JP2000296124A - Method and system for radiation tomographic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation of image quality by linearly correcting a radioactive ray detecting signal according to an irradiation position error in a radioactive ray beam in a detecting element array, and reducing weight of the radioactive ray detecting signal having a large residual error after linear correction on radioactive ray detecting signals of plural views. SOLUTION: An X-ray beam 40 having a width and a thickness in one and the other of the mutually vertical two directions vertical to the irradiating direction is irradiated from an X-ray tube 20 so that the X-ray beam 40 is detected by a detector array 24 by arranging plural X-ray detectors 242, 244 in the width direction and the thickness direction of the X-ray beam 40. A tomographic image is formed on the basis of X-ray detecting signals of plural views obtained by rotating this X-ray irradiating/detecting system. At this time, the X-ray detecting signals are linearly corrected according to an irradiation position error in the X-ray beam in the arranging direction of a detector train to reduce weight of the X-ray detecting signal having a large residual error after lenear correction as well as to increase weight of the X-ray detecting signal of an opposed view of the X-ray detecting signal having a large residual error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation tomography method and apparatus, and more particularly, to a radiation beam having a width and a thickness, and a radiation element array in which a plurality of radiation detection elements are arranged in the width direction of the radiation beam. Radiation tomography method using a plurality of detection element arrays arranged in the direction of the thickness of the beam, and irradiation position control means for controlling the irradiation position of the radiation beam in the arrangement direction of the detection element arrays in the detection element array And equipment.

[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 opening of the X-ray passing aperture (aperture) of the collimator, thereby adjusting the thickness of the slice for imaging.

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.

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.

Some X-ray detectors have an array of X-ray detection elements in two rows so that projection data for two slices can be obtained at one time. There, two rows of arrays are arranged adjacent to and parallel to each other, and the X-ray beam is uniformly distributed in the thickness direction and irradiated. The thickness of the X-ray beam applied to the two rows of arrays at the isocenter of the subject determines the slice thickness of the tomographic image.

In the X-ray tube, the focal point of the X-ray moves due to thermal expansion or the like due to a rise in temperature during use, which appears as a displacement in the thickness direction of the X-ray beam through the aperture of the collimator. When the X-ray beam is displaced in the thickness direction, 2
The distribution ratio of the thickness of the X-ray beam in the row array changes, and the slice thickness of the subject projected on the two arrays is not uniform.

Therefore, reference channels provided in the two-row array are respectively provided.
monitor the ratio of x-ray counts
Since the ratio is no longer 1, the deviation of the X-ray irradiation position is recognized, and the position of the collimator is adjusted to control the X-ray irradiation position to be a fixed position.

[0010]

The above-described irradiation position control starts at the same time as X-ray irradiation, that is, at the start of scanning. However, from the start of scanning due to the delay of the response of the control system, until the X-ray irradiation position coincides with the home position. Takes a certain amount of time, and the quality of the initially obtained image is poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to realize a radiation tomography method and apparatus for obtaining a high-quality image from the beginning of scanning.

[0012]

Means for Solving the Problems (1) The invention according to a first aspect for solving the above problems has a width and a thickness in one and the other of two directions perpendicular to the irradiation direction and perpendicular to each other. A radiation beam is irradiated from the radiation irradiating means, and a plurality of radiation detection elements are arranged in the direction of the width of the radiation beam. Detecting a radiation beam, controlling an irradiation position of the radiation beam in an arrangement direction of the detection element array in the detection element array, and setting a radiation irradiation / detection system including the radiation irradiation means and the detection element array to the radiation irradiation; The slice through which the radiation beam has passed based on the radiation detection signals of multiple views obtained by rotating about a rotation axis parallel to the direction of the beam thickness A radiation tomography method for generating a tomographic image, wherein the radiation detection signal of the radiation detection element is linearly corrected according to an irradiation position error of the radiation beam in a direction in which the detection element array is arranged in the detection element array. For the radiation detection signals of the plurality of views, the weight of the radiation detection signal having a large residual error after the linear correction is reduced, and the weight of the radiation detection signal of the opposite view of the radiation detection signal having a large residual error after the linear correction is reduced. Is a radiographic tomography method characterized by increasing.

