Method for verifying detection capability of x-ray inspection device

Abstract

The invention relates to a method for verifying the detectability of an X-ray inspection device for product types, in particular food products, in which an object is subjected to X-rays propagating through the object in an inspection zone of the X-ray inspection device. According to the invention, the object is a phantom mainly made of an artificial material and comprising at least two regions (A, B) having different propagation path lengths, the difference in the path lengths of said at least two regions (A, B) being dependent on the difference in the measured X-ray attenuation generated between the regions of a product sample of the product type simulated by the phantom, the regions correspond to the regions (A, B) of the phantom.

Description

Technical Field

[0001] The invention belongs to the field of X-ray inspection of products, in particular foods. In particular, the invention relates to a method for verifying the detection capability of an X-ray inspection device for a product type, in particular foods, wherein an object is subjected to X-rays propagating through the object in an inspection zone of the X-ray inspection device. Background Art

[0002] In the field of food quality control and / or food analysis, X-ray inspection by means of X-ray inspection equipment is well known, for example, for determining the meat and fat content of foods such as meat products. For example, US 6,597,759 B2 discloses a non-destructive analysis of a product for determining the composition of bones in a meat product by using dual-energy X-ray attenuation measurement. To this end, an X-ray radiation beam having a first and a second energy is generated, and a meat sample of any size is inserted into the beam. After the test meat sample passes through the X-ray inspection zone, the attenuation of the X-ray beams of the first and second energies is detected. Based on the previously determined photoelectric absorption index and Compton scattering values ​​corresponding to meat and bone, and the attenuation of the X-rays of the first and second energies, the ratio of the bone part to the non-bone part of the meat is derived. For calibration, a phantom with a known composition and known X-ray attenuation characteristics is used. Of course, the advantage of using a phantom for calibration rather than the meat product itself is that the calibration body does not decay and can be used for a longer time.

[0003] However, it has been demonstrated that even when using a phantom of a product sample which simulates to some extent the corresponding meat product by material selection / material composition, changes in the detection capabilities of the X-ray inspection equipment may remain undetected despite calibration at regular intervals and, in use, such equipment may allow food to pass with undetected, undesirable and possibly even dangerous bone fragments. Summary of the invention

[0004] The object of the present invention is to improve the initially mentioned method of verifying the detection capability of an X-ray inspection device, in particular in order to increase the reliability of said device in the intended application.

[0005] To this end, the invention provides a further development of such a method as described at the outset, the essential feature of which is that the object is a phantom made predominantly of artificial material and comprising at least two regions with different propagation path lengths, the difference in the path lengths of the at least two regions being correlated to the difference in measured X-ray attenuation produced between regions of a product sample of the product type simulated by the phantom, the regions corresponding to the regions of the phantom. The phantom has a height profile comprising the at least two regions, and the two regions preferably have different propagation path lengths by having different height levels.

[0006] In the framework of the present invention, it is recognized that the use of conventional phantoms for calibration or verification of detection capabilities is not sufficiently challenging for X-ray equipment, since the internal structure / composition information has been lost with respect to the original product sample. By means of the method of the present invention, said challenge is increased, so that X-ray inspection equipment, in particular X-ray inspection equipment based on X-ray transmission imaging, whose detection capabilities have been verified by the method of the present invention, can better perform its tasks, e.g. small bone fragments in poultry products, in particular in areas with high X-ray attenuation, even if bone particles are not present. Thus, based on the X-ray images generated by the X-ray inspection of the phantom, it can be determined whether the detection capabilities of the verified X-ray inspection equipment are within given set detection parameters.

[0007] The method is preferably applied to product types with a non-uniform internal structure, such as poultry meat, in particular chicken breast, but can also be applied to other meat products, food products in general, and even products outside the food field that have product types with a non-uniform internal structure.

