JP2012083277A - X-ray detector, x-ray ct apparatus using the same, and method for capturing x-ray ct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray detector for improving spatial resolution of an industrial X-ray CT apparatus; and to provide an X-ray CT apparatus using the same, and a method for capturing the X-ray CT.SOLUTION: An X-ray CT apparatus includes: an X-ray source for irradiating an X ray; an X-ray detector for detecting the X ray passing through an imaging-object subject; a driving mechanism for rotating and translating the imaging-object subject placed between the X-ray source and the X-ray detector; a signal processing circuit for quantifying an X-ray transmission amount measured by the X-ray detector; and an arithmetic device for reconstructing the image based on signals. The X-ray detector includes a plurality of semiconductor members 12 for detecting the transmission X ray disposed at known intervals apart so as to be buried in and supported by an FRP reinforced substrate 16 in a linear array state. This constitution can narrow the interval between the semiconductor members 12 so as to have a configuration of a dense array with a little detection blind zone.

Description

  The present invention relates to a technique for improving the X-ray detection density of an X-ray detector, an X-ray CT apparatus using the X-ray detector, and an X-ray CT imaging method.

  X-ray CT equipment is widely used as a medical human body internal measuring device. However, even in industrial applications, the internal state of cast parts can be measured because the internal state can be measured without cutting the object. It is used for many purposes as non-destructive inspection such as measurement.

  In an X-ray CT apparatus, an imaging subject is placed between an X-ray source and a detector, and the amount of X-ray transmitted after the X-ray irradiated from the X-ray source passes through the subject and attenuates is measured by the detector. The image inside the subject is reconstructed from the X-ray transmission amount distribution. For this reason, the detector size strongly affects the spatial resolution of the image.

  Unlike medical applications, industrial X-ray CT apparatuses often have metallic objects as objects, and require X-ray energy having a higher transmission capability than the human body. As an X-ray source for generating X-rays, an X-ray tube can be used up to 800 kV, and an X-ray source by a linear accelerator is required at an energy level in the MV region.

  In an X-ray tube, an X-ray source with a focus size of micron order exists in a low energy level region (˜225 kV), but a thick metal object cannot be imaged because of its low transmission capability. Further, in an X-ray tube having a relatively high energy level (320 kV to 800 kV), the transmission capability increases, but the focal point size of the X-ray generation source increases from submillimeter to millimeter order.

  In a linear accelerator that can obtain an X-ray energy level in the MV region, the transmission capability is further increased, and the focal point size of the X-ray source is from submillimeters as in an X-ray tube in a region with a relatively high energy level (320 kV to 800 kV). Grows on the order of millimeters. These X-ray tubes and linear accelerators are usually collimated and irradiated with X-rays in a fan shape immediately after the generation of X-rays.

  A radiation detector such as a scintillator or a compound semiconductor is used as an X-ray detector that measures the amount of attenuation of X-rays irradiated from the X-ray source and attenuated inside the imaging subject (see Non-Patent Document 1). These X-ray detectors are installed at positions facing the X-ray source with the imaging subject interposed therebetween. The X-ray detector measures the integrated X-ray transmission amount on a straight line discretely arranged at regular intervals and connecting the center of each detector element from the X-ray source.

  In order to capture the entire imaging subject, the subject placed between the X-ray source and the detector is placed on a turntable and rotated to acquire projection data necessary for reconstructing the entire image. Alternatively, the imaging subject is stopped, and the X-ray source and the detector are rotated around the subject to obtain necessary projection data.

Miyai H, Satoh K, Kitaguchi H, Izumi S. A high energy X-ray computed tomography using silicon semiconductor detectors. In: 1996 Nuclear Science Symposium Conference Record, vol. 2, 1997. p. 816-21.

  In the internal measurement in the non-destructive inspection of industrial products using the above-described existing industrial X-ray CT apparatus, it is necessary to detect a defect having a size that affects the structural strength and performance characteristics of the subject. In the case of castings, these fatal casting defects can be detected with existing CT equipment, but to detect smaller defects around these defects, further resolution Improvement is needed.