(2) The invention according to a second aspect for solving the above-mentioned problems is directed to a method of irradiating a radiation beam having a width and a thickness in each of two directions perpendicular to an irradiation direction and perpendicular to each other. Irradiating means, 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 are arranged in the direction of the thickness of the radiation beam, and An irradiation position control means for controlling an irradiation position of the radiation beam in a direction in which the detection element rows are arranged, and a radiation irradiation / detection system including the radiation irradiation means and the detection element array being parallel to the direction of the thickness of the radiation beam. Signal collection means for rotating around a rotation axis and collecting radiation detection signals of a plurality of views; and A tomographic image generating means for generating a tomographic image of a slice through which the beam has passed, wherein the irradiation position error of the radiation beam in the arrangement direction of the detection element array in the detection element array is reduced. Linear correction means for linearly correcting the radiation detection signal of the radiation detection element in response thereto, and for the radiation detection signals of the plurality of views, the weight of the radiation detection signal having a large residual error after the linear correction is reduced, and the linear correction is performed. A radiation tomography apparatus comprising: weighting means for increasing the weight of the radiation detection signal in the opposite view of the radiation detection signal having a large residual error.

(Function) In the present invention, a radiation detection signal is linearly corrected in accordance with an irradiation position error of a radiation beam in a detection element array, and a radiation detection signal having a large residual error after a linear correction is applied to radiation detection signals of a plurality of views. The weight of the signal is reduced and the weight of the radiation detection signal of the opposite view is increased, thereby preventing the deterioration of the image quality due to the irradiation position error of the radiation beam.

[0015]

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 device is an example of an embodiment 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, the present apparatus comprises a scanning gantry (gantry) 2 and a photographing table (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.
The X-ray beam is an example of the embodiment of the radiation beam in the present invention. The portion composed of the X-ray tube 20 and the collimator 22 is an example of the embodiment of the radiation irradiating means in the present invention.

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 of the X-ray irradiation / detection device will be described later. A data collection unit 26 is connected to the detector array 24. Data collection unit 2
6 collects the detection data of the individual X-ray detection elements of the detector array 24.

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
It is controlled by the 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 has a 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 these components and the control interface 62
The illustration of the individual connection with is omitted. The scanning gantry 2 and the control interface 62 are an example of an embodiment of a signal collecting unit according to the present invention. The part including the central processing unit 60, the control interface 62, and the collimator controller 30 is an embodiment of the irradiation position control means in the present invention.

A data acquisition 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 corrects data of a plurality of views collected through the data collection buffer 64 as described later, and reconstructs an image based on the corrected view data. The correction of view data includes linear correction and weighting correction. The central processing unit 60
5 is an example of an embodiment of a linear correction unit according to the present invention. It is also an example of an embodiment of the weighting means in the present invention. Also, it is an example of an embodiment of the tomographic image generating means in the present invention.

The image reconstruction includes, for example, a filtered back projection (filtered back projection).
(projection) method or the like is used. The storage device 66 is connected to the central processing unit 60. Storage device 6
6 shows various data, reconstructed images and programs (p.
program) is stored.

A display device 68 and an operation device 70 are further connected to the central processing unit 60. The display device 68 displays a reconstructed image output from the central processing unit 60 and other information. The operating device 70 is operated by an operator and transmits various instructions and information to the central processing unit 6.
Enter 0.

FIG. 2 shows a schematic configuration of the detector array 24. The detector array 24 forms two rows of multi-channel X-ray detectors 242 and 244 in which a large number (for example, about 1000) of X-ray detection elements 24 (i) are arranged in an arc shape. i is a channel number, for example, i = 1 to 100
0.

The X-ray detecting element 24 (i) 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 chamber type X-ray detection element using xenon (Xe) gas. X-ray detection element 24
(I) is an example of an embodiment of a radiation detection element according to the present invention.

