The present invention relates to an x-ray apparatus, preferably for mammography and biopsy, of the kind which comprises:

- a tube arm which is rotatably secured in relation to a base frame and which supports the x-ray tube,

- a support plate, a compression bowl and a film cassette holder which are mounted so as to be mutually displaceable along the ray line of the tube,

- a stereotactic instrument which comprises a localization and biopsy needle holder device.

X-ray apparatus of this kind for mammographic and biopsic examinations are known. Such apparatus may also be used for preoperative localiza¬ tion of catheters and the like.

The stereotactic instruments of the known apparatus are typically ac¬ cessory instruments which are connected to the x-ray apparatus proper whenever needed. The support plates, the compression bowls and the film cassette holders of such apparatus are usually mounted so as to be mutually displaceable along a guide which is connected to a part of the tube arm running perpendicularly to the rotation shaft. Thus, these elements are non-rotatably secured on the tube arm and hence they rota- te jointly with same. In use, the stereotactic instrument is assembled by means of relatively complex fitting means which extends past the tube arm and is non-movably secured in relation to the base frame of the x-ray apparatus. In order to prevent the person to be x-rayed from rotating with the tube arm during the taking of x-rays from varying angles, the stereotactic instrument should comprise a support plate, a compression bowl and a film cassette holder in addition to the locali¬ zation and biopsy needle holder device, so as to permit angulation of the tube in relation to said elements by calculation of the coordi¬ nates to the specific puncture site on the part of the body under exa- mination. Thus, in the known apparatus an extra set of elements iden¬ tical with said three elements is required. Moreover, the localization and biopsy needle holder device coacts with a display device and a measurement and calculation device. The person to be examined may re-

tain the part of her body which is subject to examination in a fixed position irrespective of the rotation of the tube arm during the expo¬ sure from various angles.

It is the object of the present invention to remedy the above draw¬ backs associated with the known x-ray apparatus and to provide a more simple stereotactic instrument which is readily mounted on the x-ray apparatus and which also el minates the need for the costly duplicate elements having functions already provided for in the instrument.

According to the present invention this is achieved with an x-ray ap¬ paratus of the kind described above which is characterized in that the apparatus comprises a second arm which is rotatably secured in rela¬ tion to the base frame and the tube arm and which is provided with a guide supporting the support plate, the compression bowl and the film cassette holder and that the localization and biopsy needle holder device of the stereotactic instruments combines with a compression bowl to form a combined unit which is constructed so as to be secured in the compression bowl holder of the x-ray apparatus.

The support plate, the compression bowl and the film cassette holder being positioned on a guide which is mounted on the second arm and the second arm being mounted rotatably in relation to the tube arm, per¬ mits fixation of the second arm and the elements connected thereto when the tube arm is rotated in order to take images from different angles. Thus, the x-ray apparatus is suitable for taking images of any part of the body without the person or the part of her body under exa¬ mination changing position.

If desired, the tube arm and the second arm may furthermore be rotated jointly in use, i.e. they have fixed mutual angle setting, wherein the ray is typically perpendicular to the support plate, the compression bowl and the film cassette holder.

Thus, the apparatus affords the use one support plate and one film cassette only. The apparatus may be produced in an even more simpli¬ fied form as compared to the known apparatus, since the localization and biopsy needle holder device is combined with a compression bowl to

form a combined unit constructed to be secured in the compression bowl holder of the x-ray apparatus. The combined unit ma thus be mounted in the apparatus solely by dismantling the standard compression bowl and subsequently replacing the standard bowl with the combined unit. The display unit and the measurement and calculation device employed in the known apparatus may be employed in connection with an x-ray apparatus according to the present invention since the only adjustment needed is a minor adjustment of the software used in the measurement and calculation device.

Additionally, the apparatus according to the invention affords a higher degree of puncture accuracy since the localization and biopsy needle holder device may be placed in the immediate vicinity of the compres¬ sion bowl and hence in the immediate vicinity of the part of the body which is to be biopsied. Thus, the inaccuracies which may occur in the guide, the bearings etc., influence the positioning of the needle tip less as it is now rendered possible to employ shorter needles. More¬ over, the simplified assembly in the compression bowl holder of the x-ray apparatus is more simple and more accurate than the known as- sembly with a fitting means which is both complex and large in order for it to extend past the tube arm and become accurately secured on the base frame of the x-ray apparatus.

Description of the Drawings. The invention will now be described more in detail with reference to the accompanying drawing, wherein:

Figure 1 shows an x-ray apparatus according to the present inven¬ tion on which the stereotactic instrument is mounted,

Figure 2 is a magnified view of a combined unit comprising a localization and biopsy needle holder device and a compr sion bowl according to the invention, and

Figure 3 is a diagrammatical illustration of the taking of images with the x-ray apparatus set in two pre-determined angle positions.

Figure 1 shows the x-ray apparatus according to the invention. The apparatus is intended for mammography and biopsy examinations.

In the following the invention will be explained in terms of use for mammography, but it is obvious that the principle of the invention may also be applied in other kinds of x-ray apparatus.

The mammography apparatus comprises a tube arm 1 supporting an x-ray tube 2 and a Collimator 3 from which a ray extends substantially per- pendicularly to the rotation axis of the tube arm which will be sub¬ ject to further discussion below. The tube arm 1 is rotatably secured in relation to a base frame 4 and a shaft 7, the tube arm 1 being pro¬ vided with a bearing housing 5 which may rotate about the shaft 7 via two bearings 6. The shaft 7 is supported by two bearings 8 which are positioned in a bearing housing 9 secured to the base frame 4 by bolts 10. The shaft 7 may rotate in the bearing housing 9 in relation to the base frame 4 when a brake 11 secured to the one end of the shaft is released. The tube arm 1 provided with a counter weight 12 to balance the weight of the x-ray tube 2 and the Collimator 3 is rotated manual- ly in a conventional manner when the brake 11 has been released.

