Abstract:
Brachytherapy treatment of a patient&#39;s lung tissue following resection is effected using a balloon applicator which is inserted, normally through the same opening used for the surgery, through the chest wall and into the cavity. The lung and chest openings are closed around the applicator and generally sealed around the applicator. A suction port is provided, in a suction circuit of the applicator, to withdraw fluid from the pleural cavity, at intervals as needed, to assure that the lung can be inflated. Different embodiments of suction circuits are disclosed. A bronchial applicator and method are also disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention pertains to minimally invasive surgery of the lung. In particular, it applies to application of brachytherapy techniques directed primarily to lung or pleural tissue surfaces exposed by or created as a result of tumor resection or the presence of primary cancer of the pleura. As with other tumor resection procedures, and even when pathology shows “clear” margins, there is potential for disease recurrence from diffuse proliferative disease in the resected surfaces. Balloon brachytherapy as an adjuvant follow-up to resection has been shown to reduce the likelihood of such recurrent disease. 
         [0002]    Recent advances in surgical treatment of proliferative diseases of the lung include endoscopic procedures conducted through, and directed to lesions near the bronchi, and alternatively, video-assisted, minimally-invasive thoracic surgery directed to more peripheral disease and performed through incisions providing access to the thoracic cavity. 
         [0003]    Today with early stage carcinoma of the lung, particularly in peripheral portions of the lung, treatment consists of resecting a wedge-shaped portion of lung through small incisions between adjacent ribs. If a wedge resection is inadequate to excise the entirety of the tumor, a lobectomy may be performed, removing a complete pulmonary lobe. Visualization is provided by camera or conventional fiber optic means mounted on a thoroscope and monitor display, although other state-of-the-art modalities can be used. Percutaneous or other methods or small incisions are used to introduce the necessary instrumentation, and with newer, minimally invasive techniques, conventional rib spreading is not required. The absence of rib spreading greatly reduces pain and hastens patient recovery, but narrows instrument access to a few small, discrete points on the rib cage. In order to provide adjuvant brachytherapy, methods and apparatus are needed that are compatible with the methods described above, and preferably without requiring additional access beyond that already established during resection. 
         [0004]    With the intrabronchial approach to treatment of obstructions or lesions, a flexible bronchoscope with a working channel is generally employed in the affected bronchus while the remaining bronchial tree provides intraoperative ventilation. The bronchoscope also comprises either camera or fiber optic means to provide monitor display. Other instrumentation, preferably including that for follow-up brachytherapy, must be flexible, and of appropriate diameter for operation from within the working channel in order to be compatible. Extra or intrabronchial procedures often involve removal of a diseased section of bronchus, after which the exposed ends are usually approximated, either by suture or staple methods. Adjuvant brachytherapy may also be indicated after extra or intrabronchial surgery. 
         [0005]    Brachytherapy practice traditionally comprises positioning a radiation source within target tissue and delivering a therapeutic dose of radiation, often from within a balloon, without overdosing either target or adjacent tissue. One particularly useful class of radiation sources are miniature electronic x-ray tubes which may be switched on and off at will, or which can be modulated with respect to either penetration depth (by controlling acceleration voltage of the x-ray tube) or dose intensity (by controlling filament current). These tubes are usually mounted at the end of a power supply cable and can emit isotropically or can be directional, emitting through a predetermined solid angle. One reference describing the principles and construction of such tubes is  Atoms, Radiation and Radiation Protection , Second Edition, John E. Turner, Ph.D., CHP, 1995, John Wiley &amp; Sons, Section 2.10. By contrast, isotope sources cannot in principle be modulated, and in addition require both isolation of the patient during radiotherapy and special facilities and apparatus to assure safety of personnel. 
         [0006]    A minimum therapeutic absorbed dose (the prescription dose) is selected by the therapist to be delivered to all of the target tissue. Because dose generally decreases exponentially with distance from the source, accurate dose delivery is complicated and automated treatment planning is generally employed to assure delivery of a dose to the target tissue which is at least equal to the prescription dose, but which is also within allowable limits, thus avoiding substantial necrosis of normal tissue. The prescription dose may of necessity vary depending on the proximity of the source to radiation sensitive structures within the anatomy. Examples would include the skin, heart or other organs, and bone. Treatment planning is usually automated based on known radiation source parameters, prescription parameters, and geometry as determined by conventional imaging of the apparatus within tissue. Planning usually precedes the treatment delivery. 
