JPH08280659A - X-ray ct scanner - Google Patents

Abstract

PURPOSE: To prevent an artifact from being generated and to improve the quality of an image even if the focus of an X-ray tube is moved by letting the main shadow of an X-ray beam into an X-ray detector and obtaining a stable good X-ray detecting signal and an image. CONSTITUTION: An X-ray tube 10 and an X-ray detector (a two-dimensional detector) 11 and a pre-collimeter 15 inserted between the X-ray tube 10 and a subject P to be examined are provided. A means for controlling the width or the position of an aperture in the slice direction of the pre-collimeter 15 (a pre-collimeter driving device 17, a stage driving device 18, a stage controlling device 33 and a main controlling device 30) in such a way that only the main shadow of the X-ray beam is let into over the whole width in the slice direction of e.g. a specified detecting element row of the X-ray detector 11, and a means for reconstituting the X-ray CT image (an image reconstituting device 35) based on the detected data are provided. In addition, based on the amt. of movement of the focus of the X-ray, the width and/or the position of the aperture in the slice direction of the pre-collimater 15 are controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT scanner, and more particularly to an X-ray CT scanner which is exposed by an X-ray tube and passes through a subject.
The present invention relates to an X-ray CT scanner including a collimator that narrows the thickness of an X-ray beam incident on a line detector in the slice direction.

[0002]

2. Description of the Related Art Generally, an X-ray CT scanner for medical use has an X-ray
A collimator for reducing the thickness of the line beam in the slice direction is provided. This collimator includes a pre-collimator that performs its main function and a post-collimator that is used as an auxiliary.

In an X-ray CT scanner, an X-ray beam emitted from an X-ray tube is focused into a fan beam having a slice thickness required for scanning, the fan beam is transmitted to an object, and the transmitted beam is transmitted. Although received by the X-ray detector, the pre-collimator is used for the X-ray diaphragm in the slice direction.
That is, the pre-collimator 100 has a slit-shaped opening as shown in FIG. 14, and is interposed between the X-ray tube 101 and the subject 102, and the X-ray beam XB is desired by the opening adjustment by the control mechanism 103. Molded into a fan beam with a slice thickness of. Then, the fan beam transmitted through the subject 102 enters the X-ray detector 104, and the image is reconstructed based on the detected value. The post collimator also has a slit-shaped opening, but the mounting position is X
The thickness in the slice direction of the fan beam narrowed down by the pre-collimator in the vicinity of the X-ray detector between the line detector and the line detector is further narrowed down as necessary.

By the way, the focus of the X-ray tube is not infinitesimal,
Since it has a certain size in the slice direction, when the X-ray beam is pre-collimated by the pre-collimator, the intensity (profile PL) of the X-ray fan beam incident on the X-ray detector in the slice direction is shown in FIG. 15, for example. Area R _M (hereinafter referred to as “main shadow”) having a trapezoidal shape and a constant intensity, and areas R _S and 2R _S (hereinafter, referred to as “main shadow”) on both sides in the slice direction of the main shadow and having an intensity gradient. (Referred to as "penumbra") is formed.

[0005] Such umbra _{R M} and penumbra _R S, the X-ray profile consisting of _{R S,} in the conventional scanner, umbra _{R M} and penumbra _R S, all of the _{R S} X-ray It is received by the detector. For example, in single-slice CT, a single-slice detector in which one row of detector elements is arranged along the channel direction orthogonal to the slice direction is used.
Normally, as shown in FIG. 15, the X-ray tube 101 (tube focus F) and the pre-collimator 100 are set so that “beam width of X-ray in slice direction” <“detector width in slice direction” (1). , And the single-slice detector 104 are set in a positional relationship. In multi-slice CT,
A two-dimensional detector in which two or more rows of detecting elements are arranged along the channel direction orthogonal to the slice direction is used, and in this case as well, the above condition (1) is held as shown in FIG. The two-dimensional detector is a concept including an image intensifier.

By the way, in order to obtain an image with an X-ray CT scanner, it is necessary to collect two types of data. That is, the calibration data and the actual clinical object data. The calibration data is for correcting the variation in the sensitivity of each segment of the X-ray detector, and is measured at relatively long intervals (for example, 1 week, 10 days, etc.) using a known phantom, for example. This is line transmission data. The sensitivity correction is performed using the calibration data in the data processing process at the time of collecting the object data.

[0007]

However, the X-ray profile is, for example, due to expansion of the tube due to heat during exposure of the anode, movement of the focal point F due to backlash or deformation of the anode, and the like. As in the transition from the solid line state to the broken line state in FIG. 17, parallel movement in the slice direction causes a state in which the X-ray profile is different between when the calibration data is collected and when the subject data is collected. However, the sensitivity correction cannot be performed accurately,
There is a problem that artifacts and CT value shifts occur in such a reconstructed image.

This problem will be described with reference to the specific examples shown in FIGS. FIG. 18 shows the influence of changes in the slice direction of the X-ray profile on the single slice detector. Since the total output of the detector is the integral of the product of the X-ray profile in the slice direction and the sensitivity of the detector, the X-ray profile is obtained at the time of collecting the calibration data and the time of collecting the object data, for example, in the figure. When the state changes from the solid line to the dotted line, the detector output changes when the detector sensitivity in the slice direction is not uniform as shown in FIG.

FIG. 19 shows the effect of changes in the slice direction of the X-ray profile on the two-dimensional detector. In the case of a two-dimensional detector, when the calibration data is collected and the object data is collected, for example, when the solid line in the figure changes to a dotted line, the X-ray intensity at the part of the detector element corresponding to the penumbra Changes greatly.

As described above, the change between the time when the calibration data of the X-ray profile is acquired and the time when the object data is acquired causes an artifact or the CT value deviates from the actual value, which deteriorates the image quality and the diagnostic ability. It will lead to a situation in which

Further, when the condition (1) is satisfied as shown in FIG. 16, the penumbra is also used for imaging, and the slice plane detected in this penumbra is the main shadow. There was also the problem that the image quality deteriorated.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is a first object of the present invention to prevent deterioration of image quality due to the use of penumbra.

A second object is to obtain an image of high quality and high accuracy by eliminating the artifacts and the deviation of the CT value due to the movement of the X-ray profile in the slice direction accompanying the movement of the X-ray focus. To do.

