JP2004028789A - Radiation shield, radiation detector, and radiodiagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shield excess radiation by X-ray generated from an X-ray generator. <P>SOLUTION: The radiation shield consists of iron 51, and tantalum which has larger atomic number than iron 51. Iron 51 and tantalum 52 are combined at suitable thicknesses so that the attenuation index (attenuation coefficient × thickness) becomes equal to or larger than the attenuation index of lead with a thickness at 3mm or less, which is provided at the back and side surfaces of the X-ray detector 70. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation shield for shielding excess radiation due to X-rays generated from an X-ray generator, a radiation detector including the radiation shield, and a radiation diagnostic apparatus including the radiation shield.
[0002]
[Prior art]
Conventionally, with respect to X-ray shielding in an apparatus for generating X-rays, for example, Japanese Patent Publication No. Hei 7-66080 (X-ray shielding that is used for an X-ray diaphragm that limits an irradiation field incident on an X-ray film is made thinner than before) Japanese Patent Application Laid-Open No. 63-61999 (X-ray shielding member for enhancing the effect of shielding X-rays incident on an X-ray detector) and the like are known.
[0003]
In the former, a reinforcing member such as a thin fiber reinforced plastic is attached to a shielding member such as lead, and a thin and strong shielding member is formed while keeping the shielding ability. In the latter, two kinds of members having different K absorption edges, such as lead and tantalum, are bonded together to produce a shielding material having an enhanced shielding effect by changing the quality of light incident on the X-ray detector. It is.
[0004]
On the other hand, in a diagnostic device using X-rays, the amount of surplus radiation emitted from the diagnostic device without using the X-rays emitted from the X-ray generator through a patient or an X-ray detector and the like is not used. Various standards and the like (for example, standards for medical X-ray equipment in Japan and IEC60601-1-3 for overseas) are within limits.
[0005]
Due to such a restriction, generally, the above-mentioned standard is satisfied by providing a radiation shield on the back surface of the X-ray detector and its periphery.
[0006]
Conventionally, lead having a thickness of about 2 mm to 3 mm has been used as a radiation shield. This is because the shielding ability against radiation is (1) the higher the atomic number, the higher the substance (lead (Pb) is atomic number 82), and (2) the atomic number is the same as that of lead in terms of availability and price. Because it is much better than other substances that have
[0007]
However, in recent years, from the viewpoint of consideration for the environment, it has been required to manufacture products that use as little lead as possible.
[0008]
[Problems to be solved by the invention]
As described above, since the conventional radiation shield is mainly made of lead, it is not preferable from the viewpoint of recent environmental problems, and has been against the current trend of eliminating lead in various directions. Also, in order to expect the same level of shielding effect as lead using a substance other than lead when lead is not used, it requires tens of times the thickness of lead, is brittle in terms of strength, A material that can be used practically, such as being very expensive due to a rare substance, could not be obtained.
[0009]
In particular, iron and other materials have the advantage of being readily available, inexpensive, and robust in terms of strength as general-purpose materials. There was a problem that had to be.
[0010]
Therefore, the present invention provides a radiation shield which can be practically used even when iron is used, for example, substantially without using lead, a radiation detector having the radiation shield, and radiation having the radiation shield. It is an object to provide a diagnostic device.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a radiation shield according to the present invention according to claim 1 includes a first component mainly composed of iron or a substance having an atomic number close to iron, and a first component composed of the first component. A second component mainly composed of a substance having an atomic number larger than that of the main substance and smaller than that of lead.
[0012]
Accordingly, when the radiation shield is formed using iron or a substance having a source number close to that of iron, a radiation shield that is thinner than that formed of iron alone can be realized.
[0013]
The radiation shield of the invention according to claim 4 includes a first constituent element made of one or more substances and one or more substances, and an attenuation coefficient of a main substance of the radiation shield is a main substance of the first constituent element. A second component in a non-solid state, which is larger than the attenuation coefficient of the first component, and disposing the first component so as to cover the second component with respect to the radiation shield. Features.
[0014]
Further, the radiation shield of the present invention according to claim 6 is a radiation shielding body according to claim 1, wherein the first constituent element is mainly a substance other than lead, and the main substance is a substance other than lead, and at least one of the strength and the attenuation coefficient is the second element. A second component that is higher than that of the main component of the first component, and the first component and the second component are each suitable for an attenuation index determined by an attenuation coefficient and a thickness of the material. It is characterized in that the attenuation index when combined with a small thickness is equal to or greater than the attenuation index of lead at a predetermined thickness.
[0015]
In the present invention according to claim 7, an X-ray detection unit for detecting X-rays transmitted through the subject, iron, or a first component mainly composed of a substance whose atomic number is close to iron, A radiation shield comprising: a second component having, as a main material, a substance having an atomic number larger than that of the main substance of the first element and a substance having an atomic number smaller than that of lead; The radiation detector is provided on a side different from the subject to be used for use.
[0016]
Further, in the present invention according to claim 8, an X-ray generation unit for generating X-rays, an X-ray detection unit for detecting X-rays generated by the X-ray generation unit and transmitted through the subject, and And a second component mainly composed of a substance having an atomic number larger than that of the first component and having a smaller atomic number than lead. The radiation diagnostic apparatus further comprises: a radiation shield comprising: a radiation shield provided on a side different from the subject with respect to the X-ray detection unit. And
[0017]
According to the present invention as described above, radiation can be shielded without using lead as a main substance. By combining a plurality of substances that can compensate for each other's disadvantages with each other's merits, a practical radiation shield and a radiation diagnostic apparatus including this radiation shield can be provided.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
Hereinafter, a first embodiment of a radiation shield according to the present invention will be described with reference to FIGS. First, an outline of the present invention will be described with reference to FIGS.
[0019]
FIG. 1 is a side view showing an example of a state at the time of examination using an X-ray diagnostic apparatus, and is a diagram for explaining a radiation diagnostic apparatus having a radiation shield of the present invention. In FIG. 1, an X-ray diagnostic apparatus includes an X-ray generator 1 for irradiating X-rays, a bed 3 on which a patient 2 sleeps, an X-ray detector 4 for detecting X-rays transmitted through the patient 2, and an X-ray detector. A radiation shield 6 that shields excess radiation 5 including X-rays that leaks from behind the detector 4 or the like.
