# Patent

## Title
System and method for modifying a flexibility of a brachythereapy catheter

## Abstract

A flexible, multi-lumen brachytherapy device includes a plurality of loose lumens extend through a hub towards a single point of attachment at a distal rigid section. Because the lumens are attached at only a single distal location, the lumens are free to move axially and rotatably, thereby increasing the overall flexibility of the device to thereby decrease intermittent device movement while increasing patient comfort. A novel keyed stylet can be selectively inserted to increase the rigidity of the device as needed. The ability to dynamically modify the rigidity of the brachytherapy device provides a comprehensive brachytherapy solution that satisfies concerns of the patient, the surgeon and the radiologists.

## Background
FIELD OF THE INVENTION
This invention relates generally to methods and apparatus for use in treating proliferative tissue disorders, and more particularly to the treatment of such disorders with a multi-lumen brachytherapy device.
BACKGROUND
Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual tumor margin after resection, with the goal of reducing its size or stabilizing it.
Radiation therapy can be administered through one of several methods, or a combination of methods, including external-beam radiation, stereotactic radiosurgery, and permanent or temporary brachytherapy. The term “brachytherapy,” as used herein, refers to radiation therapy delivered by a source of therapeutic rays inserted into the body at or near a tumor or other proliferative tissue disease site.
One interstitial brachytherapy therapy system is the Mammosite® system, provided by Hologic, Inc. of Bedford, Mass. The MammoSite system includes a catheter shaft with an inflatable balloon mounted on its distal end. A lumen extends within the catheter shaft, into the balloon. The catheter shaft is inserted into a body so that the balloon is positioned within a resected cavity. The balloon is subsequently inflated and radioactive material, for example in the form of one or more radioactive seeds, is loaded into the lumen for radiation delivery.
A typical breast brachytherapy radiation treatment plan involves insertion of the balloon by a doctor during a lumpectomy. During a series of follow up visits, a radiologists delivers radiation dosing to the patient by loading radioactive material into the balloon catheter for a determined period of time to achieve a desired dosage. The brachytherapy catheter system is removed upon completion of treatment. Although the catheter must have sufficient rigidity for insertion into the resected cavity, because the brachytherapy catheter system is left in place between treatments it is desirable that the catheter be flexible; rigid catheter designs not only cause patient discomfort but may result in undesirable torque of the balloon which results in a shift of balloon location between treatments.
In single lumen brachytherapy catheters, the lumen is generally centered within the balloon such that the balloon generates isodose profiles in the target tissue that are substantially symmetrical, similar in shape to the inflated balloon. However, symmetric dosing may not always be desirable, as the resection cavity may not be uniform or regular in shape and size. Asymmetric dosing methods, such as those described in U.S. Pat. No. 6,749,555 include catheters with multiple lumens, where radioactive seeds may be placed within the different lumens to achieve different dosing profiles. Methods and systems for using multiple lumens for interstitial breast brachytherapy are also described by Lubock in U.S. Patent application publication number 20070167667, and by Cutrer in U.S. Patent application publication number 20070142694.
One problem with existing multi-lumen designs is that they increase the rigidity of the catheter, concomitantly increasing patient discomfort and the occurrence of balloon movement subsequent to initial placement. It would be desirable to identify a design for multi-lumen brachytherapy device which overcomes the problems of the prior art.
SUMMARY
According to one aspect of the invention, a stylet includes a stylet shaft having a distal end and a proximal end, a key feature at the distal end of the shaft for engaging a lock feature of a rigid structure located at a distal end of a brachytherapy device and a tab feature located at a proximal end of the shaft.
According to another aspect of the invention, an implantable apparatus for treating a proliferative disorder in a patient comprising a plurality of separate flexible dosing lumens, each having a proximal end and a distal end, wherein each distal end of each dosing lumen extends into a different one of the plurality of openings of a rigid member, the rigid member including a lock feature and a stylet comprising a key feature, the stylet for selectively modifying a rigidity of the implantable apparatus by selective engagement of the key feature with the lock feature.
According to a further aspect of the invention, a method for controlling the rigidity of a brachytherapy device that includes a plurality of flexible lumens attached at a distal end and gathered between a proximal end and a distal end by a hub, the method including the steps of inserting a rigid stylet through a hub of the brachytherapy device towards the distal end of the device, the stylet having a key feature and, the distal end of the device having a lock feature, and inserting the key feature of the device into the lock feature of the device to increase the rigidity of the device.
According to an additional aspect of the invention, a method for controlling the rigidity of a brachytherapy device that includes a plurality of flexible lumens attached at a distal end and gathered between a proximal end and a distal end by a hub, the method including the steps of removing a rigid stylet that extends through a hub of the brachytherapy device towards the distal end of the device, the stylet having a key feature and the distal end of the device having a lock feature, the key feature of the device engaging the lock feature of the device prior to the step of removing, wherein the step of removing includes the step of unlocking the key feature from the lock feature and removing the stylet to increase the flexibility of the device.



BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a diagram of the flexible multi-lumen brachytherapy device of the present invention;
FIG. 2 is a diagram of a second embodiment of the flexible multi-lumen brachytherapy device of the present invention;
FIGS. 3A-3C include diagrams of various embodiments of a hub of the brachytherapy device of FIG. 1 or 2, the embodiments illustrated at various perspectives;
FIGS. 4A-4E are diagrams of different perspectives and different embodiments of the rigid section of the device of FIG. 1 or 2, illustrating various geometries;
FIGS. 5A and 5B are diagrams of the device of the present invention, illustrating the flexibility of the device in the presence of torque near the proximal end of the device;
FIG. 6A illustrates a keyed stylet of the present invention, which includes a key feature at its distal end;
FIGS. 6B and 6C illustrate the relationship between the keyed stylet and the device, in an inserted and removed state; and
FIG. 7 is a flow diagram illustrating exemplary steps that may be performed to deploy and use the flexible brachytherapy device of the present invention in a resected cavity.



DETAILED DESCRIPTION
A flexible multi-lumen brachytherapy catheter of the present invention includes a plurality of loose lumens which are connected only at their distal ends. Reducing the binding of the lumens to a single connection permits individualized movement of the lumens, thereby decreasing the rigidity of the device and concomitantly increasing patient comfort and reducing the opportunity for shifting of the device following placement.
An exemplary embodiment of a brachytherapy device 10 is shown in FIG. 1 to include a flexible shaft 15 including a proximal end 2 and a distal end 4. The flexible shaft is comprised of a plurality of flexible dosing lumens 14a and 14b and an inflation lumen 17. Each dosing lumen is sized to accommodate one or more radiation sources. Providing multiple dosing lumens facilitates customization of radio-isotope treatment profiles. It should be noted that although only two dosing lumens are visible in FIG. 1, the present invention may be implemented with any number of dosing lumens. The inflation lumen 17 is coupled at a proximal end to a connector 19. The lumens 14a, 14b and 17 are made, for example, from a flexible material such as Nylon, Pebax, LDPE, Hytrel, PEEK. Each lumen 14a, 14b, 17 slideably extends through holes in the hub 16 and into openings which extend longitudinally into the rigid section 12. The openings in the rigid section are sized so that the exterior of each lumen is tightly received in its respective opening. The lumens may be fixedly attached to the rigid section 12 using an adhesive.
An inflatable member, shown as balloon 11, envelops at least a portion of the rigid member 12. In operation, the inflatable member is inflated by coupling the device to a source of a gas or other liquid via connector 19. The inflation liquid flows into the member via the inflation lumen 17. One or more inflation holes (not shown) extend through the inflation lumen and rigid section into the inflatable member. When the inflatable member is positioned in the resected cavity, the gas or other liquid is forwarded through the inflation lumen into the inflatable member to secure the member within the cavity. Once the member is inflated, connector 19 is detached from the source.
The hub 16 collects but does not connect the lumens; in some embodiments, the portion of the flexible shaft between a distal end of the hub and a proximal end of the rigid balloon section may be sheathed in a catheter, although it is not a requirement of the invention. The hub 16 includes one or more holes extending there through, where the holes in the hub have clearance tolerances that allow the lumens to independently move axially and rotatably within the hub.
Because the multiple lumens of the device 10 are flexible and independently moveable both axially and rotationally, forces experienced at the proximal end of the device 10 do not translate into movement at the distal end of the device. Reducing the propensity for movement of the shaft also increases the comfort of the patient.
FIG. 2 is a view of the brachytherapy device taken along the perspective of line A of FIG. l and illustrates an embodiment of a brachytherapy device of the present invention comprising a catheter 25 disposed between the distal end of the hub and the proximal end 34 of the rigid section 12.
FIG. 3A is a side perspective of the hub 16. In one embodiment the hub is formed from a photosensitive resin using stereolithography. The hub 16 includes a distal end 22 and proximal end 21. In FIG. 3A, the proximal end is shown to include a collar portion 36 and a body portion 38, wherein the collar portion has a circumference which is less than the body portion. It should be noted that the hub may take many forms; in a simplest form the hub may merely be fixed circumference tube. The hub is not limited to a cylindrical shape; rather embodiments wherein the hub comprises one or more angular features are further envisioned. A principle purpose of the hub is to gather the lumens. Thus, the only limitation to the hub is that it provides sufficient space to permit free rotational and axial movement of the lumens, while being small enough to serve the purpose of gathering the lumens.