The X-ray detectors 242 and 244 are adjacent to each other in parallel. A predetermined number of channels at both ends of the detector array 24 are each a reference channel in each column. The reference channel is outside the range where the subject is projected during imaging.

FIG. 3 shows the relationship among the X-ray tube 20, collimator 22, and detector array 24 in the X-ray irradiation / detection device. (A) of the same figure is a front view, (b) is a side view. Here, three coordinate axes perpendicular to each other in a geometric space formed by the X-ray irradiation / detection device are defined as x, y, and z. The same applies to other figures shown below. As shown in the figure, the X-ray emitted from the X-ray tube 20 is
Is shaped into a fan-shaped X-ray beam 40, and is irradiated on the detector array 24. FIG. 3A shows the spread of the fan-shaped X-ray beam 40, that is, the width of the X-ray beam 40. The fan surface of the X-ray beam 40 is parallel to the xy plane.
FIG. 3B shows the thickness of the X-ray beam 40. The X-ray beam 40 is applied to two rows of X-ray detectors 242 and 244 with uniform thickness distribution. The thickness direction of the X-ray beam 40 is the z direction. The z direction is also the direction of the rotation axis of the X-ray irradiation / detection device.

By crossing the body axis with the fan surface of such an X-ray beam 40, for example, as shown in FIG.
Is placed in the X-ray irradiation space. The body axis of the subject 8 matches the z direction. X-ray beam 40
The projection image of the subject 8 sliced by the above is projected on the detector array 24. Each half of the thickness of the X-ray beam 40 at the isocenter of the subject 8 gives two slice thicknesses th of the subject 8. Slice thickness th
Is determined by the aperture of the collimator 22.

X-ray beam 40 for detector array 24
FIG. 5 shows a more detailed schematic diagram of the irradiation state of FIG. As shown in FIG.
By displacing 0,222 in the direction to narrow the aperture, the slice thickness th of the projected image in the X-ray detectors 242,244 is reduced. Also, the collimator pieces 220,
By moving 222 in the direction that widens the aperture,
The slice thickness th of the projected image is increased. In addition, by simultaneously moving the collimator pieces 220 and 222 in which the slice thickness th is set in the z direction while maintaining the relative positional relationship, the irradiation position in the z direction on the detector array 24 is adjusted. Such slice thickness adjustment and irradiation position adjustment are performed by the collimator controller 30.

The irradiation position in the z direction is detected based on the output ratio of two rows of reference channels in the detector array 24, and based on this detection signal, the slice thickness is made uniform on the two detector rows. The position of the collimator 22 is adjusted. Thus, the change of the irradiation position due to the movement of the focal point of the X-ray tube is corrected, and the automatic control is performed so that the X-ray beam 40 is always irradiated to the fixed position.

The adjustment of the irradiation position in the z direction is performed by displacing the detector array 24 relative to the collimator 22 in the z direction as indicated by a broken arrow, instead of moving the collimator pieces 220 and 222. You may do it.
In this way, two separate systems for adjusting the slice thickness and controlling the irradiation position in the thickness direction can be provided.
Multilateral control becomes possible.

On the other hand, if all the operations are performed by the collimator 22 as described above, the control system can be unified into one system, and it is possible to meet the demand for simplifying the configuration. It is needless to say that the irradiation position may be adjusted by combining these two means. Hereinafter, the automatic control function of the irradiation position is referred to as an auto collimator.

The X-ray irradiating / detecting device comprising the X-ray tube 20, the collimator 22, and the detector array 24 rotates around the body axis of the subject 8 while maintaining their mutual relation (sc).
an). Multiple scans per scan (e.g., 10
Projection data of the subject is collected at a view angle of about 00). The collection of projection data is performed by a system including the detector array 24, the data collection unit 26, and the data collection buffer 64.

Based on the projection data of two slices collected in the data collection buffer 64, the central processing unit 60 generates tomographic images of two slices, that is, performs image reconstruction. Image reconstruction is performed, for example, by using projection data of, for example, 1000 views obtained by one rotation scan, for example, with filtered back projection (filteredba).
The processing is performed by, for example, a ck-projection method.

