JPH05146426A - Scattering line tomography and scattering line tomography device - Google Patents

Abstract

PURPOSE:To realize the scattering line tomography and its device by which scanning is executed one-dimensionally, the photographing time is shortened, and the exposure dose is extremely small. CONSTITUTION:Pencil beam-like X rays XR are made incident on a body to be measured. In X rays scattered from plural discrete points existing on a straight line of an incident path, only a scattering line of a specific angle is allowed to pass through by slits SL1, SL2 of a shape for forming a concentric circle or a part of a concentric circle, detected by a detector element DE1 of a detector DET of the same shape as the slits SL1, SL2 and a collection of data is executed, and when irradiation on all straight lines of a straight line x=xj is finished, imaging is executed by using the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scattered radiation tomography and a scattered radiation tomography for injecting radiation such as X-rays and non-destructively displaying an image of the internal structure of the subject by the radiation scattered by the subject. Regarding the device.

[0002]

2. Description of the Related Art Radiation CT irradiates a subject with radiation, detects the radiation attenuated by the transmission with a detector, performs this in all directions of the subject, and reconstructs the obtained data as an image. It is a device for displaying a tomographic image.
Hereinafter, only X-ray radiation will be described. The description for X-rays is the same for other radiations.

The CT performed using X-rays includes scattered X-ray tomography using scattered X-rays, as well as normal X-ray CT using transmitted X-rays as described above. This method irradiates the subject with X-rays and scatters at a certain angle among the X-rays scattered by the target.
This is a method of detecting a line and displaying an image.

This scattering imaging has the following advantages. (A) Unlike ordinary X-ray CT, imaging can be performed only with scattered rays from a scattering source. Therefore, local photographing and imaging can be performed.

(B) There is a possibility of obtaining an image at the same time as photographing, and real-time imaging of the heart or the like is expected. (C) A normal X-ray CT can only photograph a cross section substantially perpendicular to the body axis, but the scattering imaging can photograph a cross section in any direction. Therefore, the resolution in any direction can be increased equally.

(D) It is said that it is possible to identify a substance or structure (crystal structure, texture or fiber structure, molecular structure, kind of substance, etc.).

[0007]

In the scattered radiation tomography having the above advantages, the conventional method has the following problems.

(B) Considering that the cross-section to be photographed is divided into a lattice shape, scanning is performed point by point in the y-axis direction, and when scanning of one line in the y-axis direction is completed, the line is advanced in the x-axis direction, y Perform an axial scan. As described above, the conventional scattering imaging method requires two-dimensional scanning, and thus takes a very long time to capture an image.

(B) Since the object is two-dimensionally scanned in radiography, the amount of X-ray exposure is very large. The present invention has been made in view of the above points, and an object thereof is to realize a scattered radiation tomography and an apparatus thereof capable of performing scanning one-dimensionally and shortening an imaging time.

Another object of the present invention is to realize a scattered radiation tomography apparatus and a device having an extremely low exposure dose as compared with the conventional scattered radiation tomography apparatus and device.

[0011]

According to the present invention for solving the above-mentioned problems, a pencil beam-like radiation is made incident on an object to be measured, and radiation scattered from a plurality of discrete points on a straight line of an incident path is detected. , The shape of which forms a concentric circle or a part of a concentric circle in a plane perpendicular to the traveling direction of the beam-like radiation, and the void is simultaneously extracted by a slit having a certain angle with respect to the traveling direction of the beam-like radiation. , Collecting and collecting data by detecting a plurality of extracted and discretized scattered radiation with a plurality of detector elements having the same shape as the slit, and imaging the measured object by scattered radiation using the collected data It is characterized by performing.

In a second aspect of the present invention, x and y coordinates are taken on a two-dimensional cross section of a reconstruction area including a subject, and pencil beam-shaped radiation is straight line x parallel to the y axis from one direction of the y axis. = X
Radiation which is incident on _j and scattered from each of a plurality of discrete coordinate points on the straight line is detected by the method according to claim 1 to collect data, and the incident position of the radiation beam is re-detected. Data is collected by detecting scattered radiation for each radiation beam incident on all the straight lines x = x _j parallel to the y-axis, which are changed relative to the constituent region, by a detector element, Two-dimensional imaging of the object to be measured by scattered radiation is performed using the collected data.

According to a third aspect of the present invention, a three-dimensional reconstruction area including an object to be measured is divided into a plurality of two-dimensional cross sections, and data is collected for each two-dimensional cross section by the method according to claim 2. After that, two-dimensional imaging is performed on the two-dimensional cross section, and this is performed on all the divided two-dimensional cross sections to perform three-dimensional imaging of the measured object.

Further, a fourth invention is a gantry having a table for accommodating an object to be measured, a radiation source for measurement and a detector, and a table / gantry control device for controlling the operation of the table and the gantry. In a scattered radiation tomography apparatus having a data collection device for collecting data and a data processing device for processing data to perform image reconstruction, the radiation source irradiates the measured object and scatters on the transmission path. At least one slit having a shape forming at least a part of a concentric circle for selecting the radiation which passes through the generated radiation and is scattered at a certain angle, and the slit having a shape equivalent to the slit. A detector having a detector element at a position capable of detecting passing radiation, and a data collecting device for collecting data detected by the detector It is characterized in that it comprises.