[0014]

In order to achieve the above object, an X-ray CT scanner according to a first aspect of the present invention includes an X-ray tube for irradiating a subject with an X-ray beam, and the subject. A pre-collimator which is interposed between a specimen and the X-ray tube and narrows the width of the X-ray beam in the slice direction orthogonal to the cross section of the specimen sliced by the X-ray beam; And an X-ray detector for receiving the transmitted X-ray beam. Then, the X-ray detector is formed by a two-dimensional detector in which a plurality of detection element rows each including a plurality of detection channels are arranged in the slice direction,
Further, the specified pre-collimator is arranged so that a designated detection element array of the plurality of detection element arrays receives only the main projection of the profile and penumbra of the profile of the X-ray beam formed by the pre-collimator. Control means for controlling and reconstructing means for reconstructing an X-ray CT image based on the data detected by the designated detector array are provided.

In the X-ray CT scanner according to the second aspect of the present invention, in particular, the X-ray detector is formed by a two-dimensional detector in which a plurality of detection element rows each having a plurality of detection channels are arranged in the slice direction. And the data detected by at least one detection element array of the plurality of detection element arrays that receives only the umbra of the X-ray beam profile formed by the pre-collimator and the penumbra Reconstructing means for reconstructing an X-ray CT image based on the above.

In the X-ray CT scanner according to the third aspect of the present invention, in particular, the X-ray detector is formed by a two-dimensional detector in which a plurality of detection element rows each having a plurality of detection channels are arranged in the slice direction. In addition, the data detected by at least one element array of the plurality of detection element arrays, which receives only the main projection of the profile of the X-ray beam formed by the pre-collimator and the main projection of the penumbra, Detected by at least one element array of the plurality of detection element arrays that receives a primary acquisition mode in which image reconstruction is performed and a main shadow and penumbra of an X-ray beam profile formed by the pre-collimator Selecting means for selecting one of the second acquisition modes for performing image reconstruction using the acquired data, and the acquisition means selected by the selecting means. And scanning means for collecting the data by performing a scan by the X-ray beam on the basis of the mode comprises. In addition to this, as a fourth aspect, it is desirable to include control means for controlling the aperture state of the pre-collimator according to the collection mode selected by the selection means.

In the X-ray CT scanner of each of the above aspects,
For example, a top plate that is movable in the slice direction and on which the subject is placed, and a top plate that matches the total slice width of the designated detection element array for each scan by the X-ray beam during multi-scan It is possible to provide a judging means for judging the moving distance and a top controlling means for controlling the movement of the top based on the moving distance judged by the judging means.

In the X-ray CT scanner of each of the above aspects, for example, a top plate that is movable in the slice direction and on which the subject is placed, and the X-ray tube and the X-rays around the subject during helical scanning. Based on the moving distance judged by this judging means, the judging means judges the moving distance of the top plate according to the total width in the slice direction of the designated detecting element array for each rotation of the detector. And a top control means for controlling the movement of the top.

Further, in the X-ray CT scanner according to each of the above aspects, for example, the opening width in the slice direction of the pre-collimator is set to the slice direction of the X-ray beam accompanying the movement of the X-ray focal point of the X-ray tube. It is possible to provide a setting means for setting a wide amount by an amount corresponding to the predicted maximum movement amount.

Further, in the X-ray CT scanner according to the first aspect, for example, a detection means for detecting an amount corresponding to the movement of the X-ray focal point of the X-ray tube is provided, and the control means is
At least one of an opening width of the pre-collimator in the slice direction, a position of the pre-collimator in the slice direction, and a position of an X-ray focal point of the X-ray tube in the slice direction based on a detection amount of the detection unit. At least one of the designated detection element arrays may be controlled to receive the main shadow of the X-ray beam. The configuration relating to the detecting means for detecting the amount corresponding to the movement of the X-ray focal point of the X-ray tube can be similarly applied to the X-ray CT scanners according to the second to fourth aspects.

Further, the X-ray C according to the fifth aspect of the present invention
In the T scanner, in particular, the X-ray detector is formed by a single-slice detector in which a detection element row composed of a plurality of detection channels is arranged in one row in the slice direction, and the detection element row is formed by the pre-collimator. X
A control means is provided for controlling at least one of an opening width and a position of the pre-collimator in the slice direction so as to receive only a main shadow of a line beam profile.

Furthermore, X of the sixth aspect according to the present invention
The X-ray CT scanner includes an X-ray tube that irradiates an X-ray beam toward the object, the object that is interposed between the object and the X-ray tube, and is sliced by the X-ray beam. Of a pre-collimator that narrows the width of the X-ray beam in the slice direction orthogonal to the cross section of the X-ray detector, an X-ray detector that receives the X-ray beam that has passed through the subject, and the subject and the X-ray detector. And a post collimator for narrowing the width of the X-ray beam incident on the X-ray detector in the slice direction, the X-ray detector being provided with a detection element array composed of a plurality of detection channels. Formed with a single slice detector arranged in one row in the slice direction,
A part or penumbra of the main shadow of the X-ray beam formed by the pre-collimator is cut so that only the main shadow is incident on the X-ray detector. Control means is provided for controlling the opening width of the collimator in the slice direction.

With the above-described structure, the essence of the X-ray beam extends over the width in the slice direction of the array of detection elements of the X-ray detector (in the case of a two-dimensional detector, the array of detection elements designated at the time of imaging or predetermined). For example, the aperture width and / or the position of the pre-collimator in the slice direction is controlled so that only the incident light enters. Therefore, even if the focal point moves in the X-ray tube, the X-ray intensity of the profile in the slice direction becomes constant, and the image quality does not deteriorate.

Further, the opening width in the slice direction of the pre-collimator is set wider by an amount corresponding to the predicted maximum movement amount of the X-ray beam in the slice direction accompanying the movement of the X-ray focal point of the X-ray tube. Therefore, a good signal and image quality can be obtained only by setting the aperture once.

Further, an amount corresponding to the movement of the X-ray focal point of the X-ray tube is detected, and the essence of the X-ray beam is designated or predetermined in the two-dimensional X-ray detector based on the detected amount. For example, the opening width in the slice direction and / or the position in the slice direction of the pre-collimator is controlled so that the pre-collimator is incident over the width of the detector element array in the slice direction. For this reason, even when the amount of movement of the X-ray focus is different between when the calibration data is collected and when the image is captured, the main shadow portion is always incident on the X-ray detector, and stable and good calibration is applied during image reconstruction, The occurrence of artifacts and CT value shifts can be prevented.

[0026]

DETAILED DESCRIPTION OF THE INVENTION An X-ray CT scanner according to an embodiment of the present invention will be described below with reference to FIGS.

