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BACKGROUND OF THE INVENTION
The present invention relates generally to a mammography apparatus and more
particularly to an improved upper and lower compression plate arrangement
for applying compression to the augmented breast during mammographic
examination.
Mammography is an X-ray examination technique used to detect and discover
anomolies of the female breast, including lumps, distortions or
calcification in the tissue. It is general practice to apply vigorous
compression to the breast to improve the quality, contrast and sharpness
of the resulting X-ray picture. Various devices can be found in the prior
art for applying pressure to the breast during such examinations, however,
none address the problem of mammography examination of prosthetically
augmented breasts. For example, U.S. Pat. No. 3,824,397 shows a device in
which pressure is applied to a plastic sheet which is placed on the
breast.
U.S. Pat. No. 4,090,084 relates to a mammography apparatus having a
pressure plate which is mounted so that the pressure can be applied
uniformly throughout the breast area. To enable such uniform pressure to
be obtained, the pressure plate is connected at its opposite ends to a
slide which is mounted on tracks on the cone of the X-ray machine.
U.S. Pat. No. 4,259,585 describes a device in which a compression plate is
mounted parallel to the support plate and is adjustable relative to the
support plate to adjust the spacing therebetween. The compression plate is
provided with a cut-out area. At the margin of the cut-out section,
marking is provided which is reproducible on the X-ray film for locating a
specific point in the cut-out section.
U.S. Pat. No. 4,122,350 suggests the use of a collimating device provided
to restrict the X-rays. The collimator is designed to fit closely over the
breast, the collimator being adjustable.
While various mammography compression devices are suggested in the prior
art, they do not provide appropriate compression of the breast tissue in
patients who have undergone breast augmentation procedures involving the
placement of prosthetic implants behind the breast tissue.
A particular problem occurs with patients who have had breast augmentations
with implants. It is estimated that over a million women nave undergone
augmentation mammaplasty in the United States. The breast implant
generally consists of a silicon gel or saline solution encapsulated within
a flexible envelope. The implant is effectively radiographically opaque.
With conventional dedicated mammography systems the lower support table is
generally fixed and the upper plate is movable to apply compression to the
breast. As the movable compression plate is lowered to apply compression
to the breast, the prosthesis also becomes entrapped along with the breast
tissue, totally or partially obscuring portions of the breast tissue and
thus degrading or interfering with the resulting X-ray photograph. For a
discussion of the effects of breast prosthesis on the screening technique
see "Mammograph and Breast Implants" in Plastic and Reconstructive
Surgery, July, 1988, Vol. 82, No. 1, Pages 1-7.
Accordingly, in view of the foregoing, it is a primary object of the
present invention to provide an improved mammography compression apparatus
which facilitates the taking of satisfactory mammographs in patients who
have undergone augmentation mammaplasty.
Another object of the present invention is to provide mating upper and
lower compression plates for X-ray mammography, which plates are
cooperatively contoured to avoid trapping the prosthetic envelope during
the compression of the breast tissue. The compression plate may be
provided as original equipment or may be appropriately adapted to an
existing X-ray apparatus.
Another object of the present invention is to provide compression plates
for a mammography X-ray system having relieved areas which allow the
plates to pass along the prosthesis without trapping the prosthesis
therebetween.
SUMMARY OF THE INVENTION
A conventional mammography apparatus has a fixed lower support table which
holds a film cassette and an upper compression plate is movable relative
to the support table and attached to the machine at an appropriate
attachment arm. In accordance with the present invention, an X-ray
mammography compression apparatus is provided having improved upper and
lower compression plates of a suitable X-ray compatible material. The
upper plate replaces the conventional compression plate and the lower
plate is secured on the top surface of the lower support table by a
suitable fastener or clamp. The inner or anterior walls of the compression
plates (the walls adjacent the patient) are contoured to define a relieved
area in the plates which allow the breast tissue to be selectively
compressed without trapping the prosthesis and thus avoid obscuration of
the X-ray by the prosthesis. The anterior walls of the plates are
preferably sloped conforming to the patient's anatomy to provide intimate
contact the patient's skin and thus assist in drawing the breast tissue
away from the prosthesis.