Moreover, the tube arm 1 may be rotated to occupy pre-determined angle positions in relation to the shaft 7. A teethed section 13 is secured to the shaft 7. A teethed wheel 14 is connected to the output shaft 15 from a motor 16 built into the tube arm 1. The teethed wheel is in mesh with the teethed section 13 and when the motor is activated the tube arm may swing from the one desired angle position to the other. Preferably, stoppers (not shown) are provided which define set angle positions for the tube arm 1. Friction-type engagement means provide an alternative to tooth meshing means.

At the end of the shaft 7 a second arm 17 is provided which is non-ro- tatably secured to the shaft 7. The second arm 17 is provided with a guide 18 mounted perpendicularly to the rotation axis 7' of the shaft 7. A cassette holder 19, a support plate 20 and a compression holder 21 are mounted on the guide 18 and thus the three elements are mutual¬ ly displaceable along the line of the ray, schematically indicated by 22, of the x-ray tube 2. The cassette holder 19 supports a cassette 23

for an x-ray film and may have a built-in ion chamber for exposure control. The cassette holder 19 may be displaced along the guide 18 and thus it permits the setting of the desired distance between the film and the focal point of the x-ray tube.

The support plate may also be displaced along the guide in order to permit the use of a magnification technique. The compression holder 21 may also travel upwardly and downwardly along the guide 18, e.g. driven by a pneumatic motor or cylinder (not shown). A compression bowl 25 may be located in the compression holder 21 via an arm 24, which bowl is intended for imparting a desired compression to a breast 26 during mammography.

The compression bowl 25 in Figure 1 is of the kind which is combined with the localization and biopsy needle holder device 27 of a stereo¬ tactic instrument in order to constitute a combined unit 28 construc¬ ted so as to be secured in the compression holder 21 of the mammography apparatus when the apparatus is to be used for biopsy. Thus, the com¬ bined unit 28 replaces the standard compression bowl (not shown) used in mammography.

For stereotactic exposures it is possible to set the tube arm 1 in two pre-determined angle positions in relation to the second arm 17. The pre-determined angle positions may be set by means of the above stop- pers and thus the tube arm may be set at e.g. 15° to the right of the second arm 17 and at 15° to the left of the second arm 17, respective¬ ly, as seen from the front of the apparatus. It goes without saying that other mutual angle settings may be used.

The mutual angle is established by activation of the motor 16 located in the tube arm 1 so as to move the tube arm 1 from its starting posi¬ tion parallel with the second arm 17 to a position where the tube arm and the x-ray tube 2 are set at e.g 15° to the right whereupon exposu¬ re is carried out. Then the motor 16 moves the tube arm and the x-ray tube to the other angle position in relation to the second arm 17 and a second exposure is carried out. When the film is developped it may be inserted into a measurement and calculation device (not shown) in order to measure and calculate the coordinates for a puncture site. If

biopsy is to be carried out the x, y and z coordinates may be determi¬ ned for correct positioning of a needle for retrieval of a tissue sample. The coordinates may be read off on a display (not shown) con¬ nected to the localization and biopsy needle holder device 27 by cables.

Figure 2 is a more detailed view of the combined unit 28 consisting of the compression bowl 25 which is mounted in the compression holder 21 of the mammography apparatus via an arm 24. The assembly is effected by a bayonet socket so as to afford ready exchange of the unit 28 for a standard compression bowl. The compression bowl shown is provided with a window 30 to be used during the biopsy; a needle (not shown) located in the needle guide of a needle holder 31 passes through said window 30. The construction shown permits positioning of the needle guide 32 in the immediate vicinity of the bottom 33 of the compression bowl 25, thus reducing the interference of play, if any, in bearings, guide etc., with the positioning of the needle tip. As shown, the needle guide preferably comprises arms 32' which are separated from each other and which each has a collar for controlling the needle. In principle, the local zation device 34 is constituted by three microme- tric screws: 35 for determination of an x-position, 36 for determina¬ tion of a y-position, and 37 for determination of a z-position for the needle tip. The micrometric screws may the set in manners known per se to a particular puncture site.

As will appear from Figure 3 the bottom of the compression bowl 25 is provided with a marker wire 38, preferably a cupper wire, which is seen as shadows 38A and 38, respectively, on the film in the film plane 23' during exposure. Such shadows are used in the well known measure- ment and calculation unit for the calculation of the coordinates of a specific puncture site 39 in the breast 26 under examination. The site 39 is also seen as two shadows 39A and 39B, respectively, on the film when the x-ray tube carries out exposure from positions A and B, re¬ spectively. From position A an exposure 40 is achieved and from posi- tion B an exposure 41 is achieved.

The use of the well known measurement and calculation unit permits calculation of the x, y and z coordinates for the puncture site 39.

Now the micrometric screws 35, 36 and 37 of the positioning device and the readout of the display permit positioning of the needle tip exact¬ ly in the site 39 for the retrieval of a tissue sample.

Figure 3 illustrates the determination/calculation of the x, y and z coordinates without, however, giving specific instructions as to the procedure involved, the calculation being known per se.