Systems and methods for X-ray dark field, phase contrast, and attenuation image acquisition

Abstract

The present invention relates to a system (1010) for X-ray dark field, phase contrast and attenuation image acquisition, the system comprising: an X-ray source (1020); an interferometer arrangement (1030); an X-ray detector (1040); a control unit (1050); at least one vibration transducer (1080); a processing unit (1090); and an output unit (1060). An axis is defined extending from the center of the X-ray source to the center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector, wherein the axis extends through the examination region, and wherein the examination region is configured to enable positioning of an object to be examined. The interferometer arrangement is located between the X-ray source and the X-ray detector, and wherein the interferometer arrangement comprises a first grating (1032) and a second grating (1034). For a first operating mode: the control unit is configured to control at least one transverse movement transducer (1070) to move the first grating or the second grating in a transverse position direction perpendicular to the axis. The control unit is configured to control the X-ray detector to acquire image data while the first grating and / or the second grating are moving. During an exposure time of the X-ray detector, the first grating and / or the second grating have moved a distance less than a period of the first grating and / or the second grating. The control unit is configured to control the movement of the first grating and / or the second grating so that the image data are acquired while the first grating and / or the second grating are moving. The output unit is configured to output one or more of the following: dark field image data, phase contrast image data, and attenuation image data; for a second operating mode: the control unit is configured to control the X-ray detector to acquire each of a plurality of image data while the first grating and / or the second grating are moving during the exposure time of the X-ray detector. The control unit is configured to control the at least one vibration transducer to vibrate the first grating and / or the second grating. The amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating. The processing unit is configured to generate attenuation image data and / or calibration data, including determining a temporally low-pass filtered version of at least some of the plurality of image data. The output unit is configured to output the attenuation image data and / or the calibration data.

Description

Technical Field

[0001] The invention relates to a system for X-ray dark field, phase contrast and attenuation image acquisition, a method for X-ray dark field, phase contrast and attenuation image acquisition, a system for attenuation image and / or calibration data acquisition, a method for attenuation image and / or calibration data acquisition, a computer program element and a computer-readable medium. Background Art

[0002] Conventional linear attenuation X-ray systems and conventional computed tomography (CT) measure the linear attenuation coefficient of an object. One of the main drawbacks of such conventional techniques is the low contrast between different tissue types, which requires the use of relatively high X-ray doses and / or the use of additional contrast agents.

[0003] Grating-based phase contrast (gbPC) X-ray imaging (both radiography and computed tomography) is an approach that offers a new X-ray imaging modality, providing simultaneous images of the linear attenuation coefficient, electron density, and small-angle scatter (i.e., images obtained from a dark-field signal).

[0004] The latter two imaging modalities of X-ray phase contrast and dark field imaging are two new imaging modalities that have shown the potential to significantly increase the diagnostic accuracy for soft tissue imaging. For example, dark field CT (DF-CT) is a new tomographic modality that can visualize anatomical structures below the resolution limit of the detector by quantifying the amount of ultra-small angle scattering of X-rays caused by these tiny structures. One of the areas that has been identified as being most likely to benefit from these two new imaging modalities is chest radiography. For example, it has been shown that X-ray dark field information can significantly aid in the diagnosis of lung diseases such as chronic obstructive pulmonary disease (COPD) or fibrosis.

[0005] In order to acquire these new imaging modalities, two or three grating interferometers are introduced into the X-ray beam, these grating interferometers are usually referred to as G0, G1 and G2 gratings. The source grating G0 can be used to make the radiation from the source more coherent but is not always necessary, while the gratings G1 and G2 are usually referred to as phase gratings and analyzer gratings. Subsequently, one of the two gratings G1 or G2 is moved perpendicular to the grating sheet relative to the other gratings in a number of steps (so-called stepping), and if the source grating G0 is used, it can be this grating that is stepped laterally (wherein laterally means perpendicular to the grating direction). Thus, an image is recorded for each new grating position. Comparison of a sequence of images acquired with and without a sample in the beam allows the calculation of three imaging signals: transmission or attenuation (conventional X-ray image), phase contrast image and dark field image. At least three images in the sequence (stepping curve) are required to calculate the three imaging signals. However, in practice, significantly more images are recorded to allow stable signal extraction. These gratings generate a fringe pattern on top of a conventional transmission image, and the dark field signal is calculated, for example, as the loss of contrast of this fringe pattern.

[0006] Therefore, the gbPC system uses a step acquisition method. This means that for one multimodal image, several projections are combined. Between each projection, a grating is moved to another position to retrieve the step curve. The setup focuses on minimal movement of the grating during acquisition, for example due to vibrations, to ensure good results. Reproducibility and speed of repositioning can be a challenge and will always result in a time gap between two measurements, during which the setup is moving and no acquisition is active.

[0007] The reason for this is that the fringe patterns analyzed in gbPC imaging are fine structures in the micrometer range. Using an analyzer grating with the same periodicity, the moiré pattern can be measured with a detector. Any movement of one or more interferometer components on this length scale changes the phase of the moiré pattern. During exposure, this movement causes blurring and, consequently, signal degradation. Here, exposure refers to the time during which the X-rays transmitted through the object are integrated to generate the original image. This is also called the integration period.

[0008] Existing X-ray imaging systems are designed for structures several orders of magnitude larger than this fringe pattern; therefore, standard X-ray systems can tolerate much greater vibration than gbPC setups. To enable the integration of gbPC and conventional CT infrastructure, implementations must be vibration-tolerant. Because laboratory gbPC imaging systems have been developed in a nearly vibration-free environment, common acquisition protocols consist of 5 to 30 exposures, with exposure times on the order of seconds. The repositioning time between exposures is unused, and the system must be stopped and brought to a standstill before acquiring the next image in the step-curve image set. The transition from laboratory to conventional CT approaches to step-curve methods struggles with these two issues. On the one hand, the repositioning time interval must be shortened to minimize acquisition time. WO 2016 / 177875 A1 discloses an X-ray imaging system in which faster X-ray acquisition times are possible. On the other hand, the system can no longer be considered vibration-free. This degrades images with long exposure times because the fringe pattern moves during measurement.

[0009] Another problem arises during calibration protocols, such as detector calibration measurements. For these measurements, it would be best to remove all gratings from the system; however, this is not always possible, and if done, the X-ray filtering would be altered, leading to calibration errors. Accurate calibration data is therefore necessary to acquire and reconstruct quantitatively correct images. In conventional CT, highly uniform elements are placed in the beam, such as thin metal sheets for beam filtering or highly accurately shaped POMs to shape the beam's intensity distribution (so-called wedge filters). Due to the high precision of these elements, their spectral impact can be analytically calculated. Gratings used in new imaging modalities cannot be manufactured with such high precision. The current state-of-the-art production process is X-ray LIGA, which is a combination of photolithography and electroplating. The period of the grating can be manufactured with extremely high precision due to the high precision provided by the photolithographic method. On the other hand, filling the grating structure with highly attenuating materials such as gold or bismuth cannot be achieved with sufficient uniformity. Field inhomogeneities during electroplating lead to variations in the height of the grating, and local defects in the substrate can cause the localized appearance of extra gold grains on top of the grating. Finally, due to nonlinear partial volume effects, slight misalignments of the gratings in the beam can lead to large differences in the spectrum across the beam. Therefore, a problem with these new imaging modalities is that the spectrum of the X-ray beam cannot be calculated analytically, but must be measured. However, measurement of spectral properties is hampered by the fringe pattern generated by the grating arrangement.

[0010] These issues need to be addressed. Summary of the Invention

[0011] It would be advantageous to have an improved system for acquiring dark field, phase contrast and attenuation X-ray image data and for determining calibration data for such a system.