The X-ray CT scanner shown in FIG. 1 comprises a gantry 1, a bed 2 and a control cabinet 3, and is an apparatus driven by, for example, the RR system. A top plate 2a is disposed on the upper surface of the bed 2 so as to be slidable in the longitudinal direction (corresponding to the slice direction (rotation axis direction)), and the subject is placed on the top surface of the top plate 2a. P is put. The top board 2a is inserted into the diagnostic opening of the gantry 1 so as to be able to move forward and backward by the drive of the bed driving device 2b represented by a servo motor. Further, the bed 2 is provided with a position detector (not shown) such as an encoder for detecting the position of the table 2a in the longitudinal direction of the bed with an electric signal. As shown in FIG. 1, the channel direction is defined as the slice direction and the direction orthogonal to the X-ray beam irradiation direction.

The gantry 1 has an X-ray tube 10 and an X-ray detector 11 which are opposed to each other with the subject P inserted in the opening therebetween.
It has. The X-ray detector 11 is a two-dimensional detector in which a plurality of detection element rows having a plurality of detection channels are arranged in the slice direction, or a single slice in which one detection element row having a plurality of detection channels is arranged in the slice direction. It is a detector. The X-ray tube 10 and the X-ray detector 11 can be rotated by a gantry drive device 12 around an axis of rotation in the gantry 1. The current signal corresponding to the transmitted X-ray detected by the X-ray detector 11 is a data acquisition device (DAS).
It is converted into a digital amount at 13 and sent to the control cabinet 3.

Further, in the gantry 1, a pre-collimator 15 is provided between the X-ray tube 10 and the subject P, and a post-collimator 16 is provided between the subject P and the X-ray detector 11. . The pre-collimator 15 has, for example, two blades that form a slit-shaped opening having a constant width in the channel direction and a variable width in the slice direction. The two blades move symmetrically in the slice direction, and the entire precommeter 15 is also movable in the slice direction. The opening width and position of the pre-collimator 15 in the slice direction are adjusted by the pre-collimator driving device 17 set in the gantry 1. As a result, the width of the X-ray beam emitted from the X-ray tube 10 in the slice direction is narrowed to form a fan beam having a desired width. X
Since the X-ray focal point F of the X-ray tube 10 has a finite length in the slice direction, the X-ray profile in the slice direction at the detector position forms a main shadow and a penumbra as in the above.

Since the opening of the pre-collimator 15 is formed in a slit shape, the problem caused by the penumbra mentioned above does not occur in the channel direction.

Similarly, the post collimator 16 also has a slit-shaped opening having a constant width in the channel direction and a variable width in the slice direction. The width in the slice direction is adjusted by the post collimator driving device 18. In the present embodiment, the post-collimator 18 has the auxiliary diaphragm function of further narrowing the X-ray beam narrowed by the pre-collimator 15.

Both the pre-collimator driving device 17 and the post-collimator driving device 18 are provided with a stepping motor and a slide mechanism, and operate in response to a drive control signal sent from the gantry driving device 12. At least the pre-collimator driving device 17 includes a motor that adjusts the opening width itself and a motor that adjusts the position of the entire opening width in the slice direction.

A focus position detector 20 as a focus position sensor is attached near the X-ray detector 11. A part of the X-ray beam exposed by the X-ray tube 10 is
For example, after passing through a pre-collimator 15D for focus position detection, which is attached to the side of the pre-collimator 15 in the channel direction, the light enters the focus position detector 20. As shown in FIG. 2, the focus position detector 20 includes, for example, two X-ray detectors FD1 and FD2 (each of which are adjacent in the slice direction).
It comprises a scintillator and a photodiode), and is sent to the gantry control device of the control cabinet 3 which will be described later after A / D conversion similarly to the data collecting device.

The control cabinet 3 has a main control unit 30 that controls the entire system, and a high voltage control unit 31, a bed control unit 32, and a gantry control unit 33 that operate in response to commands from the main control unit 30. In particular, the gantry control device 33 determines the detection signals P1 and P2 of the focus position detector 20, that is, the ratio “(P1-P2) / (P1 + P2)” of the X-ray intensities incident on the two built-in X-ray detectors FD1 and FD2. Along with the calculation, the ratio and the X-ray focus position movement amount in the slice direction are referred to in advance in a storage table to obtain the focus position movement amount. FIG. 3 is a graph showing an example of such correlation. In a certain range of focus movement, this relationship is almost linear.

Incidentally, in this gantry control device 33, instead of referring to the above-mentioned storage table, it is also possible to previously store only the equation of the straight line representing the characteristic of FIG. 3 and calculate the focal position movement amount. .

Further, the control cabinet 3 is provided with a high voltage generator 34 which operates in response to a drive signal from the high voltage controller 31 as shown in FIG. 1, and the high voltage generated by the high voltage generator 34 is It is supplied to the X-ray tube 20. Further, the control cabinet 3 receives the collection signal from the data collection device 12 and reconstructs the image data.
5. Image data storage device 3 for storing image data
6, a display device 37 for displaying a reconstructed image, and an input device 38 for an operator to give a command to the main controller 30.

As shown in FIG. 4, when the X-ray detector 11 is a two-dimensional detector, the data acquisition device 13 detects "n channels × f rows" of detection signals (n and f are larger than "1"). A positive integer), the data selection unit 13A ₁ for selecting the detection signal for one column for each channel according to the column selection signal,
13A ₂ , ..., 13A _n , and this data selection unit 13
A _1, ..., and a data collecting unit 13B to the A / D conversion or amplify each selected detection signal by 13A _n. The column selection signal is sent from main controller 30. The X-ray detection data for each channel generated by the data acquisition unit 13B is output to the image reconstruction device 35.

Main controller 30 manages the entire scanner in accordance with a predetermined procedure. An example is shown in FIGS.
Shown in The control by the main controller 30 is divided into a case where a two-dimensional detector is used as the X-ray detector 11 and a case where a single slice detector is used.

FIG. 5 shows a control example of the main controller 30 when a two-dimensional detector is used as the X-ray detector 11.

First, in step 40 in the figure, the main controller 30 determines the scan mode (multi-scan or helical scan), the number and position of the detection element arrays designated for data acquisition, the scan site and position, and the slice. Scan conditions such as thickness, X-ray tube voltage and current (however, "1" described later
The number of slices per rotation and the acquisition mode are not included). Next, at step 41, the number of slices per rotation is input. Further, in step 42, a collection mode (in the present embodiment, “main shadow mode” (: mode for collecting only main shadow), “main shadow + penumbra mode” (: (part of) main shadow and penumbra) ) And collect mode).
The detector array used for data acquisition of the X-ray detector 11 is arbitrarily designated, for example, by the operator during imaging.

