JP2005245657A - X-ray imaging equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for effectively displaying a photoelectric effect image and a Compton effect image in X-ray imaging equipment having a dual energy imaging function. <P>SOLUTION: This X-ray imaging equipment creates a composite image as an X-ray transmission image to a virtual X-ray source based on the photoelectric effect image and the Compton effect image and displays it on a single screen. This equipment is provided with a spectrum storage means 102 storing information of energy spectrum of the X-rays generated by the virtual X-ray source, and X-ray transmission image calculating means 100 and 101 calculating the X-ray transmission image of a subject relative to the virtual X-ray source based on the energy spectrum stored in the spectrum storage means and a dual energy image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an X-ray imaging technique, and more particularly to an X-ray imaging apparatus for displaying subject information acquired based on a dual energy method.

  The dual energy method is a method of calculating an X-ray attenuation amount due to a photoelectric effect and an X-ray attenuation amount due to a Compton effect in an object based on an X-ray transmission image of the object acquired by X-rays having two different energy spectra. It is. In the field of X-ray diagnostic apparatuses, since both an image (photoelectric effect image) that emphasizes a bone part of a human body and an image (Compton effect image) that emphasizes a soft tissue and the like can be acquired by a dual energy method, There is an advantage that more subject information can be provided to the examiner and the diagnostic ability of the examiner can be improved as compared with the time of taking the image.

  As a conventional example of an X-ray diagnostic apparatus using a dual energy method, for example, “The development and Characterization of a Dual-Energy Subtraction Imaging System for Chest Radiography Based on CsI: TI Amorphous Silicon Flat-Panel Technology”, Proc. SPIE, Vol. 4320, pp399-408, 2001 etc.

  According to U.S. Pat. No. 4,029,963, the signal intensity of a captured image obtained in dual energy imaging is expressed by (Equation 1) and (Equation 2).

ただし、k_p、 k_cは比例定数、εはＸ線のエネルギー、S₁(ε)、S₂(ε)は被写体に入射するＸ線のエネルギースペクトルである。また、L_pおよびL_cはそれぞれ光電効果によるＸ線減衰量、コンプトン効果によるＸ線減衰量であり、それぞれ（数３）、（数４）で示される。

Here, k _p and k _c are proportional constants, ε is X-ray energy, and S ₁ (ε) and S ₂ (ε) are X-ray energy spectra incident on the subject. L _p and L _c are the X-ray attenuation due to the photoelectric effect and the X-ray attenuation due to the Compton effect, respectively, and are expressed by (Equation 3) and (Equation 4), respectively.

ただし、sをＸ線ビームライン上の位置とし、ρ(s)、w(s)、およびZ(s)をそれぞれ位置sにおける被写体の密度、原子量、および原子番号とする。更に、（数１）および（数２）において、f_KN(ε)は単一電子に対するコンプトン散乱確率あり、（数５）に示すKlein-Nishinaの式で与えられる。

Here, s is a position on the X-ray beam line, and ρ (s), w (s), and Z (s) are the density, atomic weight, and atomic number of the subject at the position s, respectively. Further, in (Equation 1) and (Equation 2), f _KN (ε) has the Compton scattering probability for a single electron, and is given by the Klein-Nishina equation shown in (Equation 5).

ただし、α＝ε/mc²（mは電子の静止質量、cは光速）とする。デュアルエネルギー法は異なるエネルギースペクトルS₁(ε)、S₂(ε)を有するＸ線に対して得られた２つの検出信号I₁、I₂に基づいて、L_p、L_cを計算する方法である。なお以下では、全ての画素においてL_p、L_cを計算して得た画像をそれぞれ光電効果像、コンプトン効果像と呼ぶ。

Where α = ε / mc ² (m is the static mass of the electron, and c is the speed of light). In the dual energy method, L _p and L _c are calculated based on _two detection signals I ₁ and I ₂ obtained for X-rays having different energy spectra S ₁ (ε) and S ₂ (ε). It is. Hereinafter, images obtained by calculating L _p and L _c in all pixels are referred to as a photoelectric effect image and a Compton effect image, respectively.

