The image data receiving means generally used in mammog- raphy are x-ray films placed in cassettes. Such cassettes are available in several different types, depending e. g. on the manufacturer of the cassette and the type of imag- ing the cassette is designed for. Often there are also differences between cassettes according to whether the film used in them is intended to be developed in a dark- room or e. g. in a special film development device. These so-called daylight cassettes are gradually replacing darkroom cassettes. In this field, many kinds of devices for the loading of cassettes with a film and for the re- moval of the film from cassettes have been developed, and likewise different labeling devices, i. e. devices e. g. for printing or exposing patient information and imaging parameters on the film in a cassette.

The imaging apparatus used in mammography generally have in their imaging area a space with at least one feed/eject opening, a cassette tunnel or equivalent, into which a cassette loaded with a film is entered and where it is positioned at a desired imaging position and from where it is removed and taken to a separate labeling stage. In many imaging apparatus, the cassette tunnel is so implemented that its open end or ends form a cassette

feed/eject opening. When both ends of the tunnel are open, the cassette can be moved in the tunnel by pushing it from one end of the tunnel and pulling from the other.

Moreover, in some devices the tunnel wall is provided with additional holes to make it easier to move the cas- sette.

However, handling the cassette in such a cramped tunnel, besides being difficult and awkward, is also time- consuming. Especially in mammographic screening studies, in which the cassette may have to be changed as many as 50 times an hour, cassette handling alone takes up a con- siderable amount of time, and for an individual patient this means that the imaging operation, which many pa- tients find unpleasant, takes an annoyingly long time.

Traditionally, mammography apparatus have been used to take various individual transillumination radiographs.

However, the information given by a transillumination radiograph is not always sufficient in a diagnostic sense. For this reason, there has been a trend in recent times towards discovering new imaging methods e. g. to make different layers in the tissue under imaging more clearly visible in the images. A contribution to this development has been the progress in the technology and prices of digital sensors toward a level that is begin- ning to enable their use in mammography apparatus, too, both in an economic sense and in respect of image quality and authority approval.

In many imaging modes that are more complex than transil- lumination imaging, a requirement is that it should be possible to change in some way the position of the object to be imaged with respect to the imaging means during the imaging process. Such a change can be implemented either as a stepwise action or as a continuous movement during imaging. When controlled movement of the object to be imaged is difficult to achieve, as is the case in mammog-

raphy, one can naturally seek for means for moving the imaging means.

Prior-art mammography apparatus have means for moving the imaging means in relation to the object to be imaged e. g. to change the height position of the imaging means in relation to the object to be imaged, means for interde- pendently revolving the imaging means around the object to be imaged, and means for inclining the radiation source in relation to the object to be imaged and the image data receiving means. As for other movements, cer- tain apparatus also have means for moving e. g. a screen placed near the radiation source to define the radiation beam in a desired manner, and even means for moving the object to be imaged during the imaging process. However, independent movements of image data receiving means that may be needed during imaging have been difficult to im- plement in a desired manner because, if the structure of the apparatus has permitted such movements at all, they have had to be carried out manually.

In some mammography apparatus, difficulties have been encountered in getting the cassette correctly positioned in the imaging area. If the cassette is in the wrong po- sition, this may result in leaving part of the tissue to be imaged outside the area of which an image is formed on the film or other receiving medium, which may necessitate renewal imaging. This creates extra work and an unneces- sary additional exposure of the tissue to radiation.

Often the actions requiring handling of the cassette in the cassette tunnel have to be performed in ergonomically difficult working positions. This is the case especially when more than one image is taken of the same object, possibly even on the same film, in which case the cas- sette has to be changed or moved to a new position in the cramped cassette tunnel while the object to be imaged may remain positioned during all this time, in mammography in

practice generally compressed between the compression plates of the imaging apparatus.

Recording patient information, dates, imaging parameters and projections etc. on the film or equivalent is an es- sential part of the imaging process. Especially in mammo- graphic screening studies referred to above, there is a great risk of labeling errors occurring due to human fac- tors. When the actions related to labeling are carried out as an operation physically separate from the actual imaging process, the cassettes may be interchanged when being taken from the imaging apparatus to the labeling station. Thus, information of a wrong patient and/or wrong imaging parameters may be entered on the film. And when human activities are concerned, it may even happen that some or even all of the data is not recorded at all when the labeling of an individual cassette or a whole batch of cassettes is accidentally neglected e. g. as a result of a lapse of memory. On the whole, labeling the films is an operation that requires accurate management and contributes for its part to the total duration of the imaging process.

