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 extending from a center of the X-ray source to a center of the X-ray detector is defined. An examination region is disposed between the X-ray source and the X-ray detector, the axis extending through the examination region, and the examination region is configured to allow placement of an object to be inspected. The interferometer arrangement is disposed between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating 1032 and a second grating 1034. For a first mode of operation, the control unit is configured to control at least one lateral movement transducer 1070 to move the first grating or the second grating in a lateral 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 move a distance smaller 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 image data is acquired while the first grating and / or the second grating are moving. The output unit is configured to output one or more of dark-field image data, phase-contrast image data, and attenuation image data. For a second mode of operation, the control unit is configured to control the X-ray detector to acquire each image data of the 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 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 calibration data including determinations of the attenuation image data and / or temporally low-pass filtered versions of at least some of the plurality of image data, and the output unit is configured to output the attenuation image data and / or the calibration data.

Description

[Technical Field]

[0001] The present 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 technology]

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

[0003] Grating-based phase contrast (gbPC) X-ray imaging (both fluoroscopy and computed tomography) is a method that offers a new X-ray imaging modality, providing simultaneous images of linear attenuation coefficient, electron density, and small-angle scattering (i.e., images acquired from dark-field signals).

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

[0005] To acquire these new imaging modalities, two or three grating interferometers are introduced into the X-ray beam, which are typically named 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. The gratings G1 and G2 are typically named phase and analyzer gratings. Then, one of the two gratings G1 or G2 is moved in several steps relative to the other grating, perpendicular to the grating lamella (called stepping). If a source grating G0 is used, it can be this grating that is stepped laterally (here, laterally means perpendicular to the grating direction). Images are then recorded for each new grating position. Comparing the image sequences acquired with and without the sample in the beam allows for the calculation of three imaging signals: a transmission or attenuation image (traditional X-ray image), a phase-contrast image, and a dark-field image. To calculate the three imaging signals, at least three images (stepping curves) in the sequence are required. In practice, however, more images are recorded to allow for stable signal extraction. These gratings produce an interference fringe pattern on top of the conventional transmission image, and the dark-field signal is calculated, for example, as the loss of contrast in this fringe pattern.

[0006] Thus, the gbPC system uses a stepping acquisition technique, which means that several projections are combined for one multimodal image. To obtain the stepping curve, one grid is moved to another position between each projection. To ensure good results, care is taken in these settings to minimize grid movement, e.g., vibration, during acquisition. The repeatability and speed of repositioning can be an issue, which always leads to a time gap between two measurements during which the setup is moving and no acquisition is taking place.

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

[0008] Modern X-ray imaging systems are designed for feature sizes several orders of magnitude larger than this fringe pattern; therefore, standard X-ray systems tolerate much more vibration than gbPC setups. To enable the combination of gbPC and conventional CT infrastructure, the implementation must tolerate vibration. Because laboratory gbPC imaging systems were developed in a nearly vibration-free environment, a typical acquisition protocol consists of 5 to 30 exposures with exposure times several seconds long. Repositioning time between exposures is not used; the system must be stopped and come to rest before the next image in the stepping curve image set is acquired. The transition from laboratory to conventional CT stepping techniques addresses both of these points. On the one hand, repositioning time gaps must be shortened to minimize acquisition time. WO 2016 / 177875 A1 discloses an X-ray imaging system capable of faster X-ray acquisition times. 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 the measurement.

[0009] Another problem arises during calibration protocols, such as detector calibration measurements. For these measurements, it is best to remove all gratings from the system. However, this is not always possible, and even if done, it would alter the X-ray leakage and introduce calibration errors. Therefore, accurate calibration data must be acquired to obtain quantitatively accurate images. In conventional CT, highly homogeneous elements, such as thin metal sheets, are placed in the beam to reduce beam leakage, or highly precisely shaped POMs (so-called wedge filters) to shape the beam's intensity profile. The spectral impact of these elements can be calculated analytically thanks to their high precision. Gratings used in new imaging modalities cannot be manufactured with such precision. The current state-of-the-art production process is X-ray LIGA, which combines lithography and electroplating. The grating period can be manufactured with extremely high precision thanks to the high accuracy offered by lithography. On the other hand, filling the grating structure with highly attenuating materials such as gold or bismuth is not sufficiently homogeneous. Field inhomogeneities during electroplating can lead to variations in the grating height, and local defects in the substrate can cause additional gold particles to appear locally on the grating. Finally, due to nonlinear partial volume effects, slight misalignments of the grating in the beam can result in large differences in the overall beam spectrum. 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, measuring the spectral characteristics is hindered by the interference fringe patterns generated by the grating elements. Summary of the Invention [Problem to be solved by the invention]

[0010] A need exists to address these issues.

[0011] It would be advantageous to have an improved system for acquiring dark field, phase contrast and attenuated x-ray image data, and a system for determining calibration data for such systems. [Means for solving the problem]

[0012] The object of the present invention is solved by the subject matter of the independent claims, further embodiments are incorporated in the dependent claims. It is noted that the below-described aspects and embodiments of the present invention 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, a computer program element, and a computer-readable medium.

[0013] In a first aspect, there is provided a system for X-ray dark field, phase contrast and attenuation image acquisition, the system comprising: an X-ray source; an interferometer component; an X-ray detector; a control unit; at least one vibration transducer; a processing unit; Output unit and Equipped with.

[0014] An axis is defined extending from the center of the X-ray source to the center of the X-ray detector. An inspection 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 inspection region. The inspection region is configured (sized, positioned, and accessible) to allow placement of an object to be inspected. An interferometer arrangement is located between the X-ray source and the X-ray detector. The interferometer arrangement includes a first grating and a second grating.

[0015] With respect to the first mode of operation: The control unit is configured to control at least one lateral movement transducer to move the first grating or the second grating in a lateral 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 move a distance smaller 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 such that image data is acquired while the first grating and / or the second grating are moving. The output unit is configured to output one or more of dark-field image data, phase-contrast image data, and attenuation image data.

[0016] Regarding the second mode of operation: The control unit is configured to control the X-ray detector to acquire each image data of the plurality of image data while the first grating and / or the second grating are moving during an exposure time of the X-ray detector. The control unit is configured to control 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 calibration data including the attenuation image data and / or a determination of 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.

[0017] In other words, the X-ray imaging system comprises an interferometer arrangement in which a first grating or a second grating is moved laterally to generate the required stepping curves from which dark field, phase contrast and attenuation image data can be reconstructed, with one or both of these gratings being intentionally moved during image acquisition, made possible by having an exposure time that is short enough so that the movement does not erase the Moiré interference fringes on the detector.

[0018] In this way, "stepping" curve image data, which may require 5-30 separate images at different lateral positions of the first and / or second grid, can be acquired more quickly with reduced x-ray exposure to the patient because the grid can be constantly moving; for example, image data can be acquired as part of a move to the next of the 5-30 different positions. Thus, the grid is not itself stepping and is not statically positioned as the image data is acquired, but is intentionally moving as the image data is acquired, and may, in fact, be constantly moving.

