Abstract:
In a method and a device for x-ray brachytherapy, a probe is inserted into the interior of the body of a subject, the probe carrying at its distal end an x-ray source that radiates x-rays into an exposure area in the body of the subject outside of the probe. The probe also contains an x-ray array that generates an ultrasound image representing at least a portion of the exposure area. A display device displays the ultrasound image to allow identification of the exposure area in the ultrasound image.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention concerns a device for x-ray brachytherapy as well as a method for positioning of a probe inserted into the inside of a body for x-ray brachytherapy. 
         [0003]    2. Description of the Prior Art 
         [0004]    X-ray brachytherapy is a therapeutic treatment with x-rays in which the x-ray source is brought very close to the tissue to be treated (for example a tumor or a vessel wall) after implementation of a endovascular dilatation. In order to able to insert the x-ray source with the aid of a catheter or a probe either without an invasive procedure or with an optimally minimally-invasive procedure inside a body, a miniaturized x-ray source is required as is known from U.S. Pat. No. 6,721,392, for example. This is arranged at the distal end of a probe that, for example, is intraoperatively positioned in a tumor or tumor bed (after its extraction), as explained in detail in the PR information of Carl Zeiss A G, Medical Engineering Innovation by Carl Zeiss A G, “Intraoperative Strahlentherapie mit dem INTRABEAM System von der Carl Zeiss A G” state as of September 2004, for example. 
         [0005]    A miniaturized x-ray source that is arranged in a catheter with which it can be inserted into the body cavities (lumen) in order to irradiate selected tissue zones from the immediate surroundings is known from United States Patent Application Publication—2003/0149327. The x-ray source has a shielding rotatable around the axis of the catheter in order to radiate the x-rays in a targeted manner at least perpendicular to the axis in a selected solid angle. The environment of the catheter can be observed with an optical observation device arranged in a catheter. A light source that exposes only the part of the surface of the hollow space that is also irradiated is used for this purpose. 
         [0006]    In endovascular brachytherapy with a beta or gamma radiator arranged in the tip of a catheter, it is also known from DE 10 2004 008 373 B3 (for example) to arrange an optical observation device in the catheter. For this purpose, a brachytherapy catheter is integrated into a unit with an OCT catheter operating on the basis of optical coherence tomography (OCT). 
         [0007]    For the therapeutic success it is essential that the x-rays radiating out of the catheter from the x-ray source in an exposure area for most part exclusively strike the tissue (for example the tumor) to be treated in order to ensure an optimally low exposure of the healthy tissue located near this. This requires a precise positioning of the exposure area, i.e. a precise positioning and alignment of the x-ray source or, respectively, of the solid angle in which the x-rays exit. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the invention is provide a device for x-ray brachytherapy with a probe that can be inserted inside a body, with which probe a precise positioning of the exposure area is possible. A further object of the invention is to provide a method for positioning of a probe inserted inside a body for x-ray brachytherapy. 
         [0009]    With regard to the device, the above object is achieved by a device that contains a probe that can be inserted into the inside of a body, the probe at its distal end having an x-ray source that radiates x-rays into an exposure area outside of the probe, wherein an ultrasound array for generation of an ultrasound image rendering at least a portion of the exposure area is arranged in the probe. This enables a precise positioning of the exposure area, i.e. a precise positioning of the x-ray source and of the solid angle range in which the x-rays generated by the x-ray source are radiated. 
         [0010]    As used herein the term “probe” is an instrument that can be introduced into the inside of a body. This can be both a catheter (in the narrower sense) that is inserted into body cavities (transluminal) and a needle-like instrument that can be placed within a tissue zone (percutaneous or interstitial). 
         [0011]    If a shielding that can be moved relative to the x-ray source is arranged in the probe to adjust the exposure area, the exposure area can be adjusted more flexibly even given a stationary probe. 
         [0012]    In a preferred embodiment of the invention, the device has a display device to show the ultrasound image and to identify the exposure area in the ultrasound image. This enables a particularly simple and graphic positioning of the exposure area. 
         [0013]    Moreover, if lines of equal dose rating are mixed into the exposure area rendered in the ultrasound image, the dose rating required at different locations of the exposure area can be adjusted in a targeted manner. 
         [0014]    In a further preferred embodiment, the position of the x-ray source is also displayed in the ultrasound image. 
         [0015]    It is advantageous when an optical image of a surroundings of the probe containing at least a portion of the exposure area is generated in addition to the ultrasound image with the aid of an optical observation device arranged in or on the probe. The correct navigation of the probe is then in particular additionally made easier when the exposure area is identified in the optical image. 
         [0016]    A device according to the invention is suitable for insertion into a urethra or a ureter and for therapeutic treatment of a prostate, bladder or kidney tumor. 
         [0017]    The above object also is achieved in accordance with the present invention by a method for positioning a probe inserted into the interior of the body of a subject for x-ray brachytherapy, the probe having an x-ray source at a distal end thereof that radiates x-rays into an exposure area in the body of the patient outside of the probe, the method including generating an ultrasound image that shows at least a portion of the exposure area with an ultrasound array located in the probe, with the ultrasound image being used to correctly position the exposure area within the body of the subject. 
         [0018]    The aforementioned advantages associated with the inventive device are also achieved by the inventive method. 
         [0019]    In an embodiment of the method, an optical image of a subject region containing at least one part of the exposure area is generated in which optical image the exposure area is indicated, in particular in that a luminophore is applied that preferably accumulates in a tumor. The exposure area can then be correctly positioned in a particularly simple and graphic manner in that the exposure area is brought into congruence with the area marked by the luminophore. 