  In a conventional industrial X-ray CT apparatus, a radiation detector such as a scintillator or a compound semiconductor has been used as an X-ray detector. In particular, as shown in Non-Patent Document 1, a semiconductor compound material is used. Is high in sensitivity to high-energy X-rays, and can be made thinner than a scintillator, and the detector interval in the detector array can be set narrow.

  By narrowing the detector interval, the sampling interval of projection data for image generation is reduced, and a high-resolution image is obtained. On the other hand, in the semiconductor X-ray detector shown in Non-Patent Document 1, in addition to the semiconductor member for detecting the transmitted X-ray, it is for suppressing leakage electrons (crosstalk) between the X-ray detectors. A shielding plate was installed. For this reason, there is a limit to the densification of the detector array by reducing the thickness of the detector. For this reason, there is a limit to improving the resolution as an X-ray CT apparatus.

  Accordingly, a first object of the present invention is to provide an X-ray detector capable of dense arrangement. The second object is to provide an X-ray CT apparatus capable of imaging with high spatial resolution by densifying the arrangement of X-ray detectors. The third object is to provide an X-ray CT imaging method capable of imaging with high spatial resolution by densifying the arrangement of X-ray detectors.

  Means for achieving the first object of the present invention is an X-ray detector comprising a semiconductor member for detecting X-rays and a substrate on which the semiconductor member and electrodes of the semiconductor member are mounted. The X-ray detector is characterized in that the semiconductor member is embedded and a reinforcing substrate for supporting the semiconductor member is provided.

  Similarly, means for achieving the second object include an X-ray source for irradiating X-rays, an X-ray detector for detecting X-rays transmitted through the subject to be imaged, and X detected by the X-ray detector. A signal processing circuit that digitizes the amount of line transmission, an arithmetic device that creates image data based on a signal from the signal processing circuit, and an image that displays an image based on image data obtained through arithmetic processing by the arithmetic device An X-ray CT apparatus having a display device, wherein the X-ray CT apparatus includes the X-ray detector described in the means for achieving the first object as the X-ray detector. .

  Similarly, a means for achieving the third object is to transmit X-rays irradiated from an X-ray source to an object to be imaged, detect the transmitted X-rays with an X-ray detector, and detect the detection result. In the X-ray CT imaging method for digitizing with a signal processing device, creating image data with an arithmetic device based on the signal obtained by the digitization, and visualizing an image based on the image data with an image display device, The X-ray detector described in the means for achieving the first object is used as an X-ray detector, and noise from an adjacent X-ray detector is obtained from projection data acquired by using the X-ray detector. It is an X-ray CT imaging method characterized by having a signal processing process for performing processing for removing the influence for each detector.

  According to the X-ray detector of the present invention, the semiconductor portion of the X-ray detector is embedded in another member, so that the X-ray detector is thinned and can contribute to densification of the arrangement of the X-ray detector.

  According to the X-ray CT apparatus of the present invention, it is possible to provide an apparatus capable of imaging with high spatial resolution by densifying the arrangement of X-ray detectors.

  According to the X-ray CT imaging method of the present invention, it is possible to perform imaging with high spatial resolution by densifying the arrangement of X-ray detectors in a state where noise is suppressed.

It is a figure showing an example of the X-ray CT apparatus which is one Example of this invention. It is a figure showing an example of the X-ray detector structure used for the conventional X-ray CT apparatus. It is the figure which showed an example of the X-ray detector structure used for the X-ray CT apparatus which is one Example of this invention. It is the figure which showed an example of the X-ray detector structure used for the X-ray CT apparatus which is one Example of this invention. It is the figure which showed an example of the processing flow in the case of imaging with the imaging method of this invention using the X-ray CT apparatus which is one Example of this invention. It is the figure which showed an example of the system configuration in the case of imaging with the imaging method of this invention using the X-ray CT apparatus which is one Example of this invention.

  In an embodiment of the present invention, in an industrial X-ray CT apparatus, an X-ray detector is thinned to realize a dense detector array, thereby enabling imaging with high spatial resolution.

