JP2007037994A - X-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of scattered radiation originating in the X-ray of the other party in a multi-tube type X-ray CT apparatus equipped with a plurality of pairs of an X-ray tube and detector. <P>SOLUTION: The X-ray CT apparatus is equipped with a plurality of X-ray tubes 121, 122, a plurality of X-ray detectors 131, 132 corresponding to the plurality of X-ray tubes, respectively, a support mechanism 11 for supporting the X-ray tubes and the X-ray detectors rotatably around a single rotation shaft, a reconstruction part 23 for reconstructing image data on the basis of outputs from the X-ray detectors, and a plurality of filters 171, 172 which are respectively provided in the plurality of X-ray tubes and have characteristics in which an X-ray path length changes along a curve approximate to an inverted Gaussian curve from the rotation center to both ends of an X-ray beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-tube type X-ray CT apparatus and filter equipped with a plurality of pairs of X-ray tubes and detectors.

  An X-ray CT apparatus (X-ray computed tomography apparatus) reconstructs a tomographic image based on a plurality of projection data sets collected from a plurality of directions by rotating a pair of an X-ray tube and a detector. A multi-tube type X-ray CT apparatus is equipped with a plurality of pairs. A multi-tube type X-ray CT apparatus is described in Patent Document 1, for example. Patent Document 1 has an X-ray tube for treatment and an X-ray tube for data collection.

  By the way, in the multi-tube type X-ray CT apparatus, as shown in FIG. 4, the scattered radiation derived from the X-rays generated in one pair of X-ray tubes 122 (121) is converted into the other pair of X-ray detectors. The problem is that it is detected at 131 (132).

  In particular, the adverse effect is not small because the scattered radiation generated at the parts β1 and β2 on the surface of the subject P directly reaches the X-ray detectors 131 and 132 without being attenuated by the subject P. .

Filters (also referred to as wedge filters) F1 and F2 are disposed between the X-ray tubes 121 and 122 and the subject P. As shown in FIG. 5A, the filters F1 and F2 have a cross-sectional structure in which the center is thin, the periphery is thick, the thickness is expanded, and the arc is changed according to the change in the angle θ. More specifically, the filters F1 and F2 are designed so that the intensity of X-rays transmitted through the filters F1 and F2 and the uniform cylindrical phantom is substantially constant as shown in FIG. 5B.
JP 2004-73406 A

  An object of the present invention is to reduce the influence of scattered radiation derived from a counterpart X-ray in a multi-tube type X-ray CT apparatus equipped with a plurality of pairs of an X-ray tube and a detector.

A first aspect of the present invention includes a plurality of X-ray tubes, a plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes, and the X-ray tube and the X-ray detector. A support mechanism that supports the periphery of the X-ray detector, a reconstruction unit that reconstructs image data based on the output of the X-ray detector, and the plurality of X-ray tubes. A plurality of filters having a characteristic that changes in a curved manner by approximating an inverted Gaussian curve from the center toward both ends of the X-ray.
A second aspect of the present invention includes a plurality of X-ray tubes, a plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes, and the X-ray tube and the X-ray detector. A support mechanism that rotatably supports the periphery, a reconstruction unit that reconstructs image data based on the output of the X-ray detector, and an X-ray that is provided in each of the plurality of X-ray tubes and passes through the filters. A plurality of filters having characteristics in which the intensity of the line changes in a curved manner by approximating a Gaussian curve from the rotation center toward both ends.
According to a third aspect of the present invention, a plurality of X-ray tubes, a plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes, and the X-ray tube and the X-ray detector are combined into a single rotation axis. A support mechanism that supports the periphery of the X-ray detector, a reconstruction unit that reconstructs image data based on the output of the X-ray detector, and a plurality of X-ray tubes, and the filter and the uniform cylindrical phantom. And a plurality of filters having a characteristic that the intensity of the X-rays transmitted through and decreases in a curved manner from the center of rotation toward both ends.
According to a fourth aspect of the present invention, a plurality of X-ray tubes, a plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes, and the X-ray tube and the X-ray detector are combined into a single rotational axis. A support mechanism that rotatably supports the periphery, a reconstruction unit that reconstructs image data based on the output of the X-ray detector, and an X-ray that is provided in each of the plurality of X-ray tubes and passes through the filter In the central portion less than 10 cm from the rotation center, the strength exceeds 90% of the maximum strength of the rotation center, and in the peripheral portion exceeding 20 cm from the rotation center, it is less than 50% of the maximum strength of the rotation center. And a plurality of filters having characteristics.