[0008] Due to the differences in measured X-ray attenuation occurring between said respective regions of a product sample of said product type simulated by the phantom corresponding to said regions of the phantom, there may be three, four or even more regions with such different propagation path lengths. Such a plurality of regions may comprise a subset of at least two different regions, each region comprising a relative height maximum of the phantom.

[0009] In a preferred embodiment, the phantom material comprises a polymer material as a base material, however the base material is not limited thereto. It should be understood that for the above example poultry, the polymer material used should preferably have absorption characteristics similar / close to those of the main material of the product type (meaning that high energy and low energy X-rays should be absorbed in a relationship similar to, for example, the poultry). That is, preferably, the base material is a material or a mixture of materials having absorption characteristics similar / close to those of the simulated product type, and when measured against a 1 cm thick reference material, the attenuation difference is less than 20%, preferably less than 13%, and in particular less than 8%. In this regard, it is preferred that the polymer material comprises or is made of an epoxy resin, wherein a mixture of several epoxy resins may also be provided. It is also envisaged that materials comprising / consisting of PMMA may be suitable because their main elements have an effect similar to that of poultry in an X-ray image. Polymer materials such as polyethylene are conceivable, but less preferred. Furthermore, in a preferred embodiment, the material does not contain polymers comprising fluorine or chlorine, such as PTFE or PVC. In this respect, the fluorine and / or chlorine content of the base material may preferably be less than 10% by weight, in particular less than 5% by weight.

[0010] Furthermore, for example from the followingFigure 4 As can be seen in , those (at least two) regions may also be preferably located in regions where the phantom does not comprise blocks of different materials as described in the next paragraph, but instead consists of its base material.

[0011] In another preferred embodiment, the phantom locally comprises blocks of a material different from the base material, in particular blocks of calcium-containing material, preferably blocks containing calcium sulphate or calcium phosphate, in particular in areas with longer propagation path lengths. Such blocks simulating bone are therefore included in the phantom to simulate a situation which is one of the most critical situations for missed detections for X-ray inspections when natural products are being inspected, namely (in particular small / thin) bone blocks in areas which already provide high attenuation in natural products, corresponding to those areas in the phantom with long propagation paths (regardless of the propagation path length through the natural product). The areal extension transverse to the propagation direction of at least one block is preferably less than 20 mm 2 , preferably less than 13mm 2 , especially less than 10mm 2 , even less than 8mm 2 , even less than 6mm 2 In a further preferred embodiment, the lateral dimension of one or more blocks is greater than the pixel extension dimension of the detector resolution of the device by a factor in the range 2.5 to 7.5.

[0012] This aspect of the phantom simulating a bone in a local manner is also disclosed separately - with protection value. Therefore, the present invention also provides a phantom for use in a method for verifying the detection capability of an X-ray inspection device for a product type, in particular a food product, said phantom being mainly made of artificial material and locally comprising blocks of a material different from said polymer material in the form of a calcium-containing material. It should be understood that this independent aspect of the invention can also be combined with the features described above and subsequently.

[0013] Therefore, the present invention applies / includes features designed to trigger both true positive detection and false positive detection in highly non-uniform surfaces, making it challenging for X-ray transmission detection equipment to detect correct true positives.

[0014] It is further preferred that the phantom comprises a plurality of blocks of different materials, the plurality of blocks comprising in particular a first group of blocks of different dimensions in the direction of the propagation path, a second group of blocks of different dimensions and / or form in a direction transverse to the propagation path, and / or a third group of blocks of different material composition. With a plurality of such blocks of different thicknesses, a scale level is provided, which can be used to check the limits of the detection capability of a validated X-ray inspection device. In a particularly preferred embodiment, blocks of a first thickness (e.g., dimension in the direction of the propagation path) are provided, which corresponds to a first detection limit of the X-ray inspection device, with the aim that the setting parameters of the X-ray inspection device are selected such that the detection of the X-ray inspection device is no longer recognized as a criterion for sorting. It is further preferred that blocks of a second thickness correspond to the setting of the inspection device, in which setting the blocks are reliably recognized in an X-ray inspection of the phantom. There may be intermediate block thicknesses to produce a finer gradation scale, or also thicker blocks to obtain information about the level of degradation of the detection capability. The blocks are preferably arranged at least partially in positions that do not overlap with respect to the X-ray propagation.