During scanning, the X-ray focal point moves due to an increase in the temperature of the X-ray tube 20 or the like, but the X-ray irradiation position on the detector array 24 is kept constant by the autocollimator. When the scan is completed, the collimator 22 remains at the control position immediately before the end of the scan. This position corresponds to the X-ray focal position immediately before the end of the scan.

This position is the initial position of the autocollimator at the time of the next scan. However, if time elapses before the next scan, the X-ray tube 20 cools and the position of the X-ray focal point changes. The position will not fit. At the start of the next scan, adjustment for adjusting the X-ray irradiation position to the home position by the autocollimator starts, but the irradiation position error continues to be large until it is settled.

The central processing unit 60 performs data correction for minimizing the influence on the reconstructed image in such a case. This will be described below. Data correction is performed in two stages. The first stage is a linear correction. The second stage is weighting correction.

First, the linear correction will be described. This corrects the view data in proportion to the amount of displacement of the X-ray irradiation position from the fixed position. Hereinafter, the X-ray irradiation position is simply referred to as an irradiation position. The correction coefficient proportional to the amount of displacement, that is, the linear correction coefficient is obtained by individually calibrating the X-ray detection elements 24 (i) in the detector array 24 in advance (cal
ibration). The calibration is performed without the subject 8. That is, so-called air calibration (aircali)
b.).

The air calibration of the X-ray detecting element 24 (i) will be described with reference to FIGS. First, the X-ray detection data of each X-ray detection element 24 (i) in the two X-ray detectors 242 and 244 in a state where the X-ray beam 40 is irradiated to a regular position (fixed position) as shown in FIG. To collect. The X-ray detection data collected at this time is defined as Dci.
Hereinafter, the X-ray detection data is simply referred to as data.

Next, the position of the collimator 22 in the z direction is adjusted so that the irradiation position of the X-ray beam 40 is shifted toward the X-ray detector 242 by a predetermined distance as shown in FIG. Perform similar data collection. The deviating distance is a distance that does not exceed the slice thickness. The direction of the deviation at this time is called a forward direction, and is represented by a negative sign.
The data collected at this time is defined as Dfi.

Next, the position of the collimator 22 in the z direction is adjusted, and as shown in FIG.
The same data collection is performed in a state where the data is biased toward the fourth side by a predetermined distance. The deviating distance is a distance that does not exceed the slice thickness. The direction of the deviation at this time is defined as backward (back
(ward) direction and a positive sign. The data collected at this time is defined as Dbi.

As a result, for example, three data Dfi, Dci, Dbi having a relationship as shown in FIG. 8 are obtained for each of the X-ray detection elements 24 (i). Data Df
The relationship between i, Dci, and Dbi depends on the individual X-ray detection elements 24.
It is determined according to the sensitivity distribution in the z direction of (i). FIG.
Indicates the tendency of data in the X-ray detection element 24 (i) on the X-ray detector 242 side. The data in the X-ray detection element 24 (i) on the X-ray detector 244 side has the opposite tendency.

The central processing unit 60 stores the data Dfi, Dc
The data change due to the forward shift of the irradiation position is approximated by a straight line connecting i, and the data change due to the backward shift of the irradiation position is approximated by a straight line connecting the data Dci and Dbi. Then, the view data at the time of scanning is linearly corrected along these straight lines according to the magnitude of the irradiation position error given from the detection unit of the autocollimator. The coefficient for linear correction is obtained by the following equation.

[0047]

(Equation 1)

[0048]

(Equation 2)

Here, Qfi: forward correction coefficient Δzf: forward shift at Dfi measurement Qbi: backward correction coefficient Δzb: backward shift at Dbi measurement Linear correction of view data using these correction coefficients is performed by the following equation. Will be

[0050]

(Equation 3)

[0051]

(Equation 4)

Here, Dm'ij: view data after correction (j: view number) Dmij: view data before correction (j: view number) Δz: irradiation position error Next, weighting correction will be described. Since the actual change of the data based on the transition is represented by, for example, curves F and B, the data after the linear correction includes the residual error Δe. This residual error is a difference between the curves F and B and their approximate straight lines, and is as shown in FIG. 9, for example.

