Abstract:
A biopsy instrument includes a canula slidingly disposed in a finger tube having a finger at its distal end. By forward displacement of the finger tube relative to the canula the finger is inserted into an opening in the canula wall near its cutting front edge. Thereby a piece of tissue located inside the canula is severed from living tissue. The instrument has a steel spring compressed against a force of at least 35 N for displacing the canula and the finger tube in the tissue cutting step. The stopper on which the moving canula impacts includes an element of an impact damping design. The impact damping element is made of high-impact grade ABS-polymer or a polymer with similar physical properties. It can be used also with known biopsy instruments having a moving canula and/or stylet driven by a powerful spring. Also described is a loading assembly for a biopsy apparatus incorporating the biopsy instrument.

Description:
This is a division of application Ser. No. 09/090,908, filed Jun. 5, 1998, now U.S. Pat. No. 6,126,617 which is a continuation-in-part of application Ser. No. 08/783,204, filed Jan. 14, 1997, now U.S. Pat. No. 5,788,651, which is a division of application Ser. No. 08/378,402, filed Jan. 26, 1995, now U.S. Pat. No. 5,655,542, issued Aug. 12, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a biopsy instrument, and to methods and apparatus for collecting tissue samples or the like from humans or animals, in particular by excising a segment from a tissue, using the biopsy instrument. The invention also relates to a loading assembly for a biopsy instrument and an impact damping element for biopsy instruments. 
     2. Description of the Related Art 
     The invention departs from an apparatus for collecting tissue samples by excising a segment from tissue, and a corresponding method for harvesting of tissue samples described in U.S. Pat. No. 5,655,542 (Weilandt), the entire disclosure of which is incorporated by reference into this specification. 
     In this specification, the terms “proximal” and “distal” are used with respect to the person extracting a biopsy sample. Thus, the proximal end of a biopsy apparatus is its rear end, proximate the practitioner, and pointing away from the patient. 
     The biopsy instrument of the &#39;542 patent includes a first part having an end with means for penetrating a tissue at the end, and a wall having an opening extending through the wall of the first part; and a second part adapted for being slidingly disposed on the first part, excision means for separating a segment of the tissue then penetrated by the first part provided on the second part such that sliding movement of the second part on the first part in one direction causes the excision means to pass through the opening in the wall of the first part thereby separating a segment of the tissue for extraction. 
     The method of harvesting biopsy samples of the &#39;542 patent includes the steps of injecting the biopsy instrument into tissue to a position proximal of a sample to be taken; displacing simultaneously the first part and the second part of the biopsy instrument for reception of the sample in the first part; displacing the second part to sever the sample from the tissue. 
     The first part may take the form of a canula and the second part that of a tube in which the canula is slidingly arranged. The tube is provided with a finger at its distal end, the finger entering an opening in the canula wall in the tissue-severing step when the tube is displaced in a distal direction with respect to the canula. 
     The joint displacement of the first part and the second part following the injection step is accomplished by spring means, in particular a steel coil. Compression steel coils have been found to work well in practice, except for very powerful springs providing high acceleration to the combination of the first and the second part. High acceleration is attractive since, thereby, the use of separate driving force for the second step becomes superfluous, the displacement of the second part with respect to the first part being accomplished through the inertia of the second part. Moreover, high acceleration allows for less variation in sample quality when using the instrument with a variety of tissues. The loading of a biopsy instrument provided with powerful spring means which have to be compressed in the loading procedure constitutes another problem. 
     SUMMARY OF THE INVENTION 
     The present invention provides a biopsy instrument that can be reliably driven by strong spring means. The invention also provides a means for damping the impact of a stylet or canula in a biopsy instrument. In addition, the invention provides a loading assembly for loading a biopsy instrument, in particular one with a powerful compression spring. 
     The invention is a biopsy instrument of the aforementioned kind including means for damping oscillations of the first part with respect to the second part arising from the sudden stop of the first part at the end of the first step when hitting a stopper and that of the second part at the end of the second step. On impact the thin-walled tubiform first and second parts become elongated in their axial direction. In general the canula and the finger tube of electropolished steel have very thin walls of from about 0.05 to 0.1 mm thick while their length varies from about 15 to about 20 cm. 
