amount of blood that flows through tissue. 
     While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.