  Therefore, the inventor has devised a thin X-ray detector by embedding the semiconductor member 12 of the X-ray detector in a reinforcing substrate 16 made of FRP (fiber reinforced plastics) that supports the semiconductor member 12.

  In an industrial X-ray CT apparatus according to an embodiment of the present invention, an X-ray source 1 that irradiates X-rays, an X-ray detector 2 that detects X-rays transmitted through an object 8 to be imaged, and an X-ray source 1 A mechanism for rotating and translating the subject to be imaged arranged between the X-ray detectors 2 (referring to the turntable 6 in FIG. 1) and the amount of X-ray transmission measured by the X-ray detector is digitized. In the X-ray CT apparatus comprising the signal processing circuit 3 and the image reconstruction device 4 of the arithmetic device for reconstructing data for imaging based on these signals, the X-ray detector 2 is thinned as described above. A plurality of X-ray detectors 2 are arranged at regular intervals in a horizontal plane direction for acquiring a tomographic image, and are arranged in an array. Reference numeral 9 denotes an X-ray source focal point size adjusting mechanism, and reference numeral 10 denotes a signal transmission circuit.

  Further, in the embodiment of the present invention, the X-ray detector 2 has the semiconductor member 12 for detecting transmitted X-rays in a horizontal plane direction for acquiring a tomographic image and a perpendicular (also referred to as a height) perpendicular to that direction. .) FRP reinforcing substrate for arranging a plurality of semiconductor members 12 arranged in a multi-dimensional manner of two or more dimensions in this manner, a plurality of them being arranged at a constant interval in two orthogonal directions to the surface direction. 16 and a shielding plate 17 that suppresses the influence of crosstalk (noise) in any one direction between adjacent X-ray detectors, and projects projection data of a plurality of layers in the height direction of the X-ray detector. Acquired without mechanical scanning.

  Further, the embodiment of the present invention includes a signal processing process for removing the amount of crosstalk for each projection data in order to suppress noise (crosstalk) generated between adjacent detectors.

  Examples of the present invention will be specifically described below. An outline of an industrial X-ray CT apparatus which is an embodiment of the present invention is shown in FIG. In an industrial X-ray CT apparatus, an X-ray source 1 and an X-ray detector 2 are installed to face each other, and a turntable 6 that is a rotational drive mechanism is placed between the two, and an object to be imaged on the turntable 6. 8 is installed. Instead of the turntable 6, a translation drive mechanism may be used.

  The X-rays 7 irradiated from the X-ray source 1 are transmitted through the imaging object 8 and attenuated, and enter the X-ray detector 2 at the opposite position. For the X-ray detector 2, a compound semiconductor detector or a scintillator is used.

  These X-ray detectors 2 use a line array sensor in which the semiconductor members 12 are arranged at regular intervals in the horizontal direction or a planar array sensor in which the semiconductor members 12 are arranged in two dimensions in the horizontal and vertical directions. The X-rays incident on these X-ray detectors 2 are converted into electric signals corresponding to the incident X-ray dose in the X-ray detector 2.

  The obtained electrical signal of each X-ray detector 2 is transmitted from the electrode 15 of the X-ray detector 2 to the detector pixel integration processing mechanism 5, and the electrical signal of each semiconductor member 12 designated by the detector pixel integration processing mechanism 5 is transmitted. The signal of the number of elements is added.

  The processed signal is transmitted to the signal processing circuit 3, amplified and bit-converted, and then transmitted to the image reconstruction device 4. In order to reconstruct an image of the entire imaging subject, the turntable 6 is rotated and X-ray transmission amount data (called projection data) detected by all the X-ray detectors 2 is collected for one rotation at a constant angle pitch. To do.

  Projection data for each fixed angle pitch is sequentially transmitted to and stored in the image reconstruction device 4, and when one rotation is obtained, image reconstruction calculation is executed to generate image data for creating a reconstructed image. Is done. The image data obtained by this generation is visualized by being transmitted to the CT image display device 11 and displayed as an image on the display.

