US 20060235333 A1
A novel capture device apparatus comprising: (a) a capture device portion, at least a part of which is adaptable for insertion into a patient and (b) a control unit. The capture device portion comprises one or more apertures and one or more electroactive polymer actuators that open and close the one or more apertures based on control signals sent from the control unit. In another aspect of the present invention, a method of capturing a specimen within a patient's body of provided. The method comprises (a) providing a capture device apparatus like that above, (b) inserting at least a portion of the capture device portion of the apparatus into the patient such that the capture device portion is adjacent the specimen; and (c) closing the one or more apertures using the control unit, thereby capturing the specimen.
1. A capture device apparatus, comprising:
(a) a capture device portion, at least a part of which is adaptable for insertion into a patient, said capture device portion comprising one or more apertures and one or more electroactive polymer actuators, wherein said one or more actuators open and close said one or more apertures based on received control signals; and
(b) a control unit coupled to said one or more actuators and sending control signals to said one or more actuators.
2. The capture device apparatus of
3. The capture device apparatus of
4. The capture device apparatus of
5. The capture device apparatus of
6. The capture device apparatus of
7. The capture device apparatus of
8. The capture device apparatus of
9. The capture device apparatus of
10. The capture device apparatus of
11. The capture device apparatus of
wherein said one or more apertures are opened upon expansion of a first set of said one or more actuators and contraction of a second set of said one or more actuators, and
wherein said one or more apertures are closed upon contraction of said first set and expansion of said second set.
12. The capture device apparatus of
13. The capture device apparatus of
14. The capture device apparatus of
15. The capture device apparatus of
16. The capture device apparatus of
17. The capture device apparatus of
18. A method of capturing a specimen within a patient's body comprising:
providing a capture device apparatus, said capture device apparatus comprising: (a) a capture device portion, at least a part of which is adaptable for insertion into a patient, said capture device portion comprising one or more apertures and one or more electroactive polymer actuators, wherein said one or more actuators open and close said one or more apertures based on received control signals; and (b) a control unit coupled to said one or more actuators and sending control signals to said one or more actuators;
inserting at least a portion of said capture device portion into said patient such that said capture device portion is adjacent a specimen; and
closing said one or more apertures using said control unit, thereby capturing said specimen.
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This patent application is a continuation of co-pending application U.S. Ser. No. 10/177,838, filed Jun. 21, 2002, entitled “Electronically Activated Capture Device,” which is related to U.S. Ser. No. 09/971,419, filed Oct. 5, 2001, entitled “Robotic Endoscope,” now U.S. Pat. No. 6,835,173. Both of these related applications are incorporated herein by reference in their entireties.
1. Field of the Invention
The present invention relates to medical devices useful for the capture of a specimen within a patient.
2. Background of the Invention
Capture devices such as polypectomy snares, stone removal snares and baskets, and embolus capture devices, are routinely used in urology, endoscopy, interventional cardiology, and interventional radiology to extract specimens from the body of a patient, for example, to remove a blockage or to provide a biopsy specimen. Typically, long pull-wires are used to actuate a basket, snare or other capture mechanism at a catheter tip. Such mechanisms, however, limit the size, flexibility, and actuation force of the device.
The present invention provides various advantages over prior art capture devices, which typically rely on pull wire actuators.
According to one aspect of the present invention, a novel capture device apparatus is provided in which electroactive polymer actuators are used to capture a specimen of interest. The capture device apparatus preferably comprises: (a) a capture device portion, at least a part of which is adaptable for insertion into a patient and (b) a control unit. The capture device portion comprises one or more apertures and one or more electroactive polymer actuators that open and close the one or more apertures based on control signals sent from the control unit.
The electroactive polymer actuators beneficially comprise (a) an active member, (b) a counter-electrode and (c) a region comprising an electrolyte disposed between the active member and the counter-electrode. In preferred embodiments, the one or more electroactive polymer actuators further comprise a substrate layer and a barrier layer, with the active member, counter-electrode and the region comprising the electrolyte being disposed between the substrate layer and barrier layer. Preferred electroactive polymers for the practice of the present invention include polyaniline, polypyrrole, polysulfone and polyacetylene.
The one or more apertures within the device capture portion can be mechanically biased, for example, toward either an open position or a closed position.
In some embodiments, the one or more apertures are closed upon contraction of the one or more actuators and opened upon expansion of the one or more actuators. Conversely, in other embodiments, the one or more apertures are opened upon contraction of the one or more actuators and closed upon expansion of the one or more actuators.
In still other embodiments, the one or more apertures are (a) opened upon expansion of a first set of one or more actuators and contraction of a second set of one or more actuators, and (b) closed upon contraction of the first set of actuators and expansion of the second set of actuators.
