WO2016070771A1 - X射线相衬成像系统与成像方法 - Google Patents

X射线相衬成像系统与成像方法 Download PDF

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WO2016070771A1
WO2016070771A1 PCT/CN2015/093605 CN2015093605W WO2016070771A1 WO 2016070771 A1 WO2016070771 A1 WO 2016070771A1 CN 2015093605 W CN2015093605 W CN 2015093605W WO 2016070771 A1 WO2016070771 A1 WO 2016070771A1
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ray
detected object
light intensity
intensity curve
imaging system
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PCT/CN2015/093605
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English (en)
French (fr)
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张丽
陈志强
姜晓磊
朱晓骅
金鑫
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清华大学
同方威视技术股份有限公司
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Priority to EP15839133.4A priority Critical patent/EP3048441B1/en
Priority to US15/328,437 priority patent/US10267752B2/en
Publication of WO2016070771A1 publication Critical patent/WO2016070771A1/zh

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/041Phase-contrast imaging, e.g. using grating interferometers
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00Investigating materials by wave or particle radiation
    • G01N2223/30Accessories, mechanical or electrical features
    • G01N2223/33Accessories, mechanical or electrical features scanning, i.e. relative motion for measurement of successive object-parts
    • G01N2223/3306Accessories, mechanical or electrical features scanning, i.e. relative motion for measurement of successive object-parts object rotates
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00Investigating materials by wave or particle radiation
    • G01N2223/40Imaging
    • G01N2223/401Imaging image processing
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00Investigating materials by wave or particle radiation
    • G01N2223/40Imaging
    • G01N2223/408Imaging display on monitor
    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21KTECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K2207/00Particular details of imaging devices or methods using ionizing electromagnetic radiation such as X-rays or gamma rays
    • G21K2207/005Methods and devices obtaining contrast from non-absorbing interaction of the radiation with matter, e.g. phase contrast

Definitions

  • the present invention relates to X-ray grating imaging techniques, and more particularly to X-ray phase contrast imaging systems and imaging methods.
  • Phase contrast imaging reveals the internal structure of an object by capturing the phase shift information of the X-rays to observe changes in the electron density inside the object.
  • phase contrast imaging methods have emerged to enhance the low contrast resolution of a radiation image by utilizing interference or diffraction phenomena of coherent or partially coherent X-rays.
  • the publication number is "CN101532969A”
  • the name is "X-ray grating phase contrast imaging system and method” (Patent Document 1)
  • Patent Document 1 the publication number is "CN101726503A”
  • the invention name is "X-ray phase contrast tomography”.
  • Patent Document 2 The patent application (Patent Document 2), the entire contents of each of which is hereby incorporated by reference in its entirety, in the the the the the the the the the the the the the the Specifically, two absorption gratings are used to move relatively parallel in a range of one grating period by a plurality of steps, and one image is captured for each translation of one detector; after completing the acquisition process within one grating period, by comparing each pixel point corresponding to The refractive image information of the detected object is calculated by the difference between the sample light intensity curve and the background light intensity curve. This achieves a better phase contrast imaging effect.
  • the method can work under a multi-color, incoherent ray source. It is now a simple and feasible device.
  • Dark field imaging is a technique of imaging a material using indirect light such as scattered light, diffracted light, refracted light, and fluorescence, and imaging the internal structure of the substance by utilizing the difference in X-ray scattering ability of the substance.
  • dark field imaging due to the unique optical properties of hard X-rays, the required optical components are very difficult to fabricate, so hard field imaging of hard X-rays has been difficult to achieve.
  • the hard-field X-ray field imaging technique has unique advantages over brightfield imaging and phase contrast imaging in the ability to resolve and detect fine structures inside the material.
  • X-rays are emitted to the object to be measured; one of the two absorption gratings is stepped in at least one cycle; in each step, the detector receives the X-rays and converts them into electrical signals; after at least one cycle Stepping, the X-ray intensity at each pixel on the detector is expressed as a light intensity curve; according to the light intensity curve at each pixel point on the detector and the light intensity curve in the absence of the detected object Contrast, the second moment of the scattering angle distribution of each pixel is calculated; the image of the object is taken at multiple angles, and then the scattering information image of the object can be obtained according to the CT reconstruction algorithm.
  • the aforementioned raster imaging technique it is necessary to measure the light intensity curve of each detecting unit (pixel point) on the detector by using a stepping technique.
  • the basic principle of the stepping technique utilized is that after the source grating is fixed next to the X-ray source, in the technique based on the Talbot-Lau interferometry, the phase grating or the analytic grating moves relatively parallel in a grating period. In the technique based on the classical optical method, the two absorption gratings move relatively in parallel for several steps in one grating period. One image is captured for each translation of the detector.
  • the refractive image information, the attenuation image information, and the dark field image information can be calculated by comparing the difference between the sample intensity curve and the background light intensity curve corresponding to each pixel point.
  • Conventional stepping techniques are generally flat shift phase gratings or analytical or absorption gratings.
  • the public number was "CN102221565A”, the patent name of which is the "X-ray source grating stepping imaging system and imaging method" (Patent Document 4), the entire contents of which are hereby incorporated by reference in its entirety in the application, A method of stepping the X-ray source grating is proposed.
  • the period of the source grating is on the order of several tens of micrometers, the stepping accuracy requirement is greatly reduced compared to the conventional stepping method.
  • the embodiments of the present application propose a non-coherent method based on distributed X-ray source X.
  • the present invention can greatly reduce the imaging time and reduce the requirements on the mechanical precision of the imaging system and the like.
  • One aspect of the present invention provides an X-ray imaging system for X-ray imaging an object, comprising:
  • a distributed X-ray source a fixed grating module, and an X-ray detector, which are sequentially located in the propagation direction of the X-rays, wherein in the case of performing X-ray imaging, the detected object is located in the distributed X-ray source and the fixed grating Between modules,
  • the fixed grating module is composed of a first grating and a second grating, and the relative positions of the first grating and the second grating are fixed and are sequentially parallel to each other in the direction of X-ray propagation.
  • the light sources of the distributed X-ray source are distributed along a direction perpendicular to the propagation direction of the X-rays and perpendicular to the grating stripes.
  • the X-ray imaging system is further provided with a computer workstation that controls the distributed X-ray source and the X-ray detector to implement the following process:
  • Each light source of the distributed X-ray source is sequentially exposed to emit X-rays to the detected object;
  • the X-ray detector receives X-rays and, through a set of step exposure processes of the distributed X-ray source and corresponding data acquisition, each of the X-ray detectors
  • the intensity of the X-ray at the pixel is expressed as a light intensity curve
  • An image of the detected object is reconstructed based on the obtained pixel values.
  • the invention can fully utilize the superiority of the grating imaging technology, for example, obtaining the three kinds of information indicating the attenuation, the dark field and the phase contrast of the internal information of the substance in one scanning process, and can more comprehensively reflect the internal structural information and composition of the object. information.