  According to the present invention, in a multi-tube type X-ray CT apparatus equipped with a plurality of pairs of an X-ray tube and a detector, it is possible to reduce the influence of scattered rays derived from the counterpart X-ray.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram showing the overall configuration of an embodiment of the X-ray CT apparatus of the present invention. In FIG. 1, the X-ray CT apparatus (computed tomography apparatus) of this embodiment includes a gantry 10, a computer apparatus 20, and a bed (not shown). The gantry 10 is a multi-tube type, and a plurality of scanners including a pair of an X-ray tube and an X-ray detector are mounted. In the present embodiment, the description will be made with a two-tube type.

  The gantry 10 is provided with a rotating mount 11. The rotating gantry 11 is rotated around the rotation axis R by a rotating mechanism. The rotary mount 11 has a scanner composed of a first pair in which the X-ray tube 121 and the X-ray detector 131 are arranged to face each other and a second pair in which the X-ray tube 122 and the X-ray detector 132 are arranged to face each other. An opening is formed in the central portion of the rotating gantry 11 arranged at an angle (for example, an angle of 90 degrees). A subject P placed on the couch top 14 is inserted into the opening.

  The X-ray detectors 131 and 132 are provided with collimators 151 and 152 for limiting incident X-rays facing the X-ray tubes 121 and 122, respectively. Further, slits 161 and 162 are arranged on the X-ray tubes 121 and 122 and the rotation axis R. Further, the X-ray tubes 12 and 122 are respectively provided with scattered radiation reducing filters (also called wedge filters) 171 and 172. The filters 171 and 172 are detachably supported by the filter support mechanisms 173 and 174, respectively. It can be replaced with another filter having a shape suitable for the shape of the subject.

  Outputs of the X-ray detectors 131 and 132 are sent to data collection units 181 and 182, respectively, and supplied to a preprocessing unit (described later) of the computer apparatus 20. In addition, the gantry 10 is provided with a control unit 19 that performs control of tube voltages of the X-ray tubes 121 and 122, rotation control of the rotary mount 11, and the like.

  On the other hand, the computer apparatus 20 has a central control unit 21 to which a preprocessing unit 22, a reconstruction processing unit 23, an image display unit 24, an operation unit 25, and the like are connected via a data / control bus line 201. Yes. X-rays transmitted through the subject P are converted into electric signals by the X-ray detectors 131 and 132, amplified by the data acquisition units 181 and 182 and converted into digital data, and projection data is supplied to the preprocessing unit 22. The The preprocessing unit 22 performs processing such as correction of signal intensity and correction of signal loss, and outputs photographing data on the bus line 201.

  The central control unit 21 controls the operation of each unit of the computer device 20 and the control unit 19 of the gantry 10. The reconstruction processing unit 23 reconstructs tomographic image data based on the projection data. The image display unit 24 includes a display that displays medical images and the like, and the operation unit 25 inputs information such as a patient's condition and examination method by a doctor.

  FIG. 2 shows an enlarged configuration of the main part of the present embodiment. A scanner including a first pair of an X-ray tube 121 and an X-ray detector / detector 131, an X-ray tube 122, and an X-ray detector. 1 shows the configuration of a scanner including 132 second pairs. In FIG. 2, the first pair of the X-ray tube 121 and the X-ray detector 131 is representatively illustrated, but the second pair of the X-ray tube 122 and the X-ray detector 132 is the first pair. Since the configuration is the same except that the photographing reference line (X axis) is shifted by 90 ° with respect to the pair, the illustration is omitted in FIG.

