WO1993020753A1

WO1993020753A1 - Biopsy needles

Info

Publication number: WO1993020753A1
Application number: PCT/US1992/003252
Authority: WO
Inventors: Hakan Jorulf
Original assignee: Biomni Medical Systems, Inc.
Priority date: 1992-04-21
Filing date: 1992-04-21
Publication date: 1993-10-28
Also published as: AU2315692A

Abstract

Core biopsy needles (10) for use in tissue biopsies comprise an elongate cannula (14) having a distal end that has a slanted point formed by a planar end edge (20) that slants backwardly toward the cannula (14). An elongate, inner stylet (12) is received for longitudinal sliding movement within the cannula (14). The distal end of the stylet (12) has a slanted point formed by a planar end (22) that slants backwardly toward the stylet. A sample receiving notch (30) is formed inwardly from one side of the stylet (12).

Description

BIOPSY NEEDLES

BACKGROUND OF THE INVENTION

1) Field of the Invention This invention relates to improvements in biopsy needles used in biopsy procedures.

2) Prior Art

The removal of minute tissue samples from humans and animals by introducing a needle into the body and catching the sample within the needle, is a frequently used medical practice today. Such samples are necessary for microscopic examination, organ cultures, etc.

The method most commonly followed for obtaining tissue samples has been to use a needle which is formed of an inner solid rod which has a sampling notch in the distal end thereof, in conjunction with a hollow outer cannula which slides thereover and cuts tissue which has been located in the sampling notch of the inner rod. The inner rod, except for its pointed distal end, is located within the cannula when the device is inserted into the tissue to be sampled. The outer cannula is then held stationary while the inner rod is inserted deeper into the tissue. While in this position, tissue moves into the sampling notch of the inner rod just adjacent the pointed distal tip thereof. The inner rod is then held stationary while the outer cannula is slid thereover. Motion of the outer cannula passing over the sampling notch causes the tissue located therein to be severed from surrounding tissue and thereafter to be trapped in the sampling notch as the cannula completely covers the inner rod distal end. Both the outer cannula and the inner rod with the tissue sample secured therein are then simultaneously removed from the patient. The outer cannula is then slid back away from the distal end of the inner rod to allow removal of the tissue sample from the sampling notch thereof. The tissue sample is then examined. This general method of tissue sampling has been used for several decades and is exemplified in U. S. Patent No. 3,477,423. As disclosed therein, the needle movements are made manually. This has certain disadvantages, in that movements may not be made fast enough to insure clean and complete severance of a tissue sample. Further, manual operation of the needle generally involves inaccurate movements, and slight lack of coordination between the needle and the cannula. This often causes unnecessary tissue damage and, in the case of infectious or tumorous tissue, can possibly cause spreading of the diseased tissue throughout a larger tissue area. Also, during manual operation of a needle, the patient ma move slightly during the introduction thereof into the tissue and cause the needle to miss its target area. Also, respiratory movements are common for some organs, for example the liver and the kidney, which further may reduce the accuracy of the sampling technique. An improvement in the above mentioned method of biopsy sampling has been to restrict needle movements by containing the inner rod and outer cannula inside a holder or automated biopsy gun. The biopsy gun restricts needle movement to specific directions and also carries springs and separate piston mechanisms therein which drive the rod and cannula through their sampling motions in a rapid and predictable manner. This^•technique is exemplified in U. S. Patent No. 4,699,154. Even though these automated biopsy guns are an improvement over manually actuated needles, the basic design of the needles themselves has remained the same.

Heretofore, it has been thought that the cannula of the biopsy needles must be relatively thick walled to provide strength and resistance to crushing and bending during insertion of the needles into the structure being biopsied. The minimal wall thickness of the cannula of prior art needles has ranged from 0.15 mm for a 21 gauge needle to 0.20 mm and more for a 14 gauge needle.

