JP2000083942A - Radiation tomography method, device therefor, radiation detector and x-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation tomographic method for executing photographing of high spatial resolution by using plural detecting element arrays, and to provide the device, radiation detector and X-ray tube therefor. SOLUTION: In an X-ray irradiation and detection system having a plurality of detecting element arrays 250 and 270 of multi-channel, X-rays respectively radiated to the centers 252C and 272C of a center channel from X-ray focuses 450 and 470 are offset from the rotational center of the X-ray irradiation and detection system (isocenter) 320, and a picture is reconstituted based on data obtained by scanning the same slice successively by the arrays 250 and 270 and merging them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for radiation tomography, a radiation detector and an X-ray tube, and more particularly to a method and an apparatus for radiation tomography using a fan-shaped radiation beam, for a radiation beam having a width and a thickness. And a X-ray tube used to generate a radiation beam having a width and a thickness.

[0002]

2. Description of the Related Art As an example of a radiation tomography apparatus, for example, an X-ray computed tomography (CT) is used.
y) There is a device. In an X-ray CT apparatus, X-rays are used as radiation. An X-ray tube is used for X-ray generation.

An X-ray irradiator including an X-ray tube irradiates an X-ray beam having a width including an imaging range and a predetermined thickness in a direction perpendicular thereto. The thickness of the X-ray beam can be changed by adjusting the degree of opening of the X-ray passing aperture (aperture) of the collimator, so that the thickness of a slice for imaging can be adjusted. It has become.

An X-ray detector is a multi-channel in which a large number (for example, about 1000) of X-ray detection elements are arranged in an array in the direction of the width of an X-ray beam.
e) an X-ray detector for detecting X-rays.

[0005] The X-ray irradiation / detection system is rotated (scanned) around the subject, and the projection data (data) of the subject by the X-rays in a plurality of view directions around the subject is obtained. It measures and generates (reconstructs) a tomographic image based on the projection data.

The spatial resolution of the reconstructed image is determined by the channel pitch of the detector array.
In order to achieve a spatial resolution twice as fine as the channel pitch, a so-called quarter offset method is used.

As shown schematically in FIG. P1, this is a geometric relationship between a fan-shaped X-ray beam 102 having a focal point 100 and a detector element array 104 (geometry: geometry).
y) to the central channel 106 of the detector array 104
Straight line 110 connecting the channel center 108 and the focal point 100
Is the center of rotation of the X-ray irradiation / detection system (isocenter: is
center) 112 (offset)
It is designed to pass through places.

The offset distance is obtained by calculating the channel width of the central channel 106 converted to a value at the rotation center 110 by p.
Is set to be 1/4 (quarter offset). The converted channel width p corresponds to a value obtained by projecting the channel width of the central channel 106 back to the position of the rotation center 110 along the path of the X-ray beam.

In such a geometry, when the X-ray irradiation / detection system is rotated by 180 degrees, a straight line 110 ′ connecting the focal point 100 ′ and the channel center 108 ′ of the central channel 106 is formed as shown by a broken line and a two-dot chain line. , Rotation center 1
12 is a parallel line that is p / 4 away from the straight line 110 on the opposite side.

Since the straight lines 110 and 110 'both represent the path of the X-ray incident on the central channel 106, the X-ray path differs by p / 2 in the direction of the channel width by the same central channel 106 at this time. Line transmission signals are obtained respectively.

Similar relationships are established for the other channels whose X-ray directions are opposite to each other (opposed views). Therefore, the X-ray detection signals are interleaved (interleaved) between the facing views for each channel.
By performing e), projection data corresponding to that obtained by a detection element array having a channel pitch twice as fine is formed, and an image is reconstructed based on such projection data.

As one type of a multi-channel X-ray detector,
There is a type in which a plurality of detection element arrays are provided in the direction of the thickness of the X-ray beam and the X-ray beams are simultaneously received by a plurality of rows of detection element arrays. In such an X-ray detector,
Since X-ray detection signals for a plurality of slices can be obtained at one time by one scan, a multi-slice scan (multi
-Slice scan) is efficiently used as an X-ray detector. The quarter-offset technique is applied to such a detection element array to increase the spatial resolution of the reconstructed image.

The plurality of rows of the detection element arrays are arranged such that the slice positions are sequentially changed at the same pitch as the arrangement of the detection element arrays, so that each detection element array sequentially scans the same slice, The X-ray detection signals of the same slice obtained by each detection element row are fully added and S
/ N (signal-to-noise ratio)
It is also used for the purpose of obtaining a good X-ray detection signal.

[0014]

As described above, when a plurality of rows of detection element arrays are used, the path of X-rays incident on the detection element array is the same for each channel through a plurality of rows. There is a problem that the spatial resolution of the reconstructed image is not improved even if the line detection signals are fully added or interleaved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a radiation tomography method and apparatus for performing radiography with high spatial resolution using a plurality of detection element arrays, and to have high spatial resolution. An object of the present invention is to realize a radiation detector suitable for imaging and an X-ray tube suitable for imaging with high spatial resolution.

[0016]

According to a first aspect of the present invention, there is provided a fan-shaped radiation having a width and a thickness in one and the other of two directions perpendicular to an irradiation direction and perpendicular to each other. A beam is irradiated from the radiation irradiating means, and a detection element array in which a plurality of radiation detection elements are arranged in the direction of the width of the radiation beam with the incident surface facing the direction in which the radiation beam is incident, in the direction of the thickness of the radiation beam Detecting the radiation beam with a plurality of detection element arrays, rotating a radiation irradiation / detection system including the radiation irradiation means and the detection element array around a rotation axis perpendicular to a fan surface of the radiation beam. A radiation tomography method for generating a tomographic image of a slice through which the radiation beam has passed based on the radiation detection signals of a plurality of views obtained in the above-described manner. The line irradiation unit forms a straight line i connecting a plurality of focal points corresponding to the plurality of detection element rows and a center of each central radiation detection element in the plurality of detection element rows, from the rotation axis to the width of the radiation beam. Irradiating the plurality of detection element rows with the radiation beam from the plurality of focal points, respectively, in a geometric relationship passing substantially the following distance d along the direction of
Detecting a radiation detection signal for the same slice in each of the plurality of detection element rows, and generating a tomographic image based on a radiation detection signal obtained by combining all of the radiation detection signals from the plurality of detection element rows, Radiation tomography method.