  • the invention can utilize the advantages of the distributed X-ray source to quickly switch the exposure, replace the mechanical stepping process with the step exposure process, realize the fast and stable imaging of the grating imaging technology, and thus can be in the fields of medical imaging, security inspection and the like. Play a huge role.
  • an actuating device for rotating the detected object relative to other portions of the X-ray imaging system by a certain angle under the control of the computer workstation .
  • the step exposure process is repeated at each of the rotation angles, and then the image of the detected object is reconstructed according to a predetermined CT image reconstruction algorithm.
  • the distributed X-ray source is a distributed incoherent X-ray source.
  • the distributed incoherent X-ray source uses carbon nanotubes as an electron source.
  • the computer workstation is provided with: a data processing module for performing processing of data information, and calculating pixel values of points on the detected object from the image; image reconstruction module And for reconstructing an image of the detected object according to the calculated pixel value; and a control module for controlling the distributed X-ray source and the X-ray Line detector.
  • the computer workstation is provided with a display unit for displaying an image of the detected object.
  • the computer workstation is capable of calculating an X-ray from a comparison of a light intensity curve of the detected object and a background light intensity curve in which the detected object does not exist.
  • the refractive information of the predetermined point on the detected object is calculated, and the corresponding pixel value is calculated therefrom.
  • the computer workstation is capable of calculating an X-ray from a comparison of a light intensity curve of the detected object and a background light intensity curve in which the detected object does not exist.
  • the scattering information of a predetermined point on the detected object is calculated, and the corresponding pixel value is calculated therefrom.
  • the computer workstation is capable of calculating an X-ray from a comparison of a light intensity curve of the detected object and a background light intensity curve in which the detected object does not exist.
  • the attenuation information of the predetermined point on the detected object is calculated, and the corresponding pixel value is calculated therefrom.
  • an aspect of the present invention provides an X-ray imaging method for X-ray imaging an object using an X-ray imaging system having a distributed X-ray source, a fixed grating module, an X-ray detector, and a computer
  • the workstation, the X-ray imaging method has the following steps:
  • Each of the light sources of the distributed X-ray source is sequentially exposed to emit X-rays to the detected object;
  • the X-ray detector receives X-rays and, through a set of step exposure processes of the distributed X-ray source and corresponding data acquisition, each of the X-ray detectors
  • the intensity of the X-ray at the pixel is expressed as a light intensity curve
  • An image of the detected object is reconstructed based on the obtained pixel values.
  • an aspect of the invention provides an X-ray imaging method comprising:
  • Each light source of the distributed incoherent X-ray source is sequentially exposed to emit X-rays to the detected object;
  • X-rays refracted by the detected object form an X-ray signal of varying intensity via the first absorption grating and the second absorption grating;
  • An image of the detected object is reconstructed based on the obtained pixel values.
  • the object to be detected is rotated, the step exposure process is repeated at each of the rotation angles, and the detected is reconstructed according to a predetermined CT image reconstruction algorithm An image of the object.
  • X-rays are calculated on the object to be detected from a comparison between a light intensity curve of the detected object and a background light intensity curve in which the detected object does not exist.
  • the refractive information of the predetermined point is calculated, and the corresponding pixel value is calculated therefrom.
  • X-rays are calculated on the object to be detected from a comparison between a light intensity curve of the detected object and a background light intensity curve in which the detected object does not exist.
  • the scattering information of the point is predetermined, and the corresponding pixel value is calculated therefrom.
  • X-rays are calculated on the object to be detected from a comparison between a light intensity curve of the detected object and a background light intensity curve in which the detected object does not exist.
  • the attenuation information of the predetermined point is calculated, and the corresponding pixel value is calculated therefrom.
  • a distributed X-ray source is used in place of a conventional X-ray source, and a plurality of distributed light sources are sequentially exposed (step exposure process) to realize a phase stepping process of a conventional mechanical moving grating, which greatly reduces the scanning time.
  • step exposure process the requirement of high-precision translation of the imaging system is reduced, and the high requirements of the whole device for shockproof and ambient temperature are reduced, and the utility of the raster imaging system can be better promoted.
  • FIG. 1 is a schematic diagram of an X-ray phase contrast imaging system based on a distributed incoherent X-ray source, in accordance with one embodiment of the present invention.
  • Fig. 2 is a schematic view showing a light intensity curve obtained by step scanning in the present invention.
  • FIG. 3 is a schematic diagram of a cross-period step scan in the present invention, (a) is a schematic diagram of a multi-cycle acquisition and a cross-period extraction point (the point therein), and (b) is a schematic diagram of a displacement curve acquired across the period.
  • FIG. 4 is a flow chart showing a method of imaging using X-rays according to an embodiment of the present invention.
  • Fig. 5 is a schematic diagram of Application Example 1 according to the present invention.
  • Fig. 6 is a schematic diagram of Application Example 2 according to the present invention.
  • Fig. 7 is a schematic diagram of Application Example 3 according to the present invention.
  • the X-ray phase contrast imaging system of the present invention has a distributed X-ray source S (in the present invention, the distributed X-ray source S is a distributed incoherent X-ray source), a fixed grating module P and X.
  • the ray detector, and the distributed X-ray source S, the fixed grating module P, and the X-ray detector are sequentially located in the direction of propagation of the X-rays. Further, when the object to be detected is imaged, the object to be detected (i.e., the scanned object in Fig.
  • W is placed between the distributed X-ray source S and the fixed grating module P. Further, as shown in FIG. 1, the respective light sources (i.e., X-ray emission points) of the distributed X-ray source S are distributed in a direction perpendicular to the optical path (i.e., the propagation direction of the X-rays) and perpendicular to the direction of the grating stripes. . These X-ray emission points can emit X-rays in a predetermined order, for example, these X-ray emission points sequentially emit X-rays, thereby realizing the effect of the conventional phase stepping.
  • a distributed X-ray source for example, a distributed X-ray apparatus disclosed in the patent application of the publication No. CN103903941A can be used.
  • the distributed X-ray device is capable of controlling X-rays to be emitted at respective focus positions (ie, target points) in a predetermined order.
  • a distributed incoherent X-ray source can employ carbon nanotubes as an electron source.
  • the fixed grating module P is composed of two high-precision gratings G1 and G2 which are parallel to each other.
  • the two high-precision gratings used require relatively stepping motion to implement the stepping technique.
  • the relative positions of the gratings G1 and G2 are fixed, the distance between them is D, and the distance between the distributed X-ray source S and the grating G1 is L.
  • the periods of the two gratings G1, G2 are set to p 1 and p 2 , respectively, which are sequentially placed in parallel in the propagation direction of the X-rays.
  • the period of the gratings G1, G2 is generally between 0.1 and 30 microns.
  • the grating uses heavy metals as the absorbing material, such as gold (Au).
