Mammographic apparatuses

Abstract: In mammographic photography the breast (M) to be photographed is pressed and spread between holders (6,7) attached to the photographing apparatus (2,3). A beam (R) of X-radiation is directed from one side of the holders (6,7) through the breast (M) at depicting means (21) placed at the opposite side of the holders in relation to the source (2) of X-radiation, said depicting means being placed inside a film cassette or equivalent placed in connection with the frame (10) of the apparatus. The breast (M₁) to be photographed is placed on the top face of the lower holder (7), against which it is pressed from the root portion (J) of its upper side by means of the outer tip portion (6') of the upper press member (6); the upper press member (6) is displaced by pivoting it around its articulation point (8) so that it becomes substantially parallel to the support plane of the lower holder (7) in the frame part (10) that is stationary relative the source (2) of radiation and the part (3) for holding the depicting means (21); and when the upper and lower holders (6a,7a) become substantially parallel to one another, if necessary, the pressing of the breast is continued further by displacing the upper press member (6a) in its linear guides so that it retains its orientation.

Description: The invention concerns mammographic apparatuses comprising a frame part, on which a turnable frame part is mounted, most appropriately as turnable around a horizontal axis, and in which said frame part a source of radiation and means for holding the film cassette as well as holders for the breast to be photographed, to be placed between the source of radiation and said cassette supporting means, are fitted, which said breast holders are displaceable relative one another so as to press the breast to be photographed between said holders. Mammography means a method of radioscopy of breasts, wherein a roentgenogram is taken of the breasts. In connection with the photographing, the breast is pressed and spread in a way known in prior art between the holders in the photographing apparatus. Owing to the nature of the tissue to be photographed, in the photography a soft radiation is used, the anode voltage of the X-ray tube being about 20...28 kV. This results in problems of scattering, which are the more important, the thicker the tissue to be photographed is. In mammography, it would, however, be important also to depict so-called microcalcifications, whose diameters are of an order of 0.1 mm. As is known in prior art, in complete mammographic photography, three different projections are used. In mass photography, only one, as a rule vertical, projection is used. In addition to the roentgenograms taken in different projections, if necessary, enlarged photographs are taken of suspected locations. Prior-art apparatuses can also be used for so-called biopsy photographing. Biopsy photography means a method wherein the breast is photographed by using a so-called biopsy plate so that the openings in the biopsy plate become visible in the roentgenogram. In biopsy photography, the film is developed while the breast to be photographed is kept in its holders, and the finding, if any, is located with the aid of the holes in the biopsy plate, and with their aid a sample is taken from a suspected location. By means of the prior-art mammographic methods and apparatuses, it is also possible to take enlarged roentgenograms, which takes place so that a particular stand is placed on the normal breast holder, by means of which said stand the breast to be photographed is placed closer to the focus of the source of radiation. The use of such a separate stand is inconvenient, and, thus, one object of the present invention is to provide a new method and apparatus, wherein said separate stand becomes unnecessary. In mammography, attempts are made to press the breast as flat as possible, because soft secondary radiation is scattered. The thinner the breast can be made, the less secondary radiation can be scattered. To prevent scattering, lattice solutions of various types are also used. In respect of the prior art related to the present invention, reference is made by way of example to the mammographic apparatuses known from the following US Patents: 3,824,397, 3,971,950, 4,097,748, 4,599,738, and 4,613,982. The prior-art mammographic apparatuses have involved several drawbacks, which are supposed to be eliminated in certain respects by means of the new solutions of the present invention. One of the most important drawbacks has consisted of the difficulties in the operation of the prior-art apparatuses said difficulties including the necessity of the patient to move and to change her place when the projection or mode of photographing is changed, and it has been necessary to adjust the level of the breast holders in the apparatus between different processes of photography. This has increased the time taken by the photography, which is a considerable drawback in particular in the case of mass photography. In the prior-art apparatuses, difficulties have also occurred in how to be able to press and to attach the breast to be photographed between the holders in the apparatus in a favourable way. The stage of pressing the breast, which is included in mammography, is often experienced by the patients as quite disagreeable, and as this stage has, in the prior-art apparatuses, often been associated with a necessity to readjust the breast to be photographed in a more advantageous position, said drawback has