[0019] In other words, the system allows for continuous data acquisition in grating-based phase contrast and dark-field measurements.

[0020] In other words, in the first mode the system is operating as a DAX system, with the Moiré fringes on the detector being used to generate dark field, phase contrast and, in effect, attenuation data, but now in the second mode the fringe pattern is erased, with the grating still positioned in the beam, and the system operates in the normal "attenuation" mode, thereby providing a calibration function.

[0021] In an embodiment, for the first mode of operation, the control unit is configured to control the X-ray detector such that the exposure time is smaller than the time period of the resonant frequency of vibration of the first grating and / or the second grating.

[0022] In this way, in addition to having a short exposure time that allows deliberate movement of the grating without erasing the interference fringe pattern, setup vibrations and repositioning time gaps are also mitigated due to the shortened acquisition time that is part of the system vibration period. The source of vibration may be intrinsic to the system or may be added via an external device such as a vibration transducer.

[0023] Thus, in a first mode of operation, a constantly moving grating is utilized, with blurring effects reduced by shortening the exposure time, which is short enough that 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 grating. Here, a constantly moving grating can mean one or more of the gratings moving in one direction in a continuous linear motion, and can also mean that one or the other or both of the gratings can perform a periodic motion.

[0024] In other words, the system allows continuous data acquisition in grating-based phase contrast and dark-field measurements, and is also tolerant of external vibrations.

[0025] In an embodiment, for the first mode of operation, the movement of the first grating and / or the second grating during the exposure time comprises movement effected by at least one lateral movement transducer.

[0026] Thus, at least one lateral translation transducer can continuously move one or more gratings into position for image data collection for dark field and phase contrast image data acquisition. Whereas previously, grating movement was required to stop while image acquisition was occurring, image acquisition now occurs while the grating is moving between required positions, reducing the overall image acquisition timescale and radiation dose to the patient.

[0027] In an embodiment, in the second mode of operation, applying the low pass filter comprises determining an average of at least some of the plurality of image data.

[0028] In other words, moving one or both of these gratings at least this distance and averaging combined with applying a low-pass filter to the data acquired with the gratings at different positions causes the interference fringes on the detector required for a DAX system to be eliminated in the averaged image. 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 a moving grating, and in a second mode, the system operates as a conventional attenuated imaging X-ray system providing characterization and calibration of the system without the need to remove the grating from the beam path.

[0029] In an embodiment, the low pass filter comprises a low pass filter kernel having a length greater than the period of oscillation of the first grating and / or the second grating.

[0030] In an embodiment, for the second mode of operation, the control unit is configured to control the X-ray source to periodically move a focal spot on the target to N different target locations, the control unit is configured to control the X-ray detector to acquire image data separately for each of the N target locations such that at least some of the plurality of image data are associated with one focal spot target location, and the control unit is configured to control the at least one vibration transducer such that the vibration frequency is less than N / (2T), where T is an exposure time of the X-ray detector.

[0031] In a second aspect, there is provided a method for X-ray dark field, phase contrast and attenuation image acquisition, 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 inspection region between the X-ray source and the X-ray detector, the first axis extending through the inspection region, the inspection region configured to allow placement of an object to be inspected; c) disposing an interferometer arrangement between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating and a second grating; d) in a first mode of operation, controlling by the control unit at least one lateral movement transducer to move the first grating or the second grating in a lateral position direction perpendicular to the axis; e) in a first mode of operation, 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 move a distance that is smaller than the period of the first grating and / or the second grating, and the control unit controls the movement of the first grating and / or the second grating such that image data is acquired while the first grating and / or the second grating are moving; f) in a first mode of operation, outputting, by an output unit, one or more of dark-field image data, phase-contrast image data, and attenuation image data; g) controlling, in a second mode of operation, the X-ray detector by the control unit to acquire each image data of the 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 a second mode of operation, controlling by the control unit at least one vibration transducer to vibrate the first grating and / or the second grating, the amplitude of the vibration being greater than or equal to the period of the first grating and / or the second grating; i) in a second mode of operation, generating, by the processing unit, calibration data comprising determinations of attenuation image data and / or temporally low-pass filtered versions of at least some of the plurality of image data; j) in a second mode of operation, outputting, by an output unit, the attenuation image data and / or the calibration data; It has.

[0032] In a third aspect, there is provided a system for attenuation image and / or calibration data acquisition, the system comprising: an X-ray source; an interferometer component; an X-ray detector; a control unit; at least one vibration transducer; a processing unit; Output unit and Equipped with.

[0033] 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 disposed between the X-ray source and the X-ray detector. The axis defined 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 allow placement of an object to be examined. An interferometer arrangement is disposed between the X-ray source and the X-ray detector. 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 the multiple image data sets while 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 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 calibration data including determinations of the attenuation image data and / or temporally low-pass filtered versions of at least some of the plurality of image data, and the output unit is configured to output the attenuation image data and / or the calibration data.

[0034] Thus, during the acquisition of a single image data set, the grating(s) are intentionally vibrated so that they only need to move a small distance, but from one image data set to the next the grating(s) can be moved further between images, and these images can both be used in combination with low-pass filtering means to eliminate interference fringes that would otherwise be present, leaving data that can be used for calibration purposes or as an attenuation image in its own right, without having to move the grating(s) out of the beam line.

[0035] In an embodiment, applying the low pass filter comprises determining an average of at least some of the plurality of image data.

[0036] In an embodiment, the low pass filter comprises a low pass filter kernel having a length greater than the period of oscillation of the first grating and / or the second grating.

[0037] In an embodiment, the control unit is configured to control the X-ray source to periodically move a focal spot on the target to N different target locations. The control unit is configured to control the X-ray detector to acquire image data separately for each of the N target locations. The control unit is configured to control the at least one vibration transducer such that the vibration frequency is less than N / (2T), where T is the exposure time of the X-ray detector.

[0038] In a fourth aspect, there is provided 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 inspection region is positioned between the X-ray source and the X-ray detector, a first axis extending through the inspection region, the inspection region allowing placement of an object to be inspected, and an interferometer arrangement is positioned between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating and a second grating; b) controlling the X-ray detector by the control unit to acquire each image data of the 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 the amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating; d) generating, by a processing unit, calibration data comprising determinations of attenuation image data and / or temporally low-pass filtered versions of at least some of the image data; e) outputting the attenuation image data and / or the calibration data by an output unit; It has.

[0039] In an embodiment, step d) comprises determining an average of at least some of the plurality of image data.

[0040] According to another aspect, there is provided a computer program element for controlling the system as described above, adapted to perform the steps of the method as described above when executed by a processing unit.

[0041] According to another aspect, a computer readable medium having stored thereon the aforementioned computer elements is provided.

[0042] The computer program element may for example be a software program, but may also be an FPGA, a PLD or any other suitable digital means.