  • Au gold
  • the height of gold as the absorbing material is determined by the energy of the X-rays used, and is usually between 10 and 100 microns. For example, for 20 keV X-rays, gold can block 90% of X-rays when the height is greater than 16 microns.
  • an X-ray detector is used to receive X-rays, and the received X-ray signals can be converted into digitally processable electrical signals by photoelectric signal conversion techniques (eg, digital photography techniques).
  • the X-ray detector may be a matrix detector, wherein each of the detector elements (pixels) can detect a change in intensity of the X-rays incident on the detector element.
  • the X-ray detector is capable of collecting and converting X-rays at regular intervals.
  • a medical low noise area array detector an area array detector with a dynamic range > 12 bits, can be used to cover the entire imaging area.
  • the spatial resolution of the X-ray detector is required to be about 100 microns or less, for example 70 to 100 microns.
  • the X-ray phase contrast imaging system of the present invention further includes a computer workstation.
  • Control, data transfer, image reconstruction, and data processing of the entire imaging system can be performed by a computer workstation.
  • Scanning control information, position information, projection data, and the like are input to a computer workstation through a data acquisition system.
  • the computer workstation completes the extraction of various information of the object, data preprocessing and image reconstruction, and finally displays it on the display.
  • the computer workstation can include a data processing module.
  • the data processing module can be configured to calculate a change in light intensity (curve) after the X-ray passes the detected object, and to calculate the intensity (curve) of the light after the X-ray passes through the detected object, for the digitally-processable electrical signal output from the X-ray detector.
  • the change calculates the absorption information, the scattering information, or the refraction information of the X-ray at a certain point on the detected object, and uses the information to calculate the pixel information of the detected object.
  • the computer workstation may further comprise a control module (not shown in Figure 1) for controlling the operation of the distributed X-ray source S, the detected object W, the fixed grating module P, and the X-ray detector, etc., for example Relative rotation, X-ray emission and information acquisition.
  • a control module for controlling the operation of the distributed X-ray source S, the detected object W, the fixed grating module P, and the X-ray detector, etc., for example Relative rotation, X-ray emission and information acquisition.
  • the control module and the data processing module can be integrated into one, implemented by a single general purpose or special purpose processor.
  • the computer workstation may further include an imaging module (not shown in FIG. 1) that reconstructs an image of the detected object based on the obtained pixel information and outputs the display.
  • the imaging module can be implemented by a processor that is also a data processing module.
  • the X-ray phase contrast imaging system of the present invention may further comprise an actuating device for rotating the object to be detected at an angle relative to other portions of the X-ray contrast imaging system under the control of a computer workstation. Repeating the phase stepwise exposure process of the distributed X-ray source at each rotation angle to obtain X-ray imaging pixel values at multiple angles, and then reconstructing the stereoscopic image of the detected object according to a predetermined CT image reconstruction algorithm .
  • the actuating device has a structure capable of achieving relative rotation of the detected object.
  • the computer workstation can include a display unit for displaying the reconstructed image.
  • the display unit can be implemented by a universal display.
  • the operation of the X-ray phase contrast imaging system based on the distributed incoherent X-ray source is as follows.
  • the distributed X-ray source S and the X-ray detector can be controlled by a computer workstation to implement the following process.
  • the plurality of light sources (ie, X-ray emission points) of the distributed X-ray source S are sequentially exposed (ie, a stepwise exposure process), and at each exposure, the X-ray source S emits X-rays to the detected object W while X
  • the ray detector receives the X-rays; wherein, a set of stepwise exposure processes through the distributed X-ray source (ie, all X-ray emission points sequentially emit X-rays) and corresponding data acquisition, on the X-ray detector
  • the intensity of the X-ray at each pixel is expressed as a light intensity curve (as shown in Figure 2); the intensity curve at each pixel on the X-ray detector is in the absence of the detected object W.
  • the light intensity curve ie, the background light intensity curve
  • the change of the light intensity curve calculates each image The pixel value of the prime point; reconstructs an image of the detected object based on the calculated pixel value. That is, in the present invention, each X-ray emission point of the distributed incoherent X-ray source is sequentially used to emit X-rays instead of the prior art to move the two gratings step by step, and data acquisition, light intensity curve acquisition and The comparison and calculation of pixel values, reconstruction of an image, and the like can utilize the same method as in the prior art.
  • the phase step exposure process of the distributed incoherent X-ray source in the present invention is proposed based on the X-ray source grating stepping method proposed in Patent Document 4.
  • the conventional phase stepping process is to translate one of the gratings in a range of grating periods. If this is done, the respective sources of the distributed X-ray source may overlap, which is difficult to implement in practice.
  • the present invention proposes a cross-period phase stepping method, based on which an X-ray phase contrast imaging system and an imaging method based on a distributed incoherent X-ray source are realized, and a point map and a displacement curve are taken.
  • Figure 3 shows. That is, FIG.
  • FIG. 3 is a schematic diagram of a cross-period step scan in the present invention
  • (a) is a schematic diagram of a multi-cycle acquisition and a cross-period acquisition point (the point therein)
  • (b) is a schematic diagram of the displacement curve acquired across the period.
  • the conventional phase stepping process is performed in one grating period, which corresponds to one sinusoidal period in Fig. 3(a)
  • the cross-periodic phase stepping process proposed in the present invention is more Completed within a raster cycle (ie, taking points across cycles).
  • N points i.e., N steps
  • the cross-period phase stepping process of the present invention it is necessary to take each of the N periods. one point.
  • taking a point in the first cycle corresponds to the first point in the conventional phase stepping process
  • taking a point in the second period corresponding to the second point in the conventional phase stepping process Take a point in the 3rd cycle corresponding to the 3rd point in the traditional phase stepping process, and so on, until one point in the Nth cycle and the Nth in the traditional phase stepping process Point correspondence.
  • the effect of such a point is the same as that of the conventional phase stepping process, and the advantage of such a point is that it provides the possibility and imaging for the placement of the distributed light source.
  • the method provides a basis, if it is a traditional phase stepping process, then the distributed light source can not be placed.
  • a method of taking points across periods is employed in the case where a distributed incoherent light source is used.
  • the method of taking points in a cross-period according to the present invention can also be applied to a prior art X-ray phase contrast imaging system.
  • the requirements of the distributed X-ray source can be determined, and the distributed X-ray source used in the present invention is a distributed incoherent X-ray source.
  • the above description employs a method of taking points across periods in the case of the distributed non-coherent X-ray source of the present invention.
  • the cross-period taking point according to the present invention can also be used in other X-ray phase contrast imaging systems.
  • a method for imaging using X-rays includes: in step 401, an X-ray emission point of a distributed incoherent X-ray source sequentially emits an X-ray beam to an object to be detected; Step 402, each time the distributed incoherent X-ray source emits X-rays, the X-rays refracted by the detected object form an X-ray signal of varying intensity via the first and second absorption gratings (ie, grating G1 and grating G2); Step 403, the X-ray detector receives the X-ray signal of the intensity change, and converts the received X-ray signal into an electrical signal; in step 404, extracts the converted electrical signal by taking a point in a cross-period manner.