Note that d = (4i-1) p / 4n on one side with respect to the rotation axis in the range of d <p / 2, and d = (4i-3) p / 4n on the other side with respect to the rotation axis. Here, p: the length of the incident surface of the central radiation detection element in one of the two directions perpendicular to each other, which is back-projected to the position of the rotation axis along the path of the radiation beam. Number of detection element rows i: 1 to int {(n + 1) / 2} (2) According to a second aspect of the present invention for solving the above-described problem, the first and second directions are perpendicular to the irradiation direction and perpendicular to each other. A fan-shaped radiation beam having a width and a thickness is irradiated from the radiation irradiating means, and a detection element row in which a plurality of radiation detection elements are arranged in a direction of the width of the radiation beam with an incident surface directed in a direction in which the radiation beam is incident. The radiation The radiation beam is detected by a detection element array arranged in the direction of the thickness of the beam, and the radiation irradiation / detection system including the radiation irradiation means and the detection element array is rotated perpendicularly to the fan plane of the radiation beam. A radiation tomography method for generating a tomographic image of a slice through which the radiation beam has passed based on radiation detection signals of a plurality of views obtained by rotating about an axis, wherein the radiation irradiating unit includes the plurality of detection elements. A straight line i connecting the plurality of focal points corresponding to the rows and the centers of the respective central radiation detection elements in the plurality of detection element rows is substantially the following along the direction of the width of the radiation beam from the rotation axis. Irradiating the radiation beams from the plurality of focal points to the plurality of detection element rows, respectively, in a geometric relationship passing through a place separated by a distance d Detecting a radiation detection signal for the same slice in each of the plurality of detection element rows, and generating a tomographic image based on a radiation detection signal obtained by combining all of the radiation detection signals from the plurality of detection element rows. Radiation tomography method.

When n is an odd number, symmetrically on both sides with respect to the rotation axis, d = 4ip / 4n i: 0 to int (n / 2) When n is an even number, symmetrically on both sides with respect to the rotation axis, d = (4i + 2) p / 4n i: 0 to int (n / 2-1), where p is one of the two directions perpendicular to each other, which are back-projected to the position of the rotation axis along the path of the radiation beam. The length of the incident surface of the central radiation detection element in n: the number of the plurality of detection element rows (3) The third invention for solving the above-mentioned problem is the two inventions which are perpendicular to the irradiation direction and perpendicular to each other. Radiation irradiating means for irradiating a fan-shaped radiation beam having a width and a thickness in one and the other direction, and a plurality of radiation detection elements having a light incident surface directed in a direction in which the radiation beam is incident. Distributed to A detection element array in which a plurality of detection element rows are arranged in the direction of the thickness of the radiation beam, and a radiation irradiation / detection system including the radiation irradiation means and the detection element array is perpendicular to a fan surface of the radiation beam. Signal collecting means for rotating around a rotation axis to collect radiation detection signals of a plurality of views, and a tomogram for generating a tomographic image of a slice through which the radiation beam has passed based on the radiation detection signals collected by the signal collecting means Image generating means, and wherein the radiation irradiating means includes a plurality of focal points corresponding to the plurality of detection element rows and a center of each central radiation detection element in the plurality of detection element rows. And passes through a position substantially apart from the rotation axis by the following distance d along the direction of the width of the radiation beam. In a geometrical relationship, the radiation beam is applied to each of the plurality of detection element rows from the plurality of focal points, and the signal collection unit outputs radiation detection signals for the same slice in the plurality of detection element rows, respectively. Radiation, wherein the tomographic image generating means generates a tomographic image based on a radiation detection signal obtained by combining all of the radiation detection signals from the plurality of detection element arrays. It is a tomography apparatus.

In the range of d <p / 2, d = (4i-1) p / 4n on one side with respect to the rotation axis, and d = (4i-3) p / 4n on the other side with respect to the rotation axis. Here, p: the length of the incident surface of the central radiation detection element in one of the two directions perpendicular to each other, which is back-projected to the position of the rotation axis along the path of the radiation beam. Number of detection element rows i: 1 to int {(n + 1) / 2} (4) According to a fourth aspect of the present invention for solving the above-described problem, the first and second directions are perpendicular to the irradiation direction and perpendicular to each other. Radiation irradiating means for irradiating a fan-shaped radiation beam having a width and a thickness, and a detection element array in which a plurality of radiation detection elements are arranged in a direction of the width of the radiation beam with an incident surface directed in a direction in which the radiation beam is incident. The radiation A plurality of detection element arrays arranged in the direction of the thickness of the beam, and a radiation irradiation / detection system including the radiation irradiation means and the detection element array, which is rotated around a rotation axis perpendicular to a fan surface of the radiation beam. Radiation having signal collecting means for collecting radiation detection signals of a plurality of views, and tomographic image generating means for generating a tomographic image of a slice through which the radiation beam has passed based on the radiation detection signals collected by the signal collecting means. In the tomography apparatus, the radiation irradiating means may include a straight line i connecting a plurality of focal points corresponding to the plurality of detection element rows and a center of each central radiation detection element in the plurality of detection element rows. The geometrical relationship passing through a distance d substantially below in the direction of the width of the radiation beam from the axis of rotation. Irradiating the radiation beam to each of the plurality of detection element rows from a focal point, wherein the signal collecting means collects radiation detection signals for the same slice in the plurality of detection element rows, respectively, The radiation tomography apparatus is characterized in that the generation means generates a tomographic image based on a radiation detection signal obtained by combining all the radiation detection signals from the plurality of detection element arrays.

When n is an odd number, symmetrically on both sides with respect to the rotation axis, d = 4ip / 4n i: 0 to int (n / 2) When n is an even number, symmetrically on both sides with respect to the rotation axis, d = (4i + 2) p / 4n i: 0 to int (n / 2-1), where p is one of the two directions perpendicular to each other, which are back-projected to the position of the rotation axis along the path of the radiation beam. N: the number of the plurality of detection element rows in the first invention or the third invention, the combination of the radiation detection signals includes interleaving of facing view data. This is preferable in that the spatial resolution of the reconstructed image is further improved.

