Abstract:
An apparatus comprises a snare and an actuator. The snare is formed of a material having an opacity complementary to a predetermined imaging system that is positionable external to a patient. The actuator is configured to steer the snare in response to an image of at least a portion of a colon of the patient. The image is generated by the predetermined imaging system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 60/893,917, entitled “Steerable Snare for Use in the Colon and Method for the Same,” filed Mar. 9, 2007; which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The invention relates generally to medical devices for use in conjunction with a virtual colonoscopy procedure, and more particularly, to methods for thermally treating undesirable growths. 
         [0003]    Colorectal cancer is one of the leading causes of deaths from malignancy in the United States, with only lung cancer causing more deaths annually. Colon cancer can be prevented because it usually begins as a benign polyp that grows slowly for several years before becoming cancerous. If polyps are detected and removed, the risk of developing colon cancer is significantly reduced. 
         [0004]    Unfortunately, widespread colorectal screening and preventive efforts are hampered by several practical impediments, including limited resources, methodologic inadequacies, and poor patient acceptance leading to poor compliance. Moreover, some tests, such as the fecal occult blood test (FOBT) fail to detect the majority of cancers and pre-cancerous polyps. Additionally, since a sigmoidoscopy only examines a portion of the colon, it also misses many polyps that occur in the remainder of the colon. The accuracy of other tests, such as the barium enema, vary and are not always reliable. 
         [0005]    A technique for detecting colorectal cancer using helical computed tomography (CT) to create computer simulated intraluminal flights through the colon was proposed as a novel approach for detecting colorectal neoplasms by Vining D J, Shifrin R Y, Grishaw E K, Liu K, Gelfand D W,  Virtual colonoscopy  (Abst), Radiology Scientific Prgm 1994; 193(P):446. This technique was first described by Vining et al. in an earlier abstract by Vining D J, Gelfand D W, Noninvasive colonoscopy using helical CT scanning, 3D reconstruction, and virtual reality (Abst), SGR Scientific Program, 1994. This technique, referred to as “virtual colonoscopy”, requires a cleansed colon insufflated with air, a helical CT scan of approximately 30 seconds, and specialized three-dimensional (3D) imaging software to extract and display the mucosal surface. The resulting endoluminal images generated by the CT scan are displayed to a medical practitioner for diagnostic purposes. 
         [0006]    There have been several advances in virtual colonoscopy that have improved the imaging techniques, making it a more viable and effective screening option. One advantage of using a virtual colonoscopy as a screening process is the elimination of the invasiveness of a traditional colonoscopy. Traditional colonoscopies are preformed using a colonoscope that has a relatively large diameter (i.e., sufficient to form a seal with the anus) that includes, among other instruments, a scope, multiple lumens for introducing gas and/or liquid, and a working channel for introducing a snare or similar device into the colon. With such a device, there is a risk of straightening and/or perforating the colon because of its relative inflexibility and size. 
         [0007]    Another advantage of the virtual colonoscopy procedure is the elimination of the preparation process associated with a traditional colonoscopy. The typical preparation process involves the use of strong laxatives to purge any fecal waste from the colon. Such a process is extremely uncomfortable and is often cited as one of the least desirable parts of the whole procedure. Complete purging is not necessary with the virtual colonoscopy procedure. Rather, a fecal contrasting agent is used to facilitate digital subtraction of any residual feces from the virtual image. 
         [0008]    During the procedure, the patient lies on the CT scan area. A thin tube (approximately the diameter of a rectal thermometer) is placed in the rectum, through which gas is introduced into the colon. The gas is necessary to distend the bowel allowing any polyps to stand out from the normal surface. The patient holds their breath while the machine sweeps over the abdomen. The procedure is repeated with the patient lying on their stomach. The whole procedure takes approximately ten minutes. 
         [0009]    In addition to CT scan imaging modalities, magnetic resonance imaging (MRI) can also be used to perform the virtual colonoscopy. When using MRI, only certain MRI-compatible tools can be utilized (i.e., tools with only slight ferromagnetic properties). 
         [0010]    Even though the virtual colonoscopy is largely non-invasive as a screening process, a need still exists for non-invasive and minimally-invasive devices and methods for treating the colon (e.g., removing polyps) in the event the virtual colonoscopy identifies a problem area within the colon that merits further evaluation or treatment. 
         [0011]    For example, during conventional colonoscopies, polyps are removed using a wire-loop snare or similar device that slices the polyp from the wall of the colon. Such a technique is not effective for broad-base polyps or multiple polyps concentrated in a small area due to the excessive bleeding that could result as well as the increased risk of perforation. 
         [0012]    What is needed is a minimally-invasive method of removing polyps in the colon without the use of cutting tools such as polyp snares. 