  • the X-ray beam passes the refraction angle information of the object, and the pixel information (eg, the pixel value) of the object is derived using a predetermined algorithm. Further, at step 405, an image of the detected object is reconstructed based on the obtained pixel information. Further, as described above, the attenuation information and the scatter information may be obtained from the received X-rays whose intensity changes. That is, in the present invention, the refracting information, the scatter information, and the fading information can be simultaneously obtained, so that the phase contrast pattern, the dark field map, and the attenuation map of the detected object can be simultaneously obtained.
  • the invention can be utilized in an X-ray grating phase contrast CT imaging system.
  • the X-ray grating phase contrast CT imaging system may include a rotating structure for making the detected object relative to the X-ray source and the grating, and the detecting unit, in addition to the system composition as described above. (X-ray detector) or the like is rotated.
  • the CT imaging system can obtain the refraction angle information at each projection angle and the corresponding planar pixel information by rotating the detected object, and then reconstruct a tomographic image of the refractive index distribution inside the object by using a predetermined algorithm.
  • the greatest advantage of the present invention is that it completely eliminates the dependence on the high-precision translation device, and sequentially replaces the stepping technique with a plurality of light sources, thereby greatly reducing the imaging time and reducing the requirements for the mechanical precision of the imaging system and the like.
  • the present invention continues the advantages of Patent Document 1, completely escaping the dependence on the coherence of the ray source, without the limitation of the Talbot distance, and can realize the non-coherence of the near-divided-scale airport using the grating of the period above the micrometer level. Phase contrast imaging under conditions.
  • the system of the present invention is capable of high contrast imaging of weakly absorbing materials (e.g., soft tissues such as breast, blood vessels, and muscles, fibrous materials, insects, etc.) as compared to conventional X-ray imaging.
  • the present invention can reduce the fabrication difficulty of micron-scale periods and large aspect ratio gratings compared to existing phase contrast imaging, and can be easily extended to phase contrast using high energy (>40 keV) X-rays. Imaging.
  • the invention further reduces the threshold of practical application of phase contrast imaging, and opens up new ideas and approaches for the application of phase contrast imaging to medical, biological, industrial materials and the like, and has great practical significance and application value.
  • Fig. 5 is a schematic diagram of Application Example 1 of the present invention.
  • Application Example 1 shows an X-ray phase contrast imaging system based on a distributed X-ray source according to an embodiment of the present invention for X-ray photography.
  • the X-ray phase contrast imaging system can simultaneously obtain three images of attenuation, phase contrast and dark field after one scan, and can be used in applications such as a new generation of mammography machines.
  • FIG. 6 is a schematic diagram of Application Example 2 of the present invention.