[0012] The object of the present invention is solved by the subject matter of one aspect, wherein further embodiments are incorporated into another aspect. It should be noted that the aspects and examples of the invention described below also apply to a system for X-ray dark field, phase contrast and attenuation image acquisition, a method for X-ray dark field, phase contrast and attenuation image acquisition, a system for attenuation image and / or calibration data acquisition, a method for attenuation image and / or calibration data acquisition, as well as a computer program element and a computer-readable medium.

[0013] In a first aspect, a system for X-ray dark field, phase contrast and attenuation image acquisition is provided, the system comprising:

[0014] X-ray source;

[0015] interferometer device;

[0016] X-ray detectors;

[0017] control unit;

[0018] at least one vibration transducer;

[0019] processing unit; and

[0020] Output unit;

[0021] An axis is defined as extending from the center of the X-ray source to the center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector. The axis extending from the center of the X-ray source to the center of the X-ray detector also extends through the examination region. The examination region is configured (sized, positioned, and accessible) to enable positioning of an object to be examined. The interferometer device is located between the X-ray source and the X-ray detector, and wherein the interferometer device includes a first grating and a second grating.

[0022] For the first operating mode:

[0023] The control unit is configured to control at least one transversely moving transducer to move the first grating or the second grating in a transverse position direction perpendicular to the axis. The control unit is configured to control the X-ray detector to acquire image data when the first grating and / or the second grating are moving. During the exposure time of the X-ray detector, the first grating and / or the second grating have moved a distance less than the period of the first grating and / or the second grating. The control unit is configured to control the movement of the first grating and / or the second grating so that the image data is acquired when the first grating and / or the second grating are moving. The output unit is configured to output one or more of the following: dark field image data, phase contrast image data, and attenuation image data.

[0024] For the second operating mode:

[0025] The control unit is configured to control the X-ray detector to acquire each of a plurality of image data when the first grating and / or the second grating moves during an exposure time of the X-ray detector. The control unit is configured to control the at least one vibration transducer to vibrate the first grating and / or the second grating. The amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating. The processing unit is configured to generate attenuation image data and / or calibration data, including determining a temporal low-pass filtered version of at least some of the plurality of image data. The output unit is configured to output the attenuation image data and / or the calibration data.

[0026] In other words, an X-ray imaging system is provided with an interferometric arrangement in which either a first or a second grating is laterally shifted in order to generate the required step curve from which dark field, phase contrast and attenuation image data can be reconstructed, but one or both of these gratings is intentionally moved during image acquisition, which is achieved by having an exposure time that is short enough so that the moiré fringes on the detector are not washed out due to the movement.

[0027] In this way, "walking" curve image data, which may require 5-30 individual images at different lateral positions of the first and / or second gratings, can be acquired more quickly, wherein the X-ray exposure of the patient is reduced. This is because the gratings are always movable, and wherein, for example, image data can be acquired as part of the movement to the next of the 5-30 different positions. Thus, the gratings are not so stepped, wherein they are not positioned statically when acquiring image data, but rather are intentionally moved when acquiring image data, and can actually be moved continuously.

[0028] In other words, the system allows continuous data acquisition in grating-based phase contrast and dark-field measurements.

[0029] In other words, the system operates as a DAX system in the first mode, where the moiré fringes on the detector are used to generate dark field, phase contrast and, in effect, attenuation data, but now in the second mode, the fringe pattern (where the grating is still positioned in the beam) is washed out and the system operates in a "normal" attenuation mode, providing a calibration function.

[0030] In an example, for the first operating mode, the control unit is configured to control the X-ray detector such that the exposure time is smaller than a time period of a resonance frequency of vibration of the first grating and / or the second grating.

[0031] In this way, in addition to having a short exposure time that enables intentional movement of the grating(s) without washing out the fringe pattern, the vibration and repositioning time gaps of the setup are also mitigated due to the reduced acquisition time being a small fraction of the system vibration period. The vibration source can be inherent to the system or added via external devices such as vibration transducers.

[0032] Thus, in a first operating mode, a constantly moving grating (or gratings) is utilized, wherein the effects of blurring are reduced by reducing the exposure time, wherein the exposure time is short enough that the grating movement during a single exposure can be effectively ignored. This can be achieved when the exposure time is significantly shorter than the period of the dominant oscillation frequency of the gratings. In this context, constantly moving grating (or gratings) may refer to one or more of the gratings moving in a continuous linear motion in one direction, and may also refer to one or the other or both of the gratings performing a periodic motion.

[0033] In other words, the system allows continuous data acquisition in grating-based phase contrast and dark-field measurements and is additionally tolerant to external vibrations.

[0034] In an example, for the first operating mode, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

[0035] Thus, the at least one laterally movable transducer can continuously move one or more gratings into positions for image data collection for dark field and phase contrast image data acquisition. Previously, it was necessary to stop the grating movement while image acquisition occurred, but now image acquisition occurs while the grating moves between desired positions, and the overall image acquisition timescale and patient dose are reduced.

[0036] In an example, in the second mode of operation, the applying of the low pass filtering comprises determining an average of the at least some of the plurality of image data.

[0037] In other words, moving one or both of the gratings by at least this distance and averaging the acquired data for the gratings at different positions combined with the application of low-pass filtering results in the fringes on the detector required by the DAX system being washed out in the averaged image data. Thus, in one mode of operation, the system operates continuously to acquire data in a grating-based phase contrast and dark field measurement system with moving grating(s), and in a second mode, the system operates as a conventional attenuation image X-ray system providing system characterization and calibration without the need to remove the gratings from the beam path.

[0038] In an example, the low-pass filtering comprises a low-pass filter kernel having a length greater than a vibration period of the first grating and / or the second grating.

[0039] In an example, for the second operating mode, the control unit is configured to control the X-ray source to periodically move the focus on the target to N different target positions, and wherein the control unit is configured to control the X-ray detector to collect image data for each of the N target positions separately, so that at least some of the multiple image data are associated with one focal target position; and wherein the control unit is configured to control the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector.

[0040] In a second aspect, a method (1100) for X-ray dark field, phase contrast and attenuation image acquisition is provided, the method comprising:

[0041] a) orienting an X-ray source relative to an X-ray detector to define an axis extending from a center of the X-ray source to a center of the X-ray detector;

[0042] b) positioning an examination region between the X-ray source and the X-ray detector, wherein the first axis extends through the examination region, and wherein the examination region is configured to enable positioning of an object to be examined;

[0043] c) positioning an interferometer device between the X-ray source and the X-ray detector, wherein the interferometer device comprises a first grating and a second grating;

[0044] d) in a first operating mode, controlling by a control unit at least one transverse movement transducer to move the first grating or the second grating in a transverse position direction perpendicular to the axis;

[0045] e) in the first operating mode, controlling, by the control unit, the X-ray detector to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating have moved a distance that is smaller than a period of the first grating and / or the second grating, and wherein the control unit controls the movement of the first grating and / or the second grating such that the image data are acquired while the first grating and / or the second grating are moving;

[0046] f) in the first operation mode, outputting, by the output unit, one or more of the following: dark field image data, phase contrast image data, and attenuation image data;

[0047] g) in a second operating mode, controlling, by the control unit, the X-ray detector to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector;

[0048] h) in the second operating mode, controlling, by the control unit, at least one vibration transducer to vibrate the first grating and / or the second grating, wherein an amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating;

[0049] i) in said second mode of operation, generating, by the processing unit, attenuated image data and / or calibration data, comprising determining a temporally low-pass filtered version of at least some of said plurality of image data; and

[0050] j) Outputting the attenuation image data and / or the calibration data by the output unit in the second operating mode.