According to a fifth aspect of the invention, the detector and the detector element include a phosphor screen for converting incident radiation into light, and a photocathode for converting light from a fluorescent image formed on the phosphor screen into electrons. ,
A plurality of multi-channel plates whose shape of the micro-channel plate for multiplying the electrons emitted from the photocathode and its arrangement for collecting the multiplied electrons is at least part of a concentric circle.
It is characterized by comprising an anode.

According to a sixth aspect of the invention, the detector and the detector element include a first phosphor screen for converting incident radiation into light.
A first photocathode that converts light from a fluorescent image formed on the first phosphor screen into electrons, and a focusing unit that forms an electron lens that focuses electrons emitted from the first photocathode and a micro
An image intensifier having any one of electron multiplying means such as a channel plate and a second fluorescent screen for converting the electrons enhanced by the means into light and emitting the light; A second photocathode for converting light incident from the image intensifier into electrons, and
The image pickup device is configured to scan the electrons output from the photocathode by the focusing means and the deflecting means, and multiply the electrons by the electron multiplying means as needed.

According to a seventh aspect of the invention, the image intensifier has a focusing means for forming an electron lens for focusing the electrons emitted from the first photocathode, and an electron intensifier such as a micro channel plate. And a doubling means.

[0018]

Operation Of the radiation scattered from a plurality of discrete points on a straight line parallel to the y axis of the pencil beam incident path, only the radiation scattered at a specific angle is directed to the traveling direction of the incident radiation. Data is collected by passing through a slit having a concentric circle or a shape forming a part of the concentric circle on a vertical surface and detecting by a detector having a similar shape. Then, the radiation source is x
When irradiation is performed in the same direction by moving in a direction parallel to the axis, data is collected by detecting this, and irradiation on all straight lines of the straight line x = x _j parallel to the y-axis is completed, the above data is obtained. Use to perform imaging.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. Embodiment 1 FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, TA is the gantry G on which the subject BDY is placed.
It is a table for storing in the subject storage hole. XG
Is an X-ray that emits X-rays to the reconstruction area RA containing the subject.
The X-ray generation source, DET, is a detector that detects the X-rays emitted from the X-ray generation source XG. SL ₁ is irradiated from an X-ray generation source XG, and a slit formed in a concentric shape that allows only X-rays in a specific direction among X-rays scattered by the subject BDY to pass therethrough, and SL ₂ is the same. This is another concentric slit that operates.

Here, FIG. 2 shows an example of the configuration of an image pickup system in this gantry G. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. The reconstruction area RA is considered to be a rectangle or a square as shown, and the horizontal axis is the x axis and the vertical axis is the y axis. In this reconstruction area RA, y = y _i (i = 1, 2,
, M), x = x _j (j = 1, 2, ..., N). Hereafter, i and j are defined as above and will not be described again.

XR is an X-ray incident from above the y-axis,
When this X-ray successively passes through each lattice point on the above x = x _j , the X-ray is scattered from each lattice point by Compton scattering or Thomson scattering depending on the energy of the X-ray. Among them, scattered rays R _i of a component forming an angle θ with X-ray XR are simultaneously extracted simultaneously by the concentric voids of the slits SL ₁ and SL ₂ and detected by each detector element DE _i of the detector DET. Here, the term “scattering from a lattice point” means that among many scattered X-rays, only X-rays in a specific direction scattered from the lattice point are allowed to pass.

The structure of the slits SL ₁ and SL ₂ is shown in FIG. In the figure, (a) is a plan view and (b) is a sectional view taken along the line S ₁ -S ₁ ′ of (a). In the figure, h ₁ , h
₂ , ..., h _i , ..., h _m are voids through which X-rays pass,
It is made with an inclination of an angle θ with respect to a straight line perpendicular to the upper and lower surfaces.

FIG. 4 is a diagram showing an outline of the structure of the detector DET. FIG. 4A is a plan view and FIG. 4B is a S ₂ -S line in FIG.
₂ 'is a cross-sectional view. In the figure, DE ₁ , DE ₂ , ...
, DE _i , ..., DE _m are the detector elements of the detector DET.

FIG. 5 is a diagram showing the structure of an example of the detector DET. In the figure, IRW is an input window through which X-rays enter,
FRB is a phosphor screen substrate, FRS is an incident window X
It is a phosphor screen that converts lines into light. PES is fluorescent screen FRS
MCP is a photocathode that emits electrons upon receiving light from a micro channel plate (Micro Channel Plate) that has a structure suitable for multiplying electron images by bundling thin tubular secondary electron multipliers.
te). MAN is Micro Channel Plate M
It is a multi-anode composed of a large number of anodes for attracting and capturing the electrons multiplied by CP, and arranged in concentric circles. The main components of this detector are housed in a vacuum tube or vacuum container. In this detector DET,
Incident light is converted into light by the fluorescent screen FRS, and the photocathode PES
Are emitted as electrons by the micro channel plate MCP, are multiplied by the secondary electron multiplying function in the micro channel plate MCP, and are output as current in the multi-anode MAN.