In another embodiment of the invention, the compression plates are
configured as a plurality of relatively movable strips. The anterior ends
of the plates are connected to a pliable wall so the configuration of the
relieved area defined by the wall can be varied in accordance with the
anatomical requirements of the patient.
In still another embodiment the conventional support plate is replaced by a
lower compression plate having a relieved anterior edge. The lower
compression plate has a magazine for accepting a specially shaped film
cassette for closer positioning of the breast tissue to the film. This
arrangement replaces the combination of the standard lower table and the
improved lower compression plate secured to the top of the table.
The above and other objects, features and advantages of the present
invention will become more apparent from the following detailed
description taken in conjunction with the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating a conventional dedicated X-ray
examination machine having upper and lower compression plates attached
thereto in accordance with the present invention;
FIG. 2 is an enlarged perspective view illustrating the upper and lower
compression plates;
FIG. 3 is a partial sectional view of the upper and lower compression
plates taken along section line 3--3 of FIG. 2;
FIG. 4 is a perspective view of an alternate embodiment of a lower
compression plate for mammograph examinations;
FIG. 5 is a perspective view of still another embodiment of a compression
plate constructed according to the present invention;
FIGS. 6 and 7 are sectional views taken, respectively, along section lines
6--6 and 7--7 of FIG. 5;
FIG. 8 is a cross-sectional view of a portion of a patient's breast
compressed between a support table and a compression plate illustrating
mammography technique using prior art support table and compression
plates;
FIG. 9 is a cross-section of a portion of a patient's breast with the
breast in a compressed position between the upper and lower compression
plates of the present invention;
FIG. 10 is a perspective view of the lower compression plate as modified to
receive a specially configured film cassette and also to assume the
functions of compression and support;
FIG. 11 is a perspective view of an alternate embodiment of the present
invention in which the compression plate is configured as an extension
having a relieved section secured over the conventional lower support
plate; and
FIG. 12 is a perspective view of a modified form of the compression plate
having a breast-retaining and confining wall.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings, FIG. 1 illustrates a conventional dedicated
X-ray machine having the compression plates of the present invention
attached thereto. The X-ray apparatus is generally designated by the
numeral 10 and includes a vertical cabinet 12 including vertical column 20
having an X-ray source housing 14 arranged at its upper end. The housing
14 contains the X-ray source and associated controls which form no
particular part of the present invention and detailed description is not
necessary as they are conventional and well known in the art. The X-ray
source emits a stream of X-rays downwardly as indicated to provide an
X-ray photograph by exposing special low radiation exposure film. The
Thomson-CGR Senographe 500 TX dedicated mammography system is
representative of apparatus of this general type.
Support table 21 extends from the lower end of column 20 having an upper
horizontal support surface 23. A recess or film magazine 22 is provided in
the support table for receiving a film cassette which is exposed by the
X-ray source to provide an X-ray photograph of the patient's breast. A
lower compression plate 24 is supported on table 21 by appropriate
retainer clips 27. Compression plate 24, as will be explained in detail
hereafter, is specially designed to apply compression to patients having
breast implants.
Oppositely disposed above the lower compression plate 24 is upper
compression plate 30. Compression plate 30 is supported on arm 28 of the
X-ray machine which arm is received within vertical slot 26 of column 20.
Arm 28 is vertically adjustable by means of a manual or motor-driven
mechanism such as a screw jack for adjusting the relative spacing between
the compression plates 24 and 30.
The present invention deals specifically with the design of the lower
compression plate 24 and the upper compression plate 30. As shown in FIG.
1, the lower compression plate 24 is fixed and the upper plate 30 is
vertically adjustable. However, it is within the scope of the invention
for the upper plate t be fixed and the lower plate adjustable or, in some
cases, both plates may be adjustable to apply the necessary compression.