[0020]
The X-rays generated by the X-ray generator 1 are applied to the patient 2 lying on the couch 3, transmitted through the patient 2 and the couch 3, and collected and detected by the X-ray detector 4. Information detected by the X-ray detector 4 is transmitted to a subsequent device (not shown) and processed as image information. The X-ray detector 4 generally includes an X-ray fluorescence intensifier, an X-ray flat detector (a flat solid detector), and the like. When the X-ray detector 4 is the X-ray film itself, image information is recorded on this film. A radiation shield 6 is installed for radiation containing X-rays (excess radiation 5) which is not collected by the X-ray detector 4 or leaked from the X-ray detector 4 among the X-rays transmitted through the patient 2. Thus, radiation to the outside of the X-ray diagnostic apparatus is suppressed.
[0021]
FIG. 2 is a view showing a state in which a radiation shield 9 is provided when the X-ray fluorescence multiplier 7 is used as the X-ray detector. In the figure, reference numeral 8 denotes a television camera, and 10 denotes an image output unit of the X-ray fluorescent multiplier 7. The table 3 may have a form in which a radiation shield 9 is attached to shield X-rays near the input. Further, a radiation shield 9 may be integrally formed (applied) around the X-ray fluorescent multiplier 7. Since the image output unit 10 is not provided with the radiation shield 9, the radiation shield 9 is provided for the television camera 8 to shield X-rays coming out of the image output unit 10.
[0022]
As is clear from the drawings in both cases of FIGS. 1 and 2, the radiation shield 6 (9) is used by the patient 2 with respect to the X-ray detector 4 (the X-ray fluorescence multiplier 7 in FIG. 2). It is provided on the side that is not located (the side opposite to the patient 2 and the side in the figure).
[0023]
In domestic and overseas standards, the amount of surplus radiation 5 leaking around the X-ray detector as described above is specified. However, the shielding ability of the radiation shield 6 provided to satisfy the specified value, that is, the radiation shield The shielding ability of the substance used as 6 is expressed by the following equation 1.
[0024]
I = I0 × EXP [−μx] (formula 1)
I0: Intensity of X-ray of single energy incident on the target substance
I: Intensity of monoenergetic X-ray transmitted through the target substance
x: Thickness of the target substance
μ: Attenuation coefficient of the target substance
Here, the attenuation coefficient μ indicates the degree of interaction with the substance,
1) Coefficient due to photoelectric effect
2) Rayleigh scattering coefficient
3) Coefficient by Compton scattering
4) Coefficient by electron pair generation
And is determined by the type of the substance and the energy of the X-ray.
[0025]
For example, FIG. 3 is a diagram showing attenuation coefficient characteristics of lead conventionally used as a radiation shield. In the figure, the vertical axis indicates the attenuation coefficient (/ cm), and the horizontal axis indicates the X-ray energy (keV). In FIG. 3, the discontinuity point near 88.0 keV is called a K absorption edge and corresponds to an excitation voltage of a K characteristic X-ray.
[0026]
In the case of lead, the radiation shield has been realized with a thickness of about 2 mm to 3 mm in order to satisfy the specified value defined by the standard. In order to form a radiation shielding body having a radiation shielding ability equal to or higher than that of lead by using a main substance other than lead in the present invention, the index “μ × x” (hereinafter referred to as the attenuation index) of the above formula 1 is used. What is necessary is to make a combination of substances equivalent to or more than lead. For example, in order to realize a radiation shield instead of lead by using two substances (main substances) A and B, the following equation 2 may be satisfied.
[0027]
μ (Pb) × x (Pb) ≦ μ (A) × x (A) + μ (B) × x (B) (2)
μ (Pb): Lead attenuation coefficient
μ (A): attenuation coefficient of substance A
μ (B): attenuation coefficient of substance B
x (Pb): thickness of lead
x (A): thickness of substance A
x (B): thickness of substance B
FIG. 4 is an attenuation index characteristic diagram for theoretically showing an example in which the attenuation index due to the combination of the substance A and the substance B exceeds the attenuation index of lead. In the figure, the vertical axis represents the attenuation index (attenuation coefficient (/ cm) × the thickness (cm)), and the horizontal axis represents the X-ray energy (keV).
[0028]
In FIG. 4, a solid line 41 is an attenuation index characteristic of 1 mm thick lead (x (Pb) = 0.1 (cm) in Equation 2), and a thin solid line 42 is a substance A having a thickness of 2 mm (x (Ab in Equation 2). ) = 0.2 (cm)), the thin solid line 43 is the attenuation index characteristic of a 3 mm thick substance B (x (B) = 0.3 (cm) in Equation 2), and the thick solid line 44 is the total. 5 shows attenuation index characteristics of a combination of substances A and B having a thickness of 5 mm, respectively. As can be seen from the figure, even when each substance alone cannot exceed the lead attenuation index in the entire X-ray energy band, the radiation shielding ability of the combination of multiple substances is equal to or higher than that of the case of using lead. Can be obtained.
[0029]
Next, the first embodiment of the present invention will be described in detail with reference to FIGS.
[0030]
As a first embodiment of the present invention, a radiation shield when a “general-purpose substance having a small atomic number” and a “rare substance having a large atomic number” are combined will be described.
[0031]
First, iron (Fe: atomic number 26) can be considered as a “general-purpose substance having a small atomic number” used for a radiation shield. Such a substance can be said to be a general-purpose substance in terms of availability and economy, but has a low radiation shielding ability by itself. For example, in order to obtain a radiation shielding ability equivalent to that of lead having a thickness of 1 mm, a thickness of about 22 mm is required in the case of iron. For this reason, if a radiation shield is composed of such a substance alone, a very thick radiation shield will be seated around the X-ray detector, and the mobility of the X-ray diagnostic apparatus will be lost. In particular, in the case of a surgical X-ray apparatus or an arm-type apparatus, the area around the X-ray detector becomes too large, the mobility is impaired, and it cannot be put to practical use.
[0032]
Further, tantalum (Ta: atomic number 73) and tungsten (W: atomic number 74) can be considered as the "rare substance having a large atomic number" used for the radiation shield. Since these substances are relatively close to the atomic number of lead, their radiation shielding ability is not so different from that of lead, but they are very expensive as rare substances. Therefore, there is no problem in using it as a relatively thin and small-area portion that is installed near the X-ray generator and shields X-rays incident on the X-ray detector. The radiation shield is very expensive for use in a relatively thick and large area such as to shield the excess radiation.
