Abstract:
A probe for detecting changes in tissue properties comprising an illumination element providing light to a target area and a sensing element receiving light from the illumination element after reflection from a target portion of tissue in combination with a device that detects changes in a property of the light received by the sensing element and determining, based on the detected changes in the property of the received light, a change in the target tissue.

Description:
BACKGROUND  
       [0001]     Heat is often used to treat tissue, e.g., connective tissues, tumors, fibroids, etc. In such procedures, thermal energy is delivered to a target tissue mass to, for example, shrink or necrose the tissue.  
         [0002]     However, many current systems provide little to no feedback on the progress of the thermal treatment. Those systems which do monitor the progress of such treatments are often unable to account for parameters which affect the degree of treatment of tissue and ultrasound imaging systems which are used to monitor necrosis are not universally effective or consistent with all thermal energy sources. In addition, such systems often require specific expertise and/or elaborate equipment. Thus, it is difficult for physicians to accurately determine when a desired degree of treatment of a target tissue mass has been achieved.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention is directed to a probe for detecting changes in tissue properties comprising an illumination element providing light to a target area and a sensing element receiving light from the illumination element after reflection from a target portion of tissue in combination with a device that detects changes in a property of the light received by the sensing element and determining, based on the detected changes in the property of the received light, a change in the target tissue. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  shows an exemplary embodiment of a system, according to the present invention, comprising a spectral reflectance probe in conjunction with a tissue treatment device and a laparoscope;  
         [0005]      FIG. 2  shows an experimental bench test set-up for determining feasibility of detecting sub-surface tissue changes using spectral reflectance;  
         [0006]      FIG. 3  shows an ultrasound probe feasibility working model comprising illumination and sensing fibers;  
         [0007]      FIG. 4  shows a schematic of a system according to an alternative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0008]     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The invention relates to a system using a feedback device in conjunction with a device for thermal treatment of tissue. More specifically, the invention relates to a system using a spectral reflectance probe that detects sub-surface tissue changes to determine an extent of the tissue treatment.  
         [0009]     The system according to an embodiment of the present invention comprises a first elongated member with a treatment device and a second elongated member with a spectral reflectance probe. The two elongated members may be connectable to each other, or the two members may be completely independent. If coupled, the two elongated preferably members remain slidable relative to one another. The treatment device delivers energy to the tissue mass targeted for treatment. The spectral reflectance probe includes an illumination fiber and a sensing fiber. The illumination fiber delivers white light, or one or more specific wavelengths of light, from the distal tip of the probe, and the sensing fiber detects the light reflected from the tissue. In addition, the system may comprise a third elongated member with a laparoscope or other vision device to observe the procedure.  
         [0010]     In preparation for tissue treatment, a trocar is inserted to the tissue treatment location and the treatment device and spectral reflectance probe are inserted through the trocar to the target tissue mass. Alternatively, the treatment device and spectral reflectance probe may be inserted to the target tissue mass through separate trocars. The tip of the treatment device is positioned at a desired location within the target tissue mass and the tip of the spectral reflectance probe is preferably positioned outside the target tissue mass so that the illumination fiber delivers light to an outer surface of the target tissue mass with the sensing fiber detecting light reflected from the tissue to establish a baseline reflectance signal. In addition, a laparoscope or other vision device may be inserted through an additional trocar to observe the procedure. Alternatively, the treatment device and spectral reflectance probe may be inserted to the target tissue directly through the skin without the use of a trocar.  
         [0011]     During tissue treatment, the zone of treated (coagulated) tissue grows and, as an advance edge of the treated tissue expands and approaches the surface of the target tissue mass, the qualities of the light reflected from the tissue alter. Thus, these changes may be monitored by analyzing the light received by the sensing fiber and the data is conveyed to a user of the system indicating the detected change in tissue properties. Reflectance changes at one or more wavelengths may be monitored during the course of the treatment to determine when a desired level of treatment has been completed. Those skilled in the art will understand that spectral reflectance may be used in the same manner to detect changes in tissue resulting from other types of treatments including cryogenic and chemical ablations. A suitable method of detecting tissue changes is disclosed in U.S. Pat. No. 5,071,417 entitled Laser Fusion of Biological Materials, the entire disclosure of which is hereby incorporated by reference.  
         [0012]     The ability of the spectral reflectance probe to detect tissue changes below the surface of the target tissue mass depends upon the light penetrability of the tissue mass and the depth of the tissue below the surface of the tissue mass. The illumination fiber preferably delivers a wavelength of light selected based on the tissue properties with. Wavelengths of light with deeper tissue penetrations such as, for example, 600 to 900 nm, or more preferably, 635 to 780 nm, are preferred with wavelengths such as 635, 730 and 780 nm which are commercially available being more preferable as water absorption would be reduced. As would be understood by those skilled in the art, wavelengths which penetrate more shallowly (e.g., to a depth of less than 1 cm)—i.e., wavelengths above 905 or 940 nm—may unesirably heat and damage tissue.  
         [0013]      FIG. 1  shows an exemplary embodiment of a system, according to the present invention, comprising a spectral reflectance probe  20  in conjunction with a tissue treatment device  10  and a laparoscope  22 . The tissue treatment device  10  which, in this embodiment is an interstitial probe including an electrode for delivering RF energy to tissue, is inserted through the skin  12  via a trocar  14 . Those skilled in the art will understand that the system according to the invention will work equally well with other tissue treatment devices including ultrasound, laser, microwave, cryogenic and chemical ablation systems, etc. The tip of the treatment device  10  is inserted within a target tissue mass  16  (e.g., near a center thereof) within an organ  18  and the spectral reflectance probe  20  is inserted alongside the treatment device  10  until a distal tip  21  of the probe  20  is positioned adjacent to an external surface of the target tissue mass  16 . Further, to observe the procedure and to facilitate the insertion of the treatment device  10  and spectral reflectance probe  20  to their desired locations, a laparoscope  22  may be inserted through the skin  12  using an additional trocar  14  as would be understood by those skilled in the art. Those skilled in the art will understand that certain types of treatment devices (e.g., certain ultrasound heating devices) do not need to be inserted into the center of a target tissue mass. For example, a device may focus ultrasound energy from a plurality of ultrasound crystals on a spot separated from the device to heat tissue at a distance. Those skilled in the art will understand that, depending on the distance from the device to the focus area and the size of the target tissue mass  16 , such a device may be positioned adjacent the surface  17 , within the tissue mass  16  but away from the center or outside the target tissue mass  16  separated from the surface  17 . Such a device is described in a U.S. Patent Application entitled, “Apparatus and Method for Stiffening Tissue” filed Mar. 29, 2005 naming Isaac Ostrovsky, Michael Madden, Jon T. McIntyre and Jozef Slanda as inventors, the entire disclosure of which is hereby expressly incorporated by reference herein.  
         [0014]     Before the treatment is begun, an illumination element  23  of the spectral reflectance probe  22  is actuated to illuminate the external surface  17  of the target tissue mass  16  and a sensing element  25  receives light reflected from the external surface  17  and transmits the light to a sensor such as a spectrometer or silicon photodetector which converts the light to an electric signal representative thereof. This electric signal is then transmitted to a controller  36  which analyzes the signal to establish a base line reflectance level for the target tissue mass  16 . Once this value has been established, treatment is begun by energizing the treatment device  10  to deliver thermal energy to the center of the target tissue mass  16 . As the thermal energy gradually treats the tissue mass  16  a treated portion of the tissue mass  16  expands and a leading edge of this treated portion of tissue approaches the surface  17  of the tissue mass  16 . As this leading edge moves toward the surface  17 , the illumination element  23  constantly or intermittently illuminates the surface  17  and the controller  36  analyzes reflectance changes of the light received by the sensing element  25  to determine the position of the leading edge relative to the surface  17 . Feedback is provided to a user of the system to indicate the progress of the treatment. That is, changes in the properties of specific wavelength bands of the reflected light will indicate a degree of necrosis. For example, a spectrometer or other sensor may be used to identify the intensities of various frequency ranges of light to generate a ratio of these intensities to intensities measured before treatment was initiated to determine a rate and/or amount of change corresponding to the coagulation or necrosis of the target tissue.  
         [0015]     Additionally,  FIG. 1  shows the distal tip  21  of the spectral reflectance probe  20  positioned adjacent to the surface  17  of the target tissue mass  16 . Although this configuration may be preferable for certain applications such as uterine fibroids, for other applications such as cancerous tumors, the tip  21  of the probe  20  is preferably separated from the surface  17  of the target tissue mass  16  by a short distance (e.g., 1 to 2 cm) to allow treatment and spectral reflectance monitoring to continue through the outer surface  17  to encompass a desired margin of healthy tissue surrounding the target tissue mass  16 .  
         [0016]     In cases where a previous assessment of the size of a target tissue mass  16  has been made, the use of a spectral reflectance probe  20  according to the present invention does not add any significant steps to the procedure. For example, where symptoms indicative of uterine fibroids are present, a diagnostic ultrasound is generally performed to confirm the presence of the fibroids and to determine their location and size. When the fibroids are to be treated, the treatment device  10  and a spectral reflectance probe  20  are inserted into the body side by side and the treatment device  10  is further advanced to center of the fibroid while the spectral reflectance probe  20  is positioned adjacent to an outer surface of the fibroid with the illumination element  23  and the sensing element  25  thereof facing the fibroid.  
         [0017]     According to an embodiment of the invention, the spectral reflectance probe  20  and the treatment device  10  are slidably coupled to one another to form a single device for treating tissue and monitoring the treatment. Further, the spectral reflectance probe  20  may be incorporated as part of a disposable tissue treatment device  10 .  
