JP3864262B2 - X-ray CT for diagnosis - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention irradiates a subject with primary reflected light and n-order reflected light obtained by, for example, entering X-rays having a wide range of energy from an accelerator into a spectrometer, and based on the transmitted light of the subject. The present invention relates to diagnostic X-ray CT (Computed Tomography) for capturing an image of a subject.
[0002]
[Prior art]
Since conventional diagnostic X-ray CT uses X-rays of an X-ray tube, it includes X-rays with a wide range of energy. The higher the energy of X-ray, the better the transmittance. Therefore, if the thickness of the subject changes, the energy component of the X-ray after transmission changes. This is called beam hardening, which causes an error in the CT value obtained by X-ray CT.
[0003]
On the other hand, when monochromatic X-rays with only one energy are used, this beam hardening phenomenon does not occur and the CT value accuracy is improved.
[0004]
Next, it will be described that the electron density distribution can be obtained by using monochromatic X-rays of two energies. The X-ray attenuation coefficient μ can be expressed in terms of photoelectric effect and Nishina-Klein by approximation such as CMTasi.
[0005]
μ (E) = K _A (ρn _o ) <Z> E ⁻³ + K _B (ρn _o ) f (E) (1)
K _A , K _B : constant, ρn. : Electron density (cm ^-3 ), <Z>: average atomic number, where the transmittance is T, the relationship with the attenuation coefficient μ is
T (E) = exp (−∫μ (E, x) dx) = exp (−μ (E) t) (2)
It can be expressed. x is the distance in the X-axis direction, and t is the thickness of the subject, where μ (E) is S = TI (3 where S is the intensity of transmitted light regardless of location and I is the intensity of incident light. )
In equation (3), when using monochromatic X-rays of _two energies E ₁ and E ₂ , it becomes a simultaneous equation,
S ₁ = I ₁ (E ₁ ) T ₁ + I ₁ (E ₂ ) T ₂
S ₂ = I ₂ (E ₁ ) T ₁ + I ₂ (E ₂ ) T ₂
When abbreviated, the following equation is obtained.
[0006]
S ₁ = I ₁₁ T ₁ + I ₁₂ T ₂
S ₂ = I ₂₁ T ₁ + I ₂₂ T ₂ (4)
When X-rays of two energies are selected (one is made zero) or the intensity ratio is changed and the intensity is known, the equation (4) is solved and the transmittances T ₁ and T ₂ Is obtained.
[0007]
Information on the electron density distribution can be obtained from the equations (1) and (2). This electron density distribution is data that is required when determining the range of particles in the body, which is necessary in a treatment plan for particle beam cancer treatment.
[0008]
Although an error of several percent cannot be avoided in the approximation from the conventional CT value, this method can directly obtain the electron density distribution, so that the accuracy of the treatment plan is improved.
[0009]
As described above, it has been understood that monochromatic X-ray CT, particularly two-energy monochromatic X-ray CT, is effective. However, in order to use this, it is necessary to switch between the two monochromatic X-rays at high speed. In energy selection, white light is dispersed using a crystal such as silicon or germanium.
[0010]
On the other hand, regarding the beam size, the radiated light has a narrow divergence angle. Since the divergence angle is not so large, a considerably long transmission distance is required, and the beam line apparatus becomes long.
[0011]
As an example, if the vertical spread angle is 0.25 mrad, a transmission distance of 200 m or more is required to expand the beam to 50 mm. Therefore, the asymmetrical reflection of the crystal is used to expand the beam, shorten the distance, and irradiate the subject.
[0012]
By the way, since the light emitted from the two-crystal spectrometer irradiates the subject, it is necessary to have the same beam size with the same optical axis even if the energy of the X-ray changes. Therefore, a conventional method for satisfying this specification using asymmetric reflection will be described below.
[0013]
To extract X-rays of necessary energy from white light, crystal Bragg reflection is used. The relationship of Bragg reflection is expressed by equation (5).
[0014]
λn = 2dsinθ (5)
λ: wavelength, d: crystal constant, θ: Bragg angle, n: order Therefore, the wavelength (energy) of the reflected light varies depending on the crystal and the incident angle.
[0015]
Also, asymmetric reflection of crystals is used to expand the beam. The magnification factor M and the asymmetric reflection angle α at that time can be expressed by equations (6) and (7).