Next, in step 43, the width W _pre of the opening of the precommeter 15 in the slice direction is calculated.
At the time of this calculation, a possible position mode of the precommeter 15 is determined as shown in FIG.

That is, "whether all the rows or a part of the designated rows are to be used among the plurality of rows of the detection elements of the two-dimensional detector" is input information from the input device 38 (step in FIG. 5). 40) (step 43 in FIG. 6).
₁ ). If it is determined that "all columns" are to be used, the acquisition mode is either "honkage mode" or "honkage + penumbra" based on the input information (step 42 in FIG. 5) instructed from the input device 38. Mode "(step 43 _{2 in} FIG. 6).
When the "main shadow mode" is determined by this, the pre-collimator 15, the X-ray profile PL, and the X-ray detector 11 have the aperture width in the slice direction of the pre-collimator 15 so that the main shadow covers all the element rows. Will be controlled,
The positional relationship of the explanatory view (a) in FIG. 6 is taken. Also, "Honkage +
When the “half penumbra mode” is determined, the penumbra is incident on a part of the entire element row, and the positional relationship shown in FIG.

[0043] In addition, subjected to the same determination even with the step 43 ₂ proceeds to step 43 ₃ If it is determined that the use of "some of the designated row of detecting elements" in step 43 _1. As a result, when the “main shadow mode” is set, the opening width in the slice direction of the pre-collimator 15 is set so that the main shadow covers only a part of the designated detection element rows as shown in the explanatory diagram (c). Will be controlled. In the "main shadow + penumbra" mode, the positional relationship in the explanatory diagram (d) in which the penumbra is incident on a further part of the designated part of the element array can be recognized.

When the possible positional relationship of the pre-collimator 15 is determined in any of the above-described explanatory views (a) to (d), the main controller 30 causes the pre-collimator 1 to operate.
The width W _pre of the opening of No. 5 in the slice direction is calculated. This calculation is performed, for example, by referring to a storage table preset based on the position data of the X-ray tube 10, the pre-collimator 15, the subject's isocenter, the X-ray detector, etc. for each aspect of the above positional relationship. It is preferably implemented. Further, it may be calculated instead of using the storage table.

Next, in step 44 of FIG. 5, the scanning method already obtained is judged, and in the case of multi-scan, in step 45 the feed pitch of the top plate is calculated. As shown in FIGS. 12 (a) and 12 (b), this feed pitch is a distance for moving the top plate, and is a distance that matches the total slice width of the detector array designated for use of the X-ray detector 11. Is. On the other hand, in the case of helical scan, step 4
In step 6, the top plate feed speed is calculated. This feeding speed is a speed determined as the moving distance of the top plate per one rotation, and the moving distance is made to coincide with the total slice width of the designated detection element array of the X-ray detector 11. In the case of helical scan, the feed rate may be specified by another method. For example,
In order to increase the sampling density in the slice direction, it is possible to select a fractional value having a decimal point (fractional number) as the feed rate, instead of selecting an integer value without a decimal point corresponding to the designated detection element array.

In the multi-scan, "scan / top movement / scan / top movement ..." Is repeated.
When the amount of movement of the tabletop is made equal to the total slice width in one scan (that is, the half-value width of the X-ray profile incident on all of the designated detection element rows), the obtained images are all at equal intervals, Further, the individual images are obtained from the regions adjacent to each other, and there is no gap between the images. This applies to both single-slice CT and multi-slice CT, and is advantageous when a three-dimensional model is created from the obtained images.

Helical scanning is a scanning method in which data is acquired in a spiral shape by simultaneously performing scanning and moving the tabletop. In the case of reconstructing an image, a method of interpolating collected data with respect to a cross section to be reconstructed using a distance from the cross section as a coefficient is general. In the helical scan, when the moving speed of the tabletop is matched with the total slice width, the data collection areas are adjacent to each other every one rotation, and it is possible to collect subject data without omission.

When various data are obtained as described above, the main controller 30 proceeds to steps 47 to 50 to collect data 12, the image reconstructor 35, the gantry controller 33, the bed controller 32, and the high voltage. The necessary data is output to the control device 31 (steps 47 to 50). Thereby, each control device operates based on a predetermined procedure stored in advance, and the instructed scan is executed.

On the other hand, the main controller 30 in the case where a single slice detector is used as the X-ray detector 11 in FIG.
The control example of is shown. This control example captures information (slice width) peculiar to a single slice, and
The post-collimator 16 which is out of the control when the dimensional detector is used is newly added depending on the mode, which is greatly different from the case of the two-dimensional detector.

Specifically, in step 60 of the figure, the main controller 30 determines the scan mode (single scan, multi-scan, or helical scan), scan region and position, X-ray tube voltage and current, and the like. Input the scanning conditions (however, "slice width" and "acquisition mode" described later are not included). Next, in step 61, the slice width of the single slice is input, and in step 62, the acquisition mode (whether it is the “main shadow mode” or the “main shadow + half shadow mode”) is input.

Further, in step 63, the opening width W _pre of the _pre -collimator 15 in the slice direction is calculated.
Also in this case, the possible position of the pre-collimator 15 is determined as shown in FIG.

That is, it is judged whether the already input collection mode (step 62) is the "main shadow mode" or the "main shadow + half shadow mode" (step 63 _{1 in} FIG. 8). As a result, when it is determined that the "real shadow mode" is selected, step 6
3 ₂ proceeds to previously obtained are designated slice width (Step 61) is equal to or equal to the width corresponding to the detector width in the rotation axis direction. If the result of this judgment is NO, it means that “specified slice width <width corresponding to detector width” is satisfied.
The position mode is represented as shown in FIG. And
Only in this case, the post collimator 16 is involved as will be described later. On the other hand, when the result is YES, that is, “specified slice width = width corresponding to detector width”, the pre-collimator 15 takes the position mode of FIG. Step 63
_{When the} “main shadow + penumbra mode” is determined in ₁ (in this case, the specified slice width = the width corresponding to the detector width cannot be obtained), the position mode of the explanatory diagram (c) is taken. . The post collimator 16 is not involved in the case of the positions shown in FIGS. The slice width here is "X
It is defined as a value obtained by projecting the half-value width of the line profile on the center of the rotation axis.

The calculation of the opening width W _pre of the _pre -collimator 15 is performed by the X-ray tube 1 for each mode determined as described above, for example.
0, the pre-collimator 15, the isocenter of the subject, and the X-ray detector 11 based on each position data and the like, by referring to a predetermined storage table. Of course, the opening width _Wpre may be calculated each time.

