Abstract:
Devices and methods are provided for securely affixing a medical instrument to desired tissue in a patient&#39;s body, using a fixation agent. Such medical instruments may comprise localization wires or tissue acquisition instruments, such as biopsy instruments, for example. In the case of tissue acquisition instruments, the inventors have discovered significant advantages for securely affixing the distal end of the tissue acquisition instrument to a particular tissue target area. For example, such an approach permits the imaging environment to be uncoupled from the procedural environment so that expensive and often unavailable imaging equipment, such as stereotactic imaging equipment, need not be used. In a preferred embodiment, a bonding agent, such as adhesive, surgical glue, or a solvent, is used as the fixation agent.

Description:
RELATED APPLICATIONS 
     This is a continuation application of application Ser. No. 10/010,213, filed Dec. 4, 2001 now U.S. Pat. No. 7,264,596, which is a continuation of Ser. No. 09/146,185, filed Sep. 1, 1998, now U.S. Pat. No. 6,540,693, which is a continuation-in-part of patent application Ser. No. 09/057,303, filed Apr. 8, 1998, now U.S. Pat. No. 6,331,166, which claims benefit to provisional patent application Ser. No. 60/076,973, filed Mar. 3, 1998, all of which applications are hereby incorporated herein by reference in their entirety and from which priority is hereby claimed under 35 U.S.C. §§119(e) and 120. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods and devices for ensuring that a medical instrument remains in a desired location within a patient&#39;s body during a medical procedure, and more particularly to methods and devices for affixing a distal end of the medical instrument to the desired location using adhesives. 
     BACKGROUND OF THE INVENTION 
     It is often desirable and frequently necessary to sample or remove a portion of tissue from 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, particularly cancer of the breast, there is a great emphasis on early detection and diagnosis through the use of screening modalities, such as physical examination, and particularly mammography, which is capable of detecting very small-abnormalities, often nonpalpable. When the physician establishes by means of a mammogram or other screening modality, such as ultrasound, that suspicious circumstances exist, a biopsy must be performed to capture tissue for a definitive diagnosis as to whether the suspicious lesion is cancerous. Biopsy may be done by an open or percutaneous technique. Open biopsy is a surgical procedure using a scalpel and involving direct vision of the target area, for removing the entire mass (excisional biopsy) or a part of the mass (incisionial biopsy). Percutaneous biopsy, on the other hand, is usually done with a needle-like instrument through a relatively small incision, blindly or with the aid of an artificial imaging device, and may be either a fine needle aspiration (FNA) or a core biopsy. In FNA biopsy, individual cells or clusters of cells are obtained for cytologic examination and may be prepared such as in a Papanicolaou 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 type of biopsy utilized depends in large part on circumstances present with respect to the patient, including the location of the lesion(s) within the body, and no single procedure is ideal for all cases. However, core biopsy is extremely useful in a number of conditions and is being used more frequently by the medical profession. 
     When an open surgical biopsy procedure is indicated, current practice dictates the use of lesion localization needles and devices, commonly referred to as “localization wires”, for use in localizing or marking non-palpable lesions and tumors within the body. These devices generally comprise a hypodermic needle or cannula which is inserted into the body under local anesthesia to the lesion or tissue of interest. The wire marker, or localization wire, is then passed through the cannula and extends through the lesion of interest so that the distal end thereof is anchored beyond the lesion. Thus, the lesion is marked for subsequent surgical procedures such as excision or biopsy. The anchoring procedure is typically accomplished by means of mechanical structure disposed at the distal end of the wire marker, such as a barb, hook, or the like, which is attached to surrounding tissue. After marking the lesion with the wire marker, the cannula is usually removed from the body, leaving the wire in place and extending from the body, for subsequent use by the surgeon during the biopsy procedure in identifying the lesion location. However, it often occurs that the barb or hook at the distal end of the wire marker attaches to something other than the tumor or lesion. For example, in the case of breast biopsies, the breast will typically be placed in compression during the imaging procedure in order to properly identify the location of the target lesion and place the localization wire. However, breast tissue is comprised of fibrous bands which, in compression, may be close to the target lesion and inadvertently engaged by the barb of the localization wire. Later, when the breast is released from compression prior to the surgical procedure, the fibrous bands will move away from the target lesion, and the distal end of the localization wire may thus move a substantial distance away from the target lesion. 