The details of the compression plates are best seen in FIGS. 2 and 3. As
shown, upper compression plate 30 has a lower compression wall 44,
posterior wall 45, opposite side walls 46 and 47 and anterior wall 48. As
used herein, the term "rear" or "posterior" refers to an orientation away
from the patient and "front" or "anterior" refers to an orientation
adjacent the patient. For screen-film mammography, best results are
obtained when compression surface 44 is generally parallel to the surface
of the film in the film holder or magazine 22.
Compression plate 30 may be formed of any suitable material but is
preferably transparent to assist the medical personnel in the examination
and screening procedure and also to prevent any interference with passage
X-rays. For this purpose, the plate 30 may be a material such as clear
polymeric material, lucite, or plexiglas and may be fabricated by
convenient means such as injection molding or vacuum forming. Compression
plate 30 is secured to the X-ray machine by means of connector 40 which is
formed as an integral extension of the plate. Connector 40 extends
rearwardly from the center of the compression plate and is shown as being
a generally tubular member defining a receiver section which may be
attached to vertically adjustable arm 28 of the X-ray machine. Connector
40 and arm 28 can be detachably secured to the X-ray apparatus by any
convenient mechanical fastener such as a set screw 52 so that the
compression plate can be easily removed in the event the attending medical
personnel wish to attach a plate of different type or configuration to the
X-ray machine.
The anterior wall 48 of the compression plate 30 has a generally
transversely curved configuration defining a relieved area 55 at the
anterior edge of the plate. The particular curvature or shape of the wall
may vary somewhat although for most screening procedures an arcuate or
convex shape consistent with the curvature of the upper portion of the
breast is preferred. Also, as best seen in FIG. 3, wall 48 slopes upwardly
and forwardly from bottom wall 44 to generally conform to the conical
configuration of the upper half of the breast. In the event needle
localization procedures are necessary, apertures 66 may be provided in
selected suitable locations in the bottom wall.
Lower support plate 24 is also best seen in FIGS. 2 and 3 and is provided
with planar top surface 25, anterior wall 54, opposite side walls 56, 57
and posterior wall 58. The upper surface 25 of plate 25 serves as the
lower compression surface. The anterior wall 54 of the compression plate
is curved, preferably arcuate, defining a relieved area 65 in the plate.
As best seen in FIG. 3, anterior wall 54 inclines downwardly and forwardly
from planar wall 25. The lower compression plate rests on support plate 21
and is secured by retaining clips 27 arranged on the opposite side walls
which engage the opposite sides of the fixed support plate. Other types of
fasteners such as suction cups may also be utilized to removably secure
the lower compression plate to the support table 21 of the X-ray machine.
Compression plate 22 may be made from any suitable material which would not
interfere with the passage of X-rays and which is suitably rigid to
maintain parallelism with the compression plate. Again, lucite, plexiglas,
or other polymeric materials are suitable for this purpose.
A better understanding of the invention will be had from the following
description of use. During mammographic examinations using the improved
compression plate design of the present invention, a breast of the patient
is placed on the lower compression plate 24 and the compression plate 24
is lowered so that the breast is compressed between the upper compression
plate 30 and the lower compression plate. Application of uniform pressure
to the breast during the procedure results in improved diagnostic quality
of the resulting radiographic images. A suitable film cassette is inserted
into the film holder or recess 24 and the X-ray apparatus energized.
Generally while the X-ray is exposed, the patient remains in a stationary
position with respect to the mammography apparatus. Apertures 66 allow
needle localization procedures, if necessary. The X-ray source 14 and
support column 20 for the compression support plates are generally
rotatable with respect to the cabinet 12 so that various mammographic
projections can be made, as for example craniocaudad, 90.degree. medio
lateral and 45.degree. mediolateral.
