JPH0358733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simultaneous multilayer tomography apparatus using a stimulable phosphor sheet.

2. Description of the Related Art Tomography is conventionally known as a method for obtaining an X-ray tomographic image of only a desired tomographic plane of an X-ray subject.

In this method, an X-ray tube and an X-ray photographic film are arranged with the X-ray object in between, and during X-ray irradiation, the X-ray tube and X-ray photographic film are moved using a straight line rule (X-ray tube) centered on the tomographic plane of the X-ray object. The focus of By moving the object relatively so as to satisfy the following conditions, only the desired tomographic plane is imaged on the X-ray photographic film, and the tomographic planes of other objects are blurred.
An X-ray image of only the desired tomographic plane of the object can be obtained.

Furthermore, simultaneous multilayer tomography is known as a method in which images of a plurality of tomographic planes of an X-ray object are obtained at once (simultaneously) by stacking a plurality of X-ray photographic films and performing the same imaging as described above.

In the tomography method, it is sufficient that the above-mentioned linear law and geometric ratio law hold, and any method of moving the X-ray tube and the X-ray photographic film, such as linear, circular, elliptical, or spiral, can be used.

Such tomography techniques are described in detail in the "Radiation Technology Guide" published by the Tokyo Radiological Technologists Association.

In particular, simultaneous multilayer tomography can obtain images of multiple tomographic planes of an X-ray object in a single scan, so for example, for moving organs such as the heart and lungs, tomographic images with exactly the same motion phase can be obtained. In other areas, images of multiple tomographic planes can be obtained without any unavoidable movement of the subject between each tomographic image, further reducing radiation exposure and improving the physical and mental health of the subject. It is convenient for diagnosis because it reduces the burden on patients.

However, in conventional simultaneous multilayer tomography, the X-rays transmitted through the X-ray object are transmitted through multiple X-rays.
As it passes through the X-ray photographic film, it attenuates, and the density is higher in the upper layers of the X-ray photographic film and lower in the lower layers, so the sensitivity of the X-ray photographic film and intensifying screen must be adjusted. Therefore, it is necessary to correct variations in the density of each layer, but it is generally extremely difficult to balance the sensitivity of such X-ray photographic films and intensifying screens depending on the X-ray subject. There is also a limit to increasing the sensitivity of the bottom layer of X-ray photographic film, and even if an intensifying screen is used in combination, sufficient sensitivity cannot be obtained. Furthermore, lower energy X-rays are absorbed by the upper layer of X-ray photographic film, and higher energy X-rays are absorbed by the upper layer of X-ray photographic film.
Since the higher the line, the higher the contrast reaches the lower layer of the X-ray photographic film, the higher the contrast is in the upper layer of the X-ray photographic film, and the lower the contrast is in the lower layer, so it is essential to adjust the gamma value of the X-ray photographic film for each layer. However, it has been extremely difficult to prepare an X-ray photographic film whose γ value is adjusted depending on the X-ray subject. For these reasons, in conventional simultaneous multilayer tomography, it is generally extremely difficult to obtain X-ray images with high diagnostic performance, and the number of layers of X-ray photographic film and intensifying screen is only 4 at most. The limit is ~5 layers, and in order to obtain a large number of tomographic images, imaging must be performed multiple times.

With the aim of eliminating the drawbacks of the above-mentioned conventional simultaneous multilayer tomography method, the present applicant filed a patent application
In the specification of No. 165116, a laminate consisting of a plurality of stimulable phosphor sheets and an X-ray tube are arranged with an X-ray object interposed therebetween, and when irradiating the X-ray, the laminate and the
A simultaneous multilayer tomography method has been proposed, which is characterized in that the X-ray tube is moved relative to a certain cross-sectional layer of the X-ray object so as to satisfy the linear law and the geometric ratio law.

Here, the storage phosphor refers to radiation (X-rays, α
rays, beta rays, gamma rays, ultraviolet rays, etc.), a part of this radiation energy is accumulated internally, and when excitation light such as visible light is irradiated, stimulated luminescence occurs with an amount of light corresponding to the accumulated energy. A substance that has the property of emitting light.