been experienced as quite embarrassing. EP-A-0144670 discloses a radio-diagnosis apparatus in which there is a lower holder and a press member. The press member is articulate and connected to a spring by means of an arm. The arm and the spring are intended to stop the press member when the tensile force of the spring reaches a set value. EP-A-0146718 discloses a radio-diagnosis apparatus including depicting and frame means, inter alia. The frame part is stationary relative the radiation source and the part holding the depicting means, respectively. However, this apparatus does not include an upper pivotable holder functioning in combination with the other means thereof. Thus, an object of the invention is to provide a mammographic apparatus in which the various roentgenograms can be taken without having to shift the patient or to adjust the level of the apparatus when moving from one projection or mode of photography to the other. A further object of the invention is to provide a mammographic apparatus which can be automated to a very high extent. An apparatus in accordance with the invention is mainly characterized in that said upper holder is fitted pivotable around an axis, substantially perpendicular to the central axis of the breast in such a way that the breast to be photographed is to be pressed by means of the outer tip of the downwardly inclined upper holder, at the initial stage of the pressing, from above the breast at its root, and that hereupon, when the upper holder is being shifted downwards, it is pivotable around its articulation shaft so that it becomes substantially parallel to the plane of the lower holder. Some advantageous characteristic features of the apparatuses of the invention are disclosed in dependent claims 2 to 5. In the following, the invention will be described in detail with reference to the figures in the accompanying drawing while starting from a prior-art solution. Figures A and B show a known solution of mammographic apparatus, which illustrates the prior art. Figure 1 is a schematical side view of an apparatus in accordance with the invention as a whole. Figures 1a and 1b are schematical illustrations of a solution of mammographic equipment from two different projections. Figure 2 is a schematical illustration of the shifting of the upper press member into its position in accordance with the invention. Figure 3 is a schematical illustration of a mammographic apparatus in accordance with the invention in the situation of removal of the cassette after biopsy photography. Figure 4 illustrates the shields used in a mammographic apparatus in accordance with the invention. Figure 5 is a schematical illustration of a mammographic apparatus in accordance with the invention in its position of normal photography. Figure 6 is a schematical illustration of an apparatus in accordance with the invention in the biopsy photography position. Figure 7 shows a mammographic apparatus in accordance with the invention in the position of enlarged photography. Figure 8 is a schematical illustration of the tilting-mechanism of the upper press member. Figure 9 illustrates the width adjustment mechanism of the apparatus. Figures 10a..10d illustrate different exchangeable upper press plates. Figures A and B show a prior-art solution of mammographic apparatus, wherein the part 3 that supports the tube head 2 and the depicting means is mounted at its centre P of gravity on the vertical frame 4 of the apparatus 1. By means of such an apparatus, the advantage is obtained that the apparatus 1 can be balanced by and large. However, a drawback is that the apparatus 1 requires a locking device. Also, the apparatus of this prior-art solution causes a necessity both to adjust the height and to shift the patient laterally on moving from one projection C, D, E to the other, which makes the photographing slower and more difficult and prevents automation of the apparatus on moving from one projection to the other. To start with, referring to Fig. 1, the basic construction of the apparatus 1 in accordance with the invention will be described. The apparatus comprises a vertically displaceable vertical frame 4, to which a part turnable around a horizontal axis b-b is attached, said part comprising the tube head 2 and the press plates 6 and 7 as well as the film holder 3. The vertical frame 4 is arranged displaceable in the vertical direction on the frame part 54, said frame part 54 comprising a vertical guide or guides 57. Fitted around vertical guides 57 there are glide casings 56a and 56b. In connection with the pedestal 55 of the apparatus, a motor 51 is fixed, by means of which the transfer screw 52 is rotated. In connection with the threading of the transfer screw 52 there is a threaded part 53, by whose means the frame 4 is displaced vertically. In view of compensating for the weight of the displaceable frame 4 and of the other parts attached to same, a gas spring 58 is fitted between the frame 4 and the pedestal 55, said gas spring 58 being attached from one of its ends to the displaceable frame 4 by means of a projection part 59. In the apparatus 1 in accordance with Figures 1a and 1b, the part 3 that supports the tube head 2 and the depicting means is mounted on the vertical frame 4 of the apparatus 1 at the central axis a-a of the breast M 1 that is pressed between the upper press member 6 and the lower press member 7. Thereby the apparatus in accordance with the invention eliminates any necessity to readjust the apparatus or the position of the patient when moving from