[0051] In a third aspect, there is provided a system for attenuation image and / or calibration data acquisition, the system comprising:

[0052] X-ray source;

[0053] interferometer device;

[0054] X-ray detectors;

[0055] control unit;

[0056] at least one vibration transducer;

[0057] processing unit; and

[0058] Output unit;

[0059] An axis is defined as extending from a center of the X-ray source to a center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector. The axis, defined as extending from the center of the X-ray source to the center of the X-ray detector, also extends through the examination region. The examination region is configured (sized, positioned, and accessible) to enable positioning of an object to be examined. The interferometer arrangement is located between the X-ray source and the X-ray detector, and wherein the interferometer arrangement includes a first grating and a second grating. The control unit is configured to control the X-ray detector to acquire each of a plurality of image data while the first grating and / or the second grating move during an exposure time of the X-ray detector. The control unit is configured to control the at least one vibration transducer to vibrate the first grating and / or the second grating. The amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating. The processing unit is configured to generate attenuation image data and / or calibration data, including determining a temporally low-pass filtered version of at least some of the plurality of image data. The output unit is configured to output the attenuation image data and / or the calibration data.

[0060] Thus, during the acquisition of a single image data set, the one or more gratings may only move a small distance due to the fact that they are intentionally vibrated, however, from one image data set to the next, the one or more gratings may be moved further between images, and using these images in conjunction with low pass filtering means that otherwise present fringes are washed out, leaving data that can be used for calibration purposes or as an attenuation image itself, without having to move the grating out of the beamline.

[0061] In an example, the applying of the low pass filtering comprises determining an average of the at least some of the plurality of image data.

[0062] In an example, the low-pass filtering comprises a low-pass filter kernel having a length greater than a vibration period of the first grating and / or the second grating.

[0063] In an example, the control unit is configured to control the X-ray source to periodically move a focal point on a target to N different target positions. The control unit is configured to control the X-ray detector to separately acquire image data for each of the N target positions. The control unit is configured to control the at least one vibration transducer so that a vibration frequency is less than N / (2T), where T is the exposure time of the X-ray detector.

[0064] In a fourth aspect, there is provided a method for attenuation image and / or calibration data acquisition, the method comprising:

[0065] a) positioning an X-ray source relative to an X-ray detector to define an axis extending from a center of the X-ray source to a center of the X-ray detector, wherein an examination region is located between the X-ray source and the X-ray detector, wherein a first axis extends through the examination region, wherein the examination region enables positioning of an object to be examined, and wherein an interferometer arrangement is located between the X-ray source and the X-ray detector, wherein the interferometer arrangement comprises a first grating and a second grating;

[0066] b) controlling the X-ray detector by the control unit to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector;

[0067] c) controlling, by the control unit, the at least one vibration transducer to vibrate the first grating and / or the second grating, wherein an amplitude of the vibration is greater than or equal to a period of the first grating and / or the second grating;

[0068] d) generating, by a processing unit, attenuated image data and / or calibration data, including determining a temporally low-pass filtered version of at least some of the plurality of image data; and

[0069] e) Outputting the attenuation image data and / or the calibration data by the output unit.

[0070] In an example, step d) comprises determining an average of at least some of the plurality of image data.

[0071] According to a further aspect, a computer program element for controlling a system as described above is provided, which computer program element is adapted to perform the steps of the method as described above if it is run by a processing unit.

[0072] According to another aspect, a computer readable medium storing the aforementioned computer unit is provided.

[0073] The computer program element may for example be a software program, but also an FPGA, a PLD or any other suitable digital device.

[0074] Advantageously, the benefits provided by any one of the above aspects apply equally to all other aspects, and vice versa.

[0075] The above aspects and examples will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Exemplary embodiments will be described below with reference to the following drawings:

[0077] Figure 1 shows a schematic setup of an example of a system for X-ray dark field, phase contrast and attenuation image acquisition;

[0078] Figure 2 Methods for X-ray dark field, phase contrast, and attenuation image acquisition are shown;

[0079] Figure 3 shows a schematic setup of an example of a system for X-ray dark field, phase contrast and attenuation image acquisition;

[0080] Figure 4 Methods for X-ray dark field, phase contrast, and attenuation image acquisition are shown;

[0081] Figure 5 shows a schematic setup of an example of a system for attenuation image and / or calibration data acquisition;

[0082] Figure 6 Methods for attenuation image and / or calibration data acquisition are shown;

[0083] Figure 7 shows schematic setups of examples of phase contrast, dark field, and attenuation imaging systems; and

[0084] Figure 8 Shown by Figure 7 Step curve data obtained by the imaging system. DETAILED DESCRIPTION

[0085] Figure 1An example of a system 10 for X-ray dark field, phase contrast, and attenuation image acquisition is shown, wherein not all of the features shown are required, as will now be discussed in more detail. In the example, the system includes an X-ray source 20, an interferometer arrangement 30, an X-ray detector 40, a control unit 50, and an output unit 60. An axis is defined extending from the center of the X-ray source to the center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector. The axis extends through the examination region, and the examination region is configured to enable positioning of an object to be examined. The interferometer arrangement is located between the X-ray source and the X-ray detector. The interferometer arrangement includes a first grating 32 and a second grating 34. For a first operating mode, the control unit is configured to control at least one transverse motion transducer 70 to move the first grating or the second grating in a transverse position direction perpendicular to the axis. For the first operating mode, the control unit is configured to control the X-ray detector to acquire image data while the first grating and / or the second grating are moving. For the first operating mode, during the exposure time of the X-ray detector, the control unit is configured to move the first grating and / or the second grating by a distance less than the period of the first grating and / or the second grating. The control unit is configured to control the movement of the first grating and / or the second grating so that the image data is acquired while the first grating and / or the second grating is moving. For the first operating mode, the output unit is configured to output one or more of the following: dark field image data, phase contrast image data, and attenuation image data

[0086] In other words, an X-ray imaging system is provided with an interferometric arrangement in which either a first or a second grating is laterally shifted in order to generate the required step curve from which dark field, phase contrast and attenuation image data can be reconstructed, but one or both of these gratings is intentionally moved during image acquisition, which is achieved by having an exposure time that is short enough so that the moiré fringes on the detector are not washed out due to the movement.

[0087] In this way, "walking" curve image data, which may require 5-30 individual images at different lateral positions of the first and / or second gratings, can be acquired more quickly, wherein the X-ray exposure of the patient is reduced. This is because the gratings can always be moved, and wherein, for example, image data can be acquired as part of the movement to the next of the 5-30 different positions. Therefore, the gratings are not so stepped, wherein they are not positioned statically when acquiring image data, but rather are intentionally moved when acquiring image data, and can actually be moved continuously.

[0088] In other words, the system allows continuous data acquisition in grating-based phase contrast and dark-field measurements.

[0089] In an example, the movement of the first grating in a lateral position direction perpendicular to the axis or the movement of the second grating in a lateral position direction perpendicular to the axis is also perpendicular to the grating lines in the grating.

[0090] In an example, the first grating is located between the second grating and the X-ray source.

[0091] In an example, the examination region is located between the first grating and the X-ray source.

[0092] In an example, the interferometer device includes three gratings, wherein a source grating is positioned to interact with the X-rays emitted from the source and serves to increase the coherence of the X-rays propagating through the interferometer device. Thus, in the absence of a source grating, there may be two gratings, wherein the first grating is closest to the source and is an absorption grating or a phase grating, and the second grating is closest to the detector and is an absorption grating. However, in the case of three gratings, the source grating closest to the source may be the first grating, and either of the other two gratings may be the second grating, or the upper grating that may be an absorption grating or a phase grating may be the first grating, and so on.

[0093] In an example, the first grating is an absorption grating and the second grating is an absorption grating. In an example, the first grating is a phase grating and the second grating is an absorption grating.

[0094] According to an example, for the first operating mode, the control unit is configured to control the X-ray detector such that the exposure time is smaller than a time period of a resonance frequency of vibration of the first grating and / or the second grating.

[0095] In this way, in addition to having a short exposure time that enables intentional movement of the grating(s) without washing out the fringe pattern, the vibration and repositioning time gaps of the setup are also mitigated due to the reduced acquisition time being a small fraction of the system vibration period. The vibration source can be inherent to the system or added via external devices such as vibration transducers.