In some embodiments, the control unit can simply comprise a power source and a switch. In others, the control unit can be more complex, comprising, for example, a computer. The control unit can be coupled to the one or more actuators in a number of ways, for example, via an electrical cable or wireless interface.
According to another aspect of the present invention, a method of capturing a specimen within a patient's body is provided. The method comprises (a) providing a capture device apparatus like that above, (b) inserting at least a portion of the capture device portion of the apparatus into the patient such that the capture device portion is adjacent the specimen; and (c) closing the one or more apertures using the control unit, thereby capturing the specimen.
In some embodiments, at least one aperture within the capture device portion is lined by one or more blades, allowing the specimen to be severed using the blades. In other embodiments, a vacuum is provided within the device capture portion to draw the specimen into the one or more apertures, assisting capture of the specimen.
The capture device apparatus can be inserted, for example, into a body lumen such as those found within the gastrointestinal tract, respiratory tract, vasculature or urinary tract.
Specimens appropriate for removal using the capture device apparatus of the present invention, include polyps (for instance, sessile and pedunculated polyps), stones, emboli, and various biopsy specimens.
One advantage of the present invention is that a wide array of capture devices is provided.
Another advantage of the present invention is that compact capture devices are provided which are capable of exerting very large actuation forces.
These and other embodiments and advantages of the present invention will become apparent to those of ordinary skill in the art based on the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein.
According to preferred embodiments of the present invention, capture devices for insertion into the body of a patient are provided, which contain one or more electroactive polymer actuators. The devices of the present invention can be used to capture a wide array of specimens within the body, for example, emboli, polyps (including polyps of the respiratory tract, cervix and colon), stones (including stones of the liver, gallbladder, and urinary tract), and various biopsy specimens. Patients include vertebrate patients, especially human patients.
Actuators based on electroactive polymers, members of a family of plastics referred to as “conducting polymers,” have a number of advantageous attributes, including small size, large force and strain, low cost and ease of integration into the capture devices of the present invention.
Electroactive polymers are a class of polymers characterized by their ability to change shape in response to electrical stimulation. They typically structurally feature a conjugated backbone and have the ability to increase electrical conductivity under oxidation or reduction. Some common electroactive polymers are polyaniline, polysulfone, polypyrrole and polyacetylene. Polypyrrole is pictured below:
These materials are typically semi-conductors in their pure form. However, upon oxidation or reduction of the polymer, conductivity is increased. The oxidation or reduction leads to a charge imbalance that, in turn, results in a flow of ions into the material in order to balance charge. These ions, or dopants, enter the polymer from an ionically conductive electrolyte medium that is coupled to the polymer surface. The electrolyte may be, for example, a gel, a solid, or a liquid. If ions are already present in the polymer when it is oxidized or reduced, they may exit the polymer.
It is well known that dimensional changes may be effectuated in certain conducting polymers by the mass transfer of ions into or out of the polymer. For example, in some conducting polymers, the expansion is due to ion insertion between chains, whereas in others interchain repulsion is the dominant effect. Thus, the mass transfer of ions both into and out of the material leads to an expansion or contraction of the polymer.
Currently, linear and volumetric dimensional changes on the order of 25% are possible. The stress arising from the dimensional change can be on the order of 3 MPa, far exceeding that exerted by smooth muscle cells.
Referring now to
Active member 12 includes an electroactive polymer. Many electroactive polymers having desirable tensile properties are known to persons skilled in the art. In accordance with preferred embodiments of the invention, active member 12 is a polypyrrole film. Such a polypyrrole film may be synthesized by electrodeposition according to the method described by M. Yamaura et al., “Enhancement of Electrical Conductivity of Polypyrrole Film by Stretching: Counter-ion Effect,” Synthetic Metals, vol. 36, pp. 209-224 (1988), which is incorporated herein by reference. In addition to polypyrrole, any conducting polymer that exhibits contractile or expansile properties may be used within the scope of the invention. Polyaniline is an example of such a usable conducting polymer.
Electrolyte 14 may be, for example, a liquid, a gel, or a solid, so long as ion movement is allowed. Moreover, where the electrolyte 14 is a solid, it should move with the active member 12 and should not be subject to delamination. Where the electrolyte 14 is a gel, it may be, for example, an agar or polymethylmethacrylate (PMMA) gel containing a salt dopant. Where the electrolyte is a liquid, it may be, for example, a phosphate buffer solution. The electrolyte is preferably non-toxic in the event that a leak occurs in vivo.
