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WO2016038667A1 - Procédé et dispositif d'imagerie à rayons x - Google Patents

Procédé et dispositif d'imagerie à rayons x Download PDF

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Publication number
WO2016038667A1
WO2016038667A1 PCT/JP2014/073737 JP2014073737W WO2016038667A1 WO 2016038667 A1 WO2016038667 A1 WO 2016038667A1 JP 2014073737 W JP2014073737 W JP 2014073737W WO 2016038667 A1 WO2016038667 A1 WO 2016038667A1
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absorption coefficient
rays
subject
ray
ray imaging
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PCT/JP2014/073737
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English (en)
Japanese (ja)
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明男 米山
馬場　理香
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株式会社日立製作所
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]

Definitions

  • the present invention relates to a method and apparatus for imaging an object using X-rays.
  • the X-ray imaging method is a method for observing the structure inside the subject in a non-destructive manner by utilizing the high X-ray transmittance, and is widely used in various fields ranging from product inspections to airport security checks. Further, there is X-ray CT (Computed Tomography) that uses transmission images from a plurality of different angles acquired by rotating a subject relative to an X-ray source to calculate a cross-sectional image of the subject. X-ray CT is an indispensable technique for medical diagnosis because it allows non-destructive observation of the internal structure of a subject in three dimensions.
  • the X-ray imaging method detects the change in signal intensity that occurs when X-rays pass through the subject using the principle that the density of the X-ray absorption increases as the density of the image increases. Is forming. That is, in the X-ray imaging method, since the spatial density distribution in the subject can be measured, an area having a large density change (such as a boundary area (shape) or an internal structure having a different composition) can be visualized with high definition.
  • the conventional X-ray imaging method detects only the spatial density distribution in the subject, and information such as what elements the subject is composed of (ie, information on constituent elements (composition)). ) Is not expected to obtain. For this reason, in order to identify the elements contained in the subject, it is necessary to combine with other methods using fluorescent X-rays or absorption edges, but the fluorescence detector has no spatial resolution (only intensity detection) ), It is necessary to limit the region where fluorescent X-rays are generated by narrowing down X-rays, and a large sample cannot be measured at one time. In addition, in the method using the absorption edge, the number of elements that can be detected is limited to one, and it is not possible to detect all the elements contained in a composite material or compound composed of a plurality of elements.
  • the present application adopts, for example, the technical configuration described in the claims.
  • the present specification includes a plurality of means for solving the above-described problems, as an example thereof, a technique is adopted in which a processing procedure shown below is executed by an arithmetic device such as a computer.
  • each of three or more types of X-rays having different average energies is irradiated from a plurality of angles to the same region of the subject.
  • Intensity I (En, X, Y) of each pixel of the cross-sectional image calculated from the transmission image acquired for the X-ray having the same average energy transmitted through the same region (corresponding to the processing (2) described above)
  • This is a technique for causing a computer to execute the above-described processes (1), (3), (5) and (6).
  • “measured absorption coefficient ⁇ ′” is used instead of “relative measured absorption coefficient ⁇ ′”.
  • the flowchart explaining an example of the X-ray imaging procedure to propose The figure which shows the example which calculated the element contained in a to-be-photographed object (metal foil) using the proposal method. The figure explaining the change (difference) which arises in the linear absorption coefficient of each element when the energy of X-ray is changed from 10 keV to 20 keV. The figure explaining the relationship between the absorption edge (K edge) and energy of each element.
  • 1 is a diagram illustrating a schematic configuration of an X-ray imaging apparatus according to Embodiment 1.
  • FIG. 3 is a flowchart for explaining measurement processing in the first embodiment.
  • FIG. 9 is a flowchart for explaining an initial value setting method according to the second embodiment.
  • FIG. 10 is a diagram illustrating an example of measurement of the transmittance of a subject by the method of the third embodiment. 10 is a flowchart for explaining an initial value setting method according to the third embodiment.
  • FIG. 6 is a diagram illustrating a schematic configuration of an X-ray imaging apparatus according to Embodiment 4. 10 is a flowchart for explaining measurement processing in the fourth embodiment.
  • Equation (2) if the X-ray energy is known, the linear absorption coefficient ⁇ i of each element is also known. However, in addition to the thickness t, since the formula is one for a plurality of unknowns (i.e. content sigma i), (2) can not be uniquely determined the content of sigma i of each element from the equation. When the subject includes n elements, theoretically, n + 1 different formulas (2) including the thickness t are required to uniquely determine the content ⁇ i of each element. Therefore, the X-ray energy is changed, the same measurement is performed for a plurality of X-rays having different energies, and n + 1 equations (2), that is, I (E) / I o (E) are obtained from each transmission image. get.
  • obtaining the three content rates ⁇ 1 , ⁇ 2 , and ⁇ 3 corresponds to solving simultaneous linear equations represented by the following matrix.
  • the content of each element can be uniquely determined by Gaussian elimination or the like. As described above, if the elements contained in the subject are limited and the data of the absorption coefficient acquired by X-rays of different energy is larger than the number of elements contained in the subject, it is included in the subject. It is possible to quantitatively detect the amount of the element.
  • FIG. 1 shows an outline of an X-ray imaging procedure executed in the X-ray imaging apparatus.
  • Step S1 The X-ray imaging apparatus acquires the average intensity I 0 (En, X, Y) in the background area of the subject for each X-ray having different average energies.
  • Step S2 The X-ray imaging apparatus irradiates the same region of the subject with the X-rays having different average energies, and obtains the intensity I (En, X, Y) of each pixel in the transmission image for each X-ray having different average energies.
  • Steps S1 and S2 may be executed in time sequence every time X-rays having different average energies are set, or after step S1 is executed for all X-rays having different average energies, the average energies differ.
  • Step S2 may be executed for all X-rays.
  • Step S3 The X-ray imaging apparatus divides each intensity I (En, X, Y) acquired in step S2 by the average intensity I 0 (En, X, Y) acquired using X-rays having the same average energy. Further, by calculating-(minus) (-ln (x)) of the natural logarithm, the measured absorption coefficient ⁇ of the subject with respect to the X-ray having each average energy is obtained.
  • This process may be executed after all the processes of steps S1 and S2 are completed, or in parallel with the processes of steps S1 and S2, the average intensity of step S1 and the process of step S2 for one average energy. The processing may be started when both of the intensities are acquired.
  • Step S4 The X-ray imaging apparatus sets the average energy of one of the three or more types of X-rays as the reference energy E 0 , and has the other average energy according to the measured absorption coefficient ⁇ determined for the reference energy E 0.
  • the relative measured absorption coefficient ⁇ ′ is calculated by dividing the individually determined measured absorption coefficient ⁇ for the line. This process is executed for the purpose of removing the unknown variable a (the reciprocal of the object thickness t) from the relational expression described above. By executing step S4, the only unknown variable remaining in the relational expression is the element content ⁇ i expected to be included in the subject.
  • the X-ray imaging apparatus calculates, for each average energy, a theoretical synthetic absorption coefficient ⁇ Ic that is theoretically synthesized from each theoretical absorption coefficient ⁇ Ii and each content rate ⁇ i of an element expected to be included in the subject. .
  • the X-ray imaging apparatus compares the theoretical synthetic absorption coefficient ⁇ Ic calculated for each average energy and the relative measured absorption coefficient ⁇ ′, and each of the objects included in the subject so that the sum of squares of the difference is minimized.
  • the element content ⁇ i is obtained by repeated calculation.
  • step S6 can be reduced to a non-linear optimization problem.
  • Specific calculation methods include various methods such as a direct search method, a gradient method, and a Gauss-Newton method that have been developed as an optimization method. Can be used.
  • the point p (that is, the content ratio ⁇ i of each element) at which the error E is minimized can be obtained.
  • Figure 2 shows the measurement of X-rays with energy of 8, 10, 15, 20, 30, 40, and 50 keV for metal foils composed of aluminum, iron, copper, molybdenum, and tin. It is the result of calculating (simulating) the content ⁇ i of each metal by calculating the absorption coefficient (transmittance) ⁇ and repeating the calculation based on the optimization method.
  • calculation is performed including titanium, cobalt, and nickel having relatively close atomic numbers in addition to the above metals.
  • the above simplex method is used, and the content ratio ⁇ i of each element is set to the same ratio as an initial value. From this result, it can be seen that the assumed content rate ⁇ i is almost calculated.
  • the converged solution may be a minimum value and may not be the correct minimum value.
  • FIG. 3 is a result of calculating a change (difference) that occurs when the X-ray energy is changed from 10 keV to 20 keV with respect to the linear absorption coefficient ⁇ i of each element.
  • FIG. 3 shows that the amount of change in the linear absorption coefficient ⁇ i has a unique value for each element. That is, the contained element can be estimated to some extent from the change to energy.
  • the inventor obtains a change from data acquired (measured) with each energy of X-ray, compares the obtained change with a change obtained by theoretical calculation, and further tends to be similar. Based on the assumption that the subject contains the largest number of elements indicating the above, a method is proposed that employs an initial value with a higher content of elements that show similar tendencies and elements in the vicinity thereof. In the calculation process employing this method, compared to a method not employing this method, the initial value generally approaches a correct solution, and the content rate ⁇ i can be obtained more accurately.
  • each element has an energy called an absorption edge, and the linear absorption coefficient ⁇ i changes abruptly.
  • the energy interval to be measured is narrow, projection images are obtained before and after such an absorption edge, so that the linear absorption coefficient ⁇ i changes abruptly for a specific element. Therefore, the projection images acquired for each energy are arranged in order of energy, and it is determined whether or not the transmittance with respect to the energy changes abruptly in each pixel, and the element contained in the subject based on the energy in which the abrupt change is recognized
  • the projection image (two-dimensional image) is described.
  • the subject is rotated relative to the X-ray source, and the cross-sectional image is obtained nondestructively from the acquired projection images at the respective rotation angles.
  • X-ray CT it is possible to three-dimensionally acquire information on the elements of a subject by performing similar processing on images (cross-sectional images) obtained with different X-ray energies.
  • the theoretical synthetic absorption coefficient ⁇ Ic that minimizes the residual from the relative measured absorption coefficient ⁇ ′ acquired by irradiating the same region of the subject with three or more types of X-rays having different average energies.
  • Example Below, the Example of the X-ray imaging method and apparatus based on the above-mentioned view is described in order.
  • FIG. 5 illustrates a schematic configuration of the X-ray imaging apparatus according to the first embodiment.
  • the X-ray imaging apparatus shown in FIG. 5 includes an X-ray source 1, a subject 2, a subject holder 3, a subject positioning mechanism 4, an X-ray image detector 5, a control unit 6, an estimated content rate calculation unit 7, and a display device 8. is doing.
  • the X-ray beam emitted from the X-ray source 1 is held by the subject holder 3 and irradiated to the subject 2 positioned by the subject positioning mechanism 4.
  • the X-ray beam transmitted through the subject 2 is detected by the X-ray image detector 5.
  • the detection result of the X-ray image detector 5 is given to the control unit 6.
  • the control unit 6 executes setting of irradiation conditions (energy change, etc.) of the X-ray source 1 and imaging processing of a projected image (background image and transmission image) under each energy according to a measurement procedure described later.
  • the estimated content rate calculation unit 7 receives images captured by three or more types of X-rays having different average energies and executes the above-described repetitive calculation to obtain the content rate of the elements contained in the subject.
  • the processing operations of the control unit 6 and the estimated content rate calculation unit 7 are realized, for example, through execution of a program by a computer (computer).
  • the program is stored in a storage device (not shown).
  • part or all of the processing operations executed by the control unit 6 and the estimated content rate calculation unit 7 may be realized as an ASIC or a dedicated calculation module.
  • the display device 8 displays an image (element map) representing the calculated spatial distribution of each element on the display screen based on the calculation result of the estimated content calculation unit 7.
  • the display device 8 is connected to the estimated content rate calculation unit 7, but the printing device as the output device is replaced with the display device 8 or together with the display device 8 in the estimated content rate calculation unit 7. It may be connected.
  • the printing apparatus prints the element map described above. Further, instead of the display device 8 or together with the display device 8, a communication device may be connected so that transmission to an external device is possible.
  • Step S11 The control unit 6 transmits a drive signal to a drive unit (x-axis direction drive device, y-axis direction drive device, z-axis direction drive device) (not shown) of the subject positioning mechanism 4, and the subject 2 is an X-ray beam.
  • a coordinate for example, X1 located at the center is set. If necessary, a coordinate Y1 on the y axis and a coordinate Z1 on the z axis are also set.
  • Step S12 The controller 6 moves the subject 2 to a position X0 where the subject 2 is completely retracted from the X-ray beam.
  • the completely retracted position means a position where the X-ray beam does not pass through the subject 2.
  • Step S13 The control unit 6 sets the irradiation condition of the X-ray source 1.
  • the control unit 6 selects one of n setting conditions (n is 3 or more) set in advance.
  • the irradiation condition corresponds to any of the energy E1 to En.
  • the setting order here may be determined in advance or one of the setting conditions that are not used may be selected each time.
  • Step S14 The control unit 6 controls the X-ray source 1 to irradiate the X-ray beam, and the intensity I o is detected by the X-ray image detector 5.
  • the X-ray beam in this step does not pass through the subject 2. Therefore, the X-ray image detector 5 acquires a background image of the subject 2 (a projection image that is the background of the subject 2).
  • Step S15 The control unit 6 transmits a drive signal to a drive unit (an x-axis direction drive device, a y-axis direction drive device, and a z-axis direction drive device) (not shown) of the subject positioning mechanism 4 and changes the coordinates from X0 to coordinates X1. change. Thereby, the subject 2 is positioned at the center of the X-ray beam.
  • a drive unit an x-axis direction drive device, a y-axis direction drive device, and a z-axis direction drive device
  • Step S16 The control unit 6 controls the X-ray source 1 to irradiate the X-ray beam, and detects the intensity I by the X-ray image detector 5.
  • the X-ray beam in this step passes through the subject 2. Therefore, the X-ray image detector 5 acquires a transmission image of the subject 2.
  • Step S17 The controller 6 determines whether or not the measurement (imaging) of the background image and the transmission image has been completed for all irradiation conditions set in advance. When the irradiation conditions that are not used for measurement (imaging) remain, the control unit 6 returns to step S12. This operation is repeated for all irradiation conditions.
  • a background image and a transmission image are acquired for one energy at a time, but after acquiring a background image for all the energy as in steps S ⁇ b> 1 and S ⁇ b> 2 of FIG. 1 described above, You may acquire a transmission image about all the energy anew.
  • step S13 the tube voltage may be changed to a preset voltage, and each projection image (background image and transmission image) may be captured.
  • X-rays used for capturing the projected image X-rays generated by radiated light or inverse Compton scattering can be used.
  • the energy of these X-rays cannot be easily changed by changing the conditions of the source. Therefore, it is necessary to newly provide a mechanism capable of changing the energy distribution of the generated X-rays between the X-ray source and the subject.
  • a crystal spectrometer that can extract only X-rays having specific energy using X-ray diffraction is installed.
  • FIG. 7 shows an example of a double crystal spectrometer.
  • the two-crystal spectrometer here is composed of a rotary stage 71 and two single crystal plates 72 and 73 disposed on the upper surface thereof, and the two single crystal plates 72 and 73 are parallel to each other so as to sandwich the rotation axis. Is arranged.
  • the rotation stage 71 is rotated by a predetermined angle around the rotation axis, and the incident angle of the white X-rays with respect to the single crystal plate 72 is changed.
  • a monochromatic X-ray having a corresponding energy can be output toward the subject.
  • FIG. 8 shows an example of a rotating revolver type energy changing mechanism (also referred to as a metal foil rotating mechanism) in which a plurality of metal plates having different thicknesses and types are arranged along the circumferential direction of the disc.
  • the type and thickness of the metal film 82 through which X-rays pass are changed in a very short time by rotating the disk 81 (that is, the X-ray energy is changed). Can do.
  • the method for obtaining the content rate of the element contained in the subject from the plurality of projection images acquired with the X-rays of different energy described above is divided into the following cases (1) and (2). It is good to handle. (1) When the number of contained elements is less than the number of projected images (2) When there are more projections (including unknown cases)
  • the direct search method searches for a direction in which the square sum of the difference between the theoretical synthetic absorption coefficient ⁇ Ic calculated from the expected content and the relative measured absorption coefficient ⁇ ′ obtained by measurement becomes smaller.
  • This method is intuitive and has the advantage of being able to monitor the iteration process, but has the feature of slow convergence.
  • the differential coefficient of the function related to the content rate is calculated in each process of the iterative calculation, and a condition (content rate) that minimizes the sum of squares of the difference in the direction in which the deviation becomes smaller is searched. Is the method.
  • the convergence speed of these methods is faster than the convergence speed of the direct search method, it is less affected by the initial value and often converges to a minimum point.
  • the X-ray imaging apparatus performs the above-described calculation processing for each pixel (pixel) of a plurality of projection images acquired for X-rays having different energies, and obtains the content rate for each element for each pixel. Thereafter, a spatial distribution image of the selected element is displayed on the display device 8 in accordance with an operator instruction. In addition, if it is possible to display a composite image of the projected image and element content ratio image at the selected energy, the operator can better understand what structure of the element is distributed. It can be easy.
  • Example 2 When the number of elements contained in the subject is larger than the number of projection images or when the number of elements is completely unknown, the X-ray imaging apparatus described in the first embodiment results in a nonlinear optimization problem, and the optimum value (Content) is obtained by repeated calculation.
  • the direct search method may converge to a local minimum value (minimum value) and may not be able to accurately determine the content. . Therefore, in this example, a method for improving the reliability of the obtained solution by setting the content rate predicted from the measured absorption coefficient as the initial content rate will be described.
  • the linear absorption coefficient ⁇ i of each element has a unique value for each energy of the X-ray, and the amount of change in the linear absorption coefficient ⁇ i between two specific energies is also determined. It will have a unique value. Therefore, the X-ray imaging apparatus according to the present embodiment sets the initial value of the content rate by the method shown in FIG. First, the estimated content rate calculation unit 7 calculates the amount of change in the linear absorption coefficient between the two energies for each pixel of the transmission image acquired for each energy (step S21). Next, the estimated content calculation unit 7 theoretically calculates the amount of change in the linear absorption coefficient between the same two energies (step S22).
  • the estimated content rate calculation unit 7 compares the amount of change of the linear absorption coefficient calculated in step 21 with the theoretical amount of change calculated in step S22, and predicts the element contained in the subject (step S23). Furthermore, the estimated content rate calculation unit 7 sets initial values so that the content rates of the element predicted in step S23 and the elements in the vicinity thereof are increased (step S24).
  • the initial value obtained by the above processing is generally close to the correct solution as compared with the first embodiment. Therefore, the estimated content rate calculation unit 7 using the initial value can determine the elements included in the subject and their contents more accurately than in the first embodiment.
  • Example 3 In the case of Example 2 described above, the initial value of the content rate was determined based on a comparison between the change amount of the linear absorption coefficient ⁇ i measured between two energies and the theoretical change amount calculated theoretically. However, the initial value can be determined by other methods. This is a technique that uses a change at the absorption edge when an X-ray having a small energy step width and high monochromaticity such as radiated light is used as an X-ray source.
  • FIG. 10 shows the transmittance calculated for the metal foil assumed in FIG. 2 with a step width of 1 keV when the energy is between 7 and 35 keV.
  • the transmittance changes abruptly in the vicinity of 9, 20, and 29 keV.
  • the estimated content calculation unit 7 in this example calculates the initial content values of these elements. Set higher than other elements.
  • FIG. 11 shows processing (steps S31 to S33) executed in the estimated content rate calculation unit 7.
  • step S33 how much the element content determined in step S32 is set may be determined from information on the change in transmittance. For example, in the case of FIG. 10, since the magnitude of the change of Mo and Sn is about 1/4 with respect to the magnitude of the change of Cu, it is sufficient to set the ratio of 4: 1: 1 and other elements to about 0.5.
  • the estimated content rate calculation unit 7 calculates the element contained in the subject and its content. As compared with the first embodiment, it can be obtained more accurately.
  • Example 4 In the X-ray imaging apparatus according to the above-described embodiment, only a projection image of a subject can be acquired, and when different elements are multiplexed in the X-ray transmission direction, an accurate content rate of the element can be obtained. was difficult.
  • information related to elements is acquired from a plurality of cross-sectional images acquired at different energies in combination with an X-ray CT (Computed Tomography) method.
  • step S6 a predetermined process is performed on “measured absorption coefficient ⁇ ′” instead of “relative measured absorption coefficient ⁇ ′”.
  • FIG. 12 shows a configuration example of the X-ray imaging apparatus according to the present embodiment.
  • the X-ray imaging apparatus shown in FIG. 12 has a new sample rotation mechanism 9 that can rotate the sample with respect to the X-ray source, and the subject positioning mechanism 4
  • a control unit 160 that also controls the rotation of the sample rotation mechanism 9 and an estimated content rate calculation unit 170 that can calculate the content rate for each pixel of the cross-sectional image are used.
  • the sample rotation mechanism 9 may be of any drive system as long as it is a mechanism that is rotationally driven in one or both directions by a drive mechanism (for example, a motor) (not shown).
  • the subject positioning mechanism 4 is placed on the upper surface of the sample rotating mechanism 9.
  • the X-ray imaging procedure in the present embodiment is the same as that shown in FIG. 1 except that the X-ray image acquired for each energy is a cross-sectional image, and the element estimation process for each pixel is also executed for each pixel of the cross-sectional image. It is the same. Therefore, hereinafter, a measurement procedure for obtaining a cross-sectional image will be described with reference to FIG. The measurement procedure is executed through the control unit 160.
  • the control unit 160 performs measurement operations in the following order.
  • Step S41 The control unit 160 uses the subject positioning mechanism 4 to set coordinates (for example, X1) at which the subject 2 is positioned at the center of the X-ray beam. If necessary, a coordinate Y1 on the y axis and a coordinate Z1 on the z axis are also set.
  • coordinates for example, X1
  • a coordinate Y1 on the y axis and a coordinate Z1 on the z axis are also set.
  • Step S42 The controller 160 moves the subject 2 to the position X0 where the subject 2 is completely retracted from the X-ray beam.
  • Step S43 The controller 160 sets the irradiation conditions for the X-ray source 1. As in the case of the first embodiment, for example, one of n preset conditions (n is 3 or more) is selected.
  • the irradiation condition corresponds to any of the energy E1 to En.
  • the setting order here may be determined in advance or one of the setting conditions that are not used may be selected each time.
  • Step S44 The control unit 160 controls the X-ray source 1 to irradiate the X-ray beam, and detects the intensity I o with the X-ray image detector 5.
  • the X-ray beam in this step does not pass through the subject 2. Therefore, the X-ray image detector 5 acquires a background image of the subject 2 (a projection image that is the background of the subject 2).
  • Step S45 The control unit 160 transmits a drive signal to a drive unit (x-axis direction drive device, y-axis direction drive device, z-axis direction drive device) (not shown) of the subject positioning mechanism 4 and changes the coordinates from X0 to coordinates X1. change. Thereby, the subject 2 is positioned at the center of the X-ray beam.
  • a drive unit x-axis direction drive device, y-axis direction drive device, z-axis direction drive device
  • Step S46 The control unit 160 controls the X-ray source 1 to irradiate the X-ray beam, and the intensity I is detected by the X-ray image detector 5.
  • the X-ray beam in this step passes through the subject 2. Therefore, the X-ray image detector 5 acquires a transmission image of the subject 2 at the current rotation position of the sample rotation mechanism 9.
  • Steps S47 and S48 The control unit 160 rotates the sample rotation mechanism 9 to rotate the subject 2 with respect to the X-ray source 1 by a preset angle. Thereafter, the control unit 160 determines whether or not the position after rotation reaches a preset rotation angle, and returns to step S46 while a negative result is obtained. That is, until reaching a preset rotation angle, the X-ray image detector 5 acquires a transmission image obtained by X-ray beams incident from different angles on the same coordinates of the subject 2.
  • Step S49 The control unit 160 that has obtained a positive result in step S48 moves the subject 2 to the position X0 completely retracted from the X-ray beam.
  • Step S50 The control unit 160 acquires a background image again for the retracted position.
  • an X-ray background image having the same energy is acquired because there is a change in the energy of the X-ray output from the X-ray source 1 between the start of rotation of the subject 2 and the end of rotation. It is for confirming. If a change is detected, the intensity of the transmission image acquired for each rotation angle is corrected based on the intensity of the X-ray background image acquired in steps S44 and S50. For example, the intensity is corrected by linear interpolation.
  • Step S51 The controller 160 determines whether or not the measurement (imaging) of the background image and the transmission image has been completed for all irradiation conditions set in advance. If irradiation conditions that are not used for measurement (imaging) remain, the control unit 160 returns to step S43. This operation is repeated for all irradiation conditions. Through the above processing, transmission images with different angles and different energy are acquired for each coordinate of the subject 2.
  • the estimated inclusion The rate calculation unit 170 calculates a cross-sectional image of the subject 2 for each energy by a normal reconstruction process (filtered back projection method or the like). Thereafter, the estimated content rate calculation unit 170 performs the same process as described above for each pixel of each cross-sectional image, and calculates the content rate of each element included in each pixel. In the case of the present embodiment, since the term relating to the thickness of the subject is not included, if the number of elements is n, the content rate can be uniquely determined if there are n cross-sectional images.
  • an image representing the three-dimensional distribution of the content of each element contained in the subject is accurately obtained by repeated calculation from a plurality of cross-sectional images acquired with X-rays having different energies. Can be sought.
  • the present invention is not limited to the configuration of the embodiment described above, and includes various modifications.
  • some of the embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention does not necessarily have all the configurations described.
  • a part of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment.
  • each of the above-described configurations, functions, processing units, processing means, and the like may be partly or entirely realized as, for example, an integrated circuit or other hardware.
  • Each of the above-described configurations, functions, and the like may be realized by a processor interpreting and executing a program that realizes each function. That is, each configuration may be realized by software.
  • information such as programs, tables, and files for realizing each function can be stored in a storage device such as a memory, a hard disk, an SSD (Solid State Drive), or a storage medium such as an IC card, an SD card, or a DVD.
  • control lines and information lines indicate what is considered necessary for explanation, and do not represent all control lines and information lines necessary for the product. In practice, it can be considered that almost all components are connected to each other.
  • Reference Signs List 1 X-ray source 2 Subject 3 Subject holder 4 Subject positioning mechanism 5 X-ray image detector 6 Control unit 7 Estimated content rate calculation unit 8 Display device 9 Subject rotation mechanism 71 Rotation stage 72 Single crystal plate 73 Single crystal plate 81 Disc 82 Metal film 160 Control unit 170 Estimated content rate calculation unit

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  • Apparatus For Radiation Diagnosis (AREA)

Abstract

Selon la présente invention, pour chacun d'au moins trois types de rayonnement de rayons X avec des énergies moyennes différentes, l'intensité moyenne I0 (En, X, Y) d'une région d'arrière-plan d'un objet et l'intensité I (En, X, Y) de chaque pixel dans une image de transmission de rayons X transmis à travers la même région de l'objet sont obtenues. Pour chaque énergie moyenne, le coefficient d'absorption mesuré µ de l'objet est déterminé par division de chaque intensité I (En, X, Y) par l'intensité moyenne I0 (En, X, Y) à la même énergie moyenne, et calcul du logarithme naturel négatif (-ln (x)). L'un des au moins trois types de rayonnement de rayons X est défini en tant qu'énergie standard E0, et un coefficient d'absorption mesuré relatif µ' est calculé par division, par le coefficient d'absorption mesuré µ correspondant à l'énergie standard E0, un coefficient d'absorption mesuré µ correspondant à une autre énergie moyenne. Ensuite, le coefficient d'absorption composite théorique μIc de chaque élément attendu est calculée pour chaque énergie moyenne sur la base du coefficient d'absorption théorique μI et de la teneur σi de l'élément. La teneur σi avec laquelle la somme des carrés des différences par rapport aux coefficients d'absorption mesurés relatifs µ' calculés pour chaque énergie moyenne est la plus faible est calculée par calcul répété.
PCT/JP2014/073737 2014-09-09 2014-09-09 Procédé et dispositif d'imagerie à rayons x WO2016038667A1 (fr)

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WO2020175319A1 (fr) * 2019-02-28 2020-09-03 富士フイルム株式会社 Dispositif et programme de traitement d'images de rayonnement

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JPH0341933A (ja) * 1989-03-03 1991-02-22 Matsushita Electric Ind Co Ltd 放射線画像処理方法および撮影装置
US5854820A (en) * 1996-05-02 1998-12-29 Slijkerman; Walter Fredericus Johannes Method and meter for measuring the composition of a multiphase fluid
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020175319A1 (fr) * 2019-02-28 2020-09-03 富士フイルム株式会社 Dispositif et programme de traitement d'images de rayonnement
JPWO2020175319A1 (ja) * 2019-02-28 2021-12-02 富士フイルム株式会社 放射線画像処理装置及びプログラム
JP7098813B2 (ja) 2019-02-28 2022-07-11 富士フイルム株式会社 放射線画像処理装置及びプログラム

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