Testing system, casting production plant and method for examining a test object

Abstract

The invention relates to a testing system (10) for examining a test object (P), comprising a computed tomography imaging device (20) with a scanning device (22) having an X-ray source (24) and an X-ray detector (26), wherein the imaging device (20) is configured to irradiate a detection area (28) located between the X-ray source (24) and the X-ray detector (26) in order to acquire at least a first projection data set from the detection area (28) and a second projection data set from the detection area (28), and a positioning device (30) for positioning the test object (P) and / or the scanning device (22).

Description

[0001] The invention relates to a testing system for examining a test object, a casting production plant with the testing system and a method for examining a test object.

[0002] Using X-ray computed tomography (X-ray CT, simplified: CT), cross-sectional images of components (e.g., cast parts) can be generated in modern industrial manufacturing for non-destructive and, if necessary, automated inspection. A region of interest on a component to be inspected (the so-called test object) is usually placed between an X-ray source and an X-ray detector and rotated around a rotation axis relative to the X-ray source and X-ray detector while being irradiated with X-rays. The intensity of the X-rays penetrating the region of interest is attenuated by absorption, resulting in an intensity profile for each projection, which is recorded by an X-ray detector.Using conventional reconstruction algorithms, such as (filtered) backprojection, a cross-sectional image can finally be created through the region of interest perpendicular to the mentioned rotation axis.

[0003] Against this background, it is an object of the present invention to provide an inspection system with which defects in castings can be examined more precisely and efficiently. Furthermore, it is an object of the present invention to provide a corresponding casting production system and a method for examining a test object.

[0004] This object is achieved by a testing system having the features of patent claim 1, a casting production plant according to patent claim 10 and a method for examining a test object having the features of patent claim 11.

[0005] The inspection system is intended for examining a test object and comprises a computed tomography imaging device with a scanning device having an X-ray source and an X-ray detector, wherein the imaging device is configured to irradiate a detection area located between the X-ray source and the X-ray detector in order to acquire at least a first projection data set from the detection area and a second projection data set from the detection area. Furthermore, the inspection system comprises a positioning device for positioning the test object and / or the scanning device, as well as a control device configured to control the positioning device, to effect a first rotation of at least one region of interest of the test object about a first rotation axis, and to control the imaging device to acquire the first projection data set during the first rotation.Furthermore, the control device is designed to control the positioning device, to effect a second rotation of at least the region of interest of the test object about a second rotation axis different from the first rotation axis, and to control the imaging device to acquire the second projection data set during the second rotation, as well as to reconstruct a first image based on the first projection data set and a second image based on the second projection data set. The test object can advantageously be a cast part, for example, a cast vehicle component. Accordingly, the testing system can be designed as a so-called inline CT system for the non-destructive examination of cast parts.

[0006] In the context of the present disclosure, the term "computed tomography," as is common in the technical field of X-ray imaging, refers to the acquisition of X-rays after interaction with the material of the test object and the computer-assisted reconstruction of at least one image based on the acquired X-rays, without being limited to a specific scan geometry. In particular, computed tomography can refer to 2D CT, 3D CT, helical CT, and / or laminography. The reconstruction can include filtered backprojection or model-based reconstruction algorithms.

[0007] The system according to the invention enables the region of interest of this test object to be captured using various scans. This allows defects in the test object, for example, cavities, especially thread cavities, to be examined relatively precisely. In particular, the second image acquired while rotating about the second rotation axis makes it possible to verify whether a defect candidate identified in the first image is actually a defect and to determine the actual dimensions of this defect. Of particular advantage for industrial CT scanning can be that imaging errors from the first image can be attenuated in the second image, and vice versa. Consequently, the inspection system can enable imaging results to be validated synergistically, efficiently, and cost-effectively.

[0008] The X-ray detector and the X-ray source are arranged opposite each other. They are preferably located in a housing that (at least partially) shields X-ray radiation. It is conceivable to use multiple X-ray sources and multiple X-ray detectors simultaneously. During the acquisition of the projection data sets described here, a connecting axis between the X-ray detector and the X-ray source, defined by the central beam (so-called main beam) of the X-ray source, can run through the detection area. The X-rays preferably leave the X-ray source as a fan beam or a cone beam. The X-ray tube is preferably intended for non-destructive material testing. For example, an X-ray tube from Comet, Flamatt, Switzerland, with a nominal tube voltage of 450 kV and / or a radiation angle of 40° x 30° can be used as the X-ray source. Alternatively, the beam from the X-ray source can be collimated, i.e.In simple terms, they are composed of individual beams parallel to each other. Regardless of the shape of the beam from the X-ray source, it is characterized by its symmetry around the central beam. The X-ray detector can be designed as a straight or curved line detector, or as a flat or curved matrix detector.

