Method for verifying detection ability of X-ray apparatus

Abstract

The present invention relates to a method for verifying the detection capabilities of an X-ray inspection device, particularly with respect to food product types, wherein an object is exposed 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 formed of artificial material and comprising at least two regions (A, B) having different propagation path lengths, the difference in their path lengths being correlated with the measured difference in X-ray attenuation occurring between regions of a product sample of the product type mimicked by the phantom, and those regions corresponding to the said regions (A, B) of the phantom.

Description

【Technical Field】 【0001】 The present invention relates to the field of X-ray inspection of products, in particular food products. In particular, the present invention relates to a method for verifying the detection ability of an X-ray inspection apparatus, in which an object is exposed to X-rays propagating through the object in an inspection zone of the X-ray inspection apparatus, particularly for a food product type. 【Background Art】 【0002】 X-ray inspection by X-ray inspection apparatuses is widely known in the field of food quality control and / or food analysis, for example, to determine the meat and fat content of food products such as meat products. For example, U.S. Patent No. 6,597,759 discloses a non-destructive analysis of a product by using dual-energy X-ray attenuation measurements for determining the bone composition in a meat product. For that purpose, a beam of X-ray radiation 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 has passed through the X-ray inspection zone, the attenuation of the X-ray beam at the first and second energies is detected. From the pre-determined photoelectric absorption indices as well as the Compton scattering values corresponding to meat and bone, and the attenuation of the X-rays at the first and second energies, the ratio of the bone and non-bone parts of the meat is estimated. For calibration, a phantom having known composition and known X-ray attenuation characteristics is used. The advantage of using a phantom instead of the meat product itself for calibration purposes is, of course, having a non-perishable calibration object that can be used over a longer period of time. 【0003】 However, even when using a phantom that mimics the product samples of each meat product in some way by material selection / material composition, changes in the detection ability of the X-ray inspection apparatus may remain undetected despite calibration at regular time intervals, and it has been found that such an apparatus may pass food products having undetected, undesirable, and perhaps even dangerous bone fragments during use. 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 An object of the present invention is to improve a method for verifying the detection ability of an X-ray inspection apparatus as described first, for the purpose of higher reliability of the apparatus in a particularly intended use. 【Means for Solving the Problems】 【0005】 For this purpose, the present invention provides a further development of such a method as initially presented, characterized in that the object is a phantom mainly formed of artificial materials and including at least two regions having different propagation path lengths, the difference in their path lengths correlating with the measured difference in X-ray attenuation occurring between regions of a product sample of the product type mimicked by the phantom, and those regions corresponding to the regions of the phantom. The phantom has a height profile including 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 invention, it has been recognized that using a conventional phantom for calibration or verifying the detection ability is not a sufficient challenge for an X-ray apparatus because internal structure / composition information is lost regarding the original product sample. By the method of the present invention, the problems are increased such that an X-ray inspection apparatus having those detection abilities verified by the method of the present invention, particularly based on X-ray transmission imaging, works better for those tasks, for example, detecting small bone fragments in chicken products in a region with high X-ray attenuation when there are no bone particles. Therefore, based on the X-ray image generated by X-ray inspection of the phantom, it can be determined whether the detection ability of the verified X-ray inspection apparatus is within given set detection parameters. 【0007】 The method is preferably applied to product types having a non-uniform internal structure, such as chicken, especially chicken breast meat, but can also be applied to other meat products, generally to foods, and even to common and uniform products outside the field of foods having a non-uniform internal structure of the product type. 