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Claims  |
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I claim:
1. A portable compression apparatus for radiologically and graphically
locating breast lesions along three dimensional coordinates to facilitate
cytological examination and treatment thereof, comprising:
means for mounting said apparatus on the film cassette holder plate of a
dedicated mammography unit,
a top radiolucent compression plate having a cut-out area and a first
rectilinear grid scale around the periphery of said cut-out area,
a bottom radiolucent support plate having a second rectilinear grid scale
around the periphery thereof, said bottom plate being rotatably and
removably connected to said mounting means,
first means for supporting said top plate and for adjustably positioning
said top and bottom plates one relative to the other on either side of
said breast; said first and second grid scales constructed and arranged to
enable formation of corresponding grid scales on the resulting radiograph,
which corresponding grid scales, in conjunction with the representation of
the lesion also on said radiograph facilitate subsequent direct graphical
representation of the location of said lesion relative to said coordinates
within said breast,
a needle holder and guide assembly adapted to hold a needle for inserting
the tip thereof into the lesion, said assembly being adjustable in its
position relative to the lesion to enable accurate and reliable insertion
of said tip,
means providing support and guidance for said needle along two spaced
points of the needle to prevent deflection thereof during insertion of
said needle tip,
said needle holder assembly including first parallel rails on said top
plate having calibrations thereon for adjusting the position of said
assembly in the Y direction, a first sliding base mounted transversely on
said first rails, said first base having second parallel rails mounted
longitudinally thereon and having calibrations thereon for adjusting the
position of said assembly in the X direction; a second sliding base
mounted transversely on said second rails, and second base having a rod
extending vertically therefrom, said rod having calibrations and a
slidable needle holder thereon, said calibrations and slidable needle
holder for adjusting the position of said assembly in the Z direction;
said second sliding base including a releasable bushing having a lumen
through which said needle extends, said bushing and said slidable needle
holder providing support and guidance for said needle, said second base
and said needle holder also permitting release of said needle from said
apparatus while maintaining said needle tip at said location.
2. The compression plate structure of claim 1 wherein said grid scale and
said calibrations are all marked in the same units of measure.
3. The method of locating a breast lesion using an x-ray source comprising:
taking a first radiograph of a breast at a first position relative to the
x-ray source, wherein said breast is positioned between first and second
compression plates having first and second sets of radio-opaque locating
grids thereon respectively to provide a first radiograph of the lesion,
said first radiograph having a picture of said first and second sets of
locating grids thereon,
taking a second radiograph of the same breast at a second position relative
to said x-ray source wherein said breast is positioned between said first
and second compression plates having said first and second sets of
locating grids thereon, to provide a second radiograph of the lesion, said
second radiograph having a picture of said first and second sets of
locating grids thereon,
the position of said breast between said plates being substantially the
same in said step of taking said second radiograph as it is in said step
of taking said first radiograph,
measuring a distance between said first and second sets locating grids when
the compressed breast is there-between,
said first set of locating grids defining a first plane, the central axis
of the x-ray when taking said first radiograph having a first angle to
said first plane, the central axis of said x-ray when taking said second
radiograph having a second angle to said first plane, said first and
second angles being substantially different, and
analyzing the position of said lesion in said first and second radiographs
relative to coordinates of said first and second grids in each of said
radiographs to provide a location of said lesion in three dimensional
space.
4. The method of claim 3, wherein said second set of locating grids defines
a second plane, said first and second planes being parallel to one
another, and wherein said step of measuring is of the distance along a
line perpendicular to said first and second planes.
5. The method of claim 4 wherein said central axes of said x-ray beams in
said first and second positions intersect.
6. The method of claim 4 wherein:
said first and second sets of locating grids each have respective dual
spaced apart x-axes and dual spaced apart y-axes, said x and y axes
constituting perimeter coordinates, and y-axes of said first locating grid
being parallel to said y-axes of said second locating grid and said x-axes
of said first locating grid being parallel to said x-axes of said second
locating grid, and
said step of analyzing includes the graphical representation of four
planes, each of which includes the lesion and the x-ray source, each of
said planes being parallel to one of said axes of said grids.