     In experiments with strong steel coils, oscillations of amplitudes of up to 1.15 mm were observed. In addition, the first and second part do not necessarily oscillate in phase; they may even oscillate in opposite phase. Undampted, the oscillations often damaged the finger, resulting in incomplete severing of the sample or breakage of the finger. The damage occurs by the finger hitting the distal rim of the opening in the tube wall. Thereby the finger is excessively bent or broken. 
     According to the present invention, oscillation damping means are provided by appropriate design of the stopper stopping the movement of the first part. With reference to the preferred embodiment of the &#39;542 patent, the first stopping element is the plunger stop  960  modified according to the teaching of the present invention. By using a powerful steel compression spring the actuator coil  94  can be dispensed with. The displacement of the second part in relation to the first part then is caused entirely by inertia. 
     It is preferred for the steel coil of the biopsy instrument to exert a force of 35 N and more in a compressed state. Particularly preferred is a coil exerting a force of at least 50 N, most preferred of at least 65 N. 
     A reduction of oscillation by damping so as to keep oscillation of the first part with respect to the second part below 0.4 mm provides a satisfactory result and is preferred. Even more preferred is to keep oscillation within 0.35 mm, even within 0.30 mm and less. 
     A biopsy instrument according to the invention combines a powerful steel compression spring of the kind described above, an impact damping means to reduce oscillation of a canula with respect to a finger tube slidingly disposed on the canula arising on impact of the canula holder on a stopper, and a design dispensing with the use of spring means to displace the finger tube in a distal direction after the canula has been stopped by the stopper. 
     The impact damping means of the invention can also be advantageously applied to stop (decelerate) canulas and stylets in biopsy instruments other than that of U.S. Pat. No. 5,655,542, in particular canulas and stylets accelerated by a powerful compression spring, such as one which can be compressed to more than 35 N, preferably more than 50 N, most preferred more than 65 N. The damping means of the invention preferably constitutes an acrylonitrile-butadiene-styrene copolymer (ABS) having a yield tensile strength above 35 Mpa and an Izod impact strength of more than 325 J/m, or any other medical grade polymer or other material meeting these requirements. 
     The loading assembly of a biopsy apparatus incorporates, in a housing, the biopsy instrument according to the invention includes a loading arm swivellingly attached at its one end to the housing, an intermediate arm swivellingly attached at its one end to the loading arm and at its other end to a catch holding the canula holder during tensioning and in a tensioned position with respect to a tension spring or during compression, or in a compressed position with respect to a compression spring (the latter being preferred). The catch is displaceable in a proximal direction against the resistance of the spring and is adapted to be held there for intentional release. It is obvious that this loading assembly can also be advantageously used for tensioning or compressing spring means arranged for displacement of one or several elements of a biopsy apparatus different from that of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the present invention will become obvious from the study of a preferred but not limiting biopsy instrument and a corresponding apparatus according to the invention which is illustrated in a drawing of which the individual figures are described briefly as follows: 
     FIG. 1 illustrates a canula with its holder, in a perspective view from a distal viewpoint, only the rear (proximal) portion of the canula being shown; 
     FIG. 2 illustrates a finger tube with its holder, in the same view as in FIG. 1, only the rear (proximal) portion of the finger tube being shown; 
     FIG. 3 illustrates the canula and finger tube holders, in a mounted state before and during a first step of an excision procedure, in the same view as in FIGS. 1 and 2; 
     FIG. 4 illustrates the canula, the finger tube, and their respective holders, in a mounted state in the same view as before, at the end of a second step of the excision procedure; 
     FIG. 5 illustrates a stopper, in the same view as before; 
     FIG. 6 illustrates the canula holder, the finger tube holder, and the stopper, in a mounted state at the end of the second step, in the same view as before; 
     FIG. 7 illustrates the assembly of FIG. 6 before and during the first step, in a symmetric longitudinal section; 
     FIG. 8 illustrates a biopsy apparatus incorporating the biopsy instrument of FIGS. 1-7, in a loaded condition and in a symmetric longitudinal section; 
     FIG. 9 illustrates the apparatus of FIG. 8, in a released condition at the end of the first step, in the same view as in FIG. 8; 
     FIG. 10 illustrates the apparatus of FIG. 8, in a released condition at the end of the second step, in the same view as in FIG. 8; 
     FIG. 11 illustrates the apparatus of FIG. 8, after withdrawal of the finger from the canula but before sample expulsion and loading, in the same view as in FIG. 8; 
     FIG. 12 a  illustrates the catch of the loading assembly of the apparatus of FIG. 8, in a plan view from above; 
     FIG. 12 b  illustrates the catch of FIG. 12 a , in the same view as the apparatus of FIGS. 8-11. 