[0096] Thus, in a first operating mode, a constantly moving grating (or gratings) is utilized, wherein the effects of blurring are reduced by reducing the exposure time, wherein the exposure time is short enough that the grating movement during a single exposure can be effectively ignored. This can be achieved when the exposure time is significantly shorter than the duration of the dominant oscillation frequency of the grating. In this context, constantly moving grating (or gratings) may refer to one or more of the gratings moving in a continuous linear motion in one direction, and may also refer to one or the other or both of the gratings performing a periodic motion.

[0097] In other words, the system allows continuous data acquisition in grating-based phase contrast and dark-field measurements and is additionally tolerant to external vibrations.

[0098] According to an example, for the first operating mode, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

[0099] Thus, at least one laterally movable transducer can continuously move one or more gratings into positions for image data collection for dark field and phase contrast image data acquisition. Previously, it was necessary to stop the grating movement while image acquisition occurred, but now image acquisition occurs while the grating moves between desired positions, and the overall image acquisition timescale and patient dose are reduced.

[0100] According to an example, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by a movement of the at least one transverse motion transducer in the transverse position direction as part of an image acquisition protocol.

[0101] According to an example, in a second operating mode, the control unit is configured to control the X-ray detector to acquire image data while the first grating and / or the second grating are moving. In the second operating mode, during an exposure time of the X-ray detector, the first grating and / or the second grating have moved a distance greater than or equal to the period of the first grating and / or the second grating. In the second operating mode, the image data is acquired while the first grating and / or the second grating are moving. In the second operating mode, the output unit is configured to output attenuation image data and / or calibration data.

[0102] In other words, the system operates as a DAX system in the first mode, where the moiré fringes on the detector are used to generate dark field, phase contrast and, in effect, attenuation data, but now in the second mode, the fringe pattern (where the grating is still positioned in the beam) is washed out and the system operates in a "normal" attenuation mode, providing a calibration function.

[0103] In other words, moving one or both of the gratings by at least this distance causes the fringes on the detector required for the DAX system to be washed out. Thus, in one mode of operation, the system operates continuously to acquire data in a grating-based phase contrast and dark field measurement system with the moving grating(s), and in a second mode, the system operates as a conventional attenuation imaging X-ray system providing system characterization and calibration without the need to remove the gratings from the beam path.

[0104] The movement of the grating in the second mode may be intrinsic, such as by vibration of the grating at a primary or resonant frequency, or provided intentionally via a moving or vibrating transducer.

[0105] In an example, the vibration transducer may always operate in both a first mode and a second mode, wherein the detector exposure time in the first mode is less than the detector exposure time in the second mode.

[0106] According to an example, for the second operating mode, the control unit is configured to control the movement of the first grating and / or the second grating so that the image data is acquired while the first grating and / or the second grating is moving.

[0107] According to an example, the movement of the first and / or second grating during the exposure time comprises a movement caused by at least one vibration transducer 80 controlled by the control unit. The at least one vibration transducer is configured to vibrate the first and / or second grating.

[0108] In an example, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating, wherein the vibration has an amplitude greater than 10 μm.

[0109] Therefore, to make a calibration measurement without a moiré pattern but with all gratings in the beam path, a transducer is used to add high-frequency and "large" (i.e., tens of μm) amplitude vibrations to one or more of the gratings. This erases all moiré fringes from the measurement, because even though the exposure time can be very short, with the additional vibration frequency and amplitude, the fringe movement results in extreme pattern blurring.

[0110] Thus, in the second mode, the detector exposure time can be greater than that of the first mode, wherein, in the first mode, the grating(s) were moved at a specific speed that enabled moiré fringes to be detected. Now, in the second mode with a longer exposure time, the fringes are washed out because the grating(s) are now moved further, enabling attenuation data and / or calibration data to be acquired. However, by introducing vibrations to the grating(s) in the second mode, the gratings move further in the second mode than in the first mode, and the detector can have the same exposure time in both modes, thereby providing simplified detector electronics and processing. However, in both cases, now in the second mode, the fringe pattern visible in the first mode is now erased, leaving a normal attenuation image that can be used for calibration purposes or provided as a useful attenuation image in its own right.

[0111] According to an example, for the second operating mode, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

[0112] Thus, for example, a laterally moving transducer that operates in a first mode to enable acquisition of darkfield and phase contrast data can be operated in a second mode, wherein, for example, movement at a particular speed that was acceptable in the first mode due to a small exposure time now results in washout of fringes due to a longer exposure time. Alternatively, the transducer can be operated differently in the second mode than in the first mode, wherein it imparts a faster movement and / or vibration of the grating in the second mode relative to the first mode, such that, for a constant exposure time between modes, fringes that were visible in the first mode are washed out or erased in the second mode.

[0113] According to an example, the exposure time of the first operating mode is equal to the exposure time in the second operating mode.

[0114] According to an example, for the second operating mode, the control unit is configured to control the X-ray detector such that the exposure time is greater than a time period of a resonance frequency of the first grating and / or the second grating.

[0115] With reference to the above-described system for acquiring dark field and phase contrast data with associated attenuation data, the system can be operated solely to acquire attenuation data and / or calibration data by washing out moiré fringes. Thus, an example system for acquiring attenuation images and / or calibration data includes an X-ray source 20, an interferometer arrangement 30, an X-ray detector 40, a control unit 50, and an output unit 60. An axis is defined extending from the center of the X-ray source to the center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector. The axis extends through the examination region, and the examination region is configured to enable positioning of an object to be examined. The interferometer arrangement is located between the X-ray source and the X-ray detector. The interferometer arrangement includes a first grating 32 and a second grating 34. The control unit is configured to control the X-ray detector to acquire image data while the first grating and / or the second grating are moving. During an exposure time of the X-ray detector, the first grating and / or the second grating have moved a distance greater than or equal to the period of the first grating and / or the second grating. The output unit is configured to output attenuation image data and / or calibration data.

[0116] In an example of a system for attenuation image and / or calibration data acquisition, the control unit is configured to control the movement of the first grating and / or the second grating so that the image data is acquired while the first grating and / or the second grating is moving.

[0117] In an example of a system for attenuation image and / or calibration data acquisition, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by at least one vibration transducer 80 controlled by the control unit, wherein the at least one vibration transducer is configured to vibrate the first grating and / or the second grating.

[0118] In an example of the system for attenuation image and / or calibration data acquisition, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating, wherein the vibration has an amplitude greater than 10 μm.

[0119] In an example of the system for attenuation image and / or calibration data acquisition, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer 70. The control unit is configured to control the at least one transverse movement transducer to move the first grating or the second grating in a transverse position direction perpendicular to the axis.

[0120] In an example of the system for attenuation image and / or calibration data acquisition, the control unit is configured to control the X-ray detector such that the exposure time is greater than a time period of a resonance frequency of the first grating and / or the second grating.

[0121] Figure 2 An example of a method 100 for X-ray dark field, phase contrast and attenuation image acquisition is shown in its basic steps. The method 100 comprises:

[0122] In an orientation step 110 , also referred to as step a), the X-ray source 20 is oriented relative to the X-ray detector 40 to define an axis extending from the center of the X-ray source to the center of the X-ray detector;

[0123] In a positioning step 120 , also referred to as step b), an examination region is positioned between the X-ray source and the X-ray detector, wherein the first axis extends through the examination region and wherein the examination region is configured to enable positioning of an object to be examined;

[0124] In a positioning step 130 , also referred to as step c), an interferometer device 30 is positioned between the X-ray source and the X-ray detector, wherein the interferometer device comprises a first grating 32 and a second grating 34 ;

[0125] In the first operating mode:

[0126] - in a control step 140 also referred to as step d), at least one transverse movement transducer 70 is controlled by the control unit 50 to move the first grating or the second grating in a transverse position direction perpendicular to the axis;

[0127] - in a control step 150, also referred to as step e), the X-ray detector is controlled by the control unit to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating has moved a distance that is smaller than a period of the first grating and / or the second grating, and wherein the control unit controls the movement of the first grating and / or the second grating such that the image data are acquired while the first grating and / or the second grating are moving; and

[0128] In an outputting step 160 , also referred to as step g), one or more of the following are outputted by the output unit 60 : dark field image data, phase contrast image data and attenuation image data.

