JPH06233757A - Three-dimensional photographing device - Google Patents

Abstract

PURPOSE:To provide the three-dimensional photographing device exactly obtaining three-dimensional distribution concerning the X-ray absorption coefficients of an object at high speed. CONSTITUTION:An X-ray irradiating means 1 irradiates the object with parallel X rays 12, a two-dimensional detecting means 2 detects the two-dimensional intensity distribution of transmitted X rays 13, a projecting direction changing means 3 changes a direction (projecting direction) for the X rays to transmit the object, and a three-dimensional image reconstituting means 4 successively fetches the detected results. According to the request of photographing start from an operator, a photographing control means 5 performs X-ray irradiation and detection while generating control signals to the respective means and changing the projecting direction. Next, the three-dimensional distribution of X-ray absorption coefficients of the object 11 is led out from the detected results collected by the three-dimensional image reconstituting means 4, and displayed by a three-dimensional image display means 6. Thus, the reconstituting algorithm of conventional X-ray CT can be applied, the influence of noise at the time of measurement can be reduced, and high accuracy and high resolution can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional image pickup apparatus for measuring the three-dimensional distribution of X-ray absorption coefficient of a subject.

[0002]

2. Description of the Related Art Conventionally, for example, an X-ray absorption coefficient of 3
Medical Imaging Technology (MEDICAL IMAGING TECHNOLOGY) is a method to measure the dimensional distribution.
8, 4 (1990), pneumoconiosis X-ray CT images described on pages 414 to 422 were used. This is the human body X
The three-dimensional distribution of the linear absorption coefficient is measured, and the distribution of the X-ray absorption coefficient on the cross section perpendicular to the body axis is measured over a plurality of cross sections, and the obtained measurement results are accumulated to obtain the three-dimensional distribution. . Medical Imaging Technology (MEDICAL IMAGING TECHNOLOGY) 10, 3 (1992) pp. 269 to 270 uses an X-ray source with a conical irradiation shape, and X-rays from the X-ray source can be emitted in multiple directions. Describes a method of irradiating a subject from the object and measuring a three-dimensional distribution of the X-ray absorption coefficient of the subject from the intensity distribution of the X-ray transmitted through the subject. This method requires so-called reconstruction, which derives a three-dimensional distribution of X-ray absorption coefficients from the intensity distribution of X-rays that have passed through the subject. As this reconstruction algorithm, a method in which the filtered backprojection method for fan (fan-shaped) beam projection is extended to cone (conical) beam projection for a three-dimensional object is used. Also, IEICE Transactions J72-D-II, 9 (1989) No. 1
Also from page 534 to page 1542, a method using an X-ray source whose irradiation shape is also conical is described, and by adding a limiting condition to the reconstruction algorithm, artifacts that occur during reconstruction are reduced. is doing. further,
Technical Report of IEICE Technical Report, Vol. 84, No. 1.
No. 06 (1984), pp. 73-80, parallel X
A reconstruction method using a line to obtain a three-dimensional distribution of the X-ray absorption coefficient inside the subject from the two-dimensional intensity distribution of the X-ray that has basically transmitted through one subject has been studied.

[0003]

In the above-mentioned conventional method, since the measurement results of the X-ray absorption coefficient distributions of a plurality of cross sections are accumulated, there is a problem that it is difficult to perform the measurement at high speed. Further, since the measurement time is different for each cross section, there is a problem that it is difficult to associate the cross sections due to the movement of the subject. In the above conventional method,
Efficient measurement, which is important when actually diagnosing a patient in a hospital or the like, has not been studied at all, and development of an efficient measurement control procedure has been earnestly desired. Further, when attempting to reduce the artifacts that occur during reconstruction, there is a problem that, conversely, it is susceptible to external factors such as noise during measurement. Two X-rays transmitted through one subject
The conventional reconstruction method for obtaining the three-dimensional distribution of the X-ray absorption coefficient inside the subject from the three-dimensional intensity distribution is difficult to obtain the X-ray absorption coefficient with high accuracy and is difficult to use as a practical reconstruction method. There was a problem. An object of the present invention is to solve such conventional problems and to provide a three-dimensional imaging method and apparatus capable of measuring the three-dimensional distribution of the X-ray absorption coefficient of a subject quickly, accurately and easily. is there.

[0004]

A three-dimensional imaging apparatus of the present invention comprises parallel X-ray irradiating means for irradiating a subject with parallel X-rays.
A two-dimensional detecting means for detecting a two-dimensional intensity distribution of transmitted X-rays transmitted through the subject; a projection direction changing means for irradiating the subject with parallel X-rays to change a projection direction for obtaining a two-dimensional intensity distribution of the transmitted X-rays; It is characterized by having a three-dimensional image reconstructing means for reconstructing a three-dimensional distribution of the X-ray absorption coefficient of the subject based on the two-dimensional intensity distributions in a plurality of projection directions. In addition, according to the operator's instruction to start three-dimensional imaging, the parallel X-ray irradiating means irradiates the parallel X-rays, the two-dimensional detecting means detects the transmitted X-rays, and the projection direction changing means. It is also characterized in that it has an imaging control means capable of controlling at least the timing of changing the projection direction of the image and the timing of reconstructing the three-dimensional distribution by the three-dimensional image reconstructing means.

[0005]

According to the above construction, a three-dimensional distribution of the X-ray absorption coefficient of the object can be obtained by simply measuring the intensity distribution of the transmitted X-ray while changing the projection direction to a plurality of directions, and the photographing speed is increased. Therefore, it is possible to significantly reduce the influence of the movement of the subject during shooting. Further, according to the above configuration, the parallel X-ray irradiation unit, the two-dimensional detection unit, the projection direction changing unit, and the three-dimensional image reconstructing unit can operate in synchronization with each other in response to an operator's request to start imaging. Is, for example,
3D imaging can be performed only by operating the push button switch, and complicated operations are not required, so that the measurement time can be shortened and the throughput can be dramatically improved. Further, according to the above configuration, since the parallel X-ray beam is emitted, the conventional X-ray CT is used.
Reconstruction calculation using the reconstruction algorithm is possible, and it is possible to solve the conventional problem that external factors such as noise during measurement are easily received in the calculation process of reconstruction calculation.
By image reconstruction, the X-ray absorption coefficient can be obtained with extremely high accuracy and high resolution. Further, according to the above configuration, since the two-dimensional intensity distribution of a plurality of transmitted X-rays having different projection directions is used, the conventional practical image reconstruction algorithm can be used, and the high image quality equivalent to that of the conventional line CT can be obtained. Images can be obtained at high speed.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing the basic configuration of the present embodiment. Details of the X-ray irradiating means 1 capable of irradiating the subject 11 with the parallel X-rays 12 will be described later. Subject 1
The two-dimensional detection means 2 for two-dimensionally detecting the intensity distribution of the transmitted X-rays 13 which are X-rays transmitted through 1 is, for example, an X-ray light conversion means for converting X-rays into visible light and an electric signal for visible light. It is configured by combining with a photoelectric conversion means for converting into. The X-ray light converting means can be constituted by a fluorescent screen, an X-ray image intensifier, etc., and the photoelectric converting means can be constituted by an image pickup tube having a predetermined appropriate spatial resolution, a TV camera using a CCD, or the like. It is possible to change the projection direction, which is the direction in which the X-rays 12 emitted from the X-ray emission means 1 pass through the subject 11 and can be detected by the two-dimensional detection means 2, and the X-rays 12 pass through the subject 11. The projection direction changing means 3 has a configuration as shown in FIG. 2, for example.
In FIG. 2, the X-ray tube 21, the X-ray image intensifier 22 and the TV camera 23 have a rotating ring 24 on which the X-ray irradiation surface of the X-ray tube 21 and the light-receiving surface of the X-ray image intensifier 22 are arranged. Oppositely, each is fixed on a straight line passing through the center of the rotary ring 24. Electric motor 25
Rotates the rotary ring 24 in the direction indicated by 26. When the operation of the electric motor 25 starts, the rotary ring 24 rotates, and X
Since the X-ray tube 21, the X-ray image intensifier 22, and the TV camera 23 rotate on the circumference of a circle that includes the subject inside, the direction (projection direction) in which the X-ray passes through the subject 11 can be changed. . The three-dimensional image reconstructing means 4 for reconstructing the three-dimensional distribution of the X-ray absorption coefficient of the subject 11 based on the intensity distributions of a plurality of transmitted X-rays collected while changing the projection direction by the projection direction changing means 3. For example, it is composed of an interface for inputting the detection result of the two-dimensional detection means 2, an arithmetic element such as a multiplier for arithmetically processing the detection result, or a microprocessor. According to the operator's instruction to start the three-dimensional imaging, the X-ray irradiation means 1, the two-dimensional detection means 2,
The imaging control means 5 for controlling each operation timing of the projection direction detecting means 3 and the three-dimensional image reconstructing means 4 is composed of, for example, a crystal transmitting element that generates a reference signal for timing determination, a logic element such as TTL, or the like. . The three-dimensional image display means 6 for displaying the three-dimensional distribution of the X-ray absorption coefficient of the subject 11 in a visually recognizable form is, for example, a display such as a CRT having an image processing function of converting pixel values into gray values. It is composed of devices.