[0033]
Thus, by combining these “general-purpose substances having a small atomic number” and “rare substances having a large atomic number”, a radiation shield that compensates for their respective disadvantages is realized.
[0034]
FIG. 5 is a sectional view showing the structure of the radiation shield according to the first embodiment of the present invention. In FIG. 5, the radiation shield comprises iron 51 and tantalum 52. Although FIG. 5 shows a configuration in which each substance alternately forms a layer, a two-layer structure of iron and tantalum may be used (see FIG. 6). Since both iron and tantalum are robust, iron having a lower attenuation coefficient than tantalum may be provided on the side closer to the X-ray detector (see FIG. 7). 7, the iron 51 is provided so as to be close to the X-ray detector 70. As a result, it is possible to prevent surplus radiation from being suddenly shielded by tantalum having a high attenuation coefficient and increase the amount of radiation rebounding to the X-ray detector, thereby preventing the detection accuracy from being lowered by the X-ray detector. However, since the shielding ability is actually based on the attenuation index (attenuation coefficient × thickness), iron may have a higher shielding ability depending on the selection of the material thickness. In that case, the arrangement opposite to the above is preferable. Note that the thickness of the substance largely depends on the price at the time of obtaining the substance. Therefore, the thickness of relatively inexpensive iron and rare and expensive tantalum is determined based on a combination of ranges shown in FIG. You only have to decide.
[0035]
FIG. 8 is an attenuation index characteristic diagram for illustrating an example of the attenuation index characteristic of the radiation shield according to the first embodiment of the present invention. In the figure, the vertical axis represents the attenuation index (attenuation coefficient (/ cm) × the thickness (cm)), and the horizontal axis represents the X-ray energy (keV).
[0036]
In FIG. 8, a thin solid line 81 indicates an attenuation index characteristic of lead having a thickness of 1 mm, and a thick solid line 82 indicates an attenuation index characteristic when iron having a thickness of 8.65 mm and tantalum having a thickness of 0.46 mm are combined. ing. In this case, since the attenuation index characteristic of lead is equal to or higher than that of lead in the entire X-ray energy region, regardless of the magnitude of the X-ray energy, the radiation shield has at least the shielding ability when lead is used. The thicknesses of iron and tantalum described above are for 1 mm thick lead. For example, in order to obtain a shielding ability (attenuation index) equivalent to that of Amm thick lead, each thickness was multiplied by A. It can be realized by combining things.
[0037]
In FIG. 8, as an example of the combination of iron and tantalum with respect to the thickness of 1 mm of lead, the case where iron is 8.65 mm and tantalum is 0.46 mm has been described. It is not limited. FIG. 9 is a diagram showing combinations of iron and tantalum thicknesses that can obtain an attenuation index equivalent to that of a lead thickness of 1 mm. In the figure, the vertical axis indicates the thickness (mm) of iron, and the horizontal axis indicates the thickness (mm) of tantalum.
[0038]
In any case within the range shown in FIG. 9, the attenuation index in the case of combining two substances can be made equal to the attenuation index of a thickness of 1 mm of lead. However, when the thickness of tantalum is about 0.70 mm to 0.75 mm or more, the reduction rate of the iron thickness becomes small. Therefore, a combination in which the thickness of iron is selected when the thickness of tantalum is smaller than 0.70 mm to 0.75 mm is preferable. In this case, the relationship between the thicknesses of iron and tantalum is expressed by the following equation (3).
[0039]
(Thickness of iron) = − 29 × (thickness of tantalum) +22 (Equation 3)
As is clear from FIG. 9, the thickness of the radiation shield when combining iron and tantalum largely depends on the thickness of iron. Therefore, when the radiation thickness is taken into consideration even when the above equation 3 is satisfied, the thickness required when the radiation shield is constituted by iron alone (when the tantalum thickness = 0 in the above equation 3) It is preferable to use iron with a thickness of about ／ or less of (iron thickness = 22 mm).
[0040]
In addition, since the above formula 3 is a relationship between iron and tantalum with respect to a thickness of 1 mm of lead, in order to obtain a radiation shield having an attenuation index equivalent to the thickness of lead Amm, the iron and the tantalum obtained by the above formula 3 must be used. A thickness obtained by multiplying the thickness of tantalum by A may be used.
[0041]
The case where iron and tantalum are combined has been described above. However, in the first embodiment of the present invention in which “a general-purpose substance having a small atomic number” and “a rare substance having a large atomic number” are combined, the combination is limited to the combination of iron and tantalum. It is not done. Hereinafter, description will be made with reference to FIGS.
[0042]
First, a case where an iron alloy is used instead of iron will be described. Iron alloys include, for example, cast iron, steel, and stainless steel. In the case of cast iron and steel, components other than iron contained therein are minute, so that the influence on the relationship of the above equation 3 is small. Therefore, simply by multiplying the iron thickness in the above equation 3 by a coefficient, a combination with tantalum can be obtained without finding the relationship as shown in FIG. 9 again. In the case of stainless steel, nickel (Ni: atomic number 28) or chromium (Cr: atomic number 24) whose atomic number is close to that of iron is included in iron, which will be described below with reference to FIG.
[0043]
FIG. 10 is a diagram showing an example of the attenuation coefficient characteristic of a substance relating to stainless steel. In the figure, the vertical axis indicates the attenuation coefficient (/ cm), and the horizontal axis indicates the X-ray energy (keV). In the figure, a thick solid line 101 indicates an attenuation coefficient characteristic of iron, a thin solid line 102 indicates an attenuation coefficient characteristic of nickel, and a thin solid line 103 indicates an attenuation coefficient characteristic of chromium. As is clear from the figure, the attenuation coefficient characteristics of nickel and chromium are close to those of iron. Therefore, similarly to the case of cast iron and steel, simply by multiplying the iron thickness of the above equation 3 by a coefficient, a combination with tantalum can be obtained without obtaining the relationship shown in FIG. 9 again. .
[0044]
As described above, when an iron alloy is used instead of iron, depending on the content of a mixed substance such as nickel and chromium with respect to iron, the thickness of the iron of the above formula 3 is about 0.8 to 1.2. The thickness may be multiplied by the correction coefficient.