[0015] In a preferred embodiment, the phantom part comprises a block, wherein the ratio of the propagation path length in the block to the total propagation path length is less than 7%, more preferably less than 5.6%, in particular less than 4.2%, even less than 3%. On the other hand, it is preferred that the phantom part comprises a block, wherein the ratio of the propagation path length in the block to the total propagation path length in the phantom is higher than 2.4%, more preferably higher than 3.6%, in particular higher than 4.2%, even higher than 4.8%, and is preferably thicker than the aforementioned block.

[0016] In another preferred embodiment, alternatively or additionally, similar blocks are preferably also contained in areas with lower path lengths, resulting in a ratio of less than 12%, preferably less than 10%, in particular less than 8%, and / or greater than 6%, preferably greater than 10%, in particular greater than 14%. Depending on the product type, these ranges also apply to areas with higher / highest propagation path lengths.

[0017] At least one of these blocks can be embedded in the base material so that it does not increase the thickness profile (it simply replaces the base material that was originally present). In addition, when viewed along the thickness direction, at least one of these embedded blocks can be closer to the center of the phantom than to the upper and lower surfaces of the phantom.

[0018] Other blocks, such as blocks made of metal, may be included to allow additional verification checks of the device relative to other verifications involving simple phantoms with metal markings, such as for reference purposes.

[0019] The variation in form can simulate typical bone forms that may occur in poultry products, such as fan bones, wishbones and / or ribs. In a preferred embodiment, one, some or all of the locally arranged blocks are embedded in the base material. This again better simulates the real situation faced by X-ray inspection equipment for product samples of the product type. In addition, the service life of the phantom is also increased. In addition, it is conceivable to embed the bone (fragment) simulation at different height levels, taking into account the limited focal plane of certain equipment types.

[0020] In another preferred embodiment, the shape of the entire area of ​​the product sample transverse to the propagation path is simulated by the phantom. That is, the contour of the phantom corresponds to the typical contour of the product type, while the height profile does not simulate the thickness of the product sample, but is related to the X-ray attenuation of the individual areas of the product sample. In this regard, the path length difference discussed above with respect to at least two areas is preferably applicable to the entire phantom body, so that the height profile of the phantom body is not directly related to the thickness profile of the product sample, but is directly related to the corresponding local attenuation of the product sample. In the case of optical magnification of the X-ray image, the scaling ratio in the thickness direction can be different from the scaling ratio in the plane perpendicular to the thickness direction, so that the size of the phantom in this plane is substantially kept corresponding to the size of the product sample. The resulting area difference is preferably lower than 44%, more preferably lower than 16%, in particular lower than 10% of the average area of ​​the product type.

[0021] In a preferred embodiment, the device is capable of multi-energy, in particular at least dual-energy, X-ray attenuation measurements.

[0022] Such a multi-energy, in particular dual-energy X-ray device is able to simultaneously take images at different energies, in particular images at a lower X-ray energy as well as images at a higher X-ray energy. By means of a suitable evaluation algorithm, the information from the taken multiple, respectively two images can be combined to create an image in which flesh parts are effectively eliminated, making it easier to locate paths corresponding to higher attenuation, which may be bone fragments or bone parts. Single-energy X-ray devices already have problems in detecting bone fragments in materials with uneven thickness. The evaluation algorithm may include sensitivity to the local attenuation gradient and / or the total area of ​​the higher attenuation area.