       SUMMARY OF THE INVENTION 
       [0013]    In one embodiment, an apparatus comprises a snare and an actuator. The snare is formed of a material having an opacity complementary to a predetermined imaging system that is positionable external to a patient. The actuator is configured to steer the snare in response to an image of at least a portion of a colon of the patient. The image is generated by the predetermined imaging system. 
         [0014]    In another embodiment, an image of at least a portion of a colon of a patient is generated with an imaging system entirely external to the patient. A surgical instrument is disposed proximate to a polyp in the colon of the patient. The surgical instrument has a snare. The snare is steered to a location proximate the polyp based on the image of the colon. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]      FIG. 1  depicts a block diagram of a polyp removal system, according to an embodiment of the invention. 
           [0016]      FIG. 2  depicts a side view of a surgical device, according to an embodiment of the invention. 
           [0017]      FIG. 3  depicts a side view of an example of an RF snare that is a bipolar device, according to an embodiment of the invention. 
           [0018]      FIG. 4  depicts a perspective view of a cross-sectional cut-away of the surgical device shown in  FIG. 2  and taken along the line  4 - 4  in  FIG. 2 . 
           [0019]      FIG. 5  depicts an example of an application of the polyp removal system while disposed within a patient&#39;s colon. 
           [0020]      FIG. 6  depicts a system block diagram of a polyp removal system, according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0021]      FIG. 1  depicts a block diagram of a polyp removal system, according to an embodiment of the invention. As shown in  FIG. 1 , the polyp removal system  100  includes a surgical device  110 , an actuator  120  and an imaging system  130 . The surgical device includes a snare  114 . 
         [0022]    The snare  114  can be made of a material having an opacity complimentary to imaging system  130 . For example, in an embodiment where imaging system  130  is a fluoroscopic imaging system, snare  114  can be made of a material that is opaque to fluoroscopic imaging and electrically conductive such as a metal, a filled plastic or a combination of metal and filled plastic. For example, a suitable metal can be stainless steel or a metal filled with nitinol such as that described in U.S. Pat. No. 6,290,721, which is incorporated herein by reference in its entirety. For another example, a suitable filled plastic can be a plastic rendered opaque with bismuth trioxide, gold powder, platnum powder, bismuth oxychloride, iridium powder, tungsten, silver powder and/or barium sulfate. In another embodiment where imaging system  130  is a magnetic resonance imaging (MRI) system, snare  114  can be made of a material that is opaque to magnetic resonance such as plastic with slight ferromagnetic properties to avoid movement and/or image distortion from an MRI. 
         [0023]    Although the snare  114  is described and shown herein as a close loop, it should be understood that other similar devices are possible including, for example, biopsy forceps, biopsy needles, resecting devices, resecting wires, morcellators, etc. 
         [0024]    In yet another embodiment, imaging system  130  can include a virtual computer tomography (CT) system in combination with a fluoroscopic imaging system or a MRI system; in such an embodiment, snare  114  can be made of a material as described above. The physician can use virtual CT system to approximate an initial placement of the snare  114 , and then the fluoroscopic imaging system or MRI imaging system can be used to confirm and/or adjust the proper location of the RF snare  113 . In this embodiment, the location and orientation of snare  114  can be coordinated with the images produced with the virtual CT system of imaging system  130 . Thus, the images displayed by the imaging system  130  can be updated as the physician changes the position of the snare  114 . In this manner, the use of to a non-virtual imaging system is minimized, thereby reducing the time of the procedure. 
         [0025]      FIG. 2  depicts a side view of a surgical device, according to an embodiment of the invention. Surgical device  210  includes sheath  212 , RF snare  214 , actuator  216  and wires  218  and  219 . Actuator  216  is coupled to RF snare  214  and wires  218  and  219 . Wires  218  and  219  are also coupled to a distal end portion of sheath  212 . RF snare  214  is coupled to an electrical source (not shown), which provides an electrical current to RF snare  214 . 
         [0026]    Surgical device  210 , for example, can be used directly without being combined with an endoscope. In other words, surgical device  210  is made of appropriate materials that allow the distal end portion to be disposed within a patient and moved to an appropriate position, for example, within the patient&#39;s colon. For example, the sheath  212  can be made from a material such as plastic or rubber that is sufficient flexible so that the surgical device  210  can be inserted into the colon of the patient without straightening the colon. In addition, the sheath  212  can have an outer diameter, for example, of 3 mm or less. The construction and size of such a surgical device  210  allows for less patient discomfort than would be the case with a larger endoscope. 
         [0027]    In another embodiment, a low-profile guide device (not shown) can be used in conjunction with the surgical device  210 . In such an embodiment, the a low-profile guide sheath or guidewire can be delivered to the treatment site prior to delivery of surgical device  210 . Once delivered to the treatment site, the low-profile guide device can be used to lead the surgical device  210  to the treatment site. 