[0045]
Next, a case will be described where instead of iron, another substance having an atomic number close to that of iron is used instead of iron. Here, titanium (Ti: atomic number 22), chromium (Cr: atomic number 24), manganese (Mn: atomic number 25), cobalt (Co: atomic number 27), nickel (Ni : Atomic number 28), copper (Cu: atomic number 29), and zinc (Zn: atomic number 30). FIG. 11 is a diagram illustrating an example of the attenuation coefficient characteristic of each substance having an atomic number close to that of iron. In the figure, the vertical axis indicates the attenuation coefficient (/ cm), and the horizontal axis indicates the X-ray energy (keV).
[0046]
In the figure, a solid line 111 is an attenuation coefficient characteristic of titanium, a solid line 112 is an attenuation coefficient characteristic of chromium, a solid line 113 is an attenuation coefficient characteristic of manganese, a solid line 114 is an attenuation coefficient characteristic of iron, a solid line 115 is an attenuation coefficient characteristic of cobalt, and a solid line. Reference numeral 116 indicates the attenuation coefficient characteristic of nickel, solid line 117 indicates the attenuation coefficient characteristic of copper, and solid line 118 indicates the attenuation coefficient characteristic of zinc. As is clear from the figure, the attenuation coefficient characteristics of these substances are close to those of iron. Therefore, simply by multiplying the iron thickness in the above equation 3 by a coefficient, a combination with tantalum can be obtained without finding the relationship as shown in FIG. 9 again.
[0047]
For example, in the case of a substance having a smaller atomic number than iron (titanium, chromium, manganese, etc.), a correction coefficient for correcting the difference in attenuation coefficient with respect to the iron thickness obtained by the above equation 3 according to the substance. In the case of a substance having a larger atomic number than iron (cobalt, nickel, copper, zinc, and the like), the attenuation coefficient is set to about 0 to 3.0 with respect to the thickness of iron obtained by the above equation 3 according to the substance. The thickness may be multiplied by a correction coefficient of about 0.7 to 1.0 for correcting the difference.
[0048]
In the case where each of the above substances instead of iron contains impurities or is an alloy containing each as a main substance, it is multiplied by the above-mentioned correction coefficient and further added with a change in its characteristics by 0.8. The thickness may be multiplied by a correction coefficient of about 1.2.
[0049]
As described above, the substance replacing iron has been described.However, in view of the gist of the present invention, tantalum is also a substance only as an example, and the constituents of the radiation shield of the present invention are not limited to this substance. Absent. For example, instead of tantalum, an alloy of tantalum and another substance, tantalum containing impurities, or tungsten having an atomic number close to that of tantalum may be used.
[0050]
In the case where tantalum is an alloy with another substance or contains impurities, a correction coefficient of about 0.8 to 1.2 is added to the thickness of tantalum obtained by the above equation 3 in consideration of the properties of the mixture. The thickness may be multiplied.
[0051]
Further, the case of tungsten (W) will be described as an example of using another substance having an atomic number close to that of tantalum instead of tantalum. FIG. 12 is a diagram showing attenuation coefficient characteristics of tantalum and tungsten. In the figure, the vertical axis indicates the attenuation coefficient (/ cm), and the horizontal axis indicates the X-ray energy (keV).
[0052]
In the figure, a thin solid line 121 indicates an attenuation coefficient characteristic of tantalum, and a thick solid line 122 indicates an attenuation coefficient characteristic of tungsten. As is clear from the figure, the attenuation coefficient characteristics of these two substances are close to each other. Therefore, simply by multiplying the tantalum thickness in the above equation 3 by a coefficient, a combination with iron can be obtained without obtaining the relationship shown in FIG. 9 again.
[0053]
Actually, since the attenuation coefficient characteristic of tungsten is slightly better than that of tantalum, the thickness obtained by multiplying the thickness of tantalum obtained by the above equation 3 by a correction coefficient of about 0.85 for correcting the difference in attenuation coefficient is obtained. Just do it.
[0054]
When tungsten is an alloy with other substances or contains impurities, the above correction coefficient is multiplied, and further, a correction of about 0.8 to 1.2 is added in consideration of a change in the characteristic. The thickness may be multiplied by a coefficient.
[0055]
As described above, according to the first embodiment of the present invention, the “general-purpose substance having a small atomic number” is combined with the “general substance having a small atomic number” to form a “general-purpose substance having a small atomic number”. The low radiation shielding ability in the case of `` only rare substance with a large atomic number '' is supplemented by the `` radical substance with a large atomic number. '' Can be supplemented by That is, even if a radiation shielding body having a radiation shielding ability equal to or greater than that of the conventional lead is made of iron, the radiation shielding body is relatively thin and can be realized at a reasonable acquisition price.
(Second embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to FIGS.
[0056]
As a second embodiment of the present invention, a radiation shield in the case of combining “a robust substance (a general-purpose substance having a small atomic number)” and “a fragile substance having a large attenuation coefficient” will be described.
[0057]
First, as a “robust substance (a general-purpose substance having a small atomic number)” used for the radiation shield, for example, iron or the like described in the above-described first embodiment of the present invention can be considered. Such a substance is excellent in strength and can be said to be a robust substance, but has a low radiation shielding ability by itself. As described above, when a radiation shield is constituted by such a substance alone, a very thick radiation shield is seated around the X-ray detector, and the mobility of the X-ray diagnostic apparatus is lost. .
[0058]
Examples of the “fragile substance having a large attenuation coefficient” used for the radiation shield include, for example, barium (Ba: atomic number 56) and iodine, which have high radiation absorption and are also used as an X-ray contrast agent. (I: atomic number 53). These substances have a high attenuation coefficient due to a large attenuation coefficient, but on the other hand, they are insufficient in strength as a radiation shield as a constituent material of an X-ray diagnostic apparatus. In other words, these substances are often used in a non-solid state such as a powder or a liquid, and a single substance cannot be used to form a shield utilizing its radiation shielding ability.
[0059]
Thus, by combining these “robust substances (general-purpose substances having a small atomic number)” and “fragile substances having a large attenuation coefficient”, a radiation shield that compensates for their respective disadvantages is realized.
[0060]
FIG. 13 is a sectional view showing the structure of the radiation shield according to the second embodiment of the present invention. In FIG. 13, the radiation shield comprises iron 131 and barium 132. Although FIG. 14 shows a configuration in which each substance is alternately formed in layers, and the robust iron 131 sandwiches the fragile barium 132, a two-layer structure of iron and barium may be used (see FIG. 14).