For this reason, if the irradiation position error Δz as shown in FIG. 10A occurs at the beginning of scanning due to the settling delay of the autocollimator, for example, the residual error as shown in FIG. Δe occurs. Then, the central processing unit 60, for example, as shown in (c),
The weight w of the view data is set to be smaller than 1 for a view having a large initial irradiation position error Δz, that is, a view having a large residual error Δe. Accordingly, the weight w of the view data is set to be larger than 1 for the opposite view of those views. The opposing view is a view in which the transmission directions of X-rays are opposite to each other. The weight w is set to 1 for other view data.

The weight coefficient is, for example, as shown in FIG.
Based on a known settling time of the autocollimator, it shall gradually increase from 0 to 1 for views obtained within a certain period of the initial period of the scan, and gradually decrease from 2 to 1 for the opposite view accordingly. The table of weighting data (tabl)
This is preferable in that e) is simplified.

In this case, as shown by a broken line, it is preferable to gradually increase the weight w from the view before the opposite view in order to avoid a sudden change in the weight w. In this case, the weight w is gradually reduced from 1 to 0 for the view opposite to the view whose weight w is gradually increased.

Alternatively, the opposing view data may be linearly (li) depending on the distance from the center position.
(near) interpolation may be used to interpolate data. In this case, the center channel weighting pattern (patte)
rn) is 1 in the central view as shown by the one-dot line, and on both sides thereof, the pattern changes linearly to 0 in a bilaterally symmetrical manner. This is a so-called helical scan (h) in which the subject 8 is scanned while being continuously fed in the z direction.
The data is common to the weight data obtained when an electronic scan is performed. Therefore, it is preferable in that it is not necessary to have a new weight data table by sharing it. When a helical scan is performed, the weighting of the initial data of the scan is naturally corrected by the weighting of the view data.

The operation of the present apparatus will be described. The operation of this device proceeds under the control of the central processing unit 60 based on an instruction from the operator. The operator inputs shooting conditions through the operation device 70. The imaging conditions include tube voltage, tube current, slice thickness, slice position, scan time, and the like. Hereinafter, the autocollimator will be described as an example of adjusting the position of the collimator 22, but the same applies to the case where the position of the detector array 24 is adjusted or the positions of the collimator 22 and the detector array 24 are adjusted.

Scanning starts after positioning of the imaging table 4 on which the subject 8 is mounted based on a command from the operator. That is, the rotating unit 32 of the scanning gantry 2 rotates and X
A line is illuminated. The irradiation position control by the autocollimator is started with the start of the scan.

The central processing unit 60 performs the above-described linear correction and weighting correction on the view data collected by scanning. If the scan is performed without a delay from the end of the previous scan, the collimator 2
Since the initial position 2 is adapted to the current position of the X-ray focal point, the above-described data correction is omitted.

The central processing unit 60 performs image reconstruction using such corrected view data or view data from which correction has been omitted. Image reconstruction is performed by processing view data by, for example, a filtered back projection method. A tomographic image of the subject 8 is obtained by image reconstruction. Since the above-described data correction performs weight reduction for reducing the error of the view data and reducing the influence of the error in the initial view data of the scan, a reconstructed image of high quality can be obtained from the beginning of the scan.

Since the detector array 24 has two parallel rows of X-ray detectors, tomographic images of two adjacent slices can be obtained at once by one scan. Thereby, a multi-slice scan (multi-sli) is performed.
The efficiency in performing ce scan or helical scan is improved. The reconstructed image is displayed on the display device 68 and stored in the storage device 66.