     It would be desirable, therefore, to develop a localization wire system and method wherein the distal end of the localization wire could be positively attached to the target lesion in order to minimize the possibility of migration of the distal end of the localization wire away from the target lesion between the imaging and surgical procedures. 
     In circumstances where a core biopsy procedure is indicated, various systems are available. Such systems are shown, for example, in U.S. Pat. No. 5,526,822 to Burbank et al, which discloses a probe having a laterally disposed tissue receiving port at the distal end thereof for acquiring relatively small tissue samples, and in U.S. Pat. No. 5,111,828 to Kornberg et al., which discloses a probe having an axially disposed tissue receiving port at the distal end thereof for acquiring relatively large intact tissue samples. Both of these patents are expressly incorporated by reference herein. 
     U.S. application Ser. No. 09/057,303 to Burbank et al., commonly assigned with the present application and expressly incorporated by reference herein, discloses still another core biopsy apparatus, which advantageously permits the acquisition of tissue samples which are larger in diameter than the diameter of the instrument lumen, thereby greatly increasing the chances of completely removing the target lesion and leaving “clean” margins thereabout. 
     As in the case of localization wires, there is some risk in using any of the foregoing devices that the distal end of the instrument will migrate away from the target lesion during the biopsy procedure, thereby reducing the likelihood of removing target tissue. Heretofore, in the case of core biopsy procedures, the risk of this occurrence is minimized by employing image guidance techniques during the entire tissue removal procedure. For example, in the case of the &#39;822 Burbank et al. patent, a stereotactic imaging guidance system is typically utilized during the disclosed procedure. One disadvantage of this approach, however, is that the patient&#39;s breast must remain in compression during the entire procedure, with attendant discomfort and increased procedural difficulty, in order to properly utilize the imaging equipment. Furthermore, stereotactic imaging equipment or other suitable alternatives can cost as much as $400,000 or more and is not in the usual inventory of a typical community hospital. It would therefore be quite advantageous if a method and apparatus could be developed which would permit the uncoupling of the imaging environment from the procedural environment without undue risk that the active or cutting end of the core biopsy instrument would migrate away from the target lesion during the interval between the imaging procedure and the biopsy procedure. 
     SUMMARY OF THE INVENTION 
     The present invention solves the problems outlined above by describing devices and methods for securely affixing a localization wire to desired tissue in a patient&#39;s body, so that after the patient is moved from the imaging environment to the procedural environment, the practitioner will have assurance that the localization wire is still accurately placed. Additionally, devices and methods are described for ensuring that the distal end of a tissue acquisition instrument, such as a biopsy instrument, is securely affixed to a particular target area, such as a lesion, in a patient&#39;s body, thereby advantageously permitting the imaging environment to be uncoupled from the procedural environment so that expensive and often unavailable imaging equipment, such as stereotactic imaging equipment, need not be used. 
     More particularly, in one aspect of the invention a medical device is provided comprising a tube having a distal end, a proximal end, and a longitudinal axis, wherein the device is adapted for placement of the distal end thereof into a patient&#39;s body at a desired location. The medical device includes a fixation agent, which may comprise any one of a bonding agent, a mechanical fixation agent, or an electrosurgical coagulation element, disposed on the distal end thereof, which is adapted for affixing the distal end of the medical device at the desired location. 
     The medical device may comprise for example, a localization wire for use in connection with an open biopsy procedure. Alternatively, the device may comprise a tissue acquisition instrument, such as a biopsy instrument. In the preferred embodiment, the fixation agent is a bonding agent, comprising a surgical adhesive, glue, or solvent. 
     In another aspect of the invention, a tissue acquisition instrument is provided for retrieving body tissue, having a longitudinal axis and which comprises a distal end adapted for entry into a patient&#39;s body, a cutting element disposed on the instrument for cutting surrounding tissue, and structure disposed on the distal end for securing the tissue acquisition instrument at a predetermined desired location, in order to ensure that the tissue acquisition instrument remains in place during a tissue acquisition procedure so that desired tissue is properly acquired. 
     In yet another aspect of the invention, a method of performing a medical procedure is provided, using a medical device comprising a tube having a distal end, a proximal end, and a longitudinal axis. The method first comprises the step of placing the distal end of the tube in a patient&#39;s body, so that the distal end is disposed in a desired tissue location. Then, a bonding agent is dispensed for the tube into tissue surrounding the distal end, so that the distal end of the tube becomes affixed to the desired tissue location. 