[0061]
In the case of iron and barium, since the strength of iron is higher than that of barium, barium is sandwiched by iron as shown in FIG. 13 (three layers of iron-barium-iron (see FIG. 15)) or X-ray detection. It is preferable to take a two-layer structure in which barium is arranged on the vessel side and high-strength iron is arranged outside in consideration of strength (see FIG. 16).
[0062]
In FIG. 16, iron 131 is provided to cover barium 132 with respect to X-ray detector 160. Such an arrangement is particularly effective when barium is used in a non-solid state (powder or liquid form). If both materials to be combined are in a solid state, they may be warped during lamination and may be difficult to be integrally formed. However, in the case where one of the substances is non-solid, it is possible to easily form (integrally arrange) without worrying about warping by covering the non-solid substance with a solid substance.
[0063]
By the way, from the viewpoint of the radiation shielding capability, there is a method of providing iron having a lower attenuation coefficient than barium on the side closer to the X-ray detector as in the first embodiment (see FIG. 17). In this case, in order to support barium, which is a fragile substance, it is necessary to provide a container (such as a resin) outside the barium 132. As a result, surplus radiation (X-rays transmitted through the X-ray detector 160) is immediately blocked by barium having a high attenuation coefficient, and the amount of radiation that bounces back to the X-ray detector is increased to improve the detection accuracy of the X-ray detector. It is possible to avoid lowering. However, since the shielding ability actually depends on the attenuation index, iron may have a higher shielding ability depending on the selection of the material thickness. In that case, the arrangement opposite to the above is preferable. From the practical point of view, there is a problem in strength as described above. Therefore, in the case of the present embodiment, it is preferable to arrange a fragile substance near the X-ray detector.
[0064]
FIG. 18 is an attenuation index characteristic diagram illustrating an example of an attenuation index characteristic of the radiation shield according to the second embodiment of the present invention. In the figure, the vertical axis represents the attenuation index (attenuation coefficient (/ cm) × the thickness (cm)), and the horizontal axis represents the X-ray energy (keV).
[0065]
In FIG. 18, a thin solid line 181 indicates an attenuation index characteristic of lead having a thickness of 1 mm, and a thick solid line 182 indicates an attenuation index characteristic when iron having a thickness of 5.95 mm and barium having a thickness of 5.95 mm are combined. ing. In this case, since the attenuation index characteristic of lead is equal to or higher than that of lead in the entire X-ray energy region, regardless of the magnitude of the X-ray energy, the radiation shield has at least the shielding ability when lead is used. The thicknesses of iron and barium described above are based on lead having a thickness of 1 mm. For example, in order to obtain a shielding ability (attenuation index) equivalent to that of lead having a thickness of B mm, each thickness was multiplied by B. It can be realized by combining things.
[0066]
In FIG. 18, as an example of a method of combining iron and barium with respect to a thickness of 1 mm of lead, a case where iron is 5.95 mm and barium is 5.95 mm has been described. It is not limited. FIG. 19 is a diagram showing combinations of iron and barium thicknesses that can obtain an attenuation index equivalent to that of a lead thickness of 1 mm. In the figure, the vertical axis indicates the thickness of iron (mm), and the horizontal axis indicates the thickness of barium (mm).
[0067]
In any case within the range shown in FIG. 19, the attenuation index when two substances are combined can be made equal to the attenuation index for a thickness of 1 mm of lead. However, when the thickness of barium is about 7.5 mm or more, the rate of decrease in iron thickness decreases. Therefore, a combination in which the thickness of iron is selected when the thickness of barium is smaller than 7.5 mm is preferable. In this case, the relationship between the respective thicknesses of iron and barium is expressed by the following equation 4.
[0068]
(Thickness of iron) = − 2.8 × (thickness of barium) +22 (Equation 4)
As is clear from FIG. 19, the thickness of the radiation shield when iron and barium are combined has a relatively large portion depending on the thickness of iron. Therefore, when the radiation thickness is taken into consideration even when Equation 4 is satisfied, the thickness required when the radiation shield is constituted by iron alone (when Barium thickness = 0 in Equation 4 above) It is preferable to use iron with a thickness of about ／ or less of (iron thickness = 22 mm).
[0069]
In addition, since the above formula 4 is a relationship between iron and barium with respect to the thickness of 1 mm of lead, in order to obtain a radiation shield having an attenuation index equivalent to the thickness of lead Bmm, the iron and the barium obtained by the above formula 4 must be used. A thickness obtained by multiplying the thickness of barium by B times may be used.
[0070]
The case where iron and barium are combined has been described above. However, in the second embodiment of the present invention in which a “robust substance (a general-purpose substance having a small atomic number)” and a “fragile substance having a large attenuation coefficient” are combined, It is not limited to the combination of and barium.
[0071]
In the case where barium is mixed with other substances or contains impurities, a correction coefficient of about 0.8 to 1.2 is added to the thickness of barium obtained by the above equation 4 in consideration of the properties of the mixture and the like. Multiplied by the thickness.
[0072]
Further, the case of iodine (I) will be described as an example in which barium is replaced by another substance having an atomic number close to barium. FIG. 20 is a diagram showing attenuation coefficient characteristics of barium and iodine. In the figure, the vertical axis indicates the attenuation coefficient (/ cm), and the horizontal axis indicates the X-ray energy (keV).
[0073]
In the figure, a thin solid line 201 shows an attenuation coefficient characteristic of barium, and a thick solid line 202 shows an attenuation coefficient characteristic of iodine. As is clear from the figure, the attenuation coefficient characteristics of these two substances are close to each other. Therefore, simply by multiplying the barium thickness in the above formula 4 by a coefficient, a combination with iron can be obtained without obtaining the relationship shown in FIG. 19 again.
[0074]
Actually, since the attenuation coefficient characteristic of iodine is slightly better than that of barium, the thickness obtained by multiplying the thickness of barium obtained by the above equation 4 by a correction coefficient of about 0.8 to correct the difference between the attenuation coefficients. Just do it.
[0075]
When iodine is mixed with other substances or contains impurities, after multiplying the above correction coefficient, a correction coefficient of about 0.8 to 1.2 is further added in consideration of a change in the characteristic. The thickness may be multiplied.
[0076]
By the way, the iron according to the second embodiment is titanium, chromium, manganese, and others as described in the first embodiment. Equation 3 in the case of the first embodiment may be replaced with equation 4 in the case of the second embodiment, and a description thereof will be omitted.