  In FIG. 2, a slit 161 is disposed facing the X-ray tube 121. The thickness of the X-ray bundle is determined by the opening degree of the slit 161. The maximum value of the X-ray divergence angle θ is determined in advance according to the number of channels × channel pitch of the X-ray detector 131. The X-ray divergence angle θ is defined as an angle formed by the X-axis (imaging reference line) and the X-ray beam from the X-ray focal point f. The X axis passes through the X-ray focal point f of the X-ray tube 121 and the center point C of the detection surface of the X-ray detector 131. The Z axis coincides with the rotation axis R. At the time of imaging, the subject P is arranged so that the body axis of the subject P approximates the Z axis. The Y axis is an axis orthogonal to the X axis and the Z axis. The XYZ axes constitute a rotating coordinate system centered on the Z axis.

  The X-ray detector 131 has a large number of detection elements arranged in the channel direction (CH) and the column direction (Z-axis direction). The channel direction (CH) is defined as the direction of an arc centered on the X-ray focal point f. The X-ray detector 131 detects the X-ray bundle xl that has passed through the subject P.

  The X-ray detector 131 is provided with a collimator 151 (see FIG. 1). The collimator 151 has a plurality of thin collimator plates made of metal such as molybdenum arranged in the direction of focusing on the focal point f of the X-ray tube 121 constituting the pair. The collimator 151 limits the X-ray direction incident on the X-ray detector 131 to the direction from the focal point f of the X-ray tube 121 constituting the pair. Furthermore, the multi-tube type X-ray CT apparatus has a smaller rotation angle necessary to obtain a reconstructed image than a single tube type, and the time required for acquiring projection data can be shortened, thereby improving the time resolution. be able to. Therefore, it is suitable for diagnosing the heart part of the subject P and a site with movement around it.

  In addition, a filter 171 for reducing scattered radiation is disposed between the X-ray tube 121 and the slit 161. The filter 171 is detachably supported by the filter support mechanism 173. The filter 171 compensates for the difference in X-ray absorption between the periphery and the center of the subject P by reducing the low energy component that is absorbed by the subject P and does not reach the detector 131. It has a function of aligning the range as much as possible around and around the subject P.

  Furthermore, the filter 171 has a function of effectively reducing the influence of scattered radiation derived from X-rays generated in the other pair of X-ray tubes 122 as a function unique to the present embodiment. The X-rays generated in the other pair of X-ray tubes 122 are scattered on the body surface of the subject, and the scattered radiation that directly enters the detector 131 without being attenuated causes the most adverse effects. Scattered rays scattered by an open portion (part β2 of the body surface in FIG. 4) viewed from both the X-ray tube 122 and the detector 131 do not pass through the subject P and are directly attenuated without being attenuated. It is detected by the detector 131.

  Although the filter 171 will be described in detail later, typically, as shown in FIG. 3, a concave portion 17 a is formed in a portion facing the X-ray tube 121, and the concave portion has a thin central portion and a thick peripheral portion. The curved surface has a geometric shape that rises sharply from the bottom to the top.

  Therefore, X-rays from the X-ray tube have a high transmittance at the central portion of the filter 171 and a low transmittance at the peripheral portion. That is, the X-rays transmitted through the filter 171 have a large amount of X-rays incident on the center of the pair of X-ray detectors 131 in the channel direction, and the X-rays incident on the periphery in the channel direction are reduced.

  Next, the effects of the filters 171 and 172 will be described with reference to FIGS. 4, 5, 6, and 7. FIG. 4 is a diagram for explaining the influence of scattered radiation from the other pair of X-ray tubes, showing the case where conventional filters F1 and F2 are used, and FIGS. 6 and 7 are filters 171 and 172 of the present embodiment. It is a figure explaining the mitigation effect of the scattered radiation at the time of using.

