Biopsy instrument with radius ground cutting edge

BIOPSY INSTRUMENT WITH RADIUS GROUND CUTTING EDGE

0002CROSS-REFERENCE TO RELATED APPLICATION The present application is a continuation-

000310 in-part of U.S. Patent Application entitled "AUTOMATIC BIOPSY INSTRUMENT WITH INDEPENDENTLY ACTUATED STYLET AND CANNULA", filed on April 24, 1991, and given U.S. Patent Application Serial No. 07/690,628, which itself is a continuation-in-part of U.S. Patent Application

000415 entitled "AUTOMATIC BIOPSY INSTRUMENT", filed on

0005November 7, 1990, and given U.S. Patent Application Serial No. 07/610,006.

0006FIELD OF THE INVENTION 20 This invention relates to an automated mechanism for collecting a tissue sample from humans or animals by a procedure referred to as tissue biopsy, and more particularly to an instrument for automatically performing the tissue extraction from a 25 tissue mass in a precise and rapid manner with minimum patient discomfort.

0007BACKGROUND OF THE INVENTION It is often desirable and frequently 30 absolutely necessary to sample or test .a portion of tissue from humans and even animals to aid in the diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions and other diseases or disorders. Tumors are first noted in a patient by one 35 of three ways. These ways include palpation, X-ray

0008Λ imaging or ultrasound imaging. Typically, in the case '* of cancer or the suspicion of malignant tumors, a very important process called tissue biopsy is performed to establish whether cells are cancerous. Biopsy may be done by an open or closed technique. Open biopsy removes the entire tissue mass or a part of the tissue mass. Closed biopsy on the other hand is usually performed with a needle-like instrument and may be either an aspiration biopsy (hollow needle on a syringe) or a cored biopsy (special tissue cutting needle design) . In needle aspiration biopsy, individual cells or clusters of cells are obtained for cytologiσ examination. In core biopsy, a segment of tissue is obtained for histologic examination, which may be done as a frozen section or paraffin section.

0009The methods and procedures of obtaining tissue samples for cytologiσ or histologic examination have been performed historically by manual insertion and manipulation of the needle. These procedures are performed blind by the physician and guided by feel and known, anatomic landmarks.

0010One prior art manual biopsy device includes a syringe arrangement including a stylet surrounded by a cannula. The stylet has a pointed tip and behind the tip a reduced diameter shank. The diameter of the pointed tip is slightly less than the internal diameter of the cannula such that the tip prevents tissue from entering the cannula as the cannula is passed through surrounding tissue to the point of intended biopsy. An O-ring is placed in sealing relationship between the reduced diameter shank and the internal diameter of the cannula. During operation of the biopsy syringe, the cannula is urged forward past the tip of the stylet in order to collect a tissue sample. As this occurs, a vacuum is formed in the cannula between the O-ring and the tissue sample. This vacuum tends to draw the tissue sample into the cannula.

0011This device, however, has disadvantages in that it is manual and thus does not give totally reliable results, as discussed below, in taking a biopsy of a very small tumor.

0012Examples of tissue harvesting devices have been described in United States Patent Nos. 4,651,752; 4,702,260; and 4,243,048. Two very important innovations in medical technology have influenced the field of tissue biopsy in the last five years. One is the use of tissue imaging devices which allow the physician to see inside the body and visually guide the needle to the tumor mass. The second is the invention of the

0013Automatic Core Biopsy Device (ACBD) . The ACBD is an instrument which propels a needle set with considerable force and speed in order to pierce the tumor mass and collect the tissue sample. This ACBD has allowed physicians to test tissue masses in the early stages of growth and has contributed to the medical trend of early diagnosis and successful treatment of cancer.

0014The Automated Core Biopsy Device allows a biopsy to be performed on tumor masses as small as two millimeters in diameter. This procedure is performed under ultrasound or X-ray guidance. Tumors of this size cannot be biopsied reliably by hand since the tumor is about the same size as the biopsy needle. Manual attempts at biopsy pushes the tumor away without piercing the mass. Automatic puncture devices accelerate the needle at such a velocity that even a small tumor can be pierced. Automated Core Biopsy Devices (ACBD) use the True Cut needle set design. The True Cut needle is comprised of an inner notched stylet 17 (Fig. 5a) with an outer cannula 16 (Fig. 5a) . The stylet is advanced into the tissue under spring power followed by the cannula which cuts and traps the tissue sample 18 (Figs. 5a , 6) in the notch of the stylet. The True Cut needle yields a core tissue sample 18 which is semi-circular in cross-section with a length determined by the stroke of the ACBD.

0015The stylet is a needle with a notched cut¬ out at the distal end. The cannula is a hollow needle with an angled cutting surface at the distal end which slides over the stylet. When the stylet is pushed into the tissue, the tissue is pierced and relaxes into the notched cut-out. When the cannula is slid forward, the tissue in the notch of the stylet is sliced off and retained in the notch until the cannula is drawn back. The most common True Cut needle size used by

0016ACBD's is 18 gage. The use of 18 gage needles is a compromise between the physician's desire to use the smallest, least invasive, needle gage and the pathologist's needs for as large a tissue sample as possible to minimize false-positive diagnosis . This compromise in needle size leads the physician to obtain multiple core samples from the biopsy site to allow the pathologist sufficient tissue for an accurate diagnosis. • The requirements of the physician and the pathologist dictate the need for an alternative approach in the function and design of the conventional ACBD and needle sets. The ideal product would allow the use of smaller needle gages and/or lessen the need for multiple samples to be taken from a given biopsy site.

0017SUMMARY OF THE INVENTION Based on the prior art instruments for biopsy sampling of tissue masses and the actual present state of this art, there exists a need for an instrument which is capable of obtaining biopsy samples which yield more tissue volume for a given needle gage than currently marketed devices. This increased tissue volume allows the physician to use smaller needle gages and/or reduce the number of punctures per biopsy site.

0018The ability to use smaller needle gages and/or less punctures per biopsy site, opens up the other major areas of biopsy procedures to the use of a device which will increase the reliability and safety of these procedures.

0019Accordingly, I have invented an instrument for removing cylindrically shaped tissue samples of pre-determined size from a tissue mass with an instrument that automatically penetrates, captures and removes the tissue sample for examination.

0020The instrument is a spring powered mechanical design. The needle set is integral with the housing and consists of a outer hollow cannula- and an inner pointed tipped stylet. The stylet and the cannula are driven forward under spring force in a defined motion in relation to each other. In a preferred form, the housing is comprised of a hollow tube which guides a spring backed piston to which the cannula and stylet are attached. The piston is pushed backwards in a chamber described by this housing by means of an outer actuator which compresses the main spring. A locking means holds the piston and main spring in the compressed state in which the inner stylet is positioned inside the cannula and protrudes out of the distal end of said cannula. Once the spring is released, the piston and cannula are driven forward. As the piston and cannula advance, the stylet is pushed in the opposite direction by a secondary spring on the far side of the piston until a stop is reached, at which point the stylet stops the backward motion and tracks the forward motion of the advancing cannula for the rest of the movement of the cannula.

0021At the end of the forward motion of the cannula, the piston comes to rest against a block which incorporates an "O" ring seal. The chamber in which the piston moves is sealed at the distal end of the device by an end cap with integral seal and at the proximal end by a block with the integral seal. At the end of the forward motion of the piston, the chamber is sealed by the spring loaded position of the piston against said block, allowing only the hollow bore of the cannula as an exit.

0022As the spring is released, tissue is penetrated by the forward motion of the cannula, the tissue advances up into the hollow bore of the cannula created by the backward motion of the stylet. The cannula advances a defined distance into the tissue, at which point the inner stylet stops the backward motion and begins to follow the cannula, stopping the relative motion of the stylet with respect to the cannula. Since the cannula continues the forward motion and the hollow bore is filled with pierced tissue backed up against the stylet, the further advancement of the cannula slices off the captured tissue trapped inside of the cannula from the surrounding tissue at the distal end of the cannula. Essentially, the present design ensures that no matter if a soft or a firm tissue sample is being taken, the inventive device reliably slices off the tissue sample so that the tissue sample is not left in the patient when the cannula is removed.

0023The inventative instrument includes a radius ground cutting edge provided on the end of the cannula. This radius ground cutting edge defines a V- shaped portion which greatly enhances tissue severability with respect to prior art cutting edges which essentially have an oval aperture.

0024With the tissue sliced off at the tip of the distal end of the cannula and the piston sealed against the inner "0" ring seal of the block, the captured tissue remains positioned in the hollow bore of the cannula as the needle is withdrawn from the surrounding tissue. The captured tissue acts as the final seal of the chamber created by the housing and the associated internal parts ensuring that the tissue sample is held in the cannula as the cannula is withdrawn from the patient.

0025The stylet is a pointed needle positioned inside the cannula. At the distal end of the stylet, a pointed tip facilitates the introduction of the needles into the tissue mass. The stylet is positioned flush to the end of the cannula in the cocked positioned. In the cocked position, the stylet prevents tissue from entering the cannula as the needle set is introduced into the body. As the device is fired, the cannula advances while the stylet moves in the opposite direction, thus allowing space for the penetrated tissue to enter the cannula. As the device is cocked and the piston and cannula are retracted, the cannula is moved backwards over the stylet, pushing the tissue sample out of the cannula. This action removes the tissue sample and cocks the device in one motion.