         [0028]    Surgical device  210  can be configured such that the distal end portion of sheath  212  can be steered and snare  214  can be rotated to a desired position relative to the colon wall. For example, a physician can steer the distal end portion of surgical device  210  in one direction or the opposite direction via wires  218  and  219 , and can rotate snare  214  via actuator  216 . The distal end portion of the sheath  212  can be steered, for example, in a lateral or side-to-side direction with respect to the length of the of the surgical device  210 . Through this combination of steering and rotating, the snare  214  can be positioned about a polyp within the colon. The following references provide examples of a rotatable snare and each reference is incorporated herein by reference: U.S. Pat. Nos. 6,162,209; 6,235,026; 6,409,727; 6,517,539; 6,554,942; 6,602,262; 6,911,032; and U.S. Patent Application Publication Nos. 2003/0105488, 2004/0181243, 2004/0199052, 2005/0113845, 2005/0119527, 2005/0124912, and 2005/0131279. 
         [0029]    The RF snare can be, for example, a bipolar device.  FIG. 3  depicts a side view of an example of an RF snare that is a bipolar device, according to an embodiment of the invention. As shown in  FIG. 3 , the RF snare  314  includes a first RF snare portion  314 ′ and a second RF snare portion  314 ″, which is electrically isolated from the first RF snare portion  314 ′ by insulation cap  313 . More specifically, first RF snare portion  314 ′ and second RF snare portion  314 ″ are disposed within insulation sleeves  315 ′ and  315 ″, respectively. Insulation sleeves  315 ′ and  315 ″ electrically insulate first RF snare portion  314 ′ and second RF snare portion  314 ″ from sheath  212 . In an alternative embodiment, the sheath can have, for example, two electrically isolated lumens, one for the first RF snare portion and one for the second RF snare portion; in such an alternative embodiment, the sleeves are not necessary because the sheath provides the electrical isolation. 
         [0030]    Distal ends of first RF snare portion  314 ′ and second RF snare portion  314 ″ are disposed within an insulation cap  313 . Insulation cap  313  electrically insulates first RF snare portion  314 ′ from second RF snare portion  314 ″. Thus, when current is applied to the RF snare  314 , an RF field is produced between the exposed portions of first RF snare portion  314 ′ and second RF snare portion  314 ″. This RF field can ablate tissue disposed between first RF snare portion  314 ′ and second RF snare portion  314 ″ as described below. In an alternative embodiment, the RF snare can be a monopolar device configured for use with a grounding pad (not shown) on the exterior of a patient. In yet another embodiment, the snare is not energized. 
         [0031]      FIG. 4  depicts a perspective view of a cross-sectional cut-away of the surgical device shown in  FIG. 2  and taken along the line  4 - 4  in  FIG. 2 . The portion of surgical device  210  shown in  FIG. 4  includes sheath  212 , an inner catheter  215 , RF snare portions  214 ′ and  214 ″, and shaft  217 . The distal end portion of shaft  217  is operationally coupled to actuator  216  (shown in  FIG. 2 ). The proximate end portion of shaft  217  is fixedly coupled to the distal end portions of RF snare portions  214 ′ and  214 ″. The proximate end portion of shaft  217  and the distal end portions of RF snare portions  214 ′ and  214 ″ are fixedly coupled to inner catheter  215 . Inner catheter  215  is rotatably disposed within sheath  212 . 
         [0032]    The proximate end portion of shaft  217  can be fixedly coupled, for example, to the distal end portions of RF snare portions  214 ′ and  214 ″ via a bearing (not shown) within inner catheter  215 . Alternatively, the proximate end portion of shaft  217  can fixedly coupled, for example, to inner catheter  215  by a first bearing (not shown) within inner catheter  215 , and the distal end portions of RF snare portions  214 ′ and  214 ″ can be fixedly coupled, for example, to inner catheter  215  by a second bearing (not shown) within inner catheter  215 . 
         [0033]    As the actuator  216  is actuated with a rotational motion, this rotational motion is translated to shaft  217  and, consequently, to inner catheter  215  and RF snare portions  214 ′ and  214 ″. In general, this embodiment allows the snare  212  to rotate via actuator  216  without, for example, an undesired “whipping effect” where the snare  212  rapidly rotates with little or no control of the position of the snare  212 . Because the medical device  210  may be disposed within a patient along a tortuous and lengthy path, it is desirable that rotation of the snare  214  via the actuator  216  is effective and controlled. The inner catheter  215  contacts and rotates against the inner surface of sheath  212  while maintaining the relative position of shaft  217  and RF snare portions  214 ′ and  214 ″ within inner catheter  215 . U.S. Pat. Nos. 6,840,900 and 6,454,702 disclose examples of an inner catheter similar to the inner catheter  215 , and each is incorporated herein by reference. 