A sheet provided with a layer of such a stimulable phosphor is irradiated with radiation that has passed through the subject, and information about the subject is stored and recorded in the stimulable phosphor as radiation image information, and then laser light, etc. The stimulable phosphor sheet is scanned with excitation light to emit radiation image information as stimulated luminescent light, this stimulated luminescent light is read photoelectrically as an image signal, and the image signal is subjected to desired signal processing. The applicant has already proposed a radiation image system in which a visible image is output on a recording medium such as a photographic light-sensitive material or a display device such as a CRT. (Unexamined Japanese Patent Publication No. 55-12492
No. 56-11395, etc. ) This system has the very practical advantage of being able to record images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated and emitted by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure changes considerably due to various imaging conditions, the amount of emitted light can be read by the photoelectric conversion means by setting the reading gain to an appropriate value and converted into an electrical signal, and this electrical signal can be converted into an electrical signal. By outputting a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure can be obtained.

In addition, according to this system, the radiation image information accumulated and recorded in the stimulable phosphor is converted into an electrical signal, then subjected to appropriate signal processing, and this electrical signal is used to produce recording materials such as photographic light-sensitive materials, CRTs, etc. By outputting the image as a visible image on a display device, a very large effect can be obtained in that a radiation image with excellent suitability for observation and interpretation (diagnosis) can be obtained.

In this way, in a radiation imaging system using a stimulable phosphor, by setting the reading gain to an appropriate value and reading the stimulated luminescence light photoelectrically,
X as required for each layer in conventional simultaneous multilayer tomography methods, since it is easily possible to correct deviations from the desired level of radiation energy stored in the storage fluorophore. It is not necessary to balance the sensitivity of the line photographic film and the intensifying screen; it is possible to use a stimulable phosphor of the same sensitivity in each layer, or to balance the sensitivity of the stimulable phosphor in each layer. Even when changing the sensitivity, it is not necessarily required to maintain a strict sensitivity balance. Furthermore, in the past, there was a limit to the number of layers in the laminate due to limitations in the sensitivity of the X-ray photographic film and intensifying screen, but in this system, by appropriately setting the value of the reading gain, the cumulative Since the sensitivity of the light body can be corrected, it is possible to significantly increase the number of layers in the stacked body, in other words, it is possible to obtain a tomographic image with a much larger number of layers than before in one imaging session. . Furthermore, by performing gradation processing on the photoelectrically read image signal, the contrast of the output radiation image can be easily corrected as desired. It becomes possible to obtain a large number of tomographic images with the same contrast without requiring strict adjustment of the γ value of the X-ray photographic film.

As described above, the simultaneous multilayer tomography method proposed in Japanese Patent Application No. 165116/1985 has great effects, but if a stimulable phosphor sheet with the same specifications is used for each layer, The problem remained that it was difficult to make the image quality of tomographic images completely the same. This is because the energy of the X-rays transmitted through the X-ray object is sequentially absorbed by the stimulable phosphor of each stimulable phosphor sheet as it passes through the laminated stimulable phosphor sheets. The more stimulable phosphor sheets reach this
This is due to the fact that the linear energy decreases. In other words, the upper layer of the stimulable phosphor sheet absorbs a larger amount of X-ray energy, and therefore a radiographic image with a larger amount of information is recorded. Only X-ray energy is absorbed, and therefore only radiographic images containing less information are recorded. When each stimulable phosphor sheet on which a radiation image is recorded in this way is irradiated with excitation light, the upper stimulable phosphor sheet that absorbs a larger amount of X-ray energy emits a larger amount of stimulated luminescence light. On the other hand, the underlying stimulable phosphor sheet, which absorbs only a small amount of X-ray energy, will emit only a small amount of stimulated luminescence light. Therefore, in order to make the density level of the tomographic image of each layer uniform, it is necessary to increase the reading gain value toward the lower layers. However, increasing the reading gain value actually increases the amplification of X-ray quantum noise. The lower the tomographic image, the lower the S/N ratio and the lower the diagnostic performance.