0026A volumetric analysis of a cross-section of tissue area collected with the True Cut needle set vs. the cylindrical core samples of this invention follows:

0027Stylet Gage x-fip.πt-ftirraa Percentage

0028Trueut 18ga. .OOOs'q/in.

0029Cylindrical 18ga. .OOl≤q/in. 72%largsa:mple Cylindrical 20ga. .OOOSq/in. 71%ofTrueutl8ga.

0030For a given needle gage and core length, the cylindrical core volume of this invention is 72% larger than that provided by the True Cut needle set. A 20 gage cylindrical needle in accordance with this invention will yield 71% of the tissue yielded by an 18 gage True Cut needle set.

0031Accordingly, it is a principle object of this invention to provide an automated tissue sampling device for obtaining tissue samples which have a circular cross-section. Such a cross-section provides for more tissue mass for a given needle gage, provides for a less invasive procedure with reduced tissue trauma and allows for the maximum tissue to be harvested with the minimum number of samples taken.

0032It is a further object of this invention to provide a biopsy instrument which accelerates a needle at such a velocity so as to allow penetration of small tissue masses that would otherwise be too small for a closed biopsy procedure. It is another object of this invention to provide an instrument which may be used to obtain multiple tissue samples from the same biopsy site without disassembling the device or actuating multiple mechanisms or controls.

0033It is yet another object of the invention to provide an automated biopsy device which creates a seal in an inner chamber substantial enough to effectively assist in holding the tissue in the cannula as the cannula is withdrawn.

0034It is yet another object of the present invention to provide a cannula having a radius ground cutting edge in order to assist in the severing of the tissue biopsy. These and other objects of the invention will be apparent from the following descriptions and claims.

0035BRIEF DESCRIPTION OF THE DRAWINGS The above noted advantages and other characteristic features of the present invention will be apparent from the accompanying drawings, and pointed out in the following detailed description of the preferred embodiment of the invention in which references will be made to the accompanying drawings wherein like reference numerals designate corresponding parts and wherein:

0036Figs, la, lb and lc are cross-sectional side elevation views of the biopsy instrument of the invention. Fig. la depicts the device in the "fired" position, Fig. lb depicts the device in the process of being "cocked" with the thumb knob pushed rearwardly and Fig. lc depicts the device in the "cocked" position; Fig. 2 is a partial side elevation of the needle at its distal end;

0037Figs. 3a, 3b, 3c and 3d are pictorial illustrations of needle positions in various stages of the operation of an embodiment of the invention;

0038Fig. 4a is a pictorial illustration of the preferred embodiment of the distal needle end of the invention;

0039Fig. 4b is a pictorial illustration of the cross-section of tissue obtained from the preferred embodiment of this invention;

0040Fig. 5a is a pictorial illustration of the distal needle end of the prior art;

0041Fig. 5b is a pictorial illustration of the cross-section of tissue obtained from the prior art.

0042Figs. 6a and 6b depict side and plan views of the distal end of a prior art cannula showing a conventional straight ground cutting edge.

0043Figs. 7a and 7b depict side and plan views of an embodiment of the present invention wherein the distal end of the cannula is provided with an aperture defined by a radius ground cutting edge.

0044Fig. 8 depicts a side view of the stylet projecting through the inventative cannula aperture with the radius ground cutting edge of Fig. 7a.

0045DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes of promoting an understanding of the principles of the invention, -reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

0046Considering now the drawings in detail, Fig. la illustrates a side elevation view of the embodiment of the inventive biopsy instrument which is shown to depict the main components of said embodiment with the main body or housing is shown generally at 1 and the tissue piercing and removal means shown by stylet 11 and cannula 13. The main housing means extends from end cap 7 to the distal end of thumb knob 4. Within said housing 1 is a plunger block 2. Plunger rod 3 is depressed by exerting pressure on thumb knob 4 which compresses the main spring 5. Plunger 2 and main spring 5 are held in the compressed state by latch pin 12 which resides in actuator button 8. Spring 9 pushes actuator button 8 and latch pin 12 up against plunger rod 3. As plunger rod 3 is depressed, latch pin 12 slides along plunger rod 3 until latch pin 12 detents into the annular groove in plunger rod 3 (Fig. lb) . Latch pin 12 holds plunger rod 3 in place and thus holds plunger 2 and main spring 5 in compression until such time that actuator button 8 is depressed. Once the biopsy instrument is cocked, .the spring 14 returns thumb knob 4 to an initial position against stop 23 of the main body 1 (Fig. lc).

