2. Description of Related Art A stricture is an abnormally narrowed segment of an otherwise patent biological tube or conduit, such as the gastrointestinal tract. genito-urinary tract. pulmonary system. vascular system. or other systems in the body. Strictures may occur at various places within these systems in the body, such as in or near a blood vessel, the bronchial tree. the colon, a gastrointestinal body structure, a genital body structure, a kidney, a postoperative stricture. a pulmonary body structure, the rectum, the sphincter. or a urethral body structure.

The degree of narrowing, the length, and the significance of the stricture may differ greatly between particular strictures. and is responsive to the nature of the conduit which is subject to the stricture. Various etiological factors might be responsible for the development or exacerbation of any particular stricture, these may include. for example. infection.

inflammation. trauma (whether external. internal, or iatrogenic or other surgical trauma). or cancer. One or more of these factors causes the lumen of the affected conduit to narrow. that is, to stricture. with consequential obstruction of the lumen and compromise of the function of the conduit.

Treatment of strictures is aimed at restoration of intraluminal patency and physiological function. Because of the presence of abnormal or diseased tissue at the stricture, surgical treatment by endoscopic or by open surgical techniques often poses extra difficulties and has significant morbidity. Moreover. because the tissue of the stricture wall is already diseased. it often generates further scarring and fibrosis when it heals after surgery.

which can lead to recurrence of the stricture.

Accordingly, it would be advantageous to provide a method and system for treatment of strictures, such as for example urinary strictures, which use existing tissue, which promote healing of existing tissue, and which help to prevent recurrence of the stricture. This advantage is achieved in an embodiment of the invention in which a supporting frame, such as a cylindrical collagen frame with a diameter comparable to the normal lumen, is disposed intraluminally in a constricted region of the stricture. energy is emitted to ablate and harden the collagen and the tissue, and the supporting frame is used to maintain patency of the lumen and to prevent reformation of the stricture during a healing period.

Summary of the Invention The invention provides a method and system for treatment of body strictures to restore luminal diameter to within a normal diameter range, in which the stricture is dilated to stretch its lumen to a desired diameter, collagen is exuded near to existing tissue of the stricture so as to be absorbed by that tissue or adhere to that tissue. making a collagen- enhanced tissue structure. and energy is emitted to affect the collagen-enhanced tissue, such as by ablation or by hardening. Ablation and hardening may be repeated so as to create a set of layers of hardened collagen in the form of a supporting frame. preferably having a hollow cylindrical shape.

In a preferred embodiment, dilation of the stricture is achieved by expanding one or more balloons. or by the pressure of exuded collagen, until the stricture is larger than a normal diameter range. When energy is emitted into the collagen, the stricture contracts back to the normal diameter range, either by ablation of excess tissue or by plating of the stricture wall.

In a preferred embodiment, the stricture's tissue is also isolated by a set of balloons at either or both ends of the stricture, so as to isolate the stricture and restrict the collagen to the stricture's tissue.

In a preferred embodiment, the stricture's tissue is also supported by a stent.

which is preferably tack-welded onto the stricture's tissue using collagen. Collagen adheres to the stent, which supports the stricture's tissue until the stent is absorbed into that tissue.

Brief Description of the Drawings Figure 1 shows a urinary stricture with a catheter positioned therein.

Figure 2 is a flowchart for a method of operation for the catheter.

Figure 3 shows a urinary stricture with a stent positioned and attached therein.

Detailed Description of the Preferred Embodiment Urinary Stricture Figure l shows a urinary stricture with a catheter positioned therein.

A stricture 100 comprises a mass of relatively healthy tissue 101. forming a first portion of a wall 102 for a lumen 103 or other pathway, and a mass of relatively weakened tissue 104, forming a second portion of the wall 102 for the lumen 103 in a constricted region 105. The stricture 100 is shown with the lumen 103 having at least some flow capability, but there are structures 100 in which the flow capability has been reduced to zero, either because the wall 102 in the constricted region 105 has collapsed completely so as to block the lumen 103, because the lumen 103 is blocked with a mass of tissue or other substances (not shown), or some combination of these two problems.

A catheter 110 comprises a distal end 111 and a proximal end 112. the latter being coupled to a tube 113 or other connector for coupling control signals, energy. and fluids between the catheter and 110 and a control system (not shown).

In a preferred embodiment, the catheter 110 comprises a catheter such as shown in one of the following documents or in parent cases thereof: United States Application Serial No. 08/717,612, Express Mail Mailing Number EM266118924US. titled "Ablation of Rectal and Other Internal Body Structures", filed September 20, 1996, attorney docket number VCAR-001. hereby incorporated by reference as if fully set forth herein.

In a preferred embodiment, the catheter 110 is about 5 to about 6 French in width (1 French equals 1/3 of a millimeter or about 0.18 inch). However, in alternative

embodiments. the catheter 110 may be of lesser or greater width so as to accommodate strictures of lesser or greater diameter.

