Abstract:
In order to later identify the location of a biopsy or surgery, various means and methods for permanently and non-surgically marking selected tissue in the human body are used. Later visualization of the markers is readily accomplished using state-of-the-art imaging systems.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to methods and devices for marking and defining particular locations in human tissue, and more particularly relates to methods and devices for permanently defining the location and margins of lesions detected in a human breast. 
         [0002]    It is desirable and often necessary to perform procedures for detecting, sampling, and testing lesions and other abnormalities in the tissue of humans and other animals, particularly in the diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions and other diseases or disorders. Typically, in the case of cancer, when a physician establishes by means of known procedures (i.e. palpation, x-ray, MRI, or ultrasound imaging) that suspicious circumstances exist, a biopsy is performed to determine whether the cells are cancerous. Biopsy may be an open or percutaneous technique. Open biopsy removes the entire mass (excisional biopsy) or a part of the mass (incisional biopsy). Percutaneous biopsy on the other hand is usually done with a needle-like instrument and may be either a fine needle aspiration (FNA) or a core biopsy. In FNA biopsy, very small needles are used to obtain individual cells or clusters of cells for cytologic examination. The cells may be prepared such as in a Papanicolaou (Pap) smear. In core biopsy, as the term suggests, a core or fragment of tissue is obtained for histologic examination which may be done via a frozen section or paraffin section. The chief difference between FNA and core biopsy is the size of the tissue sample taken. A real time or near real time imaging system having stereoscopic capabilities, such as the stereotactic guidance system described in U.S. Pat. No. 5,240,011, is employed to guide the extraction instrument to the lesion. Advantageous methods and devices for performing core biopsies are described in the assignee&#39;s co-pending patent application Ser. No. 08/217,246, filed on Mar. 24, 1994, and herein incorporated by reference. 
         [0003]    Depending upon the procedure being performed, it is sometimes desirable to completely remove suspicious lesions for evaluation, while in other instances it may be desirable to remove only a sample from the lesion. In the former case, a major problem is the ability to define the margins of the lesions at all times during the extraction process. Visibility of the lesion by the imaging system may be hampered because of the distortion created by the extraction process itself as well as associated bleeding in the surrounding tissues. Although the lesion is removed and all fluids are continuously aspirated from the extraction site, it is likely that the process will “cloud” the lesion, thus impairing exact recognition of its margins. This makes it difficult to ensure that the entire lesion will be removed. 
         [0004]    Often, the lesion is merely a calcification derived from dead abnormal tissue, which may be cancerous or pre-cancerous, and it is desirable to remove only a sample of the lesion, rather than the entire lesion, to evaluate it. This is because such a lesion actually serves to mark or define the location of adjacent abnormal tissue, so the physician does not wish to remove the entire lesion and thereby lose a critical means for later re-locating the affected tissue. One of the benefits to the patient from core biopsy is that the mass of the tissue taken is small. However, oftentimes, either inadvertently or because the lesion is too small, the entire lesion is removed for evaluation, even though it is desired to remove only a portion. Then, if subsequent analysis indicates the tissue to be malignant (malignant tissue requires removal, days or weeks later, of tissue around the immediate site of the original biopsy), it is difficult for the physician to determine the precise location of the lesion, in order to perform necessary additional procedures on adjacent potentially cancerous tissue. Additionally, even if the lesion is found to be benign, there will be no evidence of its location during future examinations, to mark the location of the previously removed calcification so that the affected tissue may be carefully monitored for future reoccurrences. 
         [0005]    Thus, it would be of considerable benefit to be able to permanently mark the location or margins of such a lesion prior to or immediately after removing or sampling same. Marking prior to removal would help to ensure that the entire lesion is excised, if desired. Alternatively, if the lesion were inadvertently removed in its entirety, marking the biopsy site immediately after the procedure would enable reestablishment of its location for future identification. 
         [0006]    A number of procedures and devices for marking and locating particular tissue locations are known in the prior art. For example, location wire guides, such as that described in U.S. Pat. No. 5,221,269 to Miller et al, are well known for locating lesions, particularly in the breast. The device described by Miller comprises a tubular introducer needle and an attached wire guide, which has at its distal end a helical coil configuration for locking into position about the targeted lesion. The needle is introduced into the breast and guided to the lesion site by an imaging system of a known type, for example, x-ray, ultrasound, or magnetic resonance imaging (MRI), at which time the helical coil at the distal end is deployed about the lesion. Then, the needle may be removed from the wire guide, which remains in a locked position distally about the lesion for guiding a surgeon down the wire to the lesion site during subsequent surgery. While such a location system is effective, it is obviously intended and designed to be only temporary, and is removed once the surgery or other procedure has been completed. 