FIG. 6 is a diagram showing the structure of the micro channel plate MCP used in this embodiment. FIG. 6 (a) is a circular micro channel plate MCP.
In a partially cutaway perspective view of the above, CHN is a channel constituting the micro channel plate MCP. The figure (b) is an explanatory diagram of the operation of the channel CHN. As shown in the figure, the micro channel plate MCP has a large number of 10-25 μm.
It has a cylindrical shape as an assembly of channels CHN having a fine diameter of m. As shown in Fig. 2B, the channel CHN is a thin tube made of a material having a high secondary electron emission ratio and having electrodes attached to both ends and sealed in a vacuum, and a voltage is applied in the tube axial direction. When electrons are incident on the negative electrode side inner wall CIW and collide with them, secondary electrons are emitted, and the secondary electrons collide with the inner channel wall CIW again as a result of acceleration due to their own velocity and axial electric field. Then, a larger amount of secondary electrons are emitted. By repeating this, the input electrons become the multiplied output electrons.

FIG. 7 shows a micro channel plate MC
FIG. 7 is a diagram of an electric circuit related to P. In the figure, the same parts as those in FIG. 5 are designated by the same reference numerals. Photoelectric surface, as shown in FIG connected negative side of the power source E ₃ in (photocathode) PES, connect the positive side of the power source E ₃ to the electronic input side of the micro channel plate MCP, generated from the photocathode PES Photoelectrons are attracted and accelerated by this electric field. In addition, micro
Connect the negative side of the power source E ₁ to the electron incident side of the channel plate MCP, the electronic output side connected to the positive side of the power source E ₁ emit secondary electrons. The positive side of the power source E ₂ is connected to the multi-anode MAN via resistors r ₁ , r ₂ , ..., R _m , respectively, to accept secondary electrons from the micro channel plate MCP, and c ₁ , c ₂ , ..., Output from _cm terminal.

Returning to FIG. 1, the TGC is a table / gantry control device for controlling the movement of the table TA and the gantry G, and makes the movement necessary for the measurement. XGC is an X-ray generation control device for controlling X-ray generation by an X-ray generation source XG, S
The CC communicates with the operator, controls the operation of the data processing device DP, and controls the operations of the table / gantry control device TGC and the X-ray generation control device XGC.・
It is a photographing control device.

The data processing device DP is the data collecting device DA.
Various correction processing such as X-ray intensity correction and X-ray quality hardening correction is performed on the input data from S, image reconstruction processing is performed on the corrected data, and the spatial distribution of scattered X-ray intensity is calculated. Perform data processing.

The AM is a mass storage device for storing data until data processing and calculation, and for storing image data read out by the data processing device DP and reconstructed as an image. The GDC is an image display device that displays image data obtained by image reconstruction as an image.

Next, the operation of the apparatus of the embodiment configured as described above will be described while explaining the principle of tomographic image photographing by this method. The subject BDY is placed on the table TA and inserted into the gantry G at a predetermined position. After that, the table / gantry control device TGC and the X-ray generation control device XGC perform the measurement operation under the control of the operation / imaging control device SCC.

The gantry G is moved to select the reconstruction area RA which is the cross section to be photographed. The reconstructed area RA is set in a rectangular shape as shown in FIG. 2, and its center, which is the isocenter, is 0, and the orthogonal coordinate axes are x and y. X-ray XR
As a pencil beam, the X-ray generation source XG is oriented so as to be incident in parallel to the y-axis from the positive direction of the y-axis to the negative direction, and the left end of the reconstruction area RA set by the X-ray XR (or The table / gantry control unit TGC controls the gantry G so that it is located at the right end).

The X-ray generation source XG generates X-rays XR and reconstructs them.
It is incident on the formation region RA. X-ray XR is in the reconstruction area RA
Scattered by the subject, slit SL₁,slit
SL ₂Of scattered rays forming an angle θ with the y-axis by
X-ray beam X-ray XR
Scattered scattered ray R_iCorresponds to the detector DET
Detector element DE_iDetected in.

The data by the scattered radiation R _i detected by the detector DET is collected by the data collecting device DAS and stored in the mass storage device AM. The table / gantry control unit TGC controls the gantry G, and the reconstruction area RA
On the other hand, the position of the X-ray generation source XG, which is the generation position of the X-ray XR, is set to the sample interval d in the positive (or negative) direction of the x-axis.
_After moving by _x , the X-ray XR is irradiated at the position as described above, detected by the detector DET, and m pieces of data are collected as described above. All the data are collected by repeatedly carrying out at each position of all the straight lines x = x _j parallel to the y-axis whose interval is d _x . The data processing device DP stores the sent data in the mass storage device A until all data is collected.
Store in M.

At the stage when all the data have been collected, the data processing device DP reads the data stored in the mass storage device AM, and makes various corrections such as the intensity correction of the input X-rays and the X-ray quality hardening correction. After processing, image reconstruction is performed. The image-reconstructed data is displayed on the image display device GDC.