FIGS. 8 and 9 illustrate the advantages of the mammography apparatus of the
present invention as applied to patients with prosthetically augmented
breasts. FIG. 8 illustrates mammography procedure on a patient having a
breast implant using conventional prior art support and compression
plates. In this cross-sectional view, the breast is shown in a compressed
condition as would occur in a standard craniocaudad mammographic
projection. With conventional compression and support table apparatus, the
prosthesis 100 becomes trapped in the position shown between the upper and
lower portions of the breast tissue which causes pressure to be applied to
the breast tissue in the direction arrow A. This force is 90.degree.
displaced from the desired force direction, which is indicated by arrow B
in FIG. 9. Accordingly, it will be seen that with X-ray radiation
impinging downwardly, the prosthesis may obscure all but a peripheral edge
of the breast tissue to the field of view of the X-ray apparatus. The
disadvantage is that for a complete and thorough examination, further
projections with significantly increased radiation exposure to the patient
may be required.
FIG. 9 is a view similar to FIG. 8 which illustrates the mammography
procedure utilizing the compression plates 22 and 30 of the present
invention. The configuration of the anterior walls 48 and 54,
respectively, of the upper compression plate 30 and lower compression
plate 24 prevent the prosthesis 100 from being trapped in the breast
tissue between the plates. Walls 48 and 54 are both transversely curved
and vertically sloped, allowing the prosthesis 100 to assume a position
against the chest of the patient, as seen in FIG. 9. The breast tissue,
due to its attachment to the skin layer and its ability to slide free of
the underlying prosthesis will be selectively compressed apart from the
prosthesis. The sloped surfaces of anterior walls, particularly wall 48 of
the upper compression plate, provide additional skin contact to assist in
drawing the breast tissue downwardly and forwardly away from the
prosthesis. Obscuration of the tissue by the prosthesis and undesirable
forward compression of the tissue exerted by the prosthesis are avoided.
FIG. 4 shows an alternate embodiment of the present invention in which the
upper compression plate 80 is of reduced transverse dimension "C" as
compared to the compression plate shown in FIG. 2. The reduced dimensional
size allows the compression plate to be used if the attending medical
personnel wish to apply localized compression to a portion of the breast.
Compression plate 80 has a body with opposite side walls 81, 82, planar
bottom wall 85, posterior wall 83 and anterior wall 84. Compression is
applied by the lower side of planar compression wall 85. Anterior wall 84
is shown having a curved configuration in which only a portion of the
arcuate configuration of the corresponding wall of the plate is shown in
FIG. 2. Surface 84 is downwardly sloped as shown conforming to the shape
of the breast.
Plate 80 is transversely movable on slide member 86 which is mounted on
connector 87 attachable to the X-ray machine. Slide 86 has a groove 88
which cooperates with tongue 89 on rear wall 83. Since plate 80 is
transversely movable, the plate may be selectively adjusted to compress
the desired section of the breast, for example, the area in one upper
quadrant. Similarly, the compression plate may be conveniently detached
from the slide and replaced with another plate of a different size or
configuration. In other respects, the construction of the compression
plate is has been described above.
FIGS. 5, 6 and 7 show still another embodiment of the present invention
which is generally designated by the numeral 100. In these drawing
figures, a modified compression plate is shown in which the anterior
breast-engaging surface may be selectively shaped to conform to various
anatomical breast conditions. The modification is illustrated in
connection with the upper compression plate but would also be applicable
to the construction of the lower compression plate.
The modified compression plate 100 has an upper surface 104 and a lower
compression surface 105. Opposite side walls 106, 108 and rear wall 109
form a unitary, generally U-shaped frame. Rear wall 109 has an integrally
formed connector 110 attachable to the X-ray machine. Since the plate
shown is the upper compression plate, front or anterior wall 112 slopes
downwardly and outwardly from surface 104 and is rearwardly convex to
conform to the patient's breast area.
Wall 112 extends between the side walls 106, 108 and is fabricated from a
pliable material such as silastic and can be selectively contoured into
the preferred shape in accordance with the anatomical requirements of the
patient at the time of the examination. To accomplish this, a plurality of
strips 120 of plastic or similar material are arranged in parallel fashion
within the frame with an appropriate clearance space 115 provided at the
rear of the strips. The individual strips are engaged to be relatively
slideable to one another due to the groove 125 which receives an
appropriate tongue 126 of the next adjacent strip. Anterior or posterior
movement of the strips will impart movement to the pliable end wall 112 in
the area of its point of attachment to the strip. Thus, by selective
adjustment of the strips relative to one another, the configuration of
surface 112 can be varied to accommodate the requirements of the patient.