  • Application Example 2 shows a distributed X-ray source-based X-ray phase contrast imaging system for X-ray CT imaging according to an embodiment of the present invention, in which a scanning sample W can be rotated in the direction of a vertical optical path.
  • a scanning sample W can be rotated in the direction of a vertical optical path.
  • Fig. 7 is a schematic diagram of Application Example 3 of the present invention.
  • Application Example 3 shows a distributed X-ray source-based X-ray phase contrast imaging system for X-ray CT imaging according to an embodiment of the present invention.
  • the overall mechanical structure of the X-ray phase contrast imaging system can be rotated in the direction of the vertical optical path so that three-dimensional information of the material structure can be obtained.
  • the distributed X-ray source-based X-ray phase contrast imaging system of the present invention uses a distributed incoherent X-ray source instead of a conventional X-ray source, and sequentially uses a plurality of distributed light sources to expose (stepping The exposure process) replaces the phase stepping process of a conventional mechanical moving grating.
  • the present invention innovatively combines distributed X-ray source technology with raster imaging technology.
  • the invention can fully utilize the superiority of the grating imaging technology, for example, obtaining the three kinds of information indicating the attenuation, the dark field and the phase contrast of the internal information of the substance in one scanning process, and can more comprehensively reflect the internal structural information and composition of the object. information.
  • the invention can utilize the advantages of the distributed X-ray source to quickly switch the exposure, replace the mechanical stepping process with the step exposure process, realize the fast and stable imaging of the grating imaging technology, and thus can be in the fields of medical imaging, security inspection and the like. Play a huge role.

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Abstract

一种X射线成像系统与成像方法,所述X射线成像系统具有分布式X射线源(S)、固定光栅模块(P)、X射线探测器及计算机工作站,被检测物体位于所述分布式X射线源(S)与所述固定光栅模块(P)之间,所述计算机工作站进行控制,以实现如下过程:所述分布式X射线源(S)的各光源依次曝光,向所述被检测物体发射X射线;在每次曝光时,所述X射线探测器接收X射线,经所述分布式X射线源(S)的一组步进曝光过程和数据采集,所述X射线探测器上每个像素点处的X射线的光强表示为一个光强曲线;将所述光强曲线与不存在所述被检测物体的情况下的光强曲线进行比较,由光强曲线的变化得到每个像素点的像素值;根据所得到的像素值重建所述被检测物体的图像。

Description

X射线相衬成像系统与成像方法 技术领域
本发明涉及X射线光栅成像技术,特别涉及X射线相衬成像系统与成像方法。
背景技术
在现有技术中,例如CT扫描设备等中,利用X射线对物体进行扫描成像得到了广泛应用。传统的X射线扫描成像一般利用被测材料对X射线的衰减特性来以非破坏性方式检查物体的内部结构。物体内部的各部分组成结构的密度差异越明显,则传统的X射线成像技术的效果越显著。但是,轻元素构成的物质对X射线来说是弱吸收物质,所以,用传统的X射线成像技术几乎看不到它们内部的具体结构。即使用其它辅助的手段,例如,给生物组织打上造影剂,也很难得到清晰的图像,这造成了很多的缺憾。在上世纪九十年代,出现了X射线相衬成像技术。相衬成像是通过捕捉X射线的相移信息来观察物体内部的电子密度变化,从而揭示物体的内部结构。开始时,出现的相衬成像方法一般通过利用相干或者部分相干的X射线的干涉或衍射现象来增强辐射图像的低对比度分辨率。在此基础上,在公开号为“CN101532969A”、名称为“X射线光栅相衬成像系统及方法”(专利文献1)以及公开号为“CN101726503A”、发明名称为“X射线相衬层析成像”(专利文献2)的专利申请中,其中这些专利申请的全部内容在此通过参照引入到本申请中,黄志峰等人提出了非相干光栅相衬成像的新技术构思和方案。具体地,使用两块吸收光栅在一个光栅周期范围内相对地平行移动若干步,每平移一步探测器采集一张图像;在完成一个光栅周期内的采集过程后,通过比较每个像素点对应的样品光强曲线与背景光强曲线的差异而计算出被检测物体的折射图像信息。这取得了较好的相衬成像效果。该方法可以工作在多色、非相干的射线源下,实 现简单可行的装置。
另外,在X射线成像的技术发展过程中,还出现了暗场成像的技术。暗场成像是利用非直射光,例如散射光、衍射光、折射光和荧光等,对物质材料进行成像的技术,并且利用物质对X射线散射能力的差异来对物质内部结构进行成像。对于暗场成像,由于硬X射线独特的光学性质,所需的光学元件制作非常困难,所以,硬X射线的暗场成像一直难以较好地实现。然而,硬X射线的暗场成像技术在对物质内部微细结构分辨和探测能力上相对于明场成像和相衬成像具有独到的优势。由于硬X射线的散射在微米量级或甚至纳米量级尺度,因而硬X射线暗场成像技术能够看到硬X射线明场成像和相衬成像都无法分辨出的物质内部超微细结构。在2009年,在公开号为“CN101943668A”、发明名称为“X射线暗场成像系统和方法”(专利文献3)的专利申请中,其中该专利申请的全部内容在此通过参照引入到本申请,黄志峰等人提出了利用X射线对物体进行暗场成像的技术方案。具体地,向被测物体发射X射线;使得两块吸收光栅之一在至少一个周期内进行步进;在每个步进步骤,探测器接收X射线,并转化为电信号;经过至少一个周期的步进,探测器上每个像素点处的X射线光强表示为一个光强曲线;根据探测器上每个像素点处的光强曲线与不存在被检测物体情况下的光强曲线的对比度,计算得到每个像素的散射角分布的二阶矩;在多个角度拍摄物体的图像,然后根据CT重建算法可以得物体的散射信息图像。
