DE102016217781A1 - Generating a coordinated representation of different mammograms in direct comparison - Google Patents

Abstract

A method for generating a matched mammography chart is described. In the method, combined image data (KBD1, KBD2) are generated in a mammography device (37). For this purpose, a first mammographic image (BD1) and a second mammographic image (BD2) are generated from the breast of a patient. Furthermore, metadata (MD1, MD2) are obtained for the first and second mammographic images (BD1, BD2). In addition, a first and a second combined image data set (KBD1, KBD2) are generated, which in each case on the respective mammography images (BD1, BD2) based different image data sets (VBD1, VBD2) and their associated metadata (MD1, MD2) include. Subsequently, the generated image data (VBD1, VBD2) are displayed simultaneously in a diagnostic station (39). For this, ideal image representation parameters (BDP1, BDP2) are determined for each of the two combined image data sets (KBD1, KBD2) on the basis of the metadata (MD1, MD2). First and second optimized image data sets (OBD1, OBD2) are generated on the basis of the calculated image display parameters (BDP1, BDP2) and the different image data (VBD1, VBD2) and the first and second optimized image data sets (OBD2) are displayed on an image display of the diagnostic station ( 39) shown simultaneously. A mammography system (30) is also described.

Description

The invention relates to a method for producing a coordinated mammography display. In addition, the invention relates to a mammography system.

Within the scope of preventive examinations and for the further diagnosis of breast cancer, mammography has been established for years as an imaging procedure. In this case, the breast is normally compressed and held in a fixed position, while mammography images, usually simple projection images, of the breast are generated with X-ray radiation.

In the case of the mammographic images, images of both breasts in the same exposure mode are the standard case. In order to enable a smooth and fast workflow in the mammography screening, the radiologist should perform as few additional actions as possible when reading the X-ray images.

Since in the vast majority of cases two related recordings are read and compared together, for example the left breast and the right breast or an older pre-recording and a current recording of the same breast, there is a problem in ensuring the same as possible image impression of the radiographs shown each other , Especially in the case of tomosynthesis, this relative representation is important since many layers are to be compared here.

Conventionally, when X-ray images are acquired on the mammography device, preset values for display on a monitor are generated. For example, the brightness and contrast (also called "center" and "width") are set. These values are selected on the basis of the image content and a kind of look-up table so that the image alone results in a neutral image impression when viewed. These functions are known as so-called "autowindowing". For tomosynthesis images, these values are calculated in parallel to the reconstruction of the layers.

If the default values for brightness and contrast at the x-ray acquisition station are determined, these are then transferred into image data in the so-called DICOM header and stored together with the actual image data and then sent to a PACS system. On the diagnostic station, these image data are read in again together with the stored preset values for brightness and contrast, and the brightness and contrast values are applied to the image data for display.

In an image comparison of, for example, right and left shot, the right and left images are loaded and displayed with their respective brightness and contrast values from the DICOM header. Since the brightness and contrast presets written to the DICOM header by the mammography device are only calculated for the single image, it often happens that when two images, such as the left and right breasts, are displayed simultaneously, the picture impression between the pictures is clearly different.

This leads to the fact that the radiologist can not find it, but first has to manually adjust the image impressions so that they are as close as possible to each other again. This interrupts his work process, is annoying and leads to fewer cases can be reported per time, which in turn reflected in the remuneration of the radiologist.

It is an object of the present invention to provide a method and corresponding mammography system for generating and displaying different mammography images with improved handling.

This object is achieved by a method for generating a coordinated mammography display according to claim 1 and by a mammography system according to claim 11.

In the method according to the invention for producing a coordinated mammography display, first of all combined image data are generated in a mammography device from the breast or chest region of a patient. In this case, for example, a first mammographic image of the left breast of the patient and a second mammogram image of the right breast of the patient are acquired. Alternatively, a first mammographic image from a breast at an earlier time and a second mammographic image from the same breast at a later time may be taken and associated with each other.

For the purposes of the present invention, acquisition of a mammographic image means, as usual, acquisition of imaging data for a diagnostic recording of a breast held in a specific position, in particular a compressed breast. These are usually projection data that can be used directly as 2D image data. In principle, but could also be easier Mammography images are recorded in the form of 2D projection image data, for example by means of a tomosynthesis method or the like. 3D mammography images.

Metadata are determined for the first and second mammographic images. Metadata should be understood as data that includes information about features of the image data of the mammographic images, but not their image data itself. More specifically, in this context, the metadata should include parameter values and indications that influence or are related to the image impression and image quality. Subsequently, on the basis of the acquired image data and the determined metadata, a first and a second combined image data set are generated, which in each case comprise metadata assigned to them in addition to different image data based on the respective mammography images. The determination of the metadata and the combination with the different image data takes place in the mammography device. Advantageously, the fact is used that such recording devices, the generation of metadata based on the mammography images and due to intermediate results in the image processing of the mammography images can be easily done. This is made possible by the considerable computing capacity of the processor of the image processing of a mammography device. This computation may take a few seconds.

The subsequent steps, which run in a diagnostic station, then benefit from the fact that the complex analysis and precalculation of metadata has already been done on the mammography device.

The generated combined image data are used in the diagnostic station to simultaneously display mammographic images. For this purpose, ideal image representation parameters for each of the two combined image data sets are determined on the basis of the metadata. Then, first and second optimized image data sets are generated based on the calculated image display parameters and the combined image data. Finally, the first and second optimized image data sets are displayed simultaneously on an image display of the diagnostic station.

The diagnostic station has special requirements for the executable algorithms with regard to their possible computing capacity and due to the fast and fluid workflow. These processes now benefit from the fact that the complex analysis of the image data has already been carried out in the mammography device. The main advantage of performing the actual optimization of the image display based on the supplied metadata only on the diagnostic station, is that only when editing the image data in the diagnostic station is known which images should be compared with each other and thus dynamically the best possible representation of the two can be calculated relative to each other to be compared with each other mammography images.

The mammography system according to the invention comprises a mammographic device for generating processed image data. The mammographic device has an acquisition unit for acquiring a first mammographic image and a second mammographic image from the chest region of a patient. As already mentioned, the two mammographic images may be a photograph of the right breast and a photograph of the left breast of a patient. However, it may also be two comparisons, taken at different times, of the same breast of a patient. Part of the mammography device is also a metadata determination unit for determining metadata about the first and the second mammographic image. The mammography apparatus further comprises an image data set generating unit for generating a first and a second combined image data set, which in each case also comprise metadata associated therewith in addition to different image data records based on the respective mammography images.

The mammography system according to the invention also comprises a diagnostic station for displaying the generated processed image data. The diagnostic station includes a parameter determination unit for calculating ideal image representation parameters for each of the two combined image data sets based on the metadata. Part of the diagnostic station is also an image data optimization unit for generating first and second optimized image data sets on the basis of the calculated ideal image representation parameters and the different image data. Furthermore, the mammography system according to the invention also comprises an image display unit for simultaneously displaying the first and the second optimized image data set on an image display of the diagnostic station.

Some essential components of the mammography system according to the invention can for the most part be designed in the form of software components. In particular, this relates to the metadata determination unit, the image data set generation unit, the parameter determination unit, and the image data optimization unit. In principle, however, these components can also be partly realized, in particular in the case of particularly fast calculations, in the form of software-supported hardware, for example FPGAs or the like. Likewise, the required interfaces, for example, if it is only about a transfer of data from other software components, be designed as software interfaces. However, they can also be configured as hardware-based interfaces, which are controlled by suitable software.

A largely software-based implementation has the advantage that even previously used mammography systems can be retrofitted in a simple way by a software update to work in the manner according to the invention. In this respect, the object is also achieved by a corresponding computer program product with a computer program which can be loaded directly into a memory device of a mammography system, distributed to the mammography device and the diagnostic station, with program sections in order to carry out all the steps of the method according to the invention when the program is executed in the mammography system becomes. Such a computer program product, in addition to the computer program optionally additional components such. For example, a documentation and / or additional components, including hardware components, such as. Hardware keys (dongles, etc.) for using the software include.

For transport to the mammography system and / or for storage on or in the mammography system, a computer-readable medium, for example a memory stick, a hard disk or other portable or permanently installed data carrier can serve, on which the computer program readable and executable by a computer unit of the mammography system are stored. The computer unit may e.g. for this purpose have one or more cooperating microprocessors or the like.

Further, particularly advantageous embodiments and modifications of the invention will become apparent from the dependent claims and the following description, wherein the independent claims of a claim category can also be developed analogous to the dependent claims and parts of another claim category and in particular also individual features of different embodiments or variants can be combined to new embodiments or variants.

In one embodiment of the method according to the invention, the metadata include brightness parameters and / or contrast parameters of the mammographic images. The aforementioned information about the brightness and the contrast of the different image data records can later be used in the determination of the image representation parameters in the diagnostic station to achieve two image representations that are as similar as possible in terms of their brightness and their contrast.

The metadata preferably includes an already processed histogram. For example, a "processed" histogram is adjusted for information that is not tissue related. There may be one or more histograms to anatomical regions within the breast, not just the entire breast (e.g., AEC (AEC = Automatic Exposure Control)) histogram and the entire histogram). The automatic exposure control (AEC) is used to monitor the dose of radiation absorbed by the patient.

In a variant of the method according to the invention, the metadata comprise information about the centroid of the histogram. In this context, the centroid should be understood as a brightness value for which there is a maximum of a number of pixels with a specific brightness. For example, image data sets with different area centroids can be matched to one another by shifting the image presentation parameters, in this case the brightness.

• – Angaben über die Fläche des Brustgewebes,
• – Angaben zu Konturen und/oder Koordinaten der Brustgewebegrenzen,
• – Angaben über die Position und Ausdehnung der Region des dichtesten Gewebes im Brustgewebe und/oder deren Intensitätswerte in der Bilddarstellung,
• – Angaben zur Position und Ausdehnung der AEC-Region.

Additionally or alternatively, the metadata may include at least one of the following:

• - information about the area of breast tissue,
• - information on contours and / or coordinates of breast tissue boundaries,
• Information about the position and extent of the region of the densest tissue in the breast tissue and / or their intensity values in the image representation,
• - Information on the location and extent of the AEC region.

Also, the above information can be used to approximate the representation of different image data sets.

In an advantageous variant of the method according to the invention, the step of calculating ideal image display parameters in the diagnostic station comprises an adjustment of the metadata of the image data sets assigned to the two different breasts and the computation of common image display parameters and display parameters which are to be applied differently to the different image data sets , By knowing both images (and the metadata for each image), the image representation parameters of both images should be calculated in such a way that they fit together best in the direct comparison.

Preferably, in the method according to the invention, the step of calculating ideal image representation parameters is based on the same image regions in the two different image data sets. In this context, "equal image areas" shall be image areas in the two different image representations which are arranged at the same image position and / or are image areas corresponding to one another structurally. Since corresponding image regions of the image representations of the different image data sets in the diagnostic station should have a comparable image impression, it is advantageous to match the calculation of the ideal image representation parameters to these mutually corresponding regions.

Additionally or alternatively, the step of calculating ideal image representation parameters may also include matching the AEC region of the two different processed image data sets.

As part of the preparation of a mammography recording a setting of recording parameters of the X-ray source of the mammography device is determined by means of a pre-recording. For this purpose, first a region with the highest tissue density is determined. Based on this, the acquisition parameters are then determined. For example, it often makes more sense not to determine the required dose or current or duration of irradiation on the basis of the complete pre-recording, but only based on specific ranges. These can be, for example, the already mentioned "AEC regions". A comparison of the two images on their basis is particularly useful, since they are then considered for the "Automatic Exposure Control". As an AEC region, for example, the region with the highest tissue density can be identified in each case, since it is particularly important here that the contrast is sufficiently good to be able to recognize details. These areas, which are already known in the pre-recording, but can also be used for the coordination of image display parameters, since there the contrast and the detail accuracy are most important and in the different images should correspond to each other in order to achieve a good comparability of the images.

In a variant of the inventive method, the image display parameters are manually readjusted by a user and the changed image presentation parameters are stored in a database to be used in a representation of the image representation parameters associated optimized image data sets and / or as part of a learning process for the presentation of other optimized image data sets to be used.

The manually adjusted image display parameters can be stored individually for each user in the database. In this way, different image presentation parameters can be used individually according to the preferences and requirements of individual users.

The invention will be explained in more detail below with reference to the accompanying figures with reference to embodiments. The same components are provided with identical reference numerals in the various figures. The figures are usually not to scale. Show it:

1 a schematic representation of an embodiment of a mammography system according to the invention,

2 a flowchart illustrating a method for generating a matched mammography representation according to an embodiment of the invention,

3 a schematic representation of a mammography system according to an embodiment of the invention.

In 1 is a mammography system 10 for two-dimensional X-ray imaging of the breast with a mammography device 11 roughly schematically illustrated. The mammography device 11 includes an X-ray source 1 , from which X-ray radiation 2 in a fan-like manner, ie in a beam which widens orthogonally to the direction of preparation, in the direction of a breast 4 is emitted. The breast 4 lies on a stage 5 on and off of a compression plate 3 pressed against the stage. In this way, the thickness of the breast is reduced in the propagation direction of the X-radiation, ie in the z-direction. With the reduction of the illuminated by the X-ray radiation object is accompanied by a reduction of the scattered radiation. Part of the chest 4 incident X-rays are absorbed. The rest of the chest 4 incident X-radiation is transmitted and from an image sensor 6 detected.

The mammography device is activated 11 with the help of a so-called "Acquisition Workstation", in which a control device 7 for the mammography device 11 is integrated. In addition to this control device 7 The Acquisition Workstation still includes a user interface that interfaces with the controller 7 is connected to make user input and / or to display images via a user interface screen.

From the controller 7 Control data is sent to the mammography device 11 to hand over, For example, for controlling the X-ray source 1 for the triggering of X-ray radiation, whereby the X-ray current, the X-ray voltage, which determines the energy of the X-ray radiation, and the duration of the X-ray radiation can be transmitted as control data. In addition, the mammography device can 11 a specific setting of a filter arrangement can be specified so that automatically the filter in front of the X-ray source 1 can be changed. This is usually done by motor. The unprocessed image data BD generated in the context of mammography are stored in the control device 7 processed. Subsequently, the processed image data VBD to a so-called PACS system 8th (PACS = Picture Archiving and Communication System). Such a system is used for archiving and making available the captured and processed image data VBD for medical professionals. From the PACS system 8th from the processed image data VBD to a diagnostic station 9 transmitted and there on a display of the diagnostic station 9 pictured.

In 2 is a flowchart 200 with which a method for generating a coordinated mammography representation according to an embodiment of the invention is illustrated. At the step 2.I be with the help of a mammography device 11 (please refer 1 ) X-ray images BD1, BD2 of a patient, which comprise a first breast intake and a second breast intake generated. This is followed by the step 2.II an image processing of the image data BD1, BD2 to be processed image data VBD1, VBD2. In the processing of the image data BD1, BD2, for example, artifact correction, filtering, noise reduction, non-linear amplification, and normalization may be performed. In this case, intermediate results ZE are generated which are used in a calculation of metadata MD1, MD2 for the image representation of the first breast or the second breast on the basis of the image data BD1, BD2 in the step 2.III be taken into account additionally.

The intermediate results ZE can include details about the administered dose, the segmentation (breast contour recognition), the location or the coordinates of specific anatomical details, intermediate results of the aforementioned processing steps, information on the AEC region, etc. The metadata MD1, MD2 may, for example, include information regarding the brightness distribution in the image data BD1, BD2 or the distribution of contrast values. Brightness values of the image data BD1, BD2 can be determined, for example, in the form of a histogram. Other metadata MD1, MD2 may include details of the contours and / or the coordinates of tissue boundaries and the area of the tissue of the breasts. The metadata MD1, MD2 may also contain information about the AEC region for which the auto-exposure system has calculated and optimized the dose during capture. At the step 2.IV become at the step 2.II generated image data VBD1, VBD2 process with those in the step 2.III generated metadata MD1, MD2 combined. At the step 2.V The combined image data KBD1, KBD2 a first and a second breast image are then stored in a PACS system.

The thus pre-processed combined image data KBD1, KBD2 are now available for inspection by a radiologist in a diagnostic station.

For review, be at the step 2.VI a first breast of the patient concerning the first combined image data KBD1 received from the PACS system and in the step 2.VII receiving a second breast of the patient related second image data KBD2 from the PACS system. The following will be at the step 2.VIII first ideal image representation parameter BDP1 for the first combined image data KBD1 and second ideal image representation parameter BDP2 for the second combined image data KBD2. For this purpose, in particular the metadata MD1, MD2 assigned to the combined image data KBD1, KBD2 are taken into account. For example, brightness values in mutually corresponding image areas of the two different breast images VBD1, VBD2 are adjusted in order to obtain an identical image impression in each case. At the step 2.IX On the basis of the first ideal image representation parameter BDP1, a first optimized breast image OBD1 of the first breast of the patient is generated and at the step 2.X Accordingly, a second optimized breast image OBD2 of the second breast of the patient is generated. Finally, at the step 2.XI a simultaneous representation of the two optimized breast images OBD1, OBD2 on a diagnostic monitor of the diagnostic station.

In 3 is a schematic representation of a mammography system 30 shown according to an embodiment of the invention. The mammography system 30 includes an acquisition unit 11 in which X-ray images comprising first and second image data BD1, BD2 from the two breasts of a patient are recorded. Part of the mammography system 30 is also a control device 37 , The control device 37 includes a metadata discovery unit 371 with which metadata MD1, MD2 are determined to the first and second mammography image BD1, BD2. An image data set processing unit 372 is also part of the controller 37 and serves the purpose of the acquisition unit 11 to prepare received image data BD1, BD2 of the left and right breasts of the patient. During the processing of the image data BD1, BD2, intermediate results ZE are generated, which are sent to the metadata determination unit 371 and to be included in the determination of metadata MD1, MD2.

The control device 37 also includes an image data set generation unit 373 , which is arranged based on the image data set processing unit 372 generated processed image data VBD1, VBD2 and the metadata detection unit 371 determined metadata MD1, MD2 combined image data KBD1, KBD2 to produce. The mammography system 30 also includes a database 8th in which the combined image data KBD1, KBD2 are stored.

It also includes the mammography system 30 a diagnostic station 39 , With the diagnostic station 39 are the combined image data KBD1, KBD2 via an input interface 391 from the database 8th read. This is then done in a parameter determination unit 392 a calculation of image display parameters BDP1, BDP2 for each of the two combined image data sets KBD1, KBD2 based on the metadata MD1, MD2 associated with the respective image data sets KBD1, KBD2. Ideal image representation parameter values BDP1, BDP2 are calculated on the basis of the metadata MD1, MD2 for the individual image recordings VBD1, VBD2, ie image representation parameter values whose application to the two processed image data sets VBD1, VBD2 produces a comparable image impression for both image data records. This is then done in an image data optimization unit 393 a generation of optimized image data sets OBD1, OBD2 on the basis of the calculated image representation parters BDP1, BDP2 and the processed image data sets VBD1, VBD2. The optimized image captures OBD1, OBD2 are finally using an image display unit 394 displayed on a diagnostic monitor.

It is finally pointed out once again that the devices and methods described in detail above are merely exemplary embodiments which can be modified by the person skilled in the art in various ways without departing from the scope of the invention. Furthermore, the use of the indefinite article "on" or "one" does not exclude that the characteristics in question may also be present multiple times. Likewise, the term "unit" does not exclude that the component in question consists of several interacting subcomponents, which may also be spatially distributed.

LIST OF REFERENCE NUMBERS

1

 X-ray source

2

 X-rays

3

 compression plate

4

 chest

5

 stage

6

 image sensor

7

 control device

8th

 PACS system / database

9

 reading station

10

 mammography system

11

 mammography unit

30

 mammography system

37

 control device

39

 reading station

371

 Metadata detection unit

372

 Image data set processing unit

373

 Image data sets generating unit

391

 Input interface

392

 Parameter determination unit

393

 Image data optimization unit

394

 Image display unit

BD

 unprocessed image data

BDP1, BDP2

 Imaging paramters

KBD1, KBD2

 combined image data

MD1, MD2

 metadata

OBD1, OBD2

 optimized breast image data

VBD, VBD1, VBD2

 processed image data

ZE

 interim results

Claims (14)