As described above, according to the apparatus of this embodiment, the X-ray source XG moves only in the x-axis direction, and in the y-axis direction, a straight line parallel to the y-axis is obtained by one X-ray irradiation. x = x
Of the X-rays scattered at each lattice point of _j , the slits SL ₁ ,
By detecting scattered rays that are incident on the detector DET at a constant angle based on the structure of SL ₂ , it is not necessary to move in the y-axis direction, and only one-dimensional scanning is required.
Further, since the intensity of scattered rays in the y-axis direction is reduced by scattering, the intensity of X-rays to be detected is increased by using a secondary electron multiplier such as a micro channel plate MCP. It should be noted that FIG. 5 is a conceptual block diagram, and not all the shapes, dimensions, and structures are accurately drawn.

Embodiment 2 FIG. 8 shows a detector D of another embodiment of the scattered radiation tomography apparatus.
It is a figure which shows the structure of ET and the detector element DE. In the figure, II has a structure of phosphor screen-photocathode-electron lens-phosphor screen, converts weak X-rays into light on the phosphor screen, converts the light into electrons on the photocathode, and then converts the light to a focusing electrode or the like. An image intensifier for focusing and enhancing electrons by an electron lens and converting it into a visible image on the fluorescent surface on the output side, PUT is an imaging device for capturing a visible image of the image intensifier II. This detector DET converts the incident X-rays into light on the phosphor screen of the image intensifier II, converts this light into photoelectrons, then enhances the focusing by an electron lens, and forms an image on the output phosphor screen. An image pickup device PUT having a function of performing secondary electron multiplication and amplification is converted into an electric signal and output.

FIG. 9 shows the image intensifier II.
It is a figure which shows the structural example of. (A) is a sectional view of the image intensifier II, and (b) is an enlarged sectional view of a portion A of (a). (A) In the figure, AIW is an aluminum input window on which X-rays are incident, and IF is incident X.
It is an input surface that collides with lines and emits fluorescence to convert the fluorescence image into electrons. (B) The figure shows the aluminum input window AIW,
It is an enlarged view of the A section of the figure (a) including the input surface IF. In the figure, FRS ₁ is a phosphor screen that emits fluorescence upon receiving X-rays. PES is a photocathode that receives light from the fluorescent image formed on the fluorescent screen FRS ₁ and outputs photoelectrons. Input surface I
F is a phosphor screen substrate FRB, a phosphor screen FRS ₁ and a photocathode PE
It is composed of S.

Returning to FIG. 9A, FE is a focusing electrode which constitutes an electron lens for focusing the photoelectrons emitted from the photocathode PES ₁ , and FRS ₂ is a fluorescent screen which emits fluorescence by the focused photoelectrons to form a fluorescent image. is there. The fluorescent image formed on the fluorescent screen FRS ₂ is output as output light and is picked up by the image pickup device PUT.

FIG. 10 is a structural diagram of an image dissector which is an embodiment of the image pickup device PUT. In the figure, P
ES ₂ is a photocathode that receives output light from the image intensifier II and emits photoelectrons. AE is an accelerating electrode for accelerating the photoelectrons while reaching the aperture plate AP, during which the photoelectrons are focused by the focusing coil FC and deflected by the deflection coil DC to send an image for each pixel. The control signal for this deflection is input from the data acquisition device DAS. The portion from the photocathode PES ₂ to the aperture plate AP is an image portion, which is deflected by an external magnetic field by the deflection coil DC, collects photoelectrons from one point having an optical image in the hole HL of the aperture plate AP, and sends them to the amplification portion. The amplification unit includes a blanking electrode BE, a first dynode DN ₁ , a dynode group DN ₂ and an anode PL.
Composed of T. The photoelectrons that have passed through the holes HL are anodes P
Although it is attracted to the LT, it is subjected to secondary electron multiplication by the first dynode DN ₁ and the dynode group DN ₂ and output as an image signal from the anode PLT.

FIG. 11 shows the detector DE shown in FIGS.
It is a block diagram of the data collection device DAS which processes the output data of T. In the figure, AMP is an amplifier that amplifies a signal input from the image pickup device PUT, and OPA ₁ is a feedback resistor r.
An operational amplifier that forms an adder with _f and resistors R ₁ and R _2, and is the output of amplifier AMP (value proportional to voltage V ₁ ).
And the addition operation result (value proportional to the voltage V ₂ ) of the data up to immediately before being held in the sample and hold circuit SH of the subsequent stage are added, and the result is taken into the sample and hold circuit SH and stored and held. To do. OPA ₂ is an operational amplifier that forms an inverter with the feedback resistor R ₃ and the input resistor R _3, and restores the polarity of the signal whose polarity is inverted in the operational amplifier OPA ₁ . C is a sample and hold circuit S
A capacitor that holds and stores the H output. SW is a switch that is turned off during a sampling operation for fetching and storing new data in the sample and hold circuit SH, and turned on during a holding operation for storing and holding the sample and hold circuit SH. Therefore, the switch SW
Together with the capacitor C, the sample and hold circuit SH
The normal operation of the adder by the operational amplifier is maintained during the sampling operation of.