         [0007]    Other devices are known for marking external regions of a patient&#39;s skin. For example, U.S. Pat. No. 5,192,270 to Carswell, Jr. discloses a syringe which dispenses a colorant to give a visual indication on the surface of the skin of the point at which an injection has or will be given. Similarly, U.S. Pat. No. 5,147,307 to Gluck discloses a device which has patterning elements for impressing a temporary mark in a patient&#39;s skin, for guiding the location of an injection or the like. It is also known to tape or otherwise adhere a small metallic marker, e.g. a 3 millimeter diameter lead sphere, on the skin of a human breast in order to delineate the location of skin calcifications (see Horner et al, The Geographic Cluster of Microcalcifications of the Beast, Surgery, Gynecology, &amp; Obstetrics, December 1985). Obviously, however, none of these approaches are useful for marking and delineating internal tissue abnormalities, such as lesions or tumors. 
         [0008]    Still another approach for marking potential lesions and tumors of the breast is described in U.S. Pat. No. 4,080,959. In the described procedure, the skin of the portion of the body to be evaluated, such as the breasts, is coated with a heat sensitive color-responsive chemical, after which that portion of the body is heated with penetrating radiation such as diathermy. Then, the coated body portion is scanned for color changes which would indicate hot spots beneath the skin surface. These so-called hot spots may represent a tumor or lesion, which does not dissipate heat as rapidly because of its relatively poor blood circulation (about 1/20 of the blood flow through normal body tissue). This method, of course, functions as a temporary diagnostic tool, rather than a permanent means for delineating the location of a tumor or lesion. 
         [0009]    A method of identifying and treating abnormal neoplastic tissue or pathogens within the body is described in U.S. Pat. No. 4,649,151 to Dougherty et al. In this method, a tumor-selective photosensitizing drug is introduced into a patient&#39;s body, where it is cleared from normal tissue faster than it is cleared from abnormal tissue. After the drug has cleared normal tissue but before it has cleared abnormal neoplastic tissue, the abnormal neoplastic tissue may be located by the luminescence of the drug within the abnormal tissue. The fluorescence may be observed with low intensity light, some of which is within the drugs absorbance spectrum or higher intensity light, a portion of which is not in the drugs absorbance spectrum. Once detected, the tissue may be destroyed by further application of higher intensity light having a frequency within the absorbance spectrum of the drug. Of course, this method also is only a temporary means for marking the abnormal tissue, since eventually the drug will clear from even the abnormal tissue. Additionally, once the abnormal tissue has been destroyed during treatment, the marker is destroyed as well. 
         [0010]    It is also known to employ biocompatible dyes or stains to mark breast lesions. First, a syringe containing the colorant is guided to a detected lesion, using an imaging system. Later, during the extraction procedure, the surgeon harvests a tissue sample from the stained tissue. However, while such staining techniques can be effective, it is difficult to precisely localize the stain. Also, the stains are difficult to detect fluoroscopically and may not always be permanent. 
         [0011]    Additionally, it is known to implant markers directly into a patients body using invasive surgical techniques. For example, during a coronary artery bypass graft (CABG), which of course constitutes open heart surgery, it is common practice to surgically apply one or more metallic rings to the aorta at the site of the graft. This enables a practitioner to later return to the site of the graft by identifying the rings, for evaluative purposes. It is also common practice to mark a surgical site with staples, vascular clips, and the like, for the purpose of future evaluation of the site. 
         [0012]    A technique has been described for the study of pharyngeal swallowing in dogs, which involves permanently implanting steel marker beads in the submucosa of the pharynx (S. S. Kramer et al, A Permanent Radiopaque Marker Technique for the Study of Pharyngeal Swallowing in Dogs, Dysphagia, Vol. 1, pp. 163-167, 1987). The article posits that the radiographic study of these marker beads during swallowing, on many occasions over a substantial period of time, provides a better understanding of the pharyngeal phase of degluitition in humans. In the described technique, the beads were deposited using a metal needle cannula having an internal diameter slightly smaller than the beads to be implanted. When suction was applied to the cannula, the bead sat firmly on the tip. Once the ball-tipped cannula was inserted through tissue, the suction was broken, thereby releasing the bead, and the cannula withdrawn. 
         [0013]    Of course, this technique was not adapted or intended to mark specific tissue sites, but rather to mark an entire region or structure of the body in order to evaluate anatomical movements (i.e. swallowing motions). It also was not intended for use in humans. 
         [0014]    Accordingly, what is needed is a method and device for non-surgically implanting potentially permanent markers at the situs of a lesion or other abnormal tissue, for the purpose of defining the margins of a lesion before it is removed and/or to establish its location after it has been removed. The markers should be easy to deploy and easily detected using state of the art imaging techniques. 
       SUMMARY OF THE INVENTION 
       [0015]    This invention solves the problems noted above by providing an implantable device which is particularly adapted to mark the location of a biopsy or surgery for the purpose of identification. The device is remotely delivered, preferably percutaneously. Visualization of the marker is readily accomplished using various state of the art imaging systems. Using the invention, it is possible to permanently mark the location or margins of a lesion or other tissue site, prior to removing or sampling same. The markers function to provide evidence of the location of the lesion after the procedure is completed, for reference during future examinations or procedures. 
