JP4584550B2 - X-ray measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray measurement technique, and more particularly to an X-ray measurement technique including a CT apparatus and a cone beam CT apparatus.
[0002]
[Prior art]
There is a CT (Computed Tomography) apparatus that uses a one-dimensional X-ray detector and performs rotational imaging while rotating the X-ray source and the one-dimensional X-ray detector around the subject once. Further, there is a cone beam CT apparatus that uses a two-dimensional X-ray detector and performs rotational imaging while rotating the X-ray source and the two-dimensional X-ray detector around the subject one time. In addition, there are a CT apparatus and a cone beam CT apparatus that perform rotation imaging while fixing an X-ray source and an X-ray detector and rotating a subject once. These CT devices and cone beam CT devices are well known.
[0003]
As a two-dimensional X-ray detector used for the cone beam CT, an I.I.-camera type X-ray detection in which an II (Image Intensifier) and a video camera are combined through an optical system. Instruments, planar X-ray detectors, and the like. As a flat type X-ray detector, there is a combination of an amorphous silicon photodiode and a TFT, which are arranged on a square matrix and directly combined with a fluorescent plate. These sensors are well known.
[0004]
In the CT apparatus and cone beam CT apparatus, correction processing is performed on each of a plurality of data obtained by rotational imaging to obtain a set of projection data for three-dimensional reconstruction. A three-dimensional reconstruction is performed on the obtained set of projection data using a three-dimensional reconstruction algorithm to obtain a three-dimensional image. The cone beam CT reconstruction algorithm includes the Feldkamp method. These reconstruction algorithms are well known. A back projection operation is used in the reconstruction process for creating reconstruction data from the projection data, and an orthoprojection operation is used in the reprojection process for creating projection data from the reconstruction data. These operations are well known.
[0005]
When the object includes an object that causes high X-ray absorption, such as metal, an artifact occurs in the three-dimensional image. This is because the data obtained by the X-ray beam passing through the high-absorber is extremely smaller than the data obtained by other beams, so that a sharp edge is formed on the projection data, and this edge makes a three-dimensional reconstruction. Artifacts are generated on the image in the tangential direction of the absorber. For example, a band-shaped artifact is generated in a region connecting metals. In addition, artifacts occur on the tangent line connecting the metal edges.
[0006]
In the medical field, superabsorbents such as metals are frequently used during surgery.
Examples include artificial joints, metal teeth, pins that are inserted for fixation after surgery in the joint, pins that are used to close the thoracotomy after surgery in the chest, and stents that are inserted into blood vessels for vasodilation. In addition, a contrast agent injected into a blood vessel in order to facilitate blood vessel identification is an example of a superabsorbent. When performing X-ray CT measurement on a subject including a high absorber, there is a problem that an image is severely deteriorated due to artifacts generated from the high absorber and a serious trouble is caused in diagnosis. Similarly, in the case of industrial CT, when measuring a subject such as an automobile part or a semiconductor part, there is a problem that an image is severely deteriorated due to an artifact generated from a high-absorbent body, thereby causing a problem in inspection. .
[0007]
As a conventional technique to reduce this artifact, the region of interest including the high-absorber is specified on the reconstructed image, the region corresponding to the region of interest is set as the projection image, and the set region is smoothed before reconstruction. A method for performing processing has been proposed (see, for example, Patent Document 1). In addition, the region of interest including the high-absorber is specified on the reconstructed image, the region corresponding to the region of interest is set as the projection image, and the projection data in the set region is converted to the data obtained by interpolation processing from the nearby projection data. A method of performing reconstruction processing after replacement has been proposed (see, for example, Patent Document 2). Furthermore, a method has been proposed in which a superabsorber is identified on projection data and a reconstruction process is performed after the projection data in the superabsorber region is smoothed (see, for example, Patent Document 3). Furthermore, in a multi-slice X-ray detector in which the X-ray detection channels are two-dimensionally arranged in the channel direction and the segment direction, projection data whose signal intensity is extremely reduced due to a high absorber in the subject. A method has been proposed in which reconstruction processing is performed after replacing the projection data of a detection channel that is not affected by a superabsorber with a different position in the segment direction (see, for example, Patent Document 4).