In any one of the first to fourth inventions, it is preferable that the detection of the radiation detection signal for the same slice is performed by a helical scan having a pitch of 1 from the viewpoint of improving scan efficiency.

(5) According to a fifth aspect of the present invention, a radiation beam having a width and a thickness in one of the two directions perpendicular to the irradiation direction and perpendicular to each other, and the radiation surface having the radiation Radiation detected by a detection element array in which a plurality of detection element rows in which a plurality of radiation detection elements are arranged in the direction of the width of the radiation beam in the direction of incidence of the beam are arranged in the direction of the thickness of the radiation beam. A detector, wherein the radiation detecting elements have the same parallelogram-shaped incident surfaces, and are diagonal lines in the direction of the thickness of the radiation beam as a whole that are adjacent to each other in the direction of the thickness of the radiation beam. Forming a parallelogram-shaped entrance surface composed of a combination of two congruent right triangles bounded by the diagonal line. It is a vessel.

(6) According to a sixth aspect of the present invention, there is provided an X-ray tube having a cathode for irradiating an electron beam and a rotating anode for generating X-rays based on the irradiated electron beam. The cathode irradiates the electron beam to a substantially rectangular area where the direction of the major axis crosses the direction of the radius of rotation of the rotating anode on the electron beam irradiation surface of the rotating anode. It is a wire tube.

(Operation) In the first to fourth inventions,
The combination of the fan-shaped radiation beam, the geometry of the plurality of detection element arrays, and the detection signals of all the detection element arrays increases the spatial resolution of the reconstructed image in proportion to the number of detection element arrays.

In the fifth aspect of the present invention, the radiation path between the adjacent detection element rows is changed in the channel width direction by 1 / channel number of the detection element rows depending on the shape of the incident surface of the radiation detection element in the plurality of detection element rows. Deviate.

In the sixth aspect of the present invention, the X-ray tube irradiates X-rays from a plurality of focal points having different positions in the channel width direction to each of the plurality of detection element rows, depending on the shape of the electron beam irradiation area in the rotating anode. It will be.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the X-ray CT apparatus. This apparatus is an example of an embodiment of the radiation tomography apparatus of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

As shown in FIG. 1, this apparatus includes a scanning gantry 2 and a photographing table.
4 and an operation console 6. The scanning gantry 2 has an X-ray tube 20 as a radiation source. X-rays (not shown) emitted from the X-ray tube 20 are:
The collimator 22 shapes the beam into, for example, a fan-shaped X-ray beam, that is, a fan beam, and irradiates the detector array 24 with the beam.

An X-ray beam is an example of an embodiment of a radiation beam according to the present invention. X-ray tube 20 and collimator 2
The portion 2 is an example of the embodiment of the radiation irradiating means in the present invention. The X-ray tube 20 is an example of an embodiment of the X-ray tube of the present invention. The detailed configuration of the X-ray tube will be described later.

The detector array 24 has a plurality of X-ray detecting elements arranged in an array in the direction of the width of the fan-shaped X-ray beam. The detector array 24 is an example of an embodiment of the detection element array of the present invention. The configuration of the detector array 24 will be described later.

The X-ray tube 20, collimator 22 and detector array 24 constitute an X-ray irradiation / detection device. The X-ray irradiation / detection device is an example of an embodiment of a radiation irradiation / detection system according to the present invention. The configuration and the geometry of the X-ray irradiation / detection device will be described later.

The detector array 24 is connected to a data collection unit 26. The data collection unit 26 includes the detector array 24
The detection data of the individual X-ray detection elements are collected.

The irradiation of X-rays from the X-ray tube 20 is controlled by an X-ray controller (controller) 28. The illustration of the connection relationship between the X-ray tube 20 and the X-ray controller 28 is omitted. The collimator 22 is controlled by a collimator controller 30. The illustration of the connection relationship between the collimator 22 and the collimator controller 30 is omitted.

The above-described X-ray tube 20 to collimator controller 30 are mounted on the rotating unit 32 of the scanning gantry 2. The rotation of the rotation unit 32 is controlled by a rotation controller 34. The illustration of the connection relationship between the rotation unit 32 and the rotation controller 34 is omitted.

The imaging table 4 carries a subject (not shown) into and out of the X-ray irradiation space of the scanning gantry 2. The relationship between the subject and the X-ray irradiation space will be described later.

The operation console 6 has a central processing unit 60. The central processing unit 60 is an example of an embodiment of a tomographic image generation unit according to the present invention. Central processing unit 6
0 is constituted by, for example, a computer.

The central processing unit 60 is connected to a control interface (interface) 62. The scanning gantry 2 and the imaging table 4 are connected to the control interface 62.

The central processing unit 60 includes the control interface 6
2, the scanning gantry 2 and the imaging table 4 are controlled. The data acquisition unit 26, X-ray controller 28, collimator controller 30, and rotation controller 34 in the scanning gantry 2 are controlled through a control interface 62. It should be noted that illustration of individual connections between these units and the control interface 62 is omitted. Scan gantry 2 and control interface 62
Is an example of an embodiment of a signal collection unit in the present invention.

A data collection buffer 64 is also connected to the central processing unit 60. Data collection buffer 6
4 is connected to the data collection unit 26 of the scanning gantry 2. The data collected by the data collection unit 26 is input to the data collection buffer 64. Data collection buffer 6
4 temporarily stores the input data.

The central processing unit 60 performs image reconstruction based on data of a plurality of views collected through the data collection buffer 64. The central processing unit 60 is an example of an embodiment of a tomographic image generation unit according to the present invention. The image reconstruction includes, for example, filtered back projection (filtered back projection).
n) method or the like is used. The central processing unit 60 also has:
The storage device 66 is connected. The storage device 66 stores various data, reconstructed images, and programs (programs).
m) and the like are stored.

The central processing unit 60 also includes a display device 6
8 and the operating device 70 are connected to each other. The display device 68 displays a reconstructed image and other information output from the central processing unit 60. Operation device 7
Numeral 0 is operated by the operator to input various instructions and information to the central processing unit 60.

FIG. 2 shows a schematic configuration of the detector array 24. The detector array 24 includes a large number of X-ray detection elements 24.
(Ik) are arranged, and the multi-channel X-ray detector has two rows. The large number of X-ray detection elements 24 (ik) form an X-ray incident surface curved in a cylindrical concave shape as a whole. i is a channel number, for example, i = 1 to 1000
It is. k is a column number, for example, k = 1, 2.