Next, an example of the structure of the X-ray irradiation means 11 will be described with reference to FIG. The X-ray generating means 7 for generating X-rays while changing the generation position thereof emits X-rays by collision of the cathode 41 emitting thermoelectrons and the thermoelectrons emitted from the cathode 41 as shown in FIG. It is composed of a target 42 to be generated and a deflecting means 43 for changing the direction of thermoelectrons. The deflecting means 43, for example, prepares two sets of two electrodes facing each other (44 and 45, 46 and 47), arranges them so as to be orthogonal to each other, and potential difference (deflection signal) between the electrodes.
Is given to change the direction of the thermoelectrons. X-ray generation means 7
Solar slit 8 that controls the direction of X-rays generated in
Has, for example, a structure in which columnar cylinders having a dimension in the height direction 52 that is sufficiently larger than the side dimension of the square cross section 51 are stacked in the vertical and horizontal directions, and X-rays are transmitted only in the height direction 52. It is a slit. As the material of the slit, for example,
Tungsten, tantalum, platinum alloy, etc. are used. 4, when a positive potential difference is applied to the target 42 with respect to the target 42, the thermoelectrons emitted from the cathode 41 collide with the target 42 through a locus shown by 48 in the figure, for example. Here, the trajectory is changed by the deflecting means 43 on the way. When the thermal electrons collide, for example, X-rays that draw the loci shown by 49 and 50 in the figure are emitted. Its radial shape is a cone. The emitted X-rays pass through the solar slit 8 and the solar slit 8 is
X-rays in this direction are transmitted because only X-rays in this direction are transmitted.
Only get. The parallelism of X-rays is determined by the slit spacing of the solar slits, the depth length of the slits, and the distance from the X-ray source. In the present embodiment, for example, the above-mentioned slit spacing is set so that the irradiation size of X-rays transmitted through each columnar cylinder forming the solar slit on the two-dimensional detector is equal to or smaller than the size of one pixel of the detector, Depth length, distance from X-ray is determined. Next, when the deflection signal of the deflecting means 43 is changed, the locus of the thermoelectrons from the cathode 41 to the target 42 changes, so that the position on the target where the thermoelectrons 48 collide changes. Therefore, the position of the X-ray 50 obtained by passing through the solar slit 8 changes according to the deflection signal. By controlling the deflection signal so that the thermionic electrons 48 evenly collide with the target 42, 5 in FIG.
It is possible to irradiate X-rays in only two directions, that is, multiple parallel plane X-ray beams. The deflection signal of the deflection means in the X-ray generation means is given using, for example, a deflection control means for generating a deflection signal synchronized with the X-ray irradiation signal from the imaging control means as shown in FIG. The X-ray irradiation signal is a signal for controlling the irradiation of X-rays, and each signal is expressed by positive logic. Details will be described later. In FIG. 6, the X-deflection signal 6 which is the potential difference applied between the electrodes 44 and 45.
The Y-deflection signal 62, which is the potential difference applied between the first electrode 46 and the second electrode 47, is synchronized with the X-ray irradiation signal 34 from the imaging control means. When the X-deflection signal 61 and the Y-deflection signal 62 are applied, the thermoelectrons scan the Y-direction once while zigzag-scanning the X-direction on the target surface, and collide with the target evenly.

Next, an example of a three-dimensional photographing procedure based on this embodiment will be described with reference to FIG. FIG. 3 is a timing chart for explaining an example of control by the photographing control means. Each timing is a positive logic, and hereinafter, the high level is represented by H and the low level is represented by L. First, the operator requests the photographing control means 5 to start rotation of the rotary ring 24 of the projection direction changing means 3. This request is made, for example, by the operator selecting a push button switch or the like provided in the photographing control means 5, and the photographing control means 5 sends a rotation start signal 31 to the projection direction changing means 3. The operator's request is set by selecting a push button switch, a dial switch or the like provided in the photographing control means 5 at a position corresponding to a desired request not only in the present embodiment but also in the embodiments described below. To be done. The projection direction changing means 3 that has received the rotation start signal 31
The electric motor 25 is operated to rotate the rotating ring 24.
When the rotation speed reaches a predetermined value, the projection direction changing means 3
Sends a rotation completion signal 32 to the photographing control means 5. Upon receiving the rotation completion signal 32, the imaging control means 5 notifies the operator that the rotation is completed, for example, by turning on a lamp. Therefore, the operator requests the shooting control means 5 to start shooting, for example, via a push button switch or the like. The shooting start signal 33 represents this request on the timing diagram. Upon receiving the request to start shooting, the shooting control means 5
The X-ray irradiation signal 34 is sent to the X-ray irradiation means 1. This signal is generated in synchronization with the detection synchronization signal 35. The detection synchronization signal 35 is a signal representing the detection timing of the transmitted X-rays by the two-dimensional detection means 2, and corresponds to, for example, a synchronization signal of a TV camera. When the detection synchronization signal 35 is H, it corresponds to the data reading period, and when it is L, it corresponds to the blanking period. The detection synchronization signal 35 is a signal which is generated by the two-dimensional detection means 2 or the photographing control means 5 and which synchronizes the two. The X-ray irradiation signal 34 is a pulse signal that becomes H when the detection synchronization signal 35 is L, and generates a number of pulses in a predetermined predetermined projection direction (180 projections in the figure). Further, the photographing control means 5 that has received the request to start photographing
Sends the detection valid signal 36 to the three-dimensional image reconstructing means 4.
This signal is a signal that becomes H during the period in which the two-dimensional detection unit 2 detects the transmitted X-rays by a series of X-rays (180 projections in the drawing) that are emitted in response to the request to start imaging. Upon receiving the X-ray irradiation signal 34, the X-ray irradiation means 1 irradiates the subject 11 with X-rays when the X-ray irradiation signal 34 is H.
Further, the three-dimensional image reconstructing means 4 which has received the detection valid signal 36
Sequentially takes in the two-dimensional intensity distribution of the transmitted X-ray detected by the two-dimensional detection means 2. Therefore, the X-ray irradiation according to the X-ray irradiation signal 34 and the detection synchronization signal 3 in the two-dimensional detector 2 are performed.
The detection of the transmitted X-ray according to 5 and the capturing of the detection result by the three-dimensional image reconstructing unit 4 are repeated for the number of predetermined projection directions.

Next, the three-dimensional image reconstructing means 4 takes in the two-dimensional intensity distributions of the transmitted X-rays in all projection directions, and then performs a reconstruction operation for obtaining the three-dimensional distribution of the X-ray absorption coefficient of the subject 11. To do. As described below, the reconstruction algorithm used in the conventional X-ray CT can be applied to this calculation. The two-dimensional intensity distribution of the transmitted X-rays used for the reconstruction calculation rotates the position of the irradiation surface on which the X-ray irradiation means irradiates the X-rays and the position of the light-receiving surface on which the two-dimensional detector detects the X-rays. While detecting. Considering a plane perpendicular to the central axis of this rotation, when a multiple parallel plane X-ray beam is used, X-rays transmitted through an object in this plane are emitted from the same plane and detected in the same plane. To be done. That is, the conventional X
Since the data acquisition method is exactly the same as that for the line CT, image reconstruction can be performed by applying the reconstruction algorithm used in the conventional X-ray CT. Such a reconstruction algorithm is discussed in, for example, Hirokazu Kimura, Recent Medical Image Diagnostic Equipment, pages 106 to 110. Finally, the result of reconstruction by the three-dimensional image reconstruction means 4 is sent to the three-dimensional image display means and displayed in a form that can be visually recognized by the operator. This display can be performed by, for example, a method of extracting an X-ray absorption coefficient along a certain cross section and displaying the value as a gray value (cross section display).
Alternatively, it can be performed by a method (surface display) in which a portion having the same coefficient is extracted, treated as an object, and subjected to a hidden surface processing, a shading processing, or the like to display the shape. By the above three-dimensional imaging procedure, the three-dimensional distribution of the X-ray absorption coefficient of the subject 11 can be obtained and displayed.

As described above, in this embodiment, the conventional X-ray C is used.
The reconstruction algorithm used in T can be applied, and the conventional problem of being susceptible to external factors such as noise during measurement can be avoided in the calculation process of the reconstruction calculation, and the result of image reconstruction can be obtained. High accuracy and high resolution of the X-ray absorption coefficient can be achieved. Also, since the three-dimensional distribution of the X-ray absorption coefficient of the subject can be obtained by rotating the rotating ring once or an appropriate number of times, the photographing speed can be increased, and the influence of the movement of the subject during the photographing can be achieved. Can be significantly reduced. The X-ray irradiation means, the two-dimensional detection means, the projection direction changing means, and the three-dimensional image reconstructing means operate in synchronization in response to an operator's request to start imaging, so that the operator operates, for example, a push button switch. It is possible to perform three-dimensional imaging only by itself, eliminate the need for complicated operations, and improve the measurement efficiency. Further, since the X-ray irradiation can be performed during the blanking period of the TV camera, it is possible to avoid the problem that the detection target changes during the detection of the transmitted X-ray in the two-dimensional detector and the intensity distribution cannot be accurately detected. In the X-ray generation means, the thermoelectrons 48 evenly collide with the target 42, so that partial deterioration of the target can be reduced and the life can be extended. The deflection signal of the deflection means in the X-ray generation means is synchronized with the X-ray irradiation signal from the imaging control means, and the collision of thermoelectrons with the target always occurs under the same condition for one X-ray irradiation. By doing so, the two-dimensional intensity distribution of the multiple parallel plane X-ray beams emitted from the X-ray irradiating means can be kept constant, and the X-ray absorption coefficient obtained as a result of image reconstruction can be made highly accurate and have high resolution. Can be achieved.