[0008]
The main cause of artifacts caused by the high absorber is the beam hardening effect. The beam hardening effect means that, in CT measurement using non-monochromatic X-rays, the line integral of the X-ray absorption coefficient on a straight line necessary for reconstruction is the X-ray intensity measured when there is no absorber, and the absorber This is an artifact that occurs due to the fact that it is not accurately expressed in the logarithm of the ratio of the X-ray intensity measured (hereinafter, absorption term).
[0009]
With respect to this point, it has been proposed that the line integral is represented by a polynomial of an absorption term (for example, see Non-Patent Document 1). In such a conventional example, when the subject is composed of a single component, even if the above polynomial correction is completely performed, measurement is performed when a component having a large absorption coefficient is added to the subject as the second component. The line integral has an error, and this error causes beam hardening artifacts, and the line integral of the superabsorber is obtained by performing reprojection after thresholding the reconstructed image. Has been proposed that performs reconstruction processing after correcting reprojection data on the assumption that is proportional to the square term of the line integral of the high absorber.
[0010]
[Patent Document 1]
JP-A-6-98886
[Patent Document 2]
JP-A-8-19533
[Patent Document 3]
JP 2002-153454 A
[Patent Document 4]
Japanese Patent Laid-Open No. 10-337287
[Non-Patent Document 1]
Hsieh et al: “An iterative approach to beam hardening correction in cone beam CT.”, Medical Physics, 27 (1), pp.23-29, 2000
[0011]
[Problems to be solved by the invention]
In the prior art, a data conversion process is performed on an area determined as a high-absorber on the projection data. At that time, in order to prevent discontinuity at the boundary between the conversion area and the non-conversion area, in the above-described conventional example (Patent Document 1), the data in the conversion area is converted into smoothing data using peripheral data. . In the conventional example (Patent Document 2), data in the conversion area is converted into interpolation data from peripheral data. In the conventional example (Patent Document 3), data in the vicinity of the boundary line is smoothed after the data in the conversion area is converted into an arbitrary value. In the conventional example (Patent Document 4), the data in the conversion area is converted to the nearest data. These methods are replacement processing, interpolation processing, and smoothing processing using neighborhood data, and there is a limit to the correction effect. That is, when the superabsorber has very strong X-ray absorption, or when the superabsorber has a wide area, there is a problem that artifact reduction is not sufficiently performed.
[0012]
In general, the CT apparatus and the cone beam CT apparatus have a huge amount of data, so that reconstruction data is stored but projection data is not stored. For this reason, the above-described conventional technique that requires projection data for processing has a problem that correction processing can be performed only during measurement.
[0013]
In general, the reconstructed field of view is the area that the detector can contain at all angles during rotational imaging. In many cases, the two-dimensional detector used in the cone beam CT apparatus cannot fit the subject in the field of view at some angles during rotational imaging.
In that case, in the above-described conventional example (Non-Patent Document 5), since the artifacts generated from the high-absorber existing outside the reconstruction visual field cannot be corrected in the reprojection from the reconstruction image, accurate correction can be performed. It has a problem that it cannot be done.
[0014]
Further, the human body embedded with metal is composed of multiple components of three or more components. In that case, the conventional example (Non-Patent Document 5) has a problem that the high-absorber cannot be completely separated by the threshold means on the reprojection data, and accurate correction cannot be performed. Furthermore, the conventional example (Non-Patent Document 5) has a problem that the amount of calculation becomes enormous if reprojection calculation is performed with high accuracy.