         [0007]    A useful device for controlling radiation intensity is an applicator, preferably a balloon applicator. Balloon applicators generally determine the interior shape of the target tissue (the resection cavity) and position the radiation source at a controlled distance from the tissue to be treated, thus defining treatment geometry and reducing the radiation intensity exponentially from spatial considerations. Several other means are available to moderate the absorbed dose delivered to the tissue. As noted above, the acceleration voltage applied to the x-ray tube can be used to limit the penetration depth of the radiation. The filament current can be reduced to lower emitted intensity, or in fact, to eliminate emissions altogether. Once output emission characteristics are determined by selection of x-ray tube input parameters, shielding can be used to reduce radiation intensity, or to control the direction of emissions, statically or dynamically as therapy progresses. Such shielding and attenuation methods for x-ray tubes are described in copending application Ser. Nos. 11/385,255, 11/471,277 and 11/471,013, each of which is incorporated herein in their entirety by reference. 
         [0008]    Balloon applicators are known, for example those described in U.S. Pat. No. 6,413,204. In general, such applicators comprise a balloon mounted on a shaft proximate the distal end of the shaft, and further comprise at least one source guide to position the source at a known distance or distances from the balloon (and tissue cavity) surface. Fluid circuits can be provided communicating from outside the patient to the interior of the balloon for inflation purposes, or to outside the shaft and/or balloon for example for suction purposes or administration of anesthetic or therapeutic agents. 
       SUMMARY OF THE INVENTION 
       [0009]    After a lung wedge resection or lobectomy, and preferably after pathology determination of clean margins, adjuvant brachytherapy may be indicated. If so, an applicator with a balloon is positioned within the resection cavity as the lung is closed, but before the chest cavity is closed, with the applicator shaft extending outside the patient. (Optionally, the skin may be closed as well, but it may be desirable to close the skin later such that pleural access is available for suturing or stapling after removal of the brachytherapy apparatus.) For this minimal access resection method (usually between the ribs), a substantially rigid applicator shaft is likely preferred. The balloon is then inflated. If necessary to close the lung effectively, the bronchoscopic methods of U.S. Patent Application Publication No. 2005/0137714 may be employed. 
         [0010]    Once the balloon is properly positioned and inflated, the lung will likely self-expand or may be gently inflated. If desired, the chest may be imaged using conventional or state-of-the-art methods to assure that the lung tissue closely conforms to and surrounds the balloon as closely as possible. Advantageously, a fluid suction circuit in the applicator leading from outside the patient to outside the shaft of the applicator in communication with the pleural cavity is helpful for preventing or reducing pneumothorax, and facilitating proper lung inflation. The port intended to open into the pleural cavity is preferably adjustable along the shaft of the applicator such that it may be properly positioned and suction can be applied as desired. Alternatively, the suction circuit can comprise a valve, and/or the circuit can be used to instill therapeutic agents. 
         [0011]    When the apparatus is properly situated and the anatomy is in conformance with the balloon, imaging of the site can be performed, and the information used to help create the treatment plan. Such information can include the shape of the treatment cavity, and the location of the cavity relative to anatomical structures, some of which could lie within the range of target tissue, or by their anatomical position, be at risk of inadvertent exposure during delivery of the prescription. If the latter occurs, radiation sensors capable of communication with the central controller can be applied to the skin, or positioned adjacent such structures by needle means or implanted during the surgical procedure. Output from these sensors can be used to eliminate over-exposure to radiation—inadvertent or otherwise. 
         [0012]    The source, preferably mounted on a power cable or catheter, can then be inserted into the source guide, properly positioned, and optionally manipulated within or proximate the balloon to deliver the prescribed dose. Such manipulation can be manual, or is preferably automated in accordance with the treatment plan. The treatment plan may be delivered intraoperatively in its entirety, or may be delivered in fractions over time, in accordance with the treatment plan. At completion of treatment, the apparatus is removed from the body. 