In the case of FIG. 4, when the diagnostic target of the subject P is p1 (for example, a portion that is the heart and is shown dark in the figure) and the subject surface is p2, the X-ray tube 121 passes through the filter F1 and the slit 161. The irradiated X-rays are detected by the X-ray detector 131, and the X-rays irradiated from the X-ray tube 122 through the filter F 2 and the slit 162 are detected by the X-ray detector 132. At this time, the range of X-rays transmitted through the main organ (target p1) is set to the main scanning range α1, α2. The change in the thickness of the conventional filters F1, F2 is the same as that of the filters F1, F2 and the circle as shown in FIG. 5B. As shown in FIG. 5A, the inner surface is designed to have a substantially arc shape so that the intensity of the X-ray transmitted through the columnar uniform phantom has a constant value with respect to the X-ray divergence angle θ.

  On the other hand, scattered rays derived from X-rays from the X-ray tube 122 which is the other pair enter the detector 131. Similarly, scattered rays derived from X-rays from the X-ray tube 121 which is the other pair enter the detector 132. At this time, the scattered rays that particularly affect the partner are X-rays scattered by the open surface portions β1 and β2. Scattered rays scattered outside the surface portions β1 and β2 are less affected because they are attenuated in the subject.

  When the filters 171 and 172 shown in FIG. 3 are arranged in the X-ray tubes 121 and 122 as shown in FIG. 6, the thickness of the peripheral parts of the filters 171 and 172 is considerably thicker than that of the center part. The transmittance of the line is considerably smaller in the peripheral portion than in the central portion, and is reduced to about several to 50% of the central portion in the peripheral portion, for example.

  That is, the filters 171 and 172 of the present embodiment have a structure in which the thickness is thin at the center as shown in FIG. X-rays have a high transmittance at the center of the filter 171 and a lower transmittance at the periphery than the conventional filters F1 and F2. That is, the X-rays transmitted through the filter 171 have a large amount of X-rays incident on the center in the channel direction of the pair of X-ray detectors 131, and the X-rays incident on the peripheral part in the channel direction are larger than those of the conventional filters F1 and F2. It will be reduced.

  Therefore, as shown in FIG. 7B, when the subject P is inserted, the intensity of the X-rays detected by the pair of X-ray detectors 131 and 132 is strong at the center in the channel direction (CH), It becomes weaker toward the periphery. Therefore, imaging can be performed with almost no reduction in the dose of the subject P near the main organ portion p1. Further, the X-ray dose irradiated on the surface β2 of the subject P is greatly reduced, and the scattered radiation at the portions indicated by β1 and β2 is also greatly reduced. Further, even if the X-ray transmittance in the peripheral portion is reduced, there is no particular problem in diagnosing major organs.

  Thereby, when the subject P enters, the scattered rays that adversely affect the detection results of the main scanning ranges α1 and α2 detected by the X-ray detectors 131 and 132 can be considerably reduced. Further, the main organ can be diagnosed appropriately without changing the dose to the vicinity of the main organ portion p1, and the exposure dose to the epidermis that has a large adverse effect on the human body can be reduced.

  8A, 8B, and 8C show the structures of the filters 171 and 172 according to another embodiment of the present invention. When the subject P is irradiated with X-rays, the transmissivity differs from organ to organ. Therefore, as shown in FIG. 6, a plurality of filters 171 and 172 having different curvatures of the curved surface 17a are prepared. By making such a filter selectable, a more accurate diagnosis becomes possible.

  For example, a plurality of types of filters are prepared in the X-ray CT apparatus, and any one type of filter is electrically selected when performing imaging. At this time, in order to reduce the influence of scattered radiation, the filters 171 and 172 have such a shape that the thickness of the central portion is small and the thickness of the peripheral portion is thick, and as shown in FIG. The X-ray intensity detected by the detectors 131 and 132 has such a characteristic that it is strong at the center in the channel direction (CH) and weak at the periphery.