Method for generating a coordinated mammography display, comprising the steps: - generating combined image data (KBD1, KBD2) in a mammography device ( 37 comprising the steps of: - acquiring a first mammographic image (BD1) and a second mammographic image (BD2) from a patient's breast, - acquiring metadata (MD1, MD2) for the first and second mammographic image (BD1, BD2), - generating a first and a second combined image data set (KBD1, KBD2), which in each case comprise different image data sets (VBD1, VBD2) and metadata (MD1, MD2) assigned to them on the respective mammography images (BD1, BD2), - Simultaneously displaying the generated image data ( VBD1, VBD2) in a diagnostic station ( 39 ) with the steps: Calculating ideal image representation parameters (BDP1, BDP2) for each of the two combined image data sets (KBD1, KBD2) on the basis of the metadata (MD1, MD2), generating first and second optimized image data sets (OBD1, OBD2) on the basis of the calculated image representation parameters ( BDP1, BDP2) and the different image data (VBD1, VBD2), simultaneous display of the first and the second optimized image data set (OBD2) on an image display of the diagnostic station ( 39 ). The method of claim 1, wherein the first mammographic image (BD1) images the left breast of the patient and the second mammographic image (BD2) images the right breast of the patient. Method according to claim 1 or 2, wherein the metadata (MD1, MD2) comprise brightness parameters and / or contrast parameters of the mammographic images (BD1, BD2).  Method according to one of the preceding claims, wherein the metadata (MD1, MD2) comprise a preferably already processed histogram. The method of claim 4, wherein the metadata (MD1, MD2) comprises information about the centroid of the histogram. Method according to one of the preceding claims, wherein the metadata (MD1, MD2) comprise at least one of the following: - information about the area of breast tissue, - information on contours and / or coordinates of breast tissue boundaries, Information on the position and extent of the region of the densest tissue in the breast tissue and / or their intensity values, - Information on the location and extent of the AEC region. Method according to one of the preceding claims, wherein the step of calculating ideal image representation parameters (BDP1, BDP2) in the diagnostic station ( 39 ) comprises a comparison of the metadata (MD1, MD2) of the two combined image data sets (KBD1, KBD2) and the calculation of common image representation parameters (BDP1, BDP2) and of image representation parameters (BDP1, BDP2) which differ on the image data (VBD1, VBD2) the different image data sets (KBD1, KBD2) are to be applied. The method of any one of the preceding claims, wherein the step of calculating ideal image representation parameters (BDP1, BDP2) is based on the same image areas in the two different image data sets (VBD1, VBD2). The method of any one of the preceding claims, wherein the step of calculating ideal image representation parameters (BDP1, BDP2) comprises comparing the AEC region of the two different image data sets (VBD1, VBD2).  Method according to one of the preceding claims, wherein the image display parameters (BDP1, BDP2) are manually readjusted by a user and the changed image presentation parameters (BDP1, BDP2) are stored in a database in order to display the optimized images assigned to the image display parameters (BDP1, BDP2) Image data sets (OBD1, OBD2) to be used and / or used in the context of a learning process for the display of other optimized image data sets (OBD1, OBD2). The method of claim 10, wherein the manually adjusted image presentation parameters (BDP1, BDP2) are stored individually for each user in the database. Mammography system ( 30 ), comprising: - a mammography device ( 37 ) for generating combined image data (KBD1, KBD2), comprising: - an acquisition unit ( 11 ) for acquiring a first mammographic image (BD1) and a second mammographic image (BD2) from the breast of a patient, - a metadata determination unit ( 371 ) for obtaining metadata (MD1, MD2) for the first and the second mammography image (BD1, BD2), - an image data record generation unit ( 373 ) for generating a first and a second combined image data set (KBD1, KBD2), which in each case comprise different image data sets (VBD1, VBD2) and metadata (MD1, MD2) assigned to them on the respective mammography images (BD1, BD2), - a diagnostic station ( 39 ) for displaying the generated image data (VBD1, VBD2), comprising: - a parameter determination unit ( 392 ) for calculating ideal image representation parameters (BDP1, BDP2) for each of the two combined image data sets (KBD1, KBD2) on the basis of the metadata (MD1, MD2), - an image data optimization unit ( 393 ) for generating first and second optimized image data sets (OBD1, OBD2) on the basis of the calculated image display parameters (BDP1, BDP2) and the different image data (VBD1, VBD2), - an image display unit ( 394 ) for simultaneously displaying the first and second optimized image data sets (OBD1, OBD2) on an image display of the diagnostic station ( 39 ). Computer program product with a computer program, which is stored directly in a memory device of a mammography system ( 30 ) is loadable, with program sections to carry out all the steps of the method according to one of claims 1 to 11, when the computer program in the mammography system ( 30 ) is performed. A computer-readable medium having program sections which are readable and executable by a computer unit stored thereon for performing all the steps of the method according to one of claims 1 to 11 when the program sections are executed by the computer unit.

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