[0016]
M = sin (θ + α) / (θ−α) (6)
α = tan ⁻¹ [(M−1) / (M + 1) × tan θ] (7)
From the above relationship, since the Bragg angle is different when the energy is different, it is impossible to make the X-rays having different energy the same magnification by asymmetric reflection of one crystal.
[0017]
Next, conditions for making the incident light and the outgoing light to the spectrometer coaxial are described. 4 (a) and 4 (b) show two-crystal monochromator model diagrams. The symbols in the figure are as follows.
[0018]
θ _B1 : Bragg angle of crystal 1, θ _B2 : Bragg angle of crystal 2, α: Asymmetric reflection angle of crystal 2, β _IN : Beam incident angle to crystal 2, β _OUT : Output angle from crystal 2 β _IN = θ _B2 −α (8)
β _OUT = θ _B2 + α (9)
For the outgoing beam to be always horizontal with respect to the incoming beam,
90 ° -2 × θ _B1 + β _IN + β _OUT = 90 ° That is, β _IN + β _OUT = 2θ _B1 (10)
Should just hold. Substituting equations (8) and (9) into equation (10),
θ _B1 = θ _B2 (11)
Therefore, even if the beam energy is different, the same crystal (with the same Bragg angle) is used, and if the angle and position of the two crystals are adjusted for each energy, the beam is always emitted coaxially.
[0019]
[Problems to be solved by the invention]
Even if the energy is different from the above, if the angle and position are adjusted using two crystals of the same type regardless of symmetry or asymmetry, the optical axis will always be constant and the light entering and exiting the two-crystal spectrometer will be parallel. It is impossible to equalize the beam size at the position with a two-crystal spectrometer using asymmetric reflection because the magnification changes as the energy changes from the relationship of equations (5) and (6).
[0020]
Therefore, in order to guide the beam to the irradiation position with the same optical axis and a predetermined size regardless of the energy, two sets of spectroscopes 21 and 22 suitable for each energy are prepared as shown in FIG. There is one configured to switch to either the spectroscope 21 or 22 that matches the energy to be selected.
[0021]
Specifically, the spectroscope 21 has different types of crystals 23 and 24, and the spectroscope 22 has different types of crystals 25 and 26, which are not shown. It is configured to be switched by a switching mechanism that performs a piston motion using an electric motor. The X-ray 1 having a wide range of energy from the accelerator 30, for example, white light, is magnified by the spectroscope 21 or 22, and the transmitted light transmitted through the subject 4 by irradiating the subject 4 with the magnified light 7. The image is detected by the detector 5 so that an image of the subject 4 can be taken.
[0022]
However, in the X-ray CT shown in FIG. 7, it is necessary to switch energy at high speed in order to solve problems such as shortening of examination time and movement of the subject 4 during imaging.
[0023]
Further, in order to obtain an image, it is necessary to increase the beam size to some extent. Therefore, since the crystal becomes large, there is a problem that a great acceleration is applied to the switching device and the device cannot be realized.
[0024]
Specifically, if the energy is switched at 25 Hz, the mirror size is 300 mm (size in the amplitude direction), and the half amplitude is 150 mm, an acceleration of 378 G is applied, and the X-ray energy switching mechanism cannot be realized.
[0025]
Therefore, the present invention can select X-rays of a plurality of monochromatic energies from X-rays having a wide range of energy at high speed, transmit X-rays with the same optical axis to the position of the subject even if the energy is different, and have the same size. An object of the present invention is to provide an X-ray CT apparatus for irradiating a subject with X-rays.
[0026]
[Means for Solving the Problems]
In order to achieve the above object, an invention corresponding to claim 1 includes: a first spectroscopic crystal that Bragg-reflects X-rays emitted from an accelerator and splits them into primary reflected light and n-order reflected light; A two-crystal spectroscope having a second spectroscopic crystal that expands in a state of being asymmetrically reflected and having an optical axis overlapping, by incident primary reflected light by Bragg reflection on the one spectral crystal and n-order reflected light;
It has a CdTe detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided, and the primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
Have
Provided is a diagnostic X-ray CT characterized in that X-ray electron density distribution is obtained by primary transmitted light and n-order transmitted light detected by this detection means .
[0027]
According to the invention corresponding to claim 1, X-rays having a wide range are incident on the two-crystal spectrometer, the primary light and the n-order light are selected on the same axis and reflected, and the reflected light is detected by the detector. CT light can be obtained by selecting primary light and n-order light.