     In still another aspect of the invention, a method is provided for performing a tissue acquisition procedure using a tissue acquisition instrument having a distal end, a proximal end a longitudinal axis, and a cutting element. In this method, the distal end of the instrument is placed into a patient&#39;s body, so that the distal end is disposed in a desired tissue location. Then, the distal end of the instrument is affixed to the desired tissue location, so that the instrument does not move relative to the desired tissue location during the tissue acquisition procedure. The-cutting element is then actuated to acquire one or more tissue samples. 
     The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a schematic plan view of a first embodiment of the present invention, illustrating a catheter for a localization wire introduction and infusion system wherein an introducer needle for introducing the localization wire into a patient&#39;s body remains in place during securement of the localization wire to surrounding tissue using a bonding agent; 
         FIG. 2  is a schematic plan view of the introducer needle used in conjunction with the catheter of  FIG. 1 ; 
         FIG. 3  is a schematic plan view of one embodiment of a localization wire which may be used in conjunction with the infusion system shown in  FIGS. 1 and 2 ; 
         FIG. 3   a  is a perspective view of the distal end of the embodiment shown in  FIGS. 1-3 , wherein the introducer needle is inserted through the lumen of the catheter; 
         FIG. 3   b  is a perspective view of the distal end of the embodiment shown in FIGS.  1 - 3 , wherein the introducer needle is inserted through the lumen of the catheter, and its position within the catheter lumen is shown in phantom for illustrative purposes; 
         FIG. 3   c  is a perspective view similar to  FIG. 3   a , wherein the localization wire is inserted through the lumen of the catheter; 
         FIG. 4  is a perspective view of a second embodiment of the present invention, illustrating a second embodiment of a localization wire introduction and infusion system, wherein an introducer needle for introducing the localization wire into a patient&#39;s body is removed during securement of the localization wire to surrounding tissue using a bonding agent; 
         FIG. 5  is schematic plan view of the catheter for the system illustrated in  FIG. 4 ; 
         FIG. 6  is a schematic plan view of the introducer needle for the system illustrated in  FIGS. 4 and 5 ; 
         FIG. 6   a  is a perspective view of the distal end of the embodiment shown in  FIGS. 4-6 , wherein the localization wire is inserted through a lumen of the catheter; 
         FIG. 7  is a schematic plan view of a second embodiment of a localization wire which may be utilized in conjunction with either of the embodiments of  FIGS. 1-3  or  4 - 6 ; 
         FIG. 8  is a schematic view in isolation illustrating one embodiment of the present invention for storing and releasing a bonding agent which is dispensed from a medical instrument for affixing the medical instrument to surrounding tissue in a patient&#39;s body; 
         FIG. 9  is a perspective view of a third embodiment of the present invention, illustrating a catheter which may be used as a localization wire and infusion system; 
         FIG. 10  is an enlarged perspective view of the distal end of the cannula illustrated in  FIG. 9 , showing in greater detail the perforations in the distal end for infusing a bonding agent to surrounding tissue; 
         FIG. 11  is a perspective view of a modified version of the embodiment shown in  FIGS. 9 and 10 , wherein the cannula is comprised of a braided polymer tubing and the interstices between the braids function as the infusion openings for infusing bonding agent to surrounding tissue; 
         FIG. 12  is a perspective view of another modified version of the embodiment shown in  FIGS. 9 and 10 , wherein the cannula is comprised of a coil and the interstices between expanded coils function as the infusion openings for infusing bonding agent to surrounding tissue; 
         FIG. 13  is a perspective view of a biopsy instrument constructed in accordance with the principles of the present invention; 
         FIG. 14  is a perspective view of a second modified embodiment of a biopsy instrument having an expandable Mallicot structure at its distal end for anchoring the instrument at a particular tissue site; 
         FIG. 15  is a perspective view of a third modified embodiment of a biopsy instrument having a modified expandable Mallicot structure at its distal end for anchoring the instrument at a particular tissue site; 
         FIG. 16  is a perspective view of a fourth modified embodiment of a biopsy instrument having an expandable linkage structure at its distal end for anchoring the instrument at a particular tissue site, wherein the linkage structure is shown in its retracted position; 
         FIG. 17  is a perspective view of the embodiment shown in  FIG. 16 , wherein the linkage structure is shown in its expanded position; 
         FIG. 18  is a perspective view of a fourth modified embodiment of a biopsy instrument having an extendable “bottle brush” structure at its distal end for anchoring the instrument at a particular tissue site; 