[0077]
Note that when tin (Sn: atomic number 50) and a tin alloy having the same attenuation coefficient in an X-ray energy region of 33 KeV or more in the K absorption edge of iodine are used, a shielding effect equivalent to that of iodine and a compound of iodine can be obtained.
[0078]
As described above, according to the second embodiment of the present invention, by combining a “robust substance (a general-purpose substance having a small atomic number)” and a “fragile substance having a large attenuation coefficient”, a “robust substance” is obtained. Low radiation shielding ability in the case of only "a weak substance (a general-purpose substance with a small atomic number)" is compensated by "a fragile substance with a large attenuation coefficient", and the strength is inferior in the case of only a "fragile substance with a large attenuation coefficient" The points can be supplemented by “robust substances (general-purpose substances with small atomic numbers)”. That is, even if the radiation shielding body having the radiation shielding ability equal to or higher than that of the conventional lead is made of iron, the radiation shielding body is relatively thin and can be realized with sufficient strength.
(Third embodiment)
Lastly, a third embodiment of the present invention will be described in detail with reference to FIGS.
[0079]
As a third embodiment of the present invention, a radiation shield in the case of combining a “robust substance (a rare substance having a large atomic number)” and a “fragile substance having a large attenuation coefficient” will be described.
[0080]
First, as a “robust substance (a rare substance having a large atomic number)” used for the radiation shield, for example, tantalum or tungsten described in the above-described first embodiment of the present invention can be considered. These substances are described in the above-described first embodiment of the present invention, in that "the radiation shielding ability is not so different from lead because it is relatively close to the atomic number of lead". Although it can be said that it is a rare substance, it is very expensive as a rare substance. Therefore, there is no problem in using it as a relatively thin and small-area portion that is installed near the X-ray generator and shields X-rays incident on the X-ray detector. The radiation shield is very expensive for use in a relatively thick and large area such as to shield the excess radiation.
[0081]
Further, as the “fragile substance having a large attenuation coefficient” used for the radiation shield, for example, as described in the above-described second embodiment of the present invention, for example, the radiation absorption is high and the X-ray contrast is high. Barium, iodine, and the like, which are also used as agents, can be considered. These substances have a high attenuation coefficient due to a large attenuation coefficient, but on the other hand, they are insufficient in strength as a radiation shield as a constituent material of an X-ray diagnostic apparatus. In other words, these substances are often used in a non-solid state such as a powder or a liquid, and a single substance cannot be used to form a shield utilizing its radiation shielding ability.
[0082]
Thus, by combining these “robust substances (rare substances having a large atomic number)” and “fragile substances having a large attenuation coefficient”, a radiation shield that compensates for their respective disadvantages is realized.
[0083]
FIG. 21 is a sectional view showing the structure of the radiation shield according to the third embodiment of the present invention. In FIG. 21, the radiation shield comprises a tantalum 211 and a barium 212. Although FIG. 22 shows a structure in which each substance is alternately formed in layers and robust tantalum sandwiches fragile barium, a two-layer structure of tantalum and barium may be used (see FIG. 22).
[0084]
In the case of tantalum and barium, since tantalum has higher strength than barium, barium is sandwiched by tantalum as shown in FIG. 21 (three layers of iron-barium-iron may be used (see FIG. 23)) or X-ray detection It is preferable to have a two-layer structure in which barium is arranged on the vessel side and high strength tantalum is arranged on the outside in view of strength (see FIG. 24).
[0085]
In FIG. 24, the tantalum 211 is provided so as to cover the barium 212 with respect to the X-ray detector 240. Such an arrangement is particularly effective when barium is used in a non-solid state (powder or liquid form). If both materials to be combined are in a solid state, they may be warped during lamination and may be difficult to be integrally formed. However, in the case where one of the substances is non-solid, it is possible to easily form (integrally arrange) without worrying about warping by covering the non-solid substance with a solid substance.
[0086]
It is also preferable that barium having an attenuation coefficient slightly lower than that of tantalum is provided on the side closer to the X-ray detector from the viewpoint of radiation shielding ability. By doing so, it is possible to prevent the surplus radiation from being suddenly shielded by tantalum having a higher attenuation coefficient, and to prevent the amount of radiation that bounces back to the X-ray detector from increasing, thereby lowering the detection accuracy of the X-ray detector. It is possible.
[0087]
FIG. 25 is an attenuation index characteristic diagram illustrating an example of an attenuation index characteristic of the radiation shield according to the third embodiment of the present invention. In the figure, the vertical axis represents the attenuation index (attenuation coefficient (/ cm) × the thickness (cm)), and the horizontal axis represents the X-ray energy (keV).
[0088]
In FIG. 25, a thin solid line 251 indicates an attenuation index characteristic of lead having a thickness of 1 mm, and a thick solid line 252 indicates an attenuation index characteristic when tantalum having a thickness of 0.52 mm and barium having a thickness of 4.68 mm are combined. ing. In this case, since the attenuation index characteristic of lead is equal to or higher than that of lead in the entire X-ray energy region, regardless of the magnitude of the X-ray energy, the radiation shield has at least the shielding ability when lead is used. Note that the thicknesses of tantalum and barium described above are for lead having a thickness of 1 mm. For example, in order to obtain a shielding ability (attenuation index) equivalent to that of lead having a thickness of C mm, each thickness was multiplied by C. It can be realized by combining things.
[0089]
In FIG. 25, as an example of a method of combining tantalum and barium with respect to a thickness of 1 mm of lead, a case where tantalum is 0.52 mm and barium is 4.68 mm has been described. It is not limited. FIG. 26 is a diagram showing a combination of each thickness of tantalum and barium that can obtain an attenuation index equivalent to that of the case where the thickness of lead is 1 mm. In the figure, the vertical axis indicates the thickness (mm) of tantalum, and the horizontal axis indicates the thickness (mm) of barium.
[0090]
In any case within the range shown in FIG. 26, the attenuation index when two substances are combined can be made equal to the attenuation index for a thickness of 1 mm of lead. The relationship between the thicknesses of tantalum and barium is expressed by the following equation (5).
