Abstract:
An intracorporeal site marker that is adapted to be implanted into a biopsy cavity includes a plurality of balls or particles. The balls or particles are either sintered together or bonded together. Other alternative embodiments of site markers visible under various imaging modes are also disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to site markers for breast biopsy procedures. More specifically, the present invention relates to site markers that are visible under multiple modalities.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the diagnosis and treatment of breast cancer, it is often necessary to perform a biopsy to remove tissue samples from a suspicious mass. The suspicious mass is typically discovered during a preliminary examination involving visual examination, palpation, X-ray, magnetic resonance imaging (MRI), ultrasound imaging or other detection means.  
         [0003]     When a suspicious mass is detected, a sample is taken by biopsy, and then tested to determine whether the mass is malignant or benign. This biopsy procedure can be performed by an open surgical technique, or through the use of a specialized biopsy instrument. To minimize surgical intrusion, a small specialized instrument such as a biopsy needle is inserted in the breast while the position of the needle is monitored using fluoroscopy, ultrasonic imaging, X-rays, MRI or other suitable imaging techniques.  
         [0004]     In a relatively new procedure, referred to as stereotactic needle biopsy, the patient lies on a special biopsy table with her breast compressed between the plates of a mammography apparatus and two separate X-rays are taken from two different points of reference. A computer then calculates the exact position of the mass or lesion within the breast. The coordinates of the lesion are then programmed into a mechanical stereotactic apparatus which advances the biopsy needle into the lesion with precision. At least five biopsy samples are usually taken from locations around the lesion and one from the center of the lesion.  
         [0005]     Regardless of the method or instrument used to perform the biopsy, subsequent examination of the surgical site may be necessary, either in a follow up examination or for treatment of a cancerous lesion. Treatment often includes a mastectomy, lumpectomy, radiation therapy, or chemotherapy procedure that requires the surgeon or radiologist to direct surgical or radiation treatment to the precise location of the lesion. Because this treatment might extend over days or weeks after the biopsy procedure, and the original features of the tissue may have been removed or altered by the biopsy, it is desirable to insert a site marker into the surgical cavity to serve as a landmark for future identification of the location of the lesion.  
         [0006]     Known biopsy site markers have been found to have disadvantages in that the site markers are not visible under all available modalities. Moreover, because of this problem, when cancer is found at a biopsy site that has been previously marked with a site marker, due to the poor visibility of the biopsy site marker under ultrasound or other visualization modalities, the patient must undergo an additional procedure that places an additional device the biopsy site to enable the surgeon to find the biopsy site in subsequent procedures. One known technique has been to place a breast leasion localization wire at the biopsy site. The localization wire is typically placed at the biopsy site via mammography and/or ultrasound.  
         [0007]     Accordingly, there is a need for site markers made from biocompatible materials that are visible under various modes of imaging to reduce the number of procedures that patients must undergo in detection and treatment of cancer.  
       SUMMARY OF THE INVENTION  
       [0008]     Intracorporeal site markers are provided for implantation into a surgical biopsy cavity. In accordance with one aspect of the invention, the site markers include a plurality of balls or particles, bonded together to form a unitary body. The balls or particles are made from biocompatible materials such as titanium, stainless steel or platinum and are visible under multiple modes of imaging. The balls or particles are generally bonded together by sintering or by an adhesive material such as epoxy. Because the inventive site marker is constructed of material that is visible under multiple modalities, there is no need for the patient to be subjected to an additional procedure or have an additional device implanted at the biopsy site to enable the surgeon to locate the biopsy site at a later time.  