Further, in step 64 of FIG. 7, the opening width W _post of the post collimator 16 in the slice direction is calculated.
This calculation is performed in the position mode of FIG. 8A (that is,
This is performed only when the specified slice width <the width corresponding to the detector width), and the aperture width W _post is calculated so that the post collimator 16 cuts the penumbra.

Next, main controller 30 proceeds to step 65 to determine the scanning method. If it is determined to be a single scan, skip to step 68,
When it is determined that the scan is the multi-scan and the helical scan, the feed pitch of the top or the feed speed of the top is calculated in step 66 or step 67 in consideration of the slice width.

After this, the processes of steps 68 to 71 are sequentially carried out in the same manner as the processes of steps 47 to 50 in FIG.

Further, an example of controlling the opening width of the collimators 15 and 16 in the slice direction by the gantry controller 33 will be described with reference to FIG.

That is, the gantry control device 33 inputs the opening width W _pre supplied from the main control device as an initial value (step 80 in the figure) and sends a control signal corresponding to the data to the gantry drive device 18. Then, the pre-collimator driving device 17 is operated to adjust the actual opening width and / or position of the pre-collimator 15 in the slice direction to the command initial value (step 81 in the figure).

Thereafter, a detection signal from the focus position detector 20 is input (step 82 in the figure), and the movement amount of the focus F due to heat generation of the X-ray tube 10 is shown in the graph shown in FIG. 3, for example. The estimated calculation is performed by referring to the stored table (step 83 in the figure).

Next, in step 84, the aperture width W _pre of the pre-collimator 15 or the position in the slice direction in which the estimated movement amount of the X-ray focal point F is added is recalculated. That is, aperture data that corrects the displacement of the X-ray profile PL in the slice direction due to the movement of the focus F can be obtained. The new data for this correction is used again for the gantry driving device 12
And the opening width and position of the pre-collimator 15 are corrected with the updated values (step 81 in the figure). Less than,
Similar processing is repeated.

In the focus follow-up control for the focus movement according to the processing of FIG. 9 described above, only the pre-collimator 15 needs to follow, and the post collimator 16 is X.
Since it is close to the line detector 11, it is not necessary to move the collimator 16 following it. When a single slice detector is adopted as the X-ray detector 11, the slice width <
In the position mode of the pre-collimator 15 which is the detector width (that is, the position mode shown in FIG. 8A), the post collimator 16 controls the aperture width W _post calculated in the process of step 64 of FIG. It is instructed by a process (not shown) of the device 33. However, also in this case, the opening width W _post of the post collimator 16 is not controlled to follow the movement of the X-ray focal point, and is always held at a constant value to cut the penumbra. When the pre-collimator 15 adopts other position modes, that is, FIGS. 6A to 6D, 8B, and 8C, the post-collimator 16 does not participate in the X-ray collimation.

FIG. 1 shows an example of the operation relating to the above configuration and processing.
0 and 11 are shown. 10 illustrates a case where only the opening width of the pre-collimator 15 is controlled, and FIG. 11 illustrates a case where the opening width and position of the pre-collimator 15 in the slice direction are controlled.

Now, a two-dimensional detector is used as the X-ray detector 11 (element rows in the slice direction are a to h), and a part of the detector element rows c to f in the slice direction are designated to perform the book. Multi-scan in shadow mode shall be performed. When the scan condition, the number of slices, and the acquisition mode including these pieces of information are input to the main controller 30 (steps 40 to 4 in FIG. 5).
1), the position mode of the pre-collimator 15 and the opening width in the slice direction are automatically determined (step 43 in the figure).
Further, since a multi-scan is designated as the scanning method, the feed pitch is automatically calculated so as to be equal to the total slice width corresponding to a part of the designated element rows (step 45 in the figure). The data input in this way and the data calculated are respectively the required data collection device 13, image reconstruction device 35, and gantry control device 3.
3, the bed control device 50, and the high voltage control device 51.

In particular, the data collecting device 13 is "which column" (in this case, columns c to f) instructed by the main controller 30.
A column for each channel is switched by a column selection signal indicating whether or not to use, and necessary data is selected and sent to the image reconstructing device 35. Also, since multi-scan is commanded, c
The slice width corresponding to ~ f rows is the top plate feed pitch. If helical scan is commanded, c ~
The slice width corresponding to f rows is the top plate moving distance during one rotation. As a result, the loci drawn by the detector are all at equal intervals, and the processing such as data correction in reconstruction is simplified.

As a result, under the control of the main control device 30, each device operates in synchronization with each other to collect data and reconstruct the image. At this time, the pre-collimator 15 takes the position mode shown in FIG. 10 (corresponding to FIG. 6C). That is, the control so that only Honkage R _M are part of a specified element column c~f of the sensing element array a~h opening width W _pre 2D detector 11 slice direction of the pre-collimator 15 is incident To be done.

Moreover, the tube focus F of the X-ray tube 10 may move in the slice direction due to heat generation during exposure of the anode as shown in FIG. 10, for example. Even in this case,
The aperture width of the pre-collimator 15 is finely adjusted in real time according to the processing of FIG. 9 associated with the detection of the focus position movement amount, and only the main shadow R _M is incident on some of the designated element rows c to f for detection. .

By feedback-controlling the aperture width of the pre-collimator 15 in this way, even when the X-ray profile is changed between when the calibration data is collected and when the actual image is taken, the two-dimensional detector 11 Since the intensity of X-rays incident on the pre-specified detection element arrays c to f (corresponding to the slice width in the slice direction) is always constant,
The calibration at the time of reconstruction is favorably performed, and it is possible to prevent the artifacts on the image and the shift of the CT value, which have conventionally occurred. In addition, the requirement for changes in the X-ray profile is greatly reduced. Furthermore, since the reconstructed image uses only the main shadow, the image quality of any slice plane becomes good. Furthermore, since only the opening width of the pre-collimator 15 needs to be controlled, there is an advantage that the number of motors to be driven is only one for controlling the opening width, and the control is simple.

In the case where the control method of FIG. 10 described above is used for scanning in the main shadow mode by using the entire surface of the two-dimensional detector, that is, all the detection element rows a to h in the example of FIG. 10, (ie, FIG. 6). The same can be suitably applied to the state (a). Further, when a single slice detector is used as the X-ray detector 11, in the case of the main shadow mode (that is, in FIG.
(A) and (b) states) can also be suitably implemented.