[0015]
Therefore, an object of the present invention is to provide an X-ray measurement technique that realizes good measurement for a subject having a high X-ray absorber.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, an X-ray measurement apparatus according to the present invention includes means for performing a first reconstruction process using projection data, means for extracting a value greater than a threshold value in the reconstruction data, Means for reprojecting reprojection data from the extracted reconstructed data; means for subjecting reprojection data to secondary transformation; means for multiplying secondary transformation reprojection data by a weighting factor; It is characterized by having means for differentially processing projection data and means for performing second reconstruction processing using differential reprojection data.
[0017]
Further, the present invention provides a means for extracting a value larger than the threshold value in the first reconstructed data, a means for reprojecting reprojected data from the extracted reconstructed data, and second transforming the reprojected data Means for processing, means for performing a second reconstruction process using the converted reprojection data, means for multiplying the second reconstruction data by a weighting factor, and weights from the first reconstruction data And means for differentially processing the attached reconstructed data.
[0018]
The present invention further includes means for setting a region including a region where projections are not measured at all angles as a region for acquiring reconstruction data in the first reconstruction process.
[0019]
Further, the present invention relates to a means for calculating a differential coefficient at the end of the data for the projection data and the reprojection data, and a function for storing the differential coefficient at the end of the data and having a zero value at a position away from the end. And a means for converting the data outside the end of the data into a value obtained by a function.
[0020]
The present invention also includes means for smoothing the boundary between the extracted data and the data that has not been extracted when extracting a value larger than the threshold value.
[0021]
The present invention further includes means for setting the number of projections of the reprojection data to twice the number of projections of the projection data in the reprojection processing for obtaining the reprojection data from the reconstruction data.
[0022]
The present invention also includes means for smoothing the reprojection data in the reprojection process.
[0023]
In addition, the present invention includes means for setting an area in the first reconstruction data and restriction means for performing processing subsequent to the first reconstruction processing only on data in the area.
[0024]
The effects according to the present invention are listed below.
[0025]
First, it is possible to reduce artifacts generated from a high-absorber having very strong X-ray absorption and a high-absorber having a wide area. Secondly, when projection data is not stored, it is possible to reduce artifacts generated from the superabsorbent. Thirdly, artifacts generated from the superabsorber existing outside the reconstruction visual field can be reduced. Fourthly, artifacts generated from the high absorber existing outside the reconstruction visual field can be reduced with high accuracy. Fifth, it is possible to reduce artifacts generated from the high-absorber in a subject composed of three or more components. Sixth, artifacts generated from the high absorber can be reduced with high accuracy. Seventh, artifacts generated from the high absorber can be reduced with high accuracy and high speed. Eighth, artifacts generated from the high absorber can be reduced at high speed.
[0026]
A typical configuration example of the present invention will be described below.
[0027]
(1) An X-ray tube that generates X-rays to be irradiated on an inspection object (subject), an X-ray detector that detects measurement data relating to a measurement image of the inspection object, the X-ray tube for the inspection object, and the A process of obtaining a projection data by performing a logarithmic conversion process on the measurement data, the rotation apparatus changing the relative position of the X-ray detector; The first reconstruction processing is performed using the processing to obtain reconstruction data, threshold processing is performed on the reconstruction data, a value larger than the threshold is extracted, and the extracted reconstruction data is A process of performing reprojection processing to obtain reprojection data, a process of performing secondary transformation processing on the reprojection data, obtaining secondary transformation reprojection data, and multiplying the secondary transformation reprojection data by a weighting factor , The projection data The difference processing is performed, the difference data is obtained, the second reconstruction process is performed using the difference data, the correction reconstruction data is obtained, and a three-dimensional reconstruction image is obtained. An X-ray measurement apparatus characterized by that.