         [0016]    More particularly, a device is provided for marking tissue within a human body to identify a selected location for a diagnostic or therapeutic procedure. The device comprises a marker element and an apparatus for remotely delivering the marker element from outside the human body to the selected tissue location. Since, with remote delivery (e.g. percutaneously) direct visual access is not possible, an aided visualization device is used, such as an imaging system, an endoscope, or the like. Deployment of the marker element is such that it becomes implanted in the tissue. 
         [0017]    The delivery apparatus preferably includes a member, which may comprise a tube, such as a needle, cannula, or trocar, of any known type for delivering medications, surgical equipment, or other items to the interior of a patient&#39;s body. The member may also be the body of an optical instrument such as an endoscope, laparoscope, or arthroscope. In the preferred embodiment, a biopsy needle or gun, such as is often used to extract tissue for examination in a biopsy procedure, is used in conjunction with the marking device, comprising a portion of the delivery apparatus, in order to provide a means for entering the patient&#39;s body and positioning the marker element at the selected tissue location. However, in other embodiments, the marking device is self contained, having a means itself for obtaining entry to the body, and being guided by a commercially available guidance system, such as a stereotactic guidance system. 
         [0018]    The aforementioned member or tube, which typically comprises a cannula or needle having a lumen, has a distal end portion or region and a proximal end portion or region, and is adapted to extend through the body. The distal region is adapted to retain and deploy the marker element and the proximal region is linked to the distal region, so that predetermined marker deployment functions may be communicated from the proximal region to the distal region. In some embodiments, these deployment functions are communicated by means of the marker elements themselves travelling through the lumen for deployment from the distal region. In other embodiments, an actuator extends axially through the lumen to communicate deployment functions to the marker element held on or by the distal region. The apparatus is preferably guided to the selected tissue location, i.e. the site of the detected lesion or other abnormality, using a stereotactic guidance system or similar imaging system. 
         [0019]    Several alternative embodiments of the marking device are disclosed. In one embodiment, the distal region of the tube includes a forming die, which is adapted to form each marker element into a predetermined shape, preferably a helix, as the marker element is deployed from the lumen. In a number of alternative embodiments, a mechanism, such as a mandrel, is used to push the marker elements through the tube. The marker elements may comprise a pre-formed spring having a predetermined shape, which is compressed into a linear position within the tube lumen. Upon deployment from the lumen, the spring is adapted to expand and assume its predetermined shape to such an extent that the energy of its expansion is sufficient to implant the marker element into the tissue at the selected tissue location. In some embodiments, implantation is accomplished because the marker elements have a plurality of attachment elements, each having a tip end (sometimes sharpened) which expands outwardly with sufficient energy to embed and anchor itself into the tissue at the selected tissue location. In other embodiments, the marker element has blunt, rather than sharpened edges, but is adapted to expand sufficiently upon exiting from the tube that its edges press radially against the selected tissue, thereby wedging and implanting the marker element. 
         [0020]    In yet another embodiment of the invention, the tube lumen is adapted to receive a deployment actuator connector, or center wire, which extends axially through the lumen. The connector includes a distal portion which extends distally of the tube and a proximal portion which extends proximally of the tube. The proximal portion is attached to a deployment actuator, such as a pull ring, while the distal portion is attached to the marker element. On the connector, proximal to the distal portion, is a predetermined failure point which is adapted to be the weak point on the connector by failing first under tension. In operation, once the tube distal region has been positioned at the selected tissue location, the deployment actuator is actuated in a proximal direction to pull the marker element against the distal region of the tube. The tube distal region thus functions as a forming die to cause the marker element to bend until it abuts the tube distal region at its junction with the distal portion of the connector, such that the marker element is reconfigured to a desired shape. The proximal portion of the connector is adapted to be severed from the distal portion at the predetermined failure point upon the application of continued tension on the deployment actuator after abutment of the marker element against the tube distal region, thereby releasing and implanting the marker element. 
         [0021]    Another important feature of the invention is the ability to utilize marker elements having a plurality of shapes. In some embodiments, these shapes may be created merely by utilizing different sized material stock or different cross sections. This shape diversity permits the adoption of a system wherein each shape denotes a different selected tissue location or event. 
         [0022]    In a preferred embodiment of the invention, the device is adapted to be employed in combination with a medical instrument which transports the device to the selected tissue location responsive to positional control by a guidance system. The medical instrument preferably draws a vacuum to isolate and retain tissue at the selected location in a tissue receiving port. The marking device is adapted to deploy the marker element into the retained tissue. 
         [0023]    In another aspect of the invention, a marker element is provided for marking tissue within a human body to identify a selected location for a diagnostic or therapeutic procedure. The marker element, which is preferably comprised of a biocompatible, implantable, and substantially radiopaque material, is adapted to be deployed to the selected tissue location percutaneously by a delivery instrument, so as to become implanted in the tissue. 
         [0024]    A number of different marker element configurations and materials may be employed. Materials may include stainless steel, titanium, and the like, as well as non-metallic materials, such as polymers, salts, and ceramics, for example. In some embodiments, the marker element may actually be formed into a desired shape by a forming die in the delivery instrument, while in other embodiments, it may comprise a spring which radially expands upon exit from the delivery instrument to embed itself in the tissue. 
         [0025]    In yet another aspect of the invention, a method for permanently marking tissue in a human body to identify a selected location for a diagnostic or therapeutic procedure is disclosed, which comprises actuating a delivery instrument, having a tube with a distal region, to a position wherein the tube extends through the human body and the distal region is at the selected location. A marker element is then deployed from the tube distal region to the selected tissue location so that it becomes anchored in the tissue. 
         [0026]    These and other aspects and advantages of the present invention are set forth in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0027]      FIG. 1  is a cross-sectional view of a biopsy instrument embodiment as described in co-pending patent application Ser. No. 08/217,246, configured to be utilized as a preferred instrument for use in conjunction with the inventive tissue marking device; 
           [0028]      FIGS. 2 and 3  are cross-sectional views illustrating the sequential steps in the operation of the biopsy instrument embodiment needed to capture tissue targeted for marking; 
           [0029]      FIG. 4  is a cross-sectional view of one embodiment of a tissue marking device constructed in accordance with the principles of the invention, illustrating the device in a first position in preparation for delivering a marker to tissue targeted for marking; 
           [0030]      FIGS. 5 ,  6 ,  7 , and  8  are cross-sectional views similar to  FIG. 4 , illustrating sequentially the delivery of a marker to the targeted tissue; 
           [0031]      FIGS. 9 ,  10 , and  11  are schematic cross-sectional views of an alternative embodiment of a tissue marking device constructed in accordance with the principles of the invention, illustrating sequentially the delivery of a marker to the targeted tissue; 
           [0032]      FIG. 12  is a schematic cross-sectional view illustrating a third alternative embodiment of a tissue marking device constructed in accordance with the principles of the invention; 
           [0033]      FIG. 13  is a schematic cross-sectional view illustrating a fourth alternative embodiment of a tissue marking device constructed in accordance with the principles of the invention; 
           [0034]      FIG. 14  is a schematic cross-sectional view illustrating a fifth alternative embodiment of a tissue marking device constructed in accordance with the principles of the invention; 
           [0035]      FIG. 15  is a schematic cross-section view illustrating a sixth alternative embodiment of a tissue marking device constructed in accordance with the principles of the invention; 
           [0036]      FIG. 16  is a schematic cross-sectional view illustrating a seventh alternative embodiment of a tissue marking device constructed in accordance with the principles of the invention; 
           [0037]      FIG. 17  is a front elevation view of an alternative marker element embodiment; 
           [0038]      FIG. 18  is a perspective view of another alternative marker element embodiment; 
           [0039]      FIG. 19  is a front elevation view of yet another alternative marker element embodiment; and 
           [0040]      FIG. 20  is a front elevation view of still another alternative marker element embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    Now with more particular reference to the drawings,  FIGS. 4-8  illustrate sequentially the deposit of a marker into a desired tissue location, utilizing a preferred embodiment of the invention. Specifically, the marking instrument  10  comprises a marker element  12  which includes an umbrella end comprising a pair of attachment members or wings  14  and  16 , and a center wire  18 . All three wires  14 ,  16  and  18  are joined at the distal end  20  of the center wire  18 , preferably by welding. At the proximal end  22  of the center wire is a deployment actuator or pull ring  24 , which is preferably attached by welding or brazing. 
         [0042]    To place the marker element  12  at a desired location, a biopsy needle or gun is preferably used, though other known delivery means could be used as well. For example, the stand-mounted biopsy instrument described in U.S. patent application Ser. No. 08/217,246, previously incorporated by reference into this application, is a preferred instrument for introducing the marker element into the body of a patient. One embodiment of such an instrument  26  is partially illustrated in  FIGS. 1-3 . The biopsy instrument  26  includes a housing  28 . A hollow outer piercing needle  38  is attached to the housing  28  at location  34 . A distal end of the hollow outer piercing needle  38  includes a point  40 . Hollow outer piercing needle  38  also includes a tissue receiving port or bowl  42  ( FIGS. 2 and 3 ). A cannular inner cutter  44  is movably positioned coaxially within the hollow outer piercing needle  38  and housing  28 . A vacuum line  46  supplies vacuum to ports  50  in the bottom of the receiving bowl  42 . 
         [0043]    Operation of the biopsy instrument to facilitate the placement of a tissue marker is illustrated sequentially in  FIGS. 1-3 .  FIG. 1  illustrates the distal end point  40  of the hollow outer piercing needle  38  in position to pierce a target tissue  51 . The initial position of the point  40  with respect to the tissue area being marked is determined by the overall position of the biopsy instrument with respect to the patient. For example, the entire biopsy instrument may be mounted on a commercially available stereotactic guidance system (not shown) commonly used in the medical field for accurate positioning of a variety of medical devices with respect to a patient. A detailed description of such a motorized biopsy needle positioner, i.e. stereotactic guidance system, is given in U.S. Pat. No. 5,240,011, issued on Aug. 31, 1993 to Michael Assa, which is hereby incorporated herein by reference. The suspect lesion within tissue  51  is to be targeted and marked according to the instructions provided with the stereotactic guidance system. As shown in  FIG. 1 , the stereotactic guidance system has positioned the biopsy instrument  26  such that the distal end point  40  is immediately adjacent to the surface of the tissue  51 . Once the point  40  is adjacent the specific lesion to be marked, the needle  38  is fired into the lesion such that the point  40  traverses through the lesion, thereby placing the tissue receiving bowl  42  in the center of the lesion. 
         [0044]    As shown in  FIG. 2 , after the hollow outer piercing needle  38  has been positioned at the precise location within the tissue  51  at which it is desired to mark tissue, the cutter  44  is moved proximally of the housing  28  to provide an entry access for the tissue marker delivery system. 
         [0045]    As shown in  FIG. 3 , a vacuum source attached to vacuum line  46  is actuated, thereby generating a region of low pressure at the vacuum ports  50  to facilitate the prolapse of tissue  51   a  immediately adjacent to the tissue receiving port  42  into the hollow interior of hollow outer piercing needle  38 . 
         [0046]    Now again referring to  FIGS. 4-8 , the marking instrument  10  includes a tube  54 . The center wire  18  runs axially through a lumen  56  of the tube  54 , with the pull ring  24  being attached to the proximal end of the center wire  18 , proximally of the tube  54 . The distal end  20  of the center wire extends distally of the tube  54  and is joined to attachment members  14  and  16 , as described above. 
         [0047]    In operation, the tube  54  of the marking instrument is inserted into the patients body in the direction of the arrow  58 , as shown in  FIG. 4 , until the distal end  20  of the center wire  18  approaches the desired location, adjacent to or in the abnormal tissue or lesion. Because direct visual access to the targeted tissue is impossible, an aided visualization device, such as the stereotactic guidance system described above, is used to guide the distal portion of the marking instrument to the targeted tissue. Then, if the biopsy instrument shown in  FIGS. 1-3  is utilized to deploy the markers, the targeted tissue  51   a  ( FIG. 5 ) is vacuumed into the tissue receiving port  42 . Referring particularly to  FIG. 5 , once the distal end  20  of the center wire reaches the targeted, vacuumed tissue, the ring  24  is pulled away from the tissue in the direction of the arrow  60 . This action deploys the marker attachment members  14  and  16  as they are forced into a die formed in the tip  62  of the tube. This die may take any desired form, depending upon the desired deployed configuration of the attachment members  14 ,  16 . 
         [0048]    With reference to  FIG. 6 , tension continues to be applied to the ring  24 , in the direction shown by the arrow  64 , until the distal end of the marker is fully deployed. Forcing the attachment members into the die  62  causes them to extend outwardly, as illustrated, into the tissue. Their outward energy anchors the marker element  12  in the tissue for permanent implantation. The tips  66  and  68  of the attachment members may be configured to be less traumatic as an implant, or may alternatively be sharpened to provide a more secure grip. At full deployment, the width of the umbrella end of the marker element is preferably about 0.035 to 0.045 inches, though other sizes may be utilized within the scope of the invention. 
         [0049]    Now referring to  FIG. 7 , even after the attachment members  14  and  16  have been fully deployed, the pull ring  24  is pulled to further increase tension in the direction of the arrow  70 , until the center wire  18  is sheared at a point of weakness or detent  72  (see  FIGS. 4-6 ) which is established in the center wire  18  proximally of the tip  20 . Once failure has occurred, the pull ring  24  and the proximal portion  18 ′ of the center wire may be discarded as they are severed from the marker element  12  and remaining distal portion  18 ″ of the center wire. 
         [0050]    Finally, with reference to  FIG. 8 , to finish placing the marker element  12 , the tube  54  is withdrawn in the direction of the arrow  74 , as illustrated. The marker element is thereby permanently secured to locate the lesion site for future examination by known imaging methods. 
         [0051]    In the preferred embodiment, the marker element  12  is fabricated of stainless steel. However, many other biocompatible, radiopaque, implantable materials may be used for the marker element  12  as well, including, for example, titanium, tantalum, or nickel-titanium alloys. Additionally, while a 3-pronged umbrella end is shown and described, any number of prongs may be used, if desired. 
         [0052]    While it is preferred that the marker element  12  be deployed using the biopsy instrument described and shown in  FIGS. 1-3 , any instrument capable of delivering the element percutaneously may be utilized. Such instruments, for example, may include the hand-held biopsy gun described in U.S. Pat. No. Re. 34,056, entitled “TISSUE SAMPLING DEVICE” and issued to Lindgren et al. All of these types of instruments include a tube (typically a cannula or needle) which is adapted to enter the body, and would be capable of delivering the marker element. It is also within the scope of the invention to deliver the marker element through any tube which has access to the body or using optical medical instruments, such as endoscopes, arthroscopes, or laparoscopes, in which case the marker element is delivered to the desired tissue site from outside the body of the patient, through the body of the instrument. 
         [0053]    Now with reference to  FIGS. 9-11 , an alternative embodiment of a marking instrument  10   a  is shown, which is identical to the instrument  10  in all respects not shown or described herein. Portions of the instrument  10   a  corresponding to portions of the instrument  10  are designated by corresponding reference numerals followed by the letter a. 
         [0054]    The  FIG. 9  embodiment is substantially similar to the  FIG. 4  embodiment, in that the marking instrument includes a tube  54   a  which has a lumen  56   a , and may utilize a cannula, needle, or imaging instrument (i.e. endoscope, laparoscope, or the like) for access to a delivery site within the body and to aid in delivery. Again, as is the case for all succeeding embodiments, it is preferred that the tube  54   a  utilize the hollow outer piercing needle  38  of the biopsy instrument shown in  FIGS. 1-8 , though any other instrument which is capable of delivering a marker percutaneously or through a body orifice from a location outside the patients body may be utilized. A center wire  18   a  runs longitudinally through the lumen  56   a . At the proximal end of the center wire  18   a  is a deployment actuator or pull ring  24   a . At the distal end of the center wire is the marker element  12   a.    
         [0055]    A primary difference between the  FIG. 4  and  FIG. 9  embodiments is that the  FIG. 9  marker element  12   a  is preferably a generally “U” shaped element resembling a surgical ligating clip, having tips  66   a  and  68   a , which is captured by the distal looped end  20   a  of the twisted center wire. In operation, once the tips  66   a  and  68   a  of the marking element  12   a  reach the targeted tissue, the ring  24   a  is pulled rightwardly in the direction of the arrow  76  ( FIG. 10 ). This action retracts the base portion  78  of the marker element  12   a  into a forming recess  80  ( FIG. 9 ), wherein the recessed tube wall  82  forces prongs  86  and  88  together until tips  66   a  and  68   a  of the prongs  86  and  88 , respectively, contact or nearly contact one another ( FIG. 10 ). At this point, increasing tension applied to the pull ring  24   a  causes the wire  18   a  to fail at a point of weakness or detent (not shown) provided in the center wire at or near its tip end  20   a , thereby releasing the marker into the target tissue, as illustrated in  FIG. 11 . 
         [0056]    Referring now to  FIG. 12 , a second alternative embodiment of a marking instrument  10   b  is shown, which is identical to the instrument  10  in all respects not shown or described herein. Portions of the instrument  10   b  corresponding to portions of the instrument  10  are designated by corresponding reference numerals followed by the letter b. 
         [0057]    The  FIG. 12  embodiment is substantially similar to the  FIG. 4  embodiment, in that the marking instrument includes a tube  54   b  which has a lumen  56   b , and may utilize a cannula, needle, or imaging instrument (i.e. endoscope, laparoscope, or the like) for access to delivery site within the body and to aid in delivery. 
         [0058]    There are two primary differences between the embodiments of  FIGS. 4 &amp; 9  and that of  FIG. 12 . First, in the  FIG. 12  embodiment, a plurality of marker elements  12   b  (two are shown, though any number may be employed) may be preloaded into the tube  54   b , each comprising a pre-formed spring which is deployed through the tube&#39;s distal region  90  in an axial direction. Second, the nature of the deployment mechanism utilizes a compressive rather than tensile force. It may further be noted that, though end deployment of the marker elements in the  FIG. 12  embodiment is illustrated, they may be similarly deployed radially through a side port (not shown) in tube  54   b , or at any other angle, to accommodate delivery through an existing instrument (i.e. cannula, needle, endoscope, laparoscope, or the like). In being deployed radially, the distal region  90  is not used for passage of the marker element and could be utilized to house a piercing element (not shown) similar to that shown in  FIGS. 1-3 . Armed with the piercing element, this marker delivery system would not be dependent on a positioning system as described in  FIGS. 1-3  for placement at the tissue site and could be used alone in conjunction with a commercially available stereotactic or other guidance system. This concept may be applied to all subsequent embodiments except that illustrated in  FIG. 16 . 