On the other hand, in the case of the scan shown in FIG. 11, the same conditions as those in the case of FIG. 10 (two-dimensional detector, use of only some of the designated detection element arrays c to f in the slice direction, and main shadow mode) However, the feedback control amount associated with the focus movement is set to the “position in the slice direction” of each blade of the precollimator 15 (that is, the opening width and position in the slice direction of the precollimator). That is, the position of the entire pre-collimator 15 in the slice direction is changed in real time. This control is performed by steps 82 to 8 in FIG.
It is performed in real time by a series of processes of 4,81.

Therefore, for example, when the focal point F of the X-ray tube 10 moves to the right as shown by the arrow in FIG. 11, as a result, one blade of the pre-collimator 15 in the slice direction becomes the right (arrow A ₁ ). And the other blade is also moved to the right (arrow A ₂ ) an equal distance. That is, unlike the control both blade changing only the opening width W _pre move symmetrically in the slice direction responsible for collimation in the slice direction, the entire collimator aperture width W _pre itself and slice direction as in FIG. 10 described above The position of changes according to the amount of focus movement.

Therefore, the position of the X-ray profile PL in the slice direction with respect to the X-ray detector 11 does not change, and even if the focal point shift actually occurs, it is the same as the apparent focal point shift. As a result, the same effect as that of the case of FIG. 10 can be obtained, and more stable and highly accurate position control of the profile can be performed as compared with the method of FIG. 10, and the exposure dose can be minimized. There is an advantage that you can. More importantly, when the precollimator 15 shown in FIG. 11 is controlled, the position of the umbra in the slice direction is fixed. That is, the shape of the X-ray profile of the detector array that receives the main shadow is unchanged between the calibration data collection and the image data collection. Therefore, there is also an advantage that an image using the data detected by the detector array that receives such a main shadow can always be kept in high quality.

When the control method of FIG. 11 described above is used for scanning in the main shadow mode using the entire surface of the two-dimensional detector, that is, all the detection element rows a to h in the example of FIG. 11, (ie, FIG. 6). The same can be suitably applied to the state (a). Further, when a single slice detector is used as the X-ray detector 11, in the case of the main shadow mode (that is, in FIG.
(A) and (b) states) can also be suitably implemented.

On the other hand, the "main shadow + semi-shadow mode" is selected by the inspector as needed (step 42 in FIG. 5 and FIG. 7).
See step 62). In this way, not only the “main shadow mode” but also the “main shadow + penumbra mode” can be arbitrarily selected, so that the dose can be suppressed by making the penumbra part incident on the detector as well. Moreover, there is an advantage that multi-scan and helical scan can be performed at high speed. This is shown in FIGS. 12 (a) and 12 (b). The figure (a) explains the scan in the “main shadow mode”, and the figure (b) explains the scan in the “main shadow + penumbra mode”. The figure (b) shows the X-ray detector. The number of usable element rows on 11 is large. This enables high-speed scanning in the "main shadow + penumbra mode".

By the way, in FIGS. 12 (a) and 12 (b), arrows representing the amount of the feed pitch or the feed speed are schematically drawn. Since the feed pitch and feed speed are actually calculated by regarding the X-ray focal point as a point, the arrows indicating these amounts are actually slightly shorter than those shown in the figure, and correspond to the total slice width. It becomes the amount to do.

A modified example of the present invention will be described with reference to FIG. In the above-mentioned embodiment, the position of the pre-collimator 15 in the slice direction and / or the opening width is finely adjusted in real time according to the movement of the tube focus of the X-ray tube. It is a simplification.
Specifically, the opening width and / or position of the pre-collimator 15 in the slice direction is initialized only once, and thereafter, even if the focal position moves, the value is held.

Now, as in the case of FIGS. 10 and 11 described above, it is assumed that scanning is performed in the full shadow mode by using only a part of the designated detection element arrays c to e of the two-dimensional detector. Even if the X-ray tube 10 shifts from the lowest temperature state to the highest temperature state and the focal point moves, at least some of the target detection element arrays c to e are opened so that only the main shadow is incident. The width W _pre (or position) is initially set only once. That is, in consideration of the focus movement in advance, the detection element array to be used is determined, and the opening width (or the position in the slice direction) is set wider. Then, once set before scanning, the aperture control thereafter is not performed.

As a result, the temperature of the X-ray tube rises in accordance with the driving state of the X-ray CT scanner, and the tube focus becomes, for example, as shown in FIG.
Even when moving from the state shown by the solid line in 3 to the state shown by the dotted line (the state where the X-ray tube is warmed to the maximum), the designated detection element rows c to e of the X-ray detector 11 always have only the main shadow. Is incident. Therefore, according to this modification, the opening control is performed only once, and the control is simplified. In this case, there is also an advantage that the focus position detector 20 is unnecessary.

When the control method of FIG. 13 described above is used for scanning in the main shadow mode using the entire surface of the two-dimensional detector, that is, all the detection element arrays a to h in the example of FIG. 13, (ie, FIG. 6). The same can be suitably applied to the state (a). Further, when a single slice detector is used as the X-ray detector 11, in the case of the main shadow mode (that is, in FIG.
(A) and (b) states) can also be suitably implemented.

Further, in the above-described modified example, it is not always necessary to take the means of initializing the opening width (or position) of the pre-collimator 15 only once at the time of scanning, and it is necessary to set it to a fixed value in advance. May be.

The sensor means relating to the movement of the tube focus of the X-ray tube according to the present invention is not limited to the one having the above-mentioned construction, and may be an infrared detector mounted on the outer peripheral surface of the X-ray tube 10, for example. The temperature change of the X-ray tube 10 may be detected, and the movement of the tube focus may be estimated based on the temperature change. Further, for example, as described in Japanese Utility Model Application Laid-Open No. 2-91200, a temperature detector for detecting the temperature of the cooling oil of the X-ray tube may be used, or the X-ray tube voltage, the X-ray tube current, the X-ray tube current, and the X-ray tube current.
A structure may be adopted in which the information regarding the driving of the X-ray tube, such as the irradiation time of X-rays and the stopping time of X-ray irradiation, is taken in as the information regarding the movement of the tube focus.

Further, in the above-described embodiment and modification, the aperture of the post-collimator 16 is controlled only when the scan is in the main shadow mode using the single slice detector and the slice width is smaller than the detector width. I chose
By controlling the post-collimator 16 in synchronization with the pre-collimator 15, the post-collimator 16 positively cuts a penumbra portion (in the main shadow mode) as an unnecessary beam incident on the detector housing portion or the like. Good. As a result, the penumbra is the detector housing and C
Unnecessary radiation exposure for the patient caused by scattering at the T gantry portion or the like can be more reliably prevented. Moreover, the synchronous control of the post-collimator 16 has an advantage that a scattering prevention structure such as attaching an X-ray absorbing material to the housing of the detector is unnecessary.