7. The method of claim 6 wherein said step of analyzing includes the step
of:
determining at said first position a first lesion line defined by the
intersection of a first plane in space parallel to said x-axes and a
second plane in space parallel to said y-axes, said first and second
planes both passing through the x-ray source and the lesion,
determining at said second position, a second lesion line defined by the
intersection of a third plane in space parallel to said x-axes and a
fourth plane in space parallel to said y-axes, said third and fourth
planes both passing through the x-ray source and the lesion, and
determining the position of said lesion by the intersection of said first
and second lesion lines.
8. The method of claim 7 wherein said x-ray source in said first and second
positions is in the same x-z plane and wherein said distance between said
first and second sets of locating grids constitutes a distance along a
z-axis, and further comprising the steps of:
projecting said first and second lesion lines on a x-z plane and
determining the x and z coordinates of said lesion by the intersection of
said projected lesion lines on said x-z plane, and
projecting at least one of said first and second lesion lines on a y-z
plane and determining the y coordinate of said lesion by the intersection
of (a) a line parallel to said y-axis intersecting the z-axis at said z
coordinate and (b) said one of said projected lesion lines.
9. The method of claim 8 wherein said central axes of said x-ray beams in
said first and second positions intersect.
10. The method of claim 4 further including the step of placing a needle
tip in said breast lesion.
11. The method of claim 10 further comprising the steps of adjusting said
needle after placing said tip and advancing said needle after adjustment
into said breast.
12. The method of claim 11 further comprising the step of releasing the
needle from the compression plate apparatus while maintaining said needle
tip in said breast lesion.
13. Apparatus for locating a breast lesion using an x-ray source
comprising:
first and second spaced apart compression plates having first and second
sets of radio-opaque locating grids thereon respectively, and
mounting means for mounting said plates to a mammography unit and for
holding said plates spaced apart from one another when so mounted, said
mounting means including means to adjust the distance between said plates,
and
means for measuring the distance between said plates when said plates are
mounted by said mounting means to a mammography unit.
14. The apparatus of claim 13 wherein:
said first set of locating grids defines a first plane and said second set
of locating grids defines a second plane, and
wherein said mounting means is adapted to hold said plates on a mammography
unit such that said first plane and said second plane are held parallel to
one another.
15. The apparatus of claim 14 wherein: said first and second sets of
locating grids each consist of perimeter scales.
16. The apparatus of claim 15 wherein said first plate is a top plate and
is formed with a central cut-out area therein.
17. The apparatus of claim 16 wherein said first locating grid is on the
lower surface of said top plate and wherein said second locating grid is
on the upper surface of said second plate.
18. The apparatus of claim 16 further comprising: a needle holder and guide
assembly adjustable mounted to said top compression plate.
19. The apparatus of claim 17 further comprising a needle holder and guide
assembly adjustable mounted to said top compression plate.
20. The apparatus of claim 18 further including releasing means for
releasing said needle from said guide assembly.
21. The apparatus of claim 18 wherein said needle holder and guide assembly
comprises:
a sterile bushing for engaging the tip ends of a needle to the needle, said
sterile bushing being removable mounted to said top compression plate at a
position above said top plate, and
a keeper for holding said bushing at said top plate, said keeper having a
first state which holds said bushing in a predetermined position at said
top plate and a second state which permits an operator to release said
bushing from said top plate and to permit operator aspiration of tissue
from a predetermined zone adjacent to a lesion. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Technical Field:
The invention relates to radiation diagnostics and more particularly to an
improved method and apparatus for locating an internal breast lesion along
three-dimensional coordinates by radiologic examination and quickly and
accurately inserting the tip of a needle in the lesion for performing a
biopsy or marking the lesion's location by means of a dye or guide wire.