ADC is an AD converter for converting an analog signal output from the sample and hold circuit SH into a digital signal, and MM is a storage device for storing the output of the AD converter ADC.

CTL is a sample and hold circuit SH and A
A control device that controls the operations of the D converter ADC, the storage device MM, and the switch SW sends a control signal for deflecting electrons of the imaging device PUT to the imaging unit deflection control device TDC. The image pickup unit deflection control device TDC is the image pickup device PUT shown in FIG.
By controlling the deflection of the detector DET, data on an arbitrary concentric circle of the detector DET is read out in time serial.

The operation of the data collection device DAS will be described.
The output of the image pickup device PUT is amplified by the amplifier AMP and input to the operational amplifier OPA. The output of the operational amplifier OPA is held in the sample and hold circuit SH, this data is added to the output of the amplifier AMP by the data input next in the operational amplifier OPA, and the cumulative addition result is stored in the sample and hold circuit SH. To be done. When the addition of all the data on the circumference of the detector DET is completed, the data is converted into a digital signal by the AD converter ADC,
It is stored in the storage device MM. This operation is repeated for all data on the circumference of the detector DET to obtain all measurement data.

Next, the operation of the second embodiment will be described. The gantry G is moved by the table / gantry control device TGC to select a section to be imaged in the reconstruction area RA. Further, the gantry G is controlled so that the X-ray XR comes to the left end (or right end) of the reconstruction area RA.

X-ray XR is generated in the X-ray generation source XG,
A straight line x whose relation between the X-ray XR and the reconstruction area RA is parallel to the y-axis
= Scattered rays R _i from each lattice point on the x _j detectors DET
To detect.

The scattered radiation R _i guided to the detector DET is incident on the image intensifier II, and the fluorescence screen F
The light is converted into light by RS ₁ , converted into electrons by the photocathode PES ₁ , focused by the focusing electrode FE, reaches the anode PL, converted into light, and then enters the input surface of the image pickup device PUT. The incident light reaches the photocathode PES ₂ and is converted into electrons. The electrons that are converted and read one after another are the data collection device D.
The slits SL ₁ and S shown in FIGS. 3 and 4 corresponding to a group of scattered rays R _i by the imaging unit deflection control device TDC of AS.
It is based on the data obtained by scanning the points on the concentric circles of L ₂ and the detector DET one after another and reading the corresponding data on the concentric circles one after another.

The electrons are multiplied by the first dynode DN ₁ and the dynode group DN ₂ and then extracted from the anode PLT and output as data. This output data is led to the data acquisition device DAS, amplified by the amplifier AMP, and added to the addition data up to immediately before being held in the sample and hold circuit SH, and this is repeated one after another, that is, on one concentric circle. All the data are read and added one after another to obtain detection data for the scattered radiation R _i . When the addition of all the data on one concentric circle is completed, it is converted into digital data by the AD converter ADC.

In this way, for m data on each concentric circle corresponding to all grid points on one straight line parallel to the y-axis, added data of all the concentric circles is obtained, Collect detection data for all scattered rays R _i .

Next, by controlling the gantry G, the reconstruction area R
With respect to A, the generation position of the X-ray XR is moved in the positive (or negative) direction of the x axis by the sample interval d _x , and at this position, m pieces of data are collected as in the above case. This is repeated for all straight lines x = x _j and all data are collected.

The data processing device DP uses the collected data to perform various correction processes such as intensity correction of input X-rays and X-ray quality hardening correction, and then reconstructs an image. The image-reconstructed data is stored in the mass storage device AM and displayed on the image display device GDC as necessary.

As described above, according to this embodiment, X
By moving the irradiation position of the line generation source XG only in the x-axis direction, a cross-sectional image can be obtained, and it is not necessary to perform two-dimensional scanning, and the imaging time can be shortened.

In the scattered radiation tomography according to this embodiment, three-dimensional imaging can be performed as follows.
Reconstruction area RA which is a three-dimensional imaging area including the object to be measured
Is divided into a plurality of two-dimensional cross-sections, data is collected by the above-mentioned scattered radiation tomography for each two-dimensional cross-section, two-dimensional imaging is performed on the two-dimensional cross-section, and all of the divided two-dimensional cross-sections are performed. 3D imaging is obtained by performing imaging on the above and synthesizing them.

In addition to the above-described embodiments, the present invention is conceivable with the following embodiments and modifications. (1) Modification of slits The shapes of the slits SL ₁ and SL ₂ are not limited to those shown in FIG.
For example, the front and back surfaces may be curved surfaces instead of flat surfaces.

Also, although the description has been given with the example of two slits, three slits are used.
There may be one or more, and one may be provided depending on the conditions. In FIG. 3, the slits SL ₁ and SL ₂ are written with a large thickness, but a plurality of thin slits may be stacked in the X-ray passing direction, or a plurality of thin slits may be provided at intervals. It may be one installed individually.