The X-ray detecting element 24 (ik) is composed of, for example, a combination of a scintillator and a photodiode. The present invention is not limited to this, and may be, for example, a semiconductor X-ray detection element using cadmium tellurium (CdTe) or the like, or an ionization box type X-ray detection element using xenon (Xe) gas. X-ray detector 2
4 (ik) is an example of an embodiment of the radiation detecting element in the present invention.

The X-ray detecting elements 24 (ik) each having the same column number k constitute a detecting element row. The detection element row is an example of the embodiment of the detection element row in the present invention. The plurality of detection element rows are adjacently arranged in parallel with each other.

FIG. 3 shows the relationship among the X-ray tube 20, collimator 22, and detector array 24 in the X-ray irradiation / detection device. 3A is a diagram illustrating a state viewed from the front, and FIG. 3B is a diagram illustrating a state viewed from the side. As shown in the figure, the X-rays radiated from the X-ray tube 20 are shaped into a fan-shaped X-ray beam 40 by a collimator 22 and irradiated to a detector array 24.

FIG. 3A shows a fan-shaped X-ray beam 40.
, Ie, the width of the X-ray beam 40. The width direction of the X-ray beam 40 matches the channel arrangement direction (i direction) in the detector array 24. 3B shows the thickness of the X-ray beam 40. The thickness direction of the X-ray beam 40 coincides with the direction (k direction) in which the detector elements are arranged in the detector array 24.

By crossing the body axis with the fan surface of the X-ray beam 40, for example, as shown in FIG.
Is placed in the X-ray irradiation space. X
A projection image of the subject 8 sliced by the line beam 40 is projected on the detector array 24. The thickness of the X-ray beam 40 irradiating the subject 8 is set by adjusting the aperture of the aperture of the collimator 22.

FIGS. 5 and 6 are schematic diagrams showing an example of the geometry of the X-ray irradiation / detection device. FIG. 5 is a front view, FIG.
Is a side view. As shown in both figures, the detector array 24
, Two systems of X-ray beams 452, 47 from two focal points 450, 470.
2, respectively.

In the X-ray irradiation / detection system (A system) including the focal point 450, the X-ray beam 452, and the detection element row 250, a straight line 454 connecting the channel center 252 C of the central channel 252 of the detection element row 250 and the focus point 450 is X
It passes through a position offset from the rotation center (isocenter) 320 of the line irradiation / detection system. The rotation center 320 of the X-ray irradiation / detection system is an example of the embodiment of the rotation axis in the present invention.

The distance of the offset is obtained by calculating the channel width of the center channel 252 converted to the value at the rotation center 320 by p.
Is set to 1/8 of that. The converted channel width p corresponds to a value obtained by back-projecting the channel width of the central channel 252 to the position of the rotation center 320 along the path of the X-ray beam.

In the X-ray irradiation / detection system (B system) including the focal point 470, the X-ray beam 472, and the detection element array 270, a straight line 474 connecting the channel center 272 C of the central channel 272 of the detection element array 270 and the focal point 470 is formed. X
It passes through a place offset from the rotation center 320 of the line irradiation / detection system on the side opposite to the straight line 454. The offset distance is set to be 3/8 of the channel width p of the central channel 272 converted into a value at the rotation center 320.

In such a geometry, when the X-ray irradiation / detection system is rotated by 180 degrees, the geometry shown by a broken line and a two-dot chain line is obtained. In this state, in the A system, a straight line 45 connecting the focal point 450 ′ and the channel center 252 C ′ of the central channel 252 of the detection element array 250.
4 ′ is p symmetrically with respect to the straight line 454 from the rotation center 320.
/ 8 offset, and in the B system, the focus 4
A straight line 474 ′ connecting 70 ′ with the channel center 272 C ′ of the central channel 272 of the detection element row 270 passes through a point symmetrically offset by 3p / 8 from the rotation center 320 with respect to the straight line 474.

The straight lines 454 and 454 ′ are the center lines of the X-ray flux incident on the central channel 252 of the detection element array 250 and represent the X-ray flux. Can obtain X-ray transmission signals different by 2p / 8 in the direction of the channel width. In addition, since the straight lines 474 and 474 ′ are the center lines of the X-ray flux incident on the central channel 272 of the detection element array 270 and represent the X-rays, the path of the X-ray is determined by the same central channel 272 at this time. X-ray transmission signals that differ by 6p / 8 in the direction of the channel width are obtained.

FIG. 7 shows the positional relationship between the center lines 454 and 454 'of the X-ray flux incident on the central channel 252 and the center lines 474 and 474' of the X-ray incident on the central channel 272. This figure shows four X-ray center lines 454, 454 ', 47 near the rotation center 320.
The position relationship between 4,474 'and X-ray beams 452,457
FIG. 4 is an enlarged view when viewed along the irradiation direction of FIG. The center lines 454 to 474 'of the incident X-rays are hereinafter referred to as focus centers (f
ocus center).

As shown in the figure, different positions are set in the imaging range where the channel width is p and the slice thickness is 2t.
There will be one focus center. These four focus centers are arranged at a pitch of p / 4 in the i direction. The arrangement is symmetric about the center of rotation 320. The focus centers 454, 454 'and 474, 47
4 ′ is separated in the k direction by a distance corresponding to the slice thickness t.

The same relationship is obtained by detecting element rows 250,
The other channels in 270 are also formed by so-called opposed views in which the X-ray passing directions are opposite to each other. Then, by interleaving the X-ray detection signals between the opposite views for each channel for each of the A system and the B system, it is possible to obtain the view data having the arrangement schematically shown in FIG.

As shown in the figure, the view data of the A system and the view data of the B system differ in the data collection position by the slice thickness t in the k direction, but are equally spaced at a pitch of p / 4 in the i direction. It will be lined up.

Therefore, the axial scan (axi
al scan), that is, when scanning with the position of the subject 8 fixed, the same slice scanned by the A system is moved by the distance t with the subject 8 and then scanned by the B system (or vice versa). The combined data obtained by interleaving the opposite view data is combined in the same view of both systems in the order of the data arrangement (merge:
merge), as schematically shown in FIG.
It is possible to obtain view data corresponding to data collected at a pitch of p / 4 for the slice thickness t.