2. Description of the Prior Art:
Breast cancer is one of the leading causes of death in women in the United
States. In 1983, there were 114,000 new cases of breast cancer in this
country which represented about 26% of all new cancer cases in women. By
far the most useful technique in early detection is mammography,
radiological examination of the breast to discover the existence and
location of a lesion or "lump". Once a lesion is located, it is then
necessary to obtain a tissue sample for examination, or biopsy, so as to
determine the nature of the lesion, e.g. benign or malignant.
Generally, the methods available to obtain a tissue sample of the lesion,
or cells from the tissue, include surgical excision or needle biopsy and
aspiration. Before surgery can be performed, the lesion must be located so
that a visual tract can be seen from the surface of the skin to the
lesion. Such a tract is generally marked by a thin guide wire placed in
the tissue or a blue dye injected into the tissued along the tract.
However, multiple attempts at inserting the needle for placing the wire or
dye are invariably required. This is due to the fact that the breast has
neither a fixed shape nor reliable constant landmarks other than the
nipple. It must be maintained in relatively strict confinement during
location of the lesion or, with almost any movement of the patient, it
will deform and render meaningless and three-dimensional coordinates for
locating the lesion therein. Repeated decompression and recompression
exacerbate the difficulties greatly by making it extremely difficult to
accurately and precisely reproduce needle placement.
Similarly, needle biopsy and aspiration requires extreme accuracy and
several attempts at needle placement is both traumatic for the patient and
time consuming. Some attempts have been made at employing compression
grids with very limited success. Current compression grids only measure in
two dimensions and depth is left to be estimated based on the preliminary
mammogram, where the breast was compressed in an orthogonal direction to
the direction of needle placement compression.
In attempt to reduce artifacts in the mammogram associated with subject
motion and X-ray scattering, compression mammography was developed wherein
the breast is held in compression between two plates while an x-ray is
taken. Various designs for such a compression apparatus have been
developed and some representative examples are illustrated in U.S. Pat.
Nos. 4,599,738 to Panetta, et al.; 4,259,585 to Novak, et al.; and
4,573,180 to Summ.
Panetta discloses a wall mounted system which provides for magnified as
well as non-magnified compression examination of a female breast for
multiple positions while the patient remains seated or standing. Novak
discloses an apparatus which holds the breast in compression and has a
marking or scale on the upper compression plate which is reproducible on
the x-ray film and therefore locates the lesion, but in the X-Y plane
only. Summ discloses a motor driven compression apparatus for preparing
normal or enlarged x-ray images.
Granger, U.S. Pat. No. 1,370,640, discloses an apparatus for localizing
foreign bodies wherein the patient lies on a table having a transparent
top and a movable x-ray source therebelow. The x-ray source is moved until
the shadow of the foreign body being searched for is located in a small
fluorescent area of a screen positioned above the patient. A localizer
plate is then slipped between the patient and the table and is positioned
so that the shadow is seen lying directly over a cross within a small hole
in the localizer plate.
The x-ray source is then moved until the shadow of the foreign body is seen
to leave the central area of the cross and assure a similar position with
respect to a lateral area of the cross. A pointer on a vertical scale
between the fluorescent plate and the vertical plate is then raised until
its shadow blends with the shadow of the lateral area of the cross. The
pointer now lies on a vertical plane with the foreign body and a small
mark can be made on the skin at the cross to indicate the location of the
foreign body in the X-Y plane as well as at the end of the pointer to
indicate the vertical position of the foreign body.
Only one of these patents, Granger, provides for the three-dimensional
location of a foreign body. However, it is clear that the system of
Granger has at least two disadvantages when applied to mammography. First
there is the affect of even the slightest movement by the patient on the
table, which could cause a locating mark to be made in the wrong spot on
the skin.
Second, the x-ray source must move in relation to the x-ray film. Dedicated
mammography equipment in use today employs an x-ray source which is fixed
in a substantially perpendicular relation to the x-ray film. Therefore,
the apparatus of Granger could not be employed with available mammography
equipment.