The object of the invention is to eliminate above- mentioned drawbacks in a profitable way that improves working comfort and ergonomics in the imaging process, which involves no need to enter or remove the film cas- sette through narrow holes or to move it in the cramped cassette tunnel of the mammography apparatus.

One of the objects of the invention is to enable a more efficient utilization of time especially in conjunction with mammographic screening studies by reducing the time spent between exposures.

A further object of the invention is to achieve an ar- rangement in which, when a cassette is being loaded into the mammography apparatus, an automatic system according

to preferred embodiments of the invention seizes the cas- sette and drives it to the correct imaging position in the cassette tunnel, thus allowing the operator of the apparatus to proceed sooner to other actions in prepara- tion for imaging.

A further object of the invention is to enable accurately correct positioning of the image data receiving means in the imaging area so as to minimize the need for taking renewed images in consequence of inaccurate positioning of the tissue to be imaged.

Another object of the invention is to achieve an arrange- ment in which an exposed cassette can be automatically driven out of the cassette tunnel when desired, so that the operator of the apparatus could easily change/remove the cassette without having to dig it out from the open- ing of the cassette tunnel.

In certain preferred embodiments of the invention, the object is to achieve an arrangement in which the re- cording of patient information and imaging parameters on the film, which constitutes an essential part of the im- aging process, can be performed automatically in the im- aging apparatus in connection with the imaging process.

An object of preferred embodiments of the invention is also to achieve an arrangement that can be used for mov- ing image data receiving means of different types and sizes in the imaging area of the imaging apparatus.

A further object of the invention and some of its embodi- ments is to provide possibilities to use a mammography apparatus even in imaging processes requiring complex movements of the imaging means and their accurate con- trol, and in general to provide better possibilities to accurately and with ease move the imaging means in mammo- graphic imaging processes.

The problems described above are solved and the objects stated are achieved by a solution according to the funda- mental idea of the invention disclosed in the present application, in which the mammography apparatus is pro- vided with devices by means of which the image data re- ceiving means can be easily and accurately moved in the cassette tunnel or a corresponding space in the mammogra- phy apparatus, using control means and/or automatically.

In the following, some of the preferred embodiments of the invention will be described in greater detail with reference to the attached drawings. However, the inven- tion is not intended to be exclusively limited to these embodiments; instead, its exact essential features are presented in the claims below. In the attached drawings, Fig. 1 presents a typical mammography x-ray apparatus.

Fig. 2 presents a typical C-arm structure of the mammog- raphy apparatus, Fig. 3 presents an arrangement according to the invention for moving the image data receiving means that are used in mammography, and Fig. 4 presents means according to a preferred embodiment of the invention for labeling of the image data receiving means in the cassette tunnel of a mammography apparatus.

The mammography x-ray apparatus 1 presented in Fig. 1 consists of a frame part 11 and a C-arm 12 connected to it. Typically, placed at opposite ends of the C-arm 12 are a radiation source 13 and an image data receiving means 14', which is located e. g. inside a so-called bot- tom shelf structure 14. These imaging means 13,14', be- ing placed inside the casing of the apparatus, are not actually visible in Fig. 1. In addition, placed in the area between these imaging means 13,14', typically near

the image data receiving means 14', are means 15,16 for positioning the object to be imaged in the imaging area.

Typically, the C-arm 12 can be both moved vertically and horizontally in relation to the means 15,16 for posi- tioning the object to be imaged and rotated in relation to the frame part 11. The positioning means 15,16 typi- cally consist of an upper compression plate 15 and a lower compression plate 16, and the lower compression plate 16 may also be arranged to function as a so-called bucky."Bucky"means a grid structure placed between the tissue to be imaged and the image data receiving means to prevent radiation scattered from the tissue from reaching the image data receiving means.