[0043] Advantageously, benefits provided by any of the above aspects apply to all of the other aspects as well, and vice versa.

[0044] The above aspects and examples will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0045] In the following, exemplary embodiments are described with reference to the following drawings: [Brief explanation of the drawings]

[0046] [Figure 1] 1 illustrates a schematic setup of an embodiment of a system for X-ray dark field, phase contrast and attenuation image acquisition. [Figure 2] Illustrates methods for X-ray dark field, phase contrast, and attenuation image acquisition. [Figure 3] 1 illustrates a schematic setup of an embodiment of a system for X-ray dark field, phase contrast and attenuation image acquisition. [Figure 4] Illustrates methods for X-ray dark field, phase contrast, and attenuation image acquisition. [Figure 5] 1 illustrates a schematic setup of an embodiment of a system for attenuation image and / or calibration data acquisition. [Figure 6] 1 illustrates a method for attenuation image and / or calibration data acquisition. [Figure 7] 1 illustrates a schematic setup of an embodiment of a phase contrast, dark field and attenuation imaging system. [Figure 8] 8 illustrates stepping curve data acquired by the imaging system of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0047] FIG. 1 illustrates an embodiment of a system 10 for X-ray dark-field, phase-contrast, and attenuation image acquisition, although not all of the illustrated features are essential, as will be discussed in more detail. In this embodiment, 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 disposed between the X-ray source and the X-ray detector. The axis extends through the examination region, and the examination region is configured to allow placement of an object to be inspected. The interferometer arrangement is disposed 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 mode of operation, the control unit is configured to control at least one lateral movement transducer 70 to move the first grating or the second grating in a lateral position direction perpendicular to the axis. For a first mode of operation, 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 mode of operation, the control unit is configured to move the first grating and / or the second grating a distance smaller than a period of the first grating and / or the second grating during an exposure time of the X-ray detector. The control unit is configured to control the movement of the first grating and / or the second grating such that image data is acquired while the first grating and / or the second grating are moving. For the first mode of operation, the output unit is configured to output one or more of dark-field image data, phase-contrast image data, and attenuation image data.

[0048] In other words, the X-ray imaging system comprises an interferometer arrangement in which a first grating or a second grating is moved laterally to generate the required stepping curves from which dark field, phase contrast and attenuation image data can be reconstructed, with one or both of these gratings being intentionally moved during image acquisition, made possible by having an exposure time that is short enough so that the movement does not erase the Moiré interference fringes on the detector.

[0049] In this way, "stepping" curve image data, which may require 5-30 separate images at different lateral positions of the first and / or second grid, can be acquired more quickly with reduced x-ray exposure to the patient because the grid can be constantly moving; for example, image data can be acquired as part of a move to the next of the 5-30 different positions. Thus, the grid is not itself stepping and is not statically positioned as the image data is acquired, but is intentionally moving as the image data is acquired, and may, in fact, be constantly moving.

[0050] In other words, the system allows for continuous data acquisition in grating-based phase contrast and dark-field measurements.

[0051] In an embodiment, the movement of the first grating or the movement of the second grating in a lateral position direction perpendicular to the axis is also perpendicular to the grating lines of the grating.

[0052] In an embodiment, the first grating is positioned between the second grating and the X-ray source.

[0053] In an embodiment, the examination region is located between the first grating and the X-ray detector.

[0054] In an embodiment, the interferometer arrangement comprises three gratings, the source grating being positioned to interact with X-rays emitted from the source, the source grating acting to increase the coherence of X-rays propagating through the interferometer arrangement. Thus, if there is no source grating, there may be two gratings, the first closest to the source being an absorption grating or a phase grating, and the second closest to the detector being an absorption grating. However, if there are 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 grating, which may be an absorption grating or a phase grating, may be the first grating, etc.

[0055] In an embodiment, the first grating is an absorption grating and the second grating is an absorption grating.In an embodiment, the first grating is a phase grating and the second grating is an absorption grating.

[0056] According to an embodiment, for the first mode of operation, the control unit is configured to control the X-ray detector such that the exposure time is smaller than the time period of the resonant frequency of vibration of the first grating and / or the second grating.

[0057] In this way, in addition to having a short exposure time that allows deliberate movement of the grating without erasing the interference fringe pattern, setup vibrations and repositioning time gaps are also mitigated due to the shortened acquisition time that is part of the system vibration period. The source of vibration may be intrinsic to the system or may be added via an external device such as a vibration transducer.

[0058] Thus, in a first mode of operation, a constantly moving grating is utilized, with blurring effects reduced by shortening the exposure time, which is short enough that 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 grating. Here, a constantly moving grating can mean one or more of the gratings moving in one direction in a continuous linear motion, and can also mean that one or the other or both of the gratings can perform a periodic motion.

[0059] In other words, the system allows continuous data acquisition in grating-based phase contrast and dark-field measurements, and is also tolerant of external vibrations.

[0060] According to an embodiment, for the first mode of operation, the movement of the first grating and / or the second grating during the exposure time comprises a movement effected by at least one lateral movement transducer.

[0061] Thus, at least one lateral translation transducer can continuously move one or more gratings into position for image data collection for dark field and phase contrast image data acquisition. Whereas previously, grating movement was required to stop while image acquisition was occurring, image acquisition now occurs while the grating is moving between required positions, reducing the overall image acquisition timescale and radiation dose to the patient.

[0062] According to an embodiment, the movement of the first grating and / or the second grating during the exposure time comprises movement effected by at least one lateral movement transducer in a lateral position direction as part of the image acquisition protocol.

[0063] According to an embodiment, for a second mode of operation, 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 second mode of operation, during an exposure time of the X-ray detector, the first grating and / or the second grating move a distance greater than or equal to a period of the first grating and / or the second grating. For the second mode of operation, the image data is acquired while the first grating and / or the second grating are moving. For the second mode of operation, the output unit is configured to output the attenuation image data and / or the calibration data.

[0064] In other words, in the first mode the system is operating as a DAX system, with the Moiré fringes on the detector being used to generate dark field, phase contrast and, in effect, attenuation data, but now in the second mode the fringe pattern is erased, with the grating still positioned in the beam, and the system operates in the normal "attenuation" mode, thereby providing a calibration function.

[0065] In other words, moving one or both of these gratings at least this distance results in the cancellation of interference fringes on the detector, which is required for a DAX system. Thus, in one mode of operation, the system operates continuously to acquire data in a grating-based phase contrast and dark field metrology system with a moving grating, and in a second mode, the system operates as a conventional attenuated imaging X-ray system, providing characterization and calibration of the system without the need to remove the grating from the beam path.

[0066] The movement of the grating in the second mode may be intrinsic, such as through a dominant or resonant frequency vibration of the grating, or may be intentionally provided via a movement or vibration transducer.

[0067] In an embodiment, the vibration transducer may operate constantly in both the first mode and the second mode, with the detector exposure time in the first mode being shorter than the detector exposure time in the second mode.