As a result, view data having a spatial resolution of four times the channel pitch p can be obtained. By performing image reconstruction using this view data,
A tomographic image whose spatial resolution is improved to four times the channel pitch can be obtained.

When a so-called helical scan is performed in which the subject 8 is continuously moved while continuously rotating the X-ray irradiation / detection system, a helical scan with a pitch of 1 is performed. That is,
By making the moving amount of the subject 8 per rotation of the X-ray irradiation / detection system equivalent to one slice thickness, the spiral trajectory traced by one detection element row is also delayed by one rotation for the next detection element row. It is possible to perform scanning efficiently. Then, by merging the data of both systems obtained in this way, it is possible to obtain view data having a high spatial resolution in the same manner as described above, and reconstruct an image having a high spatial resolution based on the view data.

FIGS. 10 and 11 are schematic diagrams showing other examples of the geometry of the X-ray irradiation / detection device. FIG. 10 is a front view, and FIG. 11 is a side view. As shown in both figures, two detection element rows 250 and 270 in the detector array 24.
Then, two systems of X-ray beams 552 and 572 are irradiated from two focal points 550 and 570, respectively.

In the X-ray irradiation / detection system (A system) including the focal point 550, the X-ray beam 552, and the detecting element array 250, a straight line 554 connecting the channel center 252 C of the central channel 252 of the detecting element array 250 and the focal point 550 is formed. X
It passes through a position offset by a distance p / 4 from the rotation center 320 of the line irradiation / detection system. X-ray irradiation
The rotation center 320 of the detection system is an example of the embodiment of the rotation axis in the present invention.

In the X-ray irradiation / detection system (B system) including the focal point 570, the X-ray beam 572, and the detecting element array 270, a straight line 574 connecting the channel center 272 C of the central channel 272 of the detecting element array 270 and the focal point 570 is X
It passes through a place offset from the rotation center 320 of the line irradiation / detection system by a distance p / 4 on the opposite side to the straight line 554.

FIG. 12 shows a focus center 554 for the X-ray flux incident on the central channel 252 and a focus center 574 for the X-ray flux incident on the central channel 272.
3 shows a positional relationship in the vicinity of the rotation center 320.

As shown in the same drawing, two positions different from each other are set in an imaging range where the channel width is p and the slice thickness is 2t.
There are two focus centers. These two focus centers are arranged at a pitch of p / 2 in the i direction. The arrangement is symmetric about the center of rotation 320. These focus centers 554 and 574 are separated by a distance corresponding to the slice thickness t in the k direction.

A similar relationship is obtained by detecting element rows 250,
The other channels in 270 also hold, and FIG.
The view data of the array as schematically shown in FIG. 3 can be obtained.

As shown in the figure, the view data of the A system and the view data of the B system differ in the data collection position by the slice thickness t in the k direction, but are equally spaced at a pitch of p / 2 in the i direction. It will be lined up.

Accordingly, in the case of the axial scan, the same slice scanned by the A system is moved by the distance t, and then scanned by the B system (or vice versa). By merging in the order of data arrangement between the same views of both systems, it is possible to obtain view data corresponding to data collected at a pitch of p / 2 per slice thickness t, as schematically shown in FIG. it can.

As a result, view data having a spatial resolution twice as large as the channel pitch p can be obtained. By performing image reconstruction using this view data,
A tomographic image having a spatial resolution twice as high as the channel pitch can be obtained. The same applies to the case where a helical scan with a pitch of 1 is performed.

The X-ray irradiation / detection system is not limited to two systems, but may be three or more systems. In FIG.
An example of the arrangement of a focus center in the vicinity of the rotation center when the X-ray irradiation / detection system is three systems is schematically shown. As shown in the figure, in the A system, the X-ray beam 752 irradiates the central channel with the focus center 7.
54 is offset from the center of rotation 320 by 3p / 12 to the right in the figure. As a result, the focus center 754 ′ of the facing view is offset by 3p / 12 to the left of the rotation center 320.

In the B system, the focus center 774 for irradiating the center channel with the X-ray beam 772 is offset from the center of rotation 320 by p / 12 to the left in the figure. As a result, the focus center 774 ′ of the facing view is offset to the right of the rotation center 320 by p / 12.

In the C system, the focus center 794 for irradiating the central channel with the X-ray beam 792 is offset from the center of rotation 320 by 5p / 12 to the left in the figure. As a result, the focus center 794 ′ of the facing view is offset to the right of the rotation center 320 by 5p / 12.

A similar relationship holds for so-called opposite views in which the X-ray passing directions are opposite to each other for the other channels. Therefore, by interleaving the X-ray detection signals for each channel between the opposite views for each of the A to C systems, it is possible to obtain view data having an array as schematically shown in FIG.

As shown in the figure, the view data of the A to C systems are arranged at equal intervals at a pitch of p / 6 in the i direction, although the data collection positions differ by the slice thickness t in the k direction. .

Therefore, in the case of the axial scan, the same slice scanned by the A system is sequentially scanned by the B and C systems by moving the subject 8 by the distance t (the order may be reversed), and the opposite view is obtained. By merging the interleaved collected data in the same data view in the same view of all systems,
As schematically shown in FIG. 7, it is possible to obtain view data corresponding to data collected at a pitch of p / 6 with respect to the slice thickness t.

As a result, view data having a spatial resolution of 6 times the channel pitch p can be obtained, and by performing image reconstruction using this view data,
A tomographic image whose spatial resolution is improved to six times the channel pitch can be obtained. The same applies to the case where a helical scan with a pitch of 1 is performed.

FIG. 18 schematically shows another example of the arrangement of the focus centers in the vicinity of the center of rotation when the X-ray irradiation / detection system is composed of three systems. As shown in the figure, in the A system, the focus center 954 where the X-ray beam 952 irradiates the center channel is offset from the center of rotation 320 by p / 3 to the right in the figure.
In the B-system, the focus center 974 where the X-ray beam 972 irradiates the center channel is made to coincide with the rotation center 320. In the C system, the focus center 994 where the X-ray beam 992 irradiates the center channel is offset from the center of rotation 320 by p / 3 to the left in the drawing.