Fig. 2 presents one C-arm structure 12 used in mammogra- phy apparatus. The C-arm 12 in Fig. 2 differs from the structure in Fig. 1 especially in respect of the way in which the cassette tunnel or similar space 17 has been arranged in the imaging area of the apparatus. The solu- tion illustrated in Fig. 1, in which both ends of the cassette tunnel 17 are closed and a cassette 14'is en- tered into the cassette tunnel 17 by driving the bottom shelf structure 14 downwards so that a space is formed between it and the lower compression plate 16, allowing the cassette 14'to be inserted into the cassette tunnel 17 via this space from above, is fairly seldom used in mammography apparatus. Fig. 2 presents perhaps a more typical solution, in which at least one end of the cas- sette tunnel 17 is open, allowing the cassette 14'to be inserted directly into the tunnel 17 from the side of the structure, without requiring operation of the means for driving the C-arm 12.

Generally speaking, in mammography systems there are used more or less integrated structures of several different types for forming the assembly consisting of the bottom shelf, lower compression plate and bucky/grid 14,16 and the associated cassette tunnel or similar space 17. For

example, in the solution illustrated in Fig. 2, the cas- sette tunnel 17 has been integrated as a part of the lower compression plate/bucky/grid structure 16 of the apparatus. Anyway, all cassette tunnel solutions have the common aim of bringing one edge of the cassette tunnel 17 as close as possible to that wall 18 of the bottom shelf or similar structure 14,16 which comes into contact with the chest during imaging, because the image data receiv- ing means must be so placed in the imaging area as to allow a maximal amount of tissue even in the region of the sternum and armpit to be imaged.

When the cassette tunnel 17 has been arranged to be loaded in a horizontal plane-while the C-arm 12 of the mammography apparatus is in a vertical position as shown in Fig. 2, its feed/eject opening is generally disposed in a lateral location as seen from the direction 18 from which the tissue to be imaged is entered. This obviates the need for re-positioning the object to be imaged, which is an awkward operation that may be unpleasant to the person being imaged, only because a change of cas- sette 14'is needed.

Fig. 3 illustrates an arrangement according to the inven- tion which allows the entry, the ejection and if so de- sired, even other kinds of movements of a film cassette 14'in the cassette tunnel 17. In the embodiment illus- trated in Fig. 3, the arrangement for moving the cassette 14'in the cassette tunnel 17 comprises a bottom shelf 14, depicted in a sectioned view in the figure, means 19 for moving the cassette 14', a button 20 for starting the ejection of the cassette 14', and a bucky 16. The means 19 for moving the cassette 14'comprise a driving roller 21, a driving roller motor 21 not visible in the figure, being placed below the bottom shelf 14, and a turning shaft 22 functionally connecting the roller 21 and its motor and provided with a gearing 22'. In the arrangement in Fig. 3, the cassette tunnel 17 is so implemented that t forms a part or the bucky 16, with an opening/openings

at its sides serving as cassette 14'feed/eject openings.

The means 19 for moving the cassette 14'are mounted on a carriage 23 which can be moved along guide rails 24 and which is connected to a spring 25 continuously tending to draw it by means of a drawing band 26 toward that end 18 of the bucky 16 which comes into contact with the chest.

The bottom of the bottom shelf 14 is also provided with an elongated aperture, not shown in Fig. 3, laid in a direction parallel to the guide rails 24, the shaft 22 of the driving roller 21 going through this aperture. Thus, the means 19 for moving the cassette 14'can move in the direction of this aperture and the guide rails 24. The cassette tunnel 17, e. g. its bottom, may additionally be provided with one or more sensors 27 which are connected to the control means (not shown in figure 3) of the appa- ratus to probe the position of the cassette 14'in the cassette tunnel 17.

Disposed on the side opposite to that wall 18 of the bucky 16 that comes into contact with the chest of the object to be imaged is arranged an elongated cut-out or groove 28 substantially parallel to the guide rails 24, into which the shaft of the driving roller 21 is directed when the bucky 16 is being mounted on the bottom shelf 14 from the direction of the wall 18 placed against the chest. The length of this cut-out 28 is so designed that it will position the driving roller 21 in relation to the cassette tunnel 17 so that the circumference of the roller 21 will come into contact with the side wall of the cassette 14'as it is fed in the cassette tunnel 17.

A spring 25 continuously draws the means 19 for moving the cassette 14'toward the cassette 14', ensuring that a frictional force sufficient for converting the rotational motion of the roller 21 into a linear movement of the cassette 14'exists between the sidewall of the cassette 14'and the driving roller 21. In the solution illus- trated in Fig. 3, the guide slot 28 and guide rails 24 for guiding the bucky 16 are disposed at an angle sub-

stantially perpendicular to the feed direction of the cassette 14'in the cassette tunnel 17, but naturally they may also be arranged at a different angle.