[0023] These gradients can also be seen from the following Figure 1In a preferred embodiment, the phantom has a gradient of the height profile in a first part of an axial section in the direction of its thickness, the measured value of the inclination angle being higher than π / 12, preferably higher than π / 9, or even higher than π / 6, but lower than 0.496π, preferably lower than 0.492π, in particular lower than 0.488π. In the first part or in the second part of the axial section, or in another axial section through the phantom in the direction of the phantom thickness, the measured value of the inclination angle of the gradient of the height profile may even be higher than π / 4, even higher than π / 3, or higher than 5π / 12. By avoiding vertical, but still having such a steep transition between different height levels of the phantom, the evaluation algorithm encounters the challenge of allowing a higher detection sensitivity setting. Furthermore, as one can for example see from the following Figure 4 As seen in , those gradients / transitions also appear where the phantom does not contain blocks of the above different materials but is instead composed of its base material.

[0024] This aspect of the phantom with respect to the transition gradient is also disclosed separately - with protection value. Therefore, the invention also provides a phantom for use in a method for verifying the detection capability of an X-ray inspection device for a product type, in particular a food product, said phantom being mainly made of an artificial material, wherein, with reference to the thickness direction of the phantom, the transition between two different areas of the phantom has, in an axial section through the phantom, a gradient of high profile, with an inclination angle measurement higher than π / 12, preferably higher than π / 9, even higher than π / 6, but lower than 0.496π, preferably lower than 0.492π, in particular lower than 0.488π, said gradient being related to the gradient of the measured X-ray attenuation produced between areas of a product sample of said product type simulated by the phantom, said product areas corresponding to said areas of the phantom. It will be understood that this independent aspect of the invention can also be combined with the features described above and subsequently.

[0025] Thus, X-ray inspection of the phantom produces realistic X-ray images. Several difficulties that arise in X-ray inspection of production samples are reproduced, allowing for a more reliable determination of whether the X-ray equipment is achieving the desired detection capabilities.

[0026] In a preferred application, the method is used only to verify whether the detection capability of the verified X-ray inspection device is within the given set detection parameters. In addition, this verification is also intended as a continuous repetition verification, that is, the X-ray inspection is repeated on the same X-ray inspection machine after a certain time interval. In addition, by performing the method on another X-ray inspection device, in particular of the same device type, using the same (or the same manufacturing process) phantom, the detection performance of multiple X-ray inspection devices can be compared with each other.

[0027] All these aspects may not require any results in the first place, but are only for informational purposes. However, in another aspect of the invention, it is also envisaged to adjust the settings of the X-ray inspection device based on the results of the X-ray inspection of the phantom. In a further application, the phantom can also be used as a calibration phantom.

[0028] As mentioned above, the purpose of the present invention includes enhancing the safety of X-ray inspected products. Therefore, the present invention also includes a method for X-ray inspection of products of a given product type, in particular food products, more particularly poultry products, by means of an X-ray inspection device, the X-ray inspection device being particularly configured to perform multi-energy, in particular including at least dual-energy X-ray attenuation measurements, characterized in that the X-ray inspection device is subjected to a verification method according to any of the aspects and features discussed above with respect to the given product type.

[0029] Furthermore, the present invention provides a method for manufacturing a phantom for use in a method according to any of the aforementioned aspects of the disclosed verification method, characterized in that a product sample of the product type is subjected to X-ray measurement, the corresponding locally measured X-ray attenuation is converted into a thickness profile, the thickness profile having a thickness variation associated with the corresponding X-ray attenuation variation of the product sample, and a phantom with a corresponding thickness is manufactured according to the thickness profile. That is, at least part of the X-ray optical density profile is converted into a thickness profile. Furthermore, preferably, the energy level of the X-ray image used for phantom manufacturing differs from the lower energy level of the verified dual X-ray device by less than 80%, preferably less than 60%, of the energy level difference of the device. This processing mode / sequence is different from the typical process of using a phantom, in which the required calibration phantom is created in a predetermined shape, an X-ray image is obtained from the phantom, and the machine is calibrated based on the X-ray image.