         [0018]     As shown in  FIG. 2 , target tissue  16  is located between an ultrasound probe  26  according to a further embodiment of the invention and a spectral reflectance probe  20 . As described above, this probe  26  may be located within the target tissue  16  or at any point outside the tissue  16  which will allow the probe  26  to treat the target tissue  16 . As with the above described embodiments, the probe  26  may be movably coupled to the spectral reflectance probe  20  in any desired manner and, depending on the qualities of the probes  20  and  26 , may be rigidly coupled to one another so that a distance separating the probe  20  from the surface  17  is fixed relative to the location of the probe  26 . According to this embodiment, the illumination element  23  of the spectral reflectance probe  20  includes a 20 milliwatt laser producing light of 635 nm wavelength. However, as would be understood by those skilled in the art, other wavelengths may be used to achieve a desired depth of tissue penetration although wavelengths below a range of 940 nm are preferable to minimize water absorption with wavelengths below 905 nm being more preferable. Below these values there are many commercially available wavelengths that may be used. In addition, the illumination element  23  includes an illumination fiber  28  which, in this embodiment is a 400 micron optic fiber while the sensing element  25  includes a sensing fiber  30  which in this embodiment is a 600 micron optical fiber. A spectral reflectance probe  20  constructed as described herein detects tissue changes at depths ranging from 0 to approximately 20 mm. Furthermore, the probing wavelength may be changed to enhance results for different tissue depths and may be altered during the procedure to adjust for the changing depth of the leading edge of the treated tissue. Those skilled in the art will understand that the components of the illumination element  23  and the sensing element  25  may be varied to suit the design requirements of the probe  20  and its intended use, etc. Furthermore, the details of the construction of the sensing probe  20  in regard to any of the disclosed embodiments may be rearranged in any manner as the probe  20  will operate in the same manner regardless of the type of treatment device with which it is used.  
         [0019]      FIG. 4  shows a schematic of a non-invasive system  40  according to the present invention, comprising a generator  32 , a light source  34  (e.g., a laser), and a controller  36  coupled to an integrated ultrasound probe  26  as described above comprising an illumination fiber  28  and a sensing fiber  30 . Those skilled in the art will understand that the system  40  ablates tissue provides real time feedback on the degree of ablation without penetrating the target tissue mass  16 . The generator  32  delivers energy to the ultrasound probe  26  for treatment of the target tissue mass  16 . The light source  34  provides illumination of the target tissue mass  16  via the illumination fiber  28  and the controller  36  receives and analyzes spectral reflectance data transmitted thereto from the probe  20  via the sensing fiber  30 . Thus, the illumination and sensing fibers  28 ,  30 , respectively, for detecting spectral reflectance are integrated into a single ultrasound probe  26  for simultaneous tissue treatment and detection of spectral reflectance.  
         [0020]     As would be understood by those skilled in the art, the generator  32  delivers energy to the ultrasound probe  26  to stimulate vibration of one or more crystals (not shown) of the ultrasound probe  26  to treat a target tissue mass  16 . Simultaneously, the light source  34  delivers light to the surface of the target tissue mass  16  through the illumination fiber  28 , either continuously or at desired intervals, while the controller  36  receives reflectance changes of the target tissue mass  16  through the sensing fiber  30 . The controller  36  may optionally analyze reflectance changes of the tissue mass  16  and control, via the feedback loop  38 , energy delivery by the generator  32 . Thus, the system  40  may regulate and ultimately terminate tissue treatment based on reflectance changes of the target tissue mass  16  automatically reducing or eliminating the potential for user errors and reducing the actions required of the user.  
         [0021]     The exemplary embodiment described above in conjunction with  FIG. 1 , uses radio frequency energy as the tissue treatment thermal energy source. However, the system of the present invention using spectral reflectance may be used with many other tissue treatment thermal energy sources, including but not limited to microwave and laser energy. In addition, the exemplary embodiments described above have discussed treatment of cancerous tumors and uterine fibroids. Other potential applications for the spectral reflectance probe of the present invention include, but are not limited to, prostate cancer, benign prostatic hypertrophy (BPH).  
         [0022]     The embodiment described in regard to  FIG. 4  is particularly suited for the treatment of stress urinary incontinence via transvaginal delivery of ultrasound energy to create subsurface tissue effects without penetrating the surface. Other potential applications for this embodiment include, among others, gastroesophageal reflux disease (GERD), fecal incontinence, joint conditions such as rotator cuff injuries, and cosmetic applications such as treating wrinkles.  
         [0023]     The present invention has been described with reference to specific embodiments, and more specifically, with reference to a system comprising a spectral reflectance probe for use during tissue treatment. However, other embodiments may be devised that are applicable to other devices and procedures, without departing from the scope of the invention. For example, the sensing element may include any electronic imaging device sending electrical signals directly to the controller. Accordingly, various modifications and changes may be made to the embodiments, without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.