  The structure of the filter 171 will be described in more detail. Since the structure of the filter 172 is equivalent to the structure of the filter 171, description is abbreviate | omitted. FIG. 9 shows a change of the X-ray path length PL of the filter 171 with respect to the spread angle θ. The X-ray path length PL corresponds to the thickness, and more precisely is defined as the distance that the X-ray beam passes through the filter 171 as shown in FIG. 7A. θ1 represents the divergence angle of the X-ray beam in contact with a circle having a radius of 10 cm with the rotation axis R as the center. θ2 represents the divergence angle of the X-ray beam in contact with a circle having a radius of 20 cm with the rotation axis R as the center. In the filter 171, the X-ray path length PL gradually changes from the rotation axis R toward both ends of the X-ray, that is, along the curve approximated to the inverted shape of the Gaussian curve as the absolute value of the spread angle θ increases. It has a structure with characteristics. Compared to a conventional filter that approximates a circular arc, the X-ray path length PL of the filter 171 changes with little difference from the conventional one up to the divergence angle ± θ1, but becomes steeply longer in the range beyond the divergence angle ± θ1. .

  FIG. 10 shows changes in the intensity of X-rays transmitted through the filter 171 with respect to the spread angle θ. In the filter 171, the intensity of the X-ray transmitted through the filter 171 gradually changes along the curve approximated to a Gaussian curve from the rotation axis R toward both ends of the X-ray, that is, as the absolute value of the spread angle θ increases. It has the structure which has the characteristic to do. Compared with a conventional filter that approximates a circular arc, the intensity of X-rays that have passed through the filter 171 changes with little difference from the conventional one up to the divergence angle ± θ1, but is steep in the range beyond the divergence angle ± θ1. descend. More specifically, the filter 171 has a periphery in which the intensity of the X-ray transmitted through the filter 171 exceeds 90% of the maximum intensity Ic and exceeds 20 cm from the rotation axis R in the central portion where the intensity is less than 10 cm from the rotation axis R. The portion has a characteristic that it is less than 50% of the maximum intensity Ic. In an example of a conventional filter, at the position 20 cm from the rotation axis R, it is almost the end portion that exceeds 50% of the maximum intensity Ic and less than 50% of the maximum intensity Ic.

  FIG. 11 shows the change of the intensity of X-rays transmitted through the filter 171 and the cylindrical uniform phantom with respect to the spread angle θ. The filter 171 has a characteristic that the intensity of the X-ray transmitted through the filter 171 and the uniform phantom gradually decreases in a curved manner from the rotation axis R toward both ends of the X-ray, that is, as the absolute value of the spread angle θ increases. It has the structure which has. Compared with the conventional arc-shaped filter, the intensity of the X-rays transmitted through the conventional filter and the uniform phantom shows a substantially constant value, but the X-rays transmitted through the filter 171 and the uniform phantom of the present embodiment The intensity is not a constant value but gradually decreases in a range exceeding the spread angle ± θ1. More specifically, in the filter 171, the intensity of the X-ray transmitted through the filter 171 and the uniform phantom gradually changes in a range between the maximum intensity Ic and any value between 80% and 20% thereof. It has the characteristic.

  As described above, the scattered radiation scattered by the open portion (part β2 of the body surface in FIG. 4) viewed from both the X-ray tube 122 and the detector 131 is strongly influenced by the output from the detector 131. . Accordingly, as illustrated in FIG. 12, the characteristic and novel features described above are included in a part of the filter 171 corresponding to the open part β2, that is, a half part of the half angle of the detector 132 on the side of the detector 132. A path length similar to that of the prior art is applied to the portion of the -30 ° to 0 ° divergence angle that is approximately half on the opposite side of the open portion β2, which has less influence and gives a characteristic that changes along the curve that causes reverse reversal. Gives a characteristic that changes in an arc. In this example, it is possible to suppress the influence of scattered rays from the other pair of X-ray tubes and to suppress a decrease in SN. The filter 172 has opposite characteristics on the left and right.

  FIG. 13 shows a modification of the filter support mechanism 173. Since the filter support mechanism 174 has the same structure as the filter support mechanism 173, description thereof is omitted. The filter support mechanism 173 has a structure equipped with a plurality of filters having different characteristics, and a mechanism for sliding the plurality of filters in the Z-axis direction. Any filter is arranged between the X-ray tube and the detector by the slide. Thereby, any filter can be selectively used. Preferably, the filter support mechanism 173 is equipped with the following four filters.