In the present embodiment, the three-dimensional image reconstruction means 4
The reconstruction calculation in step S1 is performed after capturing the two-dimensional intensity distribution of the transmitted X-rays in all the projection directions. For example, a process that can be executed in a unit of the two-dimensional intensity distribution of the transmitted X-rays such as shading correction. Regarding the above, it can be performed in parallel with the acquisition of the two-dimensional intensity distribution of the transmitted X-rays, and in this case, the calculation speed can be increased. Further, in the present embodiment, the rotation of the rotary ring that determines the projection direction by the projection direction changing unit can be synchronized with the detection synchronization signal by the imaging control unit, and, for example, drives an electric motor that rotates the rotary ring. This can be realized by adding a function of adjusting a signal by a circuit such as a PLL (Phase Locked Loop) so that the frequency ratio and the phase difference become constant with respect to the detection synchronization signal. As a result, the projection direction can be changed more accurately, and the X-ray absorption coefficient obtained as a result of image reconstruction can be highly accurate and have high resolution. In this embodiment, the projection direction deflecting means using the rotating ring as shown in FIG. 2 is used, but the method by other means as shown in FIG. 5 may be used.

In FIG. 5, the X-ray tube 21, the X-ray image intensifier 22 and the TV camera 23 are arranged on the bow arm 55 on the X-ray irradiation surface of the X-ray tube 21 and the X-ray image.
The light receiving surface of the intensifier 22 faces and is fixed. Further, the electric motor 53 moves the bow-shaped arm 55 in the direction indicated by 54, and the electric motor 51 causes the electric motor 53 and the bow-shaped arm 5 to move.
5 is rotated in the direction indicated by 52. By starting the operation of the electric motor 51, the bow-shaped arm 55 rotates, and the X-ray tube 21, the X-ray image intensifier 22, and the TV camera 23.
Rotates on the circumference of a circle that includes the subject inside, so that the direction in which X-rays pass through the subject 11 (projection direction) can be changed, as in the example of FIG. Further, when the electric motor 53 is operated, the bow-shaped arm moves, and the changeable projection direction can be changed by the operation of the electric motor 51. Therefore, the imaging region can be changed without moving the subject. In the present embodiment, the deflection control means synchronizes the deflection signal of the deflection means in the X-ray generation means with the X-ray irradiation signal from the imaging control means. For example, the X-deflection signal and the Y-deflection signal are used. The signal repetition period can be made sufficiently shorter than the pulse width of the X-ray irradiation signal, and this synchronization function can be omitted. Further, in the present embodiment, as the deflection means in the X-ray generation means, so-called electrostatic deflection, which changes the direction of thermoelectrons by an electric field, is used, but electromagnetic deflection, which is changed by a magnetic field, is used.
Alternatively, both can be used together. Further, in the present embodiment, the X-ray generation means changes the X-ray generation position by the deflection means, but as another method, a method of changing the size (large focus, small focus) of the X-ray tube, or It is also possible to arrange a plurality of X-ray tubes and switch the X-ray tubes for irradiation, or to use these methods together. In the present embodiment, the multiple parallel plane X-ray beam is generated by the method shown in FIG. 4, but as another method, it is also possible to generate it by using a multilayer film concave mirror as shown in FIG. In FIG. 7, X generated from the X-ray tube 21
The line passes through a locus indicated by 64 in the figure, and is incident on the multilayer concave mirror 63. The multilayer concave mirror 63 reflects incident X-rays, but the reflection angle differs depending on the incident position.
The reflected X-rays become a multiple parallel plane X-ray beam like the locus shown by 65 in the figure. Therefore, the object is irradiated with the multiple parallel plane X-ray beams obtained by being reflected by the multilayer film concave mirror 63, and the three-dimensional distribution of the X-ray absorption coefficient of the object is obtained by the same procedure as in this embodiment.

(Second Embodiment) Next, a second embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, a multiple parallel plane X-ray beam composed of sheet-like X-ray beams parallel to each other was used, but a plurality of fan-shaped X-ray beams parallel to each other are used.
It is also possible to use a multiple fan-shaped planar X-ray beam consisting of a line beam. FIG. 8 shows an example of the configuration of the X-ray irradiation means of this embodiment. The X-ray generation means for generating X-rays while changing the position of generation of X-rays emits X-rays by collision of the cathode 41 emitting thermoelectrons and the thermoelectrons emitted from the cathode 41 as shown in the figure, for example. It is composed of a target 71 to be generated and a deflecting means 72 capable of changing the direction of thermoelectrons. The deflecting means 72 prepares, for example, a pair of facing two electrodes (73 and 74), gives a potential difference (deflection signal) between the electrodes to generate an electric field, and changes the direction of thermoelectrons. Unlike the case of the first embodiment, since there is one set of electrodes, the direction of thermoelectrons can be changed in only one direction. 10 is a solar slit 10 for controlling the direction of X-rays generated by the X-ray generation means 9.
Has, for example, a structure in which columnar cylinders having a dimension in the height direction 79 that is sufficiently larger than the longitudinal dimension of a rectangular cross section 78 that is sufficiently longer in the lateral direction than the longitudinal direction are vertically stacked, and the height thereof is It is a slit that transmits only X-rays that spread in a fan shape in the direction 79. As the material of the slit, for example, tungsten,
Tantalum, platinum alloy, etc. are used. In FIG. 8, when a positive potential difference is applied to the target 41 with respect to the target 71, the thermoelectrons emitted from the cathode 41 collide with the target 71 through a locus indicated by 75 in the figure, for example. Here, the trajectory is changed by the deflecting means 72 on the way. When the thermoelectrons collide, for example, X-rays that draw the loci denoted by 76 and 77 in the figure are emitted, and the emission shape becomes a conical shape. The emitted X-rays pass through the solar slit 10, but the solar slit 10 transmits only X-rays that spread in a fan shape in the direction of 79, so that only X-rays 77 are obtained. Next, when the deflection signal of the deflection means 72 is changed,
Since the trajectory of the thermoelectrons from the cathode 41 to the target 71 changes, the position on the target where the thermoelectrons 75 collide changes, and the position of the X-ray 77 obtained by passing through the solar slit 10 depends on the deflection signal. Change. The deflection signal is controlled so that the thermoelectrons 75 uniformly collide with the target 71, and the X-ray spreads in a fan shape in the direction of 79 in the figure.
That is, multiple fan-shaped plane X-ray beams can be emitted. A three-dimensional distribution of the X-ray absorption coefficient of the subject 11 can be obtained by using the means capable of irradiating the multiple fan-shaped plane X-ray beams by the same procedure as in the first embodiment. Three-dimensional image reconstruction means 4
The reconstruction calculation in the same manner as in the first embodiment (multiple parallel plane X-ray beam) is performed by the conventional X-ray CT (fan beam C).
The reconstruction algorithm used in T) can be applied. Further, regarding the deflection signal of the deflection means in the X-ray generation means, as in the first embodiment, the deflection control for generating the deflection signal synchronized with the X-ray irradiation signal from the imaging control means as shown in FIG. Means can be added. However, there is one set of electrodes, and only the Y-change signal is used.