Since the same relationship holds for the other channels, view data in an array as schematically shown in FIG. 19 can be obtained from the A to C systems. As shown in the figure, the view data of the A to C systems have data collection positions that differ by the slice thickness t in the k direction, but are arranged at equal intervals at a pitch of p / 3 in the i direction.

Therefore, in the case of the axial scan, the same slice scanned by the A system is sequentially scanned by the B and C systems while moving the subject 8 by the distance t (the order may be reversed), and the acquired data is obtained. By merging in the order of data arrangement between the same views of all systems,
As schematically shown in FIG. 20, p /
It is possible to obtain view data corresponding to data collected at a pitch of 3.

As a result, view data having a spatial resolution three times as large as the channel pitch p can be obtained. By performing image reconstruction using this view data,
A tomographic image whose spatial resolution is improved to three times the channel pitch can be obtained. The same applies to the case where a helical scan with a pitch of 1 is performed.

The above is an example of two and three X-ray irradiation / detection systems. In general, when n is a positive integer of 2 or more, n-system X-ray irradiation / detection systems are generally used. In the range, the offset amount d of the focus center of each system does not exceed p / 2, so that d = (4i-1) p / 4n on one side with respect to the rotation axis (1) d = (4i-3) p / 4n (2) where i: 1 to int {(n + 1) / 2}, or when n is an odd number, symmetrically on both sides with respect to the rotation axis, d = 4ip / 4n i: 0 to int (n / 2) (3) When n is an even number, symmetrically on both sides with respect to the rotation axis, d = (4i + 2) p / 4n i: 0 to int (n / 2-1) ( 4)

The above equations (1) and (2) represent the offset amount when a spatial resolution of 2n times the channel pitch p is obtained, and correspond to the examples shown in FIGS. 7 and 15, respectively. Equations (3) and (4) represent the offset amount when obtaining a spatial resolution of n times the channel pitch p, and correspond to the examples shown in FIGS. 12 and 18, respectively.

FIG. 21 shows a schematic configuration of a main part of an example of the X-ray tube 20 which enables the offset of the focus center as described above. 21A is a side view, and FIG. 21B is a front view. As shown in FIG.
de) 200 and the cathode 202
They are provided facing each other in a vacuum tube (not shown). A predetermined high voltage is applied between the rotating anode 200 and the cathode 202. The rotating anode 200 is driven by a driving unit (not shown) and rotates at a high speed. The rotating anode 200 has a slope facing the cathode, and the slope 202 is irradiated with an electron beam accelerated by a high voltage from the cathode 202, and generates an X-ray beam 40 by the collision energy of the electron beam. It has become.

Here, the irradiation region 204 of the electron beam on the surface of the rotating anode 200 has a substantially rectangular shape, and its major axis direction intersects the radial direction of the rotating anode 200. Such a structure can be formed by appropriately determining the shape and position of the cathode 202, for example.

By setting the shape and arrangement of the electron beam irradiation area 204 in this way, the rotating anode 200
A plurality of X-ray focal points whose positions are different from each other in the radial direction and in the direction perpendicular thereto can be formed. The difference in the radial position is a difference in the k direction due to the inclined surface of the rotating anode 200, and the difference in the direction perpendicular thereto is a difference in the i direction. Become.

Therefore, for example, two focal points 450 (550) and 47 satisfying the conditions shown in FIG. 7 or FIG.
0 (570) can be formed. Further, the present invention is not limited to this. For example, three focal points satisfying the conditions shown in FIG. 15 or FIG. 18 can be formed.
It is possible to form n focal points satisfying the conditions of Expressions (4) to (4). It is preferable that the n focal points be individually separated in the k direction by an appropriate collimator.

A single X common to a plurality of X-ray irradiation / detection systems
Even in the case of having a line focus, it is possible to obtain data having a spatial resolution several times the channel pitch by devising the configuration of the plurality of detection element rows. Next, it will be described.

FIG. 22 shows the structure of the X-ray incident surface of the channel when the number of the detection element rows is two. Although FIG. 22 shows a part of the detection element row, the other parts are also the same.

As shown in the figure, each channel of two detection element arrays 250 'and 270' arranged in parallel to each other is configured to have a parallelogram-shaped X-ray incident surface. The channel pitch is p. These X-ray incidence surfaces are adjacent to each other in the k direction, and form a parallelogram 130 as shown by a broken line.

Here, the parallelogram 130 has a shape such that a perpendicular 132 drawn from the left end of the upper side to the lower side in the figure contacts the right end of the lower side. For this reason, those adjacent to each other in the k direction
The center of the line incident surface is shifted by p / 2 in the i direction. In each of the detection element rows, the centers of the channels are arranged at a pitch p in the i direction, so that the centers of the channels of the two detection element rows are arranged at a pitch of p / 2 in the i direction.

The path of the X-ray flux incident on each channel is
As represented by the path of the X-ray incident on the center of the channel, the two detection element arrays detect signals on the X-ray path shifted by p / 2 in the i direction. Therefore, the same slice is sequentially scanned by the two detection element arrays in the same manner as described above, and the collected data is merged, so that
View data equivalent to that collected at p / 2 pitch can be obtained.

FIG. 23 shows a case where the number of detecting element rows is three. In this case, three detection element rows 250 ', 27
The parallelogram X-ray incidence surfaces of the channels 0 'and 290' are adjacent to the k-walk and form a parallelogram 150. The parallelogram 150, like the parallelogram 130, has a shape such that a perpendicular drawn from the left end of the upper side toward the lower side is in contact with the right end of the lower side.

By doing so, the center positions of channels adjacent in the k direction are shifted by p / 3 in the i direction. Therefore, by merging the view data of the same slice obtained by each of these detection element arrays, it is possible to obtain view data corresponding to data collected at a p / 3 pitch.

In general, when n detection element rows 241 to 24n are provided side by side as shown in FIG. 24, the X-ray incidence surface of each channel is a parallelogram having the same shape and size, and May be formed in such a manner that a quadrilateral formed adjacent to the direction in which the rows are arranged has a relationship in which one end of the upper side and the other end of the lower side are connected by a perpendicular when viewed in the direction of the arrangement of the rows. Or, to put it another way, if the composite parallelogram has a diagonal perpendicular to the upper and lower sides and is bisected into two congruent right triangles by the boundary. Good.