In addition, in the simultaneous multilayer tomography method, the number of tomograms obtained at one time is determined by whether or not the lowest tomogram is sufficient for diagnosis. When a laminate consisting of is used, the number of tomographic images obtained at one time is not necessarily large for the reasons mentioned above.

The present invention was made in order to solve the above-mentioned problems in simultaneous multilayer tomography in which a laminate consisting of a plurality of stimulable phosphor sheets is used.
The purpose is to provide a simultaneous multilayer tomography apparatus capable of obtaining uniform tomographic images with high diagnostic performance for each layer.

Another object of the present invention is to provide a simultaneous multilayer tomography apparatus capable of obtaining an extremely large number of tomographic images in one imaging operation.

The present invention achieves the above object by arranging a plurality of stimulable phosphor sheets to form a laminate so that the stimulable phosphor sheet with higher X-ray utilization efficiency is located farther from the X-ray subject. It is something to be achieved. That is, the simultaneous multilayer tomography apparatus of the present invention includes a laminate made of a plurality of stimulable phosphor sheets;
An X-ray tube is placed through the X-ray object, and during X-ray irradiation, the laminated body and the X-ray tube are set according to the straight line rule and the geometric ratio rule around a predetermined tomographic plane of the X-ray object. In a simultaneous multilayer tomography device that allows satisfactory relative movement, the laminate includes a plurality of stacked sheets stacked such that a stimulable phosphor sheet with higher X-ray utilization efficiency is located farther from the X-ray object. It is characterized by being made of a fluorescent phosphor sheet.

In the present invention, the X-ray utilization efficiency means how much irradiated X-ray energy can be finally converted into stimulated luminescence light, and it refers to the amount of stimulable luminescent light that can be converted into the stimulable luminescence of each stimulable phosphor that constitutes the laminate. A method for changing the X-ray utilization efficiency of a sheet is to change the thickness of the phosphor layer of each sheet (generally speaking, if the thickness of the phosphor layer is increased, the X-ray utilization efficiency will increase in proportion to this). Examples include a method of changing the type of stimulable phosphor constituting the stimulable phosphor layer of each sheet, and a combination of the above two methods.

According to the present invention, it is possible to obtain a tomographic image of uniform image quality with high diagnostic properties for each layer. Further, according to the present invention, an extremely large number of tomographic images can be obtained in one imaging operation.

FIG. 1 is a graph illustrating the relationship between the number of layers of a tomographic plane and the amount of stimulated luminescence light obtained when excitation light is irradiated.

In Figure 1, the dotted line indicates a stack of 10 stimulable phosphor sheets (i.e., stimulable phosphor sheets with the same specifications) that are made of the same type of phosphor and have phosphor layers of the same thickness. Then, each stimulable phosphor sheet is irradiated with X-rays with a tube voltage of 120 KVp, and the amount of stimulated luminescence light obtained is calculated for each layer number of each stimulable phosphor sheet. It is plotted. In this case, the amount of light emitted from the 10th layer of the stimulable phosphor sheet is approximately 1/20 of the amount of light emitted from the 1st layer of the stimulable phosphor sheet. As is clear from Fig. 1, when stimulable phosphor sheets with phosphor layers of the same specifications are used,
Images sufficient for diagnosis can only be obtained up to the 7th layer, and the information amount of the radiographic image accumulated and recorded on the stimulable phosphor sheet of the 1st layer and the 7th layer can be obtained at most.
It can be seen that the amount of information of the radiation image accumulated and recorded on the stimulable phosphor sheet of the layer is considerably different, and the image quality of the obtained tomographic image is also considerably different in terms of S/N ratio.

On the other hand, in FIG. 1, the solid line indicates that three types of stimulable phosphor sheets are used, each using the same phosphor but with three different phosphor layer thicknesses. Nine stimulable phosphor sheets are stacked so that the thickness of
The amount of stimulated luminescence obtained by irradiating each stimulable phosphor sheet with X-rays and then irradiating each stimulable phosphor sheet with excitation light is plotted against the layer number of each stimulable phosphor sheet. . In this case, although there is a slight variation in the amount of light emitted between stimulable phosphor sheets with phosphor layers of the same thickness, all tomographic images obtained from all 9 layers of stimulable phosphor sheets can be used for diagnosis. It can be seen that this provides a sufficient image to be used for. In addition, the amount of information in the radiographic images accumulated and recorded on the nine layers of stimulable phosphor sheets is almost the same, so all tomographic images obtained have high S/N ratios and high diagnostic performance. I understand.

As in the case of Fig. 1, three types of stimulable phosphor sheets with three different phosphor layer thicknesses were each used.
It goes without saying that instead of using one sheet at a time, the thickness of the phosphor layer of each sheet may be changed so that it becomes thicker from the upper layer to the lower layer. The image quality can be made uniform. The above also applies when the type of stimulable phosphor is changed without changing the thickness of the phosphor layer, or when both the thickness of the phosphor layer and the type of stimulable phosphor are changed. It has been found that almost the same effect can be obtained.

In the present invention, the stimulable phosphor used in the stimulable phosphor sheet is such that the wavelength range of stimulated luminescence light emitted by excitation light irradiation does not overlap with the wavelength range of the excitation light. This is desirable for improving the /N ratio. Specifically, it is preferable to use excitation light in a wavelength range of 450 to 700 nm and emit stimulated luminescence light in a wavelength range of 300 to 500 nm.

As described above, examples of stimulable phosphors that emit stimulated luminescence light in the wavelength range of 300 to 500 nm and that can be preferably used in the present invention include rare earth element-activated alkaline earth metal fluorohalide phosphors [ Specifically, (Ba _1-xy , Mgx, Ca _y ) FX: aEu ²⁺ (However, X
is at least one of Cl and Br,
x and y are 0<x+y≦0.6 and xy≠0,
a is 10 ^-6 ≦ a ≦ 5 × 10 ^-2 ), - Japanese Patent Application Laid-open No. 1983-
Described in Publication No. 12145 (Ba _1-x , M〓 _x )
FX: yA (however, M〓 is Mg, Ca, Sr, Zn and
at least one of Cd, X is at least one of Cl, Br and I, A is Eu, Tb, Ce,
At least one of Tm, Dy, Pr, Ho, Nd, Yb and Er, x is 0≦x≦0.6, y is 0≦
y≦0.2); ZnS: Cu, Pb, BaO x Al ₂ O ₃ described in JP-A-55-12142:
Eu (however, 0.8≦x≦10) and M〓O・xSiO ₂ :A
(However, M〓 is Mg, Ca, Sr, Zn, Cd or Ba, and A is Ce, Tb, Eu, Tm, Pb, Tl, Bi or
Mn, x is 0.5≦x≦2.5); and LnOX:
(However, Ln is at least one of La, Y, Gd, and Lu, X is at least one of Cl and Br, and A is at least one of Ce and Tb.
and x is 0<x<0.1); In particular, rather than changing the type of phosphor used,
When configuring the laminate used in the present invention by changing the thickness of the phosphor layer of the sheet, preferred among these are rare earth element-activated alkaline earth metal fluorohalide phosphors, Among these, barium fluorohalides are particularly preferred because they have excellent photostimulable luminescence.

Furthermore, metal fluorides are added to barium fluorohalide phosphors as disclosed in Japanese Patent Application Laid-open Nos. 56-2385 and 56-2386, or Japanese Patent Application No. 150873-1983. It is preferable to add at least one of a metal chloride, a metal bromide, and a metal iodide, as disclosed in , because the stimulated luminescence is further improved.

Each of the above-mentioned storage phosphors has different X-ray utilization efficiency depending on its composition. Therefore, the stimulable phosphor sheet laminate used in the present invention can be constructed by using two or more of the above stimulable phosphors. For example, when constructing a laminate using each of the above-mentioned stimulable phosphors, the phosphors used in each sheet are generally ZnS:
Cu, Pb, M〓O・xSiO ₂ :A, ((Ba _1-xy ,
Mg _x , Ca _y )FX: aEu ²⁺ , (Ba _1-x , M〓 _x )FX:
yA and BaO xAl ₂ O ₃ :Eu (these fluorophores are ranked differently depending on the composition), LnOX:
becomes.

Furthermore, as disclosed in Japanese Patent Application Laid-open No. 163500/1983, the phosphor layer of the stimulable phosphor sheet prepared using the above-mentioned stimulable phosphor is coated with a pigment or dye. It is preferable to color the image by adding a color to improve the sharpness of the final image.

The gradation processing used in the present invention is as follows:
JP-A-55-116339, JP-A No. 55-116340, JP-A No. 55-
Examples include those disclosed in Publication No. 88740.

In the present invention, in addition to gradation processing, in order to improve the image quality of radiographic images and improve diagnostic performance,
Frequency processing as disclosed in No. 54-151398, No. 54-151400, etc. can be used in combination.

Further, in the present invention, the reading gain during reading is adjusted and the gradation processing is performed on the image signal after photoelectric conversion, depending on the radiation energy accumulated in the stimulable phosphor of each layer constituting the laminate. is effective for further uniformizing the image quality of tomographic images of each layer, but for this purpose it is necessary to understand in advance the accumulated record information about the radiation energy accumulated and recorded in the stimulable phosphor. . For example, Japanese Patent Application No. 56-165111, No. 56-165112
No. 56-165113, No. 56-165114, No. 56-
165115, the methods disclosed in each specification,
After the device performs a reading operation in advance to obtain accumulated recorded information about radiant energy using excitation light with low energy, the reading gain is set and the gradation processing conditions are set based on this accumulated recorded information. After carrying out the above steps, it is desirable to irradiate the stimulable phosphor sheet with excitation light again and output a radiation image based on the obtained stimulated luminescent light. However, the method for obtaining accumulated record information regarding the radiation energy accumulated and recorded in the stimulable phosphor is not limited to this method, and is as disclosed in Japanese Patent Application Laid-Open No. 55-50180. A method using so-called "instantaneous light emission" and various other methods can also be used.

The present invention will be described in detail below with reference to FIG. FIG. 2 is a schematic diagram illustrating the simultaneous multilayer tomography method of the present invention. In Figure 2, X-ray tube 1
1, a plurality of stimulable phosphor sheets 12a, which are stacked such that the stimulable phosphor sheets with higher X-ray utilization efficiency are located farther from the X-ray subject 14;
A cassette 13 containing X-ray objects 12b, . . . 12n is arranged with an X-ray object 14 in between.

During imaging, while moving the X-ray tube 11 and cassette 13 in the directions of arrows 15 and 16,
An X-ray object 14 is irradiated with X-rays from a ray tube 11 .
As a result, the tomographic planes 18a, 18 of the X-ray object 14
The tomographic images b, . . . 18n are sequentially stored and recorded as X-ray energy on the stimulable phosphor sheets 12a, 12b, .

In this case, the stimulable phosphor sheets 12a, 12
b, . . . 12n are stacked so that the sheets with higher X-ray utilization efficiency are located farther from the X-ray object 14, so that the X-rays transmitted through the X-ray object 14
The energy of the line is absorbed in each sheet in a nearly uniform distribution. Therefore, the tomographic images of the tomographic planes 18a, 18b, . They are almost the same across the board at a diagnosable level.

In this way, the stimulable phosphor sheets 12a, 12b, . . . 12n subjected to simultaneous multilayer tomography are sent to a reading device.

FIG. 3 shows stimulable phosphor sheets 12a, 12.
b, . . . 12n for reading the accumulated record information accumulated and recorded in the stimulable phosphor sheets 12a, 12b, . 2 is a schematic diagram of a reading device including a main reading reading section 32 that reads radiographic image information.