[0129] In an example, for the first operating mode, the method comprises controlling, by the control unit, the X-ray detector such that the exposure time is smaller than a time period of a resonance frequency of vibration of the first grating and / or the second grating.

[0130] In an example, in step e), the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

[0131] In an example, in step e), the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by movement of the at least one transverse motion transducer in the transverse position direction as part of an image acquisition protocol.

[0132] Thus, in an example, steps d) and e) may occur simultaneously.

[0133] According to an example, the method comprises, in the second operating mode, a step f) of controlling 170 the X-ray detector by the control unit to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating has moved a distance greater than or equal to a period of the first grating and / or the second grating. The method further comprises a step h) of outputting 180 the attenuation image data and / or the calibration data by the output unit in the second operating mode.

[0134] In an example, step f) comprises controlling, by the control unit, movement of the first grating and / or the second grating such that the image data is acquired while the first grating and / or the second grating is moving.

[0135] In an example, in step f), controlling the movement of the first grating and / or the second grating during the exposure time comprises controlling, by the control unit, at least one vibration transducer 80 to vibrate the first grating and / or the second grating.

[0136] In an example, step f) comprises vibrating the first grating and / or the second grating by the at least one vibration transducer, wherein the vibration has an amplitude greater than 10 μm.

[0137] In an example, step f) comprises moving the first grating and / or the second grating by the at least one transverse movement transducer during the exposure time.

[0138] In an example, the exposure time in step e) is equal to the exposure time in step f).

[0139] In an example, step f) comprises controlling the X-ray detector by the control unit such that the exposure time is greater than a time period of a resonance frequency of the first grating and / or the second grating.

[0140] With reference to the above-described method for acquiring darkfield and phase contrast data with associated attenuation data, the method may be operable to acquire attenuation data and / or calibration data solely by washing out the moiré fringes. Thus, examples of methods for attenuation image and / or calibration data acquisition include:

[0141] - in an orientation step 110 , also referred to as step a), orienting the X-ray source 20 relative to the X-ray detector 40 so as to define an axis extending from the center of said X-ray source to the center of said X-ray detector;

[0142] - in a positioning step 120 , also referred to as step b), positioning an examination region between the X-ray source and the X-ray detector, wherein the first axis extends through the examination region and wherein the examination region is configured to enable positioning of an object to be examined;

[0143] - in a positioning step 130 , also referred to as step c), positioning an interferometer device 30 between the X-ray source and the X-ray detector, wherein the interferometer device comprises a first grating 32 and a second grating 34 ;

[0144] - in a control step 170, also referred to as step f), the X-ray detector is controlled by the control unit to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating has moved a distance greater than or equal to a period of the first grating and / or the second grating; and

[0145] In an output step 180 , referred to as step h), the attenuation image data and / or the calibration data are output by the output unit.

[0146] In an example, step f) comprises controlling, by the control unit, movement of the first grating and / or the second grating such that the image data is acquired while the first grating and / or the second grating is moving.

[0147] In an example, in step f), controlling the movement of the first grating and / or the second grating during the exposure time comprises controlling, by the control unit, at least one vibration transducer 80 to vibrate the first grating and / or the second grating.

[0148] In an example, step f) comprises vibrating the first grating and / or the second grating by the at least one vibration transducer, wherein the vibration has an amplitude greater than 10 μm.

[0149] In an example, step f) comprises moving the first grating and / or the second grating by at least one transverse movement transducer during the exposure time, wherein the control unit is configured to control the at least one transverse movement transducer to move the first grating or move the second grating in a transverse position direction perpendicular to the axis.

[0150] In an example, step f) comprises controlling the X-ray detector by the control unit such that the exposure time is greater than a time period of a resonance frequency of the first grating and / or the second grating.

[0151] As discussed above, regarding Figure 1-2In the new imaging modality, the inter-grating movement required for a step curve can be determined while one or more of the gratings is moving, and X-ray dark field and phase contrast information (along with normal attenuation information) can be determined based on the step curve. Therefore, while reference is made to a step curve here, the gratings do not need to be stepped; they never need to be intentionally stopped. This is achieved by moving the gratings and reducing the blurring effect by reducing the exposure time. The exposure time must be short enough that the grating movement during a single exposure is effectively negligible, or at least does not wash out fringes. This can be ensured when the exposure time is significantly shorter than the period of the grating's primary vibration frequency. Grating vibration can be inherent to the system or induced externally, such as by a vibrating transducer. However, the system can be operated to obtain X-ray attenuation data and / or normal X-ray attenuation data without having to move the interferometer assembly out of the beamline. This is accomplished if the grating movement or vibration is sufficiently large to wash out moiré fringes. The movement can be performed as part of image acquisition to acquire data for dark field, phase contrast, and associated attenuation data, and / or the movement can be due to vibration. The vibration of the grating can be intrinsic to the system or induced externally, for example by a vibrating transducer. To perform a calibration measurement without a moiré pattern but with all gratings in the beam path, a transducer is used to add high-frequency and "large" (i.e., tens of μm) amplitude vibrations to the gratings. This removes any moiré fringes from the measurement, because even if the exposure time can be very short, with the additional vibration frequency and amplitude, the fringe movement results in extreme pattern blurring.

[0152] However, there is another new way to wash out moiré fringes, as now Figure 3-6 discussed.

[0153] Figure 3 An example of a system 1010 for X-ray dark field, phase contrast, and attenuation image acquisition is shown. The system includes an X-ray source 1020, an interferometer arrangement 1030, an X-ray detector 1040, a control unit 1050, at least one vibration transducer 1080, a processing unit 1090, and an output unit 1060. An axis is defined extending from the center of the X-ray source to the center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector. The axis extending from the center of the X-ray source to the center of the X-ray detector also extends through the examination region, and the examination region is configured to enable positioning of an object to be examined. The interferometer arrangement is located between the X-ray source and the X-ray detector, and the interferometer arrangement includes a first grating 1032 and a second grating 1034.

[0154] For the first operating mode:

[0155] The control unit is configured to control at least one transverse movement transducer 1070 to move the first grating or the second grating in a transverse position direction perpendicular to the axis. The control unit is also configured to control the X-ray detector to collect image data when the first grating and / or the second grating are moving. During the exposure time of the X-ray detector, the first grating and / or the second grating has moved a distance less than the period of the first grating and / or the second grating. The control unit is configured to control the movement of the first grating and / or the second grating so that the image data is collected when the first grating and / or the second grating are moving. The output unit is configured to output one or more of the following: dark field image data, phase contrast image data, and attenuation image data.

[0156] For the second operating mode:

[0157] The control unit is configured to control the X-ray detector to acquire each of a plurality of image data when the first grating and / or the second grating moves during an exposure time of the X-ray detector. The control unit is configured to control the at least one vibration transducer 1080 to vibrate the first grating and / or the second grating. The amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating. The processing unit is configured to generate attenuation image data and / or calibration data, including determining a temporal low-pass filtered version of at least some of the plurality of image data. The output unit is configured to output the attenuation image data and / or the calibration data.

[0158] In an example, the movement of the first grating in a lateral position direction perpendicular to the axis or the movement of the second grating in a lateral position direction perpendicular to the axis is also perpendicular to the grating lines in the grating.

[0159] In an example, the first grating is located between the second grating and the X-ray source.

[0160] In an example, the examination region is located between the first grating and the X-ray source.