[0030] The thickness profile can be generated in a manner corresponding to the height profile of the phantom, that is to say the phantom is made by having a flat bottom side in a preferred manner. This makes the phantom easier to handle in the application. In a further preferred development of this method, the method comprises determining the average absorption coefficient by using the average thickness of the measured product sample and the average value of the transmitted X-ray intensity, and calculating the local thickness by means of the average absorption coefficient and the local intensity of the corresponding local X-ray intensity of the measured product sample, in particular for the X-ray image pixel by pixel, to obtain relative thickness differences. Thus, the height profile of the phantom corresponds to the thickness profile and has different height levels.

[0031] In this regard, in order to better simulate the product sample depending on the material used for the phantom, preferably, determining the thickness profile of the phantom includes globally scaling the relative thickness variations according to the absorption coefficient of the polymer material used as the base material of the phantom.

[0032] In another preferred method aspect, the production of the phantom comprises casting a polymer material into a mold, the mold form being created in particular on the basis of 3D printing. However, other production methods may also be used, such as 3D printing (e.g. FDM / FFF, SLS) of the phantom itself (and not just its negative image for the mold), or using subtractive production methods, such as removing material from a block of material by means such as optical (laser grinding) or mechanical (e.g. milling) means to form a 3D coordinate model. Combinations of these methods are also conceivable.

[0033] The verification method and the phantom of the invention already have advantages even without providing additional material simulating bone. Such an application may be particularly useful in the framework of X-ray inspection of pieces of meat from which the bones have previously been removed ("mechanical deboning"), since such meat still does not consist of homogeneous meat but may include inhomogeneities caused by residual elements, even if these are not bones, but also those that represent impurities, which may affect the detection capabilities of X-ray inspection equipment intended to detect unintended remaining bone material, these impurities being included when the phantom is not based on the thickness of the product sample but on an X-ray image of the product sample according to a main aspect of the invention. However, in a preferred embodiment, the phantom is provided with locally provided, in particular embedded blocks of different materials.

[0034] Insofar as a casting process is used, it is preferred in this regard to divide the casting into two or more steps and to insert one or more blocks of a different material, in particular a block of a calcium-containing material, between two casting steps.

[0035] These aspects of manufacturing a phantom are also disclosed in terms of a system. Such a system providing a method for manufacturing a phantom according to any of the preceding aspects comprises a system control unit configured to generate an X-ray image from a given product sample and to control the manufacturing of the phantom so that the thickness profile of the phantom is based on the X-ray image of the product sample. Of course, the product sample here is a real product, which may be a chicken breast or other poultry product, or other products mentioned above. In addition, the present invention provides a phantom of a product type simulating, in particular, food, for use in a verification method according to any of the preceding aspects and / or manufactured by a method according to any of the preceding aspects.

[0036] With regard to other types of food, the phantom may simulate not only one product sample, but a plurality of product samples of the same type, which are simulated in a connected arrangement, in particular at least partially overlapping in the thickness direction. Likewise, the thickness / height profile of the phantom does not reflect the thickness profile of the arrangement, but reflects / simulates the X-ray attenuation image of the arrangement. As a specific example, potato chips or French fries may form such an arrangement. Likewise, the invention may be used for food products that have a rather uniform structure in the main part but have structural defects such as embedded cavities, which result in an uneven height profile at least partially caused by the embedded cavities. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further details, features and advantages of the invention can be gathered from the following description of embodiments based on the accompanying drawings, in which:

[0038] Figure 1 The height profile of the simulated meat product is shown.