         [0059]    Still with reference to  FIG. 12 , each marker element or spring  12   b  preferably includes a center coil  92  from which a pair of attachment members  94  and  96  extend, and is adapted to automatically attach itself to the target tissue by utilizing its own stored energy. Thus, in operation, each spring  12   b  is held in a compressed position within the tube  54   b . When it is desired to deploy the marker, a mandrel  98  is preferably utilized to push the spring  12   b  through the center lumen  56   b  and out through the distal open end  90  of the tube. Once the spring exits the tube, stored energy causes the attachment members  94  and  96  to expand outwardly, as shown. As this expansion occurs, the tips  102  and  104  of the attachment members  94  and  96 , respectively, anchor themselves into the tissue to permanently secure the marker element in the desired location. As with the  FIG. 4  embodiment, the tips  102  and  104  may be blunt to be less traumatic as an implant, or may alternatively be sharpened or barbed to provide a more secure grip. Once a spring has been deployed, the instrument may be repositioned to the next desired location for the immediate deployment of another marker until the supply in the tube  54   b  is exhausted, eliminating the need to remove and re-load the marking instrument  10   b  between each deployment. 
         [0060]    Again in this embodiment, the spring  12   b  may be fabricated of any known biocompatible, implantable, radiopaque material, though stainless steel is preferred. Additionally, the forces required to deploy the attachment members on the spring may be customize by varying the spring filar, dimensions, material, and/or the number of coils in the torsional part of the spring. 
         [0061]      FIG. 13  illustrates another alternative embodiment of the marking instrument  10 , which is identical to the instrument  10   b  of  FIG. 12  in all respects not shown or described herein. Portions of the instrument  10   c  corresponding to portions of the instrument  10   b  of  FIG. 12  are designated by corresponding reference numerals followed by the letter c. 
         [0062]    In actuality, the  FIG. 13  embodiment is substantially identical to that of  FIG. 12 , except for the shape of each spring  12   c , and is employed in precisely the same manner. Thus, to deploy a marker element  12   c , the mandrel  98   c  is utilized to push the spring  12   c  through the center lumen  56   c  and out through the distal open end  90   c  of the tube. As in the  FIG. 12  embodiment, the marker element travels in the direction of the arrow  100   c , until the attachment members  94   c  and  96   c  extend outwardly sufficiently to anchor themselves to the target tissue. Also, the  FIG. 13  embodiment is similar to the  FIG. 12  embodiment in that the instrument may be repositioned to immediately deploy another marker element without re-loading, and marker elements may be deployed radially through a side port in tube  54   c  (not shown), or any other angle, to accommodate delivery through an existing instrument (i.e. cannula, needle, endoscope, laparoscope, or the like). 
         [0063]      FIG. 14  shows still another alternative embodiment of the marking instrument  10 , which is also substantially identical to the instrument  10   b  of  FIG. 12  in all respects not shown or described herein. Portions of the instrument  10   d  corresponding to portions of the instrument  10   b  of  FIG. 12  are designated by corresponding reference numerals followed by the letter d. 
         [0064]    Again, the  FIG. 14  embodiment is substantially identical to those of  FIGS. 12 and 13 , except for the shape of the marker element or spring  12   d . A marker element  12   d  is deployed preferably using a mandrel  98   d  or the like to push the spring  12   d  through the center lumen  56   d  until it exits through the open end  90   d  of the tube. As in the  FIGS. 12 and 13  embodiments, the marker element travels in the direction of the arrow  100   d , until the tips  102   d  and  104   d  extend outwardly sufficiently to anchor themselves to the target tissue. 
         [0065]    In practice, a radiologist or other operator of the equipment can use a marker shaped like marker  12   b , as shown in  FIG. 12 , during one biopsy, then use a differently shaped marker, such as the marker  12   c  in the  FIG. 13  embodiment, or the marker  12   d  in the  FIG. 14  embodiment, during a subsequent biopsy procedure. The differently shaped markers permit the distinction between different biopsy procedures during future imaging procedures, as well as between biopsy sites which may be close in proximity, thereby improving the information available to the radiologist and thus the ability to monitor or diagnose the patient&#39;s future condition more precisely. 
         [0066]      FIG. 15  illustrates yet another alternative embodiment of the marking instrument  10 , which is also substantially identical to the instrument  10   b  of  FIG. 12  in all respects not shown or described herein. Portions of the instrument  10   e  corresponding to portions of the instrument  10   b  of  FIG. 12  are designated by corresponding reference numerals followed by the letter e. 
         [0067]    In this embodiment each marker element  12   e  is deployed distally through the open distal region  90   e  of the tube  54   e  by a mandrel  98   e , much as in the previous embodiments shown in  FIGS. 12 ,  13 , and  14 . The primary difference, however, between this embodiment and the previous embodiments is that, while the marker elements in the previous embodiments rely largely on the barbed nature of the spring to secure themselves in the tissue, in this embodiment, the springs are secured simply because of their significant expansion upon exit from the tube. This embodiment particularly lends itself to marking the boundaries of a biopsy or other desired site by defining the perimeter of the site. The expansion of the spring  12   e  causes the blunt edges  102   e  and  104   e  to press outwardly against the selected tissue, thereby wedging the spring securely into position. 