[0009] It was stated that the control device can control the positioning device to effect a first rotation of at least the region of interest of the test object about the first axis of rotation. This (first) rotation can be realized, when viewed from the environment, as a rotation of the scanning device (including X-ray source and X-ray detector) about the stationary test object or as a rotation of the test object with the scanning device stationary (during the respective rotation). This means that when viewed from the environment, the X-ray source and X-ray detector can rotate around the stationary test object. Alternatively, the first rotation can be realized as a rotation of the test object in the environmental reference system in which the scanning device is stationary. This applies analogously to the second rotation about the second axis of rotation.

[0010] The first axis of rotation and the second axis of rotation preferably run transversely to one another and can intersect one another. In the environmental reference system, the first axis of rotation preferably runs vertically and / or (during the first rotation) perpendicular to a connecting axis between the X-ray source and the X-ray detector. This means that the connecting axis and the first axis of rotation can together span a vertical plane. The test object is preferably arranged with its main direction of extension parallel to the first axis of rotation, i.e. upright. The second axis of rotation can run transversely to the vertical. An intersection point of the first axis of rotation with the second axis of rotation can define an origin of the environmental coordinate system, which preferably lies in the region of interest. An angle between the first axis of rotation and the second axis of rotation (i.e.The minimum intermediate angle (or a minimum intermediate angle) is preferably at least 2°, or at least 5°, or at least 10°. The angle may also be at most 20°, or at most 30°, or at most 40°. Most preferably, this angle is between 10° and 20°. These relatively small angles enable even comparatively heavy test objects to be mechanically positioned precisely and cost-efficiently, while simultaneously achieving the advantages described above.

[0011] The positioning device may comprise several parts to realize the rotation(s) about the first and second rotation axes, respectively. The positions of the first and second rotation axes in the environmental reference system are preferably fixed.

[0012] In one variant, the positioning device can comprise at least one rotary table (rotary plate) that defines the first rotation axis and the second rotation axis and is mounted tiltably in the reference system of the environment of the test system. In particular, the positioning device can comprise a first part and a second part. The first part of the positioning device can be designed as the rotary table, which here is preferably configured to rotate the test object about a rotation axis of the rotary table. The second part of the positioning device can be configured to tilt the rotary table (including the test object) between a first state in which its rotation axis corresponds to the first rotation axis, and a second state in which its rotation axis corresponds to the second rotation axis. Advantageously, the X-ray source and the X-ray detector can each be stationary in the environment coordinate system during the first and / or second rotation.More specifically, the X-ray source and the X-ray detector can have the same position during both the first rotation and the second rotation, for example, they can be fixedly (stationarily) mounted in the imaging device.

[0013] A further variant provides that the positioning device comprises the aforementioned first part but not the second part, i.e. the axis of rotation is fixedly aligned in the environmental reference system. According to this variant, the scanning device can be tiltable by means of a third part of the positioning device. This means that in order to realize the first and second rotations, the third part of the positioning device can change a pivotable axis of the scanning device, about which the X-ray source and the X-ray detector rotate, such that the pivotable axis corresponds to the first axis of rotation in a first orientation of the scanning device and to the second axis of rotation in a second orientation of the scanning device. The pivotable axis preferably runs through the origin of the environmental coordinate system defined as described above. The third part can be implemented, for example, as a C-arm.The advantage here is that there is no need for additional mechanics to tilt the test object (when viewed from the surroundings).

[0014] In a further variant, the test object, when viewed from the surroundings, can be stationary in the detection area during the first or second rotation. In this case, the first or second rotation as well as the pivoting of the pivotable axis can be realized exclusively by displacing the X-ray source and X-ray detector. In this case, the X-ray source and the X-ray detector can rotate about the first or second axis of rotation during the first and / or second rotation in the surrounding coordinate system. Furthermore, the third part of the positioning device can pivot the pivotable axis of the scanning device, about which the X-ray source and the X-ray detector rotate, such that it corresponds to the first axis of rotation in the first orientation of the scanning device and to the second axis of rotation in the second orientation of the scanning device. In this case, too, the third part can be implemented as a C-arm.