Furthermore, the present invention is based on the above-described embodiment, that is, one of the two-dimensional detector that receives only the umbra of the X-ray beam.
The above-described designation of the detection element array is not limited to the scanner configuration in which the detection element array is designated each time the actual X-ray scanning is performed. Even when the one or more detection element arrays are fixedly determined in advance due to design conditions or other conditions, such a two-dimensional detector is provided with the X-ray C of the present invention.
It can be suitably applied to a T scanner. That is, in such a case, the column selection signal to the data collection device 13 should be set so that only the data detected by the predetermined detection element array is adopted and the same processing as described above is performed. Good.

Further, although the above-described embodiments and modifications have been described focusing on adjusting the physical quantity relating to the pre-collimator control, further modifications are possible. As an example, the electron beam applied to the target of the X-ray tube may be controlled by an electromagnetic force to adjust the position of the X-ray focal point to be invariable when viewed from the outside of the tube, or the X-ray tube itself may be adjusted. The position may be controlled for the same purpose.

Furthermore, the present invention is not limited to the above-described embodiments and modifications, and can be appropriately combined, changed and modified within the scope of the basic principle of the present invention.

[0085]

As described above, the X-ray C of the present invention is used.
According to the T scanner, the width in the slice direction of the detection element array of the X-ray detector (in the case of a two-dimensional detector, a designated detection element array out of a plurality of detection element arrays or a predetermined detection element array). Only the true shadow of the X-ray profile is incident on the whole, so the image quality does not change depending on the slice position.
In addition, a high signal value can be detected, and a high quality reconstructed image can be provided.

Further, since the opening width of the pre-collimator in the slice direction is set wide by an amount corresponding to the predicted maximum movement amount of the X-ray beam in the slice direction accompanying the movement of the X-ray focal point of the X-ray tube, Good signal and image quality can be obtained only by setting the aperture once.

Further, even if the tube focus of the X-ray tube moves due to temperature rise and the like, and the X-ray profile changes between the time when the calibration data is collected and the time when the image is taken, for example, the aperture in the slice direction of the pre-collimator is opened. By finely adjusting the width and / or the position etc. in real time according to the amount of focus movement, the main shadow is made incident on the entire width in the slice direction of the designated or predetermined detection element array of the X-ray detector. Since it is possible to eliminate the artifacts on the image and the shift of the CT value, the image quality can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an X-ray CT scanner according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between an X-ray detector and incidence of an X-ray beam.

FIG. 3 is a graph showing the relationship between the output of the X-ray detector and the X-ray focal point position movement amount.

FIG. 4 is a block diagram of a data collection device.

FIG. 5 is a flowchart showing a control example in the case of a two-dimensional detector executed by a main controller.

FIG. 6 is a flowchart for determining the position mode of the pre-collimator in the case of a two-dimensional detector.

FIG. 7 is a flowchart showing an example of control in the case of a single slice detector executed by a main controller.

FIG. 8 is a flowchart for determining the position mode of the pre-collimator in the case of a single slice detector.

FIG. 9 is a flowchart showing an example of opening control executed by the gantry control device.

FIG. 10 is an explanatory diagram showing an example of focus movement tracking control when a two-dimensional detector is used.

FIG. 11 is an explanatory diagram showing another example of focus movement tracking control when a two-dimensional detector is used.

12A and 12B are diagrams for comparing and explaining the magnitude of the feed pitch or the feed speed in the main shadow mode and the main shadow + penumbra mode.

FIG. 13 is a diagram illustrating aperture setting of a pre-collimator according to a modification.

FIG. 14 is a diagram illustrating the role of a pre-collimator.

FIG. 15 is a diagram illustrating a positional relationship between an X-ray profile and an X-ray detector in conventional single-slice CT.

FIG. 16 is a diagram illustrating a positional relationship between an X-ray profile and an X-ray detector in CT related to a conventional two-dimensional detector.

FIG. 17 is a diagram for explaining movement of a tube focus of an X-ray tube.

FIG. 18 is a diagram for explaining the influence of a profile change on a single slice detector.

FIG. 19 is a diagram for explaining the influence of profile change on a two-dimensional detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 gantry 2 bed 2a top board 2b bed drive device 3 control cabinet 10 X-ray tube 11 X-ray detector 12 frame drive device 13 data acquisition device 15 precollimator 16 postcollimator 17 postcollimator drive device 20 postcollimator drive device 20 X-ray Detector 30 Main controller 32 Bed controller 33 Frame controller 35 Image reconstructor

Claims (15)