[0161] In an example, the interferometer device includes three gratings, wherein a source grating is positioned to interact with the X-rays emitted from the source and serves to increase the coherence of the X-rays propagating through the interferometer device. Thus, in the absence of a source grating, there may be two gratings, wherein the first grating is closest to the source and is an absorption grating or a phase grating, and the second grating is closest to the detector and is an absorption grating. However, in the case of three gratings, the source grating closest to the source may be the first grating, and either of the other two gratings may be the second grating, or the upper grating that may be an absorption grating or a phase grating may be the first grating, and so on.

[0162] In an example, the first grating is an absorption grating and the second grating is an absorption grating. In an example, the first grating is a phase grating and the second grating is an absorption grating.

[0163] According to an example, for the first operating mode, the control unit is configured to control the X-ray detector such that the exposure time is smaller than a time period of a resonance frequency of vibration of the first grating and / or the second grating.

[0164] According to an example, for the first operating mode, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

[0165] In an example, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by movement of the at least one transverse motion transducer in the transverse position direction as part of an image acquisition protocol.

[0166] According to an example, in the second operating mode, the applying of the low-pass filtering comprises determining an average of at least some of the plurality of image data.

[0167] In an example, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating, wherein the vibration has an amplitude greater than 10 μm.

[0168] Therefore, to perform calibration measurements without a moiré pattern but with all gratings in the beam path, a transducer is used to add high-frequency and "large" (i.e., tens of μm) amplitude vibrations to one or more of the gratings. Averaging the acquired data for each focus position results in all moiré fringes being erased from the measurement, because even though the exposure time can be very short, with the additional vibration frequency and amplitude, the fringe movement between images results in extreme pattern blurring. This blurring is further increased by low-pass filtering the image data.

[0169] In an example, the exposure time of the first operating mode is equal to the exposure time in the second operating mode.

[0170] According to an example, the low-pass filtering comprises a low-pass filter kernel having a length greater than a vibration period of the first grating and / or the second grating.

[0171] According to an example, for the second operating mode, the control unit is configured to control the X-ray source to periodically move the focus on the target to N different target positions, and wherein the control unit is configured to control the X-ray detector to collect image data for each of the N target positions separately, so that at least some of the multiple image data are related to one focal target position; and wherein the control unit is configured to control the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector.

[0172] Figure 4 A method 1100 for X-ray dark field, phase contrast, and attenuation image acquisition is shown in its basic steps. The method comprises:

[0173] - in an orientation step 1110 , also referred to as step a), orienting the X-ray source 1020 relative to the X-ray detector 1040 so as to define an axis extending from the center of said X-ray source to the center of said X-ray detector;

[0174] - in a positioning step 1120 , also referred to as step b), positioning an examination region between the X-ray source and the X-ray detector, wherein the first axis extends through the examination region and wherein the examination region is configured to enable positioning of an object to be examined;

[0175] - in a positioning step 1130 , also referred to as step c), positioning an interferometer device 1030 between the X-ray source and the X-ray detector, wherein the interferometer device comprises a first grating 1032 and a second grating 1034 ;

[0176] In the first operating mode:

[0177] - in a control step 1140 also referred to as step d), at least one transverse movement transducer 1070 is controlled by the control unit 1050 to move the first grating or the second grating in a transverse position direction perpendicular to the axis;

[0178] - in a control step 1150, also referred to as step e), the X-ray detector is controlled 1150 by the control unit to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating has moved a distance that is smaller than a period of the first grating and / or the second grating, and wherein the control unit controls the movement of the first grating and / or the second grating such that the image data are acquired while the first grating and / or the second grating are moving; and

[0179] - in an outputting step 1160 , also referred to as step f), outputting by the output unit ( 1060 ) one or more of: dark field image data, phase contrast image data and attenuation image data;

[0180] - In the second operating mode:

[0181] - in a control step 1170, also referred to as step g), controlling the X-ray detector by the control unit to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector;

[0182] - in a control step 1180, also referred to as step h), the control unit controls at least one vibration transducer 1080 to vibrate the first grating and / or the second grating, wherein the amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating;

[0183] - in a generating step 1190 , also referred to as step i), generating, by the processing unit, attenuated image data and / or calibration data, comprising determining a temporally low-pass filtered version of at least some of the plurality of image data; and

[0184] In an output step 1200 , also referred to as step j), the attenuation image data and / or the calibration data are output by the output unit.

[0185] In an example, for the first operating mode, the method comprises controlling, by the control unit, the X-ray detector such that the exposure time is smaller than a time period of a resonance frequency of vibration of the first grating and / or the second grating.

[0186] In an example, in step e), the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

[0187] In an example, in step e), the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by movement of the at least one transverse motion transducer in the transverse position direction as part of an image acquisition protocol.

[0188] Thus, in an example, steps d) and e) may occur simultaneously.

[0189] In an example, step h) comprises vibrating the first grating and / or the second grating by the at least one vibration transducer, wherein the vibration has an amplitude greater than 10 μm.

[0190] In an example, the exposure time in step e) is equal to the exposure time in step h).

[0191] In an example, step i) comprises determining an average of at least some of the plurality of image data.

[0192] In an example, the low-pass filtering comprises a low-pass filter kernel having a length greater than a vibration period of the first grating and / or the second grating.

[0193] In an example, step g) includes controlling the X-ray source by the control unit to periodically move the focus on the target to N different target positions, and wherein the control unit is configured to control the X-ray detector to acquire image data for each of the N target positions separately, so that at least some of the multiple image data are related to one focal target position; and wherein step h) controls the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector, so that the exposure time is greater than the time period of the resonant frequency of the first grating and / or the second grating.

[0194] Figure 5An example of a system 2000 for acquiring attenuation images and / or calibration data is shown. The system includes an X-ray source 1020, an interferometer arrangement 1030, an X-ray detector 1040, a control unit 1050, at least one vibration transducer 1080, a processing unit 1090, and an output unit 1060. An axis is defined extending from the center of the X-ray source to the center of the X-ray detector. An examination region is located between the X-ray source and the X-ray detector. The axis extending from the center of the X-ray source to the center of the X-ray detector also extends through the examination region, and the examination region is configured to enable positioning of an object to be examined. Thus, the examination region is positioned such that an object can be positioned therein for detection. The interferometer arrangement is located between the X-ray source and the X-ray detector and includes a first grating 1032 and a second grating 1034. The control unit is configured to control the X-ray detector to acquire each of a plurality of image data as the first grating and / or the second grating move during an exposure time of the X-ray detector. The control unit is configured to control the at least one vibration transducer 1080 to vibrate the first grating and / or the second grating. The amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating. The processing unit is configured to generate attenuation image data and / or calibration data, including determining a temporally low-pass filtered version of at least some of the plurality of image data. The output unit is configured to output the attenuation image data and / or the calibration data.

[0195] In an example, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating, wherein the vibration has an amplitude greater than 10 μm.

[0196] According to an example, the applying of the low pass filtering comprises determining an average of at least some of the plurality of image data.

[0197] According to an example, the low-pass filtering comprises a low-pass filter kernel having a length greater than a vibration period of the first grating and / or the second grating.

[0198] According to an example, the control unit is configured to control the X-ray source to periodically move the focus on the target to N different target positions, and wherein the control unit is configured to control the X-ray detector to acquire image data for each of the N target positions separately; and wherein the control unit is configured to control the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector

[0199] Figure 6An example of a method 3000 for attenuation image and / or calibration data acquisition is shown in its basic steps. The method comprises:

[0200] - in a positioning step 3110, also referred to as step a), the X-ray source 1020 is positioned relative to the X-ray detector 1040 so as to define an axis extending from a center of the X-ray source to a center of the X-ray detector, wherein an examination region is located between the X-ray source and the X-ray detector, wherein the first axis extends through the examination region, wherein the examination region enables positioning of an object to be examined, and wherein an interferometer device 1030 is located between the X-ray source and the X-ray detector, wherein the interferometer device comprises a first grating 1032 and a second grating 1034;

[0201] - in a control step 3120, also referred to as step b), controlling the X-ray detector by the control unit to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector;

[0202] - in a control step 3130, also referred to as step c), the at least one vibration transducer 1080 is controlled by the control unit to vibrate the first grating and / or the second grating, wherein the amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating;

[0203] - in a generating step 3140 , also referred to as step d), generating, by the processing unit 1090 , attenuated image data and / or calibration data, comprising determining a temporally low-pass filtered version of at least some of the plurality of image data; and

[0204] In an output step 3150 , also referred to as step e), the attenuation image data and / or the calibration data are output by the output unit.