         [0009]     Alternative embodiments include a site marker having at least one continuous strand of wire that is formed in a molding cavity. The wire is made from any biocompatible material such as titanium, stainless steel, platinum, or other suitable material, and is compressed to form a mass that resembles a ball of yarn. Additionally, the site marker can take the form of a resonating capsule, or a rod with drilled holes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     These and other features and advantages of the invention will be apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings, in which:  
         [0011]      FIG. 1  is a perspective view of a biopsy site in a human breast showing the breast in section and one or more site markers being implanted in the biopsy cavity using a site marker delivery system;  
         [0012]      FIG. 2A  is a side elevational view of a site marker according to a first embodiment of the present invention;  
         [0013]      FIG. 2B  is an end elevational view of the site marker of  FIG. 2A ;  
         [0014]      FIG. 3A  is a side elevational view of a site marker according to a second embodiment of the present invention;  
         [0015]      FIG. 3B  is an end elevational view of the site marker of  FIG. 3A ;  
         [0016]      FIG. 4A  is a side elevational view of a site marker according to a third embodiment of the present invention;  
         [0017]      FIG. 4B  is an end elevational view of the site marker of  FIG. 4A ;  
         [0018]      FIG. 5  is a front elevational view of a site marker according to a fourth embodiment of the present invention;  
         [0019]      FIG. 6  is a side elevational view of a site marker according to a fifth embodiment of the present invention;  
         [0020]      FIG. 6A  is a side elevational view of a site marker according to a sixth embodiment of the present invention;  
         [0021]      FIG. 7  is a perspective view of a site marker according to a seventh embodiment of the present invention;  
         [0022]      FIG. 7A  is a perspective view of a site marker according to an eighth embodiment of the present invention;  
         [0023]      FIG. 8A  is a side elevational view of a site marker according to a ninth embodiment of the present invention;  
         [0024]      FIG. 8B  is an end elevational view of the site marker of  FIG. 8A .  
         [0025]      FIG. 9  is a side elevational view of a site marker in accordance with a tenth embodiment of the present invention 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]      FIG. 1  illustrates a perspective view of a human breast  10  being implanted with a site marker  12  according an embodiment of the present invention. At a biopsy site  14  is a lesion  16  from which a tissue sample has been removed, resulting in a biopsy cavity  18 . One or more site markers  12  are implanted in the biopsy cavity  18  using a marker delivery system  20 , as shown in  FIG. 1 . In one embodiment, the marker delivery system  20  is slidably advanced through an inner lumen  22  of a biopsy device (not shown), which avoids the need to withdraw the biopsy device and thereafter insert the marker delivery system  20 . Delivering the site marker  12  in the biopsy cavity  18  without withdrawing the biopsy device reduces the amount of tissue damage and enables more accurate placement of the site marker  12 . The marker delivery system  20  illustrated in  FIG. 1  is exemplary only and it is understood that the site marker embodiments disclosed herein are suitable for use with other marker delivery systems.  
         [0027]      FIGS. 2A-8B  illustrate suitable exemplary site marker embodiments according to the present invention. In general, the site markers described herein are made from biocompatible materials such as, but not limited to, titanium, stainless steel, and platinum. These materials have appropriate densities for radiographic imaging, appropriate surface characteristics for ultrasonic imaging, and appropriate magnetic characteristics for magnetic resonance imaging. The site markers that will be described below are preferably made from titanium; however, it is understood that any suitable biocompatible material may be used.  
         [0028]     Referring initially to  FIGS. 2A and 2B , a site marker  24  includes a plurality of balls  26  sintered together to form a unitary body. The balls  26 , as shown, vary in size and are sintered together randomly such that there is no structured or predetermined equidistance between the centers of the balls  26 . In other embodiments, the size of the balls  26  may be generally uniform, or the balls  26  may be sintered together such that the centers of the balls  26  are aligned in a predetermined manner. As illustrated in  FIGS. 2A and 2B , one embodiment of site marker  24  measures approximately 1.5 mm in diameter ( FIG. 2B ) and 3 mm in length ( FIG. 2A ). As those skilled in the art will appreciate, when the size and sintering pattern of the balls  26  are modified, the size, shape and dimensions of the site marker will also vary. The balls  26  may be constructed from any biocompatible material with suitable echogenic properties such as, but not limited to, titanium, stainless steel, or platinum.  