【0008】 By virtue of the agreement with the measured difference in X-ray attenuation occurring between the respective regions of the product sample of the product type mimicked by the phantom corresponding to the region of the phantom, a plurality of three, four or even more regions having such different propagation path lengths can exist. Such a plurality of regions can include a subset of at least two distinct regions each containing the relative maximum height of the phantom. 【0009】 In a preferred embodiment, the phantom material includes a polymer material as a base material, but the base material is not limited thereto. It should be understood that the polymer material used should preferably have absorption characteristics similar / close to those of the product type, the main material of chicken in the above example (high-energy and low-energy X-rays should be absorbed, for example, in a relationship similar to that of the chicken). That is, preferably, the base material is a material or a material mixture having absorption characteristics similar / close to those of the mimicked product type by being different by less than 20%, preferably less than 13%, especially less than 8% in attenuation when measured for a reference material with a thickness of 1 cm. In this regard, the polymer material preferably contains or is formed from an epoxy resin, and a blend of a plurality of epoxy resins can also be provided. It is also conceivable that a material containing / consisting of PMMA can be appropriate, because their main elements have an effect similar to that of chicken in an X-ray image. Polymer materials such as polyethylene are conceivable but less preferred. Furthermore, in a preferred embodiment, polymers containing fluorine or chlorine, such as PTFE or PVC, are not included in the material. In this regard, the fluorine and / or chlorine content in the base material may preferably be less than 10% by mass, especially less than 5% by mass. 【0010】 Furthermore, as can be seen from FIG. 4 below, for example, these (at least two) regions can be localized, preferably where the phantom does not contain pieces of different materials to be described in the following paragraphs, even in terms of being composed of the base material. 【0011】 In a further preferred embodiment, the phantom locally contains pieces of a material different from the base material, particularly a calcium-containing material, preferably calcium sulfate or calcium phosphate, particularly in regions having a particularly longer extension path length. Thus, such pieces mimicking bone are among the most important cases where they pass through undetected by X-ray examination when occurring for the natural product being inspected, i.e., particularly for mimicking (particularly small / thin) bone fragments in regions that already provide a high attenuation in the natural product, and this region (regardless of the propagation path length through the natural product) corresponds to those in the phantom having a long propagation path. The lateral region extension with respect to the propagation direction of at least one piece is preferably less than 20 mm 2 less, preferably less than 13 mm 2 less, particularly less than 10 mm 2 less, further less than 8 mm 2 less, further less than 6 mm 2 less. In a further preferred embodiment, the lateral dimension of one or more pieces is larger than the pixel extension of the detector resolution of the device by a factor in the range of 2.5 to 7.5. 【0012】 This aspect of the phantom for mimicking bone in a localized form is also disclosed independently as being of protective value. Thus, the invention provides a phantom for use particularly in a method of verifying the detection ability of an X-ray inspection device with respect to a food product type, the phantom being mainly formed from an artificial material and locally containing pieces of a material different from the polymeric material in the form of a calcium-containing material. It is understood that this independent aspect of the invention can also be provided in combination with the features described above and below. 【0013】 Accordingly, the invention applies / includes features designed to trigger true positive and false positive detections on a very non-uniform surface, whereby the X-ray transmission detection device is challenged to detect correct true positives. 【0014】 More preferably, the phantom includes pieces of a plurality of different materials, the plurality particularly including a first group of pieces whose dimensions vary in the propagation path direction, a second group of pieces whose dimensions and / or morphology vary in a direction transverse to the propagation path direction, and / or a third group of pieces whose material composition varies. By having, for example, a plurality of such pieces with different thicknesses, a scaling grade is provided that can be used to check the limits of the detection capabilities of the X-ray inspection device to be verified. In a particularly preferred embodiment, there is provided a piece having a first thickness (e.g., a dimension in the propagation path direction) corresponding to a first detection limit of the X-ray inspection device, with the aim that the settings of the X-ray inspection device are selected such that it no longer recognizes its detection as a criterion for classification. Even more preferably, there is a piece having a second thickness corresponding to the settings of the inspection device, in which case the piece is reliably recognized in the X-ray inspection of the phantom. Intermediate piece thicknesses can also be present for generating a finer scale of the scale, or thicker pieces for obtaining information about the grade of deterioration of the detection capabilities. These pieces are preferably arranged at least partially in positions that do not overlap with respect to X-ray propagation. 