In mammography, cassettes 14'of different sizes are com- monly used to meet different imaging needs. The arrange- ment presented in Fig. 3 is modified so as to allow the use of another cassette size, by replacing the bucky 16 on the bottom shelf 14 with one having a cassette tunnel 17 dimensioned for the other cassette size and a cut-out or recess 28 coming into contact with the driving roller 21 that has a length corresponding to this arrangement, by means of which cut-out or recess the means 19 for mov- ing the cassette 14'are moved along the guide rails 24 to correct position for moving this different-sized cas- sette 14'.

The arrangement illustrated in Fig. 3 may function e. g. as follows. When a cassette 14'is fed through the feed opening into the cassette tunnel 17, the control system of the apparatus detects by means of a sensor 27 placed in the tunnel 17 that a cassette 14'has been entered in the tunnel 17 and starts the drive motor of the driving roller 21. As the cassette 14'is pushed further in, its rear edge meets the driving roller 21, which begins to draw the cassette 14'into the tunnel 17, whereupon the person inserting the cassette 14'can release his/her grip of it. Preferably, into the cassette tunnel 17 open at both of its ends a sensor 27 is provided in the area of both of the feed openings, in which case the control system will control the drive motor of the driving roller 21 to rotate in the appropriate direction to draw the cassette 14'into the tunnel.

Disposed at a suitable location at the other end relative to the feed opening of the tunnel 17, there may be an- other sensor 25 (not shown in the figure) to detect the edge of the cassette 14', allowing the control system

either to stop the motor or to drive the cassette 14' from this detection point to a given other imaging posi- tion as required in each case. In most cases, this posi- tion is the location where the midpoint of the cassette 14'lies on the center axis of the field of rays used for imaging. According to the invention, the control system of the apparatus may be so implemented that it also in- cludes an ability to measure and learn the correct posi- tion of the cassette 14'in the tunnel 17. After the cas- sette 14'has been correctly positioned, the control sys- tem gives a permission for starting the actual imaging process.

Upon completion of the imaging process, the means 19 for moving the cassette 14'drive the cassette 14'out of the cassette tunnel 17 either on the basis of a signal ob- tained from a cassette eject button 20 or automatically e. g. via a predetermined eject opening. The arrangement preferably comprises two or an even number of cassette eject buttons 20, which are disposed substantially near each end opening of the cassette tunnel 17. The control system identifies which one of the buttons 20 has been pressed and drives the cassette 14'out of the tunnel 17 via the eject opening corresponding to this button 20. In the embodiment illustrated in Fig. 3, the means 19 for moving the cassette 14'do not automatically drive the cassette 14'far enough out of the eject opening to allow it to fall but only far enough to make it easy for the operator of the apparatus to get hold of the cassette 14' in order to remove it from the tunnel 17.

Among the advantages of the embodiment of the invention as presented in Fig. 3 are the profitableness resulting from its structural simplicity, and especially its small space requirement. In a mammography apparatus, it is not recommendable to fit any complex arrangements in the re- gions below the lower compression plate because any large

structures in these areas are a significant obstruction to patient positioning for different projections.

In the embodiment presented in Fig. 3, the means for mov- ing the cassette in the cassette tunnel comprise only one roller, but naturally more rollers can be used without departing from the basic idea of the invention.

An alternative solution for providing the apparatus with means for moving the cassette according to the invention is to use two driving rollers immovable in the plane of the cassette feed direction, at least one of which is provided with means for implementing an axial motion of the roller. By placing such cassette moving means at suitable locations in the cassette tunnel or its immedi- ate vicinity, it will be possible to use one driving roller for moving a cassette of one size and another roller for moving a cassette of another size, and this axial movement permits a roller which is used for moving a cassette of a given size but which would prevent some other bucky, cassette and so on from being fed into the cassette tunnel 17 to be drawn out of the cassette tunnel when necessary.

Another alternative way of providing the apparatus with means for moving cassettes of different sizes is to use a single driving roller having an increased length in the direction of its rotation axis, which is brought into the cassette tunnel or to a substantially close vicinity to it in a horizontal position, i. e. in an orientation par- allel to the bottom/top of the cassette tunnel, and posi- tioned there in a fixed location. When the length of the roller is suitably selected, it will be long enough to move cassettes of different sizes.