As a conventional example of the above calculation method, for example, US Pat. No. 4,029,963 and H. Neale et al. “An accurate method for direct dual-energy calibration and decomposition”, Med. Phys. 17 (3), pp 327 -341, 1990 etc. Considering that the atomic weight w is substantially proportional to the atomic number Z, L _p is substantially proportional to ρZ ³ from (Equation ³ ). Therefore, in the photoelectric effect image, an object having a relatively large atomic number, such as a bone or a catheter inside a human body, is emphasized. On the other hand, since L _c is proportional to ρ from (Equation 4), the density change of the soft tissue inside the human body is emphasized in the Compton effect image.

J. M. Sabol, et al: “The development and Characterization of a Dual-Energy Subtraction Imaging System for Chest Radiography Based on CsI: TI Amorphous Silicon Flat-Panel Technology”, Proc. SPIE, Vol. 4320, pp 399-408, 2001

U.S. Pat. No. 4,029,963 H. Neale, et al .: “An accurate method for direct dual-energy calibration and decomposition”, Med. Phys. 17 (3), pp 327-341, 1990.

  In the X-ray diagnostic apparatus using the dual energy method, a conventional photoelectric effect image and a Compton effect image are individually displayed. For this reason, the examiner needs to compare two images, and there is a problem that it takes time for diagnosis. In addition, there is a problem that it is difficult to grasp the positional relationship between the attention sites included in each image. Furthermore, there is a problem that the examiner cannot arbitrarily select an intermediate image between the two images.

  An object of the present invention is to provide an X-ray imaging apparatus capable of effectively displaying a photoelectric effect image and a Compton effect image in an X-ray imaging apparatus having a dual energy imaging function.

  Details of the objects and novel features of the present invention will become apparent from the following description and the accompanying drawings.

  In order to achieve the above object, in the present invention, in order to create a single image by synthesizing the photoelectric effect image and the Compton effect image, a composite image is created by assuming a virtual X-ray source (Equation 6). This is the basic configuration.

ただし、S(ε)は仮想Ｘ線源より発生するＸ線のエネルギースペクトルとする。

Here, S (ε) is the energy spectrum of X-rays generated from the virtual X-ray source.

As an example, assuming a monochromatic X-ray as a virtual X-ray source, S (ε) = ε. At this time, the photoelectric effect image and the Compton effect image can be synthesized at various ratios using ε as a parameter. When ε is small, the term of L _p / ε ³ becomes large in (Equation 6), and the synthesized image approaches a photoelectric effect image. On the other hand, when ε is large, the term of L _p / ε ³ becomes small in (Equation 6), and the synthesized image approaches the Compton effect image. Therefore, the ratio of the photoelectric effect image and the Compton effect image in the composite image can be arbitrarily selected by the examiner freely changing the value of ε.

Assuming an X-ray tube as another example of the virtual X-ray source, since the energy spectrum changes depending on the tube voltage V, it can be expressed as S (ε) = S _V (ε). At this time, S _V (ε) is a known method (for example, “Computation of Bremsstrahlung X-ray Spectra and Comparison with Spectra Measured with a Ge (Li) Detector” by R. Birch et al., Phys. Med. Biol., Vol. 24, No. 3, pp 505-517, 1979 (hereinafter referred to as Reference 1)).

  When V is small, the X-ray energy is small, so the composite image approaches a photoelectric effect image. On the other hand, when V is large, the energy of X-rays increases, so that the synthesized image approaches a Compton effect image. Accordingly, the examiner can freely select the ratio of the photoelectric effect image and the Compton effect image in the composite image by freely changing the value of V. In addition, at intermediate V (about 50 kV to 120 kV), the synthesized image becomes an image equivalent to a normal X-ray image taken at the corresponding tube voltage, so the examiner can use a photoelectric effect image, a normal photographed image, and a Compton. The composite image can be arbitrarily changed between effect images.

Note that the value of the energy spectrum S _V (ε) of the X-ray tube may be recorded in advance in the memory as a result of actual measurement or calculated by the method described in Reference 1, or calculated during image synthesis. May be.

  Further, the composite image calculated in (Equation 6) assumes a detection image by a photon counter type X-ray detector, but when simulating a general charge storage type X-ray detector, (Equation 7) may be used instead of 6).

（数７）では、Ｘ線のエネルギーεに比例した強度の信号が検出される。

In (Expression 7), a signal having an intensity proportional to the X-ray energy ε is detected.

  By using the above method, for example, in image diagnosis, the examiner can make a diagnosis while changing the synthesized image in various ways on the same screen without impairing the position information of the site of interest. As a result, it is not necessary to compare a plurality of images as in the prior art, and the diagnosis can be made more efficient.

  Hereinafter, typical configuration examples of the present invention will be described.

  (1) An X-ray imaging apparatus of the present invention includes an X-ray generation unit that generates X-rays having two different types of energy spectra, and an X-ray detection unit that detects the two types of X-rays after being transmitted through a subject. And an X-ray imaging apparatus for generating a dual energy image of the subject based on two types of detection signals detected by the X-ray detection means, and information on energy spectrum of X-rays generated from a virtual X-ray source And X-ray transmission image calculation means for calculating an X-ray transmission image of the subject with respect to the virtual X-ray source based on the energy spectrum stored in the spectrum storage means and the dual energy image. It is characterized by that.

  (2) The X-ray imaging apparatus according to (1), further including spectrum calculation means for calculating an energy spectrum of X-rays generated from the virtual X-ray source, wherein the energy spectrum calculated by the spectrum calculation means Information is stored in the spectrum storage means.

  (3) In the X-ray imaging apparatus according to (1) or (2), tube voltage setting means for setting a tube voltage of the X-ray tube assuming an X-ray tube as the virtual X-ray source, and the tube voltage Spectrum selection means for selecting and reading out the energy spectrum corresponding to the tube voltage set by the setting means from the spectrum information storage means, and based on the selected energy spectrum and the dual energy image, An X-ray transmission image is calculated.

  (4) The X-ray imaging apparatus of the present invention includes an X-ray generation unit that generates X-rays having two different types of energy spectra, and an X-ray detection unit that detects the two types of X-rays after being transmitted through the subject. And calculating an energy spectrum of X-rays generated from a virtual X-ray source in an X-ray imaging apparatus that generates a dual energy image of the subject based on two types of detection signals detected by the X-ray detection means Spectrum calculation means for performing X-ray transmission image calculation means for calculating an X-ray transmission image of the object with respect to the virtual X-ray source based on the energy spectrum calculated by the spectrum calculation means and the dual energy image. It is characterized by that.

  (5) The X-ray imaging apparatus according to (4), further including tube voltage setting means for setting a tube voltage of the X-ray tube assuming an X-ray tube as the virtual X-ray source, and the tube voltage setting means The X-ray transmission image of the subject is calculated based on the energy spectrum calculated by the spectrum calculation unit corresponding to the tube voltage set in step (b) and the dual energy image.

  (6) In the X-ray imaging apparatus according to (4), there is provided a monochromatic energy setting means for setting monochromatic X-ray energy generated from the monochromatic X-ray source assuming a monochromatic X-ray source as the virtual X-ray source. The X-ray transmission image of the subject is calculated based on the energy set by the monochromatic energy setting means and the dual energy image.

  According to the present invention, based on a photoelectric effect image and a Compton effect image acquired by an X-ray imaging apparatus having a dual energy imaging function, these composite images can be displayed while being variously changed on the same screen. As a result, there is no need to compare a plurality of images as in the prior art, and the diagnosis can be made more efficient.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining the configuration of an X-ray imaging apparatus according to an embodiment of the present invention. The X-ray imaging apparatus according to this embodiment includes an X-ray tube 1, a collimator 2, an X-ray grid 3, an X-ray detector 4, a column 5, a bed top 7, a bed 8, a monitor 9, a console 10, and an image memory 100. , Signal processing means 101, energy spectrum recording memory 102, image recording means 105, and the like. In addition to a known instruction mechanism for instructing X-ray imaging and a known setting mechanism for setting imaging conditions, the console 10 includes a virtual X-ray source selection unit 103 and a virtual X-ray condition setting unit 104. Is provided.

  Hereinafter, a configuration including the X-ray tube 1, the collimator 2, the X-ray grid 3, and the X-ray detector 4 is referred to as an imaging system. A known device is used for each component of the photographing system. The collimator 2 is fixed to the front surface of the X-ray tube 1 and has a function of limiting the X-ray irradiation range to the subject 6. The X-ray grid 3 is fixed to the front surface of the X-ray detector 4 and has a function of reducing scattered X-rays generated in the subject 6. The entire photographing system is supported by the support 5.

  A typical example of the distance between the X-ray generation point of the X-ray tube 1 and the input surface of the X-ray detector 4 is 110 [cm]. A known FPD (Flat Panel Detector) or the like is used for the X-ray detector 4. A typical example of the specification of the X-ray detector 4 is an input surface size of 307.2 [mm] × 307.2 [mm] and the number of pixels of 2048 [pixels] × 2048 [pixels]. The X-ray detector 4 has an imaging mode and a fluoroscopic mode, and a representative example of the frame rate in the fluoroscopic mode is 30 [frame / second]. A typical example of the specification of the X-ray grid 3 is a grid ratio (lattice ratio) of 12: 1 and a grid density of 70 [lines / cm]. Note that the above specifications are not limited to these values, and can be variously changed according to the configuration of the X-ray imaging apparatus.

  Next, an operation procedure of the X-ray imaging apparatus according to the present embodiment will be described. The X-ray imaging apparatus has a dual energy X-ray fluoroscopy / imaging function in addition to a general X-ray fluoroscopy / imaging function. In the following, an operation procedure at the time of dual energy X-ray fluoroscopy / imaging for which the present invention is utilized will be described. The operation procedure at the time of general X-ray fluoroscopy / imaging can be the same as that of a known X-ray fluoroscopy / imaging apparatus.

  Dual energy X-ray fluoroscopy / imaging comprises a fluoroscopy mode, a radiographing mode, and a reproduction mode. The operation procedure in each mode will be described below.

In the fluoroscopic mode, the examiner first instructs the start of X-ray fluoroscopy through the console 10, and X-rays are emitted from the X-ray tube 1. During X-ray fluoroscopy, pulsed X-rays are emitted in time series. The pulses are synchronized with the frame rate of the X-ray detector 4, and an X-ray transmission image for each pulse is detected by the X-ray detector 4. The tube voltage of the X-ray tube 1 is alternately repeated between a high voltage (V _H ) and a low voltage (V _L ) for each pulse. The values of V _H and V _L are set in advance by the examiner prior to fluoroscopy. Typical examples of the set values of V _H and V _L are 120 [kV] and 70 [kV], respectively. Note that the values of V _H and V _L may be automatically set by a known X-ray condition control mechanism. X-ray transmission image data of the subject 6 detected for each pulse by the X-ray detector 4 is recorded in the image memory 100. In the image memory 100, an area 100H for recording data of an X-ray transmission image at V _H (hereinafter referred to as V _H transmission image) and an X-ray transmission image at V _L (hereinafter referred to as V _L transmission image). ) Is recorded separately, and data newly acquired with each pulse is overwritten in the corresponding storage area. If specified by the examiner, the moving image data of the V _H transmission image and the V _L transmission image acquired in time series can be recorded in the image recording means 105. For the image recording means 105, a known recording device such as a hard disk can be used. Each time new data is recorded in the image memory 100, the signal processing means 101 reads out the data of the V _H transmission image and the V _L transmission image from the image memory 100, and uses a method to be described later for a dual energy image (photoelectric) Effect image and Compton effect image). Further, the signal processing means 101 creates a composite image of the dual energy image by a method described later and displays it on the monitor 9. A series of operations from acquisition of the X-ray transmission image to display of the composite image on the monitor 9 is repeated every time the X-ray transmission image is acquired, and the examiner can observe the moving image of the composite image on the monitor 9. The above series of operations is repeated until the examiner instructs the end of the fluoroscopy through the console 10.

In the imaging mode, the examiner first instructs the start of X-ray imaging using the console 10, and X-rays are emitted from the X-ray tube 1. At this time, pulsed X-rays are repeatedly emitted twice at short time intervals. A typical example of the pulse interval is 200 [ms]. In each pulse, the tube voltage of the X-ray tube 1 is set to a high voltage (V _H ) and a low voltage (V _L ). The values of V _H and V _L are set in advance by the examiner prior to imaging. Typical examples of set values of V _H and V _L are 140 [kV] and 80 [kV], respectively. Note that the values of V _H and V _L may be automatically set by a known X-ray condition control mechanism. In the two pulses, the V _H transmission image and the V _L transmission image acquired by the X-ray detector 4 are recorded in the area 100H and the area 100L in the image memory 100, respectively. If the examiner does not give an instruction, the data of the V _H transmission image and the V _L transmission image are also recorded in the image recording means 105. The signal processing unit 101 records the V _H transmission image and the V _L transmission image in the image memory 100 and simultaneously reads them, and creates a dual energy image of the subject 6 by a method described later. Further, the signal processing unit 101 creates a composite image of the dual energy image by a method described later and displays it on the monitor 9.

  In the reproduction mode, a composite image is created based on the fluoroscopic data and photographing data recorded in the image recording means 105. The examiner uses the console 10 to select data to be reproduced from the data recorded in the image recording means 105. The selected reproduction data is read out and recorded in the image memory 100. The signal processing means 101 reads out the reproduction data at the same time as it is recorded in the image memory 100 and creates a dual energy image of the subject 6 by a method described later. Further, the signal processing unit 101 creates a composite image of the dual energy image by a method described later and displays it on the monitor 9. When the selected reproduction data is fluoroscopic data, a series of operations from reading the reproduction data to displaying the composite image on the monitor 9 is repeated for each frame, and the examiner displays the composite image on the monitor 9. I can observe.

  At the time of creating a composite image, the examiner can set a composite image creation condition via the virtual X-ray source selection unit 103 and the virtual X-ray condition setting unit 104. The virtual X-ray source selection unit 103 and the virtual X-ray condition setting unit 104 can be realized by a known setting instrument such as a selection button or a knob, or a setting bar displayed on the monitor 9. The examiner selects whether the virtual X-ray source is a monochromatic X-ray source or an X-ray tube via the virtual X-ray source selection means 103. Further, the examiner, via the virtual X-ray condition setting means 104, determines the energy of the monochromatic X-ray when the monochromatic X-ray source is selected as the virtual X-ray source and the tube voltage when the X-ray tube is selected. Can be set. A typical example of the setting range of the monochromatic X-ray energy is 30 [keV] to 120 [keV]. A typical example of the setting range of the tube voltage is 30 [kV] to 160 [kV]. Note that the composite image creation conditions can be variously changed during the display of a moving image such as a perspective image or the display of a still image such as a captured image. In addition, the synthetic image creation conditions can be changed during fluoroscopy. If a method described later is used, the composite image can be displayed while being dynamically changed in accordance with the change in the composite image creation conditions.

  When the X-ray tube is selected by the virtual X-ray source selection unit 103, the signal processing unit 101 reads out energy spectrum data corresponding to the tube voltage set through the virtual X-ray condition setting unit 104 from the energy spectrum recording memory 102. Then, a composite image is created using a method described later. As the energy spectrum data recorded in the energy spectrum recording memory 102, data measured in advance at various tube voltages with respect to the X-ray tube 1 may be used, or publicly known documents (for example, “Catalogue” by Birch et al. of Spectral Data for Diagnostic X-rays ", Hospital Physicists' Association, 1979 (hereinafter referred to as Reference 2)) may be used.

  Further, if the method described in Reference Document 1 described above is used, energy spectrum data can be calculated for an arbitrary tube voltage. Therefore, calculation values for various tube voltages may be recorded in the energy spectrum recording memory 102 in advance, or the tube voltage set by the virtual X-ray condition setting means 104 may be set without providing the energy spectrum recording memory 102. Accordingly, the energy spectrum may be calculated each time.

  FIG. 2 is a block diagram for explaining a composite image creation procedure in the signal processing means 101. The processing procedure of the signal processing means 101 will be described below based on this block diagram. The following processing by the signal processing means 101 can be realized by program control for a dedicated arithmetic unit or a known general-purpose arithmetic unit.

  In step 200, the examiner designates X-ray fluoroscopy in the fluoroscopic mode, X-ray radiography in the radiographing mode, or image reproduction in the reproduction mode via the console 10, and at the same time, the following processing by the signal processing unit 101 is started. . In step 201, the recorded image is read with reference to the image memory 100. In step 202, it is determined whether the image recorded in the image memory 100 is a new image or not. If the image is a new image, the process proceeds to step 204; otherwise, the process proceeds to step 203. In step 203, it is determined whether or not a change has been made to the composite image creation condition via the virtual X-ray source selection unit 103 or the virtual X-ray condition setting unit 104. If there is a change, the process proceeds to step 205. If there is no change, the process proceeds to step 210. In step 204, a dual energy conversion operation is performed on the new image recorded in the image memory 100 to create a dual energy image. Note that the methods described in Patent Document 1 and Non-Patent Document 2 described above can be used to create a dual energy image. In step 205, the type of the X-ray source selected by the virtual X-ray source selection means 103 is determined. When the monochromatic X-ray source is selected, the process proceeds to step 206, and when the X-ray tube is selected, the process proceeds to step 207. In step 206, the energy value of the monochrome X-ray designated via the virtual X-ray condition setting means 104 is referred. In step 207, the tube voltage of the X-ray tube designated via the virtual X-ray condition setting means 104 is referred. In step 208, the energy spectrum corresponding to the specified tube voltage of the X-ray tube is read from the energy spectrum recording memory 102. In step 209, based on the dual energy image and the designated composite image creation condition, a composite image is created using (Equation 7). In addition, when there exists designation | designated by an examiner, you may produce a synthesized image using (Formula 6). In step 210, the created composite image is displayed on the monitor 9. In step 211, it is determined whether the examiner has designated the end of X-ray fluoroscopy, X-ray imaging, or image reproduction via the console 10. If the end is designated, the process proceeds to step 212. If not designated, the process returns to step 201. In step 212, the above series of processing by the signal processing means 101 is terminated.

  When displaying a moving image such as a perspective image, a series of processing from step 201 to step 210 is repeatedly performed in synchronization with the frame rate of the moving image. Thereby, since a synthesized image can be created with respect to each frame image in the movie, the synthesized image can be displayed as a movie. Further, even when the composite image creation condition changes during the moving image display, the composite image can be created and displayed while dynamically responding to the condition change. On the other hand, when displaying a still image such as a photographed image, a series of processing from step 201 to step 210 is repeated to create a composite image while dynamically responding to changes in the composite image creation conditions. Can be displayed.

In step 209, when creating a composite image using (Equation 6) or (Equation 7), the X-ray absorption coefficient constant term k _p due to the photoelectric effect and the X-ray absorption coefficient constant term k _c due to the Compton effect are used. A value is used. k _p and k _c are ideally constant terms that do not depend on the composition of the subject or the energy of the X-ray, but actually have some degree of dependence. Therefore, in order to create a composite image with high accuracy, it is necessary to set appropriate values in advance as k _p and k _c . If the subject 6 is assumed to be a human body, for example, the composition can be approximated with water or the like.

3 and 4 show the relationship between water k _p and k _c and energy. As shown in FIG. 3 and FIG. 4, k _p and k _c have energy dependence, so if these are expressed as k _p (ε) and k _c (ε) and equations 6 and 7 are calculated, A composite image can be calculated with relatively high accuracy. In order to simplify the calculation, k _p and k _c may be approximated by constants. For example, if the range of the X-ray energy used in the virtual X-ray source is 30 [keV] to 160 [keV], the approximation accuracy is greatly impaired if k _p = 13 and k _c = 0.11 are set. A composite image can be calculated without any problem.

  As described above, when the X-ray imaging apparatus shown in this embodiment is used, X-ray transmission to a virtual X-ray source is based on two images (photoelectric effect image and Compton effect image) acquired using the dual energy method. A composite image as an image can be created. Further, the composition ratio of the composite image can be variously changed by changing the energy of the virtual X-ray source and the tube voltage. In particular, when an X-ray tube is used as a virtual X-ray source, the synthesized image can be arbitrarily changed between a photoelectric effect image, a normal radiographed image, and a Compton effect image, so that the examiner does not impair the position information of the region of interest. Diagnosis can be made while variously changing the composite image on the same screen. As a result, it is not necessary to compare a plurality of images as in the prior art, and the diagnosis can be made more efficient.