【0015】 In a preferred embodiment, the phantom locally includes such pieces having a ratio of the propagation path length of the piece to the overall propagation path length of less than 7%, more preferably less than 5.6%, particularly less than 4.2%, and even more preferably less than 3%. On the other hand, the phantom preferably includes such pieces having a ratio of the propagation path length in the piece to the overall propagation path length in the phantom that is higher than 2.4%, more preferably higher than 3.6%, particularly higher than 4.2%, and even more preferably higher than 4.8%, and preferably thicker than the pieces mentioned previously. 【0016】 In a further preferred embodiment, alternatively or additionally, similar pieces are also preferably included in regions having a lower path length, leading to a ratio of less than 12%, preferably less than 10%, particularly less than 8%, and / or higher than 6%, preferably higher than 10%, particularly higher than 14%. These ranges may also apply to regions having the higher / highest propagation path length, depending on the product type. 【0017】 At least one of such pieces may be embedded in the substrate, which does not lead to an increase in the thickness profile (the piece only replaces the substrate that would otherwise be present). Further, at least one of such embedded pieces may be closer to the center than the upper and lower surfaces of the phantom when viewed along the thickness direction. 【0018】 For other validations, for example for additional validation checks for the device with respect to other validations including a simple phantom having a metal tag for reference purposes, other pieces can be included, for example made of metal. 【0019】 The shape variations can mimic typical bone shapes that can occur in poultry products, such as for example fan bones, wishbones, and / or rib bones. In a preferred embodiment, one, several or all of the locally arranged pieces are embedded in the substrate. This again better mimics the true situation of the product sample presented to the X-ray inspection device with respect to said product type. Further, the duration of the phantom is increased. Further, considering the defined focal planes of some device types, the bone (fragments) are considered to be embedded at different height levels. 【0020】 In a further preferred embodiment, the overall area shape of the product sample transverse to the propagation path is mimicked by a phantom. That is, while the contour of the phantom corresponds to the typical contour of the product type, the height profile does not mimic the thickness of the product sample but is related to the X-ray attenuation of the various regions of the product sample. In this regard, the path length differences described above for at least two regions are preferably applied to an overall phantom object having a height profile that does not directly correlate with the thickness profile of the product sample but does directly correlate with the respective local attenuation of the product sample. In the case of optical magnification of the X-ray image, the scaling in the thickness direction may be different from the scaling in a plane orthogonal to the thickness direction, and in this plane, the size of the phantom may be maintained substantially corresponding to the size of the product sample. The resulting area difference is preferably less than 44%, more preferably less than 16%, and particularly less than 10% of the average area of the product type. 【0021】 In a preferred embodiment, the apparatus is capable of performing multi-energy X-ray attenuation measurements, particularly including at least dual-energy X-ray attenuation measurements. 【0022】 Such multi-energy, particularly dual-energy X-ray devices can simultaneously acquire images at different energies, such as an image at a lower X-ray energy and an image at a higher X-ray energy. With an appropriate evaluation algorithm, the information from both of the acquired multi-images can be combined to generate an image that effectively excludes the soft tissue portion for easier localization of the path corresponding to the higher attenuation, which is likely to be a bone fragment or a bone portion. Single-energy X-ray devices already have problems in detecting bone fragments in materials having non-uniform thickness anyway. The evaluation algorithm may include being sensitive to the local gradient of attenuation and / or the overall area of the higher attenuation region. 