The operation of the present apparatus will be described. The operator sets desired photographing conditions through the operation device. Next, the subject 8 is scanned by the X-ray irradiation / detection system under the control of the central processing unit 60. In the case of an axial scan, the subject 8 corresponds to one slice thickness for each scan.
Is stepped in the body axis direction, and the same slice is sequentially scanned by all of the plurality of detection element rows. In the case of a helical scan, a helical scan with a pitch of 1 is performed.

Thus, projection data of, for example, 1000 views is stored in the data collection buffer 64 for each detection element row.
To collect. Thereby, projection data of the subject 8 is collected.

The projection data is obtained by the data collection unit 26.
It is collected as projection data for each detection element row. For such collected data, the central processing unit 60 merges the data as described above. At this time, if the projection data can be interleaved with the facing view data, interleaving is also performed.

For the projection data thus processed, for example, the filtered back projection (f
Image reconstruction is performed by an iltered back projection) method or the like to generate a tomographic image. Thus, a tomographic image having a spatial resolution several times the channel pitch of the detector array can be obtained.

In the above, an example in which X-rays are used as radiation has been described. However, the radiation is not limited to X-rays, and may be other types of radiation such as γ-rays. However,
At present, X-rays are preferred because practical means for generating, detecting, controlling, and the like are the most substantial.

[0100]

As described above in detail, according to the present invention, a radiation tomography method and apparatus for performing radiography with high spatial resolution using a plurality of detection element arrays, and for performing radiography with high spatial resolution. It is possible to realize a suitable radiation detector and an X-ray tube suitable for performing imaging with high spatial resolution.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of a detector array in an apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an X-ray irradiation / detection system in an apparatus according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an X-ray irradiation / detection system in an apparatus according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of the geometry of an X-ray irradiation / detection system detector in the apparatus according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of the geometry of an X-ray irradiation / detection system detector in an apparatus according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of an arrangement of a focus center of an X-ray beam in the apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of an array of focus centers for view data in the apparatus according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of an arrangement of focus centers of view data in the apparatus according to an embodiment of the present invention;

FIG. 10 shows an example of the X in the apparatus according to the embodiment of the present invention.
It is a schematic diagram of the geometry of a line irradiation / detection system detector.

FIG. 11 shows X in the apparatus according to the embodiment of the present invention.
It is a schematic diagram of the geometry of a line irradiation / detection system detector.

FIG. 12 shows X in the apparatus according to an embodiment of the present invention;
It is a schematic diagram of arrangement | positioning of the focus center of a line beam.

FIG. 13 is a schematic diagram of an arrangement of focus centers of view data in the apparatus according to an embodiment of the present invention;

FIG. 14 is a schematic diagram of an array of focus centers for view data in the apparatus according to an embodiment of the present invention;

FIG. 15 shows X in the apparatus according to the embodiment of the present invention.
It is a schematic diagram of arrangement | positioning of the focus center of a line beam.

FIG. 16 is a schematic diagram of an arrangement of focus centers of view data in the device according to an embodiment of the present invention;

FIG. 17 is a schematic diagram of an array of focus centers for view data in the apparatus according to an embodiment of the present invention;

FIG. 18 shows an example of X in the apparatus according to the embodiment of the present invention.
It is a schematic diagram of arrangement | positioning of the focus center of a line beam.

FIG. 19 is a schematic diagram of an array of focus centers for view data in the apparatus according to an embodiment of the present invention;

FIG. 20 is a schematic diagram of an array of focus centers of view data in the apparatus according to an embodiment of the present invention;

FIG. 21 shows an example of the X in the apparatus according to the embodiment of the present invention.
It is a schematic block diagram of the principal part of a wire tube.

FIG. 22 is a schematic configuration diagram of an incident surface of a detector array in an apparatus according to an example of an embodiment of the present invention.

FIG. 23 is a schematic configuration diagram of an incident surface of a detector array in an apparatus according to an embodiment of the present invention.

FIG. 24 is a schematic configuration diagram of an incident surface of a detector array in an apparatus according to an embodiment of the present invention.

FIG. 25 is a schematic diagram of the geometry of an X-ray irradiation / detection system in a conventional device.

[Explanation of symbols]

2 Scanning Gantry 20 X-ray Tube 22 Collimator 24 Detector Array 26 Data Collection Unit 28 X-ray Controller 30 Collimator Controller 32 Rotating Unit 34 Rotation Controller 4 Imaging Table 6 Operation Console 60 Central Processing Unit 62 Control Interface 64 Data Collection Buffer 40 X-ray Beam 8 Subject 24 (ik) X-ray detector 250, 270 Detector array 450, 470 X-ray focus 252, 272 Central channel 454, 454 ', 474, 474' Focus center

Claims (6)