     Indications of lateral direction such as ‘from above’, ‘underside’, ‘top side’ are defined by the view of FIGS. 8-11. The steel coil compression spring is only shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The biopsy instrument illustrated in FIGS. 1-7 includes a canula  101 , a finger tube  201 , and a stylet  301  of the same kind as in U.S. Pat. No. 5,655,542, where the design and function of these elements is explained in detail and thus need not be repeated here. In some of the figures of the present specification rear (proximal) end portions of the canula  101 , the finger tube  201 , and the stylet  301  are shown to illustrate their relationship with their respective holders  100 ,  200 ,  300 , each made in one piece of a polymer material, preferably an ABS polymer (acrylonitrile-butadiene-styrene copolymer) or another polymer of high impact and tensile strength. 
     FIG. 1 shows the rear portion of the canula  101  mounted to its holder  100  by gluing. The flat and substantially rectangular top section of holder  100  has a sturdy and somewhat wider foot section integral with its underside which has a transverse flat impact face  102  facing in a distal direction. By having a width in excess of that of the rectangular top section a pair of upwardly facing slide ways of which only one,  103 , is shown are formed on the foot section. The rectangular top section is provided with laterally facing slide ways of which only one,  104  is shown. Slide ways  103  and  104  and their not illustrated counterparts form a pair of mirroring L-shaped guide ways cooperating with a pair of guide rails protruding from opposite sides of the inner wall of a housing (not shown). The front (distal) portion of the top section ends in a pair of slightly flexible arms  105 ,  106  encompassing a rectangular, wide through-opening into which the neck  112  of a T-formed displacement limiter  109  protrudes from the distally facing rim of the opening. At their free ends the arms  105  and  106  are widening inwardly to form teeth  107 ,  108  carrying on their upper faces inwardly-rounded stop pins  110 ,  111  the function of which will be explained below. 
     FIG. 2 shows the rear portion of the finger tube  201  disposed in a channel  218  of a holder  200  to which it is mounted by gluing. The rear (proximal) end of the finger tube does not protrude from the rear end of the holder  200 . The foot section includes a heel  202  and a rectangular base of the same width as the foot section of the canula holder  100 . On top of the rectangular base is disposed a substantially rectangular top section. At its rear end the top section includes two arms  205 ,  206  integral with the base, encompassing a rectangular opening the depth of which is delimited by the top face  220  of the rectangular holder base. The outer (lateral) faces of arms  205 ,  206  are provided with pairs of indentations  207 ,  208 ;  209 ,  210  for cooperation with teeth  107 ,  108  of canula holder  100 . At their rear free ends arms  205 ,  206  have inwardly extending hook portions  211 ,  212  leaving open a passage wide enough to fit around the neck  112  of the displacement limiter. The holder  200  is provided with two pairs of slide ways forming L-shaped guide ways similar to those of holder  100 . Of them only one pair,  203 ;  204  is shown. The left and the right guide ways of holders  100  and  200  are disposed in line. As is evident from FIG. 7 the top section of the holder  200  has a hollow portion distally off arms  205 ,  206 , the top wall of which is cut in the form of a tongue  213 . The tip  214  of tongue  213  projects above the upper surface of the top wall. The tongue  213  is somewhat flexible and can be depressed into the hollow space beneath it. 