Naturally, a roller is not the only driving means appli- cable for moving a cassette in the cassette tunnel as provided by the invention; instead, in principe, any

known/applicable power transmission solution can be used.

However, according to the fundamental idea of the inven- tion, it is preferable to use means that require only little space and that can simply be placed in the cas- sette tunnel or in its immediate vicinity in a mammogra- phy apparatus. Such solutions typically include, however, rollers or other drive wheels or equivalent coming into a direct or indirect contact with the cassette like those described above, from which it is possible to construct simple overall solutions that enable cassettes of differ- ent sizes to be moved in the cassette tunnel. Correspond- ing means can advantageously even be used to provide the cassette tunnel or similar space with a drive system by means of which the cassette can be moved in the tunnel both in its feed direction and in a direction substan- tially perpendicular to the feed direction. In this way, conditions are created for the use of the imaging appara- tus in so-called spiral or complex motion tomographic imaging, or conditions for solutions that can be utilized in one preferred embodiment of the invention, the use of means for moving the cassette in co-action with means for labeling of films, also disposed in the cassette tunnel.

In the following, these embodiments of the invention will be described in some more detail, but as for bidirec- tional cassette movement mentioned above, we can already state at this point that, by suitably arranging the cas- sette tunnel and the means for moving the cassettes, it will be possible to use in the imaging apparatus even cassettes of different types and sizes whose so-called labeling window may be located at different positions, because, using cassette moving means like this, the cas- settes can be correctly positioned in the cassette tunnel in alignment with the labeling device even if the latter are stationarily mounted in the apparatus.

An additional feature of the invention is a possibility to use the cassette moving means even for other purposes besides cassette feed and eject functions and positioning

of the cassette in the cassette tunnel. One embodiment of this type relates to the labeling of films, i. e. to the recording of imaging parameters, patient information etc. on the film. FI patent application 19992537 filed simul- taneously with the present application contains a more detailed discussion of the problems associated with prior-art labeling arrangements and the special features of an invention concerning a labeling arrangement, pre- sented in the application in question. In this context, we shall only describe an embodiment in which a labeling device as presented in Fig. 4 is so arranged in conjunc- tion with the cassette tunnel as to allow the labeling of the film to be performed directly in the cassette tunnel.

The means 3 for the labeling of films presented in Fig. 4 comprises a frame part 31, a carriage 33 functionally connected to the frame part 31 via guide rails 32, a screw conveyor 35 for moving the carriage and a motor 36 driving the screw conveyor. Mounted on the carriage is a display or other recording element 27 and a contact means 38, such as a pin or equivalent. A labeling device 4 like this can be arranged in conjunction with the cassette tunnel either so that the desired markings can be re- corded on the film while the cassette is in a typical imaging position or so that the cassette is driven to a given labeling position for labeling. In both cases, the means of the invention for moving the cassette can be utilized for opening and closing the shutter of the la- beling window of the cassette so that when the cassette is in its labeling position, its labeling window is lo- cated in a position where, as the carriage 33 is being raised, the contact means 38 meets a counterpart provided in the shutter structure of the labeling window of the cassette. Thus, the labeling window of the cassette can be opened and closed by moving the cassette itself by the arrangement of the invention.

The recording means 37 may be e. g. a liquid crystal dis- play, from which the desired data can be projected onto the film in a known manner by using a lamp placed behind the display. When a liquid crystal display is used, it is preferably so disposed in the labeling means structure that the display 37 can be moved as close to the film as possible for the time required for labeling, e. g. by us- ing a vertical motion of the carriage as in the solution presented in Fig. 4. In this case, it may be unnecessary to provide any separate optical devices between the dis- play and the film to ensure a successful labeling expo- sure, although a suitable lens is generally required. If a film marking technique is used that requires no move- ment of the display 37 or equivalent element, then the solution presented in Fig. 4 can naturally be further considerably simplified. In this case, an arrangement in which the display 37 or equivalent element is immovably mounted directly on the frame part 31 and in which the contact element 38 used is e. g. a solenoid will be suffi- cient.

The labeling function can naturally also be made by using previously known solutions based on a scanning technique, in which case the labeling window structure of the cas- sette does not necessarily comprise an actual shutter that can be opened/closed. In a scanning technique, the essential feature is that a printing or exposure head is moved over the labeling area of the film. When the label- ing is implemented utilizing cassette moving means ac- cording to the present application, a recording head of this type can be immovably mounted in the cassette tunnel or in its immediate vicinity and the scanning movement can be implemented as a movement of the cassette. Devices based on scanning technique generally use recording heads that expose the film in only one dimension, while another dimension of the marking is accomplished by the scanning movement itself. For example, a single-row LED display is considerably cheaper than a corresponding matrix display.