As described above, in the present embodiment, the deflection direction of the thermoelectrons of the deflection means of the X-ray generation means is only one direction, the structure of the deflection control means can be simplified, and the reliability and cost can be reduced. Can be achieved. Further, the structure of the solar slit is a structure that can be easily manufactured, and high reliability and low cost can be achieved. Also in this embodiment, as in the case of the first embodiment, it is possible to generate a multiple fan-shaped plane X-ray beam by using a multilayer film concave mirror as shown in FIG. In FIG. 9, X generated from the X-ray tube 21
For example, the line passes through the locus indicated by 82 in the figure and enters the multilayer concave mirror 81. The multilayer film concave mirror 81 reflects incident X-rays, but its reflection angle differs depending on the incident position.
The reflected X-rays become a multiple fan-shaped planar X-ray beam having a locus indicated by 83 in the figure. A multiple parallel plane X-ray beam obtained by being reflected by the multilayer concave mirror 81 is applied to the subject, and a three-dimensional distribution of the X-ray absorption coefficient of the subject is obtained by the same procedure as in this embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described in detail. In each of the above-described embodiments, the projection direction is set to a predetermined number (180 projections in the example of FIG. 2).
Although the three-dimensional distribution of the X-ray absorption coefficient of the subject was obtained using the two-dimensional intensity distribution of the transmitted X-rays collected while changing, the number of projection directions to be collected can be changed according to the imaging conditions required by the operator. It is also possible to provide a means for changing the number of projections.
The projection number changing unit changes the number of projection directions to be collected per image capturing, and changes the speed of the rotating ring 24 in the projection direction changing unit shown in FIG. 2, for example. Alternatively, when the rotating ring 24 is rotated a plurality of times to collect data in all projection directions, the number of times of this rotation is changed. For example, when the operator requests high-speed imaging, the projection number changing means reduces the intervals in the projection direction to be collected and reduces the number of projections to 90 projections, 60 projections, or the like.
If the number of projections is reduced, the time required for data collection itself can be shortened.
The speed of 4 can be increased to shorten the shooting time. When the projection direction is reduced, an artifact may occur during the reconstruction calculation by the three-dimensional image reconstruction means. Such optimization that can be avoided by optimizing the reconstruction algorithm is described in, for example, Optec. Letters (OPTICS LE
TTERS) 14, 20 (1989) pp. 1095-1097. In addition, when the operator requests high-definition imaging, the projection number changing unit makes the intervals in the projection direction to be collected fine, and the number of projections is set to, for example, 3.
Increase to 60 or 480 projections. The increase in the number of projections improves the accuracy of the reconstruction calculation by the three-dimensional image reconstructing means, and a more precise three-dimensional distribution of the X-ray absorption coefficient can be obtained. As described above, in the present embodiment, since the projection number changing unit that can change the number of projection directions to be collected is provided according to the shooting condition requested by the operator, high-speed shooting or high-definition shooting can be performed according to the operator's request. It can be performed.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described in detail. In each of the above-described embodiments, the two-dimensional detection means detects the transmitted X-rays that have passed through the subject with a predetermined spatial resolution, but the spatial resolution that changes this spatial resolution according to the imaging conditions required by the operator. Modification means can also be provided. The spatial resolution changing means changes the spatial resolution of the two-dimensional detecting means, and changes, for example, a scanning signal of an electron beam that reads out charges accumulated on the image pickup surface of the image pickup tube. For example, when the operator requests high-speed imaging, the spatial resolution changing means reduces the spatial resolution of the two-dimensional detecting means. When the spatial resolution is lowered, for example, the scanning of the electron beam in the image pickup tube can be performed at high speed, and the time required for detection can be shortened, that is, the period in which the level of the detection synchronization signal 35 in FIG. 3 is H can be shortened. . Therefore, the pulse interval of the X-ray irradiation signal 34 can be shortened, and the time required for data collection itself can be shortened. For example, the speed of the rotary ring 24 in the projection direction changing means shown in FIG. 2 can be increased to shorten the imaging time. it can. Further, when the operator requests high-definition imaging, the spatial resolution changing means improves the spatial resolution of the two-dimensional detection means. If the spatial resolution is improved, the accuracy of the reconstruction calculation by the three-dimensional image reconstructing means is improved, and a more precise three-dimensional distribution of the X-ray absorption coefficient can be obtained. As described above, according to the present invention, since the spatial resolution changing means capable of changing the spatial resolution of the two-dimensional detecting means is provided according to the imaging condition required by the operator, high-speed imaging or high-definition imaging can be performed according to the operator's request. You can take a picture.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described in detail with reference to the drawings. In each of the above-described embodiments, for example, the rotating ring 24 of the shooting direction changing unit shown in FIG. 2 can be rotated at high speed to reduce the influence of the movement of the subject during shooting, but shooting is performed in synchronization with the movement of the subject. This also reduces the effect of the movement of the subject during shooting. For example, when photographing a human body, there is a risk of being affected by movement due to the heartbeat. Therefore, for example, a motion detection unit that generates a motion synchronization signal that is a signal synchronized with the motion of the subject from an electrocardiogram and the like, and a shooting synchronization unit that synchronizes the X-ray irradiation timing with the motion synchronization signal are added to the shooting control unit. To do. An example of control by the photographing control means in this embodiment will be described with reference to the timing chart shown in FIG. In FIG. 10, the rotation start signal 31, the rotation completion signal 32, and the photographing start signal 33 have the same meanings as those shown in FIG. 3 and have the same functions. An electrocardiographic signal corresponding to an electrocardiogram measured by attaching an electrode to the body surface of an electrical signal from the myocardium 9
Motion synchronization signal 92 generated by the motion detection means based on 1.
Is obtained by performing threshold processing on the electrocardiographic signal 91, for example. The X-ray irradiation signal 93, the detection synchronization signal 94, and the detection valid signal 95 have the same meanings as those shown in FIG. 3 and have the same functions. However, the two-dimensional detection means and the three-dimensional image reconstruction means perform detection of transmitted X-rays and collection of detection results in synchronization with the detection synchronization signal 94 generated by the imaging control means.
The speed at which the projection direction is changed by the projection direction changing means (corresponding to the rotation speed of the rotating ring in the example of FIG. 2).
By using a circuit such as the PLL described above.
Synchronize to 2. However, for example, 1 of the motion detection signal 92
Instead of rotating the projection direction once in a cycle, the speed is advanced by the reciprocal number (for example, 1/180) of the total number of changes.
Next, an example of a three-dimensional imaging procedure based on this embodiment will be described with reference to FIG.
It will be described using 0. First, after the imaging start signal 33 becomes H, the X-ray irradiation signal 93 is set to H after a predetermined time elapses from the time when the first motion detection signal 92 becomes H. The delay between the motion detection signal 92 and the X-ray irradiation signal 93 is controlled by the photographing synchronization means. In other words, the imaging synchronization means sets the X-ray irradiation signal 93 to H after a certain period from the time when the motion detection signal 92 becomes H, and sets X to X.
The timing of irradiating the line is synchronized with the motion synchronization signal 92. Next, the imaging control means changes the X-ray irradiation signal 93 from H to L.
Then, after the X-ray irradiation is terminated, the detection synchronization signal 94
Is set to H to detect transmitted X-rays and collect detection results. When the motion detection signal 92 becomes H again, the X-ray irradiation signal 9 is output after a certain period of time by the imaging synchronization means as in the previous case.
Set 3 to H. At this time, since the speed of changing the projection direction by the projection direction changing means is advanced by the reciprocal of the total number of changes, X is reached when the predetermined projection direction is reached.
The line will be illuminated. Next, the imaging control unit changes the X-ray irradiation signal 93 from H to L to end the X-ray irradiation, and then sets the detection synchronization signal 94 to H to detect the transmitted X-rays and collect the detection results. By repeating irradiation, detection, and collection of X-rays synchronized with the motion detection signal 92 a predetermined number of times of changing the projection direction, two-dimensional transmission X-rays at a time point after a certain period from the motion synchronization signal. The intensity distribution can be collected over all projection directions. Therefore, reconstruction operation is performed using the collected two-dimensional intensity distribution, and a three-dimensional distribution of the X-ray absorption coefficient that is less affected by the movement of the subject is obtained.

As described above, in the present embodiment, since X-ray irradiation and detection and detection results are collected in synchronization with the movement of the subject, the influence of the movement of the subject can be reduced and the X-ray absorption coefficient can be reduced. High accuracy and high resolution can be achieved. In the present embodiment, the imaging synchronization means sets the X-ray irradiation signal 93 to H only once after a certain period from the time when the motion detection signal becomes H, but it can also be set to H multiple times. Figure 1
FIG. 1 is a timing chart showing an example of control by the photographing control means. Except for the X-ray irradiation signal 96 and the detection synchronization signal 97,
It is the same as that shown in FIG. In the example of FIG. 11, the shooting synchronization means synchronizes with the motion detection signal 92, and
An X-ray irradiation signal composed of three pulses indicated by b and c is generated. Further, the detection synchronization signal 97 is generated in synchronization with the pulse of each X-ray irradiation signal, and the two-dimensional intensity distribution of the transmitted X-ray detected in synchronization with the detection synchronization signal 97 is collected by the three-dimensional image reconstructing means. To be done. The three-dimensional image reconstructing means reconstructs an image only from the acquisition result (for example, the two-dimensional intensity distribution acquired at the time point a on the detection synchronization signal 97) whose detection time points are the same when viewed from the motion detection signal 92. Therefore, the three-dimensional distribution of the X-ray absorption coefficients of a plurality of subjects with different delays can be obtained from the motion detection signal 92. As a result, the three-dimensional distribution of the X-ray absorption coefficient of a plurality of subjects having different movements can be photographed by one photographing. Further, in the present embodiment, X-ray irradiation and detection and collection of detection results are performed in synchronization with the movement of the subject, but the movement of the subject becomes irregular during imaging, and accurate synchronization cannot be obtained. In this case, for example, the period of the motion detection signal may be measured, an extreme change in the period may be detected, and shooting may be stopped or redone.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described in detail with reference to the drawings. In each of the above-described embodiments, the so-called still imaging method for deriving the three-dimensional distribution of the X-ray absorption coefficient in a desired state has been described, but the X-ray absorption coefficient of the subject is different (for example, to a living body). By collecting data before and after the injection of the contrast agent, or before and after the irradiation of X-rays, the change in the condition of the subject can be photographed. FIG. 12 shows the basic configuration of this embodiment. The X-ray irradiation means 1, the two-dimensional detector 2, the projection direction changing means 3, the three-dimensional image reconstructing means 4, the imaging control means 5, the subject 11, the X-rays 12, and the transmitted X-rays 13 are the same as those in FIG. With the function of. The two-dimensional data storage means 101 for storing the detection result of the two-dimensional intensity distribution of the transmitted X-ray detected by the two-dimensional detector 2 is composed of, for example, a semiconductor memory device for digitizing and storing the detection result. Two-dimensional detector 2
The two-dimensional difference image generation means 102 for generating a two-dimensional difference image, which is a difference image between the detection result of the two-dimensional intensity distribution of the transmitted X-ray detected in step 2 and the detection result stored in the two-dimensional data storage means 101, For example, it is composed of an arithmetic element capable of subtraction processing, a microprocessor, or the like. Multiple 3D image display means 103 capable of superimposing and displaying the reconstruction results obtained by the plurality of 3D image reconstruction means 4 in a visually recognizable form.
Is composed of, for example, appropriate image processing for converting a pixel value into a gray value and a display device such as a CRT. Multiple 3
The three-dimensional image display means 103 has the three-dimensional image display means 6 in FIG. 1 and a function capable of displaying a plurality of reconstruction results in an overlapping manner. As this superimposition display method, for example,
There is a method of simply changing the color and brightness of images to be superposed according to pixel values of the images to be superposed, a method of semi-transparent display in surface display, and the like.