         [0068]    An advantage of this embodiment is that, because of the tight compression of the springs  12   e  within the tube  54   e , a larger number of markers can be inserted therein simultaneously, thereby permitting the deployment of more markers without having to pause and disengage to re-load. 
         [0069]    Another advantage the  FIG. 15  embodiment provides is the ability to deploy springs adapted to expand to a number of different sizes all from the same lumen. Larger sized springs would require more coils within a given lumen than smaller sized springs (not shown). 
         [0070]    It should be noted that the springs need not be limited to the configuration illustrated, but could include any spring of any configuration which expands to secure its position. While stainless steel is presently preferred, any other biocompatible, implantable, and radiopaque material could be used alternatively. Also as in the previous embodiments, marker elements may be similarly deployed radially through a side port in tube  54   e  (not shown), or any other angle, to accommodate delivery through an existing instrument (i.e. cannula, needle, endoscope, laparoscope, or the like). 
         [0071]    Still another alternative embodiment of the marking instrument  10  is shown in  FIG. 16 . In this embodiment, the marking instrument  10   f  comprises a tube  54   f . Wire segments  106  of any desired length are preloaded into the lumen  56   f , which runs along substantially the entire length of the tube  54   f . Once the needle is properly positioned, the marker elements  12   f  are deployed by pushing them out of the tip of the needle, through the side exit port  108 . A curved portion  110  of the lumen  56   f  comprises a die portion, and is adapted to form the wire segments  106  into helical marker elements  12   f  as they pass therethrough, pushed by a mandrel (not shown) or other known means from the tip of the needle through the exit port  108 . The nature of the curve or curves in the die portion  110  and preformed curves imparted into the wire segments determine the final shape (which resembles a partial or whole helix) and dimensions of the marker element. 
         [0072]    This embodiment is versatile in that it is capable of continuously deploying any number of marker elements without the necessity of re-loading, since all that is required is a continuous feed of wire segments into the proximal region of the tube  54   f . Furthermore, differently sized and shaped helixes may be delivered in the same procedure by utilizing marker wires of different diameters and/or preformed curves, which approximate different helical shapes as they pass through the die portion. Thus, loading a plurality of different sized wires into the needle yields a plurality of different shaped markers. 
         [0073]    Of course, as with the previous embodiments, although stainless steel is presently preferred, many different types of biocompatible, implantable, and radiopaque materials could be utilized within the scope of the invention. Also as in the previous embodiments, marker elements may be similarly deployed at different angles to accommodate delivery through an existing instrument (i.e. cannula, needle, endoscope, laparoscope, or the like). 
         [0074]    Unlike previous embodiments,  FIG. 16  preferably incorporates a piercing element  112  enabling this marker to be delivered without the aid of the positioning system described in  FIGS. 1-3  for placement at the tissue site. This embodiment could be used alone in conjunction with a commercially available stereotactic or other (i.e. ultrasonic) guidance system. 
         [0075]    Though a number of different embodiments of the conceptual invention have been described and shown, it is considered to be within the scope of the invention for the marking elements and delivery instruments to take on many other forms. For example, embolization coils like that illustrated in  FIG. 17  and designated with reference numeral  12   g  are well known in the medical field for placement into vessels such as veins and arteries in order to block off fluid flow abnormalities (such as fistulas and arteriovenous malformations). These coils have been made of various materials, including stainless steel, platinum, and gold, and are wound into configuration similar to that of a light bulb filament. They are generally placed into the body using a catheter or trocar system. The inventors in the present application have discovered that such coils may indeed also be used as marker elements, for permanent implantation in target tissue, in a manner similar to that described previously with respect to  FIGS. 1-16 . 
         [0076]    Marker elements of many other materials and configurations may be used as well. For example, one such multi-appendaged jack-shaped marker  12   h  is illustrated in  FIG. 18 . Additionally, small beads  12   i  ( FIG. 19 ) of calcium carbonate or other radiodense materials, which are highly visible by mammographic imaging, could be deployed as marker elements. One such application would be to place a plurality of such beads or pellets (each having a diameter of about 500.mu.) around the entirety of a breast lesion prior to the extraction procedure, which would then serve as guides to ensure that all of the margins had been removed. During subsequent imaging procedures, they would function to denote the location of the previous biopsy for reference purposes. 
         [0077]    Referring now to  FIG. 20 , yet another alternative marker element  12   j , which is of a woven construction, is illustrated. Other such marker materials may include adhesives and epoxies which would be injected at the biopsy site. Biodegradable polymers and other plastics could also be used, as long as they are biocompatible, implantable, and visible using an imaging system. 
         [0078]    While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.