Method and apparatus for obtaining stereotactic mammographic guided needle breast biopsies

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to stereotactic mammographic guided needle breast biopsies, and more particularly to an add-on stereotactic needle breast biopsy apparatus for converting a conventional mammography apparatus into a mammography apparatus capable of taking high quality stereotactic mammographic images of a breast and performing stereotactically guided needle breast biopsies on lesions identified in the stereotactic images.

2. Description of the Prior Art

Within the last couple of decades there have been many improvements made in the field of mammography and stereotactic mammographic guided needle breast biopsies. These improvements have allowed the field to move towards faster, more accurate and less invasive procedural techniques to determine whether a suspicious lesion spotted in a mammographic image is malignant. More particularly, the field of mammography, as with many other medical imaging procedures, is shifting from traditional screen-film based imaging, where mammographic images are captured on a film negative, to digital imaging, where such images are acquired on a Charge Coupled Device (CCD) array and displayed on a cathode ray tube (CRT). While the advantages of the latter method for imaging are numerous, one of the most readily notable advantages is the significant reduction in image acquisition time. For example, an image captured on a CCD array may be displayed on a CRT in as little as three to six seconds after the mammographic imaging procedure is completed. In contrast, it can take more than 5 to 10 minutes to obtain the same image captured on a film negative due to processing time requirements involved in developing the mammogram film negative. The reduction in image acquisition time has been a real benefit to patients undergoing a stereotactically guided needle breast biopsy. An example of a digital imaging camera system employing a CCD array which is suitable for use in mammography may be found in the applicants' U.S. Pat. No. 5,216,250, which is incorporated herein by reference in its entirety.

Stereotactic mammographic guided needle breast biopsy procedures are evolving towards sampling cells of suspicious lesions through less invasive fine needle aspiration (FNA) procedures and sampling tissue of suspicious lesions through needle core biopsies, and away from using more invasive procedures, such as wire guided surgical excision of the suspicious lesion. Generally, there are two types of stereotactic mammographic guided needle breast biopsy devices, add-on and dedicated, described in the art for performing the range of stereotactically mammographic guided needle breast biopsies described above.

A prior art add-on biopsy device allowing stereotactic mammographic breast biopsy procedures to be carded out using a conventional mammography apparatus is disclosed in U.S. Pat. No. 4,727,565. The add-on biopsy device described therein comprises a needle guiding stage, a compression paddle and an image receiver. When a stereotactic guided needle biopsy is desired, the biopsy device is attached to a conventional mammography device. The patient's breast is held in a compressed state between the compression paddle and image receiver. To acquire the stereotactic images, the device employs oblique angle stereotactic imaging geometry wherein the X-ray tube of the mammography apparatus is positioned at oblique angles relative to the plane defined by the image receiver. Once the stereotactic images are obtained, the two dimensional positional coordinates of the suspicion lesion appearing in each of the images is measured and these two dimensional positional coordinates are used to calculate the three dimensional coordinates of the suspicious lesion in the breast relative to the needle guiding stage. Unfortunately, the oblique angle stereotactic imaging geometry employed by this device to acquire stereotactic images has some drawbacks which can possibly compromise the image quality of the stereotactic images. The imaging geometry drawbacks will be more fully explained below.

A prior art dedicated biopsy device for carrying out stereotactic mammographic breast biopsy procedures is described in "Stereotaxic Instruments for Needle Biopsy of the Mamma", an article authored by Jan Bolmgren et al, published in the American Journal of Roentgenology, Vol. 129, page 121, in July 1977. In the dedicated biopsy device, the patient is positioned on a table in a prone position over the imaging and biopsy apparatus. The breast is pendulantly presented through an aperture at one end of the table. The obvious advantage of the dedicated biopsy device over the add-on biopsy device is that it is far more comfortable for the patient. However, the dedicated biopsy device tends to be relatively more expensive and tends to take up more floor space, which, in some situations, can also be expensive. Typically, the dedicated device is only used for stereotactic mammographic breast biopsy procedures so it may have somewhat less overall utility than a conventional mammography device equipped with an add-on stereotactic biopsy apparatus. A commercial version of this device, known as a TRC Mammotest was manufactured by Tekniska Roontgencentralen AB of Sweden. A description of the commercial TRC Mammotest may be found in U.S. Pat. No. 5,078,142. The two dedicated devices identified herein also suffer from the same oblique angle stereotactic imaging geometry drawbacks as mentioned above for the prior art add-on device.