【0023】 Regarding these gradients, in a preferred embodiment, hereinafter, so as to also be obtainable from the contour lines (isohypse) of FIG. 1, the phantom, with respect to its thickness direction, in the first part of its axial section, has a gradient in the height profile measured as an inclination angle that is higher than π / 12, preferably higher than π / 9, and more preferably higher than π / 6, but lower than 0.496π, preferably lower than 0.492π, and particularly lower than 0.488π. In the first part or the second part of the axial section of the phantom or in a further axial section with respect to the thickness direction, there is a gradient in the height profile measured as an inclination angle that can be even higher than π / 4, even higher than π / 3, or even higher than 5π / 12. Avoiding perpendicularity, by further having such a cliffy transition between different height levels of the phantom, the evaluation algorithm faces the problem of allowing a higher detection sensitivity setup. Further, for example, as can be seen hereinafter from FIG. 4, these gradients / hereinafter also appear where the phantom consists of its base material without including pieces of different materials as described above. 【0024】 This aspect of the phantom regarding the gradient of the transition is also independently disclosed as being of protective value. Thus, the invention also provides a phantom for use in a method of verifying the detection ability of an X-ray inspection device, particularly with respect to food product types, the phantom being mainly formed from artificial materials, and the transition between two separate regions of the phantom, with respect to its thickness direction, in the axial section of the phantom, has a gradient in the height profile measured as an inclination angle that is higher than π / 12, preferably higher than π / 9, and more preferably higher than π / 6, but lower than 0.496π, preferably lower than 0.492, and particularly lower than 0.488π, and the gradient correlates with the measured X-ray attenuation gradient occurring between regions of a product sample of the product type mimicked by the phantom, and the product regions correspond to the regions of the phantom. It should be understood that this independent aspect of the invention can also be provided in combination with the features described above and the features described hereinafter. 【0025】 Thus, the X-ray inspection of the phantom generates realistic X-ray images. Some of the difficulties occurring in the X-ray detection of product samples are reconstructed, enabling a more reliable determination of whether the X-ray device achieves the desired detection capabilities. 【0026】 In a preferred application, the method is used only for the purpose of verifying whether the detection capabilities of the X-ray inspection device to be verified are within a given range of set detection parameters. Further, such verification is also intended as an ongoing repeated verification, i.e., the X-ray inspection is repeated on the same X-ray machine at regular time intervals. Further, the detection performances of multiple X-ray inspection devices can be compared with each other by performing the method using the same (or identically manufactured) phantom in another X-ray inspection device of the same device type. 【0027】 All of these aspects may not require any results initially and may serve for information purposes. However, in a further aspect of the invention, it is also conceivable that the settings of the X-ray inspection device are adjusted depending on the results of the X-ray inspection of the phantom. In a further application aspect, the phantom may also be used as a calibration phantom. 【0028】 As initially stated, the object of the invention includes enhancing the safety aspects regarding the products to be X-ray inspected. Thus, the invention features that the X-ray inspection device is exposed to a verification method according to any of the aspects and features described above with respect to the given product type, in particular an X-ray inspection device configured to perform at least dual-energy X-ray attenuation measurements, in particular multiple energies, and also includes a method for X-ray inspection of products of a given product type, in particular food products, more specifically chicken products. 【0029】 Furthermore, the invention provides a method of manufacturing a phantom for use in a method according to any of the preceding aspects of the disclosed verification method, characterized in that X-ray measurements are made on a product sample of the product type, and each locally measured X-ray attenuation is converted into a thickness profile having a thickness change correlated with the respective X-ray attenuation change of the product sample, and a phantom having a thickness dependent on the thickness profile is manufactured. That is, at least partially, the X-ray optical density profile is converted into a thickness profile. Further, it is preferred that the energy level used for the X-ray image for phantom manufacturing differs from the lower energy level of the dual X-ray apparatus being verified by less than 80%, preferably less than 60%, of the energy level difference of the apparatus. The method / sequence of this procedure is different from the typical procedure of using a phantom in which the required calibration phantom is formed in a predetermined shape, an X-ray image is acquired from the phantom, and the machine is calibrated based on this X-ray image. 