Abstract:
An interstitial marker for localization of organs, biopsy sites, tumors or tumor beds, is comprised of a fluid marker material which is visible under at least one imaging modality. The fluid marker material is injected at the desired location to create a marker having a desired size and configuration. The configuration includes combinations of straight and curved lines, spheres and blank spaces. The fluid marker material includes a high density metal such as bismuth, gold, or iridium suspended in a liquid, in colloidal form or made into a solution.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to interstitial markers for localization of organs, tumors or tumor beds. More particularly, it relates to an interstitial marker of a high density metal in a solution formed through injection. 
         [0003]    2. Discussion of Related Art 
         [0004]    Interstitial markers have long been known to the medical world. They are regularly used to prepare patients undergoing radiation treatment. Such treatments are typically split into daily doses or fractions. The interstitial markers help the radiation clinician target the therapy to the same area each time treatment is performed on a given patient&#39;s tumor. Interstitial markers are also used in tracking a biopsy site and tracking organ or tumor volume changes, either increases or decreases, over time. 
         [0005]    Historically interstitial markers have been produced of metal “seeds” pre-shaped in the form of a grain of rice or a pre-formed metal coil. Known markers have a standard shapes and sizes. The marker cannot be adjusted based upon the specific needs for the individual. Also, the shape and size of the marker are selected prior to insertion. They cannot be adjusted during positioning. The pre-formed marker is implanted at the desired location through injection. To implant a large diameter marker into a given tissue bed, a large bore needle, such as 18 gauge, must be used. Such a large needle requires anesthesia be use on the patient which complicates the procedure. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention substantially overcomes the deficiencies of known interstitial markers through the use of a liquid marker material. According to various aspects of the invention, bismuth, gold and/or iridium particles are used in the formation of the liquid marker material. According to other aspects of the invention, the metal particles are suspended in a fluid of dextrose, saline or silicon. According to other aspects of the invention, particles of biocompatible plastics or glass micro beads are used in the formation of the liquid marker material. According to another aspect of the invention, the fluid includes Vitamin E oil. 
         [0007]    According to another aspect of the invention, the liquid marker material is injected into the body of the patient at the desired marker location. According to another aspect of the invention, the needle used for injecting the liquid marker is moved during the injection process to create a specific marker shape. According to another aspect of the invention, the needle includes a drive mechanism for precise deposition of the liquid marker material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an illustration of a needle for delivery of the interstitial marker according to an embodiment of the present invention. 
           [0009]      FIG. 2  is an illustration of a needle for delivery of the interstitial marker according to another embodiment of the present invention. 
           [0010]      FIGS. 3A-3G  illustrate representative interstitial markers created according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    An interstitial marker according to an embodiment of the present invention is formed by metal particles suspended in a fluid. Preferably, the metal particles are of bismuth, gold or iridium. These metals are easily visible when viewed via MRI (Magnetic resonance imaging), PET (positron emission tomography), CT (computerized tomography), Digital X-ray radiography, mammography, and ultrasound. Bismuth subnitrate and bismuth subcarbonate are used extensively in medicine and have a long history of safety. Of course, other metals or materials which would be visible using any desired technology could be used. When the interstitial marker is to be viewed with MRI, materials other than metals are preferable. MRI technology does not image gold well. It does, however, provide images of plastics and glass. Therefore, particles of biocompatible plastics, such as high molecular weight polyethylene, or other materials visible using MRI technology can be used for the interstitial marker. Similarly, micro beads of glass could also be used. Furthermore, multiple types of particles can be used with the interstitial marker. The types of particles can be selected for their imaging characteristics using different technologies. With multiple types of particles, the interstitial marker may be easily viewed with different imaging technologies. 
         [0012]    The metal or other particles are approximately 5 microns to 25 microns in diameter. In one embodiment of the invention, the particles have a diameter of 10 microns. Of course, other dimensions could be used. Smaller particles tend to be taken up by the tissue rather than remain in place. Larger particles can cause clots in blood vessels. The particles may have uniform diameters, but need not be uniform. Furthermore, the particles do not need to have uniform shapes. 