The catheter 110 also comprises a first x-ray marker 121, preferably disposed at or near the distal end 111 of the catheter 110 and a second x-ray marker 121, preferably disposed at or near the proximal end 111 of the catheter 110. With suitable x-ray or fluoroscopy equipment, a radiologist or surgeon can position the catheter 110 relative to the constricted region 105 without any requirement for a camera or other optical equipment disposed in or near the constricted region 105.

The catheter 110 also comprises a first ring balloon 122, preferably disposed at or near the distal end 111 of the catheter 110 and a ring balloon 122. preferably disposed at or near the proximal end 111 of the catheter 110. The ring balloons 122 are disposed so that.

when inflated and in combination with the body of the catheter 110, they physically seal off gas or fluids between the constricted region 105 and other portions of the lumen 103 outside the constricted region 105.

In alternative embodiments, the ring balloons 122 may comprise other shapes.

and in particular, the ring balloon 122 disposed at the distal end 111 of the catheter 110 may comprise a spherical or ellipsoidal balloon disposed to seal off the lumen 103 without need for combination with the body of the catheter 110. In such alternative embodiments. the spherical or ellipsoidal balloon is disposed in substantially the same location as shown for the ring balloon 122, except that the spherical or ellipsoidal balloon is disposed to substantially block the lumen 103 and thus seal it off.

In further alternative embodiments, the ring balloons 122 may be porous.

microporous, semiporous, or some combination thereof, or may be disposed within the lumen 103 slightly imperfectly, so that the seal made by the ring balloons 122 is not necessarily completely gas-tight or even completely fluid-tight.

The catheter 110 also comprises an expansion balloon 123, preferably disposed at or near a middle portion of the catheter 110. The expansion balloon 123 is disposed so that when inflated it physically forces the constricted region 105 of the stricture

100 to open to a greater diameter. such as a diameter within a normal diameter range for the lumen 103.

In a preferred embodiment, the expansion balloon 123 comprises a porous.

microporous. or semiporous membrane through which a mass of collagen 130, a solution including saline, or other flowable substances, may flow. The catheter 110 comprises an internal lumen (not shown) which couples flowable substances from the tube 113, so as to exude those flowable substances out from a set of holes 124 and to the expansion balloon 123. When flowable substances are exuded out from the holes 124 to the expansion balloon 123, pressure from the flowable substances causes the expansion balloon 123 to expand and to physically force the constricted region 105 of the stricture 100 to open to the greater diameter.

In a preferred embodiment. the expansion balloon 123 comprises a spherical or ellipsoidal shape. so as to expand in a middle region near the stricture 105. In a preferred method of operation, the expansion balloon 123 is first expanded to its maximum diameter.

then deflated somewhat so as to allow flowable substances to flow into the region of the stricture 1 05.

However, in alternative embodiments, the expansion balloon 123 may comprise another shape, such as a concave shape (shaped somewhat like the stricture itself) having a greater degree of expansion at a distal end of the stricture 105 and at a proximal end of the stricture 105, and having a lesser degree of expansion at a middle portion of the stricture 105. The expansion balloon 123 can take on this concave shape by being comprised of a relatively thinner (and therefore more expansible) rubber material at the distal end of the stricture 105 and at the proximal end of the stricture 105, while being comprised of a relatively thicker (and therefore less expansible) rubber material at the middle portion of the stricture 105.

The catheter 110 also comprises a set of electrodes 125, preferably disposed at or near a middle portion of the catheter 110. The electrodes 125 are coupled using the tube 113 to a power source (not shown). The power source provides energy to the electrodes 125.

which emit that energy into the constricted region 105 of the stricture 100 so as to affect the

mass of collagen 130, the relatively weakened tissue 104. and (in some embodiments) the relatively healthy tissue 101.

The catheter 110 also comprises a set of sensors 126, preferably disposed at or near a surface of the catheter 110. The sensors 126 are coupled using the tube 113 to a control system (not shown) and to an operator display (not shown). The sensors 126 provide signals to the control system for feedback control, and to the operator display for displaying information to an operator.

In a preferred embodiment, the sensors 126 comprise a plurality of temperature sensors, such as thermistors or thermocouples, and the control system provides feedback control to maintain a temperature of the mass of collagen 130 at a temperature selected bv the operator. In a preferred embodiment, the operator display comprises a temperature reporting gauge. However, it would be clear to those skilled in the art that other and further sensor signals. feedback control. and display signals, would be useful. and are within the scope and spirit of the invention.

Method of Use Figure 2 is a flowchart for a method of operation for the catheter.

A method 200 of operation for the catheter 110 comprises a sequence of steps between the flow points 210 and 230. In a preferred embodiment. the method 200 is carried out using the catheter 110, as well as other and further equipment which would be clearly deemed necessary or desirable by those skilled in the art.