         [0034]    The embodiment shown in  FIG. 4  is one of many possible embodiments. For example, the shape of the inner catheter can be a shape other than the star-like shape of inner catheter  215  shown in  FIG. 4 . Alternatively, the inner catheter arrangement can be embodied by any type of swivel structure such as a ball-and-socket arrangement. Various possible alternative embodiments are disclosed in U.S. Patent Application Publication 2005/0113845, entitled “Self-Orienting Polypectomy Snare Device,” the disclosure of which is incorporated herein by reference. Other alternative embodiments are also disclosed in U.S. Pat. No. 6,602,262, entitled “Medical Device Having Linear to Rotation Control,” the disclosure of which is incorporated herein by reference. 
         [0035]      FIG. 5  depicts an example of an application of the polyp removal system while disposed within a patient&#39;s colon. The patient&#39;s colon  10  is shown in  FIG. 5  in a cut-away view and includes a polyp  12  extending from the wall of the colon  10 . The distal end of the surgical device  210  can be disposed within the appropriate location within the colon  10 . As discussed above, a physician can steer the distal end portion of surgical device  210  in one direction or the opposite direction via wires  218  and  219 . RF snare  214  can be positioned about the stalk of polyp  12  through manipulation of actuator  216 . More specifically, once the distal end of surgical device  210  is positioned near the polyp  12 , the actuator  216  can be actuated to extend RF snare  214  from the sleeve  212 . Once extended from sleeve  212 , the RF snare  214  can be positioned about a portion of polyp  12  (e.g., the narrow stalk of polyp  12 ). Then, the RF snare  214  can be electrically activated while being closed about polyp  12 . 
         [0036]      FIG. 6  depicts a system block diagram of a polyp removal system, according to another embodiment of the invention. As shown in  FIG. 6 , the polyp removal system  300  includes a surgical device  310 , a remote actuator  320 , an imaging system  330  and an imaging system output device  340 . Remote actuator  320  is coupled to and controls surgical device  310 . Imaging system output display  340  is a display unit for imaging system  330  such as, for example, a video display. Patient  15  can be positioned within polyp removal system  300  such that surgical device  310  is appropriately disposed within patient  15  for polyp removal and imaging system  330  to obtain images of the patient  15  and surgical device  310 . 
         [0037]    Imaging system output device  340  and remote actuator  320  are disposed within an imaging system isolation region  400 . Imaging system isolation region  400  electromagnetically isolates imaging system output device  340  and remote actuator  320  from imaging system  330 . For example, where imaging system  330  is an MRI system, which can interact with any metal device, imaging isolation region  400  isolates imaging system output device  340  and remote actuator  320  from imaging system  330 . In such a case, imaging isolation region  400  can be, for example, an isolation chamber or room that prevents the MRI system of imaging system  330  from imaging people and equipment within imaging isolation region  400 . 
         [0038]    Remote actuator  320  is remote from surgical device  310  in the sense that actuator  320  is separated from surgical device  310  by imaging system isolation region  400 . Remote actuator  320  can be, for example, a robotic system by which a physician can control surgical device  310 . Where the surgical device  310  is similar to the surgical device  110  shown in  FIGS. 2-4 , a physician located within imaging system isolation region  400  can remotely control, for example, the position of the distal end portion of the sheath of surgical device  310 , the position and orientation of the RF snare of surgical device  310  and the electrical power provided to the RF snare. 
       Conclusion 
       [0039]    While various embodiments of the invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. While various embodiments have been particularly shown and described, it will be understood that various changes in form and details may be made. For example, although a particular type of actuator is shown in  FIG. 2 , other types of actuators also possible. Such alternative actuators include, for example, other types of manual devices controlled by a medical practitioner and non-manual devices such as machine-controlled actuators. Such a machine-controlled actuator can be operated in conjunction with the output of the imaging system. 
         [0040]    Any of the above-discussed surgical devices can further include a visualization system internal to the surgical device. In one embodiment, for example, the surgical device can include an internal optical fiber that is part of an optical system for visualization. In such an embodiment, the external imaging system can target tissue and the optical fiber within the surgical device can provide higher resolution information about the tissue site to minimize treating or affecting healthy tissue during the procedure. 
         [0041]    In other embodiments, the polyp removal system can be used in conjunction with multiple devices under virtual colonoscopy. For example, a resecting device can include a resecting razor and as tapler for closing the resecting site. Other embodiments include but are not limited to needles, biopsy forceps, snares, staplers, fasteners, suturing systems and other diagnostic and therapeutic tools.