  As mentioned above, although the Example of this invention was shown, this invention is not limited only to this Example, and can be variously changed in the range which does not deviate from the summary. For example, it goes without saying that the present invention can be applied to an X-ray imaging apparatus having no fluoroscopic function, an image processing apparatus having only an image reproduction / processing function, an industrial X-ray imaging apparatus, and the like.

  According to the present invention, based on the photoelectric effect image and the Compton effect image acquired by the X-ray imaging apparatus having the dual energy imaging function, these synthesized images are displayed on the same screen without impairing the position information of the site of interest. Can be displayed with various changes. As a result, there is no need to compare a plurality of images as in the prior art, and the diagnosis can be made more efficient.

It is a figure for demonstrating the structure of the X-ray imaging apparatus which concerns on one Example of this invention. It is a block diagram for demonstrating the synthetic | combination image preparation procedure in the signal processing means shown in FIG. Is a diagram showing an X-ray absorption coefficient constant term k _p and energy relationship by the photoelectric effect of the water. Is a diagram showing an X-ray absorption coefficient constant term k _c and energy relationships by Compton effect of water.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... Collimator, 3 ... X-ray grid, 4 ... X-ray detector, 6 ... Subject, 9 ... Monitor, 10 ... Console, 100 ... Image memory, 101 ... Signal processing means, 102 ... Energy Spectrum recording memory, 103... Virtual X-ray source selection means, 104... Virtual X-ray condition setting means, 105.

Claims (6)

  X-ray generation means for generating X-rays having two different types of energy spectra, and X-ray detection means for detecting the two types of X-rays after passing through the subject, detected by the X-ray detection means In an X-ray imaging apparatus that generates a dual energy image of the subject based on two types of detection signals, a spectrum storage unit that stores information on an X-ray energy spectrum generated from a virtual X-ray source, and the spectrum storage unit An X-ray imaging apparatus comprising: X-ray transmission image calculation means for calculating an X-ray transmission image of the subject with respect to the virtual X-ray source based on the energy spectrum stored in the image and the dual energy image.   It has spectrum calculation means for calculating the energy spectrum of X-rays generated from the virtual X-ray source, and stores information on the energy spectrum calculated by the spectrum calculation means in the spectrum storage means. The X-ray imaging apparatus according to claim 1.   Assuming that the virtual X-ray source is an X-ray tube, tube voltage setting means for setting the tube voltage of the X-ray tube, and an energy spectrum corresponding to the tube voltage set by the tube voltage setting means is the spectrum information. 3. A spectrum selection unit that selects and reads out from a storage unit, and calculates an X-ray transmission image of the object based on the selected energy spectrum and the dual energy image. The X-ray imaging apparatus described.   X-ray generation means for generating X-rays having two different types of energy spectra, and X-ray detection means for detecting the two types of X-rays after passing through the subject, detected by the X-ray detection means In an X-ray imaging apparatus that generates a dual energy image of the subject based on two types of detection signals, a spectrum calculation unit that calculates an energy spectrum of X-rays generated from a virtual X-ray source, and the spectrum calculation unit An X-ray imaging apparatus comprising: X-ray transmission image calculation means for calculating an X-ray transmission image of the subject with respect to the virtual X-ray source based on the calculated energy spectrum and the dual energy image.   Assuming that the virtual X-ray source is an X-ray tube, tube voltage setting means for setting the tube voltage of the X-ray tube is provided, and the spectrum calculation corresponding to the tube voltage set by the tube voltage setting means 5. The X-ray imaging apparatus according to claim 4, wherein an X-ray transmission image of the subject is calculated based on the energy spectrum calculated by the means and the dual energy image.   Assuming that the virtual X-ray source is a monochromatic X-ray source, it has monochromatic energy setting means for setting the energy of monochromatic X-rays generated from the monochromatic X-ray source, and the energy set by the monochromatic energy setting means The X-ray imaging apparatus according to claim 4, wherein an X-ray transmission image of the subject is calculated based on the dual energy image.

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