This is best illustrated in FIG. 7.
Once the strips nave been adjusted and the desired configuration of surface
112 established, strips 120 are locked into the desired position by
tightening bolt 130 which has a threaded body 135 engageable within
internally threaded tube 140 extending transversely through longitudinal
slots 132 in the plates. By tightening locking bolt 130, transverse
pressure is applied to the plates locking them into the selected position.
FIG. 10 illustrates still another embodiment of the present invention which
is generally designated by the numeral 200. In this embodiment, the lower
compression plate 230 is shown supported in a generally horizontal
position on the X-ray machine 226 in a position aligned with the X-ray
tube to receive X-ray radiation. As has been described with reference to
other embodiments, the lower compression plate has a relieved anterior
surface 248 which is both curved and sloped to conform to the
configuration of the patient's breast area. A cassette holder 280 is
secured to the X-ray 226 apparatus at pivotal hinge member 255. Cassette
holder 250 has opposite parallel edges 260 and 261 and forward or anterior
edge 262. Edges 260 and 261 generally correspond to the edges of the
compression plate 230 and the anterior edge 260 of the cassette holder
conforms in shape to the lower edge of anterior wall 248 of the
compression plate. Thus, a film holder or magazine in a shape generally
corresponding to the shape of the adjacent compression plate 230 is
provided. A specially configured film cassette, not shown, is insertable
in the film magazine 280 with the film holder in the open position.
Thereafter, the film magazine is pivoted to a closed position and secured
in place at lock member 285. The advantage of the configuration shown in
FIG. 10 is that a more complete X-ray photograph is provided the examining
physician.
In FIG. 11 still another embodiment is shown which is generally designated
by the numeral 300. The lower fixed table 324 is part of the X-ray machine
is conventional. The improved lower compression plate 325 has opposite
side walls 326, 327 which are parallel and spaced apart a distance closely
approximating the distance between the side walls of the lower fixed table
324. The forward or anterior edge 352 of the compression plate 352 is
relieved and sloped as has been described to conform to the shape of the
breast of the patient to accommodate the prosthetically augmented breast.
As shown in FIG. 11, the compression plate 325 can be conveniently engaged
on the fixed plate 324 with the side walls 326, 327 of the compression
plate engaging the side walls of the table. The use of a flexible material
permits the compression plate side walls to be easily expanded to
facilitate placement of the plate on the lower support. When in place,
compression plate 325 can be moved anteriorly or posteriorly along the
support plate 324 as required. When the X-ray procedures are completed,
the compression plate 325 can be quickly disengaged from the support table
and the film cassette removed. The "snap-on" configuration of the
compression table attachment permits a compression plate of the desired
shape to be conveniently attached to the machine.
In FIG. 12, another embodiment of the present invention is generally shown
designated by the numeral 400. In this embodiment, an upper compression
plate 430 is shown which is constructed generally as has been described
with reference to FIGS. 1 to 3. In this embodiment, compression is again
applied by compression surface 446 being brought into contact with the
breast of the patient with the breast being supported on a lower
compression plate having a relieved area as described above. However, to
better contain the breast of the patient, the upper edge of the anterior
wall 452 is extended upwardly beyond the upper edge of side walls 455, 456
a predetermined distance as, for example, 2 cm. Further, the opposite
edges of this wall are extended posteriorly connecting with the opposite
side edges 455 and 456 of the compression plate. Thus, in the case of an
upper compression plate, the wall extension will extend toward the patient
following the general contour of the upper portion of the breast. The
upper edge of the extension wall 452 has a vertically-extending lip 460,
typically having a height of about 2 cm. which further assists in
containing the breast during the mammography procedure.
Thus it ill be seen that the present invention provides an improved
mammography apparatus and a preferred form of the invention has been
illustrated in the application. It is to be understood that various
modifications, alterations and changes may be made thereto without
departing from the spirit and scope of the appended claims. They are
intended to be encompassed therein.
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