[0205] In an example, step b) comprises vibrating the first grating and / or the second grating by the at least one vibration transducer, wherein the vibration has an amplitude greater than 10 μm.

[0206] According to an example, step d) comprises determining an average of said at least some of said plurality of image data.

[0207] In an example, the low-pass filtering comprises a low-pass filter kernel having a length greater than a vibration period of the first grating and / or the second grating.

[0208] In an example, step b) includes controlling the X-ray source by the control unit to periodically move the focus on the target to N different target positions, and wherein the control unit controls the X-ray detector to acquire image data for each of the N target positions respectively; and wherein step c) includes controlling the control unit to control the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector.

[0209] Therefore, reference Figure 3-6 For the acquisition of calibration data and / or the attenuation image itself, fringe patterns are eliminated by a combination of two techniques. The first involves applying an oscillation to at least one of the gratings, with an amplitude at least equal to the grating period. This ensures that the fringe pattern oscillates through at least 360°. The second element involves averaging the detector readings for each focus position. Specifically, for a four-focus acquisition, in which the focus of the X-ray tube is periodically moved between four different positions on the anode, the signal at each focus position is temporally low-pass filtered. Some specific further details are:

[0210] The size of the low-pass kernel should be large enough to capture at least one cycle of the main vibration frequency.

[0211] If the detector integration period is T, then the detector's Nyquist frequency is 1 / 2T. However, for quad focal acquisition, only every fourth readout is used on average. Therefore, the oscillation frequency should be much lower than 2 / T to avoid aliasing issues.

[0212] For example, calibration information can be obtained by placing different homogeneous materials into the beam during calibration measurements.

[0213] refer to Figure 7-8 Aspects of the new imaging modality are further explained.

[0214] Figure 7 An example of the interferometer portion of a system that can acquire X-ray phase contrast, dark field and attenuation image data is shown. References to the interferometer device above refer only to the gratings of the interferometer portion of the system. The system is capable of imaging the spatial distribution of attenuation of or in a sample, as well as imaging the spatial distribution of refraction (phase contrast imaging), and also imaging the spatial distribution of small angle scattering (dark field imaging). The system has a grating-based interferometer. In this example, the interferometer includes two grating structures G1 and G2, but in other examples a three-grating interferometer (with gratings G0, G1 and G2) is used, in which a source grating G0 close to the source is used to increase the coherence of the radiation propagating through the sample and the G1 grating and the G2 grating.

[0215] exist Figure 7In FIG, the source grating G0 is not shown, and the following discussion considers two grating structures G1 and G2, but all three gratings G0, G1 and G2 may be present, and wherein G0 may be a laterally shifted grating. Figure 7 In the figure, grating G1 is a phase grating (but can also be an absorption grating), and G2 is an absorption grating. The system also includes an X-ray source and an X-ray detector. The X-ray detector (here shown as a CCD detector) can be a 2D full-view X-ray detector, which is either planar or curved. A plurality of detector pixels are arranged in an array in rows and columns to form a 2D X-ray radiation sensitive surface capable of recording X-ray radiation emitted by the X-ray source. The X-ray detector and the X-ray source are spaced apart to form an examination area. The examination area is appropriately spaced apart to receive a sample to be imaged. The sample can be, for example, a patient's breast or a patient's chest in order to examine the lungs. Either G1 or G2 can be curved or flat, but even if curved, can define a plane parallel to the center of the grating. The system has a transducer that moves the grating laterally, and can also have a vibrating transducer that vibrates one of the gratings.

[0216] The sample then modulates attenuation, refraction and small-angle scattering information onto the radiation, which can then be extracted by the operation of the tandem gratings G1 and G2. The gratings G1, G2 induce an interference pattern that can be detected as fringes of a moiré pattern at the X-ray detector. If there is no object in the examination region, an interference pattern (called a reference pattern, which is usually captured during a calibration procedure) can still be observed at the X-ray detector. This is achieved by specifically adjusting or "detuning" the mutual spatial relationship between the two gratings G1 and G2, causing, for example, a slight bend, so that the two gratings are not completely parallel. Now, if a sample is positioned in the examination region and interacts with the radiation mentioned above, the moiré pattern (which is now more properly called a sample pattern) can be understood as a perturbed version of the reference pattern.

[0217] In order to separate this phase information from other contributions to the signal (e.g. attenuation due to the sample, inhomogeneous illumination or grating defects), a modified phase stepping method is used. g (like Figure 3 One of the gratings (G1 or G2 or G0, if present) is scanned (as shown) and an image is taken for each point of the scan, and the image data is collected while the grating is moving, wherein the detector exposure time is such that the moiré fringes are not washed out. If a source grating G0 is present, it can be this grating that is scanned in the transverse direction. The resulting phase contrast, dark field and attenuation data are then sinusoidally oscillated with and without the sample, as shown in FIG. Figure 8, shown for phase contrast (A), dark field (B) and attenuation (C). Further details on the standard phase stepping method can be found in the article by Weitkamp et al. (Optics Express, Vol. 13, No. 16, pp. 6296-6304 (2005)).

[0218] However, for the presently described system, another operating mode is utilized to obtain X-ray calibration data or normal attenuation data. The grating being moved as described above can be moved in the same manner by laterally moving the transducer, but the detector exposure time can be increased to wash out the fringes. Furthermore, the movement speed can be increased within a constant detector exposure time. As will be readily appreciated, there are combinations of movement speed and exposure time that result in the fringes being washed out. However, another way to wash out the fringes is simply to increase the exposure time to a duration at which the fringes disappear as a result of the system's inherent vibrations. These vibrations can be enhanced by laterally vibrating the grating using a vibrating transducer, so that the moiré fringes are washed out for the detector exposure time used.

[0219] Furthermore, using a different technique, the system can be used to acquire X-ray calibration data or normal attenuation data while the gratings remain in place. This technique vibrates the gratings, which do not need to move much or at all during image acquisition. However, the amplitude of the vibration is sufficient to allow the combination of multiple images in conjunction with low-pass filtering. However, at least one grating has now been moved from at least one previous image acquisition position, allowing the fringes that would otherwise be present to be washed out or removed. This results in data that can be used for calibration purposes or simply as a normal attenuation image.

[0220] In a further exemplary embodiment, a computer program or a computer program element is provided, characterized in that it is configured to execute the method steps of the method according to one of the preceding embodiments on a suitable system.

[0221] Thus, a computer program element may be stored in a computer unit, which may also be part of an embodiment. The computer unit may be configured to perform the steps of the above-described method or cause the steps of the above-described method to be performed. Furthermore, it may be configured to operate components of the above-described apparatus and / or system. The computer unit may be configured to operate automatically and / or execute user commands. The computer program may be loaded into a working memory of a data processor. Thus, the data processor may be equipped to perform a method according to one of the aforementioned embodiments.

[0222] This exemplary embodiment of the invention covers both a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention.

[0223] Furthermore, the computer program element can provide all necessary steps for implementing the procedures of an exemplary embodiment of the method as described above.

[0224] According to a further exemplary embodiment of the present invention, a computer-readable medium, such as a CD-ROM, USB stick or the like, is proposed, wherein the computer-readable medium has a computer program element stored on the computer-readable medium, the computer program element being described by the preceding section.

[0225] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or solid-state medium provided together with or as part of other hardware, but the computer program may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0226] However, the computer program may also be present on a network such as the World Wide Web and be downloadable from such a network into the working memory of a data processor. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, wherein the computer program element is arranged to perform a method according to one of the previously described embodiments of the present invention.