(2) Modified Example of Measurement System As a source of pencil beam X-rays, a structure in which a collimator, an input slit, a filter and the like are inserted in an X-ray source such as an ordinary X-ray tube may be used.

The position where the slit is installed is not necessarily placed immediately before the detector, and it is not always necessary that the slit is placed immediately after the reconstruction area. Further, it may have a structure in which an X-ray shield is inserted after the X-ray generation source.

Furthermore, the structure may be such that an X-ray shield which does not interfere with the X-ray detection by the detector is inserted in front of the detector or between the subject and the detector. Further, although the X-ray XR is incident in the positive direction of the y-axis in the embodiment, it is not limited to this and the X-ray XR may be incident in any direction. The incident direction of the X-ray XR in this case is not necessarily parallel to the x-axis or the y-axis with respect to the orthogonal coordinates xy. In this case, the incident position of the X-ray XR with respect to the subject BDY (reconstruction region) is changed by moving the sample interval in the direction perpendicular to the incident direction of the X-ray XR.

(3) Modified Examples of Detector and Detector Element The shapes of the detector and detector element are not limited to those shown in FIG. For example, the front and back surfaces may be curved surfaces instead of flat surfaces.

The detectors, detector elements, and slits need not have a structure that covers the entire circumference of each concentric circle, but may be a continuous part of the circumference, or a discontinuous discrete part. It may be.

The configuration of the detector and the detector element in the embodiment is not limited to that shown in FIG. For example, a combination of a scintillator such as a fluorescent surface and a photoelectric conversion element such as a photo diode array or a semiconductor detector may be used, and further, an amplifier may be added thereto.

(4) Modification of First Embodiment In the detector shown in FIG. 5, the multi-anode structure does not have to be the structure of the entire circumference of each concentric circle, and a part of the circumference is continuous. Or may be a discontinuous discontinuous part. Further, a method of obtaining a reduced image of a two-dimensional input X-ray image may be used. For example, a structure in which a focusing electrode is provided after the fluorescent screen and the photocathode to focus photoelectrons may be used. Further, the micro channel plate may not be provided, and the micro channel plate may have not only one stage but also a multi-stage configuration.

(5) Modification of Second Embodiment The structure of the image intensifier II is not limited to that shown in FIG. For example, it does not have to be a structure for reducing a two-dimensional input X-ray image (in this case, the intensity is multiplied as an image). Further, the photoelectron image converted from the two-dimensional input X-ray image may be directly multiplied without increasing the intensity by a multiplying means such as a micro channel plate MCP, or focusing means FE forming an electron lens. Etc. may be provided with an electron multiplying means such as a micro channel plate MCP (in this case, enhancement by focusing with an electron lens and a micro channel plate MCP).
It is used together with the enhancement by electron multiplication etc.).

The structure of the image pickup device PUT is not limited to that shown in FIG. For example, the focusing and deflecting methods include combinations of electromagnetic focusing and electromagnetic deflection; electrostatic focusing and electromagnetic deflection; electromagnetic focusing and electrostatic deflection; electrostatic focusing and electrostatic deflection. Any combination may be used. ..

In addition to the image dissector of the embodiment, the image pickup device PUT includes various types such as a vidicon, a carnicon, an image orthicon, a SIT tube, and an image pickup storage tube, and any one of them is used. It doesn't matter.

The configuration of the data collecting device DAS is not limited to that shown in FIG. For example, the amplifier AMP is not always necessary. The imaging unit deflection control device TDC may be provided outside the data acquisition device DAS, for example, as an independent control device in the embodiment of FIG. Further, the configuration of the adder does not have to include the operational amplifier OPA ₁ , the feedback resistor r _f, and the resistors R ₁ and R ₂ .

For the scattered X-rays R _i obtained from the X-ray beam XR incident on x = x _j , the scanning method of the image incident on the input surface of the image pickup device PUT, that is, the input two-dimensional data surface The scanning method is not limited to concentric scanning. For example, the two-dimensional surface may be scanned linearly like a normal television. In this case, x at the top (or bottom) of the two-dimensional surface
Scan on a straight line parallel to the axis, then on a straight line parallel to the x-axis just below (or just above), and repeat for all horizontal lines.

FIG. 12 is a block diagram of the data collection device DAS in such a case. In the figure, the same parts as those in FIG. 11 are designated by the same reference numerals. Each of MM1 and MM2 is a data storage device. The operation of this device is performed as follows.

The scanning of each horizontal line is performed under the control of the imaging unit deflection control device TDC, and the data sequentially read by the scanning of each horizontal line is stored in the sequential data storage device MM1. Data on each concentric circle corresponding to FIG. 2 is sequentially read from the data storage device MM1, amplified by the amplifier AMP, added with the data held in the sample hold circuit SH, and the resulting data is added to the sample hold circuit SH. Hold, and repeat this one after another to obtain the data of the addition result of all the data on one concentric circle. The resulting data is held in the sample and hold circuit SH. The addition result of all the data on one concentric circle is converted into digital data by the AD converter ADC and then stored in the data storage device MM2.