While there is little doubt that oblique angle stereotactic imaging geometry, briefly described in the '565 patent, is sufficient for calculating the three dimensional coordinates of an observed lesion in a pair of images, it is believed that this stereotactic imaging geometry is not the best for obtaining stereotactic images with optimum image quality, quality approaching that of conventional screening mammography. More particularly, because these devices position the X-ray tube at an oblique angle relative to the plane of the image receiver for each of the stereotactic images, it is nearly impossible to use a conventional moving scatter reducing grid in a conventional manner because the central ray of the X-ray beam does not fall normal to the plane of the image receiver.

Conventional scatter reducing grids generally comprise a plurality of nearly parallel slats of X-ray absorbing materials that are typically positioned to be focused at the focal spot of the X-ray tube. These grids are also moved in a direction tangential to the patient's chest wall during the X-ray exposure to blur the shadows cast on the film by the plurality of X-ray absorbing materials. Because the central ray of the X-ray beam of the above described prior art devices is not presented normal or perpendicular to the plane of the X-ray film in either of the stereotactic imaging positions, it is nearly impossible to use a moving scatter reducing grid in the conventional manner because the oblique angle stereotactic X-ray imaging positions take the focal point of the X-rays outside of the focus of the grid. While it is possible that one skilled in the art could orient a conventional grid such that it could be used during stereotactic imaging with these prior art devices to somewhat overcome the above described constraints, these prior art biopsy devices have a further drawback in that they cannot use scatter reducing grids having X-ray absorbing materials arranged in a crossed structure because there is no way to orient the grid in the image plane such that this type of grid will be in focus with the focal spot of the X-ray tube during stereotactic imaging.

Thus, it is possible that a suspicious lesion spotted in a mammogram obtained by standard screening mammography techniques using a conventional scatter reducing grid may not be observable in stereotactic images taken with these prior art devices because they are generally unable to effectively use the scatter reducing grids. A brief discussion of the benefits of scatter reducing grids may be found in the Recommended Specifications for New Mammography Equipment published by the American College of Radiology.

The above noted limitations of the oblique angle imaging geometry of the prior art add-on and dedicated devices have been overcome by the stereotactic mammography imaging system described in related grandparent U.S. Pat. No. 5,289,520, which is incorporated herein by reference in its entirety. The device disclosed therein is a dedicated stereotactic mammography biopsy system. It overcomes the oblique angle imaging limitations by obtaining stereotactic images of the breast with perpendicular stereotactic imaging geometry wherein the focal spot of the X-ray tube is always presented normal to the plane of the X-ray film in each of the stereotactic imaging positions. Unlike the oblique angle stereotactic imaging geometry of the prior art devices, the perpendicular stereotactic imaging geometry does not place the same constraints on the use of scatter reducing grids since the X-ray focal spot remains in the same position relative to the image receiver during all stereotactic imaging. Thus, a conventional scatter reducing grid will always be in focus with the focal spot of the X-ray tube during all stereotactic imaging. However, while this device is more comfortable for the patient, as explained above, dedicated biopsy devices may have somewhat less overall utility for the user and can be more expensive than a typical mammography-apparatus equipped with an add-on type stereotactic needle biopsy device.

For at least several years, some mammography apparatus have been equipped with digital image receivers having a CCD camera focused through an optical arrangement of mirrors and lens or optical fibers at a phosphor screen. As compared to film-screen image receivers, digital image receivers tend to have a small field of view due to the costs of CCD arrays. When a mammography apparatus equipped with a digital image receiver having the small field of view is used to acquire stereotactic images and perform needle biopsies, conditions can arise such that the resulting stereotactic X-ray images do not completely fall within the field of view of the CCD camera. Accordingly, it is possible that a lesion in some of the stereotactic X-ray images can fall outside of the field of view in one or even both stereotactic images.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of the prior art by providing a biopsy apparatus for performing stereotactic mammographic needle biopsies on a breast with a conventional mammography apparatus that can obtain images with either a digital image receiver or a conventional film-screen image receiver. The mammography apparatus that may be used with the biopsy apparatus generally includes a base, a pivot shaft connected to the base at a first end, and a second end, the pivot shaft further defining a pivot axis, an imaging arm having an X-ray source end and an X-ray receiving end, the imaging arm being attached to the second end of the pivot shaft at a point between the X-ray source end and the X-ray receiving end, an X-ray tube having a focal spot, the X-ray tube being connected to the imaging arm at its X-ray source end, an X-ray image receiver support affixed to the imaging arm at its X-ray receiving end, and an X-ray image receiver attached to the support.