     FIG. 3 shows the canula holder  100  and the finger tube holder  200  in an assembled state before and during the first step in which both travel together. Whereas the canula holder  100  is pushed forward (in a distal direction) by a strong steel coil (not shown; compressed to 70 N) affecting its rear (proximal) end, the finger tube holder  200  is pushed forward by the canula holder  100  with which it is in abutment at  120 ,  121 ,  122 . Canula holder teeth  107 ,  108  engage with the respective distal indentation  208 ,  210  of the finger tube holder  200  to avoid unintended forward movement of the finger tube  201 . 
     FIG. 4 shows the same arrangement, including cannula  101  and finger tube  201 , after the forward travel of canula holder  100  has come to an end while the finger tube holder  200  continues its movement by inertia, only to be stopped by the rear side of the transverse bar of the T-formed displacement limiter  109  abutting faces  215 ,  216  of hooks  211 ,  212 , respectively. For reasons of balance an additional stop is provided by a front face  221  of the distal heel portion cooperating with a rearward facing wall  415  of the stopper  400  (see below; see FIG. 7 which however illustrates the assembly before or during the joint displacement of the canula  101  and the finger tube  201 ). In this figure the canula  101 , the finger tube  201 , and the stylet  301  are shown except for their distal ends. Stylet holder  300  is fixed to the housing (not shown) and thus does not move. 
     FIG. 5 shows a fork-like stopper  400  for restricting the travel of the canula  101  and the finger tube  201 . By arms  402 ,  403  of the front-end fork shaft handle  401  protruding at opposite sides from the housing (not shown) the stopper  400  can be set at several positions along the canula/stylet axis to select one of a number of predetermined tissue penetration depths. The prongs  404 ,  405  of the fork are directed rearward to meet the impact (indicated by ‘F’ in the drawing) of the canula holder (by foot face  102 ) at their proximal ends. 
     The impact is damped by hemi-cylindrical recesses  409 ,  410 ,  411 ;  412 ,  413 ,  414  alternating at the inner and outer lateral faces of each prong. On impact the prongs  404 ,  405  are compressed in an axial direction and deformed by a sort of bending due to these recesses. ABS polymers are particularly well suited to the purpose of shock absorbers since they have a high softening point and excellent impact strength as well as a good yield tensile strength (toughness). Advantageously, they combine, by their chemical nature, the good yield tensile strength of general purpose (low impact) polystyrene with the high impact strength of rubbery polymers, such as butadiene rubber. The holders  100 ,  200 ,  300  and the stopper  400  are produced by injection molding. In combination with a serpentine geometry of the prong end portions, provision is made for good damping of the oscillatory movement of the canula  101  and the finger tube  201  with their holders  100 ,  200 . With the teaching of the invention in mind the person skilled in the art will be able to produce the damping effect also by modifications of the stopper design other than hemi-cylindrical recesses, for instance by a zigzag design, by bores, etc. 
     Proper damping (with respect to spring force, etc.) can be determined by experiments in which the depth and/or the number of recesses is varied. In the preferred embodiment according to the invention described above, a steel coil compressed to 70 N was used. The oscillation amplitude of the canula  101  with respect to the finger tube  201  was found experimentally to be in the range from 0.30 to 0.35 mm. In a device identical with that of the invention, except for the hemi-cylindrical recesses  409 ,  410 ,  411 ;  412 ,  413 ,  414  which had been omitted, a relative oscillation amplitude of from 1.0 to 1.1 mm was determined experimentally. In this case excessive finger bending or breakage was observed. By using steel coils compressed to a force of 30 N or less oscillation could be kept within acceptable limits. 
     Between the handle  401 , which is provided with stiffening ribs  407 , and the prongs  404 ,  405  the shaft has a flat transitional portion  406  which can be bent to allow the fork shaft handle  401  of the stopper  400  disposed in a latch arranged in the housing wall to be moved in distal/proximal direction between three positions, for instance to latch  503  (see FIG. 8) which position provides for maximal stroke length. The arms  402 ,  403  of the fork shaft handle  401  protrude through slits at opposite sides of the housing  500  (see FIG. 9) and are thus maneuverable from outside. A central groove  408  cooperates with corresponding channel  218  in the finger tube holder  200  and another one (not shown) in the canula holder  100  is provided for receiving the stylet/canula/finger tip tube assembly. 