         [0020]    The method according to the invention is suitable in the treatment of a prostate, bladder or kidney tumor in which the probe is inserted into a urethra or a ureter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  schematically illustrates a device for x-ray brachytherapy constructed and operating in accordance with the present invention. 
           [0022]      FIG. 2  illustrates an ultrasound image obtained in accordance with the present invention, in which the exposure area is displayed. 
           [0023]      FIG. 3  illustrates an optical image of the environment of the probe obtained in accordance with the present invention, in which the exposure area is identified. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    According to  FIG. 1 , a probe  6  (a catheter in the example) in which an x-ray source  8  is arranged at its distal end is inserted into a cavity (lumen)  2  of a body  4  (which can be a urethra or a ureter). A shielding  10  is associated with the x-ray source  8 , which shielding  10  in the exemplary embodiment contains a cylindrical part  10   a  that is provided in its circumference with a diaphragm or aperture  12  through which x-rays  14  can exit perpendicular to the longitudinal axis  16  of the probe  6 , i.e. radially in a (for example conical) exposure area  18  defined by the shape of the aperture  12  and its distance from the anode of the x-ray source  8 , which exposure area  18  is emphasized by hatching in the Figure and is indicated by boundary lines  19 . 
         [0025]    The cylindrical part  10   a  of the shielding  10  is arranged within the probe  6  such that it can be rotated around its longitudinal axis  16  so that the exposure area  18  can likewise be pivoted on this longitudinal axis  16 . For this purpose, the outer wall of the probe  6  is provided with a window  20  rotating annularly, which window  20  is permeable to x-rays  14 . However, the probe  6  can also be permeable to x-rays  14  in a larger region and, for example, possess an outer wall consisting of a polymer material. 
         [0026]    The shielding  10  has on its front side a front plate  10   b  that is provided with a closable diaphragm (not shown in detail in  FIG. 1 ) with which it is possible to selectively radiate x-rays  14  in the direction of the longitudinal axis  16 . In this case either a movable lock is provided with which the aperture  12  can be closed or an additional shielding is provided that is arranged in the probe  6  such that the aperture  12  can be positioned in the region of this shielding. For example, this can be realized in that the window  20  does not extend over its entire extent. 
         [0027]    An ultrasound array  30  that generates an ultrasound image of a subject region  34  (illustrated by boundary lines  32 ) that overlays at least a portion of the exposure area  18  is arranged in the immediate proximity of the x-ray source  8 . 
         [0028]    Moreover, the probe  6  contains a schematically indicated optical observation device  40  with which a subject region can be observed that renders at least a portion of the exposure area  18 . 
         [0029]    The probe  6  is connected to a control and evaluation device  42  with which the x-ray source  8 , the ultrasound array  30  and the observation device  40  are controlled and the signals transmitted from the ultrasound array  30  and from the observation device  40  are evaluated so that they can be shown as an ultrasound image or as an optical image on a display device  44  (for example a monitor). 
         [0030]    In the example of  FIG. 1  a tissue zone  52  to be therapeutically treated (for example a tumor, in particular a prostate tumor, a bladder tumor or a kidney tumor that should be irradiated with x-rays  14 ) is located in the region of the wall  50  of the cavity  2 . 
         [0031]    This tissue zone  52  as well as the wall  50  are schematically depicted in the ultrasound image of  FIG. 2 . In this ultrasound image the intersection surface of the exposure area  18  with the subject plane detected by the ultrasound array is, for example, identified by rendering its lateral boundary lines  19 . The exposure area  18  mixed into the ultrasound image in this manner enables a correct positioning of the probe or, respectively, of the x-ray source. 
         [0032]    Moreover, approximately circular lines  54  of equal dose rating that indicate the current local dose rating to the therapist are mixed into the ultrasound image, for instance. These lines  54  are located, for example, located among one another at an interval that corresponds to the decrease of the dose rating to 1/e, respectively. These are approximately 1.2 cm given an x-ray radiator with an average energy of 20 keV in the tissue. The therapist can then adjust the required dose rating by changing the operating parameters of the x-ray source (anode current, acceleration voltage). These lines  54  of the same dose rating then shift in the ultrasound image corresponding to the dose rating changing with the variation of the operating parameters. 
         [0033]    According to  FIG. 3 , an optical image in which the wall  50  of the cavity is visible given corresponding illumination is generated from the surroundings of the probe. If a luminophore is additionally applied (for example directly with the aid of the probe) which preferably accumulates in the tissue zone  52  if this is a tumor and that, for example, is excited by the light source used for illumination and emits fluorescence light in the visible range, the tumor  52  can also be made visible in the optical image at least in its surface region with which it borders the cavity. If the envelope if the x-ray beam striking the surface of the wall  50  is additionally mixed in as a circular line  56  and its center axis is mixed in as a point  58 , the exact positioning can also be effected with the aid of the optical image in addition to the positioning with the ultrasound image since in this case image information exists from a different plane, for example a plane perpendicular to the image plane of the ultrasound image. 
         [0034]    The invention is described using a catheter inserted into the cavity of a body. In principle the invention is also suitable for probes that are directly inserted into the tissue, as this is the case in the invasive post-treatment (explained above) of a tumor bed of a previously removed tumor. The tissue zone to be treated can also be a vessel wall that should be irradiated after the implementation of a dilatation to reduce the restenosis rate. 
         [0035]    Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.