[0068] According to an embodiment, for the second mode of operation, the control unit controls the movement of the first grid and / or the second grid such that image data is acquired while the first grid and / or the second grid are moving.

[0069] According to an embodiment, the movement of the first grating and / or the second grating during the exposure time comprises a movement effected by at least one vibration transducer 80 controlled by the control unit. The at least one vibration transducer is configured to vibrate the first grating and / or the second grating.

[0070] In an embodiment, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating with vibrations having an amplitude greater than 10 μm.

[0071] Therefore, to perform a calibration measurement with no moiré patterns and all gratings in the beam path, a transducer is used to impose a high frequency, "large" (i.e., several tens of μm) amplitude vibration on one or more of the gratings. This wipes out all moiré fringes from the measurement, even if the exposure time is very short, as the additional vibration frequency and amplitude causes fringe movement to lead to extreme blurring of the patterns.

[0072] Thus, in the second mode, the detector exposure time may be greater than the detector exposure time for the first mode; in the first mode, moving the grating at a particular speed allows detection of Moiré fringes, but now in the second mode, the grating moves further so that attenuation and / or calibration data can be acquired, resulting in the longer exposure time eliminating the fringes. However, by introducing vibration into the grating in the second mode, the grating moves more in the second mode than in the first mode, and the detector can have the same exposure time in both modes, providing simplified detector electronics and processing. However, now in the second mode, in both situations, the fringe pattern that was visible in the first mode is wiped away, leaving a normal attenuation image that can be used for calibration purposes or that can serve as a useful attenuation image in its own right.

[0073] According to an embodiment, for the second mode of operation, the movement of the first grating and / or the second grating during the exposure time comprises a movement effected by at least one lateral movement transducer.

[0074] Thus, for example, a lateral translation transducer that operates to enable acquisition of dark field and phase contrast data in a first mode can be operated in a second mode, such that, for example, movement at a particular speed that was acceptable in the first mode due to a small exposure time now results in the disappearance of interference fringes due to a longer exposure time. Alternatively, the transducer may operate differently in the second mode than in the first mode, imparting faster movement and / or vibration to the grating in the second mode than in the first mode, such that for a given exposure time between modes, interference fringes visible in the first mode are disappeared or wiped away in the second mode.

[0075] According to an embodiment, the exposure time for the first mode of operation is equal to the exposure time in the second mode of operation.

[0076] According to an embodiment, for the second mode of operation, the control unit is configured to control the X-ray detector such that the exposure time is greater than the time period of the resonant frequency of the first grating and / or the second grating.

[0077] Referring to the above-described system for acquiring dark-field and phase-contrast data with associated attenuation data, the system may operate to simply acquire attenuation data and / or calibration data by canceling Moiré fringes. Thus, an embodiment of a system for attenuation image and / or calibration data acquisition comprises 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 disposed between the X-ray source and the X-ray detector. The axis extends through the examination region, and the examination region is configured to allow placement of an object to be inspected. The interferometer arrangement is disposed between the X-ray source and the X-ray detector. The interferometer arrangement comprises 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 moved. During an exposure time of the X-ray detector, the first grating and / or the second grating move a distance greater than or equal to a period of the first grating and / or the second grating. The output unit is configured to output the attenuation image data and / or the calibration data.

[0078] In an embodiment of the system for attenuation image and / or calibration data acquisition, the control unit controls the movement of the first grating and / or the second grating such that image data is acquired while the first grating and / or the second grating are moving.

[0079] In an embodiment 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 includes movement effected by at least one vibration transducer 80 controlled by the control unit, the at least one vibration transducer being configured to vibrate the first grating and / or the second grating.

[0080] In an embodiment 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 with vibrations having an amplitude greater than 10 μm.

[0081] In an embodiment 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 effected by at least one lateral movement transducer 70. The control unit is configured to control the at least one lateral movement transducer to move the first grating or the second grating in a lateral position direction perpendicular to the axis.

[0082] In an embodiment 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 the time period of the resonant frequency of the first grating and / or the second grating.

[0083] FIG. 2 illustrates an embodiment of a method 100 for X-ray dark-field, phase-contrast, and attenuation image acquisition in its basic steps. In an orienting step 110, also referred to as step a), orienting the X-ray source relative to the X-ray detector to define an axis extending from the center of the X-ray source 20 to the center of the X-ray detector 40; In a positioning step 120, also referred to as step b), positioning an inspection region between an X-ray source and an X-ray detector, the first axis extending through the inspection region, the inspection region configured to allow placement of an object to be inspected; In a positioning step 130, also referred to as step c), positioning an interferometer arrangement 30 between an X-ray source and an X-ray detector, the interferometer arrangement comprising a first grating 32 and a second grating 34; In a first mode of operation, In a controlling step 140, also referred to as step d), controlling by the control unit 50 at least one lateral movement transducer 70 to move the first grating or the second grating in a lateral position direction perpendicular to the axis; in a controlling step 150, also referred to as step e), 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 move a distance that is smaller than a period of the first grating and / or the second grating, and the control unit controls the movement of the first grating and / or the second grating such that image data are acquired while the first grating and / or the second grating are moving; In an outputting step 160, also referred to as step g), outputting one or more of the dark-field image data, the phase-contrast image data, and the attenuation image data by the output unit 60. It has.

[0084] In an embodiment, for a first mode of operation, the method comprises controlling, by the control unit, the X-ray detector such that the exposure time is less than the time period of the resonant frequency of vibration of the first grating and / or the second grating.

[0085] In an embodiment, in step e), the movement of the first grating and / or the second grating during the exposure time comprises a movement effected by at least one lateral movement transducer.

[0086] In an embodiment, in step e), the movement of the first grating and / or the second grating during the exposure time comprises movement effected by at least one lateral movement transducer in a lateral position direction as part of the image acquisition protocol.

[0087] Thus, in an embodiment, steps d) and e) may be performed simultaneously.

[0088] According to an embodiment, the method comprises a step f) of controlling 170 by the control unit the X-ray detector in a second mode of operation 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 move a distance greater than or equal to the period of the first grating and / or the second grating. The method also comprises a step h) of outputting 180 by the output unit the attenuation image data and / or the calibration data in the second mode of operation.

[0089] In an embodiment, step f) comprises controlling, by the control unit, the movement of the first grid and / or the second grid so that image data is acquired while the first grid and / or the second grid are moving.

[0090] In an embodiment, 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.

[0091] In an embodiment, step f) comprises vibrating the first grating and / or the second grating by means of at least one vibration transducer with vibrations having an amplitude greater than 10 μm.

[0092] In an embodiment, step f) comprises moving the first grating and / or the second grating during the exposure time by means of at least one lateral movement transducer.

[0093] In an embodiment, the exposure time in step e) is equal to the exposure time in step f).

[0094] In an embodiment, step f) comprises controlling, by the control unit, the X-ray detector such that the exposure time is greater than the time period of the resonant frequency of the first grating and / or the second grating.