The same reading and addition as described above is performed on the data on all the concentric circles to obtain the detected data on all the concentric circles. (6) Modification of Data Collection Device DAS The configuration of the data collection device DAS is as shown in FIG.
1, FIG. 12, but is not limited to this. For example, an amplifier (the above-mentioned amplifier, main amplifier, etc.), which is composed of a pulse circuit,
It is also possible to use a wave height analyzer (or wave height discriminator), a counting circuit, or the like.

In order to measure the light converted from X-rays with high sensitivity, the photon counting method is used to identify the peak value by the wave height discriminator, and in the measurement of extremely weak light, noise or stray light is detected. To remove incident light by turning on and off the incident light with a chopper and subtracting the off count value from the on count value (synchronous counting method; examples of this configuration include a chopper, an amplifier, a wave height discriminator, A subtractor with a memory, an LED, a phototransistor or the like for generating a synchronizing signal) may be employed. (7) Deformation of data collection and image reconstruction by scanning When the scattering angle θ in Fig. 2 is very small, tan θ becomes a very small value, which reduces the size of the detector element and the detection system. It is necessary to set the opening width very small.
The detector and the detector element of the present embodiment are (see FIGS. 5 and 8 to 10).
Etc.) It has a configuration that can sufficiently cope with that point. However, when the realization is difficult due to the configuration of the apparatus and the measurement conditions (in such a case, the resolving power in the y direction of the reconstruction area RA in FIG. 2 is considerably deteriorated as compared with the resolving power in the x direction). The image is reconstructed by a normal scan in the direction described in the example to reconstruct the image (this is called direct mode scatter tomography) and the subject BDY (reconstruction area)
The same measurement as in the example is performed by rotating only the measurement direction by 90 degrees while fixing the X-ray (measured by irradiating the X-ray XR from the positive direction of the x-axis, and measuring the X-ray XR in the y-direction of the subject). Repeat the measurement by moving the sample interval d _y to the sample, and do this for all straight lines y = y _i to collect all data) and perform image reconstruction from these data (this direct mode scatter tomography). -In the image, the resolution in the x direction is much worse than that in the y direction). Thus, these two images are used to improve the resolution in each direction by the statistical calculation process. (This is called reconstruction mode scattering tomography).

An example of this calculation will be described below. The image 1 of direct mode scattering tomography is an image in which the resolving power in the y direction is deteriorated, and a substantial (meaningful) sample interval dx in the x direction and a substantially (meaningful) sample interval dy in the y direction ( dy = n · dx, n >> 1) Assume that measurement and image reconstruction have been performed. The image 2 of the direct mode scattering tomography is an image in which the resolving power in the x direction is deteriorated, and the substantial sample interval dx ′ in the x direction and the substantial sample interval dy ′ in the y direction (dx ′ = n · dy ′). ，
n >> 1) It is assumed that measurement and image reconstruction have been performed.
For the same portion of these two images, the image data of image 1 is a _i (i = 1, 2, ..., N) and the image data of image 2 is b _j (j = 1, 2, ..., N). To do. At this time, the image data represented by s _ij is obtained as follows as an image having the same resolution in the x and y directions.

[0072]

[Equation 1]

(8) Three-dimensional imaging area R including the object to be measured
A is divided into a plurality of two-dimensional cross sections, and for each two-dimensional cross section,
As described in the operation of the above-described embodiment, the data is collected, the two-dimensional imaging is performed on the cross section, and the imaging is performed on all the two-dimensional cross sections, so that the three-dimensional imaging of the measured object can be performed. it can.

[0074]

As described in detail above, according to the present invention, it is a characteristic common to scattered ray tomography or obtained by scattered ray tomography: imaging and imaging of only the required local area can be performed ( There is a possibility of so-called real-time imaging that obtains an image at the same time as shooting (possible real-time imaging of the heart, etc.), and it is possible to shoot and image a cross section in any direction ( Resolving power can be increased equally in arbitrary directions), and it has great features not present in CT, such as the possibility of identifying substances or tissues,
In addition, conventional two-dimensional imaging can be done by one-dimensional imaging as compared with conventional scattered radiation tomography, so the imaging time can be made extremely short (1 / (Equation 10) ~
1 / (number 1000)).

Moreover, by changing the conventional two-dimensional scanning of the subject to one-dimensional scanning, the radiation dose to the subject can be extremely reduced (1 / (Equation 10)- 1 / (number 1000)).

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of a photographing system according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of the structure of a slit used in the apparatus of the embodiment.

FIG. 4 is a diagram showing an example of the shape of a detector used in the apparatus of the embodiment.

5 is a diagram showing the structure of an example of the detector and detector elements of FIG.

6A and 6B are views showing the structure of a micro channel plate used in the detector of FIG. 5 and its action.

FIG. 7 shows an electrical circuit associated with a micro channel plate.

FIG. 8 is a block diagram of an example of a detector and a detector element used in the apparatus of another embodiment of the present invention.

9 is a structural diagram of an example of the image intensifier shown in FIG.