[0028]
In order to achieve the above object, an invention corresponding to claim 2 includes a first spectral crystal that Bragg-reflects X-rays emitted from an accelerator and incident into a primary reflected light and an n-order reflected light, and the first spectral crystal. A two-crystal spectroscope having a second spectroscopic crystal that expands in a state of being asymmetrically reflected and having an optical axis overlapping, by incident primary reflected light by Bragg reflection on the one spectral crystal and n-order reflected light;
It has a CdTe detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided, and the primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
A diagnostic X-ray CT comprising:
A primary reflection light and an n-order reflection emitted from the two-crystal spectrometer are arranged between the two-crystal spectrometer and the subject, and have a filter formed by combining a part with and without a filter element. Provided is a diagnostic X-ray CT that selectively transmits one of light and obtains an electron density distribution of X-rays by primary transmitted light and n-order transmitted light detected by the detecting means .
[0029]
According to the invention corresponding to claim 2, X-rays having a wide range are incident on the two-crystal spectrometer, the first-order light and the n-order light are selected and reflected on the same axis, and the reflected light is selectively selected. By switching the filter to be blocked, a CT image can be obtained while selecting the primary light and the n-order light at high speed.
[0030]
In order to achieve the above object, an invention corresponding to claim 3 includes a first spectroscopic crystal that Bragg-reflects X-rays emitted from an accelerator and splits them into primary reflected light and n-order reflected light, A two-crystal spectroscope having a second spectroscopic crystal that expands in a state of being asymmetrically reflected and having an optical axis overlapping, by incident primary reflected light by Bragg reflection on the one spectral crystal and n-order reflected light;
It has a CdTe detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided, and the primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
A diagnostic X-ray CT comprising:
A filter that is disposed between the accelerator and the second crystal spectrometer and has a combination of a part with a filter element and a part without a filter element, and light having the same wavelength as the primary reflected light emitted from the second crystal spectrometer; One of the n-order reflected lights emitted from the two-crystal spectrometer is selectively transmitted, and an X-ray electron density distribution is obtained by the primary transmitted light and the n-order transmitted light detected by the detecting means. A diagnostic X-ray CT is provided.
[0031]
According to the invention corresponding to claim 3, by switching the filter that selectively blocks X-rays having a wide range, the first-order light and the n-th order light are selected at high speed, and this is incident on the two-crystal spectrometer. Then, the first order light and the nth order light are selected on the same axis and reflected, and a CT image can be obtained by irradiating the subject with the reflected light.
[0034]
In order to achieve the above object, an invention corresponding to claim 4 includes a first spectral crystal that Bragg-reflects X-rays emitted from an accelerator and splits them into primary reflected light and n-order reflected light, A two-crystal spectroscope having a second spectroscopic crystal that expands in a state of being asymmetrically reflected and having an optical axis overlapping, by incident primary reflected light by Bragg reflection on the one spectral crystal and n-order reflected light;
It has a semiconductor detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided. The primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
A diagnostic X-ray CT comprising:
The filter is disposed between the accelerator and the two-crystal spectrometer , and has two types of filter elements arranged adjacent to each other and is capable of alternately putting in and out the filter elements, and is emitted from the two-crystal spectrometer. The subject can be irradiated with light having different transmittance or absorption rate of light having the same wavelength as that of the primary reflected light and light having the same wavelength as that of the nth order reflected light emitted from the second crystal spectrometer. Provided is a diagnostic X-ray CT characterized in that an X-ray electron density distribution is obtained by primary transmitted light and n-order transmitted light detected by a detecting means .
[0035]
According to the invention corresponding to claim 4 , the subject is irradiated with light having different intensity ratios of the first-order light and the n-order light obtained by putting in and out a filter that enters a wide range of X-rays. CT images can be obtained.
[0036]
In order to achieve the above object, the invention corresponding to claim 5 is the diagnostic X-ray CT according to any one of claims 2 to 4 , further comprising a filter rotating device that performs rotation switching of the filter. is there.