[0095] Referring to the above-described methods for acquiring dark field and phase contrast data with associated attenuation data, the method may operate to acquire attenuation data and / or calibration data simply by canceling out Moiré fringes. Thus, an embodiment of a method for attenuation image and / or calibration data acquisition may include: In an orienting step 110, also referred to as step a), orienting the X-ray source relative to the X-ray detector to define an axis extending from the center of the X-ray source 20 to the center of the X-ray detector 40; In a positioning step 120, also referred to as step b), positioning an inspection region between an X-ray source and an X-ray detector, the first axis extending through the inspection region, the inspection region configured to allow placement of an object to be inspected; In a positioning step 130, also referred to as step c), positioning an interferometer arrangement 30 between an X-ray source and an X-ray detector, the interferometer arrangement comprising a first grating 32 and a second grating 34; in a controlling step 170, also referred to as step f), 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 move a distance greater than or equal to a period of the first grating and / or the second grating; In an outputting step 180, also referred to as step h), outputting the attenuation image data and / or the calibration data by an output unit. It has.

[0096] In an embodiment, step f) comprises controlling, by the control unit, the movement of the first grid and / or the second grid so that image data is acquired while the first grid and / or the second grid are moving.

[0097] In an embodiment, 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.

[0098] In an embodiment, step f) comprises vibrating the first grating and / or the second grating by means of at least one vibration transducer with vibrations having an amplitude greater than 10 μm.

[0099] In an embodiment, step f) comprises a step of moving the first grating and / or the second grating during the exposure time by at least one lateral movement transducer, wherein the control unit is configured to control the at least one lateral movement transducer to move the first grating or the second grating in a lateral position direction perpendicular to the axis.

[0100] In an embodiment, step f) comprises controlling, by the control unit, the X-ray detector such that the exposure time is greater than the time period of the resonant frequency of the first grating and / or the second grating.

[0101] As discussed above with respect to FIGS. 1 and 2 , in the new imaging modality, inter-grating motion is required for stepping curves from which X-ray dark-field and phase-contrast information (along with conventional attenuation information) can be determined while one or more of the gratings are moving. Hence, although stepping curves are mentioned herein, the gratings do not need to be stepped and never intentionally stopped. This is achieved by moving the gratings and reducing the blurring effect through reduced exposure times. The exposure time must be short enough so that grating motion during a single exposure is practically negligible or at least does not erase the interference fringes. This can be ensured when the exposure time is significantly shorter than the period of the dominant vibration frequency of the grating. The vibration of the grating may be intrinsic to the system or may be externally induced, for example by a vibration transducer. However, the system may be operable to acquire X-ray attenuation data and / or conventional X-ray attenuation data without moving the interferometer components out of the beam line. This is done when the grating motion or vibration is large enough to eliminate the Moiré fringes. The motion can be as part of the image acquisition performed to acquire data for dark field, phase contrast, and related attenuation data, and / or the motion can be due to vibration. The grating vibration can be intrinsic to the system or can be induced externally, for example, by a vibration transducer. To enable calibration measurements to be performed without Moiré patterns and with all gratings in the beam path, a transducer is used to impose high-frequency, "large" (i.e., several tens of microns) amplitude vibrations on the grating. This wipes out all Moiré fringes from the measurement, even if the exposure time is very short, because the additional vibration frequency and amplitude cause the fringe motion to lead to extreme blurring of the pattern.

[0102] However, there is another novel way in which the Moire fringes can be eliminated, as will now be discussed with reference to FIGS.

[0103] FIG. 3 illustrates an example of a system 1010 for X-ray dark-field, phase-contrast, and attenuation image acquisition. 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 extending from the center of the X-ray source to the center of the X-ray detector is defined. An examination region is disposed 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 allow placement of an object to be inspected. An interferometer arrangement is disposed between the X-ray source and the X-ray detector, and the interferometer arrangement includes a first grating 1032 and a second grating 1034.

[0104] With respect to the first mode of operation: The control unit is configured to control at least one lateral movement transducer 1070 to move the first grating or the second grating in a lateral position direction perpendicular to the axis. The control unit is also 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 move a distance smaller 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 such that image data is acquired while the first grating and / or the second grating are moving. The output unit is configured to output one or more of dark-field image data, phase-contrast image data, and attenuation image data.

[0105] Regarding the second mode of operation: The control unit is configured to control the X-ray detector to acquire each image data of the plurality of image data while the first grating and / or the second grating are moving during an exposure time of the X-ray detector. The control unit is configured to control 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 calibration data including the attenuation image data and / or a determination of 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.

[0106] In an embodiment, the movement of the first grating or the movement of the second grating in a lateral position direction perpendicular to the axis is also perpendicular to the grating lines of the grating.

[0107] In an embodiment, the first grating is positioned between the second grating and the X-ray source.

[0108] In an embodiment, the examination region is located between the first grating and the X-ray detector.

[0109] In an embodiment, the interferometer arrangement comprises three gratings, the source grating being positioned to interact with X-rays emitted from the source, the source grating acting to increase the coherence of X-rays propagating through the interferometer arrangement. Thus, if there is no source grating, there may be two gratings, the first closest to the source being an absorption grating or a phase grating, and the second closest to the detector being an absorption grating. However, if there are 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 grating, which may be an absorption grating or a phase grating, may be the first grating, etc.

[0110] In an embodiment, the first grating is an absorption grating and the second grating is an absorption grating.In an embodiment, the first grating is a phase grating and the second grating is an absorption grating.

[0111] According to an embodiment, for the first mode of operation, the control unit is configured to control the X-ray detector such that the exposure time is smaller than the time period of the resonant frequency of vibration of the first grating and / or the second grating.

[0112] According to an embodiment, for the first mode of operation, the movement of the first grating and / or the second grating during the exposure time comprises a movement effected by at least one lateral movement transducer.

[0113] In an embodiment, the movement of the first grating and / or the second grating during the exposure time comprises movement effected by at least one lateral movement transducer in a lateral position direction as part of the image acquisition protocol.

[0114] According to an embodiment, in a second mode of operation, applying the low pass filter comprises determining an average of at least some of the plurality of image data.

[0115] In an embodiment, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating with vibrations having an amplitude greater than 10 μm.

[0116] Therefore, to perform a calibration measurement without the moiré patterns and with all gratings in the beam path, a transducer is used to impose high-frequency, "large" (i.e., several tens of microns) amplitude vibrations on one or more of the gratings. Averaging the data acquired for each focal spot position tends to wipe out all moiré fringes from the measurement, even if the exposure time is very short, because the additional vibration frequency and amplitude causes fringe movement between images to result in severe blurring of the patterns. Such blurring is further increased through low-pass filtering of the image data.

[0117] In an embodiment, the exposure time for the first mode of operation is equal to the exposure time in the second mode of operation.

[0118] According to an embodiment, the low pass filter comprises a low pass filter kernel having a length greater than the period of oscillation of the first grating and / or the second grating.