[0028]
(2) An X-ray tube that generates X-rays to be irradiated on the inspection object, an X-ray detector that detects measurement data relating to a measurement image of the inspection object, and the X-ray tube and the X-ray detection for the inspection object A rotation device that changes the relative position of the instrument, and a processing device that performs calculation processing of the measurement data, and the processing device performs logarithmic conversion processing on the measurement data to obtain projection data; A process of performing first reconstruction processing using the projection data to obtain first reconstruction data, and a process of performing threshold processing on the first reconstruction data and extracting a value larger than the threshold A process of performing reprojection processing on the extracted reconstructed data to obtain reprojection data, a process of performing secondary transformation processing on the reprojection data, and obtaining secondary transformation reprojection data, and the secondary transformation Using reprojection data, the second A process of performing configuration processing to obtain second reconstructed data, and a process of multiplying the second reconstructed data by a weighting factor, performing differential processing from the first reconstructed data, and obtaining corrected reconstructed data And an X-ray measuring apparatus configured to obtain a three-dimensional reconstructed image.
[0029]
(3) In the X-ray measurement apparatus according to (1) or (2), the processing apparatus includes a process of performing a smoothing process on the reprojection data after the process of obtaining the reprojection data. X-ray measuring apparatus characterized by the above.
[0030]
(4) The X-ray measurement apparatus according to (1) or (2), wherein the X-ray detector is a one-dimensional or two-dimensional detector.
[0031]
(5) In the X-ray measurement apparatus according to (1) or (2), the processing apparatus may perform projection at all angles as a region for acquiring reconstruction data in the first reconstruction process. An X-ray measurement apparatus configured to set a region including a region that has not been measured.
[0032]
(6) In the X-ray measurement apparatus according to (5), the processing device calculates a differential coefficient at an end of the data with respect to the projection data and the reprojection data; Including a process of storing a differential coefficient at an end and calculating a function that becomes a zero value at a position away from the end of the data, and a process of converting data outside the end of the data into a value obtained by the function. The X-ray measurement apparatus according to claim 5.
[0033]
(7) In the X-ray measurement apparatus according to (1) or (2), the processing apparatus extracts extracted data and unextracted data when extracting a value larger than the threshold value. An X-ray measurement apparatus comprising a process for smoothing the boundary of the X-ray.
[0034]
(8) In the X-ray measurement apparatus according to (1) or (2), in the reprojection process for obtaining reprojection data from the reconstructed data, the processing device sets the number of projections of the reprojection data in the reprojection process. An X-ray measurement apparatus configured to be set to twice the number of projections of projection data.
[0035]
(9) The X-ray measurement apparatus according to (1) or (2), wherein the processing device includes a process of smoothing the reprojection data in the reprojection process.
[0036]
(10) In the X-ray measurement apparatus according to (1) or (2), the processing device sets a region in the first reconstruction data, and processing after the first reconstruction processing. An X-ray measurement apparatus comprising: a restriction process that is performed only on data in a region.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0038]
FIG. 2 shows an outline of a cone beam CT apparatus as an example of a three-dimensional X-ray measurement apparatus according to the present invention. The apparatus includes an X-ray tube 201 that generates X-rays, an X-ray detector 202 that detects X-rays transmitted through a subject (inspection target) 203, a holder 204 that holds the subject 203, a subject 203 and the X-ray tube 201. It comprises a rotating device 205 that changes the relative position of the X-ray detector 202, a processing device 206 that processes data detected by the X-ray detector 202, and the like. In FIG. 2, the X-ray detector 202 is a two-dimensional X-ray detector in which detection elements are two-dimensionally arranged. The holder 204 is horizontal to the floor surface, and the X-ray tube 201 and the X-ray detector 202 are rotated around the subject 203 by the rotating device 205. The detector 202 measures the data of the subject 203 from various directions while rotating, and sends the data to the processing device 206.