在前述的光栅成像技术中,都需要采用步进技术测量出探测器上每个探测单元(像素点)的光强曲线。所利用的步进技术的基本原理为:源光栅紧邻X光机源固定不动后,在基于Talbot-Lau干涉法的技术中,位相光栅或者解析光栅在一个光栅周期范围内相对平行移动若干步;而在基于经典光学方法的技术中,两块吸收光栅在一个光栅周期范围内相对平行移动若干步。每平移一步探测器采集一张图像。完成一个光栅周期内的采集过程后,通过比较每个像素点对应的样品光强曲线与背景光强曲线的差异可计算出折射图像信息、衰减图像信息和暗场图像信息。传统的步进技术一般是平移位相光栅或者解析光栅或吸收光栅。在2010年,在公开号为 “CN102221565A”、发明名称为“X射线源光栅步进成像系统与成像方法”(专利文献4)的专利申请中,其中该专利申请的全部内容在此通过参照引入到本申请,黄志峰等人提出了X射线源光栅步进的方法。具体地,由于源光栅的周期在几十微米级,相对于传统的步进方法大大降低了步进精度要求。
但即便如此,步进技术的存在仍然对光栅成像技术的推广造成极大障碍,机械系统的步进非常耗时,大大增加扫描时间,同时即使是几十微米级的平移仍然对机械设备的精度、整体设备防震、环境温度等有较高的要求,这两方面大大限制了这种新的光栅成像技术的应用推广。
发明内容
在已经提出的X射线光栅相衬成像、暗场成像以及X射线源光栅步进成像系统等技术的基础上,本申请的实施例提出一种非相干方法实现的基于分布式X射线源的X射线相衬成像系统与成像方法,其中以分布式非相干X射线源代替传统的X射线光源,并且以多个光源依次曝光代替步进技术。从而,本发明能够大大减少了成像时间,降低了对成像系统机械精度等的要求。
本发明的一个方面提供一种用于对物体进行X射线成像的X射线成像系统,包括:
依次位于X射线的传播方向上的分布式X射线源、固定光栅模块以及X射线探测器,其中在进行X射线成像的情况下,被检测物体位于所述分布式X射线源与所述固定光栅模块之间,
所述固定光栅模块由第一光栅和第二光栅构成,所述第一光栅和所述第二光栅的相对位置固定不变并且彼此平行地依次位于X射线的传播方向上,
所述分布式X射线源的各光源沿着垂直于X射线的传播方向且垂直于光栅条纹的方向分布,
所述X射线成像系统还具备计算机工作站,所述计算机工作站对所述分布式X射线源以及所述X射线探测器进行控制,以实现如下过程:
所述分布式X射线源的各光源依次曝光,向所述被检测物体发射X射线;
在每次曝光时,所述X射线探测器对X射线进行接收,并且,经过所述分布式X射线源的一组步进曝光过程和相应的数据采集,所述X射线探测器上每个像素点处的X射线的光强表示为一个光强曲线;
将所述X射线探测器上每个像素点处的光强曲线与不存在所述被检测物体的情况下的光强曲线进行比较,由所述光强曲线的变化得到每个像素点的像素值;
根据所得到的像素值重建所述被检测物体的图像。
本发明可以充分发挥光栅成像技术的优越性,例如在一次扫描过程中同时获得体现物质内部信息的衰减、暗场和相衬这三种信息,并且可以更加全面地反应物体的内部结构信息以及组成信息。同时,本发明可以利用分布式X射线源快速切换曝光的优势,以步进曝光过程替代机械步进过程,实现光栅成像技术的快速稳定成像,从而可以在医疗成像、安全检查等多方面的领域中发挥巨大的作用。
此外,在本发明的X射线成像系统中,还具备:致动装置,用于在所述计算机工作站的控制下,使所述被检测物体相对于所述X射线成像系统的其他部分旋转一定角度。
此外,在本发明的X射线成像系统中,在每个所述旋转角度下,重复所述步进曝光过程,然后根据预定CT图像重建算法来重建所述被检测物体的图像。
此外,在本发明的X射线成像系统中,分布式X射线源是分布式非相干X射线源。
此外,在本发明的X射线成像系统中,分布式非相干X射线源采用碳纳米管作为电子源。
此外,在本发明的X射线成像系统中,所述计算机工作站具备:数据处理模块,用于进行数据信息的处理,并从中计算得出所述被检测物体上各点的像素值;图像重建模块,用于根据计算得出的像素值重建所述被检测物体的图像;和控制模块,用于控制所述分布式X射线源以及所述X射 线探测器。
此外,在本发明的X射线成像系统中,所述计算机工作站具备:显示单元,用于显示所述被检测物体的图像。
此外,在本发明的X射线成像系统中,所述计算机工作站能够从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的折射信息,并由此计算出相应的像素值。
此外,在本发明的X射线成像系统中,所述计算机工作站能够从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的散射信息,并由此计算出相应的像素值。
此外,在本发明的X射线成像系统中,所述计算机工作站能够从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的衰减信息,并由此计算出相应的像素值。
此外,本发明的一个方面提供一种X射线成像方法,利用X射线成像系统对物体进行X射线成像,所述X射线成像系统具有分布式X射线源、固定光栅模块、X射线探测器以及计算机工作站,所述X射线成像方法具有如下步骤:
所述分布式X射线源的各光源依次曝光,向被检测物体发射X射线;
在每次曝光时,所述X射线探测器对X射线进行接收,并且,经过所述分布式X射线源的一组步进曝光过程和相应的数据采集,所述X射线探测器上每个像素点处的X射线的光强表示为一个光强曲线;
将所述X射线探测器上每个像素点处的光强曲线与不存在所述被检测物体的情况下的光强曲线进行比较,由此得到光强曲线的变化;
由所述光强曲线的变化得到所述X射线探测器上每个像素点的像素值;
根据所得到的像素值重建所述被检测物体的图像。
此外,本发明的一个方面提供一种X射线成像方法,包括:
分布式非相干X射线源的各光源依次曝光,向被检测物体发射X射线;
在所述分布式非相干X射线源每次发射X射线时,经所述被检测物体折射的X射线经由第一吸收光栅和第二吸收光栅形成强度变化的X射线信号;
利用X射线探测器接收所述强度变化的X射线信号,并将接收到的X射线信号转换为电信号;
以跨周期取点的方式从所述转换的电信号中提取X射线束经过物体的折射角信息,以及利用预定的算法得出物体的像素值;以及
根据所得到的像素值重建所述被检测物体的图像。
此外,在本发明的X射线成像方法中,使所述被检测物体旋转,在每个所述旋转角度下,重复所述步进曝光过程,并且根据预定CT图像重建算法来重建所述被检测物体的图像。
此外,在本发明的X射线成像方法中,从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的折射信息,并由此计算出相应的像素值。
此外,在本发明的X射线成像方法中,从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的散射信息,并由此计算出相应的像素值。
此外,在本发明的X射线成像方法中,从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的衰减信息,并由此计算出相应的像素值。
根据本发明,用分布式X射线源代替传统的X射线光源,利用分布式的多个光源依次曝光(步进曝光过程)实现传统的机械移动光栅的相位步进过程,大大降低了扫描时间,同时降低了成像系统对于高精度平移的需求,降低了整体设备对于防震、环境温度等的较高要求,可以更好地推动光栅成像系统的实用化。
附图说明
图1是根据本发明一个实施例的基于分布式非相干X射线源的X射线相衬成像系统的示意图。
图2是在本发明中利用步进扫描所获得的光强曲线的示意图。
图3是在本发明中跨周期步进扫描的示意图,(a)是多周期采集与跨周期取点的示意图(其中的点),(b)是跨周期采集位移曲线的示意图。
图4是示出根据本发明实施例的利用X射线进行成像的方法的流程图。
图5是根据本发明的应用示例1的示意图。
图6是根据本发明的应用示例2的示意图。
图7是根据本发明的应用示例3的示意图。
具体实施方式
以下,参照附图详细地对本发明进行说明。