Next, an example of a three-dimensional photographing procedure based on this embodiment will be described. First, the first three-dimensional imaging is performed according to the same procedure as in the first embodiment, and the three-dimensional distribution of the X-ray absorption coefficient of the subject 11 is obtained. However, when the two-dimensional intensity distribution of the transmitted X-ray detected by the two-dimensional detector 2 is captured by the three-dimensional image reconstructing means 4, the captured intensity distribution is also stored in the two-dimensional data storage means 101. The image generating means 102 does not perform any processing (the intensity distribution detected by the two-dimensional detector 2 is directly taken into the three-dimensional image reconstructing means 4). Further, the reconstruction result by the three-dimensional image reconstruction means 4 is
The multiplex three-dimensional image display means 103 is displayed by the same method as the three-dimensional image display means 6 of FIG. Next, the second three-dimensional imaging is performed in consideration of the state in which the X-ray absorption coefficient of the subject has changed. The second three-dimensional imaging is basically performed in the same procedure as the first one, but in the second one, the two-dimensional difference image generation means 102 makes a difference to the intensity distribution detected by the two-dimensional detector 2. To do. Transmission X detected by the two-dimensional detector 2
The two-dimensional intensity distribution of the line is sent to the two-dimensional difference image generation means 102 before being captured by the three-dimensional image reconstruction means 4. Two
The two-dimensional difference image is generated by the two-dimensional difference image generating means 102 between the intensity distribution detected by the two-dimensional detector 2 and the intensity distribution in the two-dimensional data storage means 101 stored at the time of the first imaging. To generate. Three-dimensional image reconstruction means 4
Then, the generated two-dimensional difference images are sequentially captured, and 2
The reconstruction calculation is performed by regarding the dimensional difference image as the intensity distribution of the transmitted X-ray. By performing the reconstruction on the difference image in this way, a change in the X-ray absorption coefficient between the first imaging and the second imaging can be obtained. The result of the reconstruction calculation is displayed by the multiplex three-dimensional image display means 103, for example, after superimposing the reconstruction result in the first photographing.

As described above, in this embodiment, the two-dimensional difference image obtained by performing the difference between the intensity distribution detected by the two-dimensional detector 2 and the intensity distribution detected and stored in advance is reconstructed. Therefore, the change in the X-ray absorption coefficient with respect to the change in the state of the subject can be displayed, and the state of the subject can be displayed in more detail.
You can understand it carefully. In addition, the three-dimensional distribution of the X-ray absorption coefficient of the subject photographed in advance and the X
Since the change in the linear absorption coefficient can be displayed in an overlapping manner, the position of the changed portion can be grasped from the result of the image capturing in advance, and the image capturing result can be recognized quickly and accurately. In this example,
The image was taken twice, and the difference was obtained between the two obtained two-dimensional intensity distributions, but the image was taken three times or more and the difference was made between any two two-dimensional intensity distributions. Is also possible. For example, it is possible to always store the two-dimensional intensity distribution obtained in the first imaging in the two-dimensional data storage means and perform the difference between the two-dimensional intensity distribution in the third imaging, the fourth imaging, and the like. it can. Alternatively, the two-dimensional intensity distribution obtained by the second, third, etc. photographing is also stored in the two-dimensional data storage means (data already stored is rewritten), and the two consecutive photographing (for example, the second photographing) It is also possible to perform the difference at the third time, the third time and the fourth time, etc.). Further, in the present embodiment, the three-dimensional image display means is used to superimpose and display the three-dimensional distribution of the X-ray absorption coefficient of the subject photographed in advance and the change of the X-ray absorption coefficient with respect to the change of the state of the subject. However, it is also possible to display only the change of the X-ray absorption coefficient with respect to the change of the state of the subject by using the three-dimensional image display means of FIG. 1, or to combine both.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described in detail with reference to the drawings. In each of the above-described embodiments, the so-called still imaging method for deriving the three-dimensional distribution of the X-ray absorption coefficient in a desired certain state has been described, but the X-ray absorption coefficient of the subject is different (for example, to a living body). It is also possible to capture the change in the state of the subject by collecting data before and after the injection of the contrast agent, or before and after the injection of the contrast agent). FIG. 13 is a diagram showing the basic configuration of this embodiment. The X-ray irradiation means 1, the two-dimensional detector 2, the projection direction changing means 3, the three-dimensional image reconstruction means 4, the imaging control means 5, the three-dimensional image display means 6, the subject 11, the X-rays 12, and the transmitted X-rays 13 are , Has the same function as that of FIG.
The three-dimensional area extracting means 104 capable of extracting a desired area from the three-dimensional distribution of the X-ray absorption coefficient of the subject obtained as a result of the reconstruction operation in the three-dimensional image reconstructing means 4 can obtain the reconstruction result, for example. It is composed of an arithmetic element such as a multiplier for arithmetic processing or a microprocessor. As the extraction method, for example, a binarization method using an appropriate threshold value or the like is used. The three-dimensional data storage unit 105 that stores the extraction result of the three-dimensional region extraction unit 104 is configured by, for example, a semiconductor storage element that stores the extraction result in a digitized form. The three-dimensional difference image generation means 106 capable of generating a three-dimensional difference image, which is a difference image between the reconstruction result of the three-dimensional image reconstruction means 4 and the extraction result stored in the three-dimensional data storage means 105, is, for example, , A subtraction processing arithmetic element, a microprocessor, or the like. Next, an example of a three-dimensional imaging procedure based on this embodiment will be described. First, the first three-dimensional imaging is performed according to the same procedure as in the first embodiment, and the three-dimensional distribution of the X-ray absorption coefficient of the subject 11 is obtained. However, the result obtained by the three-dimensional image reconstructing means 4 is not directly sent to the three-dimensional image display means 6 and displayed, but is sent to the three-dimensional area extracting means 104. The three-dimensional area extracting means 104
According to the operator's instruction, a desired area (for example, only the bone area when the subject is a human body) is extracted from the three-dimensional distribution of the X-ray absorption coefficient sent from the three-dimensional image reconstructing means 4. The extraction result is sent to the three-dimensional data storage unit 105, only the extraction region has the X-ray absorption coefficient obtained by the three-dimensional image reconstructing unit 4, and the values of the other regions are zero (no absorption). It is stored as data. Next, the second three-dimensional imaging is performed in consideration of the state in which the X-ray absorption coefficient of the subject has changed. The second three-dimensional imaging is also performed according to the same procedure as in the first embodiment. However, the result obtained by the three-dimensional image reconstructing means 4 is not directly sent to the three-dimensional image display means 6 for display, but is sent to the three-dimensional difference image generating means 106. The three-dimensional difference image generation unit 106 stores the reconstruction result sent from the three-dimensional image reconstruction unit 4 and the 3 stored at the time of the first imaging.
The difference with the extraction result in the dimensional data storage unit 105 is calculated to generate a three-dimensional difference image. Here, the three-dimensional difference image is an X outside the area extracted by the three-dimensional area extracting unit 104.
An image is obtained by superimposing the X-ray absorption coefficient and the change of the X-ray absorption coefficient with respect to the change of the state of the subject. For example, when the subject is a human body, a bone region is extracted by the three-dimensional region extraction unit 104 and images are taken before and after angiography, and an image in which a region other than the bone and the blood vessel are superimposed is obtained. The generated three-dimensional difference image is sent to the three-dimensional image display means 6 and displayed.

As described above, in this embodiment, the difference between the three-dimensional distribution of the X-ray absorption coefficient of the subject obtained by the three-dimensional image reconstructing means and the three-dimensional distribution of the X-ray absorption coefficient photographed in advance is calculated. After the operation, it will be displayed.
The change in the linear absorption coefficient can be displayed, and the state of the subject can be grasped in more detail and detail. In addition, since a desired area is extracted from the three-dimensional distribution of the X-ray absorption coefficient photographed in advance, the difference with the newly photographed X-ray absorption coefficient is calculated. Therefore, it is extracted from the newly photographed X-ray absorption coefficient. It is possible to remove the part relating to the region, for example, it is possible to reduce the overlap of the images of the bone, which is an obstacle when grasping the fine structure of blood vessels,
You can understand the subject's condition in more detail and detail. In the present embodiment, the three-dimensional region extracting means 1 is used for the first photographing.
After extracting a desired area from the reconstruction result by 04, the extraction result is stored in the three-dimensional data storage means 105.
It is also possible to omit the function of the dimensional area extracting unit 104 and store the reconstruction result directly in the three-dimensional data storage unit 105. In this case, the change in the X-ray absorption coefficient with respect to the change in the state of the subject can be displayed. In addition, in this embodiment,
Similar to the case of the sixth embodiment described with reference to FIG. 12,
It is also possible to superimpose and display other information such as the three-dimensional distribution of the X-ray absorption coefficient of the subject photographed in advance by using the multiple three-dimensional image display means.