Although the example in which the detector array includes two rows of X-ray detectors has been described above, the detector array may be a multi-row of three or more rows. Also, an example in which X-rays are used as radiation has been described, but the radiation is not limited to X-rays, and may be other types of radiation such as, for example, γ-rays.
However, at present, X-rays are preferable because practical means regarding generation, detection, control, and the like are the most substantial.

[0063]

As described above in detail, according to the present invention, it is possible to realize a radiation tomography method and apparatus for obtaining a high-quality image from the beginning of scanning.

[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 view of a detector array in the apparatus shown in FIG.

FIG. 3 is a schematic diagram of an X-ray irradiation / detection device in the device shown in FIG.

FIG. 4 is a schematic view of an X-ray irradiation / detection device in the device shown in FIG.

FIG. 5 is a schematic diagram showing an X-ray irradiation state in the apparatus shown in FIG.

FIG. 6 is a schematic diagram showing an X-ray irradiation state in the apparatus shown in FIG.

FIG. 7 is a schematic diagram showing an X-ray irradiation state in the apparatus shown in FIG.

FIG. 8 shows the X obtained in the X-ray irradiation state shown in FIGS.
It is a graph which shows an example of line detection data.

9 is a graph showing an example of a residual error of linear correction in the device shown in FIG.

FIG. 10 is a graph illustrating weighting correction in the device shown in FIG. 1;

[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 Rotation Unit 34 Rotation Controller 4 Imaging Table 6 Operation Console 60 Central Processing Unit 62 Control Interface 64 Data Collection Buffer 66 Storage Device 68 display device 70 operating device 242, 244 X-ray detector 40 X-ray beam 8 subject 220, 222 collimator piece

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C093 AA22 BA03 BA10 BA13 CA08 CA09 EA02 EA14 EB13 EB18 FA16 FA32 FA54 FC15 FC16 FC27 FD01 FD11 FD12 FD13 FD20

Claims (2)

[Claims] 1. A radiation beam irradiating a radiation beam having a width and a thickness in one of two directions perpendicular to each other and perpendicular to an irradiation direction from a radiation irradiation unit, and a plurality of radiation detection elements are adjusted to a width of the radiation beam. The radiation beam is detected by a detection element array in which a plurality of detection element rows arranged in a direction are arranged in the direction of the thickness of the radiation beam, and the detection element array in the detection element array is arranged in a direction in which the detection element rows are arranged. Controlling the irradiation position of the radiation beam, and a plurality of views of radiation obtained by rotating the radiation irradiation / detection system including the radiation irradiation means and the detection element array around a rotation axis parallel to the thickness direction 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 a detection signal, the method comprising: (B) linearly correcting the radiation detection signal of the radiation detection element according to the irradiation position error of the radiation beam in the direction of disposition of the detection element row in (a), and for the radiation detection signals of the plurality of views, remaining after the linear correction A radiation tomography method, comprising: reducing the weight of a radiation detection signal having a large error and increasing the weight of a radiation detection signal of a view opposite to the radiation detection signal having a large residual error after the linear correction. 2. A radiation irradiating means for irradiating a 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 plurality of radiation detecting elements each having a width of the radiation beam. A detection element array in which a plurality of detection element arrays arranged in the direction are arranged in the direction of the thickness of the radiation beam, and the irradiation position of the radiation beam in the arrangement direction of the detection element arrays in the detection element array. An irradiation position control unit for controlling, and a radiation irradiation / detection system including the radiation irradiation unit and the detection element array are rotated around a rotation axis parallel to a thickness direction of the radiation beam to collect radiation detection signals of a plurality of views. Signal collecting means for generating a tomographic image of a slice through which the radiation beam has passed based on the collected radiation detection signals A radiation detection signal of the radiation detection element according to an irradiation position error of the radiation beam in an arrangement direction of the detection element array in the detection element array. Linear correction means for linearly correcting the radiation detection signal of the plurality of views, while reducing the weight of the radiation detection signal having a large residual error after the linear correction, and reducing the weight of the radiation detection signal having a large residual error after the linear correction. A weighting means for increasing the weight of the radiation detection signal of the opposing view.