one projection f,g,h (different positions M 1 , M 2 , and M 3 of the breasts) to the other. The apparatus in accordance with the present invention, however, requires particular operations to counterbalance the apparatus (will be described in more detail in relation to Fig. 3), but said particular operations are reasonable in view of the advantage that is achieved. Moreover, the operation of the apparatus is motorized, so that complete counterbalancing is not indispensable or even needed. Thus, by means of the apparatus of the invention, it is possible to increase the degree of automation. In mammography, it is critical that the commonest location of cancer is in the outer upper quarter of the breast close to the body. Thus, it is important that the tissue at the root of the breast is included in the picture. When prior-art apparatuses are used, the nurse spreads the breast from the rear at the initial stage of the pressing of the breast, and thereat, when the upper press member approaches the breast, there remains no space for the hands of the nurse, and she must release her grasp before the press member locks the breast. On the contrary, in the upper press-member solution in accordance with the invention, which is shown in Fig. 2, there remains space for the hands of the nurse to spread the breast on the lower press member 7 at the initial stage of the pressing, the tip 6' of the press member 6 locking the press at the end of said initial stage. The upper press member 6 is mounted on the rod 10 by means of a linear journalling 9. Thus, the tip 6' of the downwardly inclined upper press member 6 grasps the breast M 1 at its root J, whereinafter the upper press member 6 is pivoted around its tip 6' at the same time as the upper press member 6 moves in its linear journalling 9 along the guide bar 10 and is pivoted around its articulation point 8. The articulation point 8 is provided with an adjustable spring loading, which permits pivoting of the upper press member 6 until it reaches its normal position 6a, i.e. the position parallel to the lower press plate, whereupon the pressing of the breast M 1 can be increased further if necessary while the press member 6a retains its orientation. In Fig. 3, the apparatus 1 in accordance with the invention is shown in the position after biopsy photography, corresponding to the removal of the film cassette. Thereat the breast M 1 is still pressed between the upper press member 6 and the lower press member 7, but the cassette rack 22 and the tube head 2 have been run slightly downwards by means of the motor 12 and the screw 13 for removal of the cassette 21. In Figures 2 and 3, a revolving part 25 is supported on the vertical frame 4 of the apparatus 1 by means of bearings 30, said part 25 being provided with a stationary lower press plate 7. The film holder 22 itself and the tube head 2 are attached to a common frame part 10, which is mounted by means of a linear journalling 23 on the part 25 revolving around the horizontal axis b-b. In Fig. 3, the upper press member 6 moves relative the frame part 10 in its journalling 9, and the lower press member 7 is stationary. Thus, without any separate additional part, it is possible to move over to enlarged photography, even without releasing the pressing. Moreover, by means of the solution in accordance with the invention, it is possible to substitute for a biopsy cassette rack. The vertical frame part 10 is displaced by means of the motor 12 and the screw 13. The revolving part 25 comprises a spiral gear 14, to which a spiral screw 15 as well as a primary gear 16 and a rotating motor 17 are connected. The movement of rotation is counterbalanced by means of a balancing gas spring 18, one of whose ends is connected to the wheel 14 by means of a lever, while the other end is connected to the vertical frame 4 of the apparatus 1 by means of an arm 18a. When moving over to a new projection g,h of photography, the rotation of the part 25 also takes place around the central axis a-a of the breast M, because the central axis a-a substantially coincides with the axis b-b of rotation of the part 25. Thus, when the projection of photography is being changed, the necessity of height adjustment of the apparatus 1 is eliminated. The apparatus 1 in accordance with the invention includes readiness for biopsy photography, so that separate installation of an additional part is not necessary when moving over to biopsy photography; only the upper press plate 6 must be exchanged. The upper press plate 6 is chosen in accordance with the film size used. The film sizes may be, e.g., 18 x 24 cm or 24 x 30 cm. Different types of upper press plates 6 of different sizes are needed for the apparatus 1 in accordance with the invention, for both film sizes, the plates needed for biopsy photography, as well as the spot photography plates. The upper press plates 6 are made of a material readily penetrable by X-radiation most appropriately, e.g., so that the transparent part is made of polycarbonate or acrylic and connected to the width-adjustment unit shown in Fig. 9. In this way the press plates can be made simple and inexpensive. Fig. 4 shows the shields used in the device 1 in accordance with the invention. The upper shield 26 is linked 27 with the upper press member 6 and attached by means of its guide groove 28 to the tube head 2. The lower shield curtain 29 is attached to the part 3 that supports the depicting means and to the lower press member 7. The upper shield 26 protects the head and jaw and the shoulders of the