[Claims] 1. An X which irradiates an object with an X-ray beam.
A pre-collimator for narrowing the width of the X-ray beam in a slice direction orthogonal to the cross section of the subject sliced by the X-ray beam and interposed between the X-ray tube and the subject. And an X-ray CT scanner including an X-ray detector that receives the X-ray beam that has passed through the subject, wherein the X-ray detector includes a detection element array including a plurality of detection channels in the slice direction. A book which is formed by a plurality of two-dimensional detectors and in which a designated detector array among the plurality of detector arrays is formed by the pre-collimator in the main shadow and penumbra of the X-ray beam profile. Control means for controlling the pre-collimator so as to receive only shadows, and reconstructing means for reconstructing an X-ray CT image based on the data detected by the designated detector array. An X-ray CT scanner characterized by that. 2. X for irradiating a subject with an X-ray beam
A pre-collimator for narrowing the width of the X-ray beam in a slice direction orthogonal to the cross section of the subject sliced by the X-ray beam and interposed between the X-ray tube and the subject. And an X-ray CT scanner including an X-ray detector that receives the X-ray beam that has passed through the subject, wherein the X-ray detector includes a detection element array including a plurality of detection channels in the slice direction. At least one of the plurality of detection element arrays which is formed by a plurality of two-dimensional detectors arranged and receives only the main shadow of the X-ray beam profile formed by the pre-collimator and the main shadow of the penumbra An X-ray CT scanner, comprising: a reconstructing unit that reconstructs an X-ray CT image based on data detected by one detector array. 3. An X which irradiates a subject with an X-ray beam
A pre-collimator for narrowing the width of the X-ray beam in a slice direction orthogonal to the cross section of the subject sliced by the X-ray beam and interposed between the X-ray tube and the subject. And an X-ray CT scanner including an X-ray detector that receives the X-ray beam that has passed through the subject, wherein the X-ray detector includes a detection element array including a plurality of detection channels in the slice direction. At least one of the plurality of detection element arrays which is formed by a plurality of two-dimensional detectors arranged and receives only the main shadow of the X-ray beam profile formed by the pre-collimator and the main shadow of the penumbra A first acquisition mode for image reconstruction using data detected by the two element arrays and the umbra and half of the profile of the X-ray beam formed by the pre-collimator. Selecting means for receiving one of the second acquisition modes for performing image reconstruction using the data detected by at least one element array among the plurality of detection element arrays, which receives a shadow; An X-ray CT scanner, comprising: a scanning unit that executes scanning with the X-ray beam based on the acquisition mode selected by the selection unit and acquires the data. 4. The X-ray CT scanner according to claim 3, further comprising control means for controlling an aperture state of the pre-collimator according to the acquisition mode selected by the selection means. 5. A top plate that is movable in the slice direction and on which the subject is placed, and the total slice width of the designated detection element array for each scan by the X-ray beam during multi-scan, matching the total slice width 5. A determination means for determining the moving distance of the top, and a top controlling means for controlling the movement of the top based on the moving distance determined by this determining means. The X-ray CT scanner as described in one item. 6. A top plate that is movable in the slice direction and on which the subject is placed, and the designated detection for each rotation of the X-ray tube and the X-ray detector around the subject during helical scanning. Judgment means for judging the movement distance of the top plate according to the total width of the element row in the slice direction, and top plate control for controlling the movement of the top board based on the movement distance judged by this judgment means. An X-ray CT scanner according to any one of claims 1 to 4, further comprising: 7. The opening width of the pre-collimator in the slice direction is set to the X-axis according to the movement of the X-ray focal point of the X-ray tube.
2. A setting means for widening the line beam by an amount corresponding to the predicted maximum movement amount of the line beam in the slice direction.
The X-ray CT scanner according to claim 4. 8. A detection means for detecting an amount corresponding to a movement of an X-ray focal point of the X-ray tube, wherein the control means has an opening in the slice direction of the pre-collimator based on a detection amount of the detection means. At least one of the width, the position of the pre-collimator in the slice direction, and the position of the X-ray focal point of the X-ray tube in the slice direction, at least the designated detector array is used for the X-ray beam. An X-ray C according to claim 1, including means for controlling to receive the main shadow.
T scanner. 9. A detector that detects an amount corresponding to the movement of the X-ray focal point of the X-ray tube, and an opening width of the pre-collimator in the slice direction based on the amount detected by the detector.
At least one of the position of the pre-collimator in the slice direction and the position of the X-ray focal point of the X-ray tube in the slice direction, at least the at least one detection element row is the book of the X-ray beam. The X-ray CT according to claim 2, further comprising: a control unit that controls to receive a shadow.
Scanner. 10. A detecting means for detecting an amount corresponding to a movement of an X-ray focal point of the X-ray tube, an opening width of the pre-collimator in the slice direction based on a detected amount of the detecting means, and a pre-collimator's opening width. At least one of the position in the slice direction and the position in the slice direction of the X-ray focal point of the X-ray tube is configured to at least prevent movement of the profile of the X-ray beam incident on the X-ray detector. 4. The X according to claim 3, further comprising:
Line CT scanner. 11. A detection means for detecting an amount corresponding to a movement of an X-ray focal point of the X-ray tube, wherein the control means has an opening in the slice direction of the pre-collimator based on a detection amount of the detection means. At least one of the width, the position of the pre-collimator in the slice direction, and the position of the X-ray focal point of the X-ray tube in the slice direction of the profile of the X-ray beam incident on the X-ray detector. 5. A means for controlling to at least prevent movement.
The described X-ray CT scanner. 12. An X-ray tube that irradiates an X-ray beam toward a subject, and is interposed between the subject and the X-ray tube,
A pre-collimator that narrows the width of the X-ray beam in the slice direction orthogonal to the cross section of the subject sliced by the X-ray beam, and the X that has passed through the subject.
An X-ray CT scanner provided with an X-ray detector for receiving a beam of rays, wherein the X-ray detector is formed of a single slice detector in which a row of detection elements consisting of a plurality of detection channels is arranged in one row in a slice direction. , At least the opening width and position in the slice direction of the pre-collimator so that the detection element array receives only the main shadow of the main shadow and penumbra of the profile of the X-ray beam formed by the pre-collimator. An X-ray CT scanner comprising a control means for controlling one of them. 13. A top plate that is movable in the slice direction and on which the subject is placed, and the X-axis during multi-scan.
Judgment means for judging the feed pitch of the top plate according to the width in the slice direction of the detection element array for each scanning with a line beam, and movement of the top plate based on the feed pitch judged by this judgment means. The X-ray CT scanner according to claim 12, further comprising: a top plate control unit that controls the. 14. An X-ray tube that irradiates an X-ray beam toward a subject, and is interposed between the subject and the X-ray tube,
A pre-collimator that narrows the width of the X-ray beam in the slice direction orthogonal to the cross section of the subject sliced by the X-ray beam, and the X that has passed through the subject.
An X-ray detector that receives a X-ray beam and a post-collimator that is interposed between the subject and the X-ray detector and that narrows the width in the slice direction of the X-ray beam that is incident on the X-ray detector. In an X-ray CT scanner provided with the X-ray detector, the X-ray detector is formed by a single-slice detector in which a row of detection elements consisting of a plurality of detection channels is arranged in a slice direction, and the X-ray formed by the pre-collimator. A part or penumbra of the main shadow and penumbra of the line beam is cut, and the opening width of the post collimator in the slice direction is adjusted so that only the main shadow is incident on the X-ray detector. An X-ray CT scanner comprising control means for controlling. 15. An X-ray tube that irradiates an X-ray beam toward a subject, and is interposed between the subject and the X-ray tube,
A pre-collimator that narrows the width of the X-ray beam in the slice direction orthogonal to the cross section of the subject sliced by the X-ray beam, and the X that has passed through the subject.
An X-ray detector that receives a X-ray beam and a post-collimator that is interposed between the subject and the X-ray detector and that narrows the width in the slice direction of the X-ray beam that is incident on the X-ray detector. In an X-ray CT scanner provided with the X-ray detector, the X-ray detector is formed by a single-slice detector in which a row of detection elements including a plurality of detection channels is arranged in a slice direction, and the X-ray formed by the pre-collimator. A first acquisition mode for image reconstruction using the data detected by the array of detectors which receives only the main shadow of the beam profile and the main shadow of the penumbra; Selecting means for selecting one of the second acquisition modes for performing image reconstruction using the data detected by the detector array that receives the penumbra; And a control means for controlling the opening width in the slice direction of the post collimator according to the mode selected by the selection means.