[0119] According to an embodiment, for the second mode of operation, the control unit is configured to control the X-ray source to periodically move a focal spot on the target to N different target locations, the control unit is configured to control the X-ray detector to acquire image data separately for each of the N target locations such that at least some of the plurality of image data are associated with one focal spot target location, and the control unit is configured to control the at least one vibration transducer such that the vibration frequency is less than N / (2T), where T is an exposure time of the X-ray detector.

[0120] 4 illustrates a method 1100 for X-ray dark field, phase contrast and attenuation image acquisition in its basic steps. In an orienting step 1110, also referred to as step a), orienting the X-ray source relative to the X-ray detector to define an axis extending from the center of the X-ray source 1020 to the center of the X-ray detector 1040; In a positioning step 1120, also referred to as step b), positioning an inspection region between an X-ray source and an X-ray detector, the first axis extending through the inspection region, the inspection region configured to allow placement of an object to be inspected; In a positioning step 1130, also referred to as step c), positioning an interferometer arrangement 1030 between an X-ray source and an X-ray detector, the interferometer arrangement comprising a first grating 1032 and a second grating 1034; In a first mode of operation, In a controlling step 1140, also referred to as step d), controlling by the control unit 1050 at least one lateral movement transducer 1070 to move the first grating or the second grating in a lateral position direction perpendicular to the axis; in a controlling step 1150, also referred to as step e), controlling 1150 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 move a distance that is smaller than the period of the first grating and / or the second grating, and the control unit controls the movement of the first grating and / or the second grating such that image data are acquired while the first grating and / or the second grating are moving; In an outputting step 1160, also referred to as step f), outputting one or more of the dark-field image data, the phase-contrast image data, and the attenuation image data by an output unit (1060); In a second mode of operation, In a controlling step 1170, also referred to as step g), controlling the X-ray detector by the control unit to acquire each image data of the plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector; In a controlling step 1180, also referred to as step h), controlling by the control unit 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; In a generating step 1190, also referred to as step i), generating, by a processing unit, calibration data comprising determinations of attenuation image data and / or temporally low-pass filtered versions of at least some of the image data; In an outputting step 1200, also referred to as step j), outputting the attenuation image data and / or calibration data by an output unit. It has.

[0121] In an embodiment, for a first mode of operation, the method comprises controlling, by the control unit, the X-ray detector such that the exposure time is less than the time period of the resonant frequency of vibration of the first grating and / or the second grating.

[0122] In an embodiment, in step e), the movement of the first grating and / or the second grating during the exposure time comprises a movement effected by at least one lateral movement transducer.

[0123] In an embodiment, in step e), the movement of the first grating and / or the second grating during the exposure time comprises movement effected by at least one lateral movement transducer in a lateral position direction as part of the image acquisition protocol.

[0124] Thus, in an embodiment, steps d) and e) may be performed simultaneously.

[0125] In an embodiment, step h) comprises vibrating the first grating and / or the second grating by means of at least one vibration transducer with vibrations having an amplitude greater than 10 μm.

[0126] In an embodiment, the exposure time in step e) is equal to the exposure time in step h).

[0127] In an embodiment, step i) comprises determining an average of at least some of the plurality of image data.

[0128] In an embodiment, the low pass filter comprises a low pass filter kernel having a length greater than the period of oscillation of the first grating and / or the second grating.

[0129] In an embodiment, step g) comprises controlling, by a control unit, the X-ray source to periodically move a focal spot on the target to N different target locations, wherein the control unit is configured to control the X-ray detector to acquire image data separately for each of the N target locations such that at least some of the plurality of image data are associated with one focal spot target location, and step h) controls the at least one vibration transducer to have an oscillation frequency smaller than N / (2T), where T is an exposure time of the X-ray detector, and the exposure time is greater than the time period of the resonant frequency of the first grating and / or the second grating.

[0130] FIG. 5 illustrates an example of a system 2000 for attenuation image and / or calibration data acquisition. 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 extending from the center of the X-ray source to the center of the X-ray detector is defined. An examination region is disposed 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 allow placement of an object to be inspected. Thus, the examination region is positioned such that an object can be positioned therein for inspection. An interferometer arrangement is disposed between the X-ray source and the X-ray detector, and the interferometer arrangement includes a first grating 1032 and a second grating 1034. The control unit is configured to control the X-ray detector to acquire each image data of the plurality of image data while the first grating and / or the second grating are moving during an exposure time of the X-ray detector. The control unit is also configured to control 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 calibration data including the attenuation image data and / or a determination of 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.

[0131] In an embodiment, the at least one vibration transducer is configured to vibrate the first grating and / or the second grating with vibrations having an amplitude greater than 10 μm.

[0132] According to an embodiment, applying the low pass filter comprises determining an average of at least some of the plurality of image data.

[0133] According to an embodiment, the low pass filter comprises a low pass filter kernel having a length greater than the period of oscillation of the first grating and / or the second grating.

[0134] According to an embodiment, the control unit is configured to control the X-ray source to periodically move a focal spot on the target to N different target locations, the control unit is configured to control the X-ray detector to acquire image data separately for each of the N target locations, and the control unit is configured to control the at least one vibration transducer such that the vibration frequency is less than N / (2T), where T is the exposure time of the X-ray detector.

[0135] 6 illustrates a method 3000 for attenuation image and / or calibration data acquisition in its basic steps. In a positioning step 3110, also referred to as step a), positioning the X-ray source relative to the X-ray detector to define an axis extending from the center of the X-ray source 1020 to the center of the X-ray detector 1040, an inspection region is positioned between the X-ray source and the X-ray detector, a first axis extends through the inspection region, the inspection region allows for the placement of an object to be inspected, and an interferometer arrangement 1030 is positioned between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating 1032 and a second grating 1034; In a controlling step 3120, also referred to as step b), controlling the X-ray detector by the control unit to acquire each image data of the plurality of image data while the first grating and / or the second grating is moving during an exposure time of the X-ray detector; In a controlling step 3130, also referred to as step c), controlling by the control unit 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; In a generating step 3140, also referred to as step d), generating, by the processing unit 1090, calibration data comprising determinations of attenuation image data and / or temporally low-pass filtered versions of at least some of the plurality of image data; In an outputting step 3150, also referred to as step e), outputting the attenuation image data and / or the calibration data by an output unit. It has.

[0136] In an embodiment, step b) comprises vibrating the first grating and / or the second grating by means of at least one vibration transducer with vibrations having an amplitude greater than 10 μm.

[0137] According to an embodiment, step d) comprises determining an average of at least some of the plurality of image data.

[0138] In an embodiment, the low pass filter comprises a low pass filter kernel having a length greater than the period of oscillation of the first grating and / or the second grating.