     In FIG. 6 the stopper  400  is shown mounted with the stylet/canula/finger tube assembly of FIG. 4 at the end of the movement of the finger tube  201 . FIG. 7 is a corresponding longitudinal section. 
     The biopsy apparatus  500  of FIGS. 8-12 b  incorporates the biopsy instrument of FIGS. 1-7 in a housing  500  consisting of two substantially symmetrical halves sectioned perpendicular to the larger faces of the holders  100 ,  200  and of the catch  540 . Only one half is shown. The housing which has the approximate form of a rectangular bar can be of a suitable polymer, for instance polycarbonate, or of metal, such as aluminum. The housing halves fit by appropriate design of rims  501  and other elements, such as snaps (not shown). The halves can be connected by gluing, welding, or similar process. 
     The holder  300  of stylet  301  is firmly fixed at the housing and can only move with it. The stylet  301 , the canula  101  and the finger tube  201 , which are disposed substantially centrally in the housing  500  in a distal direction, protrude from the front wall after passage through an opening (at  502 ) of a diameter slightly greater than the outer diameter of the finger tube  201 . The walls of the housing  500  halves have inner profiles functioning as guide rails for holders  100  and  200  which can move forth and back in the housing to the extent permitted by other elements, such as the stopper  400  and the spring  610 . 
     The housing is provided with a loading assembly by which holders  100 ,  200  are brought to a ‘loaded’ position from which they can be released for tissue sampling. 
     To provide for easy loading by which the sturdy spring coil  610  has to be compressed the assembly makes use of three elements: a loading arm  520 , an intermediate arm  530 , and catch  540  holding the canula holder  100  during compression or in a compressed (loaded) position. With its hook-like front end  541  the catch  540  grips the tip  214  of the finger tube holder&#39;s  200  tongue  213 , as shown in FIG. 8 where the apparatus is in a loaded state. The canula holder  100  in turn is held in position by some of its front faces abutting rear faces of finger tube holder  200 , such as at  120  (FIG.  3 ). 
     The canula holder/finger tube holder assembly  100 ,  200  can be released from the loaded state by an oblong trigger  600  disposed between the catch  540  and canula holder/finger tube holder assembly  100 ,  200 . The rear end of trigger  600  forms a release button  602 , which passes through an opening in the rear wall of the housing  500 . By pressing the release button  602  the trigger  600  is pushed forward (direction A in FIG.  8 ), thereby dislocating downwards, by its slanting front end abutting the slanting rear face of tongue tip  214  (direction B in FIG.  8 ), thereby releasing the canula holder/finger tube holder assembly  100 ,  200 . The biopsy apparatus can be secured in a loaded position by a transversely displaceable locker pin  603  disposed near the rear end of the housing in through-bores of the housing. When inserted the locker pin  603  cooperates with an arc-formed cutout of the trigger  600 . 
     Prior to sampling, the cannula  101  is inserted into the tissue to a depth at which a sample is intended to be collected. Injection is made easy by the use of a canula of small diameter having a thin wall and a sharp cutting edge. 
     In the first sampling step the canula holder  100  and the finger tube holder  200  are dislocated together in a distal direction until the canula holder foot face  102  hits the rear end of the stopper  400  (at arrow heads F in FIG.  5 ). In the second sampling step the finger tube holder  200  with the finger tube  201  continues to travel by inertia until stopped by rear faces of the cannula holder (at  123 ; FIG. 4) and the stopper (at  415 ; FIG.  7 ). At the end of the second step (FIG. 10) the finger (not shown) of the finger tube  201  has entered the interior of the canula  101  through a wall opening, thereby cutting off a substantially cylindrical tissue sample disposed in the canula. On withdrawal of the biopsy apparatus the tissue sample remains in the canula and can be recovered. 