The biopsy apparatus for performing stereotactic mammographic needle biopsies with the conventional mammography apparatus described above includes a biopsy apparatus base which has first and second sides and a compression plate engaging end. A compression plate is attached to the biopsy apparatus base at the compression plate engaging end. A multi-dimensional positionable biopsy needle guiding stage is attached to the first side of the biopsy apparatus base and a biopsy needle holder is connected to the needle guiding stage. The biopsy apparatus also includes a compression paddle carriage slidably attached to the biopsy apparatus base on its first side between the biopsy needle guiding stage and the compression plate and a compression paddle, having an opening therein permitting a biopsy needle to be inserted into a breast, is affixed to the compression paddle carriage. A breast is held in position between the compression paddle and compression plate during imaging and the biopsy procedure. The biopsy apparatus further includes a pivot member having first and second ends. The first end of the pivot member is pivotally attached to the second side of the biopsy apparatus base near its compression plate engaging end and the pivotally attached pivot member allows pivotal motion of the biopsy apparatus base relative to the imaging arm of a conventional mammography apparatus having an imaging arm which pivots about a pivot axis defined by a pivot shaft of the mammography apparatus. The pivot member of the biopsy apparatus also includes a means for attaching the biopsy apparatus to the imaging arm, the means being affixed to the pivot member at its second end.

Accordingly, it is one object of the present invention to provide an add-on stereotactic needle biopsy apparatus to convert a conventional mammography apparatus into a device for carrying out stereotactic mammographic guided needle breast biopsies.

It is another object of the present invention to provide an add-on stereotactic needle biopsy apparatus for a conventional mammography apparatus that can use scatter reducing grids in the conventional manner to improve the image quality of stereotactic images.

It is another object of the present invention to provide an add-on stereotactic needle biopsy apparatus for a conventional mammography apparatus equipped with a digital image receiver.

These objects are accomplished, at least in part, by providing an add-on stereotactic biopsy apparatus that obtains stereotactic images using perpendicular stereotactic imaging geometry.

These objects are also accomplished, at least in part, by shifting the position of a digital image receiver during stereotactic imaging in proportion to the thickness of the object being imaged.

These objects are further accomplished, at least in part, by acquiring stereotactic images with a scatter reducing grid.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the following derailed description read in conjunction with the attached drawings and claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, not drawn to scale, which include:

FIG. 1 is a side perspective view of the stereotactic needle biopsy apparatus of the present invention for converting a conventional mammography apparatus into a device for carrying out stereotactic mammographic guided needle breast biopsies;

FIG. 2 is a side perspective view of a conventional mammography apparatus incorporating the stereotactic needle biopsy apparatus of the present invention;

FIG. 3 is a side elevation view of the same conventional mammography apparatus incorporating the stereotactic needle biopsy apparatus of the present invention;

FIG. 4 is block diagram of the control system for controlling the digital image receiver shifting motor;

FIGS. 5A, 5B, 6A, 6B, 7A and 7B are a series of schematic diagrams illustrating the problem of image shifting during stereotactic imaging using the existing perpendicular stereotactic imaging geometry of a typical mammography apparatus and a collimating stainless steel needle biopsy compression paddle;

FIGS. 8A, 8B, 9A, 9B, 10A and 10B are a series of schematic diagrams illustrating the repositioning of the image receiver to solve the problem of image shifting during stereotactic imaging with a collimating stainless steel needle biopsy compression paddle;

FIGS. 11A, 11B, 11C, 12A, 12B and 12C are a series of schematic diagrams illustrating that the degree of shift is proportional to the thickness of the breast being imaged and biopsied;

FIG. 13A is top plan schematic diagram illustrating the relationship of the X-ray absorbing materials of a cross-pattern scatter reducing grid to the X-ray tube position during stereotactic imaging with the prior art devices employing oblique angle stereotactic imaging geometry;

FIG. 13B is a cross-sectional front elevation diagram of the structure shown in FIG. 13A taken along the line 13B illustrating the position of the X-ray tube relative to the film plane and X-ray absorbing materials of the cross-pattern scatter reducing grid;

FIG. 14A is a top plan schematic diagram illustrating the relationship of the X-ray absorbing materials of a conventional linear scatter reducing grid oriented in a conventional manner to the X-ray tube position during stereotactic imaging with the prior art devices employing oblique angle stereotactic imaging geometry;