         [0029]      FIGS. 3A and 3B  illustrate another embodiment of the invention having irregularly shaped particles or bits  28  that are sintered together to form site marker  30 . The particles, as shown in  FIGS. 3A and 3B , are exaggerated to illustrate the random shapes of the particles  28 . In application, however, the edges of the particles are sufficiently smooth so as to not damage any tissue. The particles can be substantially similar in size and shape, or they may vary as shown in  FIGS. 3A and 3B . The particles  28  may be constructed from any biocompatible material with suitable echogenic properties such as, but not limited to, titanium, stainless steel, or platinum.  
         [0030]     In another aspect of the invention, the particles  28  may be sufficiently small such that, when sintered together, the resultant site marker  32  appears to form a porous metal, as shown in  FIGS. 4A and 4B .  
         [0031]      FIG. 5  shows another embodiment of a biopsy site marker  34  made from a continuous strand of wire  36 . To form the biopsy site marker  34 , the wire  36  is fed into a molding cavity (not shown). When the wire  36  reaches the back wall of the cavity, it folds over onto itself conforming to the shape of the molding cavity. The wire  36  is compressed into a mass that resembles a ball of yarn. Inherently, the size and shape of the site marker  34  is dependent upon the size and shape of the molding cavity. The wire  36  may be constructed from any biocompatible material with suitable echogenic properties such as, but not limited to, titanium, stainless steel, or platinum.  
         [0032]      FIG. 6  shows a thin-walled hollow site marker in the form of a capsule  38  having an open end  40 . A cap  42  is attached to the open end  40  by a weld  44 . The capsule  38  is designed to resonate at a predetermined ultrasound frequency. In the event that the capsule  38  needs to resonate at more than one frequency, a resonant beam  46 , as shown in  FIG. 6A , can be attached to the inner surface wall of the cap  42  so that the beam resonance is transmitted through the wall of the capsule. The capsule  38  may be constructed from any biocompatible material with suitable echogenic properties such as, but not limited to, titanium, stainless steel, or platinum.  
         [0033]      FIGS. 7 and 7 A show site marker  48 ,  50  in the form of a rod  56 ,  58  having drilled holes  52 ,  54  throughout the body of the rod. Site marker  48  of  FIG. 7  is a solid rod, whereas site marker  50  of  FIG. 7A  is a hollow rod or tube. The holes in both rods  48 ,  50  may be drilled in a random or in a predetermined pattern. The rod  56 ,  58  may be constructed from any biocompatible material with suitable echogenic properties such as, but not limited to, titanium, stainless steel, or platinum.  
         [0034]      FIGS. 8A and 8B  illustrate another embodiment of a site marker  60  that includes ball or bits  62  of material that are visible under one or more imaging modalities, and dispersed in a block of material  64  that is different than the balls or bits  62 . The balls or bits  62  may be constructed of titanium, stainless steel or other suitable material that are visible under more than one imaging modalities. In addition, the balls or bits  62  of material may be contacting each other within the block  64  and may vary in size and shape. In one embodiment, the block of material  64  is a biocompatible material such as epoxy. In another embodiment, the block of material is constructed of a bioabsorbable material that is absorbed by the patient&#39;s body such that only the bills  62  remain at the biopsy site.  
         [0035]      FIG. 9  illustrates another embodiment of a site marker  70  that is made in accordance with the present invention. Site marker  70  is a unitary body made of biocompatible material or a combination of biocompatible materials that are visible under one or more imaging modalities. Maker  70  may be hollow or solid. According to one aspect of the invention, marker  70  further includes a plurality of depressions  72  formed on an outer surface  74  of marker  70 . Depressions  72  may be formed on surface  74  so as to be set a predetermined distances apart from one another or may be randomly formed on outer surface  74 . Depressions  72  may also be formed so as to have a variety of shapes. In one embodiment, depressions  72  have a parabola shape, with a length of at least about 0.25 mm.  
         [0036]     While the present invention has been particularly shown and described with reference to the foregoing preferred embodiments, it should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention embodiments within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. The foregoing embodiment is illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.