[Claims] 1. A fan-shaped radiation beam having a width and a thickness in one of two directions perpendicular to an irradiation direction and perpendicular to each other is irradiated from a radiation irradiation means, and a direction in which the radiation beam is incident on an incident surface. Detecting the radiation beam with a detection element array in which a plurality of radiation detection elements arranged in the direction of the width of the radiation beam are arranged in the direction of the thickness of the radiation beam; A slice through which the radiation beam has passed based on a radiation detection signal of a plurality of views obtained by rotating a radiation irradiation / detection system including a radiation irradiation unit and the detection element array around a rotation axis perpendicular to a fan surface of the radiation beam. A radiation tomography method for generating a tomographic image of a plurality of detection element arrays, And the straight line i connecting the center of the radiation detection element at the center of each of the plurality of detection element rows is substantially separated from the rotation axis by the following distance d along the direction of the width of the radiation beam. However, in the passing geometrical relationship, the radiation beam is applied to each of the plurality of detection element arrays from the plurality of focal points, and the plurality of detection element arrays respectively detect radiation detection signals related to the same slice. A tomographic image is generated based on a radiation detection signal obtained by combining all the radiation detection signals from the detection element arrays. In the range of d <p / 2, d = (4i-1) p / 4n on one side with respect to the rotation axis, and d = (4i-3) p / 4n on the other side with respect to the rotation axis. : Length of the incident surface of the central radiation detection element in one of the two directions perpendicular to each other, which is back-projected to the position of the rotation axis along the path of the radiation beam. N: the plurality of detection element rows I: 1 to int {(n + 1) / 2} 2. A fan-shaped radiation beam having a width and a thickness in one of two directions perpendicular to an irradiation direction and perpendicular to each other is irradiated from a radiation irradiation means, and a direction in which the radiation beam is incident on an incident surface. Detecting the radiation beam with a detection element array in which a plurality of radiation detection elements arranged in the direction of the width of the radiation beam are arranged in the direction of the thickness of the radiation beam; A slice through which the radiation beam has passed based on a radiation detection signal of a plurality of views obtained by rotating a radiation irradiation / detection system including a radiation irradiation unit and the detection element array around a rotation axis perpendicular to a fan surface of the radiation beam. A radiation tomography method for generating a tomographic image of a plurality of detection element arrays, And the straight line i connecting the center of the radiation detection element at the center of each of the plurality of detection element rows is substantially separated from the rotation axis by the following distance d along the direction of the width of the radiation beam. However, in the passing geometrical relationship, the radiation beam is applied to each of the plurality of detection element arrays from the plurality of focal points, and the plurality of detection element arrays respectively detect radiation detection signals related to the same slice. A tomographic image is generated based on a radiation detection signal obtained by combining all the radiation detection signals from the detection element arrays. When n is an odd number, symmetrically on both sides with respect to the rotation axis, d = 4ip / 4n i: 0 to int (n / 2) When n is an even number, symmetrically on both sides with respect to the rotation axis, d = (4i + 2) ) P / 4n i: 0 to int (n / 2-1), where: p: the center in one of the two mutually perpendicular directions, which is back-projected to the position of the rotation axis along the path of the radiation beam. Length of the incident surface of the radiation detecting element of n: number of the plurality of detecting element rows 3. A radiation irradiating means for irradiating a fan-shaped radiation beam having a width and a thickness in one of two directions perpendicular to an irradiation direction and perpendicular to each other, and a direction in which the radiation beam is incident on an incident surface. A detecting element array in which a plurality of detecting element rows in which a plurality of radiation detecting elements are arranged in the direction of the width of the radiation beam toward the direction of the radiation beam; A signal collection unit configured to rotate a radiation irradiation / detection system including an element array around a rotation axis perpendicular to a fan surface of the radiation beam and collect radiation detection signals of a plurality of views; and the radiation detection signals collected by the signal collection unit. A tomographic image generating means for generating a tomographic image of a slice through which the radiation beam has passed based on the tomographic image. The radiation irradiating means includes a straight line i connecting each of the plurality of focal points corresponding to the plurality of detection element rows and the center of each central radiation detection element in the plurality of detection element rows.
The radiation passes from the plurality of focal points to the plurality of detection element rows in a geometric relationship in which the radiation passes from the rotation axis substantially along the width direction of the radiation beam at a distance d described below. The signal collecting means collects radiation detection signals related to the same slice in the plurality of detection element arrays, respectively, and the tomographic image generation means performs radiation by the plurality of detection element arrays. A radiographic tomography apparatus for generating a tomographic image based on a radiation detection signal obtained by combining all the detection signals. In the range of d <p / 2, d = (4i-1) p / 4n on one side with respect to the rotation axis, and d = (4i-3) p / 4n on the other side with respect to the rotation axis. : Length of the incident surface of the central radiation detection element in one of the two directions perpendicular to each other, which is back-projected to the position of the rotation axis along the path of the radiation beam. N: the plurality of detection element rows I: 1 to int {(n + 1) / 2} 4. A radiation irradiating means for irradiating a fan-shaped radiation beam having a width and a thickness in one of two directions perpendicular to the irradiation direction and perpendicular to each other, and a direction in which the radiation beam is incident on an incident surface. A detecting element array in which a plurality of detecting element rows in which a plurality of radiation detecting elements are arranged in the direction of the width of the radiation beam toward the direction of the radiation beam; A signal collection unit configured to rotate a radiation irradiation / detection system including an element array around a rotation axis perpendicular to a fan surface of the radiation beam and collect radiation detection signals of a plurality of views; and the radiation detection signals collected by the signal collection unit. A tomographic image generating means for generating a tomographic image of a slice through which the radiation beam has passed based on the tomographic image. The radiation irradiating means includes a straight line i connecting each of the plurality of focal points corresponding to the plurality of detection element rows and the center of each central radiation detection element in the plurality of detection element rows.
Are transmitted from the plurality of focal points to the plurality of detection element arrays in a geometric relationship in which the radiation passes from the axis of rotation substantially along the direction of the width of the radiation beam by a distance d described below. The signal collecting means collects radiation detection signals relating to the same slice in the plurality of detection element arrays, respectively, and the tomographic image generation means performs radiation by the plurality of detection element arrays. A radiographic tomography apparatus for generating a tomographic image based on a radiation detection signal obtained by combining all the detection signals. When n is an odd number, symmetrically on both sides with respect to the rotation axis, d = 4ip / 4n i: 0 to int (n / 2) When n is an even number, symmetrically on both sides with respect to the rotation axis, ) P / 4n i: 0 to int (n / 2-1), where: p: the center in one of the two mutually perpendicular directions, which is back-projected to the position of the rotation axis along the path of the radiation beam. Length of the incident surface of the radiation detecting element of n: number of the plurality of detecting element rows 5. A plurality of radiation detecting elements, wherein a radiation beam having a width and a thickness in each of two directions perpendicular to the irradiation direction and perpendicular to each other is directed to an incident surface in a direction in which the radiation beam is incident. A detection element array arranged in the direction of the width of the radiation beam by a detection element array formed by arranging a plurality of detection element rows in the direction of the thickness of the radiation beam, wherein the radiation detection elements are the same as each other. Have a parallelogram-shaped incident surface, and further, those which are adjacent to each other in the direction of the thickness of the radiation beam have a diagonal line in the direction of the thickness of the radiation beam as a whole and have two congruent right angles bounded by the diagonal line. A radiation detector, which forms a parallelogram-shaped incident surface composed of a combination of triangles. 6. An X-ray tube having a cathode for irradiating an electron beam and a rotating anode for generating X-rays based on the irradiated electron beam, wherein the cathode is long on an electron beam irradiation surface of the rotating anode. An X-ray tube for irradiating the electron beam to a substantially rectangular area whose axial direction intersects the direction of the radius of rotation of the rotating anode.