Another attempt at location of a breast lesion is described in Price, J. L.
and Butler, P. D., Stereoscopic Measurement in Mammography, Proc. of the
British Inst. of Radiology, p. 901, Nov. 1971. The method employed
involves two exposures taken from a superior-inferior position with the
x-ray tube displaced 7 centimeters between exposures. These exposures are
viewed and aligned together on a mirror stereoscope and then aligned with
the lesion. Two parallax readings are taken from which the depth of the
lesion is calculated according to formulae described therein. The
difficulty of practising this technique with the currently available fixed
source equipment is apparent.
Another serious consideration in mammography is the diagnosis of a lesion
once located. The best method of forming such a diagnosis is to sample and
test, a portion of the tissue from the actual lesion. The obvious aim is
to sample the lesion tissue with the least discomfort to the patient. This
usually entails a procedure along the lines of a needle biopsy in which a
hollow needle is inserted into the tumor or lesion and a sample of the
tissue is drawn out, either with the needle after detachment by rotation,
or by other means such as aspiration.
A number of devices have been proposed to facilitate needle placement.
These are often referred to as stereotaxic devices and are exemplified in
U.S. Pat. Nos. 4,583,538 to Onik, et al.; 3,817,249 to Nicholson;
4,580,561 to Williamson; and 4,427,005 to Tener.
Onik, in FIG. 6 and the accompanying text, discloses a device for
positioning a biopsy needle in three-dimensions which requires computed
tomography to initially locate the lesion. The device of Nicholson is for
positioning electrodes in the x-y plane only.
Williamson discloses an apparatus employing two parallel compression grids
which are used to direct interstitial implants through the breast along a
line normal to the plates. Tener discloses a template for controlling the
location and placement of needles in a breast in preparation for placing
radioactive seeds.
Clearly it is desirable to insert the needle and draw the sample as
expeditiously as possible. This requires extreme accuracy both in location
of the lesion as well as subsequent placement of the needle, both of which
are greatly complicated by the pliancy of the breast. Furthermore, when
location of the lesion and placement of the needle are performed in two
separate operations, as is suggested by the references above which
generally disclose either means for locating the lesion or for placing the
needle, the problem is exacerbated greatly.
Attempts have been made to combine the two functions specifically in the
area of breast lesions. One such apparatus is marketed under the name TRC
MAMMOTEST by Tekniska Rontgencentralen AB, P.O. Box 121, S-183 22 TABY,
Sweden. The development of the instrument is described by Bolmgren,
Jacobson and Nordenstrom in Stereotaxic Instrument for Needle Biopsy of
the Mamma, The J. Roentgenol., 129:121-125, July 1977 and some of its
methods are employed in Svane, G., A Stereotaxic Technique for
Preoperative Marking of Non-Palpable Breast Lesions, Acta Radiologica
Diagnosis, 24, (1983) Fasc. 2, pp. 145-151.
With the MAMMOTEST, the patient lies face down in a prone position on a
horizontal platform mounted above the instrument with the involved breast
hanging through a hole in the platform and compressed between two plates.
Two x-ray exposures through the breast are taken by rotating the x-ray
source to plus or minus 15.degree. from the line normal to the center of
the film plate. A digital computer is then utilized to compute
mathematical expressions for the coordinates of the lesions according to
complex formulae set forth and explained in the Bolmgren publication.
Another method of location and needle placement is described in Yagen, et
al. Mammographic Needle Localization of Lesions Seen In Only One View,
Amer. J. Roentgenology, 144:911-916, May 1985. Briefly, the Yagen
technique involves a preliminary mammogram taken preferably of a
mediolateral view to determine the point of entry for the localization
needle, and over which a small adhesive marker is placed. The x-ray source
is then rotated 30.degree. without changing the position of the breast. An
exposure is made and the depth of the lesion is calculated as 1.73 times
the distance measured between the images of the tape marker and the
lesion. The mathematical basis for the factor 1.73 is derived in the
publication. A needle and subsequently a guide wire are placed based on
the point of entry and the calculated depth. As is apparent from an
analysis of FIG. 2 of the reference, Yagan makes the assumption that the
x-rays emanating from each position of the tube during a given exposure
are parallel to one another at approximately 36 inches from the x-ray
source. This assumption is not valid. X-rays do not emanate from a point
source as parallel rays but rather spread out with increasing distance
from the source. This introduces problems of parallax which could
seriously affect the accuracy of the Yagan device. Furthermore, there is
the problem discussed above relating to the natural pliancy of the breast,
in which two exposures are taken while attempting to avoid moving the
breast. At no time is compression employed.