(Eighth Embodiment) Next, an eighth embodiment of the present invention will be described in detail with reference to the drawings. In each of the embodiments described above, the three-dimensional distribution of the X-ray absorption coefficient of the subject is derived and displayed from the intensity distribution of the plurality of transmitted X-rays collected while changing the projection direction by the projection direction changing means. It is also possible to display a projected image which is a two-dimensional intensity distribution of the transmitted X-rays in the desired direction. FIG. 14 is a diagram for explaining the basic configuration of this embodiment. X-ray irradiation means 1, two-dimensional detector 2, projection direction changing means 3, three-dimensional image reconstruction means 4,
Photographing control means 5, three-dimensional image display means 6, subject 11,
The X-ray 12 and the transmitted X-ray 13 have the same functions as those in FIG. The projection image generation means 111 capable of generating a projection image which is a two-dimensional intensity distribution of transmitted X-rays transmitted through the subject directly takes in the detection result of the two-dimensional detection means 2, for example. The two-dimensional display means 112 capable of displaying the projected image generated by the projected image generating means 111 in a visually recognizable form is, for example,
Appropriate image processing and CR for converting pixel values into gray values
It is composed of a display device such as T. The projection direction instructing means 113 that allows the operator to instruct a desired projection direction based on the three-dimensional distribution of the X-ray absorption coefficient of the subject displayed on the three-dimensional image display means 6 is, for example, a three-dimensional image display means. It is configured by using a coordinate input device such as a mouse, a trackball, or a touch panel that allows coordinate input while observing the display screen of 6. Next, an example of a photographing procedure based on this embodiment will be described. First, after fixing the projection direction that can be changed by the projection direction changing means 3 to an appropriate predetermined direction, the X-ray irradiation means 1 continuously emits X-rays. As a result of the irradiation, the two-dimensional intensity distribution of the transmitted X-ray transmitted through the subject is detected by the two-dimensional detection means 2. The detected two-dimensional intensity distribution is displayed on the display screen by the two-dimensional image display means 112 through the projection image generation means 111. This detection and display can be sequentially repeated to perform fluoroscopic imaging of the subject. The operator can grasp the state of the subject by observing the projected image displayed on this display screen. next,
The operator gives an instruction to start the three-dimensional imaging to the imaging control means 5. The instruction timing for starting the imaging can be determined based on the observation result of the projected image, and the procedure of the three-dimensional imaging after the instruction follows the same procedure as in the first embodiment. The three-dimensional distribution of the X-ray absorption coefficient of the subject 11 obtained as a result of photographing is displayed on the display screen of the three-dimensional image display means 6. The operator uses the projection direction instruction means 113 to display the three-dimensional image. While observing the image displayed on the means 6, the desired projection direction is designated. As an instruction method, for example, the X-ray absorption coefficient along the plane formed by the X-ray irradiation surface and the light-receiving surface of the projection direction changing unit 3 at the time of three-dimensional imaging is displayed on the display screen of the three-dimensional image display unit 6. A cross-section is displayed above, and a line segment that passes through the center of this cross-section (the direction of the line segment represents the projection direction) is input using a mouse or the like. Alternatively, as another example, the X-ray absorption coefficient representing the outer shape of the subject is extracted and displayed on the surface of the display screen of the three-dimensional image display means 6, and one point on this surface is input using a mouse or the like. The direction of the line segment connecting the input point and the origin of the three-dimensional space represents the projection direction. Projection direction indicating means 1
When the projection direction is designated by 13, the projection direction designating means 11
3 requests the photographing control means 5 to perform X-ray irradiation and detection in the designated projection direction. Upon receiving the request, the imaging control unit 5 requests the projection direction changing unit 3 to change the projection direction, generates an X-ray irradiation signal when the desired projection direction is reached, and irradiates the X-ray, and The detection synchronizing signal is set to H and control is performed so as to detect a transmitted X-ray. Transmission X detected
The two-dimensional intensity distribution of the line is 2
It is displayed on the display screen by the three-dimensional image display means 112. Therefore, the projection image in the projection direction designated by the projection direction designating means 113 is displayed on the display screen.

As described above, in this embodiment, the three-dimensional distribution of the X-ray absorption coefficient of the object photographed in advance and the projected image of the object at the present time can be observed at the same time, and the object can be grasped in more detail and closeness. Further, it is possible to determine the timing to start the three-dimensional imaging while observing the state of the subject by the fluoroscopic imaging, and to start the three-dimensional imaging in a more optimal state such as how the contrast agent spreads in angiography. It is possible to accurately extract the information, and it is possible to reduce imaging mistakes and reduce the amount of radiation exposure by preventing unnecessary X-ray irradiation. When capturing a projected image, a desired projection direction can be designated based on the three-dimensional distribution of the X-ray absorption coefficient of a subject that has been captured in advance. For example, the projection direction to be observed, such as a portion having an abnormal absorption coefficient, can be specified. , The X-ray absorption coefficient can be directly determined from the imaging result, and the subject can be grasped quickly and accurately. In the present embodiment, the projection direction that can be changed by the projection direction changing means is fixed to a predetermined appropriate direction, and then the subject is fluoroscopically photographed. You can change to the desired direction. However, in the state before performing the three-dimensional imaging, although it is not possible to instruct based on the three-dimensional distribution of the X-ray absorption coefficient of the subject, for example, the position of the X-ray irradiation surface in the projection direction changing unit is directly instructed. This can be done by using methods that can be instructed together. Further, in the present embodiment, the projection image obtained by the projection image generating means is used for determining the instruction timing for starting the three-dimensional imaging, but it may be used for determining the three-dimensional imaging position.
For example, first, the positional relationship between the subject and the X-ray irradiating means and the two-dimensional detector is adjusted while observing the subject by fluoroscopy. At this time, the positional relationship between the projection image obtained by the fluoroscopic imaging and the imaging visual field in the three-dimensional imaging is determined in advance, and the region to be three-dimensionally imaged is adjusted to be within the imaging visual field. For example, on the display screen of the two-dimensional image display means, this photographing field of view is represented by an appropriate frame, adjustment is performed so that a desired part is included in this frame, and after the photographing position is determined, three-dimensional photographing of the subject is performed. To start. In this way, since the three-dimensional imaged part is determined from the projected image, the part to be observed can be surely three-dimensionally imaged.
It is possible to accurately extract desired information, reduce imaging mistakes, and reduce exposure dose by preventing unnecessary X-ray irradiation. Also,
In the present embodiment, the two-dimensional image display means capable of displaying the projected image and the three-dimensional image display means capable of displaying the three-dimensional distribution of the X-ray absorption coefficient are respectively prepared, but both information are displayed on the same screen. It is also possible to use a means of displaying the images side by side or displaying them in an overlapping manner. When the means shown in FIG. 5 is used as the projection direction changing means, the electric motor 53 can be operated to move the arcuate arm 55, so that projection images can be taken in various projection directions without moving the subject. Further, the X-ray irradiation means, the two-dimensional detection means, and the projection direction changing means used in the three-dimensional imaging are used for the imaging of the projected image, but other respective means are prepared for imaging the projected image, for example, It is possible to perform photography without being restricted in performing three-dimensional photography, such as the degree of freedom of changeable projection direction.

(Ninth Embodiment) Next, a ninth embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, the projected image, which is the two-dimensional intensity distribution of the transmitted X-rays in the direction desired by the operator, is displayed, but the X-ray absorption coefficient of the subject is different (for example, to the biological environment). By collecting data before and after the injection of the contrast agent, or before and after the irradiation of X-rays, the change in the condition of the subject can be photographed and displayed.
FIG. 15 is a diagram for explaining the basic configuration of this embodiment. X
Line irradiation means 1, two-dimensional detector 2, projection direction changing means 3,
The three-dimensional image reconstructing unit 4, the photographing control unit 5, the three-dimensional image display unit 6, the subject 11, the X-rays 12, and the transmitted X-rays 13 have the same functions as those in FIG. In addition, the projection image generation means 1
11. The projection direction changing means 113 has the same function as that of FIG. The projection data storage unit 114 capable of storing the projection image generated by the projection image generation unit 111 is composed of, for example, a semiconductor memory element that digitizes and stores the projection result. Projection difference image generation means 1 capable of generating a projection difference image, which is a difference image between the projection image generated by the projection image generation means and the projection image stored in the projection data storage means 114.
Reference numeral 15 is composed of, for example, an arithmetic element for performing subtraction processing, a microprocessor, or the like. The multiple two-dimensional image display means 116 capable of superimposing and displaying a plurality of projected images in a visually recognizable form includes, for example, appropriate image processing for converting a pixel value into a gray value and a display device such as a CRT. Composed.
The multiplex two-dimensional image display means 116 is a three-dimensional image display means 112 in FIG. 14 with a function capable of displaying a plurality of projected images in an overlapping manner. This is done by changing the color and brightness of the image to be displayed according to the pixel value of the image to be superimposed. Next, an example of a photographing procedure based on this embodiment will be described. First, a projected image of the subject 11 in a desired projection direction is photographed (first photographing). The shooting procedure is according to the eighth embodiment. However, although the obtained projection result is stored in the projection data storage means 114, the projection difference image generation means 115
Then, without performing any processing, the multiplex two-dimensional image display means 116 directly converts the grayscale value and displays it. Next, the second projection image is photographed without changing the projection direction while observing the state where the X-ray absorption coefficient of the subject has changed. The obtained projection result is sent to the projection difference image generation means 115, and the difference is obtained with the projection image stored in the projection data storage means 114. The difference gives the change in the intensity of the transmitted X-ray between the first and second imaging. The projection difference image obtained as a result of the difference is displayed by the multiplex two-dimensional image display means 116, for example, overlapping the projection image in the first photographing.