[0091]
(Thickness of tantalum) = − 0.097 × (thickness of barium) +0.97 (Equation 5)
As is clear from FIG. 26, the thickness of the radiation shield in the case of combining tantalum and barium greatly depends on the thickness of barium. Therefore, when the radiation thickness is taken into consideration even when the above equation 5 is satisfied, the thickness required when the radiation shield is constituted by barium alone (when the tantalum thickness = 0 in the above equation 5) It is preferable to use barium with a thickness of about ／ or less of the thickness of barium = 10 mm).
[0092]
In addition, since the above formula 5 is a relationship between tantalum and barium for a thickness of 1 mm of lead, in order to obtain a radiation shield having an attenuation index equivalent to the thickness of lead Cmm, tantalum obtained by the above formula 5 and A thickness obtained by multiplying the thickness of barium by C may be used.
[0093]
The case where tantalum and barium are combined has been described above. However, in the third embodiment of the present invention in which a “robust substance (a rare substance having a large atomic number)” and a “fragile substance having a large attenuation coefficient” are combined, tantalum is used. It is not limited to the combination of and barium.
[0094]
As described in the first embodiment, for example, tungsten or the like may be used as a substitute for the tantalum according to the present embodiment. Note that Equation 3 in the first embodiment may be replaced with Equation 5 in the third embodiment, and a description thereof will not be repeated.
[0095]
Further, as for barium in this embodiment, for example, iodine may be used as a substitute substance as described in the second embodiment. Note that Equation 4 in the second embodiment may be replaced with Equation 5 in the third embodiment, and a description thereof will not be repeated.
[0096]
Furthermore, when tin (Sn: atomic number 50) and a tin alloy having the same attenuation coefficient in the X-ray energy region of the K absorption edge of 33 KeV or more of iodine are used, a shielding effect equivalent to that of iodine and a compound of iodine can be obtained.
[0097]
As can be seen from FIG. 25, the combination of tantalum and barium can form a discontinuous point at the K absorption edge around 40 keV and 70 keV in X-ray energy. Lines are observed. However, when a substance having an atomic number of 30 or less existing in a region having a K absorption point lower than these two discontinuous points and near 10 keV or lower is further used, this effect is reduced.
[0098]
As described above, according to the third embodiment of the present invention, by combining a “robust substance (a rare substance having a large atomic number)” and a “fragile substance having a large attenuation coefficient”, a “robust substance” is obtained. The point that the acquisition price in the case of only a rare substance (large atomic number) is expensive is supplemented by the “fragile substance with a large attenuation coefficient”, and the strength in the case of only the “fragile substance with a large attenuation coefficient” is increased. Inferior points can be compensated for by “robust substances (rare substances with high atomic numbers)”. That is, there is an effect that a radiation shield having radiation shielding ability equal to or higher than that of the conventional lead can be realized at a reasonable acquisition price and with sufficient strength.
[0099]
As described above, according to the present invention, it is possible to constitute a radiation shield having a shielding ability equal to or greater than that of lead without using lead conventionally used for the radiation shield as a main substance of the shield. It becomes possible. By combining substances (components) having different attenuation coefficients and strengths, and furthermore, difficulty in obtaining (price), for example, a substance having a high shielding ability but inferior strength can be combined with a substance having a low shielding ability but excellent strength. Thus, a practical radiation shield can be provided without using lead substantially.
[0100]
Note that the present invention is not limited to the above-described embodiments of the present invention. The radiation shield described in each embodiment of the invention is not limited to being applicable only to an X-ray diagnostic apparatus, but is applicable to any radiation diagnostic apparatus that generates and diagnoses X-rays, such as an X-ray CT apparatus. . In the embodiment of the present invention, as a substance to be combined with iron (or a substance having an atomic number close to iron), tantalum or a substance having an atomic number close to tantalum (the first embodiment) and barium and barium are used. Although the substance having the close atomic number (the second embodiment) has been described, the present invention is not limited to these combinations, and the atomic number is larger than that of iron (or the substance whose atomic number is close to iron). Any substance having an atomic number smaller than that of lead may be used. Furthermore, in each of the embodiments of the present invention, two types of substances have been described as the main substances. However, in the present invention, a radiation shield may be composed of three or more types of plural substances.
[0101]
Furthermore, it goes without saying that substances other than the substances described in the embodiments of the invention can be substances realizing the present invention as long as they do not depart from the gist of the present invention.
[0102]
[Appendix]
A substance having an atomic number close to that of tantalum is tungsten.
[0103]
A substance having an atomic number close to that of barium is iodine or tin.
[0104]
The said predetermined thickness is 3 mm or less, The radiation shield characterized by the above-mentioned.
[0105]
A radiation shield, wherein the lower strength component of the first and second components is covered with the higher strength component.
[0106]
Radiation, wherein a component having a lower attenuation index of the first component and the second component is provided closer to the radiation shield than a component having a higher attenuation index. Shield.
[0107]
The main substance of the first component is iron or a substance having an atomic number close to iron, and the main substance of the second component is tantalum or a substance having an atomic number close to tantalum. Radiation shield.
[0108]
The thickness of the main substance of the first component is determined by calculating the attenuation index obtained when the first component and the second component are combined to have an appropriate thickness, respectively. A radiation shield characterized in that the thickness is less than or equal to 2/3 of the thickness achieved when the radiation shield is used alone.
[0109]
When the attenuation coefficient obtained by combining the first component and the second component at appropriate thicknesses is X times the attenuation coefficient obtained by lead having a thickness of 1 mm, A value obtained by reducing the thickness of the main substance of the constituent element by 1 / X is less than 0.75 mm.
[0110]
The main substance of the first component is barium or a substance whose atomic number is close to barium, and the main substance of the second component is iron or a substance whose atomic number is close to iron. Radiation shield.
[0111]
The thickness of the main substance of the second component is determined by calculating the attenuation index obtained when the first component and the second component are combined to have appropriate thicknesses, respectively. A radiation shield characterized in that the thickness is less than or equal to 2/3 of the thickness achieved when the radiation shield is used alone.
[0112]
When the attenuation coefficient obtained when the first component and the second component are combined at an appropriate thickness is X times the attenuation coefficient obtained by lead having a thickness of 1 mm, A value obtained by reducing the thickness of the main substance of the constituent element to 1 / X is less than 7.5 mm.
[0113]
The main material of the first component is barium or a material whose atomic number is close to barium, and the main material of the second component is tantalum or a material whose atomic number is close to tantalum. Radiation shield.