In addition to the freestanding MAMMOTEST apparatus, Applicant is aware of
two other commercially available units designed to fit onto existing
mammography equipment. The first is the STEREOTIX instrument for fine
needle biopsy put out by CGR skandinaviska ab, Torshamnsgaten 28, Kista,
Box 1243, S-163 13 SPANGA, Sweden. This machine is also a digital
computer-based apparatus designed to fit specifically on a Thomson CGR
Senographe 500T mammography unit.
The other such machine is the CYTOGUIDE put out by Philips which also
requires a digital computer for calculation of the coordinates of the
lesion. This unit is designed to fit on a Philips mamography unit.
Both the STEREOTIX and the CYTOGUIDE units utilize the same complex
mathematical principles explained in the Bolmgren article with respect to
the TRC MAMMOTEST. In both the STEREOTIX and the CYTOGUIDE, the patient
may be sitting or standing, the breast is compressed between a compression
plate and a breast support/film holder, both of which are suspended above
what was the original breast support plate of the mammographic unit to
which the STEREOTIX or CYTOGUIDE is attached. However, as with the
MAMMOTEST, the breast is held stationary while the x-ray source and film
plate are rotated to take two views at plus and minus 15.degree. from the
orthoganal to the film plate. In all of the above-described prior art
units, symmetry of the two views taken is required for accurate
computation of the coordinates of the lesion which, for all practical
purposes, must be performed by computer.
TRC MAMMOTEST also provides a removable puncture device which is adjusted
to the calculated coordinates and then attached to the compression portion
of the apparatus. The puncture device does not allow for removal of the
needle from the device while its position in the lesion is maintained.
This is a considerable disadvantage in that it severely limits the types
of tissue sampling techniques available to the physician. Both the
STEREOTIX and the CYTOGUIDE also include a puncture apparatus, both of
which suffer from the same short-coming as the MAMMOTEST.
There are a number of other disadvantages associated with these
commercially available prior art devices. The TCR MAMMOTEST is a very
large freestanding device dedicated to the breast lesion localization and
needle placement as described. A substantial amount of expensive hospital
floor space is therefore required for this very costly machine despite its
extremely limited function. Further, as the Bolmgren article notes,
patients are chosen who have palpable or non-palpable lesions and who
require further cytological study. (Bolmgren, page 121, Procedure). The
original, traditional mammogram, in which the lesion is initially
identified and preliminarily located, is taken with the patient in a
sitting position. However, the MAMMOTEST requires that the patient be
prone and face down. Therefore, breast architercture surrounding the
lesion may well change rendering visualization on the MAMMOTEST very
difficult.
It should be noted that the other two devices, the STEREOTIX and the
CYTOGUIDE, are both designed to function with a particular mammography
unit and therefore their use is quite limited. Further, even if the
facility looking to add such a device already has the appropriate
mammography unit, the Applicant is advised that the attachments themselves
are extremely costly, in the vicinity of $50,000.00 for the CYTOGUIDE and
$60,000.00 for the STEREOTIX.
As noted above, all three units require the use of a digital computer for
calculation of the coordinates of the lesion. Besides the expense, this
requirement also increases the possibility of inaccuracy or even total
disablement of the apparatus based on the computer failure.
All three of the units also require exact positioning of the x-ray source
at plus and minus 15.degree. for accurate calculation of coordinates. Even
slight misalignment may substantially affect the computations.
Finally, none of these devices allow for release of the needle from the
positioning apparatus once it is advanced into the lesion without
withdrawing the needle from the lesion. Therefore, only the tissue
directly in line above, through and below the lesion can be sampled.