[0039] Figure 2 shows a value corresponding to Figure 1 A highly contoured phantom with additional blocks that simulate bones,

[0040] Figure 3 shows a value corresponding to Figure 1 A highly contoured phantom with additional blocks that simulate bone,

[0041] Figure 4 Shows the combination Figure 2 and Figure 3 An embodiment of

[0042] Figure 5 An X-ray inspection device is shown schematically, and

[0043] Figure 6 A flow chart of a method of making a phantom is shown. DETAILED DESCRIPTION

[0044] Figure 1 The phantom 100 shown is made of epoxy resin, and the shape of the phantom 100 is determined by the mold in which the phantom is cast. Figure 1 As can be seen in the figure, the contour of the phantom 100 simulates the contour of a typical product sample of a chicken breast product. The numbers within the outer contour of the phantom 100 are not reference numerals, but are numbers indicating the height contour of the phantom 100 relative to its bottom surface, which is a plane in this embodiment. Figure 1It can be seen that on the left, several platforms (corresponding areas) have height levels of (at least) 30 mm, 35 mm and 40 mm (area A), while on the right, several platforms have lower height levels, in this embodiment 25 mm (area B), 20 mm and 15 mm or lower. These height levels do not match the height levels / thicknesses of product samples of the product type simulated by the phantom 100, but are based on an X-ray image of such a product sample. In order to obtain the height profile, the following method is applied in this embodiment. First, an X-ray image is acquired from the selected product sample, giving the external profile and the local profile of the X-ray attenuation. By using the absorption formula I=I0·exp(-μ·d), the average formula I can be derived avg =I0·exp(-μ avg ·d avg ), where I0 is the intensity of the initial X-ray, I is the intensity of the X-ray that penetrates the product sample, and the average value refers to the average thickness of the probe (product sample) and the average value of the X-ray in the entire image. avg The relative local thickness can then be calculated pixel by pixel (for each value obtained from the X-ray image according to its scaling), thereby providing, for each pixel in the image, thickness information for the corresponding pixel area determined according to the desired resolution, which reflects the relative difference relative to the X-ray image of the product sample. The contour lines in the figure also give a sense of increasing height.

[0045] By making an X-ray measurement of the absorption coefficient of the material used to make the phantom, a global factor is derived from such known data to be multiplied by the thickness value (if applicable) so that the absolute absorption of the original image matches that of the phantom.

[0046] Thus, the height profile of phantom 100 is based on an X-ray image of a product sample and, when itself subjected to X-ray inspection, locally reproduces the X-ray image via different propagation path lengths associated with differences in measured X-ray attenuation occurring between respective regions of the product sample.

[0047] Figure 2 An embodiment similar to Figure 1 In the embodiment of the invention, however, in parts D, E and F3, the resin material is replaced by a calcium-containing material, in this embodiment gypsum, to simulate a typical bone form (BM) that may occur in this product type. In this embodiment, the BM in D simulates a wishbone, the BM in E simulates a rib, and the BM in F simulates a fan bone.

[0048] exist Figure 3In the embodiment of the invention, blocks of calcium-containing material (here made of plaster) are embedded in the phantom 300 as shown in regions A and B. These blocks simulate bone fragments or small bone pieces and are provided in two rows in region A with thickness increasing from 1.0 mm to 2.0 mm, each with an area of ​​2×2 mm. The same set of blocks of material simulating bone fragments is also present in region B. By performing an X-ray inspection on the phantom 300, it can be understood whether the detection capability is sufficient to identify these bone fragment simulations and where the detection limit of the X-ray inspection equipment lies.

[0049] For example, in the case of a dual energy X-ray inspection device 500 ( Figure 5 ), all bone fragment simulants in region B were detected, while in region A, only bone fragment simulants with a thickness of 1.5 mm and 2.0 mm were detected, and no bone fragment simulants with a thickness of 1.0 mm were detected. This may correspond to a suitable detection resolution setting of the X-ray inspection device 500. Although the setting of the image evaluation algorithm of the X-ray inspection device can theoretically be modified or improved to detect the thinnest bone fragment simulants in the region (A) with the longest propagation path length, such a setting will result in too many products being warned / possibly rejected relative to a reasonable number during X-ray inspection of real food charges of the same product type. On the other hand, if for an exemplary case, after a given time interval, the next verification method of the X-ray inspection device 500 makes it no longer possible to detect bone fragment simulants with a thickness of 1.5 mm in region A and / or bone fragment simulants with a thickness of 1.0 mm in region B, it can be concluded that the detection capability has deteriorated. By setting a suitable threshold in this way, it can also be determined when it is necessary to readjust the setting parameters of the X-ray inspection device. Furthermore, when the phantom 300 is used in a plant comprising more than one X-ray inspection apparatus, a relative comparison between the X-ray inspection apparatuses can be made based on a validation process using the phantom, for example to detect differences in their detection capabilities which may be undesirable, with the possibility of re-adjusting the detection capabilities all to the same level.

[0050] exist Figure 5In FIG. 1 , an X-ray inspection system with an X-ray inspection device 500 is shown in a schematic manner. Products P1, P2, ... Pn are transported via a known transport device 501 to pass through an inspection zone 501 of a dual-energy X-ray inspection device 500 and are analyzed by means of dual X-ray inspection in a manner known in the art. For example, a dual-energy X-ray device from Eagle (Eagle Product Inspection) can be used, as well as other X-ray inspection devices commercially available on the market. Products can be transported through the inspection zone at a rate of, for example, more than 10 pieces per minute, preferably more than 30 pieces per minute, or even more than 60 pieces per minute.

[0051] From time to time, when the X-ray inspection process is deactivated or interrupted, the X-ray inspection device 500 performs an X-ray inspection using one or more phantoms according to the present invention (e.g., one or more of the phantoms 100, 200, 300, and 400) to verify the detection capabilities of the X-ray inspection device 500 according to the explanations given above.

[0052] exist Figure 6 In step S1, a typical product sample of the product type in question is selected, for example Figure 5 In step S2, an X-ray image is generated from the product sample Pi. This can be done on a pixel basis, for example a 0.4 mm pixel size at the detector.

[0053] In step S3, the calculation as described above is performed to convert the X-ray image of step S2 into a thickness profile / height profile of the phantom. In step S4, the height profile is implemented in the form of a mold, which is created, for example, by 3D printing technology, and the mold corresponds to the negative image of the phantom. Then, it can be understood that step S4 may include smoothing the height profile on a scale corresponding to the local roughness caused by typical X-ray random noise, after which the surface shape of the height profile roughly re-corresponds to the surface shape / roughness of the product sample Pi. In step S5, a mold, such as a silicon mold, is prepared according to the height profile. In step S6, the process of casting the mold with material M (for example, epoxy resin in this embodiment) is started. In (optional) step S7, casting is interrupted, bone mimic (BM) and / or bone fragment mimic (BS) are placed in selected areas (D, E, F / A, B) on the casting material, and casting is continued afterwards so that the bone mimic / bone fragment mimic is embedded in the casting material. In the last step S8, after the casting material is fully cured, the phantom is removed from the mold. The dashed line from M to S3 indicates that material property information, here the absorption coefficient of the epoxy, is input into the calculation used to determine the global scale factor. This conversion can be performed on a pixel-by-pixel basis.

[0054] It should be understood that for some aspects, it is not necessary to replicate / simulate the exact contour form of the original product. Instead, only a portion of the X-ray image may be used, such as a portion including regions A and B, to have a simpler contour form, such as a rectangular or circular (e.g., elliptical) contour form. Alternatively, additional portions may be added to the X-ray image to obtain a simplified mold contour form, or a combination of these two variations.

[0055] Furthermore, in zone C, one can identify still different blocks of material (here stainless steel (SS)), which are spaced apart and have increasing thicknesses starting from 0.6 mm, 0.8 mm, 1.0 mm, 1.5 mm, 1.8 mm to 2.0 mm. This addition is completely optional, even if a plurality of identical bone blocks (BS) are provided in one or more zones (A, B) is only a preferred example of the present invention, which is not limited by the specific arrangement of the exemplary embodiments.

Claims

1. A method for verifying the detection capability of an X-ray inspection device (500) for a product type, in particular food, wherein: An object is subjected to X-rays propagating through the object in an inspection zone (501) of an X-ray inspection device, characterized in that the object is a phantom (100; 200; 300; 400) mainly made of artificial material and comprising at least two areas (A, B) with different propagation path lengths, the difference in the path lengths of the at least two areas (A, B) being related to the difference in measured X-ray attenuation produced between areas of a product sample of the product type simulated by the phantom, the areas corresponding to the areas (A, B) of the phantom.

2. The method according to claim 1, wherein: The mimetic material comprises as a base material a material or a material mixture, in particular a polymer material (M), which has absorption properties similar / close to those of the type of product being simulated.

3. The method according to claim 2, wherein: The phantom partially comprises blocks of a material different from the polymer material (BS; BM), in particular blocks of a calcium-containing material, in particular in regions with longer propagation path lengths.

4. The method according to claim 3, wherein: The phantom comprises a plurality of blocks (BS) of different materials, the plurality of blocks particularly comprising a first group of blocks having different sizes in the direction of the propagation path, a second group of blocks having different sizes and / or forms in a direction transverse to the propagation path, and / or a third group of blocks having different material compositions.

5. The method according to claim 3 or 4, wherein: At least a portion of the locally arranged blocks is embedded in a base material.

6. A method according to any one of the preceding claims, wherein: The X-ray inspection apparatus is configured to perform multi-energy, in particular at least dual-energy, X-ray attenuation measurements.

7. A method according to any one of the preceding claims, wherein: The overall area shape of the product sample transverse to the propagation path is simulated by the phantom.

8. A method according to any one of the preceding claims, wherein: After a certain period of time, the X-ray examination is repeated on the same X-ray examination machine and / or the method is additionally carried out for another X-ray examination apparatus, in particular of the same apparatus type, using the same phantom.

9. A method according to any one of the preceding claims, wherein: The settings of the X-ray inspection equipment are adjusted based on the results of the X-ray inspection of the phantom.

10. A method for X-ray inspection of products of a given product type, in particular food, by means of an X-ray inspection device, the X-ray inspection device being in particular configured to perform multi-energy, in particular including at least dual-energy X-ray attenuation measurements, It is characterized in that For the given product type, the X-ray inspection device is subjected to a verification method according to any one of the preceding claims.

11. A method for manufacturing a phantom for use in the method according to any one of claims 1 to 9, characterized in that: X-ray measurements are performed on product samples of the product type, corresponding locally measured X-ray attenuation is converted into a thickness profile having thickness variations associated with corresponding X-ray attenuation variations of the product sample, and a phantom having a corresponding thickness is manufactured according to the thickness profile.

12. The method according to claim 11 comprises determining an average absorption coefficient by using the average thickness of the measured product sample and the average value of the transmitted X-ray intensity, and calculating the local thickness by means of the average absorption coefficient and the local intensity of the corresponding local X-ray intensity of the measured product sample, in particular calculating pixel by pixel for the X-ray image to obtain the relative thickness difference.

13. The method according to claim 12, wherein: Determining the thickness profile of the phantom comprises a global scaling of the relative thickness variations according to the absorption coefficient of the material or material mixture, in particular a polymer material, used as the base material of the phantom.

14. The method according to any one of claims 11 to 13, wherein: The production of the phantom comprises casting a material or a material mixture, in particular a polymer material, into a mold, the mold form being created in particular on the basis of 3D printing.

15. The method according to claim 14, wherein: The casting is divided into two or more steps and between two casting steps one or more blocks of a different material, in particular a block of a calcium-containing material, are inserted.

16. A phantom which simulates a product type, in particular a food product, in a authentication method according to any one of claims 1 to 9 and / or which is produced by a method according to any one of claims 7 to 15.

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