图1是根据本发明的一个实施例的基于分布式非相干X射线源的X射线相衬成像系统的示意图。如图1所示,本发明的X射线相衬成像系统具有分布式X射线源S(在本发明中,分布式X射线源S是分布式非相干X射线源)、固定光栅模块P以及X射线探测器,并且,分布式X射线源S、固定光栅模块P以及X射线探测器依次位于X射线的传播方向上。此外,在对被检测物体进行成像时,使被检测物体(即,图1中扫描物体)W位于分布式X射线源S和固定光栅模块P之间。此外,如图1所示那样,分布式X射线源S的各光源(即,X射线发射点)沿着垂直于光路(即,X射线的传播方向)的方向且垂直于光栅条纹的方向分布。这些X射线发射点可以按照预定顺序发射X射线,例如这些X射线发射点依次发射X射线,由此实现了传统的相位步进的效果。
此外,关于分布式X射线源,例如可以使用公开号为CN103903941A的专利申请中所公开的分布式X射线装置。该分布式X射线装置能够通过控制使得以预定顺序在各焦点位置(即,靶点)发射X射线。此外,根据一个实施例,分布式非相干X射线源可以采用碳纳米管作为电子源。
此外,在本发明中,固定光栅模块P由两块高精度的光栅G1和G2组成,这两个光栅G1和G2彼此平行。在背景技术中所引用的专利文献的光栅成像技术中,所使用的两块高精度光栅需要进行相对步进运动来实现步进技术。而在本发明中,光栅G1和G2的相对位置是固定不变的,它们之间的距离为D,并且,分布式X射线源S与光栅G1之间的距离为L。此外,将两块光栅G1、G2的周期分别设定为p1、p2,它们平行地依次位于X射线的传播方向上。
此外,优选地,光栅G1、G2的周期一般在0.1~30微米之间。光栅使用重金属作为吸收材料,例如金(Au)。例如,作为吸收材料的金的高度由所使用的X射线的能量决定,通常在10~100微米之间。例如,对20keV的X射线来说,金的高度大于16微米时能阻挡90%的X射线。
此外,X射线探测器用于接收X射线,并且能够通过光电信号转换技术(例如,数字化摄影技术)将所接收到的X射线信号转换为可进行数字处理的电信号。优选地,X射线探测器可以是矩阵探测器,其中的每个探测元(像素)可以检测射到该探测元上的X射线的强度变化。优选地,X射线探测器能够定时地进行采集和转换X射线。优选地,可以采用医用低噪声的面阵探测器,动态范围>12bit的面阵探测器,覆盖整个成像区域。为了能够检查到几百微米乳腺钙化组织,X射线探测器的空间分辨率要求在百微米左右或以下,例如70~100微米。
此外,本发明的X射线相衬成像系统还包括计算机工作站。整个成像系统的控制、数据传输、图像重建以及数据处理等均可由计算机工作站完成。扫描控制信息、位置信息、投影数据等通过数据采集系统输入到计算机工作站中。由计算机工作站完成物体多种信息的提取、数据预处理及图像重建的工作,最后在显示器上显示出来。
此外,计算机工作站可包括数据处理模块。数据处理模块可设置成用于从X射线探测器输出的可数字处理的电信号,计算得出X射线经过被检测物体后的光强(曲线)的变化,并且通过所述光强(曲线)变化计算出被检测物体上某个点处对X射线的吸收信息、散射信息或折射信息,以及利用这些信息计算出被检测物体的像素信息。这些功能也可通过编程的软件 来实现,或者可替换地,也可通过专用的硬件芯片组来实现。
此外,计算机工作站还可包括控制模块(在图1中未示出),控制模块用于控制分布式X射线源S、被检测物体W、固定光栅模块P以及X射线探测器等的操作,例如相对转动、X射线发射和信息采集等。优选地,控制模块和数据处理模块可以集成为一体,由单个通用或专用处理器来实现。
此外,计算机工作站还可包括有成像模块(在图1中未示出),成像模块根据得到的像素信息重建被检测物体的图像并输出显示。并且,成像模块可以由兼为数据处理模块的处理器实现。
此外,本发明的X射线相衬成像系统还可包括致动装置,其在计算机工作站的控制下,用于使被检测物体相对于X射线相衬成像系统的其他部分旋转一定角度。在每个旋转角度下,重复分布式X射线源的相位步进曝光过程,从而得出多个角度下的X射线成像像素值,然后,根据预定CT图像重建算法来重建被检测物体的立体图像。该致动装置具有能够实现相对转动被检测物体的结构。
此外,计算机工作站可包括显示单元,用于显示所重建的图像。该显示单元可由通用的显示器来实现。
具体地,根据本发明一个实施例的基于分布式非相干X射线源的X射线相衬成像系统的工作过程如下。例如,在本发明中,可以通过计算机工作站对分布式X射线源S以及X射线探测器进行控制,从而实现下述过程。分布式X射线源S的多个光源(即,X射线发射点)依次曝光(即,步进曝光过程),在每次曝光时,X射线源S向被检测物体W发射X射线,同时X射线探测器对X射线进行接收;其中,经过分布式X射线源的一组步进曝光过程(即,所有X射线发射点依次发射了一次X射线)和相应的数据采集,X射线探测器上每个像素点处的X射线的光强表示为一个光强曲线(如图2所示);将X射线探测器上每个像素点处的光强曲线与不存在被检测物体W的情况下的光强曲线(即,背景光强曲线)相比较(此处,不存在被检测物体W的情况下的光强曲线是已知的,可以存储在计算机工作站或者从外部调入),由所述光强曲线的变化计算得出每个像 素点的像素值;根据所计算得出的像素值重建被检测物体的图像。即,在本发明中利用分布式非相干X射线源的各X射线发射点依次发射X射线来代替现有技术中的使两个光栅进行步进移动,而数据采集、光强曲线的获得和比较以及像素值的计算、图像的重建等可以利用与现有技术相同的方法。
特别地,本发明中的分布式非相干X射线源的相位步进曝光过程是在专利文献4所提出的X射线源光栅步进方法的基础上提出的。但是,传统的相位步进过程是在一个光栅周期范围内平移其中的一块光栅,若按此实现,则分布式X射线源的各个光源会有重叠,实际中难以实现。为了解决此问题,本申请发明提出了跨周期的相位步进方法,以此为基础实现基于分布式非相干X射线源的X射线相衬成像系统与成像方法,其取点示意图与位移曲线如图3所示。即,图3是在本发明中跨周期步进扫描的示意图,(a)是多周期采集与跨周期取点的示意图(其中的点),(b)是跨周期采集位移曲线的示意图。具体地说,传统的相位步进过程是在一个光栅周期内完成的,这对应于图3(a)中的一个正弦周期,而在本发明中所提出的跨周期相位步进过程是在多个光栅周期内完成的(即,跨周期取点)。例如,在传统的相位步进过程中取N个点(即,N步)的情况下,那么相应地,在本发明的跨周期相位步进过程中就需要在N个周期中每个周期取一个点。例如,在第1个周期中取一个点与传统的相位步进过程中的第1个点对应,在第2个周期中取一个点与传统的相位步进过程中的第2个点对应,在第3个周期中取一个点与传统的相位步进过程中的第3个点对应,以此类推,直到在第N个周期中取一个点与传统的相位步进过程中的第N个点对应。考虑到正弦函数的周期性,可知这样取点的效果是与传统的相位步进过程的效果一样的,而这样取点的好处是为分布式光源的摆放提供了可能并为其采用的成像方法提供了依据,如果是传统的相位步进过程,那么分布式光源就没法摆放了。
上文描述,在本发明中,在使用了分布式非相干光源的情况下采用了跨周期取点的方法。但是,并不限于此,根据本发明的跨周期取点的方法也能够应用于现有技术的X射线相衬成像系统。
根据以上的内容,可以确定分布式X射线源的要求,并且,在本发明中所使用的分布式X射线源是分布式非相干X射线源。
(1)对单个光源尺寸的要求。引用专利文献1中对源光栅G0的周期要求,即p0=(P1P2)/(p2-p1)》(l/p1)λ,其中,p0、p1、p2分别为G0、G1和G2这三块光栅的周期,l是G0和G1之间的距离,λ是X射线波长。因此,在本发明中,分布式X射线源的每个光源的焦点尺寸不大于D=p0.DC,其中DC为源光栅的占空比,其定义为开口尺寸与光栅周期之比。
(2)对分布式X射线源的光源间距的要求。由上述的跨周期步进扫描过程可知,一个由n个焦点组成的分布式X射线源,其两两焦点间距为d=(m+1/n).p0,m=1,2,3,...。其中m可以取任意正整数,较大的m取值可以增大光源间距,降低加工难度。
上文描述在本发明的采用分布式非相干X射线源的情况下采用了跨周期取点的方式。但并不限于此,根据本发明的跨周期取点也可以使用在其他的X射线相衬成像系统中。
图4示出根据本发明实施例的利用X射线进行成像的方法的流程图。如图4所示,根据本发明的一个实施例的利用X射线进行成像的方法包括:在步骤401,分布式非相干X射线源的X射线发射点依次向被检测物体发射X射线束;在步骤402,分布式非相干X射线源每次发射X射线时,经被检测物体折射的X射线经由第一和第二吸收光栅(即光栅G1和光栅G2)形成强度变化的X射线信号;在步骤403,X射线探测器接收所述强度变化的X射线信号,并将接收到的X射线信号转换为电信号;在步骤404,以跨周期取点的方式从所述转换的电信号中提取X射线束经过物体的折射角信息,以及利用预定的算法得出物体的像素信息(例如,像素值)。此外,在步骤405,根据所得到的像素信息重建被检测物体的图像。此外,如前述那样,还可以从所接收到的强度变化的X射线得到衰减信息以及散射信息。即,在本发明中,能够同时得到折射信息、散射信息以及衰减信息,从而可同时得到被检测物体的相衬图、暗场图以及衰减图。