  The first filter has characteristics peculiar to the present embodiment in which the intensity of X-rays transmitted through the filter gradually changes along a curve approximating a Gaussian curve as the absolute value of the spread angle θ increases. The range in which the intensity of the X-rays transmitted through the filter exceeds 90% of the maximum value Ic is relatively narrow, for example, a radius of 8 cm.

  The second filter has characteristics peculiar to the present embodiment in which the intensity of X-rays transmitted through the filter gradually changes along a curve approximating a Gaussian curve as the absolute value of the spread angle θ increases. The range in which the intensity of the X-rays transmitted through the filter exceeds 90% of the maximum value Ic is a relatively wide range, for example, a radius of 10 cm.

  The third filter has characteristics similar to those of the prior art in which the intensity of X-rays transmitted through the filter spreads and gradually changes along an arc shape as the absolute value of the angle θ increases, and transmitted through the filter. The range in which the X-ray intensity exceeds 90% of the maximum value Ic is relatively wide, for example, a radius of 16 cm.

  The fourth filter has characteristics similar to those of the prior art in which the intensity of X-rays transmitted through the filter spreads and gradually changes along an arc shape as the absolute value of the angle θ increases, and transmitted through the filter. The range in which the intensity of X-rays exceeds 90% of the maximum value Ic is relatively narrow, for example, a range with a radius of 10 cm.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

FIG. 1 is an overall configuration diagram of an X-ray CT apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing a configuration of a main part of the X-ray CT apparatus of FIG. FIG. 3 is an external view of the filter of FIG. FIG. 4 is an explanatory diagram of the influence of conventional scattered radiation. FIG. 5A is a diagram illustrating a cross-sectional shape of a conventional filter. FIG. 5B is a diagram illustrating a change in the intensity of X-rays transmitted through the filter and the uniform phantom of FIG. 5A with respect to the spread angle θ. FIG. 6 is a supplementary diagram for explaining the operation of the filter of FIG. FIG. 7A is an explanatory diagram of the X-ray path length. FIG. 7B is a diagram showing a change of the X-ray intensity corresponding to FIG. 7A with respect to the channel. FIG. 8A is a diagram showing a cross-sectional shape of the filter of FIG. FIG. 8B is a diagram showing another cross-sectional shape of the filter of FIG. 1. FIG. 8C is a diagram showing still another cross-sectional shape of the filter of FIG. 1. FIG. 9 is a diagram showing a change of the X-ray path length PL of the filter of FIG. 1 with respect to the spread angle θ. FIG. 10 is a diagram illustrating a change in the intensity of X-rays transmitted through the filter of FIG. 1 with respect to the spread angle θ. FIG. 11 is a diagram illustrating a change in the intensity of X-rays transmitted through the filter and the uniform phantom of FIG. 1 with respect to the spread angle θ. FIG. 12 is a diagram showing a change of the X-ray path length PL with respect to the spread angle θ regarding a modification of the filter of FIG. FIG. 13 is a diagram showing another configuration example of the filter support mechanism of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Gantry, 20 ... Computer apparatus, 11 ... Rotary mount, 121, 122 ... X-ray tube, 131, 132 ... X-ray detector, 14 ... Top plate, 151, 152 ... Collimator, 161, 162 ... Slit, 171, 172 ... Wedge filter, 173, 174 ... Filter support mechanism, 181,182 ... Data collection unit, 19 ... Control unit, 21 ... Central control unit, 22 ... Pre-processing unit, 23 ... Reconstruction processing unit, 24 ... Image display unit 25, operation unit, 201, data / control bus line.