     By pushing the rear end  544  of the loading arm  520  away from the housing  500  the transverse bar  521  of the front end of the L-shaped loading arm  520  is made to swivel around a pivot  522  by which it is fixed at the housing. This releases the rear end of the loading arm  520  from a snap connection made up of a snap hook  535  of the upper transverse bar of an F-formed intermediate arm end portion engaging with a shoulder  524  of the loading arm  520  pertaining to the wall of an opening  523  therein. The vertical bar  532  of the F-shaped intermediate arm  530  portion is slidingly disposed in the housing  500 . The lower transverse bar  533  protrudes from the housing  500  through a wide slit extending over a substantial portion of the housing  500  in a distal direction from close its rear end. Near its other end the intermediate arm  530  is fastened to the loading arm  520  rotatably about a link  531 . A further joint  537  is provided in the intermediate arm  530  where its straight portion extending from the link  531  is joined to the lower transverse bar  533 . This joint  537  is obtained by the provision of a recess which makes the relatively thin (1-2 mm) portion of reduced thickness easy to bend; a flexible polymer, such as polyethylene or nylon, is an appropriate material for the intermediate arm  530 . 
     When loading arm  520  is pushed or pulled from the housing  500  the F-shaped intermediate arm portion travels in a distal direction and the catch  540  of which engages a recess  543  (FIG. 12 b ). The front end hook portion  541  of the catch eventually overrides the tongue tip  214  by forcing it to bend downwards through pressure applied against its slanting rear face. After engagement of the hook portion  541  with the tongue tip  214  further movement of the catch  540  in a distal direction is prevented by the stops  538  on the catch  540  abutting the inwardly rounded stop pins  110 ,  111  of the canula holder  100 . Just before reaching the stops  538  the stop pins  110 ,  111 , and with them the resiliently-flexible arms  105 ,  106  of the canula holder  100 , are pressed outward by shoulders  539  of lateral, outward facing guide walls (FIG. 12 a ) and remain in that position when abutting stops  538 . The catch  540  now has reached its extreme distal position. Further movement of the finger tube holder  200  with respect to the canula holder  100  is prevented by their abutment at  123  (FIG.  4 ). 
     Since the shoulders  539  slant slightly inwardly in a direction away from the stops  538 , the stop pins  110 ,  111  with the arms  105 ,  106  are pressed rearward. Thereby the teeth  107 ,  108  of the flexible arms  105 ,  106  disposed in the proximal indentations  208 ,  210  of finger tube holder arms  205 ,  206  become disengaged whereby the finger tube holder  200  is unlocked and carried forward until it is stopped by the canula holder  100  while the teeth  107 ,  108  snap into the distal indentations  207 ,  209 . In FIGS. 8-11 the lines indicating the position of stop pin  110 , the shoulder  539 , and the stop  538  are dotted. 
     By carefully moving, in the following step, the loading arm  520  towards the housing  500  the canula  101  and the finger tube  201  are retracted while the sample is expelled by the stylet  301 . The biopsy apparatus is now ready for re-loading to prepare it for removal of another sample of tissue. Arm  520  is pressed towards the housing  500  until the hook  535  of the intermediate arm enters the opening  523  of the loading arm  520  and engages the shoulder  524  to form a snap connection. At the same time the free end portion  534  of the intermediate arm  530  moves rearward and compresses the coil spring  610  via intermediate holders  100 ,  200  of the biopsy instrument. The flat trigger  600  is only active in triggering release and, therefore, has been omitted from the drawings except for FIG.  8 . 
     The construction of the loading assembly is also advantageous in that the loading arm  520  with the apparatus in a loaded position forms a single body with the housing  500  which is comfortable to hold and maneuver, and which is safe. It is also advantageous through its reduction of the force needed for compressing the spring coil. It is obvious to the person skilled in the art that the loading assembly also could be used with a strong tension spring which, for other reasons, however, is not as attractive in the present context as a compression spring. 
     The person skilled in the art will have no difficulty in modifying the invention by various combinations of its features, for example, without departing from its teaching. Accordingly, the present invention is to be limited not by the description of the preferred embodiments set forth above, but only by the appended claims.