         FIG. 19  is a perspective view of a fifth modified embodiment of a biopsy instrument having a nitinol flap structure at its distal end, expandable upon retraction of a surrounding sleeve, for anchoring the instrument at a particular tissue site; 
         FIG. 20  is a perspective view of a sixth modified embodiment of a biopsy instrument having a rolled stent structure at its distal end which unrolls upon retraction of a surrounding sleeve, for anchoring the instrument at a particular tissue site; 
         FIG. 21  is a perspective view of a seventh modified embodiment of a biopsy instrument having expandable spiral wires at its distal end for anchoring the instrument at a particular tissue site; and 
         FIG. 22  is a perspective view of an eighth modified embodiment of a biopsy instrument having an expandable basket at its distal end for anchoring the instrument at a particular tissue site. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now more particularly to the drawings,  FIGS. 1-3   c  illustrate a first embodiment of the invention, wherein a medical instrument  10  ( FIGS. 3   a - 3   c ) comprises a catheter  12  ( FIGS. 1 ,  3   a - 3   c ), an introducer needle  14  ( FIGS. 2 ,  3   a , and  3   b ), and a localization wire  16  ( FIGS. 3 ,  3   c ). In this embodiment, which may be styled as a “needle in” infusion system, the introducer needle  14  comprises a sharp distal end  18 , which is inserted through an entry hole  20  in the catheter  12  ( FIG. 1 ), so that its tip  18  extends beyond the distal end  22  of the catheter  12 , as shown in  FIGS. 3   a  and  3   b . The introducer needle  14  may include a stop  24  having an enlarged diameter, which is adapted to engage the distally tapering inner sidewall of the catheter  12  at a predetermined point, as generally shown particularly in  FIG. 3   b , to ensure that the tip  18  properly extends beyond the distal end  22  of the catheter  12 . The introducer needle  14  and catheter  12  together are then introduced into a patient&#39;s body (not shown), using known imaging techniques for guiding localization wires to the site of tissue to be excised (“target tissue”). 
     Once the catheter  12  and introducer needle  14  are in position relative to the target tissue, the introducer needle  14  is removed proximally from the catheter  12 , and the localization wire  16  is inserted distally through the entry hole  20  and pushed distally through the lumen in the catheter  12 , so that the distal end of the localization wire  16  extends distally of the distal end of the introducer needle and catheter, as shown in  FIG. 3   b . Indicator marks  25  preferably assist the practitioner in ensuring that the localization wire is properly inserted to the required depth. 
     Localization wires such as the wire  16  typically include some type of mechanical anchoring means, such as a barb or hook  26 , for securing the distal end of the localization wire  16  in position behind the target tissue. However, this approach is often inadequate, as discussed supra in the Background portion of the specification, because the tissue to which the hook  26  becomes attached will often shift relative to the target tissue between the imaging step of the medical procedure, which is usually a biopsy, such as a breast biopsy, and the ensuing surgical step, which usually takes place in a different area of the hospital and requires transportation and resultant jostling of the patient from the radiology department to the operating room. The present invention, therefore, contemplates an advantageous additional step of employing a bonding agent, which may comprise any known material which is capable of creating a bond between the distal end of the medical instrument  10  and surrounding tissue. Once the localization wire is properly placed at the desired target tissue site, under imaging guidance, the bonding agent is dispensed from the distal end of the medical instrument to the surrounding tissue to create the desired bond. In the embodiment of  FIGS. 1-3   a , a plurality of infusion ports  28  are disposed along the length of the distal end of the catheter  12 . Any number of infusion ports (one or more) may be employed in order to optimize the flow of bonding agent to the tissue, and they are preferably staggered circumferentially about the catheter in order to evenly deliver bonding agent about the circumference of the instrument  10 . Various delivery means may be employed as well. For example, in the illustrated embodiment, the catheter  12  comprises a proximal hub  30  ( FIG. 1 ), including a stopcock  32  which is engageable with a syringe (not shown) containing the bonding agent. When the localization wire is properly positioned, the practitioner injects the bonding agent into the lumen (not shown) of the catheter using the syringe with sufficient pressure that it flows distally through the lumen and is infused into surrounding body tissue through the infusion ports  28 . The resultant bonding of the distal end of the localization wire  16  to the surrounding target tissue ensures with much greater certainty than the use of mechanical attachment means alone, such as the hook  26 , that the localization wire will be properly positioned when the surgical procedure commences, thereby improving the likelihood that the proper target tissue will be excised with a minimum incision and resultant trauma to the patient. 