In addition, while the hub may vary in exterior shape, there are a variety of ways in which the interior passageways of the hub can be arranged. For example, FIGS. 3B and 3C illustrate cross sections of the hub taken along the plane B of FIG. 3A. In FIG. 3B, a hub 116 includes a single opening extending there through. In FIG. 3C, a hub 216 includes multiple openings 41 which extend partially through the hub into a larger opening 43. As will be described in more detail below, the hub may also include a separate hole for accommodating a keyed stylet, although it is not a requirement of the invention.
FIG. 4A is a side view of the rigid section 12. The rigid section 12 includes one or more holes 22 for accepting lumens. As shown in dashed lines in FIG. 4A, the holes extend longitudinally towards the distal end 4 of the rigid section. In addition, in a preferred embodiment the rigid section 12 includes a lock or other feature 24 for engaging the keyed stylet. The rigid section 12, like the hub, may be formed from a photosensitive resin using stereolithography to define the openings.
FIG. 4B is a drawing of a cross section of the proximal end 34 of one geometrical embodiment of the rigid section 12. The rigid section 12 includes an opening 23, 25, 27 and 29 for accepting each of the dosing lumens. In addition, the rigid section 12 includes an opening 30 for accepting the inflation lumen 17. Each of the dosing lumens as well as the inflation lumen extends into one of the dosing lumen openings 23, 25, 27 and 29, where they are fixedly attached to the rigid section 12. The attachment to the rigid section is the sole attachment point of each dosing lumen to the device 10. One technique for affixing the dosing lumen to the dosing lumen opening is to apply adhesive to the distal end of the dosing lumen prior to insertion of the dosing lumen into one of the openings. Other methods of securing the dosing lumens, such as through the use of heat, mechanical locks, over-molding, etc, may be readily substituted herein as equivalents.
The geometry of the rigid section that is illustrated in FIG. 4B enables the use of 4 dosing lumens in a brachytherapy device, thus expanding the variety of isodose profiles which may be delivered during treatment. Radioactive material may be loaded into any or all of the dosing lumens, in different amounts and in different positions along the rigid section to satisfy a variety of dosing needs. It should be noted that FIG. 4B is merely an example of one multi-lumen dosing geometry; other geometries may be substituted by one of skill in the art herein without affecting the scope of the invention. The geometries include, but are not limited to, the use of the geometry shown in FIG. 4B with one or more of the lumen openings 29, 25, 27 or 23 removed; such geometries include the geometry of FIG. 4C to support one inflation lumen and one offset dosing lumen, the geometry of 4D which supports two offset lumen and the geometry of FIG. 4E, supporting three offset lumen. Other geometries can be substituted herein without affecting the scope of the present invention. It is further noted that although the inflation lumen 30 is shown in a particular position, there is no limitation as to the positioning of the inflation lumen so long as one or more openings are provided from the inflation lumen opening 30 into the inflatable member 11.
FIGS. 5A and 5B show brachytherapy devices designed according to the concepts of the present invention, having various forces applied thereto. Devices 100 and 200 are manipulated to provide a respective clockwise and counter clockwise torque upon the catheter; however, a rotation of less than ninety (90) degrees at the proximal end transmits no torque to the rigid section 12.
Accordingly, a multi-lumen brachytherapy solution with increased flexibility has been shown and described as having several advantages over the prior art. The flexibility of the multi-lumen catheter reduces the chance that external forces, acting upon the device will cause a shift in position of the device subsequent to placement. Because device placement remains stable following insertion, its location can be relied upon in temporally spaced, multi-dosing treatment plans. In addition, because the increased flexibility increases patient comfort, the likelihood that the device remain in situ during the course of treatment is increased.
Keyed Stylet Feature
While there are several advantages to the flexibility of the multi-lumen brachytherapy device of the present invention, this flexibility presents a problem when controlled insertion of the device into patient is required. Controlled placement of the device requires the device to have a certain amount of rigidity.
Accordingly, according to one aspect of the invention and referring now to FIG. 6A, rigidity of the device can be provided during placement using a keyed stylet 18. The keyed stylet 18 includes a shaft 30 with a key feature 32 on a distal end and a tab 31 on the proximal end. The key feature 32 is formed to engage the lock 24 at the proximal end of the rigid feature 12. The keyed stylet extends from the proximal end of the hub into the lock of the proximal end of the rigid section 12. Tab 31 is formed so that it extends away from the hub when the key feature engages the lock, thereby facilitating access to the tab for removal of the stylet once the device 10 is in place in the resected cavity. By keying the rigid section and connecting it with the hub 16, a one to one rotation of the device can be obtained. Although a key feature/lock combination is shown, it should be appreciated that equivalent devices for releasably mating the stylet to the rigid shaft may readily be substituted herein. For example, a distal end of the stylet may extend into any feature of the rigid section, or may be formed to hook or latch onto some feature of the rigid section. Other embodiments, where the stylet extends up to, but not into, the rigid section are also envisioned.
FIGS. 6B and 6C illustrate the keyed stylet and the device, prior to and following insertion of the stylet through the hub and into the rigid member. As shown in FIG. 6B, the length of the stylet is generally selected to provide control of the device during placement; the length may therefore range from a maximum length equal to the entire length of the dosing lumens to a minimum length equivalent to the depth of the resection cavity. The tab 31 is a feature which allows the surgeon to easily withdraw the stylet once the device 10 is in place. Although a tab 31 is shown, any means that provides extraction, such as a loop or the like could be readily substituted herein. In addition, other embodiments in which the stylet is latched, spring loaded or the like could be substituted herein as equivalents. In one embodiment, the stylet is formed from a stiffening material such as plastic, metal or combination, although any material that provides a rigidity sufficient to rotate the device can be readily substituted herein.
As shown in FIG. 6C, the key feature of the stylet is inserted into the proximal end of hub 16, and extends into the lock 24 at the base of the rigid section 12. In one embodiment, the hub may include a slot for accepting the tab 31. In other embodiments, the tab 31 will sit above the hub, as shown in FIG. 5. One advantage of having the tab extend over the hub is that it provides a protuberance which is associated with the geometry of the device; for example, if the surgeon is aware that the lock is 24 is positioned relative to any of the geometries of FIGS. 4A-4E, the surgeon can position the device so that the geometry best suits a radiation profile suitable for the extracted lesion. However the tab is arranged, once the stylet key feature is in the lock 24, at least a portion of the device 10 has sufficient rigidity for easy manipulation.
FIG. 7 is a flow diagram of an exemplary process 500 that may be performed to use the device of the present invention. At step 510 the keyed stylet is inserted through the hub such that the key feature engages the lock. As a result, the device is rigid and may be inserted into a patient. The stylet may be packaged separately from the brachytherapy device 10 and inserted by the doctor prior to insertion, or the stylet maybe inserted into the device as part of the manufacturing process. Once the stylet is introduced into the device, the device has sufficient rigidity for placement. At step 512 the device is inserted into the resected cavity, and the surgeon may rotate the device to a desired location for treatment.
At step 514, the stylet is removed. The removal of the stylet releases the rigidity of the device 10, and the resultant flexible multi-lumen brachytherapy catheter is resistant to movement caused by external forces.
In general the placement of the catheter is temporally spaced from the treatment of the patient using the catheter. Thus, once the patient is ready for treatment, the radiologist can use any of the lumens of the multi-lumen catheter to implement a treatment plan customized for the individual. Because of the flexibility of the design, the radiologist can have increased confidence in the stability of the placement of the device. However, should the radiologist need to adjust the device, he or she can easily and accurately modify the device positioning by re-inserting the key through the hub and into the device.
Accordingly, a flexible, multi-lumen brachytherapy device has been shown and described which has several advantages over the prior art. The flexibility of the design decreases intermittent device movement while increasing patient comfort. A novel keyed stylet can be selectively inserted to increase the rigidity of the device as needed. The ability to dynamically modify the rigidity of the brachytherapy device provides a comprehensive brachytherapy solution that satisfies concerns of the patient, the surgeon and the radiologists.
Having described exemplary embodiments of the invention, it should be appreciated that the present invention may be achieved using other components to perform similar tasks. For example, although an example of a keyed stylet has been shown, any rigid structure, such as a pin or rod, adapted for removable mating with the flexible catheter may be substituted herein as an equivalent. Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications can be made that will achieve some of the advantages of the invention without departing from the true scope of the invention. These and other obvious modifications are intended to be covered by the appended claims.

## Claims

1. An apparatus for treating a proliferative disorder in a patient comprising:
an implantable rigid member having a proximal end and a distal end, the implantable rigid member comprising a plurality of lumen openings extending longitudinally within the implantable rigid member, and wherein the proximal end of the implantable rigid member defines a lock opening;
a plurality of separate flexible dosing lumens, each having a proximal end and a distal end, wherein each distal end of each dosing lumen extends into a different one of the plurality of lumen openings of the implantable rigid member and wherein the distal end of each dosing lumen is spaced apart from the proximal end of the implantable rigid member;
a hub discrete from the implantable rigid member and disposed about the plurality of dosing lumens, wherein the hub defines a slot defined by an outer circumferential surface of the hub; and
a stylet comprising a shaft having a distal end and a proximal end and a key feature at the distal end of the shaft, wherein an exterior of the shaft has a uniform shape along a length of the shaft from the proximal end of the shaft to the distal end of the shaft and wherein the key feature removably mates with the lock opening of the implantable rigid member, and wherein the proximal end removably mates with the slot defined by the hub, such that mating engagement between the stylet and both the lock opening and the slot allows for a one-to-one axial rotation of the implantable rigid member and the hub, whereby an axial rotation of the stylet causes a corresponding axial rotation of the implantable rigid member and the hub.

2. The apparatus of claim 1, wherein the stylet further comprises a tab at the proximal end and wherein the shaft extends between the key feature and the tab.

3. The apparatus of claim 1 further comprising an implantable inflatable member, the implantable inflatable member enveloping at least a portion of the rigid member.

4. The apparatus of claim 1 wherein the hub comprises a plurality of holes extending there through, wherein each of the plurality of holes is sized such that each of the plurality of dosing lumens is configured to independently move axially and rotatably within the hub.

5. The apparatus of claim 1 wherein the hub comprises a collar portion and a body portion, a circumference of the collar portion being less than a circumference of the body portion.

6. The apparatus of claim 1 wherein the stylet comprises a tab feature located at an end of the shaft.

7. The apparatus of claim 1 wherein each of the dosing lumens is fixedly attached to an interior of a respective opening of the implantable rigid member.

8. The apparatus of claim 1 wherein the stylet is rigid such that rigidity of the stylet allows the stylet to selectively modify the rigidity of the apparatus and imparts rigidity to the at least a portion of the apparatus.

9. The apparatus of claim 1, wherein the hub defines at least one hole extending therethrough, wherein the plurality of dosing lumens are disposed in the at least one hole.

10. The apparatus of claim 1, wherein the hub defines a plurality of holes extending therethrough, wherein at least one of the plurality of dosing lumens are disposed in each of the plurality of holes.

11. An apparatus for treating a proliferative disorder in a patient comprising:
an implantable rigid member having a proximal end and a distal end, the implantable rigid member comprising a lumen opening extending longitudinally within the implantable rigid member, the implantable rigid member further comprising a lock opening defined by the proximal end;
a dosing lumen having a proximal end and a distal end, wherein the distal end of the dosing lumen extends into the lumen opening of the implantable rigid member;
a hub discrete from the implantable rigid member and disposed about the dosing lumen, wherein the hub defines a slot defined by an outer circumferential surface of the hub; and
a stylet comprising a shaft having a distal end and a proximal end and a key feature at the distal end of the shaft, wherein the key feature removably mates with the implantable rigid member at the lock opening, and a portion of the proximal end mates with the slot of the hub, such that mating engagement between the stylet and both the lock opening and the slot allows for a one-to-one axial rotation of the implantable rigid member and the hub, whereby an axial rotation of the stylet causes a corresponding axial rotation of the implantable rigid member and the hub.

12. The apparatus of claim 11, wherein the stylet further comprises a tab at the proximal end and wherein the shaft extends between the key feature and the tab.

13. The apparatus of claim 12, wherein the key feature of the stylet is added for insertion in the lock opening of the implantable rigid member.

14. The apparatus of claim 11 further comprising an implantable inflatable member, the implantable inflatable member enveloping at least a portion of the implantable rigid member.

15. The apparatus of claim 11, wherein the hub comprises a hole extending there through, wherein the hole is sized such that the dosing lumen is configured to independently move axially and rotatably within the hub.

16. The apparatus of claim 11, wherein the stylet comprises a tab feature located at an end of the shaft.

17. The apparatus of claim 11, wherein the stylet is rigid such that rigidity of the stylet allows the stylet to selectively modify the rigidity of the apparatus and imparts rigidity to the at least a portion of the apparatus.