person to be photographed as well as, in the case of fat persons, any extra fatty tissue from the radiation beam R. The lower shield curtain is needed mainly only in enlarged photography to prevent access of fatty tissue of the person to be photographed between the lower press member 6 and the part 3 that supports the depicting means. Fig. 5 shows the apparatus 1 in accordance with the invention in the normal photographing position. In such a case, the lower press plate 7 has been run into contact with the part 3 that supports the depicting means 21. From normal photography it is possible to move over to enlarged photography and to biopsy photography without removing the breast M 1 (from between the upper press member 6 and the lower press member 7). Fig. 6 shows the apparatus in accordance with the invention in the biopsy photography position. Fig. 7 shows the apparatus 1 in accordance with the invention in enlarged photography. In the apparatus 1 of the invention, the ratio of enlargement can be chosen freely. Typically, the ratio of enlargement in enlarged photography is 1.5:1, but in the solution in accordance with the invention the ratio of enlargement can be chosen and adjusted continuously. Fig. 8 is a schematical illustration of the mechanism of articulation of the upper press member 6, which said mechanism permits the upper press member 6 to grasp the breast M at its root in accordance with what is explained in connection with Fig. 2, thereby leaving space for the hands of the nurse to "stretch" the breast at the initial stage of the pressing. After the upper press member 6 has pivoted against the load of the adjustable spring 31 to the normal position, i.e. substantially parallel to the lower press plate, the pressing can be continued in the same way as in prior-art solutions. During the pivoting movement of the press member 6, its tip 6' remains on the vertical line denoted with a dotted-dashed line in Fig. 8. The part denoted with the reference numeral 9' is a sledge that can move in the direction of pressing and that belongs to the mechanism. The parts of the articulation mechanism of the press member 6 also include a lever 32, which is connected to the casing 34 of the linear bearing by the intermediate of the rod 33, said casing being, e.g., a cross-piece, whose articulation pins are, in Fig. 8, denoted with the reference numeral 35. By means of an adjustable spring 31, the force is determined that is opposed to the pivoting of the press member to the horizontal position, i.e. the force with which the tip 6' of the press member presses the breast. Fig. 9 illustrates the width-adjustment mechanism of the exchangeable press plates 6, which said mechanism is provided with an emergency-release release torque switch. The width-adjustment wheel 36 is in direct contact with the holders, e.g. brackets 37, to which the press plates 6 are attached. Between the shaft 42 and the brackets 37, there are parts 38 which permit only axial movement. The frame 39 of the width-adjustment mechanism is attached to the rods 33 shown in Fig. 8. The shaft 42 is locked non-revolving in the frame part by means of the torque switch 40, which is provided, e.g., with such a torque-adjustment wheel as is provided with recesses 46 in which the pins 45 provided on the frame part are locked when the wheel is tightened. Figures 10a...10d show different press plates. Fig. 10a shows a press plate 6A, e.g., for a photographing press member of a size of 30 x 24 cm. The press plate can be placed into a regulating mechanism 42 which can be adjusted for different widths. In Fig. 10b, the "spot" photographing press plate 6B, which is provided with an opening 47, is denoted with the numeral 43, and the biopsy press plate with the numeral 44. In Figs. 10c and 10d, with reference numerals 42', 43',44', reference is made to the same parts as in Figs. 10a and 10b, but for smaller, e.g. 24 x 18 cm, photographing press members 6C. As has come out above, in the invention it is possible to use simple and inexpensive press plates in connection with a common mechanism 42 adjustable for different widths. Thereby substantial economies are obtained as compared with the fact that in prior art, as a rule, six different upper press members were required. It is to be emphasized strongly that above only some exemplifying embodiments of the invention have been described, and the scope of the invention also includes numerous modifications of the apparatuses of the invention which are obvious for a person skilled in the art, of which only the following should be mentioned in this connection. The apparatuses of the invention can also be applied in such mammography in which no X-ray film is used but in which the picture is reproduced by means of detectors which are sensitive to radiation and in themselves known, e.g. by means of electric detectors, from which an electric signal is obtained, on whose basis the picture is stored on storage media in themselves known. The definition 'film cassette or equivalent' used in the application includes such means for reproduction and storage of a picture. The scope of the invention also includes such modifications of the apparatus as have no separate lower breast holder at all but in which the film cassette or parts placed in its connection or any other, corresponding picture reproduction means referred to above act as the lower holder. In the following the patent claims will be given, wherein the various details of the invention may show variation within the scope defined in said claims.