[0015] The control device is connected to the imaging device and the positioning device for signal transmission. It can control the imaging device and the positioning device to acquire the first and second projection data sets synchronously with the first and second rotations, respectively. The angle of rotation of the first and second rotations is preferably between 180° and 360°. The second rotation can be controlled immediately after the first rotation. The first and second images generated on the basis of the first projection data set and the second projection data set, respectively, are preferably sectional images through the region of interest. To generate a three-dimensional image data set, a plurality of first and second images (sectional images) can be generated on different planes, as described above.

[0016] In addition to the rotational movements described above, the positioning device preferably offers translational degrees of freedom. Thus, the positioning device can comprise a conveyor device configured to displace the test object / region of interest relative to the detection zone, in particular transversely to the first and / or second rotational axis. Preferably, the positioning device comprises a holder for the test object, which can be displaced translationally by means of the conveyor device in order to displace the region of interest into the detection zone and optionally out of the detection zone. This enables the test objects to be examined more easily and quickly in series production.The rotation table can be tiltably mounted on the conveyor device by means of the positioning device, so that the test object can be positioned outside the housing on the rotation table, moved with the region of interest into the detection area and then rotated about the first and second rotation axes as explained above.

[0017] In order to efficiently scan several test objects one after the other using the same scanning device, the conveying device can further comprise a first carrier section for the test object and a second carrier section for a further test object. The conveying device can be arranged to selectively arrange the first carrier section or the second carrier section in the housing. Preferably, the conveying device comprises at least one rail and at least one carriage on which the first and / or the second carrier section can be formed. In this embodiment, it can be provided that a first part and / or a second part of the positioning device is provided for each carrier section (and for each test object). The conveying device can be designed such that (exclusively) either the first carrier section or the second carrier section can be arranged in an interior region of the imaging device delimited by the housing.Thus, the conveying device can displace the test object and the further test object at a first section of the housing into the interior (translationally) and displace them out of the interior at a second section of the housing which is different from the first section and in particular opposite the first section.

[0018] During series production of cast parts, the second carrier section can thus be loaded with a second cast part (the further test object), while a first cast part (the test object) is visualized under the control of the control device. Subsequently, the area of ​​interest of the second cast part can be moved into the detection area by means of the conveyor device, controlled by the control device, while the first cast part on the first carrier section is moved out of the housing so that it can be removed from the conveyor device.

[0019] The reconstructed first and second images, or the associated three-dimensional image data sets, can be displayed using a display device of the inspection system. For this purpose, the control device is preferably designed to register the first image with the second image or a virtual image corresponding at least partially to the region of interest, and preferably to control the display device to display the first image, the second image, and / or the virtual image sequentially or simultaneously in response to a predetermined user input. The virtual image can be generated based on a CAD data set corresponding to the inspection object or the further inspection object.In one variant, a third image can be generated based on the second images, corresponding to the first image in terms of orientation. This third image can be used instead of or in addition to the second image for registration and / or display via control by the control device. In all cases, registration can be based on individual (intrinsic or extrinsic) features of the respective test object / casting. The control device can be configured to recognize these features using computer-implemented technology. Alternatively, the features can be identified via user input.

[0020] A casting production facility proposed here comprises a testing system described in detail above. Such a casting production facility can be part of a foundry. Accordingly, the test object, preferably in the form of a cast part, can be cast from a metal or an alloy.

[0021] In the method proposed here, a test object can be examined using an inspection system. The inspection system comprises a computed tomography imaging device with a scanning device having an X-ray source and an X-ray detector, a positioning device for positioning the test object and / or the scanning device, and a control device. This inspection system is preferably the inspection system described above. In the method, a detection area located between the X-ray source and the X-ray detector is irradiated by means of the imaging device in order to acquire at least one first projection data set from the detection area and a second projection data set from the detection area.The method comprises in particular the following steps, which can preferably be carried out in the following order, partly simultaneously: controlling the positioning device to effect a first rotation of at least one region of interest of the test object about a first axis of rotation; controlling the imaging device to acquire the first projection data set during the first rotation; controlling the positioning device to effect a second rotation of at least the region of interest of the test object about a second axis of rotation different from the first axis of rotation; controlling the imaging device to acquire the second projection data set during the second rotation; and reconstructing a first image based on the second projection data set and a second image based on the second projection data set.