This naturally also applies to many other techniques, such as optical fibers.

The above-described opening/closing movements of the la- beling window will be unnecessary and can be omitted in solutions where a labeling window substantially imperme- able to wavelengths of visible light, and a recording element producing information that is capable of pene- trating the cassette's labeling window impermeable to visible light, or that can otherwise, e. g. in a converted form, be conveyed through it, are used.

The advantages of the arrangement of the invention are clearly visible in screening studies as mentioned above, in which it can be utilized e. g. as follows: After taking the first image, the operator of the imaging apparatus emerges from behind the radiation shield and steps in front of the apparatus, holding the next cassette ready in his hand, presses the cassette eject switch on that side where he wants the cassette to come out of the cas- sette tunnel, or removes the cassette automatically ejected by the apparatus and inserts the new cassette via the opening of the cassette tunnel, whereupon the auto- matic system of the apparatus positions the cassette in the correct position. Next, the C-arm of the device is turned into the next projection angle and, if necessary, the position of the object to be imaged is corrected, and thus the apparatus is ready to take the next image. If the apparatus is additionally provided with means for automatic labeling of the cassette according to a pre- ferred embodiment of the invention before it is driven out of the cassette tunnel, then the imaging work can be carried out considerably more effectively than before as the time spent on supplementary work associated with the imaging process is substantially reduced.

The amount of manual work to be done in connection with the arrangement of the invention can be further reduced

by adding to the cassette tunnel feed opening a cassette feed magazine operated by any known technique. The ar- rangement of the invention can even be thought of as be- ing developed as far as creating a mammography imaging line that is completely automated except for the posi- tioning of the object to be imaged. The first part of such a line could consist of a station for loading cas- settes with film, said station either simultaneously functioning as the cassette feed magazine of the mammog- raphy apparatus or being connected to a cassette feed magazine via a cassette conveyor line, from which maga- zine the cassette is fed into the cassette tunnel of the mammography apparatus, where the cassette moving means provided in the tunnel take care of the cassette move- ments needed for its positioning in connection with imag- ing, possible cassette motion and labeling during imaging and finally driving the cassette out of the cassette tun- nel, either from the same side as or from a different side than where the cassette was inserted into the tun- nel, in which case, depending on the solution, the cas- sette is conveyed either via the same aforementioned cas- sette conveyor line or via a separate line to a film de- velopment unit containing means known in themselves for automatic removal of the film from the cassette and for its development.

Besides facilitating the supplementary functions to be performed in connection with the imaging process, the arrangement of the invention can also be utilized e. g. in so-called stereotactic imaging, which involves taking at least two pictures of the same object on the same film or e. g. on a digital cassette, typically requiring the cas- sette to be moved to a new position between the expo- sures. In the arrangement of the invention, the cassette motion can be controlled e. g. by means of pre-input op- eration parameters or by operating the motor of the driv- ing roller via control buttons on the imaging apparatus.

Furthermore, the arrangement of the invention provides possibilities e. g. for taking film-based narrow-beam to- mograms with a mammography apparatus. In this type of imaging, the object to be imaged is scanned with a radia- tion beam that is narrower than the object to be imaged while the position of the radiation source and film cas- sette in relation to the stationary tissue layer or area to be imaged is changed during the imaging process, e. g. by revolving the imaging means around the object to be imaged, the film cassette being simultaneously moved in a manner required by the imaging condition known in itself so that the radiation beam also sweeps over the film dur- ing the imaging cycle.

Although the prices of digital sensors are continuously falling, especially sensors having a large surface area are still very expensive. The arrangement of the inven- tion makes it possible to use a digital sensor for taking mammographic radiographs e. g. by using a narrow sensor attached to a suitable cassette or plate, moving the sen- sor in synchronism with the scanning movement of a narrow radiation beam implemented by keeping the radiation source stationary while moving a screen placed near the radiation source to define the radiation beam.

The examples presented above are not meant to be an ex- haustive list of concrete and preferred ways of applying the invention; instead, its embodiments may vary within the scope of the inventive idea defined in the following claims.