[0039]
The processing device 206 performs high-absorber artifact correction processing and reconstruction processing on the data to create a three-dimensional image. The processing device 206 includes an input device that can input parameters necessary for the high-absorber artifact correction processing, and a storage device that can hold the parameters. The parameters are a threshold value in threshold processing, the number of pixels of reconstruction data in the first reconstruction processing, the number of projections of reprojection data in reprojection processing, a function in secondary transformation processing, and a weight coefficient in difference processing. is there. In addition, the processing device 206 includes a display device that can display the progress of each process when the superabsorbent artifact correction process is executed.
[0040]
In FIG. 2, the rotation surfaces of the X-ray tube and the X-ray detector are set to be perpendicular to the floor surface, but may be set to be horizontal or oblique to the floor surface. Although the cage is set horizontally on the floor surface, it may be set perpendicularly or obliquely to the floor surface. The subject is fixed and the X-ray tube and the X-ray detector are rotated, but the X-ray tube and the X-ray detector are fixed and the subject is rotated, or the X-ray tube, the X-ray detector and the subject are rotated. You may comprise.
[0041]
FIG. 1 shows an example of a high-absorber artifact correction process according to the present invention. Preprocessing associated with reconstruction processing, such as offset correction, sensitivity correction, distortion correction, and protrusion correction, is performed on all data output from the detector in rotation measurement, either inside the detector or in the processing device, and the measurement data Get 101. In the processing apparatus, the following processing is performed on the measurement data 101.
[0042]
A logarithmic conversion process 102 is performed on the measurement data 101 to obtain projection data 103. A first reconstruction process 104 is performed using the projection data to obtain reconstruction data 105. Next, threshold processing 106 is performed on the reconstruction data 105 to extract a value larger than the threshold. Reprojection processing 107 is performed on the extracted reconstruction data to obtain reprojection data 108. Here, by performing the smoothing process on the reprojection data, it is possible to prevent the occurrence of artifacts due to the discontinuity of the data generated at the time of extraction.
[0043]
Next, secondary conversion processing 109 is performed on the reprojection data 108 to obtain secondary conversion reprojection data 110. For example, the function used for the secondary conversion process is to square the value in each pixel. The secondary transformation reprojection data 110 is image data representing a high-absorber artifact component. The secondary transformation reprojection data 110 is multiplied by a weighting factor, and difference processing 111 is performed from the projection data 103 to obtain difference data 112. A second reconstruction process 113 is performed using the difference data 112 to obtain corrected reconstruction data 114.
[0044]
FIG. 3 shows another example of the high-absorber artifact correction processing according to the present invention. Preprocessing associated with reconstruction processing, such as offset correction, sensitivity correction, distortion correction, and protrusion correction, is performed on all data output from the detector in rotation measurement, either inside the detector or in the processing device, and the measurement data 301 is obtained. In the processing apparatus, the following processing is performed on the measurement data 301.
[0045]
A logarithmic conversion process 302 is performed on the measurement data 301 to obtain projection data 303. A first reconstruction process 304 is performed using the projection data 303 to obtain first reconstruction data 305. Next, threshold processing 306 is performed on the first reconstruction data 305 to extract a value larger than the threshold. A reprojection process 307 is performed on the extracted reconstruction data to obtain reprojection data 308. Here, by performing the smoothing process on the reprojection data, it is possible to prevent the occurrence of artifacts due to the discontinuity of the data generated at the time of extraction.
[0046]
Next, secondary conversion processing 309 is performed on the reprojection data to obtain secondary conversion reprojection data 310. For example, the function used for the secondary conversion process is to square the value in each pixel. A second reconstruction process 311 is performed using the secondary transformation reprojection data 310 to obtain second reconstruction data 312. The second reconstruction data 312 is image data representing a high absorber artifact component. The second reconstruction data is multiplied by a weighting factor, and the difference processing 313 is performed from the first reconstruction data 305 to obtain corrected reconstruction data 314.