     Preferred bonding agents include any known effective biocompatible bonding materials, such as surgical adhesives, including cyanoacrylate, fibrin glue, and solvents. 
     An alternative to injection of the bonding agent through the lumen of the medical instrument  10  is illustrated in  FIG. 8 . The bonding agent  33  may be stored in a rupturable container  34  which is disposed in the distal end of the medical instrument  10 , adjacent to the infusion ports  28 . When it is desired to release the bonding agent  33  through the infusion ports, a puncturing device  36  may be actuated by the practitioner to rupture the container  34 . In the illustrated embodiment, the device  36  comprises a simple “spear” which is actuated distally to rupture the container, but it may alternatively comprise any suitable configuration for functioning equivalently. Additionally, it is within the scope of the invention to employ a chamber for containing the bonding agent which includes a valved port, wherein the valve is actuated to an open position by the practitioner to release the bonding agent. Various other embodiments for accomplishing this function, as would be known to one of ordinary skill in the art, are deemed to fall within the scope of the invention as well. 
     Once the localization wire is securely bonded to the surrounding tissue, the practitioner may withdraw the catheter and introducer needle assembly, leaving the localization wire in place to mark the target tissue for the ensuing surgical step in the biopsy or other medical procedure. 
       FIGS. 4-7  illustrate a second “localization wire” embodiment, wherein like elements to those shown in the first embodiment are designated by like reference numerals, succeeded by the letter “a”. This system may be styled as a “needle out” infusion system. In this embodiment, the catheter  12   a  comprises a dual lumen extrusion, including first and second lumens  38  and  40 , respectively ( FIG. 6   a ). The first lumen  38  accommodates the bonding agent, while the second lumen accommodates the localization wire. The catheter  12   a  further includes a dual lumen proximal hub  42 , which comprises a localization wire entry port  44  and a stopcock  32   a.    
     In operation, the introducer needle  14  a is disposed coaxially outside of the catheter  12   a , as illustrated in  FIG. 4 , and the instrument  10   a  is inserted into the patient&#39;s body in known fashion, under conventional imaging guidance. The localization wire  16   a  is inserted distally through the port  44 , either before or after introduction of the instrument  10   a  into the patient&#39;s body. As in the first embodiment, once the instrument  10   a  is placed, the localization wire  16   a  is advanced distally until the indicator marks  25   a  indicate to the practitioner that the distal hook  26   a  is distal of the distal end of the catheter  12   a  and of the target lesion, as shown by the imaging equipment. The localization wires of  FIGS. 3 and 7  may be used interchangeably in either of the two disclosed embodiments, and are substantially identical except that the localization wire  16   a  includes filaments  46  near its distal end which provide additional surface area for bonding. 
     As in the previous embodiment, once the localization wire is in the proper position, bonding agent is injected into the catheter  12   a , preferably using a syringe which is engaged with the stopcock  32   a , so that the bonding agent flows distally through the first lumen  38  and is infused through the infusion ports  28   a . Again, the infusion ports may be disposed about the catheter, in rows offset by 90 degrees with respect to one another, or otherwise staggered so that the bonding agent is evenly disposed about the catheter. Alternatively, as in the previous embodiment, the bonding agent may be stored in the distal end of the instrument  10   a  using an apparatus like that illustrated in  FIG. 8 . It is within the scope of this invention, as well, to store or inject two or more bonding agent compounds, comprising a reactant and a catalyst, at the injection site, and to mix the reactant and catalyst together at the appropriate time to catalyze a bonding agent. 
     Once the bonding agent has been injected, but before it has solidified, the catheter  12   a  and introducer needle  14   a  are withdrawn from the patient&#39;s body, leaving the localization wire in place. 