Counter-electrode 18 is in electrical contact with electrolyte 14 in order to provide a return path for charge to a source 20 of potential difference between member 12 and electrolyte 14. Counter-electrode 18 may be any electrical conductor, for example, another conducting polymer, a conducting polymer gel, or a metal such as gold or platinum, which can be applied by electroplating, chemical deposition, or printing, for example. In order to activate actuator 10, a current is passed between active member 12 and counter-electrode 18, inducing contraction or expansion of member 12. Additionally, the actuator may have a flexible skin for separating the electrolyte from an ambient environment.
The actuators can be provided in an essentially infinite array of configurations as desired, including planar actuator configurations, cylindrical actuator configurations (e.g., see the actuator illustrated in
Additional information regarding the construction of actuators, their design considerations, and the materials and components that may be employed therein, can be found, for example, in U.S. Pat. No. 6,249,076, assigned to Massachusetts Institute of Technology, and in Proceedings of the SPIE, Vol. 4329 (2001) entitled “Smart Structures and Materials 2001: Electroactive Polymer and Actuator Devices (see, in particular, Madden et al, “Polypyrrole actuators: modeling and performance,” at pp. 72-83), both of which are hereby incorporated by reference in their entirety.
Actuators can be disposed within the capture devices of the present invention in numerous ways. For example, the actuators can be separately manufactured and subsequently attached to structural elements of the capture devices. As another example, multiple actuators or actuator arrays can be disposed upon a substrate layer, for example, a polymeric sheet, which is associated with the capture device.
As a specific example,
The capture device 100 of
In the embodiment of
Referring now to
Of course, numerous flexible tubular structural elements are known besides the structural element 102 of
Where the capture devices of the present invention are employed in operations requiring a cutting step (for example, in the removal of gastrointestinal polyps), it may be desirable to provide the aperture with a cutting edge. For example, it may be possible to sharpen the material defining the edges of the aperture, for instance, where the material is a metal or a hard plastic material. Alternatively, as illustrated in
In the above embodiments, the actuators are wrapped around a portion of the circumference of the tubular structural element 102. However, numerous additional configurations are possible. For example, referring now to
In the above embodiments, the actuators are used to open the device aperture to allow capture of a specimen of interest, while the closing force is provided by the inherent elasticity of the structural element. In other embodiments, the actuators are used to close the apertures, with the opening force being inherent in the structural element.
For example, referring now to
A structure likes that of FIGS. 5A-B can be readily incorporated into the distal end of a capture device 100 as illustrated in
In alternative designs, multiple actuators can be placed in opposition with one another to achieve the desired shape. For example, referring now to
In the configuration illustrated in
The effect of buckling the outer jacket 104 can be better seen in
Hence, in the capture device of FIGS. 7A-B, opening and closing forces are exerted by two sets of opposing actuators. This eliminates the need for an inherent mechanical bias to provide the necessary force to open or close the device. The same is true for the device of FIGS. 7C-D immediately below.
A variation of the design of FIGS. 7A-B is illustrated in FIGS. 7C-D. Referring now to
In the configuration illustrated in
In general, the orientation of the aperture(s) in the capture devices of the present invention can be inferred from the intrinsic position-dependent electrical properties of the electroactive polymer actuators therein. However, strain gauges can be employed to provide electronic feedback concerning the orientation of the actuators and openings within the assembly, if desired. This electronic feedback will also provide a number of additional advantages, including greater stability, error correction, and immunity from drift. Electronic feedback also permits a haptic interface to the controller, in which the operator may “feel” the force fed back. Strain gauges suitable for use in the present invention include (a) feedback electroactive polymer elements whose impedance or resistance varies as a function of the amount of strain in the device and (b) conventional strain gauges in which the resistance of the device varies as a function of the amount of strain in the device, thus allowing the amount of strain to be readily quantified and monitored. Such strain gauges are commercially available from a number of different sources, including National Instruments Co., Austin, Tex., and include piezoresistive strain gauges (for which resistance varies nonlinearly with strain) and bonded metallic strain gauges (for which resistance typically varies linearly with strain).
Feedback regarding the capture device configuration, as well as the relationship between the capture device and the body into which it is inserted (including the specimen which is sought for capture), may also be obtained using conventional medical imaging techniques, including radiographic contrast dye techniques, fluoroscopy, ultrasound imaging, MR imaging, computed tomography, visual endoscopy, and other well known modalities of image-guided surgery.
The actuators within the capture devices of the present invention can be individually controlled or controlled as a group. Where individual control is desired, the actuators (and strain gauges, if desired) may be placed in direct communication with a controlling device by means of dedicated circuits linking each of these elements to the device. On the other hand, these elements can also be deployed in an array in which each element is in communication with the controlling device by means of a common communications cable. The signals from each element may be digital or analog. If need be, digital-to-analog or analog-to-digital converters may be provided to convert the signals from one format to the other. The signals to and from each element may be conveniently managed and transmitted over a common cable by multiplexing.