FIG. 14B is a cross-sectional front elevation diagram of the structure shown in FIG. 14A taken along the line 14B illustrating the position of the X-ray tube relative to the film plane and X-ray absorbing materials of the conventional linear scatter reducing grid oriented in the conventional manner;

FIG. 15A is a top plan schematic diagram illustrating the relationship of the X-ray absorbing materials of a conventional linear scatter reducing grid oriented in an unconventional manner to the X-ray tube position during stereotactic imaging with the prior art devices employing oblique angle stereotactic imaging geometry;

FIG. 15B is a cross-sectional front elevation view of the structure shown in FIG. 15A taken along the line 15B illustrating the position of the X-ray tube relative to the film plane and X-ray absorbing materials of the conventional linear scatter reducing grid oriented in the unconventional manner;

FIGS. 16A, 16B and 16C are a series of schematic front elevation diagrams illustrating the relative position of the X-ray absorbing grid structures of a conventional X-ray scatter reducing grid oriented in a conventional manner relative to the X-ray tube in the perpendicular stereotactic imaging geometry employed by the present invention;

FIGS. 17, 18 and 19 are a series of comparative top plan schematic diagrams illustrating the position of the X-ray tube relative to the same grids and orientations illustrated in FIGS. 13A, 14A, and 15A;

FIGS. 20A and 20B are side elevation schematic diagrams of the translation stage, affixed to the image receiver support, used to move the image receiver according to the present invention; and

FIGS. 21A, 21B, 22A, 22B, 23A and 23B are a series of schematic diagrams illustrating the problem of image shifting during stereotactic imaging using the existing perpendicular stereotactic imaging geometry of a typical mammography apparatus with a collimating stainless steel needle biopsy compression paddle and a plurality of compact flat digital image receivers.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1, 2 and 3 primarily illustrate the preferred embodiment of the present invention. Referring to FIG. 1, there is generally shown an add-on stereotactic needle biopsy apparatus 10 which may be attached to a conventional mammography apparatus 100 to convert the mammography apparatus 100 into a device for performing stereotactic mammographic guided needle biopsies on a breast using the benefits of perpendicular stereotactic imaging geometry. The add-on apparatus 10 generally includes a base 12 having a first side 17 to which is attached an orthogonal three-dimensional needle guiding stage 14. The needle guiding stage 14 may utilize motors, if desired, to position the needle. The base 12 also has a compression plate engaging end 13 to which a compression plate 18 is affixed. Also, the base includes a compression paddle carriage 16 slidingly attached to the base 12 on its first side 17. Attached to the compression paddle carriage 16 is a stainless steel compression paddle 22 having an opening therein to permit a needle to pass through into a breast under compression. Compression paddle carriage 16 includes a knob 15 for manual movement of the compression carriage 16 along base 12. The compression paddle carriage may also include a motor for motorized sliding movement relative to the base 12. The biopsy apparatus also has a display window 48 for indicating the coordinates of the needle tip and the calculated coordinates of the lesion.

The biopsy apparatus 10 also includes a pivoting member 20 having a first end 27 and a second end 29. The first end 27 of the pivoting member is pivotally attached to a second side 19 of the base 12 near its compression plate engaging end 13. Stabilizing support arms 31 and 33 are affixed to the base 12 adjacent to its compression plate engaging end 13. Each of the stabilizing support arms 31 and 33 have ends 35 and 37 respectively which may be attached to the pivot shaft 104 of the mammography apparatus 100 via a collar 109 to aid with the affixation of the biopsy unit 10 thereto. Ends 35 and 37 of stabilizing support arms 31 and 35 secured to collar 109 provide a means for inhibiting the movement of the biopsy apparatus 10 during stereotactic X-ray imaging with the conventional mammography apparatus 100

Referring to FIGS. 2 and 3, the conventional mammography apparatus 100 generally includes a base 102, and a pivot shaft 104 having a first end 105 attached to the base 102 and a second end 107 which defines a pivot axis 21. The mammography apparatus 100 further includes an imaging arm 106 having an X-ray source end 108 and an X-ray receiving end 110. The second end 107 of the shaft 104 is attached to the imaging arm 106 between an X-ray source end 108 and an X-ray receiving end 110. The imaging arm 106 includes a pair of slots 25 positioned between the X-ray source end 108 and the X-ray receiving end 110. The slots 25 are shown as being offset from the pivot axis 21.