[0139] In an embodiment, step b) comprises controlling, by a control unit, the X-ray source to periodically move a focal spot on the target to N different target locations, and the control unit controls the X-ray detector to acquire image data separately for each of the N target locations, and step c) comprises controlling the control unit to control the at least one vibration transducer to have an oscillation frequency less than N / (2T), where T is an exposure time of the X-ray detector.

[0140] Thus, referring to Figures 3-6 for the acquisition of the calibration data and / or the attenuation image itself, the interference fringe pattern is effectively removed through a combination of two techniques. The first is still a vibration applied to at least one of the gratings, with an amplitude at least equal to the grating period. This ensures that the interference fringe pattern oscillates through at least 360°. The second element is the averaging of the detector readings for each focal spot position. Specifically, for a four focal spot acquisition where the focal spot of the X-ray tube moves cyclically between four different locations on the anode, the signal for each focal spot position is low-pass filtered in time. Some specific details include: It may be that the size of the low-pass kernel must be large enough to capture at least one period of the dominant vibration frequency.

[0141] If the integration period of the detector is T, then the Nyquist frequency of the detector is 1 / 2T. However, for a quad focus acquisition, only every fourth reading is used in the averaging. Therefore, to avoid aliasing problems, the oscillation frequency must be sufficiently lower than 2 / T.

[0142] Calibration information can be obtained, for example, by placing different homogeneous materials in the beam during calibration measurements.

[0143] Aspects of the new imaging modality are further described with reference to FIGS.

[0144] FIG. 7 illustrates an example of the interferometer portion of a system capable of acquiring X-ray phase-contrast, dark-field, and attenuation image data. References to the interferometer components above refer only to the gratings in the interferometer portion of the system. The system can image the spatial distribution of attenuation of a sample, as well as the spatial distribution of refraction (phase-contrast imaging) and small-angle scattering (dark-field imaging). The system includes a grating-based interferometer. In this example, the interferometer includes two grating structures G1 and G2; however, 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 radiation propagating through the sample and the G1 and G2 gratings.

[0145] In FIG. 7, the source grating G0 is not shown, and the following discussion considers two grating structures G1 and G2, but all three, G0, G1, and G2, may be present, in which case G0 may be a laterally shifted grating. In FIG. 7, grating G1 is a phase grating (but may also be an absorption grating), and G2 is an absorption grating. The system further includes an X-ray source and an X-ray detector. The X-ray detector, shown here as a CCD detector, may be a 2D full-view X-ray detector, which may be flat or curved. A plurality of detector pixels are arranged in rows and columns as an array forming a 2D X-ray radiation-sensitive surface onto which X-ray radiation emitted by the X-ray source can be aligned. The X-ray detector and the X-ray source are spaced apart to form an examination region. The examination region is appropriately spaced to accommodate the sample to be imaged. The sample may be, for example, a patient's chest or a patient's chest for lung examination. G1 or G2 may be curved or flat, but even if curved, a plane parallel to the center of the grating may be defined. The system may have a transducer that moves the grating laterally and may also have a vibration transducer that vibrates one of the gratings.

[0146] The sample then modulates the radiation attenuation, refraction, and small-angle scattering information, which can then be extracted by the operation of the tandem gratings G1 and G2. The gratings G1 and G2 induce an interference pattern that can be detected as a Moiré pattern of interference fringes on the X-ray detector. If no object were present in the examination region, there would still be an interference pattern that could be observed on the X-ray detector. This is called the reference pattern and is usually captured during a calibration procedure. This occurs, for example, by specifically adjusting or "detuning" the mutual spatial relationship between the two gratings G1 and G2 by inducing a slight deflection so that the two gratings are no longer perfectly parallel. Thus, if a sample is positioned in the examination region and interacts with the radiation as described, the Moiré pattern, now more properly called the sample pattern, can be understood as a perturbed version of the reference pattern.

[0147] To separate this phase information from other contributions to the signal, such as attenuation by the sample, inhomogeneous illumination, or grating imperfections, a modified phase "stepping" technique is used. One of the gratings (G1 or G2, or G0, if present) is phase-stepped in the transverse direction X over at least one period of the grating (as illustrated in FIG. 3). g The source grating G0 is scanned along the lateral direction, or an image is taken at each point of the scan, and this image data is acquired with a detector exposure time such that the Moiré fringes are not washed out while the grating is moving. If a source grating G0 is present, it may be this grating that is scanned along the lateral direction. The resulting phase contrast, dark field, and attenuation data then oscillate sinusoidally with and without the sample, as illustrated for phase contrast (A), dark field (B), and attenuation (C) in Figure 8. Further details of standard phase stepping techniques can be found in Weitkamp et al., Optics Express, Vol. 13, No. 16, (2005) 6296-6304.

[0148] However, in the presently described system, another mode of operation is utilized to acquire X-ray calibration data or normal attenuation data. The grating, which has been moved as described above, can be moved in the same manner by a lateral movement transducer, but the detector exposure time can be increased to eliminate the interference fringes. Also, for a constant detector exposure time, the movement speed can be increased. As will be readily appreciated, there are combinations of movement speed and exposure time that result in the elimination of interference fringes. However, another way to eliminate interference fringes is to simply increase the exposure time to a duration where the interference fringes disappear as a result of the inherent vibrations of the system. These vibrations can be enhanced through the use of a vibration transducer that vibrates the grating laterally so that the Moiré fringes are eliminated for the detector exposure time being used.

[0149] Furthermore, in a different technique, the system can be used to acquire X-ray calibration data or normal attenuation data while the grating remains in place. This technique oscillates the grating, which does not need to move significantly or at all during image acquisition. However, the amplitude of the oscillation is sufficient that, combined with low-pass filtering, several images can be combined. However, now at least one grating has moved from at least one previous image acquisition position, which allows interference fringes that would otherwise be present to be erased or removed. This therefore results in data that can be used for calibration purposes or simply as a normal attenuation image.

[0150] In another exemplary embodiment, a computer program or a computer program element is provided, characterized in that it is adapted to perform, on a suitable system, the steps of the method according to one of the preceding embodiments.

[0151] Thus, the computer program element is stored on a computing unit, which is also part of an embodiment. The computing unit is configured to perform or cause the performance of the steps of the method described above. Furthermore, it is configured to operate the components of the device and / or system described above. The computing unit may be configured to operate automatically and / or to execute user instructions. The computer program is loaded into the working memory of a data processor. The data processor is thus equipped to perform the method according to one of the preceding embodiments.

[0152] This exemplary embodiment of the present invention covers both computer programs that use the present invention from the beginning and computer programs that, through an update, transform an existing program into a program that uses the present invention.

[0153] Furthermore, the computer program element may provide all the necessary steps to accomplish the actions of the exemplary embodiments of the methods described above.

[0154] According to a further exemplary embodiment of the present invention, a computer readable medium such as a CD-ROM, a USB stick or the like is provided, which computer readable medium stores the computer program elements described by the preceding paragraphs.