  The X-ray detector 2 used in the X-ray CT apparatus of the present embodiment will be described with reference to FIG. For comparison at that time, the structure of a conventional X-ray detector is shown in FIG. In the conventional X-ray detector, a semiconductor member 12 for detecting X-rays is mounted on an FPC (Flexible printed circuits) substrate 13 and a shielding plate 14 is provided on them. 2A shows one X-ray detector 2, and FIG. 2B shows an X-ray array in which these X-ray detectors are arrayed at regular intervals in the horizontal direction of the imaging tomographic plane. A line detector array is shown.

  In the X-ray detector 2 according to the embodiment of the present invention shown in FIG. 3, the semiconductor member 12 for detecting X-rays is mounted on the recess of the U-shaped FRP reinforcing substrate 16, thereby reinforcing the X-ray detector 2. It is embedded in and supported by the substrate 16. These are provided with an FPC board 13.

  FIG. 3A shows one X-ray detector 2, and FIG. 3B shows a detector array in which these X-ray detectors 2 are arranged at regular intervals in the horizontal direction. As can be seen from FIG. 3B, the structure of the X-ray detector 2 according to the embodiment of the present invention does not have the conventional shielding plate 14, and therefore the thickness of the X-ray detector 2 can be made thinner than before. When the X-ray detectors 2 are arrayed, the interval between the X-ray detectors 2 can be narrowed to make the arrangement of the X-ray detectors 2 dense.

  On the other hand, in the X-ray detector 2 according to the embodiment of the present invention, noise from the adjacent X-ray detectors, so-called crosstalk, is introduced by eliminating the conventional shielding plate 14. Therefore, in the X-ray CT apparatus according to the embodiment of the present invention, in the image reconstruction process, a process of removing noise components due to crosstalk from the projection data obtained by each X-ray detector 2 in each imaging section is performed. An imaging method using the X-ray CT apparatus including these processing processes is shown in FIG.

  In the imaging method according to the embodiment of the present invention, first, after setting the imaging height position 18, the horizontal section imaging 19 at the set height position is performed. In this process, the projection data acquisition 20 of the horizontal section at the set height position is performed. Thereafter, noise correction 21 of the projection data is performed for each X-ray detector. After performing noise correction on all X-ray detectors, image reconstruction 22 is performed using corrected projection data of a horizontal section at a set height position. These processes are repeated at the designated height position, and imaging is completed.

  Next, a second embodiment of the X-ray detector 2 used in the industrial X-ray CT apparatus according to the present invention will be described with reference to FIG. In this embodiment, in one X-ray detector 2, the semiconductor member 12 for detecting X-rays transmitted through the X-ray detector 2 is in a vertical direction perpendicular to the horizontal direction in the first embodiment, that is, A plurality of semiconductor members 12 are arranged at regular intervals in the height direction, and all of the plurality of semiconductor members 12 are embedded in the reinforcing substrate 16 as in the first embodiment, and the whole is held by the reinforcing substrate 16. A shielding plate 17 is provided between the semiconductor members 12 in the height direction in the horizontal direction. In FIG. 4, although it consists of the three semiconductor members 12, it is also possible to pile up the same structure in a height direction. In FIG. 4B, a two-dimensional X-ray detection surface is developed with a structure in which the X-ray detectors 2 are arrayed at regular intervals in the horizontal plane direction in which tomographic images are acquired.

  In the imaging using the X-ray detector 2 according to the second embodiment of the present invention, horizontal sectional images at a plurality of height positions are obtained by a process of rotating the imaging target object 8 once, and projection data of a plurality of tomograms are obtained. The detector can be obtained quickly without mechanical scanning. Therefore, it is possible to greatly shorten the imaging of the whole subject height.

  In addition, in the imaging position designation in the height direction, the conventional X-ray detector always has a constant imaging movement interval in the height direction, but the X-ray detector 2 of the second embodiment of the present invention is used. In imaging, the imaging movement interval in the height direction is changed depending on the number of integrated semiconductor members in the height direction.