[0114]
The thickness of the main substance of the first component is determined by calculating the attenuation index obtained when the first component and the second component are combined to have an appropriate thickness, respectively. A radiation shield characterized in that the thickness is less than or equal to 2/3 of the thickness achieved when the radiation shield is used alone.
[0115]
【The invention's effect】
According to the present invention, a radiation shield can be formed without mainly using lead by combining a plurality of substances in which each substance can compensate for each other's weak points.
[Brief description of the drawings]
FIG. 1 is a side view of an X-ray diagnostic apparatus for explaining the present invention.
FIG. 2 is a side view of an X-ray diagnostic apparatus showing an example in which the radiation shield of the present invention is applied to a photomultiplier tube.
FIG. 3 is an attenuation coefficient characteristic diagram showing an attenuation coefficient characteristic of lead.
FIG. 4 is an attenuation index characteristic diagram showing an example in which the attenuation index by the combination of the substances of the present invention exceeds the attenuation index of lead.
FIG. 5 is a sectional view showing a first example of the structure of the radiation shield according to the first embodiment of the present invention.
FIG. 6 is a sectional view showing a second example of the structure of the radiation shield according to the first embodiment of the present invention.
FIG. 7 is a sectional view showing an example of an arrangement structure of the radiation shield according to the first embodiment of the present invention with respect to the X-ray detector.
FIG. 8 is a diagram showing an example of an attenuation index characteristic of the radiation shield according to the first embodiment of the present invention.
FIG. 9 is a diagram showing the relationship between the thicknesses of iron and tantalum which provide an attenuation index equal to or higher than that of lead.
FIG. 10 is a diagram showing an example of attenuation coefficient characteristics of a substance relating to stainless steel.
FIG. 11 is a diagram showing an example of an attenuation coefficient characteristic of a substance whose atomic number is close to that of iron.
FIG. 12 is a graph showing attenuation coefficient characteristics of tantalum and tungsten.
FIG. 13 is a sectional view showing a first example of the structure of the radiation shield according to the second embodiment of the invention.
FIG. 14 is a sectional view showing a second example of the structure of the radiation shield according to the second embodiment of the invention.
FIG. 15 is a sectional view showing a third example of the structure of the radiation shield according to the second embodiment of the invention.
FIG. 16 is a cross-sectional view illustrating a first example of an arrangement structure of a radiation shield according to a second embodiment of the present invention with respect to an X-ray detector.
FIG. 17 is a sectional view showing a second example of the arrangement structure of the radiation shield according to the second embodiment of the present invention with respect to the X-ray detector.
FIG. 18 is a diagram illustrating an example of an attenuation index characteristic of the radiation shield according to the second embodiment of the present invention.
FIG. 19 is a diagram showing the relationship between the thicknesses of iron and barium that obtain an attenuation index equal to or higher than that of lead.
FIG. 20 is a graph showing attenuation coefficient characteristics of barium and iodine.
FIG. 21 is a sectional view showing a first example of the structure of the radiation shield according to the third embodiment of the present invention.
FIG. 22 is a sectional view showing a second example of the structure of the radiation shield according to the third embodiment of the present invention.
FIG. 23 is a sectional view showing a third example of the structure of the radiation shield according to the third embodiment of the present invention.
FIG. 24 is a cross-sectional view showing an example of an arrangement structure of a radiation shield according to a third embodiment of the present invention with respect to an X-ray detector.
FIG. 25 is a diagram showing an example of an attenuation index characteristic of the radiation shield according to the third embodiment of the present invention.
FIG. 26 is a diagram showing the relationship between the thicknesses of tantalum and barium that provide an attenuation index equal to or greater than that of lead.
[Explanation of symbols]
1 ... X-ray generator
3 ... sleeper
4,70,160,240 ... X-ray detector
6, 9 ... radiation shield
7 ... Photomultiplier tube
8 ... TV camera
51, 131 ... iron
52, 211 ... tantalum
81, 181, 251 ··· attenuation characteristic of lead
82: Attenuation index characteristic when iron and tantalum are combined
101: Attenuation coefficient characteristics of iron
121: attenuation coefficient characteristics of tantalum
132, 212 ・ ・ ・ Barium
182: Attenuation index characteristic when iron and barium are combined
201 ・ ・ ・ Attenuation coefficient characteristics of barium
252: attenuation index characteristics when tantalum and barium are combined

Claims (8)

A first constituent element whose main substance is iron or a substance whose atomic number is close to iron, and a main substance whose atomic number is larger than that of the first constituent element and whose atomic number is smaller than that of lead. A radiation shield comprising: a second component. The radiation shield according to claim 1, wherein the substance whose atomic number is close to that of iron is any one of titanium, chromium, manganese, cobalt, nickel, copper, and zinc. 3. The radiation shield according to claim 1, wherein a main substance of the second component is tantalum or a substance whose atomic number is close to that of tantalum. 4. A non-solid second component comprising a first component composed of one or more substances and one or more substances, wherein the attenuation coefficient of the primary substance is greater than the attenuation coefficient of the primary substance of the first component; And a component, wherein the first component is disposed so as to cover the second component with respect to the radiation shield. The radiation shield according to claim 4, wherein the main substance of the second component is barium or a substance whose atomic number is close to barium. A first component mainly composed of a substance other than lead; and a second configuration mainly composed of a substance other than lead, wherein at least one of the strength and the attenuation coefficient exceeds that of the main substance of the first component. And an attenuation index determined by the attenuation coefficient and the thickness of the substance, wherein the attenuation index when the first component and the second component are combined to have an appropriate thickness is a predetermined thickness. A radiation shield that is equal to or more than the attenuation index of lead. An X-ray detection unit that detects X-rays transmitted through the subject;
A first constituent element whose main substance is iron or a substance whose atomic number is close to iron, and a main substance whose atomic number is larger than that of the first constituent element and whose atomic number is smaller than that of lead. A radiation shield comprising: a second component; and a radiation shield provided on a side different from the subject with respect to the X-ray detection unit and used for use. vessel. An X-ray generation unit that generates X-rays,
An X-ray detection unit that detects X-rays generated by the X-ray generation unit and transmitted through the subject;
A first constituent element whose main substance is iron or a substance whose atomic number is close to iron, and a main substance whose atomic number is larger than that of the first constituent element and whose atomic number is smaller than that of lead. A radiation diagnostic apparatus, comprising: a radiation shield comprising: a second component; and a radiation shield provided on a side different from the subject with respect to the X-ray detection unit.

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