[0037]
According to the invention corresponding to claim 5 , in claims 2 to 4 , the CT image can be obtained by switching the energy at high speed by rotating the filter.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0039]
<Embodiment 1 >
(Constitution)
In the present embodiment, as shown in FIG. 1, an X-ray 1 having a wide range of energy from an accelerator 30 is incident and split into primary reflected light and n-order reflected light 6 to irradiate the subject 4. It is those provided with a single spectrometer having a first crystal 2 and the second crystal 3. Then, a detector 5 composed of, for example CdT e detects the first order transmission light and n-order light transmitted through the subject 4 (Kad pneumo tellurium).
[0040]
In the present embodiment, the energy required for the first crystal 2 is selected, and the beam is expanded by the asymmetric reflection of the second crystal 3. It passes through the subject 4 and is detected by the detector 5.
[0041]
(Function, effect)
Next, operations and effects of the first embodiment configured as described above will be described. Necessary energy (radiated light), that is, primary light and n-order light 6 is selected by Bragg reflection of the first crystal 2 from the X-ray 1 emitted from the accelerator 30. The light reflected by the first crystal 2 is enlarged to a necessary size by the asymmetric reflection of the second crystal 3.
[0042]
Since the reflected light of the first crystal 2 and the second crystal 3 follows the formula (5), the primary light is the formula (1), and n = 1 and the n-order light are reflected. Since the Bragg angle and the asymmetric reflection angle are the same for both the primary light and the n-order light, the same size is enlarged in the asymmetric reflection. In the expressions (6) and (7), the optical axes of the primary light and the n-order light, that is, the expanded light 7 are overlapped, pass through the subject 4 and guided to the detector 5. The detector 5 classifies and detects the intensity based on the energy of the X-ray, and obtains a CT image. An electron density distribution is obtained by the equations (1), (2), and (3).
[0043]
According to the present embodiment, it is possible to select light having a plurality of necessary energy from the X-ray 1, expand it to a necessary beam size, irradiate the subject 4 with the same optical axis, and obtain an electron density distribution. .
[0044]
<Embodiment 2 (corresponding to claims 2 and 6)>
(Constitution)
As shown in FIG. 2, an X-ray 1 having a wide range of energy from an accelerator 30 is incident and split into primary reflected light and n-order reflected light. The first crystal 2 and the second crystal One spectroscope having 3 is provided.
[0045]
Further, one of the primary reflected light and the n-order reflected light emitted from the spectroscope is selectively transmitted to irradiate the subject, and a portion 14 having a single type of filter element, which will be described later, and a filter The filter 10 which combines the part 13 without an element is provided.
[0046]
In the portion 14 of the filter 10 having the filter element, a filter element having a transmittance different from that of the secondary light with respect to the primary light, for example, 33 keV is used for the primary light and iodine is used for the filter element.
[0047]
The filter 10 is rotatably connected to the rotating device 11. Moreover, the detector 5 which detects the primary transmitted light and the n-th transmitted light which permeate | transmit the subject 4 is provided.
[0048]
(Function, effect)
Next, operations and effects of the second embodiment configured as described above will be described. Necessary energy is selected from the X-rays 1 emitted from the accelerator 30 by Bragg reflection of the first crystal 2 (primary light and secondary light 6). The light reflected by the first crystal 2 is enlarged to a necessary size by the asymmetric reflection of the second crystal 3. Since the reflected light of the first crystal 2 and the second crystal 3 follows the equation (5), the primary light [n = 1 in the equation (5)] and the secondary light are reflected. Since both the primary light and the secondary light have the same Bragg angle and the asymmetric reflection angle, they are enlarged to the same size in the asymmetric reflection. The primary light of [Formula (2), Formula (3)] and the secondary light expansion light 7 overlap each other.
[0049]
The filter element portion 14 uses iodine having a high absorption rate for 33 keV and a low absorption rate for the second-order 66 keV. The transmitted light is a mixture of primary light and secondary light, but the intensity ratio can be greatly changed with respect to the non-filter portion 13. That is, in Formula (4), I ₁₁ : Intensity of the primary light (33 keV) of the primary light (33 keV) of the portion 13 without the filter element I ₁₂ : Intensity of the secondary light (66 keV) of the non-filter element 13 of the front surface of the subject I ₂₁ : Filter element There primary light portion 14 (33keV) subjects the front of the intensity _{I 22:} becomes subject front of the intensity of the secondary light (66keV) of the filter element there portion 14, unwinds the simultaneous equations, the transmittance _T 1, _{T 2} The electron density distribution can be obtained from the equations (1) and (2).
[0050]
<Embodiment 3 (corresponding to claims 4 and 6)>
(Constitution)
In the present embodiment, as shown in FIG. 3, an X-ray 1 having a wide range of energy from an accelerator 30 is incident and split into primary reflected light and n-order reflected light. And one spectrometer having the second crystal 3.
[0051]
In addition, the primary reflected light and the n-order reflected light emitted from the spectroscope are respectively incident, and light having different transmittances or absorptances of the primary reflected light and the n-order reflected light is detected by the subject 4. The filter 20 which consists of two types of filter elements 8 and 9 which irradiate is provided. The filter element 8 is made of a semicircular semi-transmissive material made of a material that blocks n-order light. The filter element 9 is made of a semicircular semi-transmissive material made of a material that transmits only the n-order light opposite to that of the filter element 8 and blocks the primary light.
[0052]
The filter 20 is connected to a rotating device 11 for rotationally driving the filter 20.
[0053]
Furthermore, a detector 5 for detecting primary transmitted light and n-order transmitted light transmitted through the subject 4 is provided.
[0054]
(Function, effect)
Next, operations and effects of the third embodiment configured as described above will be described. For the X-ray 1 emitted from the accelerator 30, necessary energy is selected by the Bragg reflection of the first crystal 2 (primary light and n-order light 6). The light reflected by the first crystal 2 is enlarged to a necessary size by the asymmetric reflection of the second crystal 3. Since the reflected light of the first crystal 2 and the second crystal 3 follows the equation (5), the primary light [n = 1 in the equation (5)] and the n-order light are reflected. Since the Bragg angle and the asymmetric reflection angle are the same for both the primary light and the n-order light, the same size is enlarged in the asymmetric reflection. [Expressions (2) and (3)] The primary light and the expanded light 7 of the n-order light overlap each other. The filter 20 includes a filter element 8 that transmits only primary light and blocks n-order light, and a filter element 9 that transmits only n-order light and blocks primary light. Rotating device 11 rotates at a constant speed according to the required energy switching, X-ray 1 of one energy out of the two energies necessary for imaging is alternately irradiated to subject 4 at regular intervals, and each energy is detected by detector 5. The X-ray intensity is measured.
[0055]
According to this embodiment, it is possible to select necessary two energy light from white light, expand it to a necessary beam size, and irradiate a subject with necessary X-ray energy at high speed alternately on the same optical axis. Since the required energy light is selected from the two energies simply by rotating 20, X-ray energy switching can be performed at high speed.
[0056]
<Embodiment 4 (corresponding to claims 3 and 6)>
As shown in FIG. 5, this embodiment is different from the embodiment of FIG. 2 in that the positions of the filter 10 and the spectrometer are reversed. Specifically, the filter 10 is arranged on the accelerator 30 side, and the filter The light transmitted through 10 is input to a spectroscope having crystals 2 and 3 so that the subject 4 is irradiated with reflected light obtained by the spectroscope. Other points are the same as in the embodiment of FIG. The operations and effects of this embodiment are the same as those of the second embodiment.
[0057]
<Embodiment 5 (corresponding to claims 5 and 6)>
As shown in FIG. 6, this embodiment is different from the embodiment of FIG. 3 in that the positions of the filter 20 and the spectrometer are reversed. Specifically, the filter 20 is arranged on the accelerator 30 side. The light transmitted through the filter 20 is input to the spectroscope having the crystals 2 and 3, and the subject 4 is irradiated with the reflected light obtained by the spectroscope. Other points are the same as in the embodiment of FIG. The operations and effects of this embodiment are the same as those of the third embodiment.
[0058]
【The invention's effect】
As described above in detail, according to the present invention, a plurality of energies necessary for CT imaging are selected from X-rays having a wide range of energy emitted from an accelerator, and a beam is emitted to the subject's position with the same optical axis and the same size. It is possible to provide a diagnostic X-ray CT that can be guided and can switch energy at high speed.
In addition, an error of several percent was unavoidable in the approximation from the conventional CT value, but with this method, since the electron density distribution can be obtained directly by selecting X-rays of two energies, the accuracy of treatment planning is improved. To do.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram for explaining Embodiment 1 of the present invention.
FIG. 2 is a schematic configuration diagram for explaining a second embodiment of the present invention.
FIG. 3 is a schematic configuration diagram for explaining a third embodiment of the present invention.