Claims: Mammographic apparatus, comprising a frame part (4), on which a turnable frame part (25) is mounted (30), most appropriately as turnable around a horizontal axis (b-b), and in which said frame part (25) a source (2) of radiation and means for holding the film cassette (21) as well as holders (6, 7) for the breast to be photographed, to be placed between the source (2) of radiation and said cassette supporting means, are fitted, which said breast holders are displaceable relative one another so as to press the breast (M) to be photographed between said holders (6, 7), characterized in that said upper holder (6) is fitted pivotable around an axis substantially perpendicular to the central axis (a-a) of the breast in such a way that the breast (M) to be photographed is to be pressed by means of the outer tip (6') of the downwardly inclined upper holder (6), at the initial stage of the pressing, from above the breast at its root (7), and that hereupon, when the upper holder is being shifted downwards, it is pivotable around its articulation shaft so that it becomes substantially parallel to the plane of the lower holder (7). Apparatus as claimed in claim 1, characterized in that the press plate of the upper holder (6) is, by means of an articulation shaft, attached to a guide part (9) that can move in a linear way on the frame part (10) between the tube head (2) and the part (3) that supports the depicting means (21), and that said guide part (9) and articulation part (8) can be displaced relative one another. Apparatus as claimed in claim 1 or 2, characterized in that said turnable frame part (25) comprises a vertical part, which is provided with guides (23), in connection with which there is a guide-frame part (10), the source (2) of radiation being attached to one end of said guide-frame part (10) and the support-frame part (3) for the depicting means (21) being attached to the other end of said guide-frame part (10), and that between said guide-frame part (10) and the turnable frame part (25), transfer means are provided, preferably a motor and a transfer screw (13), by means of which the source (2) of radiation and the part (3) that supports the depicting means (21) can be shifted as one unit relative said frame part (25) and relative the press member (7) or press members (6, 7) that press the breast (M) to be photographed. Apparatus as claimed in any to the claims 1 to 4, characterized in that said turnable frame part (25) comprises a horizontal shaft which is supported by bearings (30) on the vertical frame part (4) of the apparatus, that said shaft is provided with a drive wheel (14), which is driven by a motor, most appropriately a screw motor, by the intermediate of the toothing on its outer rim, and that to said wheel (14) a gas spring device (18) is attached that substantially balances the turnable frame part (25) and the various parts attached to same during change of projection of photography. Apparatus as claimed in any of the claims 1 to 5, characterized in that the apparatus comprises a frame part (25) turnable around a substantially horizontal axis and mounted on a vertically displaceable frame (4), that said displaceable frame (4) is arranged to be displaceable by a motor, most appropriately a screw motor (51, 52), in the vertical direction on guides (56a, 56b, 57), and that, to compensate for the weight of the displaceable frame (4) and of the other parts attached to said frame a gas spring (58) or an equivalent compensation member is provided.

Inventors: MALMEN KARI, STROEMMER PEKKA, VIRTA ARTO, MALMEN, KARI, STROEMMER, PEKKA, VIRTA, ARTO, Strömmer, Pekka
Applicants: PLANMED OY
Application year: 1989
Main classification: A61B6
IPC codes: A61B6