In many preferred embodiments, the actuators are provided on a substrate layer, which is subsequently incorporated into the capture device. For example, FIGS. 9A-C illustrate a structural element 102, which is a braided wire tube analog of the structural element 102 of
The substrate layer 105 with attached actuators 110 of
It is noted that the device of
Actuators 110 can be provided on substrate layer 105 in numerous configurations. For example, a single actuator 110 is shown in cross-section in
The substrate layer 105 is formed of a flexible material. Electrically insulating materials are preferred. Flexible materials useful in the construction of the substrate layer 105 include the following polymeric materials: polyolefins such as metallocene catalyzed polyethylenes, polypropylenes, and polybutylenes and copolymers thereof; ethylenic polymers such as polystyrene; ethylenic copolymers such as ethylene vinyl acetate (EVA), butadiene-styrene copolymers and copolymers of ethylene with acrylic acid or methacrylic acid; polyacetals; chloropolymers such as polyvinylchloride (PVC); fluoropolymers such as polytetrafluoroethylene (PTFE); polyesters such as polyethylene terephthalate (PET); polyester-ethers; polysulfones; polyamides such as nylon 6 and nylon 6,6; polyamide ethers such as polyether block amides; polyethers; elastomers such as elastomeric polyurethanes and polyurethane copolymers; silicones; polycarbonates; polychloroprene; nitrile rubber; butyl rubber; polysulfide rubber; cis-1,4-polyisoprene; ethylene propylene terpolymers; as well as mixtures and block or random copolymers of any of the foregoing are non-limiting examples of biostable polymers useful for manufacturing the medical devices of the present invention.
In some embodiments, the substrate layers are constructed from stiff polymers like those used in electronic printed circuits or cables, such as polyimide (e.g., Kapton®), and relieved by selective cutting, e.g. with a laser, to provide the appropriate flexibility.
The active member 112 of
The counter-electrode 118 may be any electrical conductor, for example, another conducting polymer or a metal such as gold or platinum, preferably in a flexible form, for example, in the form of a thin layer or foil, which can be applied by electroplating, chemical deposition, or printing, for example.
The electrolyte within the electrolyte-containing layer 114 can be, for example, a liquid, a gel, or a solid as previously discussed. In the embodiment illustrated, contact between the active member 112 and counter-electrode 118 is prevented by providing the electrolyte within a flexible porous layer of insulating polymer material. Beneficial insulating polymers for this purpose include insulating polymers within the polymer list provided above in connection the substrate layer 105. PTFE is a specific example.
Thin track wires 122 a and 122 c are connected to active member 112 and counter-electrode 118, respectively, allowing for electrical communication with a controlling device (not shown).
Barrier layer 120 is provided for several reasons. For example, the barrier layer 120 prevents species within the electrolyte-containing layer 114 from escaping. Appropriate materials for the barrier layer include those discussed above in connection with substrate layer 105.
Numerous actuator configurations other than that illustrated in
As another example,
As previously noted, substrate layer 105 is formed from an insulating material in many preferred embodiments. However, where the active elements are to be simultaneously actuated, then the substrate layer 105 can be formed form a conductive material, for example, a metal such as gold or platinum. In this instance, the substrate can be used as a current path, eliminating the need for independent track wires.
A wide range of controlling devices can be used with the present invention. For example, the controlling device can simply consist of a switch and a power source, such as a battery. Alternatively, the controlling device can be significantly more sophisticated, which is desirable, for example, where individual actuator control is required. As a specific example, a computer provided with an electronic interface (including drivers) can be employed as a controlling device 154. In this instance, signals are sent from drivers in the electronic interface associated with the personal computer 154, through cable bundle 150, to the actuators within capture device portion 100, to open and close the capture device portion 100 as needed.
As noted above, in some embodiments of the invention, the capture device portion 100 is provided with strain gauges, in which case signals are output from the strain gauges and sent via the cable 150 to the electronic interface within controlling device 154. These signals are processed within controlling device 154, for example, to provide feedback regarding the state of the actuators.
Numerous variations are possible. As an example, although the capture device portion 100 and controlling device 154 are illustrated as separate units in the device of
As another example, the body of the capture device portion 100 can contain a channel leading to a vacuum system as illustrated in
Another example is illustrated in
Although the present invention has been described with respect to several exemplary embodiments, there are many other variations of the above-described embodiments that will be apparent to those skilled in the art, even where elements have not explicitly been designated as exemplary. It is understood that these modifications are within the teaching of the present invention, which is to be limited only by the claims appended hereto.