FIG. 4 is a diagram for explaining the principle of diagnostic X-ray CT of the present invention.
FIG. 5 is a schematic configuration diagram for explaining a fourth embodiment of the present invention.
FIG. 6 is a schematic configuration diagram for explaining a fifth embodiment of the present invention.
FIG. 7 is a schematic configuration diagram for explaining a problem of a conventional diagnostic X-ray CT.
[Explanation of symbols]
1 ... X-ray
2 ... 1st crystal
3 ... second crystal
4… Subject
5 ... Detector
6 ... Primary light and n-order light 7 ... Magnified light
8 ... Filter element
9 ... Filter elements 10, 20 ... Rotating filter 11 ... Rotating device 13 ... No filter part 14 ... Filtered part 30 ... Accelerator

Claims (5)

A first spectroscopic crystal that Bragg-reflects X-rays emitted from the accelerator and separates them into primary reflected light and n-order reflected light, and primary reflected light and n-order reflected by Bragg reflection on the first spectroscopic crystal. A two-crystal spectrometer having a second spectroscopic crystal that is asymmetrically reflected and expands in a state of overlapping optical axes;
It has a CdTe detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided, and the primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
Have
A diagnostic X-ray CT characterized in that an X-ray electron density distribution is obtained by primary transmitted light and n-order transmitted light detected by the detecting means . A first spectroscopic crystal that Bragg-reflects X-rays emitted from the accelerator and separates them into primary reflected light and n-order reflected light, and primary reflected light and n-order reflected by Bragg reflection on the first spectroscopic crystal. A two-crystal spectrometer having a second spectroscopic crystal that is asymmetrically reflected and expands in a state of overlapping optical axes;
It has a CdTe detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided, and the primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
A diagnostic X-ray CT comprising:
A primary reflection light and an n-order reflection emitted from the two-crystal spectrometer are arranged between the two-crystal spectrometer and the subject, and have a filter formed by combining a part with and without a filter element. A diagnostic X-ray CT that selectively transmits one of light and obtains an electron density distribution of X-rays by primary transmitted light and n-order transmitted light detected by the detecting means . A first spectral crystal that Bragg-reflects incident X-rays emitted from the accelerator and separates it into primary reflected light and n-order reflected light, and primary reflected light and n-order reflected by Bragg reflection on the first spectral crystal. A two-crystal spectrometer having a second spectroscopic crystal that is asymmetrically reflected and expands in a state of overlapping optical axes;
It has a CdTe detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided, and the primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
A diagnostic X-ray CT comprising:
A filter that is disposed between the accelerator and the second crystal spectrometer and has a combination of a part with a filter element and a part without a filter element, and light having the same wavelength as the primary reflected light emitted from the second crystal spectrometer; One of the n-order reflected lights emitted from the two-crystal spectrometer is selectively transmitted, and an X-ray electron density distribution is obtained by the primary transmitted light and the n-order transmitted light detected by the detecting means. X-ray CT for diagnosis to be fine. A first spectroscopic crystal that Bragg-reflects X-rays emitted from the accelerator and separates them into primary reflected light and n-order reflected light, and primary reflected light and n-order reflected by Bragg reflection on the first spectroscopic crystal. A two-crystal spectrometer having a second spectroscopic crystal that is asymmetrically reflected and expands in a state of overlapping optical axes;
It has a semiconductor detector and is arranged so that the expanded light from the second spectral crystal after passing through the subject is guided. The primary transmitted light and the nth transmitted light are separated by the energy of the X-rays after transmission. Separately detecting means for detecting intensity,
A diagnostic X-ray CT comprising:
The filter is disposed between the accelerator and the two-crystal spectrometer , and has two types of filter elements arranged adjacent to each other and is capable of alternately putting in and out the filter elements, and is emitted from the two-crystal spectrometer. The subject can be irradiated with light having different transmittance or absorption rate of light having the same wavelength as that of the primary reflected light and light having the same wavelength as that of the nth order reflected light emitted from the second crystal spectrometer. A diagnostic X-ray CT characterized in that X-ray electron density distribution is obtained by primary transmitted light and n-order transmitted light detected by a detecting means . The diagnostic X-ray CT according to any one of claims 2 to 4, further comprising a filter rotating device that performs rotation switching of the filter .

Images