Applicant is aware of one other existing unit but does not know if the unit
is commercially available. It is called the MARK 3D Stereographic Breast
Biopsy Guide from AB MEDIDE and does not appear to employ the novel
apparatus and method described and claimed hereinafter.
SUMMARY OF THE INVENTION
The invention provides a portable compression grid and needle holder for
radiologic location of breast lesions along three-dimensional coordinates
and needle placement in the lesion to facilitate cytological sampling,
examination and removal thereof. The invention includes means for mounting
the apparatus on conventional mammography units, a top breast compression
plate having a cut-out area or portion and a bottom breast support plate,
each plate having a radio-opaque grid or scale therearound. The support
plates are adjustably connected to one another by a vertical support or
spine having a scale thereon for measuring in the Z, or vertical,
direction.
The apparatus is rotatably connected to the mounting means to facilitate
taking two x-ray exposures, one on either side of a line normal to the
plane of the x-ray film on mammography units having a stationary x-ray
source.
When the two views are taken, the radio-opaque grids from the top and
bottom plates will be reproduced on the film around the lesion. This
allows simple coordinates to be read directly from the film. Intersecting
lines and points can be drawn manually on graphs corresponding to the
grids on the plates according to the coordinates read from the film. One
graph locates the lesion in the X-Z plane and the other locates the lesion
in the Y-Z plane.
The apparatus also includes an adjustable needle holder and guide assembly
mounted on the upper support plate which is readily adjustable in
three-dimensions and immediately facilitates the insertion of a needle
directly and accurately into the lesion. In addition, the needle holder
assembly allows for removal of the needle from the assembly while
maintaining the needle point in the lesion to facilitate aspiration of
tissue as well as aspiration of tissue in the immediate area of the lesion
by allowing movement in three dimensions.
The exposures may be taken with the patient in a sitting or standing
position and the breast need never be removed from the apparatus from the
time that the first exposure is taken until the tissue sampling needle is
in place, a period which may well not be greater than a few minutes. This
alleviates the problem of a two part procedure where the architecture and
dimensions of the tissue surrounding the lesion may not remain constant by
eliminating the need for multiple location and/or needle placement.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the apparatus embodying the invention
looking toward the front end thereof;
FIG. 1A is a fragmentary perspective view of the needle holder portion of
the needle hub positioner assembly of the apparatus of FIG. 1 without a
needle placed therein;
FIG. 2 is a fragmentary front view of the bottom breast support plate of
the apparatus of FIG. 1;
FIG. 3 is a bottom plan view of the top breast support plate of the
apparatus of FIG. 1;
FIG. 4 is a fragmentary exploded perspective view of the base portion of
the needle holder and guide assembly of the apparatus of FIG. 1;
FIG. 5 is a partial section view of the base portion of the needle holder
and guide assembly along line 5--5 of FIG. 4, however, with the needle,
bushing and rectangular plate for maintaining the needle in the assembly
in place;
FIG. 6 is an example of an x-ray exposure of a breast with lesion taken on
the apparatus of the invention;
FIG. 7 is an example of another x-ray exposure of the breast of FIG. 6
taken on the apparatus of the invention after rotating the apparatus to
the opposite side of the plane normal to the film;
FIG. 8 illustrates the first graphical determination in the location of the
lesion of FIGS. 6 and 7, in the X-Z plane, according to the method of the
invention; and
FIG. 9 illustrates the second graphical determination in the location of
the lesion of FIGS. 6 and 7, in the Y-Z plane, according to the method of
the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings in which like structures are labelled with like
reference numerals, FIG. 1 represents the apparatus embodying the
invention designated generally by the reference numeral 10. The apparatus
10 includes a mounting bracket assembly 20 for mounting device 10 on a
table, film holder, etc. of an existing mammography unit. Assembly 20
includes a C-bracket 21 having threaded holes 22 in the top and bottom
tails 23 of the bracket 21 for thumbscrews 24. Bracket 21 also has a
transverse hole 26 through the longest section 27 of the bracket 21 and a
threaded hole 28 through section 27 approximately normal to and
intersecting hole 26.