[0022] Furthermore, this method for examining the test object may have any, in particular all, of the features described above in connection with the test system. In particular, the method may include any functions of the test system and its components as method steps.

[0023] Preferred embodiments of a testing system, a casting production plant and a method for examining a test object will now be explained in more detail with reference to the attached schematic, not to scale drawings, wherein Fig. 1 shows a first variant of a testing system in a perspective view; Fig. 2 the test system Fig. 1 shows a plan view of a first casting as a test object located inside the imaging device; Fig. 3 the test system Fig. 1 shows a plan view of a second casting (further test object) located inside the imaging device; Fig. 4 the test system Fig. 1 in a perspective view while a first rotation is performed; Fig. 5 the test system Fig. 1 in a perspective view while a second rotation is being performed; Fig. 6 a casting production plant with the testing system from Fig. 1 shows; and Fig. 7 shows a method for examining a test object including its process steps.

[0024] The Fig. 1 to 5 show an inspection system 10 for examining a test object P, which here is, for example, a cast part, for example, a metallic casting. The cast part contains a defect, for example, a thread void, which can be examined by the inspection system 10; the defect thus defines the region of interest of the test object P.

[0025] In order to be able to examine the test object P non-destructively, the test system 10 comprises an X-ray-based computed tomography imaging device 20, a positioning device 30 for positioning the test object P at a suitable location and a control device 40 connected to the positioning device and the imaging device for signal transmission. The imaging device 20 has a scanning device 22 with at least one X-ray source 24 and at least one X-ray detector 26. In this embodiment, the X-ray source 24 is configured to Fig. 1 to emit an (X-ray) fan beam, indicated by dashed lines, toward the X-ray detector 26. The latter is preferably designed as a line detector and positioned in the fan beam. Between the X-ray source 24 and the X-ray detector 26, there is thus a detection area 28 through which the fan beam passes during operation in order to detect multiple projection data sets, in particular a first projection data set from the detection area 28 and a second projection data set from the detection area 28.

[0026] The X-ray source 24 and the X-ray detector 26 are arranged within a shielding housing 60 of the imaging device 20, which defines the interior region 62 of the imaging device 20. The detection area 28 is located in the interior region 62. The scanning device 22 can generally be designed such that the X-ray source 24 and the X-ray detector 26 are coupled to one another via a rigid connection, so that a central beam of the X-ray source 24 impinges centrally on the line detector. In the present variant, the X-ray source 24 and the X-ray detector 26 are mounted stationary in the environmental reference system of the imaging device 20, so that they do not move during the imaging process.In one or more modifications, at least part of the relative movement between the test object P and the scanning device 22 (including X-ray source 24 and X-ray detector 26) can be realized by moving the scanning device 22 by means of the positioning device 30, controlled by the control device 40.

[0027] The positioning device 30 is in the variant made of Fig. 1 is arranged to position the test object P such that the region of interest P1 can actually be captured at least in part by the imaging device 20, i.e., is located at least in part in the capture region 28 when the projection data sets described below are captured. For this purpose, the positioning device 30 in the present case comprises a conveyor device 50 with a first carrier section 56. The conveyor device 50 is provided to displace the region of interest P1 transversely to the first and / or second rotation axis A, B relative to the capture region 28.

[0028] Preferably, the conveyor device 50 also has a second carrier section 58 for a further test object (see Fig. 1) which can be formed integrally with the first support section 56 and the first support section 56 accordingly. As shown in the Fig. 2 and Fig. 3, the conveying device 50 can optionally arrange the first support section 56 or the second support section 58 in the interior region 62 of the housing 60. What is stated below for the first support section 56 and for elements located thereon (in particular the rotary table 54 and the further test object) therefore applies accordingly to the second support section 58. The first support section 56 and the second support section 58 can be formed on the upper sides of respective carriages, which can be guided by means of one or more rails 57, 59.

[0029] The positioning device 30 comprises rotary tables 52, 54, each defining a first rotation axis A and a second rotation axis B. The rotary tables 52, 54 are mounted on the conveyor device 50 so that they can be tilted in the reference system of the environment of the test system 10. The statements below regarding the rotary table 52 apply accordingly to the rotary table 54.