【0030】 The thickness profile can be generated such that the phantom is formed to have a flat bottom side in a preferred form, i.e., so as to correspond to the height profile of the phantom. This facilitates handling the phantom in an application. In a further preferred development of such a method, the method determines an average absorption coefficient by the average use over the average thickness of the measured product sample and the intensity of the transmitted X-rays, and calculates the local thickness, in particular for each pixel with respect to the X-ray image, by the local intensity of the average absorption coefficient and the corresponding local X-ray intensity of the measured product sample. Thus, the height profile of the phantom then corresponds to the thickness profile and has different height levels. 【0031】 In this regard, in order to better mimic the product sample depending on the material used for the phantom, the determination of the thickness profile for the phantom is provided in a preferred form that involves a global scaling of the relative thickness change depending on the absorption coefficient of the polymeric material used as the base material for the phantom. 【0032】 In a further preferred method aspect, the production of the phantom involves injecting a polymeric material into a mold, the mold shape being generated in particular based on 3D printing. However, other manufacturing methods can be used, such as 3D printing of the phantom itself (not only its negative for the mold), for example FDM / FFF, SLS, or defective methods such as material removal by optical (laser ablation) or mechanical (e.g., milling) means from a material block starting, for example, to a 3D coordinate system model. Combinations of these methods are also conceivable. 【0033】 The verification method and phantom of the present invention already have advantages even if no additional material mimicking bone is provided. Such an application can be useful in particular in the framework of X-ray examination of meat slices where the bone has been previously removed ("mechanical boning"). Because such meat may still not consist of uniform meat but may contain inhomogeneities due to residual elements even if not bone, and these residues represent impurities that have an effect on the detection ability of an X-ray examination device aimed at detecting unintended residual bone material, and such impurities are included according to the main aspect of the present invention when the phantom is based on the X-ray image of the product sample rather than on the thickness of the product sample. 【0034】 From the perspective of using a casting process, in this regard, it is preferred that the casting is divided into two or more steps and one or more pieces of different materials, and in particular that a calcium-containing material is inserted between two casting steps. 【0035】 These aspects of manufacturing the phantom are also disclosed in terms of system aspects. Such a system for providing a method of manufacturing a phantom according to any of the preceding aspects includes a system control configured to generate an X-ray image from a given product sample and to control the manufacture of the phantom, whereby the thickness profile of the phantom is based on the X-ray image of the product sample. Here, of course, the product sample can be a true product which can be chicken breast meat or other chicken meat products, or other products as described above. Further, the present invention provides a phantom that mimics a food product type for a verification method according to any of the aspects described previously and / or is manufactured by a method according to any of the aspects described previously. 【0036】 With respect to other types of food items, the phantom can mimic not only one product sample, but also multiple product samples of the same type that are mimicked in a connected arrangement that at least partially overlaps, particularly in the thickness direction. Again, 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, hash browns or French fries can form such an arrangement. The invention can also be used for food items that are mostly of a fairly uniform structure but have structural defects such as embedded cavities, such embedded cavities resulting in a non-uniform height profile that at least partially originates from the embedded cavities. 【0037】 Further details, features and advantages of the invention can be obtained from the subsequent description of the embodiments based on the drawings. 【Brief Description of the Drawings】 【0038】 【Figure 1】 It is a figure showing the height profile of a phantom which mimics a meat product. 【Figure 2】A diagram showing a phantom having a height profile corresponding to the height profile of FIG. 1 and having additional pieces imitating bones. 【Figure 3】 A diagram showing a phantom having a height profile corresponding to the height profile of FIG. 1 and having additional pieces imitating bone fragments. 【Figure 4】 A diagram showing an embodiment combining FIGS. 2 and 3. 【Figure 5】 A diagram showing an X-ray inspection apparatus in a schematic form. 【Figure 6】 A flowchart of a method for manufacturing a phantom. 【DETAILED DESCRIPTION OF THE INVENTION】 【0039】 The phantom shown in FIG. 1 is formed from an epoxy resin, and the shape of the phantom 100 is determined by the mold in which the phantom is molded. It can be recognized from FIG. 1 that the contour of the phantom 100 imitates the contour of a typical product sample of a chicken breast product. The numbers within the outer contour of the phantom are not reference numbers, but rather the numbers indicate the height profile of the phantom 100 with respect to the bottom surface that is flat in the embodiment of the subject matter. From FIG. 1, for example, in the left portion, several elevated platforms (region A) having height levels of (at least) 30 mm, 35 mm, and 40 mm are recognized, while on the right side, in this embodiment, there are several elevated platforms having lower height levels of 25 mm (region B), 20 mm, and 15 mm and below. These height levels do not match the height levels / thicknesses of the product samples of the product type mimicked by the phantom 100, but are based on the X-ray images of such product samples. To obtain the height profile, the following method was applied in the embodiment of the subject matter. First, an X-ray image was acquired from a selected product sample, giving the outer contour and the local distribution of X-ray attenuation. By using the absorption formula I = I0·exp(-μ·d), the average formula I avg = I0·exp(-μ avg ·d avg) can be derived, where I0 is the intensity of the initial X-ray, I is the intensity of the X-ray transmitted through the product sample, and average refers to the average thickness of the probe (product sample) and the average of the X-rays in the overall image. From this, μ established therefrom avg Having avg , the relative local thickness can be determined for each pixel (for all values obtained from the X-ray image according to the scaling of the X-ray image), thereby reaching, for each pixel in the image, thickness information that reflects the relative difference regarding the X-ray image of the product sample for the area of the pixel according to the respective desired resolution. The contour lines in the drawing also give an impression of the gradient of the height increase. 【0040】 By X-ray measurement of the absorption coefficient of the material used to manufacture the phantom, respectively, from such known data respectively, a global factor by which the thickness value is multiplied if applied, whereby the absolute absorption of the original image matches the absorption of the phantom. 【0041】 Therefore, the height profile of the phantom 100, based on the X-ray image of the product sample, correlates with the measured difference in X-ray attenuation that occurs between the respective corresponding regions of the product sample, and as a result, through the different propagation path lengths that occur, when itself undergoing X-ray inspection, locally reproduces the X-ray image. 【0042】 The embodiment of FIG. 2 is similar to that of FIG. 1, but in parts D, E, and F3, the resin material has been replaced with a calcium-containing material, in this embodiment gypsum, in order to mimic the typical form of bone (BM) that can appear in such product types. In this embodiment, the BM in D mimics the wishbone, the MBM in E mimics the rib, and the BM in F mimics the fan bone. 【0043】 In the embodiment of FIG. 3, here pieces of the calcium-containing material formed from plaster are embedded in the phantom 300 as shown in regions A and B. These pieces mimic bone fragments or small bone chips and are provided with respective areas of 2×2 mm in two rows having thicknesses increasing from 1.0 mm to 2.0 mm in region A. The same set of bone fragments mimicking the material pieces is present in region B. From the X-ray examination of the phantom 300, it is recognized whether the detection ability is sufficient to identify these bone fragment mimics where they respectively reach the detection limit of the X-ray examination apparatus. 【0044】 For example, in an exemplary measurement obtained by, for example, a dual-energy X-ray inspection device 500 (FIG. 5), all bone fragment mimics in region B were detected, but in region A, only those having thicknesses of 1.5 mm and 2.0 mm were detected, and those having a thickness of 1.0 mm were not detected. This can correspond to an appropriate detection resolution setting for the X-ray inspection device 500. The setting for the image evaluation algorithm of the X-ray inspection device can be theoretically modified or improved to also detect the thinnest bone fragment mimics in the region (A) with the longest propagation path length, but such a setting leads to alerts / possible rejections for products that are too numerous with respect to the positive number during the use of the actual food charge of the same product type during X-ray inspection. On the other hand, for exemplary situations, the next verification method of the X-ray inspection device 500 after a given time interval can conclude a deterioration in detection ability, for example, if the 1.5-mm thick bone fragment mimics in region A and / or the 1.0-mm thick bone fragment mimics in region B are no longer detected. By thus setting an appropriate threshold, it is also possible to determine when readjustment of the setting parameters of the X-ray inspection device is required. Further, when using the phantom 300 in a plant including two or more X-ray inspection devices, a relative comparison between them can be made based on the verification process using the phantom in order to detect differences in their detection abilities, which may be undesirable, and for purposes such as having the possibility of readjusting all detection abilities to the same level. 【0045】 In FIG. 5, an X-ray inspection system including an X-ray inspection apparatus 500 is shown in a schematic form. Products P1, P2,... Pn are conveyed by a known conveying device 501 so as to pass through an inspection zone 501 of the dual-energy X-ray inspection apparatus 500 and are analyzed by dual X-ray inspection in a form known in the technical field. For example, an Eagle dual-energy X-ray apparatus (Eagle Product Inspection) can be used, and other X-ray inspection apparatuses are also commercially available. The products can be conveyed through the inspection zone at a speed of, for example, more than 10 pieces per minute, preferably more than 30 pieces per minute, and further preferably more than 60 pieces per minute. 【0046】 Sometimes, when the X-ray inspection process is stopped or interrupted, the X-ray inspection apparatus 500 performs X-ray inspection using one or more phantoms according to the present invention, for example, one or more of phantoms 100, 200, 300, and 400, in order to verify the detection ability of the X-ray inspection apparatus 500 according to the description provided above. 【0047】 In the flowchart of FIG. 6, a preferred method for manufacturing a phantom according to the present invention is provided. In step S1, a typical product sample of the problematic product type, for example, product Pi in FIG. 5, is selected. In step S2, an X-ray image is generated from the product sample Pi, which can be performed on a pixel basis, for example, with a pixel size of 0.4 mm in a detector. 【0048】 In step S3, in order to convert the X-ray image of step S2 into a thickness profile / height profile for the phantom, the calculations as described above are performed. In step S4, the height profile is implemented in the shape of a mold formed, for example, by 3D printing technology, and the mold corresponds to the negative of the phantom shape. Then, step S4 may include smoothing of the height profile at a scale corresponding to local roughness by typical X-ray random noise, and it should be understood that the surface shape of the height profile then substantially corresponds to the surface shape / roughness of the product sample Pi. In step S5, for example, a silicon mold is prepared according to the height profile. In step S6, a molding process for the mold is started using the material M, in this embodiment, for example, an epoxy resin. In (optional) step S7, the molding is interrupted, and a bone mimetic (BM) and / or a bone fragment mimetic (BS) are placed on the molding material in the selected zones (D, E, F / A, B), and then the molding is continued, for example, to embed the bone / bone fragment mimetic into the molding material. In the last step S8, after the molding material is sufficiently solidified, the phantom is removed from the mold. The dotted line from M to S3 indicates that the material property information, here the absorption coefficient of the epoxy resin, is input into the calculation to determine the global scaling factor. The conversion can be performed at the per-pixel level. 【0049】 It should be understood that for some embodiments, it is not necessary to reproduce / mimic the exact contour shape of the main product. As an alternative, only a part of the X-ray image, for example, only the part including regions A and B, can be used in order to have a simpler contour shape, for example, a rectangular or circular, for example, an elliptical contour shape. Additionally, additional parts can be added to the X-ray image, or a combination of both variations can be possible, such as to arrive at a simplified contour shape for the mold. 【0050】 Furthermore, in region C, further different materials having an increased thickness starting at 0.6 mm, spaced apart, exceeding 0.8 mm, 1.0 mm, 1.5 mm, and up to 2.0 mm are recognized, where in this case pieces of stainless steel (SS) are recognized. Such an addition is purely optional and is only a preferred example of the invention which is not limited by the particular arrangement of the exemplary embodiments, even by the provision of some identical bone fragments (BS) in one or more regions (A, B).

Claims

[Claim 1] A method for verifying the detection capability of an X-ray inspection apparatus (500) particularly with respect to a food product type, wherein an object is exposed to X-rays propagating through the object in an inspection zone (501) of the X-ray inspection apparatus, wherein the object is a phantom (100; 200; 300; 400) formed mainly from an artificial material and comprising at least two regions (A, B) having different propagation path lengths, wherein the difference in the path lengths of the propagation paths correlates with a measured difference in X-ray attenuation occurring between regions of a product sample of the product type mimicked by the phantom, and the regions correspond to the regions (A, B) of the phantom. [Claim 2] The method according to claim 1, wherein the phantom material comprises a material or mixture of materials having absorption properties similar to or close to those of the product type being imitated, in particular a polymer material (M) as a substrate. [Claim 3] The method according to claim 2, wherein the phantom locally comprises pieces of a material different from the polymer material, particularly calcium-containing material (BS; BM), especially in regions having longer propagation path lengths. [Claim 4] The method according to claim 3, wherein the phantom comprises a plurality of pieces (BS) of different materials, the plurality particularly comprising a first group of pieces whose dimensions change in the propagation path direction, a second group of pieces whose dimensions and / or shape change laterally with respect to the propagation path direction, and / or a third group of pieces whose material composition changes. [Claim 5] The method according to claim 3, wherein at least a portion of the locally placed pieces is embedded in the substrate. [Claim 6] The method according to claim 1, wherein the X-ray inspection apparatus is configured to perform a multiple energy attenuation measurement, in particular including at least a dual energy X-ray attenuation measurement. [Claim 7] The method according to claim 1, wherein the overall area shape of the product sample in the direction lateral to the propagation path is mimicked by the phantom. [Claim 8] The method according to claim 1, wherein the X-ray inspection is repeated in the same X-ray inspection machine after a time interval and / or using the same phantom, and such a method is additionally performed for another X-ray inspection apparatus of the same apparatus type. [Claim 9] The method according to claim 1, wherein the settings of the X-ray inspection apparatus are adjusted depending on the results of the X-ray inspection of the phantom. [Claim 10] In a method of X-ray inspection of a given product type, particularly food, using an X-ray inspection apparatus specifically configured to perform multi-energy X-ray attenuation measurements, including at least dual-energy X-ray attenuation measurements, The X-ray inspection apparatus is characterized by undergoing the verification method described in any one of claims 1 to 9 with respect to the given product type. [Claim 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 a product sample of the product type, the locally measured X-ray attenuations of each product sample are converted into a thickness profile having a thickness change correlated with the respective X-ray attenuation changes of the product sample, and a phantom having a thickness dependent on the thickness profile is manufactured. [Claim 12] The method according to claim 11, comprising determining an average absorption coefficient by using an average over the average thickness of a measured product sample and the intensity of transmitted X-rays, and calculating a local thickness in particular on a pixel-by-pixel basis with respect to the average absorption coefficient and the local intensity of the corresponding local X-ray intensity of the measured product sample in order to obtain a relative thickness difference. [Claim 13] The method according to claim 12, wherein the determination of the thickness profile for the phantom involves a global scaling of the relative thickness change depending on the absorption coefficient of the material or material mixture, in particular the polymer material used as the substrate for the phantom. [Claim 14] The method according to claim 11, wherein the production of the phantom involves molding a material or mixture of materials, particularly a polymer material, into a mold, the mold shape being formed particularly on the basis of 3D printing. [Claim 15] The method according to claim 14, wherein the molding is divided into two or more steps, and one or more pieces of different materials, in particular calcium-containing materials, are inserted between the two molding steps. [Claim 16] A phantom that particularly mimics a food product type in the verification method according to any one of claims 1 to 9.

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