The device 10 has a bottom breast support plate assembly 30 having a neck
portion 32 and a radiolucent support portion 34. Neck portion 32 has a bar
36 extending out from the rear portion thereof which is inserted through
the hole 26 on the bracket assembly 20 and maintained in a given position
by thumbscrew 35 to removably and rotatably secure support assembly 30 to
mounting bracket assembly 20. The bottom breast support plate 30 includes
a spine or support 50 which extends vertically from the top of neck
portion 32 and has a scale 52 engraved, printed, or otherwise permanently
affixed thereto along its length.
A top compression plate assembly 60 having a neck portion 62 and a
radiolucent compression portion 64 is adjustably mounted on the spine 50.
This may be achieved by the use of a square hole 66 through the neck
portion 62 of compression plate assembly 60 in conjunction with a
thumbscrew 68 as illustrated in FIGS. 1 and 3, or any other suitable
means.
Device 10 includes a needle holder and guide assembly 90 adjustably mounted
on the compression plate assembly 60, which will be described in detail
hereinafter.
Referring now to FIGS. 1 and 2, the bottom breast support plate assembly 30
may include a cut-out area 40 which provides a more stable securing of the
breast tissue. A radio-opaque or a x-ray absorbing grid 42 is marked off
around the periphery of support assembly 30 in any convenient units, such
as centimeters. The grid may be applied by any suitable method. Cut-out
area 40 also eliminates at least one layer of material through which the
radiation must pass, and therefore tends to provide a clearer image.
Bottom plate assembly 30 includes two matching triangular legs 44 which
serve to steady the apparatus when each of the two x-ray exposures are
taken, as will be described in detail with respect to the method of the
invention.
Vertical spine 50 may be separately manufactured and attached to neck
portion 32 of bottom assembly 30 by any suitably method. Spine 50 may also
be manufactured as one piece with neck and support portions 32 and 34,
such as by casting or molding. The vertical scale 52, should be marked in
units compatible with those of grid 42, and, when a breast is properly
inserted in the device 10, provides a convenient reference for the
thickness of the breast in compression.
Referring to FIGS. 1 and 3, top compression plate assembly 60 has a neck
portion 62 and a compression portion 64. Top assembly 60 is attached to
spine 50 such as by providing a square hole 66 through neck portion 62
which is dimensioned to fit snugly over spine 50 as shown. In this way
compression portion 64 is maintained in substantially parallel relation to
support portion 34 of bottom assembly 30. Compression assembly 60 is
maintained at a desired vertical level with respect to bottom assembly 30
by any convenient method such as thumbscrew 68.
Compression plate assembly 60 includes a cut-out portion or area 70 which,
when assembly 60 is mounted on spine 50, is essentially in line with
bottom support assembly 30. A radio-opaque or radiation absorbing grid 72
is applied around the periphery of area 70 preferably on the under side 74
of assembly 60 facing grid 42 on bottom assembly 30. Grid 72 is marked in
the same units as grid 42. Because of their radio-opaque nature, both
grids 42 and 72 will be reproduced on x-ray exposures taken with the
apparatus of the invention interposed between the x-ray source and the
film. In this manner, it is assured that vertical and horizontal lines
superimposed on the exposed films which intersect in the center of the
lesion being located will also intersect both the ordinate and the
abscissa of each of the grid reproduced in the films.
Further, compression assembly 60, as illustrated, has on its under side 74
two laterally extending arms or side leaves 76. Arms 76 have marked
thereon extensions in both directions of the X scale of grid 72. These
arms with extensions serve to substantially reduce the possibility that a
lesion in a rotated x-ray view will be located near the periphery of top
plate 64 and therefore off the scale.
On its top side 78 (FIG. 1), compression plate assembly 60 includes a pair
of rails 80 along the lateral sides thereof in the Y-direction having
ruled calibrations thereon which are in units coinciding with those of
grids 42 and 72 and vertical scale 52. Rails 80 function with respect to
needle holder 90 as will be explained.
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