本发明能够利用于X射线光栅相衬CT成像系统。根据本发明的一个实施例,该X射线光栅相衬CT成像系统除了包括如上所述的系统组成外,还可以包括一个旋转结构,用于使得被检测物体相对于X射线源和光栅、检测单元(X射线探测器)等进行旋转。所述CT成像系统在CT模式下,可以通过旋转被检测物体,获得各个投影角度下的折射角信息及相应的平面像素信息,进而利用预定算法来重构物体内部的折射率分布的断层图像。
如上所述那样,本发明的最大优点是完全摆脱了对高精度平移装置的依赖,以多个光源依次曝光替代步进技术,从而大大减少成像时间,降低了对于成像系统机械精度等的要求。同时,本发明延续了专利文献1的优点,完全摆脱了对射线源相干性的依赖,没有Talbot距离的限制,而且能使用微米量级以上的周期的光栅实现近分米量级机场的非相干条件下的相衬成像。此外,与传统X射线成像相比,本发明的系统能够对弱吸收物质(例如,乳腺、血管和肌肉等软组织、纤维材料、昆虫等)进行高对比度的成像。此外,与现有相衬成像相比,本发明能够降低了微米量级周期、大深宽比光栅的制作难度要求,并可很容易地推广到使用高能量(>40keV)X射线进行相衬成像。本发明将进一步降低相衬成像实际应用的门槛,为相衬成像走向医学、生物学、工业材料等领域应用开拓崭新的思路和途径,具有重大的实际意义和应用价值。
(应用示例)
以下说明本发明的几个应用例。
图5是本发明的应用示例1的示意图。如图5所示,应用示例1示出将根据本发明的实施例的基于分布式X射线源的X射线相衬成像系统用于X射线摄影。该X射线相衬成像系统可以一次扫描后同时获得衰减、相衬和暗场三种图像,可以用于新一代乳腺机等应用。
此外,图6是本发明的应用示例2的示意图。如图6所示,应用示例2示出将根据本发明的实施例的基于分布式X射线源的X射线相衬成像系统用于X射线CT成像,其中扫描样品W可以沿垂直光路的方向旋转,从而可以获取物质结构的三维信息。
此外,图7是本发明的应用示例3的示意图。如图7所示,应用示例3示出将根据本发明的实施例的基于分布式X射线源的X射线相衬成像系统用于X射线CT成像。该X射线相衬成像系统的整体机械结构可以沿垂直光路的方向旋转,从而可以获取物质结构的三维信息。
综上所述,本发明所提出的基于分布式X射线源的X射线相衬成像系统使用分布式非相干X射线源代替传统的X射线光源,利用分布式的多个光源依次曝光(步进曝光过程)替代传统的机械移动光栅的相位步进过程。这大大降低了扫描时间,同时降低了成像系统对于高精度平移的需求,降低了整体设备对于防震、环境温度等的较高要求,可以更好地推动光栅成像系统的实用化。
本发明创新地将分布式X射线源技术与光栅成像技术相结合。本发明可以充分发挥光栅成像技术的优越性,例如在一次扫描过程中同时获得体现物质内部信息的衰减、暗场和相衬这三种信息,并且可以更加全面地反应物体的内部结构信息以及组成信息。同时,本发明可以利用分布式X射线源快速切换曝光的优势,以步进曝光过程替代机械步进过程,实现光栅成像技术的快速稳定成像,从而可以在医疗成像、安全检查等多方面的领域中发挥巨大的作用。
以上对本发明进行了说明,但是本领域技术人员应该理解的是,对于目前所给出的公开内容,在不脱离这里所描述的本发明技术思想的范围内可以进行各种变形。因此,并不意味着本发明局限于所示出的和所描述的特定实施例。

Claims (15)

  1. 一种X射线相衬成像系统,具备:
    分布式非相干X射线源;
    固定光栅模块,由第一光栅和第二光栅构成,并且所述第一光栅和所述第二光栅相互平行且相对位置固定;以及
    X射线探测器。
  2. 如权利要求1所述的X射线相衬成像系统,其中,
    所述分布式非相干X射线源的各光源沿着垂直于X射线的传播方向且垂直于光栅条纹的方向分布,并且
    所述X射线相衬成像系统还具备计算机工作站,所述计算机工作站对所述分布式非相干X射线源以及所述X射线探测器进行控制,以实现如下过程:
    所述分布式非相干X射线源的各光源依次曝光,向被检测物体发射X射线;
    在每次曝光时,所述X射线探测器对X射线进行接收,并且,经过所述分布式非相干X射线源的一组步进曝光过程和相应的数据采集,所述X射线探测器上每个像素点处的X射线的光强表示为一个光强曲线;
    将所述X射线探测器上每个像素点处的光强曲线与不存在所述被检测物体的情况下的光强曲线进行比较,由光强曲线的变化得到每个像素点的像素值;
    根据所得到的像素值重建所述被检测物体的图像。
  3. 如权利要求2所述的X射线相衬成像系统,还具备:
    致动装置,用于在所述计算机工作站的控制下,使所述被检测物体相对于所述X射线成像系统的其他部分旋转一定角度。
  4. 如权利要求3所述的X射线成像系统,其中,
    在每个所述旋转角度下,重复所述步进曝光过程,然后根据预定CT图像重建算法来重建所述被检测物体的图像。
  5. 如权利要求1所述的X射线相衬成像系统,其中,
    所述分布式非相干X射线源采用碳纳米管作为电子源。
  6. 如权利要求2所述的X射线成像系统,其中,
    所述计算机工作站具备:数据处理模块,用于进行数据信息的处理,并从中计算得出所述被检测物体上各点的像素值;图像重建模块,用于根据计算得出的像素值重建所述被检测物体的图像;和控制模块,用于控制所述分布式X射线源以及所述X射线探测器。
  7. 如权利要求2所述的X射线成像系统,其中,
    所述计算机工作站具备:显示单元,用于显示所述被检测物体的图像。
  8. 如权利要求2所述的X射线成像系统,其中,
    所述计算机工作站能够从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的折射信息,并由此计算出相应的像素值。
  9. 如权利要求2或8所述的X射线成像系统,其中,
    所述计算机工作站能够从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的散射信息,并由此计算出相应的像素值。
  10. 如权利要求2、8和9中任一项所述的X射线成像系统,其中,
    所述计算机工作站能够从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的衰减信息,并由此计算出相应的像素值。
  11. 一种X射线成像方法,具有如下步骤:
    分布式非相干X射线源的各光源依次曝光,向被检测物体发射X射线;
    在所述分布式非相干X射线源每次发射X射线时,经所述被检测物体折射的X射线经由第一吸收光栅和第二吸收光栅形成强度变化的X射线信号;
    利用X射线探测器接收所述强度变化的X射线信号,并将接收到的X射线信号转换为电信号;
    以跨周期取点的方式从所述转换的电信号中提取X射线束经过物体的折射角信息,以及利用预定的算法得出物体的像素值;以及
    根据所得到的像素值重建所述被检测物体的图像。
  12. 如权利要求11所述的X射线成像方法,其中,
    使所述被检测物体旋转,其中,在每个所述旋转角度下,重复所述步进曝光过程,并且根据预定CT图像重建算法来重建所述被检测物体的图像。
  13. 如权利要求11所述的X射线成像方法,其中,
    从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的折射信息,并由此计算出相应的像素值。
  14. 如权利要求11或13所述的X射线成像方法,其中,
    从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的散射信息,并由此计算出相应的像素值。
  15. 如权利要求11、13和14中任一项所述的X射线成像方法,其中,
    从存在所述被检测物体的光强曲线和不存在所述被检测物体的背景光强曲线的对比中计算出X射线在所述被检测物体上预定点的衰减信息,并由此计算出相应的像素值。
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