As described above, in this embodiment, since the projection difference image obtained by performing the difference from the projection image captured in advance is displayed,
The change in the intensity of the transmitted X-ray with respect to the change in the state of the subject can be displayed, and the state of the subject can be grasped in more detail and detail.
In addition, since the projection image of the subject captured in advance and the change in the intensity of the transmitted X-ray with respect to the change in the condition of the subject can be displayed in an overlapping manner, the position of the changed portion can be grasped from the result of the advance capture, The result can be recognized quickly and accurately.
In the present embodiment, the difference is obtained between the two projected images obtained by performing the photographing twice, but it is also possible to perform the difference between the arbitrary two projected images by performing the photographing three times or more. For example, it is possible to always store the projection image obtained in the first photographing in the projection data storage means and make a difference with the projection images in the third and fourth photographing. Alternatively, the projection images obtained by the second and third shootings are also stored in the projection data storage means (data already stored is rewritten), and two consecutive shootings (for example, the second and third shootings). , The third time and the fourth time, etc.). Further, in the present embodiment, by using the multiplex two-dimensional image display means, it is possible to superimpose and display the projection image of the subject photographed in advance and the change in the intensity of the transmitted X-ray with respect to the change in the state of the subject. By using the two-dimensional image display means of FIG. 14, it is possible to display only the change in the intensity of the transmitted X-ray with respect to the change in the state of the subject, or to display both in combination.

(Tenth Embodiment) Next, the tenth embodiment of the present invention will be described.
Embodiments will be described in detail with reference to the drawings. In the ninth embodiment, the change in the intensity of the transmitted X-ray with respect to the change in the state of the subject is grasped by the difference processing between the projection image of the subject captured in advance and the projection image newly captured. After re-projecting the three-dimensional distribution of the X-ray absorption coefficient of the subject that has been captured and collected, the change in the condition of the subject can be grasped by the difference processing between the re-projection result and the newly captured projection image. FIG. 16 is a diagram for explaining the basic configuration of this embodiment. X-ray irradiation means 1, two-dimensional detector 2, projection direction changing means 3, three-dimensional image reconstruction means 4, imaging control means 5, three-dimensional image display means 6, subject 11, X-rays 12, transmitted X-rays 13.
Has the same function as in FIG. The projection image generation means 111, the two-dimensional image display means 112, and the projection direction changing means 113 have the same functions as those in FIG. 14, and the projection difference image display means 115 has the same functions as those in FIG. Hold. The three-dimensional area extracting means 117 capable of extracting a desired area from the three-dimensional distribution of the X-ray absorption coefficient of the subject obtained as a result of the reconstruction operation by the three-dimensional image reconstructing means 4 can obtain the reconstruction result, for example. It is composed of an arithmetic element such as a multiplier for arithmetic processing or a microprocessor. As the extraction method, for example, binarization processing with an appropriate threshold value is used. The three-dimensional data storage unit 118 capable of storing the extraction result of the three-dimensional area extraction unit 117 is composed of, for example, a semiconductor storage element that stores the extraction result in a digitized form. The reprojection image generation unit 119 capable of generating a reprojection image that is a result of reprojection in a certain projection direction based on the extraction result stored in the three-dimensional data storage unit 118, for example, performs various arithmetic operation processes. It is composed of a computing element to be performed, a microprocessor, a memory element for storing a computation result, or the like. Next, an example of a photographing procedure based on this embodiment will be described. First, three-dimensional imaging is performed according to the same procedure as in the first embodiment, and the three-dimensional distribution of the X-ray absorption coefficient of the subject 11 is obtained. The result obtained by the three-dimensional image reconstructing means 4 is sent to the three-dimensional area extracting means 117. The three-dimensional area extracting unit 117, according to the instruction of the operator, selects a desired area (for example, from the three-dimensional distribution of the X-ray absorption coefficient sent from the three-dimensional image reconstructing unit 4).
If the subject is a human body, only the bone region) is extracted. The extraction result is sent to the three-dimensional data storage unit 118, and has the X-ray absorption coefficient obtained by the three-dimensional image reconstructing unit 4 only in the extraction region, and as the data in which the coefficient is zero (no absorption) in other regions. Is stored. Next, a state in which the X-ray absorption coefficient of the subject has changed is observed, and a projection image of the subject 11 in a desired projection direction is taken according to the same procedure as in the eighth embodiment. The obtained projection image is sent to the projection difference image generation means 115. Further, the reprojection image generation means 119 generates a reprojection image obtained by reprojecting in the same projection direction as the captured projection image. The generated re-projection image is sent to the projection difference image generation unit 115, and the difference is obtained between it and the projection image from the projection image generation unit 111. The projection difference image obtained as a result of the difference is the X outside the area extracted by the three-dimensional area extracting means 118.
An image is obtained by superimposing the linear absorption coefficient and the change in the intensity of the transmitted X-ray with respect to the change in the state of the subject. For example, when the subject is a human body, a bone region is extracted by the three-dimensional region extracting unit 118, and images are taken before and after angiography, so that a projected image in which a region other than the bone and the blood vessel are superimposed is obtained. The generated projection difference image is sent to the two-dimensional image display means 112 and displayed.

As described above, in this embodiment, after the three-dimensional imaging is performed in advance and the three-dimensional distribution of the X-ray absorption coefficient of the object collected is re-projected, the result between the re-projection result and the newly captured projection image is Since the change of the state of the subject is grasped by the difference processing of 3), once the three-dimensional imaging is performed in advance, the intensity of the transmitted X-ray with respect to the change of the state of the subject can be changed by simply taking the projection image in the arbitrary projection direction. Changes can be displayed and the subject's condition can be grasped in more detail and detail. In addition, X taken in advance
Since the re-projection process is performed after extracting a desired region from the three-dimensional distribution of the linear absorption coefficient, it is possible to remove a portion related to the region extracted from the newly captured projection image. For example, when grasping a fine structure of a blood vessel. It is possible to reduce overlapping of images of bones, which hinders the user, and to grasp the condition of the subject in more detail and detail. In this embodiment, after the desired area is extracted from the reconstruction result by the three-dimensional area extracting means 117 and the extraction result is stored in the three-dimensional data storing means 118, the function of the three-dimensional area extracting means 117 is omitted. The reconstruction result may be directly stored in the three-dimensional data storage means 118. In this case, the change in the intensity of the transmitted X-ray with respect to the change in the state of the subject can be displayed. Further, in the present embodiment, as in the case of the ninth embodiment described with reference to FIG. 15, other information such as a projected image of a subject photographed in advance is superimposed by using the multiplex two-dimensional image display means. Can be displayed. Note that, in each of the above-described embodiments, mainly relates to a method and apparatus associated with three-dimensional imaging (in particular, the third to tenth embodiments).
With respect to (3), it is applicable to the case of performing three-dimensional imaging without using parallel X-rays. For example, a conventional fan-shaped beam X-ray is used to obtain a three-dimensional distribution of the X-ray absorption coefficient of the subject 3.
It is also applicable when performing three-dimensional imaging.

[0031]

As described above, according to the present invention, since the multiple parallel plane X-ray beam having a constant two-dimensional intensity distribution is used, the reconstruction algorithm used in the conventional X-ray CT is used as the reconstruction operation. Applicable, in the process of reconstruction operation,
It is possible to avoid the conventional problem of being susceptible to external factors such as noise at the time of measurement, and it is possible to achieve high precision and high resolution of the X-ray absorption coefficient obtained as a result of image reconstruction. According to the device of the present invention, it is possible to perform three-dimensional imaging by designating the imaging conditions, the observation site, etc., only by operating the push button switch, eliminating the need for complicated operations, speeding up imaging, and improving measurement efficiency. Can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a projection direction changing unit.

FIG. 3 is a diagram illustrating an example of control of a photographing control unit.

FIG. 4 is a diagram illustrating an example of an X-ray irradiation unit.

FIG. 5 is a diagram illustrating an example of a projection direction changing unit.

FIG. 6 illustrates a control example of a deflection control unit.

FIG. 7 is a diagram illustrating an example of multiple parallel plane X-ray beam irradiation means.

FIG. 8 is a diagram illustrating an X-ray irradiating means according to a second embodiment of the present invention.

FIG. 9 is a diagram illustrating an example of a multiple fan-shaped plane X-ray beam irradiation unit.

FIG. 10 is a timing chart showing an example of control of a photographing control means according to the fourth embodiment of the present invention.

FIG. 11 is a timing chart showing another control example of the photographing control means in the fourth embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a sixth exemplary embodiment of the present invention.

FIG. 13 is a diagram showing the configuration of a seventh exemplary embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of an eighth exemplary embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of a ninth exemplary embodiment of the present invention.

FIG. 16 is a diagram showing the configuration of a tenth embodiment of the present invention.