[0227] It should be noted that embodiments of the present invention are described with reference to different subject matters. Specifically, some embodiments are described with reference to method-type claims, while other embodiments are described with reference to apparatus-type claims. However, those skilled in the art will appreciate from the above and following descriptions that, unless otherwise indicated, any combination of features relating to different subject matters, in addition to any combination of features belonging to one type of subject matter, is also considered disclosed by this application. However, all features can be combined to provide synergistic effects that exceed the simple sum of the features.

[0228] Although the present invention has been described and illustrated in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention from a study of the drawings, the description, and the appended claims.

[0229] In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A system for X-ray dark field, phase contrast, and attenuation image acquisition, the system comprising: X-ray source; interferometer device; X-ray detectors; control unit; at least one vibration transducer; processing unit; as well as Output unit; wherein an axis is defined as extending from the center of the X-ray source to the center of the X-ray detector; wherein an examination region is located between the X-ray source and the X-ray detector, wherein the axis extends through the examination region, and wherein the examination region is configured to enable positioning of an object to be examined; wherein the interferometer device is located between the X-ray source and the X-ray detector, and wherein the interferometer device comprises a first grating and a second grating; Among them, for the first operation mode: The control unit is configured to control at least one transverse movement transducer to move the first grating or the second grating in a transverse position direction perpendicular to the axis; and wherein the control unit is configured to control the X-ray detector to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating has moved a distance that is less than a period of the first grating and / or the second grating, and wherein the control unit is configured to control the movement of the first grating and / or the second grating so that the image data is acquired while the first grating and / or the second grating are moving; and Wherein, for the first operation mode, the output unit is configured to output one or more of the following: dark field image data, phase contrast image data, and attenuation image data; Among them, for the second operation mode: The control unit is configured to control the X-ray detector to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector; The control unit is configured to control the at least one vibration transducer to vibrate the first grating and / or the second grating, wherein an amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating; The processing unit is configured to generate attenuated image data and / or calibration data, including determination of a temporally low-pass filtered version of at least some of the plurality of image data; and Wherein, for the second operation mode, the output unit is configured to output the attenuation image data and / or the calibration data.

2. The system according to claim 1, wherein: For the first operating mode, the control unit is configured to control the X-ray detector so that the exposure time is less than a time period of a resonance frequency of vibration of the first grating and / or the second grating.

3. The system according to claim 1 or 2, wherein: For the first operating mode, the movement of the first grating and / or the second grating during the exposure time comprises a movement caused by the at least one transverse movement transducer.

4. The system according to claim 1 or 2, wherein: In the second mode of operation, the applying of the low pass filtering comprises determining an average of the at least some of the plurality of image data.

5. The system according to claim 4, wherein: The low-pass filtering includes a low-pass filter core having a length greater than a vibration period of the first grating and / or the second grating.

6. The system according to claim 4, wherein: For the second operating mode, the control unit is configured to control the X-ray source to periodically move the focus on the target to N different target positions, and wherein the control unit is configured to control the X-ray detector to collect image data for each of the N different target positions respectively, so that at least some of the multiple image data are related to one focal target position; and wherein the control unit is configured to control the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector.

7. A method for acquiring X-ray dark field, phase contrast, and attenuation images, the method comprising: a) orienting an X-ray source relative to an X-ray detector to define an axis extending from a center of the X-ray source to a center of the X-ray detector; b) positioning an examination region between the X-ray source and the X-ray detector, wherein the axis extends through the examination region, and wherein the examination region is configured to enable positioning of an object to be examined; c) positioning an interferometer arrangement between the X-ray source and the X-ray detector, wherein the interferometer arrangement comprises a first grating and a second grating; d) in a first operating mode, controlling by a control unit at least one transverse movement transducer to move the first grating or the second grating in a transverse position direction perpendicular to the axis; e) in the first operating mode, controlling, by the control unit, the X-ray detector to acquire image data while the first grating and / or the second grating are moving, wherein, during an exposure time of the X-ray detector, the first grating and / or the second grating have moved a distance that is smaller than a period of the first grating and / or the second grating, and wherein the control unit controls the movement of the first grating and / or the second grating such that the image data are acquired while the first grating and / or the second grating are moving; f) outputting, by an output unit, one or more of the following: dark field image data, phase contrast image data, and attenuation image data; g) in a second operating mode, controlling, by the control unit, the X-ray detector to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector; h) in the second operating mode, controlling, by the control unit, at least one vibration transducer to vibrate the first grating and / or the second grating, wherein an amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating; i) in said second mode of operation, generating, by the processing unit, attenuated image data and / or calibration data, comprising determining a temporally low-pass filtered version of at least some of said plurality of image data; and j) Outputting the attenuation image data and / or the calibration data by the output unit.

8. A system for attenuation image and / or calibration data acquisition, the system comprising: X-ray source; interferometer device; X-ray detectors; control unit; at least one vibration transducer; processing unit; as well as Output unit; wherein an axis is defined as extending from the center of the X-ray source to the center of the X-ray detector; wherein an examination region is located between the X-ray source and the X-ray detector, wherein the axis extends through the examination region, and wherein the examination region is configured to enable positioning of an object to be examined; wherein the interferometer device is located between the X-ray source and the X-ray detector, and wherein the interferometer device comprises a first grating and a second grating; wherein the control unit is configured to control the X-ray detector to acquire each of the plurality of image data when the first grating and / or the second grating is moving during an exposure time of the X-ray detector; wherein the control unit is configured to control the at least one vibration transducer to vibrate the first grating and / or the second grating, wherein an amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating; wherein the processing unit is configured to generate the attenuated image data and / or calibration data, including determination of a temporally low-pass filtered version of at least some of the plurality of image data; and Wherein, the output unit is configured to output the attenuation image data and / or the calibration data.

9. The system according to claim 8, wherein: The applying of the low pass filtering includes determining an average of the at least some of the plurality of image data.

10. The system according to claim 9, wherein: The low-pass filtering includes a low-pass filter core having a length greater than a vibration period of the first grating and / or the second grating.

11. The system according to any one of claims 8 to 10, wherein: The control unit is configured to control the X-ray source to periodically move the focus on the target to N different target positions, and wherein the control unit is configured to control the X-ray detector to acquire image data for each of the N different target positions separately; and wherein the control unit is configured to control the at least one vibration transducer so that the vibration frequency is less than N / (2T), wherein T is the exposure time of the X-ray detector.

12. A method for attenuation image and / or calibration data acquisition, the method comprising: a) positioning an X-ray source relative to an X-ray detector to define an axis extending from a center of the X-ray source to a center of the X-ray detector, wherein an examination region is located between the X-ray source and the X-ray detector, wherein the axis extends through the examination region, wherein the examination region enables positioning of an object to be examined, and wherein an interferometer arrangement is located between the X-ray source and the X-ray detector, wherein the interferometer arrangement comprises a first grating and a second grating; b) controlling the X-ray detector by a control unit to acquire each of a plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector; c) controlling, by the control unit, at least one vibration transducer to vibrate the first grating and / or the second grating, wherein an amplitude of the vibration is greater than or equal to a period of the first grating and / or the second grating; d) generating, by a processing unit, attenuated image data and / or calibration data, including determining a temporally low-pass filtered version of at least some of the plurality of image data; and e) Outputting the attenuation image data and / or the calibration data by an output unit.

13. The method of claim 12, step d) comprising determining an average of the at least some of the plurality of image data.

14. A computer program element for controlling a system according to any one of claims 1 to 6, which, when executed by a processor, is configured to perform the method according to claim 7, and / or the computer program element for controlling a system according to any one of claims 8 to 11, which, when executed by a processor, is configured to perform the method according to any one of claims 12 to 13.

15. A computer readable medium having stored thereon a computer program element according to claim 14.

Images