[0030] The rotation table 52 forms a first part of the positioning device 30. It has an axis of rotation about which the test object P can be rotated, and is tiltably mounted on the first support section 56 by means of a second part of the positioning device 30. The second part of the positioning device can be configured to tilt the rotation table 52 (including the test object) under control of the control device 40 between a first state in which its axis of rotation corresponds to the first axis of rotation A, and a second state in which its axis of rotation corresponds to the second axis of rotation B, which is different from the first axis of rotation A. The first axis of rotation A preferably runs at an angle α to the second axis of rotation B. The first axis of rotation A can be oriented vertically.Preferably, the first rotation axis A and the second rotation axis B intersect; the intersection point can define the origin of an environmental coordinate system. In this case, the angle α is between 5° and 30°, in particular 15° (+ / - 5°).

[0031] In order to move the area of ​​interest P1 into the detection area 28, the test object P is attached to the rotation table 52, after which it is moved into its Fig. 2 in the interior. The control device 40 then controls the scanning device 22 and the positioning device 30 to perform the imaging of the region of interest P1. For this purpose, the control device 40 is designed to control the positioning device 30, to effect a first rotation of the region of interest P1 of the test object P about the first axis of rotation A, and to control the imaging device 20 to acquire the first projection data set during the first rotation. Furthermore, the control device 40 can control the positioning device 30 to effect the second rotation of the region of interest P1 of the test object P about a second axis of rotation B different from the first axis of rotation A, and to control the imaging device 20 to acquire the second projection data set during the second rotation.During the first rotation and the second rotation, the entire test object P is rotated around the first and second rotation axes A, B running through the test object P.

[0032] The control device 40 reconstructs a first image (sectional image) based on the first projection data set and a second image (sectional image) based on the second projection data set. In order to generate a three-dimensional image data set with a plurality of first images obtained in this way, the positioning device 30 can be designed to effect a relative movement between the scanning device 22 and the test object P parallel to the first or second rotation axes A, B. The further first or second projection data sets obtained in this way are then reconstructed into further first / second images by means of the control device 40, for example by means of back projection. While the test object P is located in the interior region 62, the further test object can be positioned on the second carrier section 58.

[0033] After all desired projection data sets of the test object P have been recorded, the second support section 58 can be moved into the interior region 62 by means of the conveyor device 50. The further test object can then be subjected to the same imaging as the test object P. In this way, the inspection system 10 enables test parts of a production line to be examined sequentially and efficiently for defects. While the second support section 58 and the further test object are located in the interior region 62, the test object P can be removed from the first support section 56 outside the housing 60. In a modification, the first and second support sections 56, 58 can be moved back and forth by means of the conveyor device 50, i.e., the displacement of the second support section 58 into the interior region 62 (including the simultaneous displacement of the first support section 56 out of the interior region 62) can be reversed.

[0034] For the visual representation of the acquired first and second images or the associated image data sets, the inspection system 10 can include a display device 64. The control device 40 can further be configured to register the first image with the second image or a virtual image corresponding at least partially to the region of interest P1. Furthermore, the control device 40 can control the display device 64 to display the first image, the second image, and / or the virtual image sequentially or simultaneously in response to a predetermined user input.

[0035] A casting production plant 100 is in Fig. 6. It comprises the above-described inspection system 10, with which castings can be examined one after the other as test objects P in a production line. The castings can be produced in a casting device of the casting production plant 100.

[0036] The method 200 for examining a test object P by means of the test system 10 is shown in Fig. 7 is shown in a highly simplified manner. The test system 10 has the features described above in connection with the Fig.1 to 5, and the method 200 provides for irradiating a detection area 28 located between the X-ray source 24 and the X-ray detector 26 by means of the imaging device 20 in order to acquire at least a first projection data set from the detection area 28 and a second projection data set from the detection area 28. The positioning device 30 is controlled in a step 204 to effect a first rotation of at least one region of interest P1 of the test object P about a first axis of rotation A. The imaging device 20 is controlled in step 206, which is carried out simultaneously with step 204, to acquire the first projection data set during the first rotation. In step 208, the positioning device 30 is controlled to effect a second rotation of at least the region of interest P1 of the test object P about a second axis of rotation B that is different from the first axis of rotation A.Step 210, which is performed simultaneously, provides for controlling the imaging device 20 to acquire the second projection data set during the second rotation. Finally, in step 212, a first image is reconstructed based on the second projection data set, and a second image is reconstructed based on the second projection data set. Further method steps of method 208 can correspond to the functions of the inspection system 10 described above.