[0155] The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0156] However, the computer program may also be provided over a network, such as the World Wide Web, and downloaded into the working memory of a data processor from such a network. According to a further exemplary embodiment of the invention, a medium from which a computer program element can be downloaded is provided, the computer program element being configured to perform a method according to one of the above-described embodiments of the invention.

[0157] It should be noted that embodiments of the present invention are described with respect to different subject matters. In particular, some embodiments are described with respect to method-type claims, while other embodiments are described with respect to device-type claims. However, those skilled in the art will understand from the above and below description that, unless otherwise indicated, any combination of features belonging to one type of subject matter, as well as any combination between features related to different subject matters, is considered to be disclosed by the present application. However, all features may be combined to provide synergistic effects that are greater than the sum of the individual features.

[0158] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to 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 disclosure, and the appended claims.

[0159] In the claims, the word "comprises" does not exclude other elements or steps, and the singular does not exclude a plurality. A single processor or other unit may fulfill 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. 1. A system for x-ray dark field, phase contrast and attenuation image acquisition, said system comprising: an X-ray source; an interferometer component; an X-ray detector; a control unit; at least one vibration transducer; a processing unit; Output unit and Equipped with an axis extending from a center of the X-ray source to a center of the X-ray detector is defined; an examination region is disposed between the X-ray source and the X-ray detector, the axis extending through the examination region, the examination region allowing placement of an object to be examined; the interferometer arrangement is disposed between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating and a second grating; the system having a first mode of operation and a second mode of operation; When the system operates in the first mode of operation, the control unit controls at least one lateral movement transducer to move the first grating or the second grating in a lateral position direction perpendicular to the axis; the control unit controls the X-ray detector to acquire image data while the first grating and / or the second grating are moving, and during an exposure time of the X-ray detector, the first grating and / or the second grating move a distance that is smaller than a period of the first grating and / or the second grating, and the control unit controls 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; the output unit outputs one or more of dark-field image data, phase-contrast image data, and attenuation image data; When the system operates in the second mode of operation, the control unit controls the X-ray detector to acquire each image data 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 controls the at least one vibration transducer to vibrate the first grating and / or the second grating, the amplitude of the vibration being greater than or equal to the period of the first grating and / or the second grating so that interference fringes are eliminated and the plurality of image data are acquired; the processing unit generates calibration data including a determination of attenuation image data and / or a temporally low-pass filtered version of at least some of the plurality of image data; The output unit outputs the attenuation image data and / or the calibration data.

2. 2. The system of claim 1, wherein, for the first mode of operation, the control unit controls the X-ray detector such that the exposure time is less than a time period of a resonant frequency of the first grating and / or a resonant frequency of the second grating.

3. 3. The system of claim 1, wherein, for the first mode of operation, movement of the first grating and / or second grating during the exposure time comprises movement effected by the at least one lateral movement transducer.

4. 4. The system of claim 1, wherein in the second mode of operation, applying a low-pass filter to perform the temporal low-pass filtering comprises determining an average of the at least some of the plurality of image data.

5. The system of claim 4 , wherein the low-pass filter comprises a low-pass filter kernel having a length greater than a time period of the oscillation of the first grating and / or the second grating.

6. 6. The system of claim 4 or 5, wherein for the second mode of operation, the control unit controls the X-ray source to cyclically move a focal spot on a target to N different target locations, the control unit controls the X-ray detector to acquire image data separately for each of the N target locations such that at least some of the plurality of image data are associated with one focal spot target location, and the control unit controls the at least one vibration transducer such that an vibration frequency is less than N / (2T), where T is the exposure time of the X-ray detector.

7. 1. A method for X-ray dark field, phase contrast and attenuation image acquisition, said method comprising: a) orienting the X-ray source relative to the 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, the axis extending through the examination region, the examination region being an area allowing placement of an object to be examined; c) disposing an interferometer arrangement between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating and a second grating; and the method comprising a first mode of operation and a second mode of operation; When operating in said first mode of operation: d) controlling, by a control unit, at least one lateral movement transducer to move the first grating or the second grating in a lateral position direction perpendicular to the axis; e) 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 move a distance that is smaller than a period of the first grating and / or the second grating, and the control unit controls the 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 are moving; f) outputting, by an output unit, one or more of the dark-field image data, the phase-contrast image data, and the attenuation image data; and When operating in said second mode of operation: g) controlling the X-ray detector by the control unit to acquire each image data 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) controlling, by the control unit, at least one vibration transducer 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 so that interference fringes are cancelled and the plurality of image data are acquired; i) generating, by a processing unit, calibration data comprising determinations of attenuation image data and / or temporally low-pass filtered versions of at least some of said plurality of image data; j) outputting the attenuation image data and / or the calibration data by the output unit; The method further comprising:

8. 1. A system for attenuation image and / or calibration data acquisition, the system comprising: an X-ray source; an interferometer component; an X-ray detector; a control unit; at least one vibration transducer; a processing unit; Output unit and Equipped with an axis extending from a center of the X-ray source to a center of the X-ray detector is defined; an examination region is disposed between the X-ray source and the X-ray detector, the axis extending through the examination region, the examination region allowing placement of an object to be examined; the interferometer arrangement is disposed between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating and a second grating; the control unit controls the X-ray detector to acquire each image data 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 controls the at least one vibration transducer to vibrate the first grating and / or the second grating, the amplitude of the vibration being greater than or equal to a period of the first grating and / or the second grating so that interference fringes are eliminated and the plurality of image data are acquired; the processing unit generates calibration data including a determination of attenuation image data and / or a temporally low-pass filtered version of at least some of the plurality of image data; The output unit outputs the attenuation image data and / or the calibration data.

9. The system of claim 8 , wherein applying a low pass filter to perform the temporal low pass filtering comprises determining an average of the at least some of the plurality of image data.

10. The system of claim 9 , wherein the low pass filter comprises a low pass filter kernel having a length greater than a time period of the oscillation of the first grating and / or the second grating.

11. 11. The system of claim 8, wherein the control unit controls the X-ray source to periodically move a focal spot on a target to N different target locations, the control unit controls the X-ray detector to acquire image data separately for each of the N target locations, and the control unit controls the at least one vibration transducer to have an vibration frequency less than N / (2T), where T is the exposure time of the X-ray detector.

12. 1. A method for attenuation image and / or calibration data acquisition, the method comprising: a) positioning the X-ray source relative to the 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, the axis extending through the examination region, the examination region being an area allowing placement of an object to be inspected, and an interferometer arrangement is located between the X-ray source and the X-ray detector, the interferometer arrangement comprising a first grating and a second grating; b) controlling the X-ray detector by a control unit to acquire each image data 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 the amplitude of the vibration is greater than or equal to the period of the first grating and / or the second grating so that interference fringes are eliminated and the plurality of image data are acquired; d) generating, by a processing unit, calibration data comprising determinations of attenuation image data and / or temporally low-pass filtered versions of at least some of said plurality of image data; e) outputting the attenuation image data and / or the calibration data by an output unit; A method comprising:

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

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

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

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