The forceful introduction of a needle into the tissue area generally causes a certain amount of damage to the tissue in the immediate surroundings of the target area. The relative wall thickness of the cannulas used in prior art needles forms a toroidal interface on the leading side edge of the stylet as the biopsy needle is injected into the tissue being biopsied. This toroidal interface in the case of prior art needles is of sufficient size that it causes damage of the outer (peripheral) part of the core sample. For example, it often causes damage of peripheral glomeruli in. cas of renal biopsy. Also, the toroidal interface of the prior art needles can damage surrounding tissue as the needle is being inserted through areas adjacent to the site of the biopsy as well as when the needle is inserted into the area of the tissue which is to be biopsied. In addition, the toroidal interface can cause transfer of normal tissue from adjacent areas of the site of the biopsy to the area in which the biopsy sample is being taken. This complicates the procedure inasmuch as the sample tissue taken may be partly or predominantly normal tissue that has been transferred to the biopsy site by the action of the toroidal interface formed by the distal end of the cannula.

In addition, the increased bulk size of the needle due to the relatively large wall thickness of the cannula increases the complications that can accrue during and after the biopsy procedure due to damage caused to the surrounding tissue during the procedure. It is well known that complications do occur in conjunction with prior art biopsy procedures. Surrounding sensitive structures can be damaged by the sharp insertion point of the stylet as well as by the toroidal interference surface formed by the distal end of the cannula. Such sensitive structure that can be damaged includes blood vessels, nerves, ducts or channels and sensitive membranes. Damage to blood vessels results in undesirable bleeding and loss of blood. Large blood collection can result in severe organ damage. Nerves can be damaged with loss of their function. Ducts and channels can be damaged with leakage of fluid into other body compartments. Sensitive membranes can be damaged leading to severe pain. Further complicating the matter with respect to the use of prior art biopsy needles, the pointed end of the stylet is relatively large and no attention has been made to develop new and advanced designs for this part of the needle. In the needles of the prior art, the tip of the stylet that extends beyond the distal end of the cannula has a length of between about 5 mm and 7 mm. This part of the stylet of course passes into the tissue and often bypasses the structure to be biopsied. This undue extension in many cases can cause undesirable damage to other tissue and organs that are otherwise normal and should not be damaged. Undesired damage can occur to normal, sensitive structures, and disease can be spread into such normal areas beyond the pathological target area. It also carries an additional risk of spreading diseased tissue material into normal tissues. 3} Objects of the Invention

It is an object of the present invention to provide improved biopsy needles for use in biopsy procedures and in particular with automated biopsy guns. A particular object of the present invention is to provide a biopsy needle of acceptable outer diameter that utilizes an ultra thin walled cannula which allows an increase in the relative amount of tissue to be retrieved in comparison to conventional biopsy needles in the prior art. Another objective of the present invention is to develop a new, rather inexpensive biopsy needle having an ultra thin walled cannula whose distal end is formed as a slanting, pointed end which unexpectedly acts as a razor type edge during severing of tissue and thus markedly improves the quality of the tissue sample that is obtained.

A further object of the present invention is to provide a new biopsy needle having an ultra thin walled cannula that causes less crushing or damage to the peripheral parts of the core tissue sample and in addition results in a significantly smaller outer diameter for the biopsy needle to thereby further reduce risks of complications developing during or following the biopsy procedure.

A still further object of the present invention is to provide a new biopsy needle having a novel combination of design features including an ultra thin walled cannula and specially designed, pointed distal end of the stylet which results in substantial reduction in complication rates from biopsy procedures as compared to such complication rates experienced with conventional prior art biopsy needles.

SUMMARY OF THE INVENTION Tissue biopsy from human organs and structures is used for a variety of purposes including diagnosis of disease following the course of treatment for a disease, and otherwise monitoring the response to various drugs or substances which will influence the health. Tissue retrieved can be analyzed in many different ways including for instance histology, cytology, electron microscopy, histochemistry and immunoanalysis. Such retrieval of tissue from the interior of the body is commonly performed by introducing a needle into the body structures thereby giving access to the particular structure to be biopsied. In the vast majority of cases, the needle has to pass through normal structures before reaching the target.

Tissue retrieval can be performed in various quantities. In general, smaller tissue samples will allow for cytological analysis, while histological study needs a larger sample for preparation and investigation. It is well known that complications can occur in conjunction with a biopsy procedure. Surrounding sensitive structures can be damaged by the needle. Damaging blood vessels can cause severe bleeding with loss of blood or damage of an organ due to large blood collection. Damaged nerves can result in loss of function. Damaged ducts or channels result in leakage of fluid into other body compartments. Damage to sensitive membranes can cause severe pain.

There is increased risk of bleeding within the pathological area inasmuch as pathological tissues often include neoplasm (tumor) which has increased blood supply. In addition, neovascularity (tumor vessels) often occurs which are weaker in their structure and can be damaged easier than normal vessels. In the surrounding area of the neoplasm there is often also increased number of blood vessels carrying the blood to the neoplasm. Furthermore, spread of disease can occur from the biopsy procedure when the needle passes through the diseased area into healthy, normal structures. Pathological structure can be spread forward as the needle is being inserted into the subject or backward when the needle is being retracted. In either case pieces of pathological tissue can be spread and left along the track of the needle.

The rate of complication varies according to what organ is being biopsied and is related to the size of the introcluded needle. The incidence of death in conjunction of biopsy varies but has been reported high as 0.3% in certain procedures. It has unexpectedly been found that a novel combination of improved features for biopsy needles can be provided that will significantly reduce complication rate. In general, the larger the outer diameter of the needle, and the longer the pointed end of the stylet extending from the cannula, the larger is the risk for complication to occur. The size (outer diameter) of biopsy needles is, of course, maintained as small as possible to minimize damage and complications. However, to retrieve tissue into the cannula of the needle, the cannula has to have a certain inner diameter to allow for sufficient material being collected and contained in the needle. In accordance with the present invention, it has been found that an ultra thin walled cannula can be employed in a biopsy needle. The ultra thin walled cannula allows a larger sample to be taken without increasing the outer diameter of the cannula.

In addition, it has been unexpectedly found that a relatively inexpensive fine grinding of the distal end of the ultra thin walled cannula produces a cutting edge that is essentially the same as a razor. The tissue sample is severed with an improved quality of the retrieved tissue by the razor like cutting edge of the ultra thin walled cannula. The surface or peripheral structures of the tissue sample is not crushed and damaged as unfortunately occurs when using conventional, prior art biopsy needles that use a relatively thick walled cannula. Previously, little or no attention has been paid to the needle design regarding the relationship between the inner and the outer diameter for biopsy needles. Producers of the prior art biopsy needles heretofore thought it necessary to use a relatively thick walled cannula in the biopsy needle for purposes of strength and rigidity. There has been no recognition of the significant, unexpected benefits that can be achieved by utilizing an ultra thin walled cannula in a biopsy needle, nor has it been recognized that such an ultra thin walled cannula could be utilized without loss of structural strength and rigidity.

It has now been found that a cannula having an ultra thin wall can be used in biopsy needles, and in fact such an ultra thin walled cannula results in significant additional unexpected improvements in the operation and performance of the biopsy needle. Further, when the ultra thin walled cannula is used in combination with improvements in the tip of the stylet of the biopsy needle, the occurrence of undesirable complications during and following the biopsy procedure can be significantly reduced.

Additional objects and features of the present invention will become apparent from the following detailed description taken together with the accompanying drawings. THE DRAWINGS

Preferred embodiments of the present invention representing the best mode presently contemplated of carrying out the invention are illustrated in the accompanying drawings in which: FIG. 1 is a longitudinal, central cross section through an improved biopsy needle in accordance with the present invention;

FIG. 2 is a pictorial end view of the cannula of the needle of Fig. 1 showing the sharpened, distal end of the cannula;

FIG. 3 is a pictorial end view of the stylet of the needle of Fig. 1 showing the sharpened, distal end of the stylet; and

FIG. 4 is a longitudinal, central cross section similar to that of Fig. 1 but showing a modified embodiment of the needle unit in accordance with the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS As shown in the drawings, the improved biopsy needle 10 of the present invention comprises an elongate solid stylet 12 and an elongate cannula 14 that slides in telescopic fashion over the stylet 12. In the embodiment illustrated in Figs. 1-3, a notch 16 is formed in the stylet 12 near the distal end of the stylet 12. In accordance with the invention, the cannula 14 has an outside diameter of between about 2.1 mm and 0.8 mm and corresponding wall thickness of between about 0.1 mm and 0.06 mm, respectively. The distal end of the cannula 14 has a slanted point formed by finely grinding the distal end to form an essentially planar, oval shaped edge 20 (Fig. 2) that lies on an essentially flat plane which slants backward toward the cannula at an angle of between about 25 degrees and 35 degrees with respect to the elongate axis of the cannula 14. Preferably, the slanted, pointed end 20 of the cannula 14 slants at an angle of between about 27 degrees and 31 degrees, and in a most preferred embodiment, the end 20 of the cannula 14 slants at an angle of about 29 degrees.

The elongate, inner stylet 12 is received for longitudinal sliding movement within the cannula 14. The stylet 12 has an outside diameter that is no more than about 0.1 mm less than the minimum inside dimension of the cannula 14. A slanted point is formed at the distal end of the stylet 12 by finely grinding the distal end of the stylet 12 to form an essentially planar, oval shaped edge 22 (Fig. 3) that lies on an essentially flat plane which slants backwardly toward the stylet 12 at an angle of between about 25 degrees and 35 degrees with respect to the elongate axis of the stylet 12. Preferably, the slanted, pointed end 22 of the stylet 12 slants at an angle of between about 27 degrees and 31 degrees, and in a most preferred embodiment, the end 22 of the stylet 12 slants at an angle of about 29 degrees.'

In the embodiment of the invention shown in Figs. 1- 3, an elongate sample receiving notch 30 is formed inwardly from one side of the stylet 12. The notch 30 is of any desirable length up[ to about 25 mm and has a depth of up to about 2/3 of the diameter of the stylet 12. Such notches 30 are well known and understood in the art of biopsy needles, and the dimensions of the notch 30 are given for illustrative purposes only. These dimensions are not per se critical and thus a broad range of dimensions has been recited.

In accordance with the embodiment of the .invention in which a notch 30 is provided in the stylet 12, the distal most point of the notch 30 is spaced in a longitudinal dimension along the stylet 12 from the innermost point of the oval sharpened edge 22 of the distal end of the stylet 12 by a distance of at least about 1 mm, preferably between about 1.25 mm and 1.75 mm, and most preferably between about 1.3 mm and 1.5 mm. By using an ultra thin walled cannula having the dimensions given above in place of the traditional, relatively thick walled cannula of prior art biopsy needles, larger core biopsy tissue samples can be obtained using needles that have an outer diameter no larger than the diameter of previous prior art biopsy needles. The biopsy needles of the present invention can in fact have a smaller outer diameter than previous prior art needles and still achieve a core diameter as large or larger than possible using prior art biopsy needles. It has been further unexpectedly found that by a simple procedure in which the distal end of the ultra thin walled cannula is finely ground to an essentially flat, planar, oval edge as specified above, the oval edge forms a razor like cutting edge. The razor like cutting edge cuts the tissue sample in a clean razor like cut without crushing or otherwise damaging the cut surface of the tissue sample. When using ultra thin walled cannulas having wall thicknesses as given above, only little honing of the oval edge of the distal end of the ultra thin walled cannula is necessary to produce a razor like cutting edge. The fine grinding of the distal end to form the oval, slanting edge is generally sufficient to produce a razor sharp edge. This edge can, if desired, be further honed to a very sharp, razor edge. It has been further found that the distal end of the ultra thin walled cannula forms a very thin edge that does not disrupt and harm tissue as the biopsy needle is being inserted into the tissue and as the biopsy sample is being taken. The very thin interference edge of the distal end of the ultra thin walled cannula is significantly less pervasive than the edge formed at the distal ends of the relatively thick walled cannulas used in prior art needles. The relatively thick interference edge of the thick walled cannulas of prior art biopsy needles crushes and damages tissue as the biopsy needle is inserted and pushed through the tissue. In addition, the interference edge of the relatively thick walled cannulas may transport portions of severed tissue along the outer surface of the needle as the needle is pushed through surrounding tissue. Normal tissue from a surrounding area can in fact be transported to the target area for the biopsy, and the normal tissue can be included in the tissue sample extracted during the biopsy procedure. It has been unexpectedly found that by using ultra thin walled cannulas as specified and claimed herein, little and if any only insignificant damage is done to surrounding tissue as the biopsy needle is pushed through the surrounding tissue.

It has further been found highly advantageous to limit the length of the stylet tip that projects from the cannula. By reducing the length of the projecting tip of the stylet, damage resulting to surrounding tissue can be significantly reduced, and transporting- of tissue forward with the tip of the stylet as the needle is being pushed through tissue can be essentially eliminated. In biopsy needles of the prior art, the solid tip of the stylet that extends from the distal end of the cannula as the needle is being inserted into and pushed through tissue is relatively long, e.g., 5 mm to 7 mm, and no special attention has been paid to improving the design of this part of the stylet. In the prior art needles, this solid tip is often long enough to by-pass through the structure being biopsied. The relatively large tip can cause unnecessary damage to surrounding, normal tissue and sensitive structures. The unnecessary extension of the solid tip of the stylet beyond the structure to be biopsied can spread disease from the structure that is being biopsied to normal tissue beyond the pathological target area.

By controlling the angle of the pointed end of the stylet 12 and further by limiting the distance that the notch 30 of the stylet 12 is spaced from the innermost point of the slanted, pointed end of the stylet 12, the length that the tip of the stylet 12 extends from the cannula 14 during insertion of the biopsy needle 10 is minimized. It has been found that the exposed tip of the biopsy needle of the present invention allows insertion of the needle through tissue as adequately as the longer tips of prior art needles. Further, the needles of the present invention have been surprisingly capable of causing much less damage to surrounding tissue than incurred with prior art biopsy needles.

A slightly modified embodiment of a biopsy needle in accordance with the present invention is shown in Fig. 4. In this modification, there is no notch formed in the side of the stylet 12. The stylet 12 is formed such that no more than about 1.5 mm of the stylet from the innermost point on the slanted end projects outwardly from the distal tip end of the cannula 14. Other criteria for the cannula 14 and stylet 12 are the same as discussed previously with respect to the embodiment shown in Figs. 1-3.

In using the biopsy needle 10 of Fig. 4, the needle 10 is inserted through surrounding tissue to the target area, with the tip end of the stylet 12 and the distal end of the cannula 14 being located within the target area. The cannula 14 is then slid forwardly and outwardly over the end of the stylet 12. As the open end of the cannula 14 moves through the tissue in the target area, sample tissue is cut and drawn into the hollow distal end of the cannula 14. The slight vacuum formed either by keeping the stylet at stand still or by the withdrawing of the stylet 12 within the cannula 14 aids in drawing severed tissue into the hollow distal end of the cannula 14. If so desired, external means (not shown in the drawings) can be provided to draw additional vacuum in the cannula 14 through a small channel (not shown in the drawings) formed in the stylet 12.

Although preferred embodiments of needles of the present invention have been illustrated and described, it is to be understood that the present disclosure is made by way of example and that various other embodiments are possible without departing from the subject matter coming within the scope of the following claims, which subject matter is regarded as the invention.

Claims

1. An improved biopsy needle for use in tissue biopsy, said needle comprising an elongate cannula having an outside diameter of between about 0.8 mm and 2.1 mm and a wall thickness of between about 0.06 mm and 0.1 mm, with the distal end of said cannula having a slanted point formed by finely grinding the distal end of said cannula to form an essentially planar, oval shaped edge which lies on an essentially flat plane that slants backward toward the cannula at an angle of between about 25 degrees and 35 degrees with respect to an elongate axis of said cannula; an elongate, inner stylet received for longitudinal sliding movement within said cannula, said inner stylet having an outside diameter that is no more than about 0.1 mm less than a minimum inside dimension of said cannula; a slanted point formed at the distal end of said stylet by finely grinding the distal end of said stylet to form an essentially planar, oval shaped edge which lies on an essentially flat plane that slants backwardly toward said stylet at an angle of between about 25 degrees and 35 degrees with respect to an elongate axis of said stylet; and a sample receiving, elongate notch formed inwardly from one side of said stylet, said notch being up to about 25 mm in length and having a depth of up to about 2/3 of the diameter of said stylet, with the distal most point of said notch being spaced in a longitudinal dimension along said stylet from the innermost point of said oval shaped edge of said slanted point of said stylet by a distance of between about 1 mm and about 2.5 mm.

2. A biopsy needle in accordance with Claim 1 wherein the planar, oval shaped edge forming the slanted point of said cannula slants at an angle of between about 27 degrees and 31 degrees; the planar, oval shaped edge forming the slanted point of said stylet slants at an angle of between about

27 degrees and 31 degrees; and the distance from the distal most point of said notch and the innermost point of said oval shaped edge of said slanted point of said stylet in a longitudinal dimension along said stylet is between about 1.25 mm and

1.75 mm. 3. A biopsy needle in accordance with Claim 1 wherein the planar, oval shaped edge forming the slanted point of said cannula slants at an angle of about 29 degrees; the planar, oval shaped edge forming the slanted point of said stylet slants at an angle of about 29 degrees; and the distance from the distal most point of said notch and the innermost point of said oval shaped edge of said slanted point of said stylet in a longitudinal dimension along said stylet is between about 1.

3 mm and

1.5 mm.

4. An improved biopsy needle for use in tissue biopsy, said needle comprising an elongate cannula having an outside diameter of between about 0.8 mm and 2.1 mm and a wall thickness of between about 0.06 mm and 0.1 mm, with the distal end of said cannula having a slanted point formed by finely grinding the distal end of said cannula to form an essentially planar, oval shaped edge which lies on an essentially flat plane that slants backward toward the cannula at an angle of between about 25 degrees and 35 degrees with respect to an elongate axis of said cannula; an elongate, inner stylet received for longitudinal sliding movement within said cannula, said inner stylet having an outside diameter that is no more than about 0.1 mm less than a minimum inside dimension of said cannula; and a slanted point formed at the distal end of said stylet by finely grinding the distal end of said stylet to form an essentially planar, oval shaped edge which lies on an essentially flat plane that slants backwardly toward said stylet at an angle of between about 25 degrees and 35 degrees with respect to an elongate axis of said stylet.

5. A biopsy needle in accordance with Claim 4 wherein the planar, oval shaped edge forming the slanted point of said cannula slants at an angle of between about 27 degrees and 31 degrees; and the planar, oval shaped edge forming the slanted point of said stylet slants at an angle of between about 27 degrees and 31 degrees.

6. A biopsy needle in accordance with Claim 4 wherein the planar, oval shaped edge forming the slanted point of said cannula slants at an angle of about 29 degrees; and the planar, oval shaped edge forming the slanted point of said stylet slants at an angle of about 29 degrees.