In the prefetch reading unit 21, a laser light source 22
The laser beam 23 emitted from the filter 2 cuts the wavelength region of the stimulated luminescent light emitted from the stimulable phosphor sheet 20 by the excitation of the laser 23.
After passing through the optical deflector 2, such as a galvano mirror,
5, the light is one-dimensionally deflected and incident on the stimulable phosphor sheet 20 via the plane reflecting mirror 26. Here, the laser light source 22 is selected so that the wavelength range of the laser light 23 does not overlap with the wavelength range of the stimulated luminescent light from the stimulable phosphor sheet 20. On the other hand, the phosphor sheet 20 is moved in the direction of the arrow 27 to perform sub-scanning, and as a result, the entire surface of the phosphor sheet 20 is irradiated with laser light. Here, the power of the laser light source 22, the beam diameter of the laser light 23, the scanning speed of the laser light 23,
The transport speed of the phosphor sheet 20 is selected such that the energy of the laser beam 23 for pre-reading is smaller than that for main reading. Laser light 23
When the stimulable phosphor sheet 20 is irradiated with
emits stimulated luminescent light with an amount proportional to the stored and recorded X-ray energy, and this luminescent light enters the light-guiding sheet 28 for pre-reading. The light guiding sheet 28 has a linear incident surface and is disposed adjacent to and opposite to the scanning line on the stimulable phosphor sheet 20, and an annular exit surface for detecting light such as a photoprint. It is brought into close contact with the light receiving surface of the vessel 29.
This light guide sheet 28 is made by processing a transparent thermoplastic resin sheet such as acrylic resin, and is configured so that the light incident from the incident surface is transmitted to the exit surface while being totally reflected inside. The stimulated luminescent light from the stimulable phosphor sheet 20 is guided through the light guide sheet 28, exits from the exit surface, and is received by the photodetector 29. The preferred shape, material, etc. of the light guiding sheet are disclosed in Japanese Patent Application Laid-Open No. 55-87970,
It is disclosed in Publication No. 56-11397, etc.

A filter is attached to the light receiving surface of the photodetector 29, which transmits only light in the wavelength range of stimulated luminescence light and cuts out light in the wavelength range of excitation light, and detects only stimulated luminescence light. It's getting wet. Photodetector 2
The stimulated luminescent light detected by 9 is converted into an electrical signal and further amplified by amplifier 30. The accumulated recording information of the X-ray image information output from the amplifier 30 is input to the control circuit 31 of the main reading reading section 32. The control circuit 31 adjusts the amplification factor setting value a and the recording scale scale according to the obtained accumulated record information so that a tomographic image with more uniform density and contrast in each tomographic plane and with good diagnostic performance can be obtained. Actor setting value b and reproduction image processing condition setting value c are output. Storable phosphor sheet 2 with pre-reading completed
0 is transferred to the reading section 32 for main reading.

In the reading unit 32 for main reading, the laser beam 34 emitted from the laser light source 33 for main reading is excited by the laser beam 34, and the stimulable phosphor sheet 2 is
After passing through a filter 35 that cuts out the wavelength range of the stimulated luminescence light emitted from zero, the beam diameter is strictly adjusted by a beam expander 36, and the beam diameter is strictly adjusted by an optical deflector 37 such as a galvanometer mirror. 38 onto the stimulable phosphor sheet 20. An fθ lens 39 is arranged between the optical deflector 37 and the plane reflecting mirror 38,
Even when the laser beam 34 scans the phosphor sheet 20, it always has a uniform beam diameter. On the other hand, the phosphor sheet 20 is moved in the direction of the arrow 40 to perform sub-scanning, and as a result, the entire surface of the phosphor sheet 20 is irradiated with laser light. When the laser beam 34 is irradiated in this way, the stimulable phosphor sheet 20 emits stimulated luminescent light with an amount proportional to the accumulated and recorded X-ray energy, and this emitted light is transmitted to the light guide sheet for book reading. 41. The light guide sheet 41 for main reading has the same material and structure as the light guide sheet 28 for prereading. Stimulated luminescent light guided through the light guiding sheet 41 for main reading while undergoing repeated total reflection is emitted from its exit surface and is received by the photodetector 42. A filter that selectively transmits only the wavelength range of the stimulated luminescence light is attached to the light receiving surface of the photodetector 42, so that the photodetector 42 detects only the stimulated luminescence light. The stimulated luminescence light detected by the photodetector 42 is converted into an electrical signal, and after being amplified to an electrical signal of an appropriate level by the amplifier 43 whose sensitivity is set by the amplification factor setting value a, the stimulated luminescence light is converted to an electrical signal. 44. The A/D converter 44 converts the digital signal into a digital signal using a scale factor suitable for the signal fluctuation width according to the recorded scale factor setting value b, and inputs the digital signal to the signal processing circuit 45 . The signal processing circuit performs signal processing based on the reproduction image processing condition setting value c to obtain an X-ray image with the same density and contrast of the tomographic image of each tomographic plane and excellent suitability for observation and interpretation, and transmits it to the recording device. be done. Recording devices include those that optically record by scanning a photosensitive material with a laser beam or the like;
Various methods can be used, including those that display electronically on a CRT, etc., those that record the X-ray image displayed on a CRT, etc. on a video printer, etc., and those that record on a heat-sensitive recording material using heat rays. .

It goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made.

For example, as a method to make the contrast and density of the tomographic image of each tomographic plane more uniform, instead of amplifying the output of the photodetector 42 to an appropriate level signal with the amplifier 43, the photodetector 42 can be used as a photoelectronic When using a multiplier tube, the applied voltage may be changed depending on the amplification factor setting value a, or the A/D converter 44 may convert the voltage into a digital signal using a scale factor suitable for the signal fluctuation width. Alternatively, the signal fluctuation width may be optimized using an analog amplifier and then converted into a digital signal using the A/D converter 44 in accordance with the recording scale factor setting value b.

Further, as described above, the method of relative movement between the X-ray tube 11 and the cassette 13 is not limited to linear movement, but may be circular, elliptical, spiral, or the like.

[Brief explanation of drawings]

Figure 1 shows the number of tomographic layers in a simultaneous multilayer tomography system using a stimulable phosphor sheet laminate;
This is a graph illustrating the relationship between the amount of stimulated luminescence light obtained when irradiated with excitation light. This figure shows the above relationship in an embodiment. FIG. 2 is a schematic diagram illustrating the simultaneous multilayer tomography apparatus of the present invention. FIG. 3 is a schematic diagram of a preferred reading device for use in the present invention. 11...X-ray tube, 12a, 12b, 12c, 1
2n, 20...Storage phosphor sheet, 13...Cassette, 14...X-ray object, 17a, 17a',
17n, 17n'...X-ray, 18a, 18b, 18
c, 18n...Tomographic plane, 21...Reading section for pre-reading, 22...Laser light source for pre-reading, 23...Laser light, 24...Filter, 25...Optical deflector, 2
6...Flat reflecting mirror, 28...Light guide sheet for pre-reading, 2a...Photodetector, 30...Amplifier, 31...
...Control circuit, 32... Reading section for main reading, 33...
Laser light source for main reading, 34... Laser light, 35...
...Filter, 36...Beam expander, 3
7...Light deflector, 38...Plane reflecting mirror, 39...
fθ lens, 41...Light guide sheet for book reading, 42
...Photodetector, 43...Amplifier, 44...A/D
Converter, 25...signal processing circuit.

Claims (1)

[Claims] 1. A laminate consisting of a plurality of stimulable phosphor sheets and an X-ray tube are arranged with an X-ray object in between,
In the simultaneous multilayer cross-sectional imaging device, the laminated body and the X-ray tube are moved relative to each other around a predetermined tomographic plane of the X-ray object so as to satisfy the straight line rule and the geometric ratio rule during radiation irradiation. The stimulable phosphor sheet whose laminate has higher X-ray utilization efficiency is the
A simultaneous multilayer tomography apparatus characterized by comprising a plurality of stimulable phosphor sheets stacked so as to be located farther from a linear object. 2. The laminate is characterized in that the laminate is composed of a plurality of stimulable phosphor sheets stacked such that the stimulable phosphor sheet having a thicker phosphor layer is located farther from the X-ray object. A simultaneous multilayer tomography apparatus according to claim 1. 3. The laminate includes a plurality of stimulable phosphor sheets laminated such that the stimulable phosphor sheet having a phosphor layer made of a phosphor with higher X-ray utilization efficiency is located farther from the X-ray object. The simultaneous multilayer tomography apparatus according to claim 1, characterized in that it is made of a light sheet.