         [0013]    For application of brachytherapy after a bronchial resection or for treatment/palliation of an inoperable lesion (cancer), an applicator with a flexible shaft is advanced through the working channel of the bronchoscope. Once properly situated within a bronchus, the balloon is inflated, positioning the source guide accurately relative to the tissue to be treated. The source can then be positioned and radiotherapy begun. Because of the tubular nature of the resection, radiation delivery may be from within one positioning of a relatively short balloon with the source position fixed or translated within the balloon, or can be delivered from successive balloon positions with iterations of inflation, radiation, and deflation. Alternatively, an elongated or sausage-shaped balloon may be used. Because of the limited diameter of the bronchus, the methods and apparatus of co-pending U.S. application Ser. No. 11/925,200, have applicability here, and this teaching is incorporated herein in its entirety by reference. 
         [0014]    The apparatus and methods of this invention may be employed to facilitate adjuvant brachytherapy used in conjunction with the procedures described above. The features and elements disclosed may be combined in other embodiments as will occur to those of skill in the art, but these variations are to be considered within the scope of the invention. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1A  is a schematic side view in partial section of an applicator of the invention passing through the skin and chest wall of a patient and extending into a lung. 
           [0016]      FIG. 1B  is a detail of the apparatus of  FIG. 1A  showing a suction sleeve with its open end positioned just within the pleural cavity of a patient. 
           [0017]      FIG. 2A  is a schematic side view in partial section of an alternate applicator of the invention comprising a channel of a suction circuit within the applicator shaft bore, the channel having a port opened to communicate with the volume of the pleural cavity. 
           [0018]      FIG. 2B  is a section view of the applicator shaft of  FIG. 2A  showing the suction channel. 
           [0019]      FIG. 3  is a schematic perspective view of a bronchoscope positioned within a section of bronchus, the bronchoscope having a intraluminal balloon applicator positioned and inflated within the resection portion of the bronchus. 
           [0020]      FIGS. 4A  and B are progressive positions of an applicator similar to that of  FIG. 3 , but intended for multiple positioning within the bronchus being treated. 
           [0021]      FIG. 5  is an schematic perspective view of an elongated balloon on a bronchial applicator of the invention, though which a radiation source may be translated in order to treat an elongated section of bronchus. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]      FIG. 1A  is a side view in partial section showing an applicator  10  of the invention passing through the chest wall  12  of the patient. The shaft  14  of the applicator extends from a conventional hub  16  outside the patient into a balloon  18  positioned within a resected portion of the lung  20 . The chest wall  12  includes the skin  22 , ribs  24 , and parietal pleura  26 . The space between the parietal pleura  26  and the visceral pleura (not shown) covering the lung  20  defines the pleural cavity  28 . 
         [0023]    The hub  16  of the applicator  10  includes a side port  30  for inflating the balloon  18  and a central port  32  for advancing a radiation source  34  and source catheter  36  into the balloon  18 . The central port includes a conventional seal (not shown) to avoid fluid leaks around the catheter through the hub. The shaft  14  extends from the hub into the balloon, and the balloon inflation medium passes through the shaft around the catheter  36  to a port  37  opening into the interior of the balloon  18  (see flow arrows). The interior of the shaft serves as a source guide, and accurately positions the source  34  within the balloon. Preferably the balloon is fastened to the shaft at both its distal end  38  and proximal end  40 . 
         [0024]    A suction sleeve  42  is located coaxially and slideably over the applicator shaft  14  as shown in  FIG. 1B , just distal of the hub  16 , and comprises a knob  44 , a conventional seal  45  therein at its proximal end  46 , sealing the interior of the sleeve  42  and outside of the shaft. A suction port  48  is provided near the proximal end, and in communication with the annulus between the sleeve  42  and the shaft  14 . In use, the applicator  10  is advanced into the anatomy until the balloon  18  is properly positioned in the target tissue, i.e. in a resected portion of the lung. The sleeve is then slid on the shaft until the distal end is just within the pleura and in communication with the pleural cavity. If desired, apparatus for locking the sleeve position axially on the shaft may be provided, for example a locking nut or set screw (not shown). Thus upon application of suction, the pleural cavity  28  is drained and/or evacuated, facilitating expansion of the lung  20 . 
         [0025]    As an alternative to the shaft being attached to both the proximal and distal extremities of the balloon as depicted in  FIG. 1A , the shaft need only communicate with the interior of the balloon as shown in  FIG. 2A . The shaft  64  can extend into the volume of the balloon  65  and stop. The inflation medium passes from the port  68  into and through the annulus between the interior of the shaft  64  and the outside of the catheter  36  and into the interior of the balloon. 