         [0013]    In the present invention, the metal particles are suspended in a fluid. Preferably, the fluid is saline, dextrose solution, dimethly-silicone or other silicon based solution. Of course, other fluids may be used. The fluid may provide additional benefits for viewing the interstitial marker with different imaging technologies. For example, the fluid may include vitamin E oil which is easily visible with MRI technology. In one embodiment, a 5% dextrose solution is used for the fluid. According to an embodiment of the invention, concentrations of approximately 1 to 2 grams of gold particles to a milliliter of fluid are used. Similar concentrations of other metals may also be used, as well as different concentrations. 
         [0014]    An interstitial marker is created by injecting the suspension into the patient at the desired location. Since the metal particles are small, a small gauge needle (29 gauge) can be used, regardless of the desired marker size. The size of the marker is determined by the amount of suspension injected at a location. Furthermore, the needle can be moved during the injection process to create different markers of various shapes and sizes. 
         [0015]    An added advantage of a liquid marker system is that the same micro needle can implant a marker in a fine or coarse line form, larger or smaller spheres attached to a line or any combination required by the user. The small gauge needle is easier to “steer” in tissue allowing for larger arches in the marker material creating a marker that has a better ability to create the three dimensional image when viewed to more accurately plan for patent treatment. 
         [0016]    The ability to use a small gauge needle is also beneficial to treatment of the patient. Anesthesia is not required with the small gauge needle. This makes the procedure faster, less costly, and safer for the patient. The patient has less bleeding. Also, the chances of allergic or adverse reactions are reduced. The use of a small gauge needle also allows interstitial markers to be placed at locations not previously possible. For example, the interstitial marker of the present invention can be injected into visceral and vascular areas which could be damaged by larger needles, such as the stomach, pancreas, lung and brain. 
         [0017]      FIG. 1  is a perspective view of a standard needle  10  which can be used to create an interstitial marker according to an embodiment of the present invention. The needle  10  includes a small gauge needle  11  and a syringe  12 . According to embodiments of the invention, 21 or 29 gauge needles are used. Of course, other size needles which can accommodate the metal particles could also be used. The metal suspension  20  is placed in the syringe. The needle  11  is inserted into the patient&#39;s body so that the tip is at the desired location for the marker. Imaging techniques can be used to accurately position the tip of the needle. The plunger  13  is pressed to inject the metal suspension  20  into the patient. The operator can move the tip of the needle to create an interstitial marker of a desired size and shape. 
         [0018]      FIG. 2  illustrates another needle  110  for injecting the metal suspension  20  to create an interstitial marker according to another embodiment of the present invention. As in  FIG. 1 , the needle  110  includes a small gauge needle (not shown) and a syringe  112 . The plunger  113  includes a plurality of teeth  114  positioned on one or more sides. A set of drivers  130  include toothed wheels  131  to engage the teeth  114  of the plunger  113 . A motor (not shown) rotates the wheels  131  to depress the plunger  113 . With an appropriate motor, this embodiment allows accurate control of the amount of metal suspension  20  which is injected. 
         [0019]      FIGS. 3A-3G  illustrate possible marker shapes. A large variety of shapes can be created. This allows optimal markers to be created for specific locations or needs. With the present invention, any shape or size marker can be created during the injection process.  FIG. 3A  illustrates a larger sphere  210  with narrow lines  220  on either side. A sphere  210  is created by injecting more of the metal suspension while moving the needle slowly. A narrow line  220  is created my injecting less of the suspension while moving the needle more quickly. Empty spaces  230  can also be create by moving the needle without injecting any of the metal suspension. 
         [0020]      FIG. 3B  illustrates forming multiple narrow lines  221 ,  222 . The lines may be long  221  or short  222 , or various combinations thereof.  FIG. 3C  illustrates spheres of various sizes  210 ,  211  connected with narrow lines  220 .  FIGS. 3D and 3E  illustrate curved marker shapes. The curved lines may be thick  230  or thin  231  depending upon the rate of injection of the metal suspension relative to the speed of needle movement.  FIG. 3F  illustrates a complex marker shape which can be created in accordance with the present invention. Alternatively, a simple set of spheres may be created, as illustrated in  FIG. 3G . 
         [0021]    Having disclosed at least one embodiment of the present invention, various adaptations, modifications, additions, and improvements will be readily apparent to those of ordinary skill in the art. Such adaptations, modifications, additions and improvements are considered part of the invention which is only limited by the several claims attached hereto.