[Explanation of symbols]

1 ... X-ray irradiation means, 2 ... Two-dimensional detection means, 3 ... Projection direction deflection means, 4 ... Three-dimensional image reconstruction means, 5 ... Imaging control means, 6 ... Three-dimensional image display means, 7 ... X-ray generation means , 8 ...
Solar slit, 9 ... X-ray generating means, 10 ... Solar slit, 11 ... Subject, 12 ... X-ray, 13 ... Transmitted X
X-ray, 21 ... X-ray tube, 22 ... X-ray image intensifier, 23 ... TV camera, 24 ... Rotating ring, 25 ...
Electric motor, 31 ... Rotation start signal, 32 ... Rotation completion signal, 3
3 ... Imaging start signal, 34 ... X-ray irradiation signal, 35 ... Detection synchronization signal, 36 ... Detection valid signal, 41 ... Cathode, 42 ...
Target, 43 ... Deflection means, 61 ... X-deflection signal, 6
2 ... Y-deflection signal, 63 ... Multilayer film concave mirror, 71 ... Target, 72 ... Deflection means, 81 ... Multilayer film concave mirror, 91 ... Electrocardiographic signal, 92 ... Motion detection signal, 93 ... X-ray irradiation signal, 9
4 ... Detection synchronization signal, 95 ... Detection effective signal, 101 ... Two-dimensional data storage means, 102 ... Two-dimensional difference image generation means,
103 ... Multiple 3D image display means, 104 ... 3D area extraction means, 105 ... 3D data storage means, 106 ... 3
Dimensional difference image generation means, 111 ... Projection image generation means, 11
2 ... Two-dimensional image display means, 113 ... Projection direction instruction means,
114 ... Projection data storage means, 115 ... Projection difference image generation means, 116 ... Multiple two-dimensional image display means, 117 ... 3
Dimensional area extraction means, 118 ... Three-dimensional data storage means, 1
19 ... Reprojection image generation means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Ueda 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (25)

[Claims] 1. A parallel X-ray irradiating means for irradiating a subject with parallel X-rays, a two-dimensional detecting means for detecting a two-dimensional intensity distribution of transmitted X-rays transmitted through the subject, and the parallel X-rays for the subject. Projection direction changing means for changing the projection direction for obtaining a two-dimensional intensity distribution of transmitted X-rays, and a three-dimensional distribution of the X-ray absorption coefficient of the subject based on the two-dimensional intensity distributions in a plurality of projection directions. A three-dimensional imaging apparatus having a three-dimensional image reconstructing means for reconstructing. 2. The three-dimensional imaging apparatus according to claim 1, wherein the parallel X-ray irradiating means irradiates a multiple parallel plane X-ray beam composed of a plurality of parallel plane X-ray beams parallel to each other. A three-dimensional imaging device characterized by. 3. The three-dimensional imaging apparatus according to claim 1, wherein the parallel X-ray irradiation means irradiates a multiple fan-shaped plane X-ray beam composed of a plurality of mutually parallel fan-shaped plane X-ray beams. A three-dimensional imaging device characterized by. 4. The three-dimensional imaging apparatus according to claim 1, wherein the projection direction changing means includes the parallel X-ray irradiating means and the two-dimensional detecting means in a predetermined manner. A three-dimensional imaging device characterized by rotating on a circumference having a distance as a diameter. 5. The three-dimensional imaging apparatus according to any one of claims 1 to 4, wherein at least parallel X-rays by the parallel X-ray irradiating means are in accordance with an operator's instruction to start three-dimensional imaging. Of the three-dimensional distribution in the three-dimensional image reconstructing means, the timing of irradiating the X-rays, the timing of detecting the transmitted X-rays in the two-dimensional detecting means, the timing of changing the projection direction in the projection direction changing means. A three-dimensional imaging apparatus having imaging control means for controlling the timing of reconstruction. 6. The three-dimensional imaging apparatus according to claim 1, wherein the two-dimensional detector includes at least X-ray light conversion means for converting transmitted X-rays into visible light and visible light. A three-dimensional imaging device comprising: a photoelectric conversion unit that converts light into an electric signal. 7. The three-dimensional imaging apparatus according to claim 1, wherein the parallel X-ray irradiating means is configured to emit X-rays by colliding the cathode emitting thermoelectrons with the thermoelectrons.
A target that generates a line, and a deflection unit that changes the movement direction of the thermoelectrons, the movement direction of the thermoelectrons is sequentially changed by the deflection unit, and the thermoelectrons scan the target. A three-dimensional imaging device characterized by generating parallel X-rays. 8. The three-dimensional imaging apparatus according to claim 7, further comprising a solar slit that controls a direction of X-rays emitted from the target. 9. A three-dimensional imaging apparatus according to claim 7, wherein the deflection means synchronizes the timing of changing the moving direction of the thermoelectrons by the deflection means with the timing of photographing the subject. A three-dimensional imaging device having a control means. 10. The three-dimensional imaging apparatus according to claim 1, wherein the parallel X-ray irradiation means is
3. A conical X-ray beam generation source that generates at least a conical X-ray, and a multilayer film concave mirror that reflects this conical X-ray beam as parallel X-rays.
Dimensional photography device. 11. The three-dimensional imaging apparatus according to claim 1, wherein the shadow direction changing means changes the projection direction and the two-dimensional detecting means transmits X.
A three-dimensional imaging apparatus comprising projection number changing means for changing the number of times of detecting a two-dimensional intensity distribution of a line according to a desired imaging condition. 12. The three-dimensional imaging apparatus according to claim 1, further comprising means for changing the spatial resolution of the two-dimensional detection means according to a desired imaging condition. A characteristic three-dimensional imaging device. 13. The three-dimensional photographing apparatus according to claim 1, wherein the movement detecting means for detecting the movement of the subject and the detected movement are synchronized with the photographing timing of the three-dimensional photographing. A three-dimensional image capturing apparatus, comprising: 14. The three-dimensional imaging device according to claim 1, wherein the two-dimensional data storage stores a two-dimensional intensity distribution of transmitted X-rays used in the three-dimensional image reconstructing means. Means and a two-dimensional difference image generation means for generating a two-dimensional difference image representing the difference between the intensity distributions stored in the two-dimensional data storage means, and representing the difference between the intensity distributions obtained by individual photographing. 2D obtained by generating a two-dimensional difference image
A three-dimensional imaging apparatus, which reconstructs a three-dimensional distribution of differences between the intensity distributions based on the three-dimensional difference image to generate a three-dimensional difference image. 15. The three-dimensional imaging apparatus according to claim 1, wherein the three-dimensional data storage means stores a three-dimensional distribution of the X-ray absorption coefficient of the subject, and the three-dimensional data storage means. A three-dimensional difference image representing a difference from the three-dimensional distribution stored in the data storage means, and a three-dimensional difference image representing a difference between the three-dimensional distributions obtained by individual photographing. A three-dimensional image capturing apparatus characterized by generating a. 16. The three-dimensional imaging apparatus according to claim 15, further comprising a three-dimensional area extracting means for extracting a desired area from the three-dimensional distribution of the X-ray absorption coefficient of the subject. Three-dimensional imaging device. 17. The three-dimensional imaging apparatus according to any one of claims 14 to 16, wherein the three-dimensional difference image is superimposed and displayed on the three-dimensional distribution of the X-ray absorption coefficient of the subject. A three-dimensional image capturing apparatus having multiple three-dimensional image display means. 18. The three-dimensional imaging apparatus according to claim 1, wherein a projection image having a two-dimensional intensity distribution of transmitted X-rays is generated in a desired projection direction. A three-dimensional imaging apparatus having an image generating means. 19. The three-dimensional imaging apparatus according to claim 18, further comprising a two-dimensional image display means for displaying the projection image obtained by the projection image generation means, the two-dimensional image display means comprising: A three-dimensional imaging device, which starts three-dimensional imaging based on a projected image displayed. 20. The three-dimensional image capturing apparatus according to claim 18, further comprising a two-dimensional image display means for displaying the projection image obtained by the projection image generating means, the two-dimensional image display means comprising: A three-dimensional imaging apparatus having means for designating a part to be three-dimensionally imaged based on a projected image displayed. 21. The three-dimensional imaging apparatus according to claim 18, wherein the three-dimensional distribution of the X-ray absorptance of the subject obtained by the three-dimensional reconstruction means is displayed. It has a three-dimensional image display means and a projection direction instruction means for instructing a desired projection direction based on the displayed three-dimensional distribution, and the projection image generation means is instructed by the projection direction instruction means. A three-dimensional imaging apparatus characterized by generating a projected image from a projection direction. 22. The three-dimensional imaging apparatus according to claim 18, wherein the projection data storage unit stores the projection image generated by the projection image generation unit, and the projection data storage unit. And a projection difference image generation unit that generates a projection difference image representing a difference from the projection image stored in
A three-dimensional imaging device characterized by generating a projection difference image representing a difference between projection images obtained by individual imaging. 23. The three-dimensional imaging apparatus according to claim 18, wherein the three-dimensional data storage means stores a three-dimensional distribution of the X-ray absorption coefficient of the subject, and the three-dimensional data. A reprojection image generation means for projecting the three-dimensional distribution stored in the storage means in the projection direction of the projection image generated by the projection image generation means, a projection image generated by the projection image generation means, and the reprojection image generation means. Projection difference image generation means for generating a projection difference image showing a difference from the generated reprojection image, and generating a projection difference image showing a difference between the projection images obtained by individual photographing Three-dimensional imaging device. 24. The three-dimensional imaging apparatus according to claim 23, further comprising a three-dimensional area extracting means for extracting a desired area from the three-dimensional distribution of the X-ray absorption coefficient of the subject. Three-dimensional imaging device. 25. The three-dimensional image capturing apparatus according to claim 22, wherein the projection image generated by the projection image generating means includes a projection image generated by the projection image generating means. A three-dimensional image capturing apparatus, comprising: a multiple three-dimensional image display unit that superimposes and displays the projection difference images generated in the above.