[0037] In the context of the present disclosure, the terms "comprising," "having," "with," and similar terms are not intended to be exhaustive. For the sake of readability, the expression "at least one" has been partially omitted in this disclosure. If a feature is described in the singular, this also refers to the plural (e.g., the at least one X-ray source / the one or more X-ray sources, etc.). At least partially means, in this case, partially or completely.

Claims

[1] Test system (10) for examining a test object (P), comprising a computed tomographic imaging device (20) with a scanning device (22) which has an X-ray source (24) and an X-ray detector (26), wherein the imaging device (20) is configured to irradiate a detection area (28) located between the X-ray source (24) and the X-ray detector (26) in order to acquire at least a first projection data set from the detection area (28) and a second projection data set from the detection area (28), a positioning device (30) for positioning the test object (P) and / or the scanning device (22), and a control device (40) which is designed to to control the positioning device (30) to effect a first rotation of at least one region of interest (P1) of the test object (P) about a first axis of rotation (A), and to control the imaging device (20) to acquire the first projection data set during the first rotation, to control the positioning device (30) to effect a second rotation of at least the region of interest (P1) of the test object (P) about a second rotation axis (B) different from the first rotation axis (A), and to control the imaging device (20) to acquire the second projection data set during the second rotation, and to reconstruct a first image based on the first projection data set and a second image based on the second projection data set. [2] Test system (10) according to claim 1, wherein an angle (a) between the first rotation axis (A) and the second rotation axis (B) is at least 5° and / or at most 30°. [3] Test system (10) according to claim 2, wherein the angle (a) is between 10° and 20°. [4] Test system (10) according to one of the preceding claims, wherein the first rotation axis (A) is perpendicular to a connecting axis between the X-ray source (24) and the X-ray detector (26), and / or wherein the first axis of rotation (A) runs vertically. [5] Test system (10) according to one of the preceding claims, wherein the positioning device (30) comprises at least one rotation table (52, 54) defining the first rotation axis (A) and the second rotation axis (B), which is tiltably mounted in the reference system of the environment of the test system (10). [6] Test system (10) according to one of the preceding claims, wherein the positioning device (30) comprises a conveying device (50) which is designed to displace the region of interest (P1) transversely to the first and / or second axis of rotation (A, B) relative to the detection region (28). [7] Test system (10) according to claim 6 in conjunction with claim 5, wherein the rotary table (52, 54) is tiltably mounted on the conveyor device (50). [8] Test system (10) according to claim 6 or 7, further comprising a housing (60) which defines an interior region (62) of the test system (10) and in which the detection region (28) is arranged, wherein the conveying device (50) has a first carrier section (56) for the test object (P) and a second carrier section (58) for a further test object (P) and is arranged to selectively arrange the first carrier section (56) or the second carrier section (58) in the housing (60). [9] Test system (10) according to one of the preceding claims, further comprising a display device (64), wherein the control device (40) is designed to register the first image with the second image or a virtual image corresponding at least in part to the region of interest (P1) and to control the display device (64) to display the first image, the second image and / or the virtual image successively or simultaneously in response to a predetermined user input. [10] Casting production plant (100) comprising a testing system (10) according to one of the preceding claims. [11] Method (200) for examining a test object (P) by means of a test system (10), wherein the test system (10) comprises a computed tomography imaging device (20) with a scanning device (22) having an X-ray source (24) and an X-ray detector (26), a positioning device (30) for positioning the test object (P) and / or the scanning device (22), and a control device (40), wherein the method provides for irradiating a detection area (28) located between the X-ray source (24) and the X-ray detector (26) by means of the imaging device (20) in order to acquire at least a first projection data set from the detection area (28) and a second projection data set from the detection area (28), and comprises the following steps: Controlling (204) the positioning device (30) to effect a first rotation of at least one region of interest (P1) of the test object (P) about a first axis of rotation (A); controlling (206) the imaging device (20) to acquire the first projection data set during the first rotation; Controlling (208) the positioning device (30) to effect a second rotation of at least the region of interest (P1) of the test object (P) about a second rotation axis (B) different from the first rotation axis (A); controlling (210) the imaging device (20) to acquire the second projection data set during the second rotation; and Reconstructing (212) a first image based on the second projection data set and a second image based on the second projection data set.

Images