Claims (14)

A plurality of X-ray tubes;
A plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes;
A support mechanism for rotatably supporting the X-ray tube and the X-ray detector around a single rotation axis;
A reconstruction unit for reconstructing image data based on the output of the X-ray detector;
A plurality of filters provided in each of the plurality of X-ray tubes and having a characteristic in which an X-ray path length approximates an inverted Gaussian curve from the center of rotation toward both ends of the X-ray and changes in a curved manner. X-ray CT apparatus characterized by this. The X-ray CT apparatus according to claim 1, further comprising a mechanism for attaching and detaching the filter. A plurality of slits for limiting the X-ray thickness provided in each of the plurality of X-ray tubes;
The X-ray CT apparatus according to claim 1, wherein the filter is disposed between the X-ray tube and the slit. 2. The filter according to claim 1, further comprising a characteristic in which the intensity of the X-ray transmitted through the filter changes in a curved manner by approximating a Gaussian curve from the center of rotation toward both ends of the X-ray. The X-ray CT apparatus described. 2. The X according to claim 1, wherein each of the filters further has a characteristic that the intensity of X-rays transmitted through the filter and a uniform cylindrical phantom decreases in a curved manner from the rotation center toward both ends. Line CT device. Each filter has an intensity of X-rays transmitted through the filter exceeding 90% of the maximum intensity of the rotation center in the central portion less than 10 cm from the rotation center, and in the peripheral portion exceeding 20 cm from the rotation center. The X-ray CT apparatus according to claim 1, further having a characteristic of being less than 50% of the maximum intensity of the rotation center. 2. The X-ray CT apparatus according to claim 1, wherein each of the filters has a curved shape in which a thickness of a central portion is thin and a thickness gradually increases toward a peripheral portion. A plurality of X-ray tubes;
A plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes;
A support mechanism for rotatably supporting the X-ray tube and the X-ray detector around a single rotation axis;
A reconstruction unit for reconstructing image data based on the output of the X-ray detector;
A plurality of filters provided in each of the plurality of X-ray tubes and having a characteristic in which the intensity of the X-rays transmitted through the filters changes in a curved manner by approximating a Gaussian curve from the rotation center toward both ends. X-ray CT apparatus characterized by performing. A plurality of X-ray tubes;
A plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes;
A support mechanism for rotatably supporting the X-ray tube and the X-ray detector around a single rotation axis;
A reconstruction unit for reconstructing image data based on the output of the X-ray detector;
A plurality of filters provided on each of the plurality of X-ray tubes, each having a characteristic that the intensity of X-rays transmitted through the filter and a uniform cylindrical phantom decreases in a curved manner from the rotation center toward both ends; X-ray CT apparatus characterized by performing. A plurality of X-ray tubes;
A plurality of X-ray detectors respectively corresponding to the plurality of X-ray tubes;
A support mechanism for rotatably supporting the X-ray tube and the X-ray detector around a single rotation axis;
A reconstruction unit for reconstructing image data based on the output of the X-ray detector;
The intensity of the X-rays respectively provided in the plurality of X-ray tubes and transmitted through the filter exceeds 90% of the maximum intensity of the rotation center at a central portion less than 10 cm from the rotation center, and 20 cm from the rotation center. An X-ray CT apparatus comprising: a plurality of filters having a characteristic that a peripheral portion exceeding 1 is less than 50% of the maximum intensity of the rotation center. A filter provided in an X-ray tube of an X-ray CT apparatus, characterized in that the X-ray path length has a characteristic that approximates an inverted Gaussian curve from the center toward both ends. A filter provided in an X-ray tube of an X-ray CT apparatus, characterized in that the intensity of X-rays transmitted through the filter has a characteristic that approximates a Gaussian curve from the center toward both ends. A filter provided in an X-ray tube of an X-ray CT apparatus, characterized in that the intensity of X-rays transmitted through the filter and a uniform cylindrical phantom decreases in a curved manner from the center toward both ends. The intensity of the X-ray transmitted through the filter exceeds 90% of the maximum intensity of the center in the central portion less than 10 cm from the center, and less than 50% of the maximum intensity of the center in the peripheral portion exceeding 20 cm from the center. The filter provided in the X-ray tube of the X-ray CT apparatus characterized by having the following characteristics.

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