     Still a third embodiment, which functions in a manner equivalent to that of a localization wire, is illustrated in  FIGS. 9 and 10 . In this embodiment, a catheter  48 , which comprises a proximal hub  50 , a distal end  52 , and a lumen  54 , is insertable into a patient&#39;s body using conventional image guidance techniques, so that the distal end  52  is disposed at a desired target tissue site. Once properly located, a bonding agent  33  is infused through one or more infusion ports  56  to surrounding target tissue, in order to bond the distal end of the catheter  48  to the surrounding tissue. Again, as in the previous embodiments, the bonding agent may be injected into the lumen  54  of the catheter through the proximal hub  50 , or may alternatively be stored in the distal end  52  of the catheter and selectively released at the desired time. 
       FIGS. 11 and 12  illustrate two alternative embodiments for the outer tube  58  of the catheter in any of the foregoing embodiments. In  FIG. 11 , the tube  58  comprises a stainless steel braid, the proximal end  60  of which is encapsulated by a polymer, such as polyamide, and the distal end  62  of which is exposed. The exposed distal end is preferably approximately 1-2 centimeter (cm) in length, though it may be longer or shorter if desired. In operation, interstices  64  between bands  66  of the exposed braided portion  62  function as openings for permitting infusion of bonding agent to surrounding tissue, instead of the infusion ports disclosed in the preceding embodiments. If the exposed braided portion is expanded, the interstices will be enlarged and will permit the flow of more bonding agent therethrough. 
     In a manner in some respects similar to the embodiment of  FIG. 11 , the  FIG. 12  embodiment comprises an outer tube  58  having a sleeve  68  surrounding a coil  70  of suitable material. In the distal end of the tube  58 , the coil  70  may be stretched to create interstices  72  between bands  74  of the coil. Bonding material may be infused, as desired, outwardly through the interstices  72  of the expanded coil, and then through holes  76  in the sleeve  68  to surrounding tissue. Alternatively, the sleeve could be retracted to expose the coil, in which case the sleeve holes  76  would be unnecessary. 
       FIG. 13  illustrates the distal end of a medical instrument  78  which is shown and described in co-pending application Ser. No. 09/057,303, commonly assigned with the present application and expressly incorporated by reference herein. The instrument  78  comprises a tissue acquisition or biopsy instrument and preferably includes a tip  80  having an electrosurgical element  82  for entering tissue, and a shaft  84 , on which is disposed a radially extendable and retractable cutting element or wire  86 . The cutting element  86  is preferably energized by RF energy provided by an electrosurgical generator. 
     In operation, the instrument  78  is moved axially to a position wherein the distal tip  80  is preferably distal to a target lesion or tissue to be removed, using a suitable imaging technique. In the prior art, such imaging techniques for biopsy procedures and the like typically include the use of a stereotactic or sonographic imaging system, both of which are relatively expensive and not always available in an average community hospital. This approach is designed to combine the imaging and cutting steps so that both occur simultaneously. For example, in the case of a breast biopsy procedure, the breast is clamped in order to effectively utilize the imaging equipment, after which the instrument is inserted into the breast under imaging guidance to the lesion location. Then, under continued imaging guidance, the cutting element is actuated and the target tissue removed. 
     However, an important advantage of the present invention is the ability to “uncouple” the imaging environment from the procedural environment in a typical surgical or biopsy procedure, and the resultant important ability to utilize unmodified mammography equipment, readily available in most hospitals, to position the distal end of the instrument during the imaging step, rather than expensive and specialized stereotactic equipment. Then, the procedural step may occur later, in another area of the hospital. In the case of breast biopsies, this “uncoupling” also permits the patient&#39;s breast to be unclamped for the procedural step, resulting in increased patient comfort and easier working conditions for the practitioner. 
     These advantages are made possible because the inventive apparatus and technique permits the securement of the distal end of the instrument to the target tissue or lesion with sufficient confidence that the patient may be moved to the procedural environment without fear of having it slip away from the target tissue. This securement is accomplished using a fixation agent, which preferably comprises a bonding agent like that disclosed in connection with the foregoing localization wire and catheter embodiments. In a manner similar to those embodiments, once the instrument is positioned in a desired position, the bonding agent is injected into a lumen of the instrument, or, alternatively, in a manner like that described supra, released from a container or chamber in the distal end of the instrument, so that it may be infused from one or more infusion ports  88  disposed on the distal end of the instrument. Preferably, the ports  88  are disposed on a bushing or sleeve  90  which has a linear slot  92  for permitting passage of the cutting element  86  as it is extended and retracted radially, and which is rotatable relative to the shaft  84 . Thus, when the bonding agent is infused to the surrounding tissue, so that the bushing  90  is affixed in place relative to the surrounding tissue, the cutting element  86  will still be rotatable on the underlying shaft  84  in order to permit circumferential cutting of tissue, as desired, during the later procedural step. Suitable care is taken that only a sufficient amount of bonding agent is dispensed to bond the bushing to surrounding tissue, and not the shaft or tip of the instrument, in order that the shaft and tip continue to be rotatable relative to the bushing. 