         [0026]    In the alternate applicator  60  of  FIG. 2A , there is no suction sleeve as in  FIG. 1A , but rather a suction channel  62  within the bore of the shaft  64 . The channel  62  is shown in section view in  FIG. 2B  taken at the port  72 . Again as in  FIG. 1A , the chest wall  12  includes the skin  22 , ribs  24 , and parietal pleura  26 . The space between the parietal pleura  26  and the visceral pleura covering the lung  20  defines the pleural cavity  28 . The balloon  65  of this embodiment is only secured to the shaft  64  at the balloon proximal end. This fastening is shown as an alternate to the preferred fastening at both distal and proximal extremities of the balloon  65  as shown in  FIG. 1A . The hub  66  of this embodiment comprises one port  68  for balloon inflation as described above in connection with  FIGS. 1A and 1B , and a suction port  70  in communication with the suction channel  62  in the shaft  64  and the port  72 . The distal end of the channel  62  is blocked (for example with a plug  63 ) so as not to communicate with the interior of the balloon. In use, and maintaining the sterile surgical field, the balloon is positioned properly within the resected tissue, and the axial location of the pleural cavity  28  is marked on the shaft over the suction channel  62 . The applicator is then withdrawn from the anatomy sufficiently for the practitioner to pierce or cut a port  72  into the suction channel at the mark. Once the port is made, the applicator is reinserted into the anatomy so the port  72  communicates with the pleural cavity  28 , the balloon  65  is inflated, and the source  34  and the source catheter  36  are inserted to commence radiation treatment. Suction may then be applied to the suction channel  62  via the hub suction port  70 , thus draining the pleural cavity  28  of any fluid therein. 
         [0027]    Alternatively, the suction channel  62  may have a long slot (not shown) communicating outside the shaft  64  in the manner of the port  72 , but extending from the hub  66  distally and stopping short of communication with the interior volume of the balloon  65 . A piece of sterile tape (not shown) may be applied to the exterior of the shaft  64  from the hub  66  to just inside the pleural cavity, thereby forming a closed suction circuit to drain the pleural cavity in a manner similar to that described above. 
         [0028]    With either the applicator of  FIG. 1A  or  2 A, once the balloon is properly located and inflated and the suction circuit established (if needed), radiotherapy is commenced. The planed therapy can be delivered in one dose application, or can be divided into fractions and spread out in time. One treatment is complete, the apparatus is removed, and any closing required is performed in a conventional manner. 
         [0029]      FIG. 3  shows a bronchoscope  80  positioned in a portion of a bronchus  82  which has been resected and subsequently approximated. A balloon applicator  84  is shown protruding from the working channel of the bronchoscope  80 , with the applicator balloon  86  inflated near the point of bronchus reapproximation  88 . With bronchoscopic applications, the applicator shaft is preferably flexible so as easily to follow the working channel of the bronchoscope. A radiation source and flexible source catheter (neither shown) may be advanced into the balloon  86  from outside the patient, properly positioned, and radiotherapy commenced in accordance with a treatment plan. 
         [0030]    If desired in order to deliver radiotherapy to a longer section of bronchus, the balloon  86  may be deflated from its original position, moved within the bronchus, reinflated and further radiation delivered. Such stepping is illustrated in  FIGS. 4A and 4B , and can be provided with use of a manipulator of the sort depicted in  FIG. 3  of copending application Ser. No. 11/925,200 referenced herein. Because of the small scale of the bronchial anatomy, the eccentric source guides and methods of Ser. No. 11/925,200 may be advantageously utilized for treatment from within a balloon positioned in the bronchi. Alternatively to stepping, a sausage-shaped balloon  90  with two-point fastening to the shaft  92  may be used as depicted in  FIG. 5 . The hollow shaft  92  acts as a source guide for a source  34  which is translated within the balloon  90  in accordance with the treatment plan. After completion of treatment, the applicator and bronchoscope are removed. 
         [0031]    With the methods and apparatus of this invention, the advantages of brachytherapy can be made available to virtually all patients undergoing surgery of the lung. Most notably, these advantages include less normal tissue exposure to radiation since no external radiation sources are used, fewer safety requirements to be observed (with x-ray tubes, no bunker facilities are required) and hence virtually any medical facility can perform the radiotherapy, and greatly reduced capital requirements and costs of treatment. 
         [0032]    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.