The present invention relates to tissue sampling or biopsy devices, and in particular to an automatic tissue sampling apparatus for utilizing two piece biopsy needle systems. In a specific aspect, the invention concerns a needle hub assembly for use with the automatic tissue sampling apparatus.
A typical biopsy needle system may be utilized in obtaining tissue samples from a patient which includes two coaxial needles. The first needle generally consists of a substantially solid shaft in the form of a stylet having a cutting point at its end to facilitate insertion of the needle into the tissue to be sampled. The second needle is typically hollow in the form of a cannula and is disposed about the first inner needle.
In manual biopsy needle systems, the two needle components each have handles at their ends for manual operation. To obtain the tissue sample, the biopsy needle is inserted into the patient into the specific target tissue, preferably at the center of a desired cell mass to be investigated. The two needles are then reciprocated relative to each other to trap tissue within the outer needle cannula. Typically, the outer needle is held stable while projecting the first inner needle or stylet forward a short distance to penetrate the tissue. Then with the outer needle held stable, the inner stylet is retracted, severing the adjacent tissue and confining the tissue within the outer cannula. The entire biopsy needle assembly can then be withdrawn and the tissue sample sent for pathological examination.
In order to facilitate the tissue sampling operation, automatic tissue sampling or biopsy apparatus have been developed. One such device is depicted in U.S. Reissue Pat. No. 34,056 to Lindgren et al. This patent shows a tissue sampling device in which the two needles of the biopsy needle system are driven by a series of compressed springs. Each of the needles is supported by a hub, which hub is removably mounted within a respective slide or carriage. The actuating springs operate on the carriages to drive the stylet into the target tissue and then the outer cannula over the stylet to extract the tissue sample.
Another automatic tissue sampling device is shown in U.S. Pat. No. 5,284,156 to Shramm et al. This patent shows a biopsy apparatus that utilizes a different driving and actuation mechanism from that shown in the prior Lindgren patent. However, as with most automatic biopsy devices, the sampling apparatus in the Shramm patent also utilizes a carriage assembly to support hubs within which each of the needles are engaged.
The details of automatic tissue sampling or biopsy apparatus of this type can be easily gleaned from either the Lindgren or the Shramm patents. In accordance with the present invention, a tissue sampling apparatus 10, such as shown in FIGS. 1, 2, is provided which is similar in operation to the device shown in the Shramm U.S. Pat. No. 5,284,156. This biopsy device 10 includes a drive unit 11 which supports a biopsy needle assembly 12. As described above, the biopsy needle assembly 12 includes an outer cannula 13 and a concentrically disposed stylet 14. The stylet defines a tissue recess 15 which is used to capture and excise target tissue. The drive unit 11 includes a drive unit housing 17 that is provided with a hinged cover 18 to permit access to the internal workings of the drive unit 11. Many of the internal components of the drive unit are shown in FIG. 2. It is understood that the representation of tissue sampling device 10 in FIGS. 1, 2 is simply for purposes of illustration and that the device includes other components that are not depicted in the figures for clarity.
The particular tissue sampling device 10 shown in these figures can be a device sold as the MBD (Multiple Biopsy Device).TM. manufactured and marketed by Engineered Medical Systems, Inc., of Indianapolis, Ind. The details of the structure and operation of the MBD.TM. can be easily discerned from the product itself. However, for purposes of illustration in connection with the present invention, a general description of the components of the sampling device 10 will follow. In particular, the drive unit housing 17 is closed not only by the hinged cover 18 but also by a front end plate 19 and an opposite end plate 21. The front end plate 19 includes a slot 20 defined therein through which a biopsy needle assembly 12 extends. A support frame 22 is mounted within the drive unit housing 17 and includes a carriage stop 23 which restricts the longitudinal motion of the carriages within the unit.
The cannula and stylet of the biopsy needle assembly 12 are supported within the sampling device 10 by a cannula carriage 24 at the forward end of the device and a rear stylet carriage 25. The drive mechanism of the device includes a series of springs. A return spring 27 operates to provide a resistive force against reciprocation of the cannula carriage 24. A nest spring 28 and pusher spring 29 provide the actuation force to drive the two carriages 24, 25 forward into the tissue site. A center tube 30 extends through the cannula carriage 24 to maintain the coaxial alignment of the carriages and to support the shaft portion of the actuator handle 32. The actuator handle operates to cock the carriages 24, 25 into their operative positions. A latch 31 engages the carriages to hold them in their loaded or energized positions until the latch is released.
As thus illustrated, the tissue sampling device 10 is similar to automatic devices currently available in the marketplace. With these devices, the biopsy needle assembly 12 can be removed and sterilized and re-inserted into the same drive unit. Alternatively, a pre-sterilized disposable biopsy needle can be provided that fits into the carriages 24, 25 of the device. However, one difficulty with this approach is that the needle hubs affixed to the coaxial needles are often small and difficult to manipulate. In addition, the physician may have to spend time manipulating the hubs to properly position them within the carriages of whatever automatic biopsy device is being used. Finally, another difficulty encountered with these devices utilizing replaceable biopsy needle assemblies is that the assemblies are not easy to remove once a tissue sample has been obtained. Simple and safe removal is essential to protect the physician and to protect the excise tissue sample.
There is a need in the industry for a hub for use with a removable and replaceable biopsy needle assembly that is ergonomically efficient and is economical to produce. In addition, the hub should permit easy placement within the biopsy sampling device, and particularly in the carriages of the device.