     Of course, the bushing  90  may be constructed in number of alternative ways, as will be apparent to those of ordinary skill in the art. For example, as shown in  FIGS. 11 and 12 , the bushing could be comprised of a braided or coil material, so that interstices between braids or coils thereof could function as the infusion openings. 
     Rather than using a bonding agent, a mechanical fixation agent may be utilized to secure the distal end of the instrument to surrounding tissue. For example,  FIG. 14  illustrates an alternative embodiment to that of  FIG. 13 , wherein a mechanical fixation structure  94  is utilized to secure the distal end of the instrument to surrounding tissue, rather than a bonding agent. In this embodiment, wherein like elements to those of  FIG. 13  are designated by like reference numerals, succeeded by the letter “b”, the mechanical fixation structure  94  comprises an expandable Mallicot structure, having a rotatable bushing  90   b  and a plurality of expandable bands  96 . Actuating pushrods  98 , of which there are preferably four, arranged circumferentially 90 degrees apart, are provided to actuate the bands  96  between their expanded positions (as shown), in which they are positioned to anchor the distal tip  80   b  to the desired tissue site, and their retracted positions. 
       FIG. 15  illustrates another modified embodiment which is similar to that of  FIG. 14 , and wherein like elements to those of  FIG. 14  are designated by like reference numerals, succeeded by the letter “c”. The only difference between this embodiment and the  FIG. 14  embodiment is that the bands  96   c  are split at their centers, to form protruding portions  100 , for the purpose of permitting further radial extension of each band and to also permit the protruding portions  100  to attach themselves to adjacent tissue. 
       FIGS. 16 and 17  schematically illustrate still another modified mechanical fixation structure  94   d , comprising a linkage, which may be substituted for the structures  94  and  94   c  of  FIGS. 14 and 15 , respectively, wherein  FIG. 16  illustrates the linkage in its retracted configuration and  FIG. 17  illustrates it in its radially expanded configuration. 
       FIG. 18  schematically illustrates yet another modified mechanical fixation structure  94   e , comprised of a plurality of radially retractable and extendable wires  102 . 
       FIG. 19  schematically illustrates still another modified mechanical fixation structure  94   f , of the bone anchor type, comprised of a nitinol tube  104  and radially expandable flaps  106 . 
     In  FIG. 20 , there is shown another modified mechanical fixation structure  94   g , comprised of a rolled stent which may be unrolled to expand radially and provide an anchoring function by axially retracting a sleeve  108 . 
       FIG. 21  shows still another modified mechanical fixation structure  94   h  comprised of a plurality of extendable wires  110 . 
       FIG. 22  illustrates a modified mechanical fixation structure  94   i  which comprises a radially expandable and retractable basket. 
     Any of the foregoing mechanical fixation structures may be interchangeably employed in the embodiments of  FIGS. 14 and 15 , and it is within the scope of this invention to also employ other mechanical fixation structures which are known conventionally for anchoring medical devices in the body. 
     Still another means for bonding the distal end of the instrument  78  to surrounding tissue, which is within the scope of the present invention, is to apply RF energy to the tissue, using an electrosurgical coagulation element. The electrosurgical coagulation element may comprise one of the existing electrosurgical elements  82  or  86 , or preferably another coagulation element  112  ( FIG. 13 ) which may be disposed on or near the bushing  90 . Activation of the coagulation element  112  for a short interval coagulates the tissue-surrounding the tissue, thereby bonding the bushing to the tissue. Alternatively, the element  112  could comprise a heating rod for cauterizing tissue, similar to the function of a branding iron, to produce the same type of bonding effect by “sticking” the cauterized tissue to the distal end of the instrument. 
     This approach may also be utilized in the localization wire embodiments illustrated in  FIGS. 1-12 , by employing an electrosurgical coagulation element on the distal end thereof, which is connected to a suitable electrosurgical generator, or, alternatively, by employing an electrical heating element for cauterizing tissue. 
     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.