  FIG. 6 shows a system configuration for realizing the imaging method of the present embodiment. Conditions necessary for each processing process are input from the input unit C15 by the whole imaging condition specifying unit C9, the noise correction condition specifying unit C10, the detector pixel size specifying unit C11, and the image reconstruction calculation condition specifying unit C12. To enter. The overall imaging conditions are stored in the overall imaging condition storage means C2, and after passing through the noise correction conditions and X-ray source irradiation condition storage means C4 set by the noise correction condition setting means C3, and the projection data storage means C6 by actual imaging, An image is created by the image reconstruction means C7. Finally, a reconstructed image D6 is obtained, recorded in the reconstructed image storage means C8, and displayed on the display means C16.

  As described above, according to each embodiment of the present invention, an apparatus capable of imaging with high spatial resolution by realizing a dense detector array by reducing the thickness of the detector in an industrial X-ray CT apparatus. And an imaging method can be provided.

  Each embodiment of the present invention can provide an apparatus and an imaging method capable of imaging only a specified specific region of an imaging subject to be imaged with high spatial resolution in an industrial X-ray CT apparatus. As an application example of each embodiment, the entire subject to be imaged can be imaged with a rough spatial resolution, and only a necessary area to be examined in detail can be imaged with a high resolution, and a high-resolution image can be imaged in a short time. The obtained imaging data can also be suppressed to the minimum necessary size, and the calculation and analysis time can be shortened.

  As described above, the present invention enables high-precision and high-efficiency nondestructive inspection inside industrial products. The present invention can be applied not only to industrial X-ray CT apparatuses but also to medical X-ray CT apparatuses.

  The present invention is applicable to an X-ray CT apparatus that transmits X-rays to an object to be inspected and inspects the inside of the object nondestructively.

DESCRIPTION OF SYMBOLS 1 X-ray source 2 X-ray detector 3 Signal processing circuit 4 Image reconstruction apparatus 5 Detector pixel integration processing mechanism 6 Turntable 7 X-ray 8 Subject to be imaged 9 X-ray source focus size adjustment mechanism 10 Signal transmission circuit 11 CT Image display device 12 Semiconductor member 13 FPC board 15 Electrode 16 Reinforcement board 17 Shielding plate

Claims (7)

A semiconductor member for detecting X-rays;
In the X-ray detector comprising the semiconductor member and a substrate on which the electrode of the semiconductor member is mounted,
An X-ray detector, wherein the semiconductor member is embedded and a reinforcing substrate for supporting the semiconductor member is provided.   2. The X-ray detector according to claim 1, wherein the plurality of semiconductor members are arranged in a horizontal direction and have a one-dimensional arrangement.   3. The X-ray detector according to claim 2, wherein the plurality of semiconductor members are arranged in a vertical direction and have a multidimensional arrangement.   The X-ray detector according to claim 3, further comprising a shielding plate that shields X-rays between the semiconductor members arranged in the vertical direction. An X-ray source that emits X-rays;
An X-ray detector for detecting X-rays transmitted through the subject to be imaged;
A signal processing circuit for quantifying the amount of X-ray transmission detected by the X-ray detector;
An arithmetic unit for creating image data based on a signal from the signal processing circuit;
In an X-ray CT apparatus provided with an image display device for displaying an image based on image data obtained through arithmetic processing by the arithmetic device,
An X-ray CT apparatus comprising the X-ray detector according to any one of claims 1 to 4 as the X-ray detector.   6. The signal processing unit according to claim 5, further comprising: a signal processing unit that performs, for each detector, processing for removing the influence of noise from an adjacent X-ray detector from projection data acquired using the X-ray detector. X-ray CT system. X-rays radiated from an X-ray source are transmitted through an object to be imaged, the transmitted X-rays are detected by an X-ray detector, and the detection results are digitized by a signal processing device and obtained by quantification. In an X-ray CT imaging method of creating image data with an arithmetic device based on the received signal and visualizing an image based on the image data with an image display device,
While using the X-ray detector as described in any one of Claims 1-4 as said X-ray detector, from the projection data acquired using the said X-ray detector from the adjacent X-ray detector. An X-ray CT imaging method comprising a signal processing process for performing processing for removing the influence of noise for each detector.

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