0047When the actuator button 8 is depressed, plunger rod 3 is released and main spring 5 pushes plunger 2 forward with the associated component cannula 13 which is attached to plunger 2. Cannula 13 is fixed to plunger 2 through a hole in plunger 2 is sealed in the hole and communicates with an inner chamber 21 defined by the inside of housing 1. Plunger 2 when in contact with "O" ring seal 10, and end cap 7 with associated "O" ring seal 6, create an air tight inner chamber 21 of main housing 1 with the hollow body of cannula 13 the only avenue of air passage. Depressing actuator button 8 releases plunger rod 3 thus allowing plunger 2 to be forced forward by main spring 5. As plunger 2 moves forward, spring 16 pushes rearwardly against stylet plunger block 15 which pulls the attached stylet 11 back out of cannula 13.

0048Cannula 13 continues forward motion as stylet 11 moves back. The associated relationship of motion between cannula 13 and stylet 11 is maintained until the stop collar 20 of plunger 22 contacts the plunger block 2. At this point, the cannula 13 is still moving forward, but stylet 11 stops moving backwards and begins to move forward with cannula 13. Both cannula 13 and stylet 11 move forward through the surrounding tissue, cutting off the captured tissue in cannula 13, until the plunger block 2 comes to rest against "O" ring 10, sealing the chamber 21 of the main housing 1. The captured tissue in cannula 13 acts as a seal to the chamber 21 created in the main housing 1 and allows the withdrawal of the needles from the surrounding tissue without accidental loss of the captured tissue.

0049The design of prior art cannulas as evidenced by Figs. 6a and 6b include a straight ground cutting ^• edge 30 which is provided at an angle with respect to the tubular body 32 of the cannula 34. This straight ground cutting edge includes a bevel 36 and defines an oval aperture 38. The oval aperture 38 includes a forwardmost portion 40 and a rearwardmost portion 42. The tissue is severed or cut-off by the rearwardmost portion 42 with the stylet and cannula travelling forwardly together.

0050Figures 7a and 7b depict an improved cannula 50 which has a cutting edge 52 with a straight ground cutting edge portion 54 and a radius ground cutting edge portion 56. The straight ground cutting edge portion 54 in combination with the radius ground cutting edge 56 defines a modified oval aperture 58 which has a forwardmost portion 60 and a rearwardmost portion 62. As can be seen in Fig. 7b, with the creation of the radius ground cutting edge portion 56 the rearwardmost portion 62 of the modified oval aperture 58 is substantially V-shaped and includes first and second substantially straight cutting edges 64 and 66 which end abruptly in a point 68. A bevel 70 is provided on the cutting edge 52. As can be seen in Fig. 7a, the radius ground cutting edge portion 56 extends below a reference line 70 extending from the straight ground cutting edge portion 54. It can be appreciated that due to the tubular shape of the cannula 50 that as the radius ground cutting edge portion 56 is machined by grinding the cannula 52 about a radius, such as radius 72, that the V-shaped portion is formed with the two straight cutting edges 64, 66.

0051In operation with the stylet and cannula proceeding forwardly together and with an appropriate sample of tissue collected in the cannula, the radius ground cutting edge portion 56 serves to sever the biopsy sample from the surrounding tissues in a highly efficient manner ensuring that the biopsy sample is not left with the mass of surrounding tissue but is extracted with the removal of the biopsy instrument. Figure 8 depicts the stylet 11 projecting through the cannula 50 of the invention preparatory to the biopsy instrument being insert into the mass of tissue from which a tissue biopsy is to be obtained. Figure 2 illustrates a cross-sectional side elevation view of the distal ends of cannula 13 and stylet 11. Stylet 11 is a solid rod with a pointed tip at the distal end. Stylet 11 prevents tissue from entering cannula 13 as it is passed through the surrounding tissue to the point of intended biopsy.

0052Figures 3a through 3d illustrate the preferred embodiment of the distal needle end of this invention. Four stages of motion are depicted.

0053Figure 3a shows the preferred embodiment of cannula 13 and stylet 11 in the "cocked" position.

0054Figure 3b shows the preferred embodiment of cannula 13 and stylet 11 in the act of being "fired".

0055Figure 3c shows the continuation of motion of cannula 13 with the reversal of motion of the stylet 11.

0056Figure 3d shows the preferred embodiment of cannula 13 and stylet 11 in the act of "cocking" the mechanism and the subsequent expulsion of the tissue sample 15. Figure 4a illustrates the preferred embodiment of the distal needle end with the expulsed tissue sample 15.

0057Figure 4b illustrates the cross-section of tissue 15 obtained from the distal needle end of the • preferred embodiment of this invention.

0058Figure 5a illustrates the dis±al needle end of the prior art device with the expulsed tissue sample 18. Figure 5b illustrates the cross-section of tissue 18 obtained from the distal needle end of the prior art device.

0059While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.