At a flow point 210, it is desired to treat the urinary stricture 100.

At a step 221, the catheter 110 is inserted into the constricted region 105 of the urinary stricture 100. As noted herein, the radiologist or surgeon positions the catheter 110 relative to the urinary stricture 100 using the x-ray markers 121 and a fluoroscope or other x-ray device.

At a step 222, the first ring balloon 122 and the second ring balloon 122 are expanded to isolate the constricted region 105 from other portions of the lumen 103 in a gas- tight and fluid-tight manner.

At a step 223, the mass of collagen 130 and a saline solution are flowed through the tube 113, through the body of the catheter 110, through the holes 124, and into the expansion balloon 123. The flow of the mass of collagen 130 and the saline solution into the expansion balloon 123 causes the expansion balloon 123 to expand, physically forcing the relatively weakened tissue 104 out to a diameter greater than the normal diameter range for the lumen 103.

At a step 224. the mass of collagen 130 and the saline solution are flowed through the expansion balloon 123, into contact with the relatively weakened tissue 104. The mass of collagen 130 and the saline solution are absorbed into the relatively weakened tissue 104.

At a step 225, electrical energy is conducted from the power source through the tube 113, through the body of the catheter 110, to the electrodes 125. The electrodes 125 emit RF energy (at a preferred frequency of between about 400 megahertz and about 700 megahertz, but possibly at other frequencies, such as microwave frequencies). which is received by the saline solution and thus transmitted to the relatively weakened tissue 104.

The relatively weakened tissue 104, having been suffused with the mass of collagen 130, receives the RF energy emitted by the electrodes 125 and is ablated. As RF energy is received by the relatively weakened tissue 104, the relatively weakened tissue 104 is heated to at least about 90 to 120 degrees Celsius, causing ablation to occur by means of cell death. dehydration, denaturation, or other means.

In a second preferred embodiment, the mass of collagen 130 forms a surface layer over the wall 102 of the relatively weakened tissue 104. At the step 224. the mass of collagen 130 adheres to the surface while the saline solution is absorbed into the relatively weakened tissue 104. At the step 225. the mass of collagen 130 is cooked or otherwise thermoset by the RF energy so as to solidify into a layer of hardened collagen, preferably

about I mil (0.001 inch or about 0.0025 centimeters) in thickness. The step 224 and the step 225 are repeated a number of times sufficient to create a layer of hardened collagen effective to restrain fluid flowing in the lumen 103 from seeping into the relatively weakened tissue 104.

The mass of collagen 130, having been heated by application of RF energy, cooks or otherwise thermosets to a solidified state.

At a step 226, the relatively weakened tissue 104, having been ablated, shrinks to a diameter within a normal diameter range for the lumen 103.

At a step 227, the relatively weakened tissue 104, as supported by the mass of collagen 130. is allowed to heal by growth of epithelial cells.

At a flow point 230, the urinary stricture 100 has been treated and should be in condition for normal operation.

In alternative embodiments, the method 200 may be applied to other body structures or other places within the gastrointestinal tract, genito-urinary tract, pulmonary system. vascular system, or other systems in the body, such as in or near a blood vessel. the bronchial tree. the colon, a gastrointestinal body structure, a genital body structure. a kidney, a postoperative stricture, a pulmonary body structure, the rectum. the sphincter. or a urethral body structure.

Figure 3 shows a urinary stricture with a stent positioned and attached therein.

A stent 300 comprises a substantially cylindrical structure having a distal end 301 and a proximal end 302, and formed in the shape of a mesh or a woven structure, such as used in gauze or stretchable fabrics. In a preferred embodiment, the stent 300 comprises a suture material. such as catgut, polygalactic polymer 910, or PDS.

The stent 300 is disposed in the urinary stricture 100 by coupling the stent 300 to the catheter 110, disposing the catheter 110 substantially within the constricted region 105

of the urinary stricture 100, and coupling the stent 300 to at least a portion of the urinary stricture 100.

The stent 300 is coupled to the urinary stricture 100 by coupling the distal end 301 of the stent 300 to a coupling spot 310 on the relatively healthy tissue 101 outside the constricted region 105 of the urinary stricture 100 by means of "tack welding''. Tack welding" refers to disposing the distal end 301 of the stent 300 at the coupling spot 310.

exuding collagen so as to adhere to both the distal end 301 of the stent 300 and the coupling spot 310, and emitting energy so as to harden the collagen to permanently or semipermanently couple the distal end 301 of the stent 300 to the coupling spot 310.

In a preferred embodiment. the coupling spot 310 comprises an O-shaped ring around the lumen 103.

Alternative Embodiments Although preferred embodiments are disclosed herein, many variations are possible which remain within the concept, scope, and spirit of the invention, and these variations would become clear to those skilled in the art after perusal of this application.