[0047]
In the correction processing shown in FIGS. 1 and 3, the projection data and the reprojection data are subjected to calculation processing of a differential coefficient at the end of the data, the differential coefficient is stored at the end of the data, and zero at a position away from the end. A function that becomes a value is calculated, data outside the end of the data is converted into a value obtained by the function, and then a reconstruction process is executed. Thereby, it is possible to prevent the occurrence of artifacts outside the reconstruction visual field.
[0048]
In the correction processing shown in FIGS. 1 and 3, the amount of calculation required for the reprojection processing can be reduced by setting a high threshold value in the threshold processing. In the first reconstruction data, the amount of calculation can be reduced by specifying a region including the superabsorbent and performing the reprojection process and the second reconstruction process only on the region.
[0049]
FIG. 4 shows an example of data in the high-absorber artifact correction processing according to the present invention. The projection data 401 has horizontal a and vertical b pixels. The size of the pixel 402 on the projection data is horizontal P and vertical Q when converted to the rotation center position. The reconstruction data 404 obtained by the first reconstruction processing 403 has horizontal c and vertical d pixels. The size of the pixel 405 on the first reconstruction data is horizontal S and vertical T. In the first reconstruction process, by setting S to be smaller than P, it is possible to prevent a decrease in resolution on a plane parallel to the rotation plane. In the first reconstruction process, by setting T smaller than Q, it is possible to prevent a decrease in resolution on a plane perpendicular to the rotation plane.
[0050]
The number c of pixels in the horizontal direction of the first reconstruction data is a value obtained by dividing the horizontal size of the reconstruction field of view that can be included in the detector at all angles during rotational imaging by the pixel size S. Is also set to a large integer. As a result, it is possible to prevent a reduction in horizontal resolution due to the reconstruction process and a reduction in the field of view. The number d of pixels in the vertical direction of the first reconstruction data is obtained by dividing the vertical size of the reconstruction field of view that can be included in the detector at all angles during rotational shooting by the pixel size T. Is also set to a large integer. As a result, it is possible to prevent a reduction in resolution in the vertical direction due to the reconstruction process and a reduction in the field of view.
[0051]
Instead of the first reconstruction process 405, a large-field reconstruction process 406 is performed in which the reconstruction process is performed on a field 407 wider than the normal reconstruction field 404. As a result, it is possible to image the superabsorbent that exists outside the normal reconstruction field of view, and to reflect the artifacts generated therefrom in the reprojection data. For example, the horizontal pixel count c ′ of the first large-field reconstruction data is set to be twice the horizontal pixel count c of normal reconstruction data.
[0052]
A reprojection process 409 is performed on the first reconstruction data to obtain reprojection data 410.
The number of pixels and the pixel size of the reprojection data 410 are set equal to the number of pixels and the pixel size of the projection data 401. Thereby, it is possible to prevent a reduction in resolution and a reduction in field of view in the reprojection process. By setting the number of projections in the reprojection process equal to the number of projections of the projection data, high-speed computation can be performed. By setting the number of projections in the reprojection process to twice the number of projections of projection data, an increase in artifacts can be prevented.
[0053]
Next, the second reconstruction processing 412 is performed using the secondary transformation reprojection data, and the second reconstruction data 413 is obtained. The number of pixels and the pixel size of the second reconstruction data are set equal to the number of pixels and the pixel size of the first reconstruction data 404. Thereby, it is possible to prevent a reduction in resolution and a reduction in field of view.
[0054]
In the above embodiment, the case where the correction process is performed on the data obtained by the two-dimensional detector has been described. However, the present invention is not limited to this, and the present invention also applies to the one-dimensional data by the one-dimensional detector. It is possible to implement.
[0055]
As described above, according to the present invention, the first reconstruction process is performed using the projection data, a value larger than the threshold value is extracted from the reconstruction data, and the reprojection data is re-created from the extracted reconstruction data. Projection processing, secondary conversion processing of the reprojection data, multiplication of the secondary conversion reprojection data by a weighting factor, differential processing of the weighted reprojection data from the projection data, and second processing using the difference reprojection data By performing the reconstruction process, artifacts generated from a superabsorber having very strong X-ray absorption and a superabsorber having a wide area can be reduced.
[0056]
Further, according to the present invention, a value larger than the threshold value is extracted from the first reconstruction data, the reprojection data is reprojected from the extracted reconstruction data, and the reprojection data is subjected to secondary conversion processing. The second reconstruction process is performed using the converted reprojection data, the second reconstruction data is multiplied by a weighting factor, and the weighted reconstruction data is differentially processed from the first reconstruction data. Thus, artifacts can be reduced when projection data is not stored.
[0057]
Further, according to the present invention, in the first reconstruction process, by setting a region including a region where projections are not measured at all angles as a region from which reconstruction data is acquired, Artifacts generated from the superabsorbent existing in the can be reduced.
[0058]
Further, according to the present invention, for the projection data and the reprojection data, a function that calculates a differential coefficient at the end of the data, stores the differential coefficient at the end of the data, and has a zero value at a position away from the end. By calculating and converting the data outside from the end of the data into a value obtained by a function, artifacts generated from the high absorber existing outside the reconstruction visual field can be reduced with high accuracy.
[0059]
In addition, according to the present invention, when extracting a value larger than the threshold value, the boundary between the extracted data and the data that has not been extracted is smoothed so that it is composed of three or more components. Artifacts can be reduced in a subject.
[0060]
Further, according to the present invention, in the reprojection processing for obtaining reprojection data from reconstructed data, the number of projections of reprojection data is set to twice the number of projections of projection data, thereby reducing artifacts with high accuracy. be able to.
[0061]
In addition, according to the present invention, an area is set in the first reconstruction data, and the processing after the first reconstruction processing is performed only on the data in the area, thereby reducing artifacts at high speed. be able to.
[0062]
【The invention's effect】
The present invention realizes a technique for correcting high-absorber artifacts with high accuracy and high speed, and realizes a three-dimensional X-ray measurement apparatus that enables satisfactory measurement of a subject having a high X-ray absorber. It is.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an example of a high-absorber artifact correction process according to the present invention.
FIG. 2 is a diagram illustrating a configuration example of a three-dimensional X-ray measurement apparatus according to the present invention.
FIG. 3 is a diagram for explaining another example of the high-absorber artifact correction processing according to the present invention.
FIG. 4 is a diagram for explaining an example of data in a high-absorber artifact correction process according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Measurement data, 102 ... Logarithmic conversion process, 103 ... Projection data, 104 ... 1st reconstruction process, 105 ... Reconstruction data, 106 ... Threshold process, 107 ... Reprojection process, 108 ... Reprojection data, 109: Secondary conversion processing, 110: Secondary conversion reprojection data, 111: Difference processing, 112: Difference data, 113: Second reconstruction processing, 114: Correction reconstruction data, 201: X-ray tube, 202 ... X-ray detector 203 ... subject, 204 ... holder, 205 ... rotating device, 206 ... processing device, 301 ... measurement data, 302 ... logarithmic conversion process, 303 ... projection data, 304 ... first reconstruction process, 305 ... first reconstruction data, 306 ... threshold processing, 307 ... reprojection processing, 308 ... reprojection data, 309 ... secondary transformation processing, 310 ... secondary transformation reprojection data, 311 ... second Configuration processing, 312 ... second reconstruction data, 313 ... difference processing, 314 ... corrected reconstruction data, 401 ... projection data, 402 ... pixel, 403 ... first reconstruction processing, 404 ... reconstruction data, 405 ... Pixel, 406 ... Large-field reconstruction processing, 407 ... Field of view, 408 ... Pixel, 409 ... Reprojection processing, 410 ... Reprojection data, 411 ... Pixel, 412 ... Second reconstruction processing, 413 ... Second reconstruction Data, 414 ... pixels.

Claims (10)

An X-ray tube that generates X-rays to be irradiated on the inspection object, an X-ray detector that detects measurement data relating to the measurement image of the inspection object, and a relative relationship between the X-ray tube and the X-ray detector with respect to the inspection object A rotation device that changes a position; and a processing device that performs calculation processing of the measurement data; and the processing device performs logarithmic conversion processing on the measurement data to obtain projection data; and the projection data A first reconstruction process is performed using the first reconstruction data, a process for obtaining first reconstruction data, a threshold process for the first reconstruction data, and a process for extracting a value larger than the threshold, and an extraction above was re-projecting process to the reconstructed data, a process of obtaining a reprojection data, the values at each pixel for the re-projection data subjected to the square to second transformation process, obtain a second transformation reprojection data Processing and secondary transformation Multiplying the reprojection data by a weighting factor, performing a difference process from the projection data to obtain difference data, and performing a second reconstruction process using the difference data to obtain corrected reconstruction data An X-ray measuring apparatus configured to perform a three-dimensional reconstructed image. An X-ray tube that generates X-rays to be irradiated on the inspection object, an X-ray detector that detects measurement data relating to the measurement image of the inspection object, and a relative relationship between the X-ray tube and the X-ray detector with respect to the inspection object A rotation device that changes a position; and a processing device that performs calculation processing of the measurement data; and the processing device performs logarithmic conversion processing on the measurement data to obtain projection data; and the projection data A first reconstruction process is performed using the first reconstruction data, a process for obtaining first reconstruction data, a threshold process for the first reconstruction data, and a process for extracting a value larger than the threshold, and an extraction It was re-projection processing to the reconstructed data, and processing to obtain the re-projection data, wherein the value in each pixel for the re-projection data subjected to the square to second transformation process, obtain a second transformation reprojection data Processing and secondary transformation A second reconstruction process is performed using the projection data, the second reconstruction data is obtained, a weighting factor is multiplied by the second reconstruction data, and a difference process is performed from the first reconstruction data. An X-ray measuring apparatus configured to perform a process for obtaining corrected reconstruction data and obtain a three-dimensional reconstruction image.   The X-ray measurement apparatus according to claim 1, wherein the processing apparatus includes a process of performing a smoothing process on the reprojection data after the process of obtaining the reprojection data.   The X-ray detector according to claim 1, wherein the X-ray detector is a one-dimensional or two-dimensional detector. In the first reconstruction process, the processing device is configured to set a region including a region where projection is measured only at some angles as a region from which reconstruction data is acquired. The X-ray measurement apparatus according to claim 1 or 2. The processing device calculates a differential coefficient at the edge of the image represented by the data for the projection data and the reprojection data, stores the differential coefficient at the edge of the data, and stores the differential coefficient of the image represented by the data . a process of calculating the function to be zero value at a position apart in the outside of the image from the edge, the image enlarged from the edge of the image represented by the original data by increasing the pixel outward from the edge of the image represented by the original data The X-ray measuring apparatus according to claim 5, further comprising a process of converting data in an outer pixel into a value obtained by a function.   The processing apparatus includes a process of smoothing a boundary between extracted data and unextracted data when extracting a value larger than the threshold value. X-ray measuring device. In the reprojection process for obtaining reprojection data from the reconstructed data, the processing device sets the number of images of the reprojection data to twice the number of images of the projection data, and rotates the reprojection data. The X-ray measurement apparatus according to claim 1, wherein the X-ray measurement apparatus is configured to perform difference processing corresponding to projection data at the same angle in imaging . The processing unit, the re-projection processing, X-rays measurement device according reconstructed data to claim 1 or 2, characterized in that it comprises a process of smoothing.   The processing apparatus includes a process for setting an area in the first reconstruction data, and a restriction process for performing a process after the first reconstruction process only on data in the area. The X-ray measurement apparatus according to claim 1 or 2.

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