The mammography apparatus 100 further includes an X-ray tube head 112 having a focal spot 114 from which X-rays emanate. The X-ray tube head 112 is attached to the imaging arm 106 at the X-ray source end 108. An X-ray image receiver support 116 is attached to the imaging arm 106 at a point adjacent to the image receiving end 110. The image receiver support 116 provides a planar platform in which at least one edge of the plane is substantially perpendicular to the central ray emanating from the focal spot 114 of the X-ray tube 112. An image receiver 118 is mounted on the support 116 so as to present at least one edge of the associated image plane thereof perpendicular to the focal spot 114 of the X-ray tube head 112.

In FIGS. 2 and 3, X-ray image receiver 118 is illustrated as being a digital image receiver. FIG. 6A, for example, provides a schematic illustration of the principal components of the digital image receiver 118. The digital image receiver 118 generally includes a phosphor screen 120, a pellicle mirror 122, and a CCD camera 124 all enclosed in a light tight box 125. More specific details regarding the construction of the digital image receiver for mammographic imaging and processing digital mammographic images is described and shown in related U.S. Pat. No. 5,289,520. Alternatively, imaging can be accomplished using a standard mammography quality film-screen, similar or identical to that shown in related U.S. Pat. No. 5,289,520, together with X-ray scatter reducing grids.

Referring to FIGS. 1 and 3, the biopsy apparatus 10 also includes a pair of hooks 24 which are connected to the pivoting member 20. The hooks 24 provide a means for attaching the biopsy apparatus 10 to slots 25 on the image arm 106 mammography apparatus 100. In the preferred embodiment, pivoting member 20 on the biopsy apparatus 10 is attached to the image arm 106 via hooks 24, and pivoting member 20 allows the biopsy apparatus 10 to be angularly moved about the pivot axis 21 independent of the angular movement of the imaging arm 106 to which the pivoting member 20 is attached. This permits the imaging arm 106 to be positioned for stereotactic imaging while the breast is held stationary between the compression paddle 22 and the compression plate 18. Of course, imaging arm 106 and biopsy apparatus 10 can be positioned to perform a stereotactic needle breast biopsy procedure in any of the standard mammographic viewing positions such as the cranio-caudal or medio-lateral positions.

Still referring to FIGS. 1 through 3, the biopsy apparatus 10 further includes a removable needle holder 26 which is attached to the three dimensional needle guiding stage 14. The particular needle holder 26 illustrated in the figures is dimensioned to receive a biopsy gun 28 (shown in FIG. 3) to take core tissue samples of a breast. Other needle holder types, such as a holder for an aspiration needle or a holder for a localizing wire, may be employed without deviating from the spirit of the present invention.

In the preferred embodiment of the present invention, the needle holder 26 is attached to the three dimensional needle guiding stage 14 so that the axis of a biopsy needle 41, having needle sampling end 43 and needle holder engaging end 45, positioned therein is presented substantially normal to the plane formed by the fixed compression plate 18. In the preferred embodiment, the needle is moved in an orthogonal manner by the orthogonal needle guiding stage 14. Alternatively, the needle may be presented via a polar coordinate stage, such as that previously used by the TRC Mammotest. However, it is believed that the positioning of the needle tip using polar coordinates, rather than in the orthogonal coordinate system described above, is more difficult to visualize for the technician or user.

FIG. 6A generally illustrates the relative positioning of the X-ray tube focal spot 114, compression paddle 22 having an opening therein, compression plate 18 and a digital image receiver 118 for taking a non-stereotactic image with the biopsy apparatus 10 and mammography apparatus 100. FIGS. 5A and 7A generally illustrate the relative positioning of the focal spot 114, compression paddle 22, compression plate 18 and image receiver 118 during stereotactic imaging with the same biopsy apparatus 10 and mammography apparatus 100. As will be more fully explained below, one embodiment of the biopsy apparatus 10 of present invention includes features that make it compatible with a conventional mammography apparatus 100 equipped with a digital image receiver 118 so that images may be acquired in any of the positions illustrated in FIGS. 5A, 6A or 7A. Also, the biopsy apparatus 10 of the present invention is also fully compatible with the use of conventional film-screen image receivers and conventional scatter reducing grids typically used therewith.

Usually, the size and positioning of the phosphor screen 120, pellicle film 122, and CCD array in the CCD camera 124 of a digital image receiver 118 for a conventional mammography apparatus 100 are likely to have been optimized for taking non-stereotactic digital images, as shown in FIG. 6A. However, the size and positioning of these components may not necessarily be optimum for stereotactic imaging. As shown in FIGS. 5A and 7A, when the same digital image rece