10 is a structural diagram of an image dissector of the example of the image pickup apparatus shown in FIG.

FIG. 11 is a block diagram of an embodiment of a data collection device.

FIG. 12 is a block diagram of another embodiment of the data collection device.

[Explanation of symbols]

DAS data acquisition device DC deflection coil DE _i detector element DET detector DN dynode DP data processing device FE focusing electrode FRS phosphor screen G gantry II image intensifier MAN multi-anode MCP micro channel plate PES photocathode PUT imaging Equipment RA Reconstruction area _Ri Scattered ray SL Slit TA table TGC table Gantry controller XG X-ray source XR X-ray beam

Claims (7)

[Claims] 1. A pencil-beam-shaped radiation (XR) is incident on an object to be measured, and the radiation scattered by a plurality of discrete points on a straight line of the incident path is converted into the beam-shaped radiation (XR).
R) has a shape that forms a concentric circle or a part of a concentric circle in a plane perpendicular to the traveling direction of the slit (SL ₁ , SL ₁ having a certain angle with respect to the traveling direction of the beam-like radiation (XR)). A plurality of scattered radiations extracted at the same time by the SL ₂ ) and discretized are extracted from the slits (SL).
₁ , SL ₂ ) and a plurality of detector elements (D
Scattered tomography, wherein data is collected by detecting with E _i ), and the measured object is imaged by scattered radiation using the collected data. 2. A x- and y-coordinate is taken on a two-dimensional cross section of a reconstruction area (RA) including a subject, and pencil beam-like radiation (XR) is a straight line x parallel to the y-axis from one direction of the y-axis. = X
Radiation which is incident on _j and scattered from each of a plurality of discrete coordinate points on the straight line is detected by the method according to claim 1 to collect data, and the incident position of the radiation beam (XR) is detected. Relative to the reconstruction area (RA), and the scattered radiation (R _i ) for each radiation beam (XR) incident on all the straight lines x = x _j parallel to the y-axis, A scattered radiation tomography characterized by performing detection of data by detecting with a detector element (DE _i ) and using the collected data to perform two-dimensional imaging of an object to be measured with scattered radiation (R _i ). 3. A three-dimensional reconstruction area (R) including an object to be measured.
A) is divided into a plurality of two-dimensional cross-sections, data is collected for each two-dimensional cross-section by the method according to claim 2, and then two-dimensional imaging is performed on the two-dimensional cross-section. Scattered-ray tomography, wherein three-dimensional imaging of an object to be measured is performed by performing the above two-dimensional cross-section. 4. A table (T for storing an object to be measured)
A) and radiation source (XG) and detector (DE) for measurement
Gantry (G) having T) and the table (T)
A) a gantry controller (TGC) that controls the operations of the gantry (G), a data acquisition device (DAS) that acquires data, and a data processing device (DP) that processes data and performs image reconstruction. In the scattered radiation tomography apparatus having: a radiation source (XG), an object to be measured is irradiated, and at least a radiation for scattering at a constant angle is selected to pass radiation scattered on a transmission path thereof. and at least one slit having a shape forming a part of concentric circles (SL _1, SL _2), has the slits (SL _1, SL ₂₎ equivalent shape, the slits (SL _1, SL ₂₎ a detector element in a position capable of detecting the radiation which has passed through (DE _i) detector with (DET), the data collection for collecting the data detected by the detectors (DET) Scattered radiation tomography apparatus characterized by comprising a location (DAS). 5. Detector (DET) and detector element (D)
E _i ) is a phosphor screen (F which converts incident radiation into light)
RS), a photocathode (PES) for converting light by a fluorescent image bound to the phosphor screen (FRS) into electrons, and the photocathode (PE)
S) from a micro-channel plate (MCP) that multiplies the electrons emitted from it and a plurality of multi-anodes (MAN) whose geometry of the arrangement to collect the multiplied electrons is at least part of a concentric circle The scattered radiation tomography apparatus according to claim 4, wherein the scattered radiation tomography apparatus is configured. 6. Detector (DET) and detector element (D)
E_i) Is the first fluorescence that converts incident radiation into light
Face (FRS₁) And the first phosphor screen (FRS₁)
The first photocathode (PE that converts light from the fluorescent image into electrons)
S₁) And the first photocathode (PES₁) Is emitted from
Focusing means (FE) forming an electron lens for focusing electrons
And electric power such as Micro Channel Plate (MCP)
And one of the means for multiplying
The second fluorescent screen (F
RS₂) And an image intensifier (I
I) and incident from the image intensifier (II)
Second photocathode (PES) for converting light into electrons₂) And the
Second photocathode (PES₂) Output electrons of focusing means (F
C) and deflecting means (DC) to scan, and if necessary, electronic
Multiplier (DN ₁, DN₂) Image pickup device
And (PUT).
The scattered ray tomography device described. 7. An image intensifier (II)
Comprises a focusing means (FE) forming an electron lens for focusing the electrons emitted from the _first photocathode (PES ₁ ) and an electron multiplying means such as a micro channel plate (MCP). 7. A scattered radiation tomography apparatus according to claim 6, wherein: