Abstract:
A vaginal brachytherapy applicator is versatile to different anatomies and more comfortable to the patient than prior applicators. An inflatable balloon on a shaft may be inelastic or elastic. In one embodiment the shaft is rotatable relative to the balloon for enabling a ring or band of dose delivery, for versatility in radiation placement. Alternatively, the source can be rotated and pulled back within a stationary shaft. An adjustment is provided for reducing the length of balloon that inflates, to accommodate different anatomies and positions. Although isotope radiation sources can be used in the applicator, an electronic source is preferred, and the system and method include procedures for using the applicator with an electronic source.

Description:
This application is a continuation-in-part of application Ser. No. 10/464,140, filed Jun. 18, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention concerns radiation therapy, especially for treating tissue which may have malignancies, and in particular the invention relates to an applicator for delivering radiation to a vaginal cavity and/or to adjacent tissue post full/partial hysterectomy for surgical treatment of cancer. Treatment of endometrial cancer is encompassed by the invention. 
     Vaginal or endometrial cancer, or malignancies in adjacent tissues, have been treated by applicator cylinders designed to receive radioactive isotopes. Applicators of this general type are shown, for example, in U.S. Pat. Nos. 5,913,813 and 6,413,204. Even though the applicator cylinders are sized to the vaginal cavity or adjacent anatomy, these types of applicators have often been uncomfortable or painful on insertion and once inserted have failed to provide a good fit. Ideally, the tissue should be positioned closely against the applicator. The conventional applicator can cause discomfort, inconvenience and less than ideal treatment in many cases. Such devices also lack flexibility in dose delivery profile. Basically, prior art applicator cylinders have included a straight lumen down the center through which radioactive seeds were delivered. 
     SUMMARY OF THE INVENTION 
     The invention is an improved applicator for gynecological brachytherapy, more comfortable to the patient on insertion and in use, more versatile, and optimally with capability of rotating a radiation emitting device to produce a ring or band of irradiated tissue. The device has a main shaft to which is secured or connected an inflatable balloon surrounding the distal end of the shaft which will be inserted into the body of the patient. The shaft may have alternate configurations for variations in positioning a radiation source, or to accommodate a range of therapeutic treatments. Multiple guides for the radiation source(s) can be included, as also disclosed in copending application Ser. No. 10/464,140, incorporated fully herein by reference. The invention encompasses use of isotopes, but especially in preferred embodiments, embraces application of variable voltage and/or current to a switchable electronic miniature x-ray source (or to several sources) in order to optimize a treatment plan. Also, the system can employ feedback control in real time, to feed actual sensor-determined radiation values back to a controller to adjust and control the dose delivered by the electronic radiation device, to achieve a desired dose profile even in a cavity of irregular shape, utilizing directionality of radiation if necessary. 
     In one preferred implementation of the invention, a brachytherapy applicator comprises an inflatable balloon, with a shaft extending into the interior of the balloon, the shaft having a conduit for inflating the balloon by admitting fluid to the balloon&#39;s interior. A source of ionizing radiation for delivery of radiation is affixed to or retained at the distal end of a flexible catheter or a rigid wand, depending on the application at hand. The source catheter or wand is contained in or received in the applicator shaft and is guided into the space within the balloon. A fluid tight seal, such as by a bonded joint, is provided at the proximal end of the balloon to seal the balloon against the exterior of the shaft in this embodiment. At the interior of the proximal end of the shaft in this preferred embodiment, an O-ring seal seals the shaft to the exterior of the flexible catheter or rigid wand comprising the radiation source, permitting rotation as well as axial movement between the radiation source structure and the shaft without substantial fluid leakage. 
     The radiation source may be omni directional or direction specific to suit the application. In one embodiment a radio opaque source guide including a radiation window is provided between the shaft and the source catheter or wand to control the directionality of emitted radiation. The radiation source and source guide can be rotatable within the shaft without substantial loss of fluid from the interior of the balloon. A preferred form of the shaft is configured to allow pullback of the radiation source. 
     In use, the balloon on the shaft is placed in a gynecological cavity with the balloon deflated, the radiation source is inserted, and once in place, the balloon is inflated (in some embodiments the balloon can be put in place and inflated before the radiation source is inserted). With the ionizing radiation source in the shaft, the source can be rotated and/or moved axially by machine or by hand, manipulated from a position outside the patient to control the locations from which the radiation is to be emitted, and the directions in which the radiation is to be directed. 
     In the various applicator embodiments described, the distal end of the applicator shaft is preferably affixed to the distal end of the balloon, or includes a rotary bearing connecting the distal end of the shaft to the distal end of the balloon, so as to permit rotation while supporting the balloon on the shaft. 
     The distal end of the shaft or source guide (most remote from the controller as used herein) in one embodiment is bent to an oblique angle for emitting the directional radiation outwardly and axially from the applicator, with capability of rotating the shaft relative to the balloon; alternatively, directional radiation can be emitted from a straight shaft located generally centrally. The shaft of an applicator refers to that element of the applicator that connects to the balloon (rotationally or not) and which provides an internal lumen or guide for receiving the radiation source. 
     Another preferred feature of the invention is a means for adjusting the size of the inflated portion of the balloon. This can be accomplished using a slidable tubular sheath over the shaft that slides axially relative to the shaft, and when moved forward (distally), covers a desired portion of the balloon from the proximal end of the balloon so as to prevent or limit expansion of the balloon in the sheath-covered portion. The expanded length of the balloon is thus limited as desired. This adjustment accommodates different anatomies of different patients, as well as adjusts for different regions within the anatomy. 
     As noted above, the source of ionizing radiation in a particular preferred embodiment is an electronic switchable x-ray source, which is not only switchable on/off but is adjustable as to voltage and current, and thus as to x-ray penetration depth and cumulative dose delivered. This affords attaining a much more accurate delivered dose profile than can be obtained using prior art methods since the control of radiation allows accommodation of differences in distance from source to tissue and differences in dose delivered to different tissue regions. It also provides a more flexible and anatomy-conforming applicator. 
     When the anatomy demands, or when the morbidity requires, an embodiment is provided in which the shaft and other elements of the apparatus can be bent to facilitate entry into the uterus after dilation. For example, the shaft may be formed in a continuous curve, or may comprise a deformable element, for example annealed metal, which may be formed by the doctor to accommodate the patient&#39;s anatomy. 
     It is thus among the objects of the invention to greatly improve efficiency, reliability, versatility, patient comfort and dose accuracy in brachytherapy radiation within the vaginal cavity and adjacent anatomy. These and other objects, advantages and features of the invention will be apparent from the following description of preferred embodiments, considered along with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view in cross-section of a preferred embodiment of the invention. 
         FIG. 2  is a side view in cross-section of an applicator of the invention, including a slidable tubular sheath covering a portion of the expandable balloon, limiting its expansion. 
         FIG. 3  is a side elevation view of a curved embodiment of the applicator similar to that of  FIG. 1 , in partial cross section. 
         FIG. 4   a  is a side elevation view of a radio opaque outer element of a source guide with a window through which radiation may be directed. 
         FIG. 4   b  is a side elevation view of the inner element of a radio-opaque source guide with a window through which radiation may be emitted. 
         FIG. 4   c  illustrates how the source guide elements can be assembled and how the window depicted in  FIGS. 4   a  and  4   b  may be adjusted to cooperate in obtaining a desired window through which a controlled beam of radiation is to be omitted. 
         FIG. 5  depicts a side view of an alternate embodiment of the invention in partial cross-section, comprising a shaft with a curved channel to direct radiation distally and rotatably about the shaft axis. 
         FIG. 5   a  is a side view of an alternative bearing configuration in partial cross section. 
         FIG. 5   b  is a view similar to  FIG. 5  but showing another embodiment. 
         FIG. 6   a  and  6   b  show side and axial views in cross-section of apparatus of the invention that includes suction applied to the distal end of the applicator to draw of accumulated fluid or exudate. 
         FIG. 7  shows a portion of a patient&#39;s vaginal anatomy in coronal section with early stage cancer (shaded) at the mouth of the cervix. An applicator of the invention positioned within the vagina. 
         FIG. 8   a  shows the patient&#39;s anatomy with advanced cancer in coronal section with an applicator of the invention positioned within the vagina and partially into the uterus. 
         FIG. 8   b  shows the anatomy of  FIG. 8   a  in medial sagittal section, again with an applicator within the vagina and a portion of the uterus. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  depicts a basic embodiment of the invention. A radiation source catheter or wand  100  has a radiation source  101  at its distal end. The catheter or wand  100  is shown assembled within a shaft  200  of an applicator  208 . The shaft  200  comprises a tubular body with a balloon  300  at its distal end  205 . The distal end of the shaft  200  is bonded to the balloon at its distal extremity, and bonded to the balloon proximal extremity at  206 . 
     At the proximal end  207  of the shaft  200  is a conventional applicator hub (not shown) as is common in radiation applicators, including a port  201  for balloon inflation fluid in communication with a fluid outlet  202  within the balloon, and a seal receptacle  203  for an O-ring  204 . The O-ring  204  maintains a movable seal between the shaft  200  and the catheter  100  in this embodiment, allowing both rotation and translation of the catheter within the shaft without loss of balloon inflation pressure. 
       FIG. 2  shows an optional tubular sheath  210  placed over and coaxial with the shaft  200  and proximal end of the balloon  300 , on an applicator  208   a.    
     The sheath  210  may be adjusted and positioned axially as desired along the body of the shaft  200  in order to limit the inflated length of the balloon. The sheath  210  can be held in position by a nut  211  and a tapered thread  212  at the split, proximal end of the sheath  210 . When positioned as desired, the sheath  210  and nut  211  are rotated relative to one another such that the tapered thread causes the split end of the sheath to tighten onto the shaft  200 . The sheath may be rigid and of metal (stainless steel, for example) or engineering plastic and flexible (PVC, Nylon). Advantageously, it may be radio-opaque (e.g. barium loaded if plastic). In an alternate embodiment (not shown) a latch can be provided on the sheath to engage with an element of the shaft or of a hub to position the sheath relative to the shaft. 
     The balloon  300  can be either elastic or inelastic in nature; that is, it can be of material to substantially conform to tissue, or material to form a generally rigid predefined shape. In use, the balloon preferably abuts the patient&#39;s tissue to be treated. If the nature of the cavity being irradiated is irregular or rigid, an elastic construction is usually preferred. A suitable material is silicone rubber, and of such a thickness that inflation pressure will cause expansion of the balloon to substantially fill the irregular cavity to be irradiated. If in contrast, the cavity to be irradiated is of fairly uniform geometry, or if the tissue is highly compliant, then an inelastic balloon might be preferred. Such a balloon, constructed for example of PET or polyurethane, can be fabricated to expand to a predetermined shape, and if properly proportioned, usually can deform the tissues to be treated such that they conform to the balloon geometry. A balloon that assumes a known (fairly rigid) shape has been important in use of isotope radiation, with the isotope source positioned centrally in the balloon to produce a known distance to tissue and uniform dose distribution. Such is one embodiment of this invention, and can be considered as represented in  FIGS. 1 and 2 , and also in  FIG. 3 ,  6   a - 6   b ,  7  and  8   a - 8   b . With a controllable electronic x-ray source, however, more latitude is permitted and irregular shapes can be treated, with conforming balloons. 
     Generally, it is preferable that the position of the radiation source within the balloon be known as precisely as possible. Therefore, it is usually advantageous that the balloon  300  be secured to or supported on the shaft of the applicator at both distal and proximal balloon extremities. There may be situations, however, where the geometry of the anatomy to be treated and that of the balloon are sufficiently predictable that anchoring of the balloon to the shaft only at the proximal end of the balloon is adequate for proper control of therapy. 
     Depending on the anatomy being treated, and perhaps its surrounding anatomy, it may be preferred that the applicator be curved as shown with the applicator  208   b  in  FIG. 3 . As shown the body of the shaft  301  has a continuous curve, although the form can be arbitrary to suit the anatomy of the patient. If desired, the body of the shaft  301  can be of deformable material such as annealed stainless steel, and bent to suit by the radiation therapist. Further, it could be of Nitinol according to the catheter teachings of U.S. Pat. No. 4,665,906. Use of a flexible source catheter  100  permits the radiation source to be positioned at will along the tubular bore of the shaft  301 . A situation in which a curved applicator is preferred is shown in  FIG. 8   b  and discussed below. 
     The preferred radiation source of this invention is a miniature x-ray tube  101 , positioned at the end of a cable catheter or wand  100 . An example of such an x-ray source is described in U.S. Pat. No. 6,319,188. Generally, they consist of a flexible, high-voltage cable (as part of the catheter  100 ) connected to a power source and controller at its proximal end and to the small x-ray tube at its distal end. The x-ray tube has a cathode which can be caused to emit electrons (for example by heat) at its proximal end and a target anode at its distal end. The voltage between the cathode and electrode accelerates the electrons emitted by the cathode such that they impact the anode creating x-rays. The spectrum of energies produced is related to the voltage applied between the anode and cathode and the target material used. It is this anode to cathode high voltage (as well as current control) that provides the option for control of the radiation emitted from such an x-ray device as compared to a radio-isotope source which always emits in a known and unchangeable manner. 
     The shape of the anode, and its structure and shielding, determine the directionality of the x-rays emitted. They may be omni directional, or they may be directed radially or axially, or a combination thereof. Anode shaping is well known by those skilled in the art of x-ray generation apparatus. The penetration of the x-rays in tissue is directly related to the voltage accelerating the electrons, and the cumulative dose may be controlled by x-ray source beam current or dwell time at positions within the body of the patient. Current can be varied in the tube to control cathode emission. It should also be noted that dosimeters can be placed on the balloon at plural locations, thus to be directly adjacent to the tissue, and can sense dose from the source so that the dose being delivered to different tissue regions being treated is known. This enables control of dose delivered to all regions in an irregularly-shaped cavity and balloon; feedback control is disclosed in copending application Ser. No. 10/464,140, incorporated herein by reference. 
     On occasion, it is preferable to shape the emission field of the x-ray tube by shielding the output of the source  101  rather than by anode design. An example of such shielding is illustrated by a directional source guide  400  in  FIGS. 4   a - c . The directional source guide  400  is inside the lumen of an applicator shaft.  FIG. 4   a  shows in side elevation the outer, tubular, radio opaque shield sleeve  401  having one closed end and a window  402  which is open for an arbitrary length and an arc B.  FIG. 4   b  shows an inner, tubular, radio-opaque sleeve  403  having one closed end and a window  404  which is open for an arbitrary length and an arc A. The inner bore of the shield sleeve  401  accommodates the outer diameter of sleeve  403 . The outer diameter of the sleeve  401  is accommodated by the inner diameter of the shaft  200  and the O-ring seal  204 , if the applicator is constructed as in  FIG. 1 . The inner bore of the smaller sleeve  403  accommodates the source catheter  100 . When the inner and outer sleeves  401  and  403  are assembled, they comprise the source guide  400  shown in  FIG. 4   c . Windows  402  and  404  may be positioned rotationally and axially to create a clear window  405  of arbitrary size for desired radiation emission as shown in  FIG. 4   c . This composite window  405  may then be directed toward the tissue to be irradiated. The relative positions of sleeves  401  and  403  may be fixed by a tapered thread and nut similar to that shown in  FIG. 2 , as may the inner sleeve  403  in relation to the source catheter body  100 . Positioning and movement of the source catheter and of the source guide sleeves  401  and  403  can be controlled by a program driven machine. With this source guide, stray radiation is eliminated, protecting healthy tissue or tissue especially susceptible to radiation damage, such as the bowel. Such a source guide may be fashioned from barium loaded engineering plastic. Note that intermediate elements between the source catheter and the shaft may necessitate additional seals to prevent inflation fluid leaks, depending on the nature of the inflation port. 
     Directionality and control of the position at which radiation is directed can be achieved in other ways. For example, the x-ray  101  source within the catheter  100  can simply be shielded by a radio opaque shield or coating on the x-ray tube or surrounding catheter, allowing radiation to be emitted only in a single cone or shaft, and the axial position and rotational orientation of the catheter can be manipulated in a selected pattern of movement so as to place the proper dose at each region of the tissue. 
       FIG. 5  depicts an embodiment of an applicator  505  in which a base portion  506  of the applicator terminates near Image Page  3  the proximal end of the balloon  300 , and a cupped, separate element or bearing  500  is affixed to the distal extreme of the balloon  300 , for example by bonding. A shaft or source guide  501  has a branch  502  forming a curved guide lumen, closed at its distal end, and an axial extension  503  to cooperate with the cup  500  to maintain the position of the shaft or source guide  501  relative to the distal end of the balloon. If necessary to maintain axial position of the cup  500  relative to wand guide  501 , a groove  504  (shown in alternate detail,  FIG. 5   a ) can be provided in the axial extension  503  into which the rim of the cup  500  can be heat formed after assembly of the shaft  501  into the base member  506 . The guide  501  can be rotated within the shaft or base  506  such that the branch describes a circle within the balloon  300 , directing radiation outward in a conical or radial manner, when the source catheter is in the branch. Such a construction would be useful in directing axial radiation into the fornices of the vagina, or for irradiation of such tissue alongside the site of hysterectomy. 
       FIG. 5   b  shows another embodiment wherein the shaft  501  is not rotatable but has two branches  502  and  507  into which the source can be placed. Here the end of the shaft  501   a  is fixed to the balloon. This forked shaft  501   a  can have the two branches or forks  502  and  507  at 180° or at any other selected angle, to protect, for example, the bladder and bowel by providing selected directional radiation. The source catheter (not shown) can have a slight bend near its tip so it can be steered into one channel ( 502 ,  507 ), then the other. 
     The applicator embodiment  607  of  FIGS. 6   a  and  6   b  comprises an optional vacuum channel to evacuate exudate or other fluids from the region near the distal end of the balloon  300  through a port  605  in response to vacuum drawn on a port  606  at the proximal end of a multiple-lumen shaft  600 . Exudate or fluid is drawn through an annular passage  604  between the catheter  100  and the shaft  600 &#39;s inner diameter. The ports  605  and  606  communicate through this annulus. To provide inflation of the balloon, a lumen  601  is provided in the wall of the shaft  600 , terminating at a port  603  within the balloon, and at inflation port  602  near the proximal end of the shaft  600 . 
     A preferred method of use of the invention apparatus is illustrated in  FIG. 7 .  FIG. 7  shows in frontal coronal section the applicator  505  of  FIG. 5  in the vaginal space of the patient, positioned to treat early stage cancer at the mouth of the cervix  700 , the cancer being indicated by shading near the distal end of the applicator. In use, the deflated applicator  505  is inserted into the vagina. The source catheter  100  is then inserted into the applicator, and the balloon is inflated, anchoring the applicator in position in the vagina. The controller and power supply (not shown) are connected to the source catheter  100  (also not shown), and switched on. Then treatment proceeds. After treatment is concluded, the system is switched off, the balloon deflated, and the applicator removed. 
     The treatment plan is prescribed by the physician prior to application of radiation. If therapy is to be x-ray in nature, the plan may comprise specification of dose intensity, penetration and dwell of the radiation source by position from which radiation will be emitted and the direction of emission or shielding utilized to protect healthy anatomy. Therapy may also include verification of dose delivered and feedback from sensors placed near the anatomy being treated, as noted above, on or in the applicator, or on external anatomy of the patient or at interstitial positions. Preparation of a plan of this sort and subsequent treatment to plan are discussed thoroughly in co-pending application Ser. No. 10/464,140, filed Jun. 18, 2003. 
     A further illustration of the use of apparatus of the invention is shown in  FIGS. 8   a  and  8   b .  FIG. 8   a  is a frontal coronal section through the vagina showing later stage cancer with involvement of the uterus and pelvic structure to the patient&#39;s left of the vagina.  FIG. 8   b  shows a sagittal section of the anatomy to be treated. The inflated, curved applicator  208   b  of  FIG. 3  is shown positioned in the vagina, and partly into the uterus. In use, the cervix is dilated and the applicator is properly positioned. The source catheter is then inserted and the balloon  300  inflated to abut the tissue and substantially fill the space around the radiation source, anchoring the applicator. The controller and power supply (not shown) are connected to the source catheter  100 , and switched on. Then treatment proceeds. After treatment is concluded, the system is switched off, the balloon deflated, and the applicator removed. 
     Another embodiment of the applicator of the invention, not illustrated, can have a balloon with a generally elliptical cross section, short front-to-back and shielded at front and back ends to protect the bowel and bladder, which are indicated at  801  and  802  in  FIG. 8   b.    
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.