JP4708147B6 - X-ray CT system - Google Patents

Description

  The present invention relates to an X-ray CT apparatus, and more particularly to an apparatus for detecting an X-ray beam by a detector having a plurality of X-ray sensor arrays.

  The X-ray CT apparatus is an apparatus that rotates an X-ray beam that passes through a subject and reconstructs a tomographic image or a three-dimensional image of the subject based on data obtained thereby (see Patent Document 1). In addition to being used for diagnosing human diseases, the X-ray CT apparatus is also used for measuring animals and other objects other than the human body for the purpose of research and experiments. For example, in a pharmaceutical company, an X-ray CT apparatus is used for verification of animal experiments. In this case, examples of the subject include small animals such as guinea pigs, rats, mice, and hamsters.

  The original X-ray CT apparatus mainly obtains one piece of tomographic data by a detector in which X-ray sensors are arranged in a line, and constructs a tomographic image of a subject from the tomographic data.

  On the other hand, in recent years, a multi-slice type X-ray CT apparatus that detects an X-ray beam by a plurality of X-ray sensors arranged in a lattice form has appeared. In other words, a plurality of tomographic data is obtained by using a multi-slice (multiple row) detector composed of a plurality of X-ray sensors arranged in a grid by arranging a plurality of X-ray sensor rows that originally existed in only one row. X-ray CT apparatuses constituting the above are becoming widespread.

JP 2004-121297 A

  By using a multi-slice X-ray CT apparatus, a plurality of tomographic data can be obtained by rotating the X-ray beam once, and a three-dimensional stereoscopic image can be obtained from the plurality of tomographic data. . In particular, a high-definition stereoscopic image can be obtained by increasing the number of X-ray sensors arranged in a grid pattern (for example, using a multi-slice detector having several thousand rows).

  On the other hand, in the multi-slice X-ray CT apparatus, the calculation time for image forming processing cannot be ignored. In particular, when calculating diagnostic parameters such as bone density of a subject from tomographic data obtained from each X-ray sensor array, it takes time to calculate the diagnostic parameters in addition to the image forming processing time.

  However, when calculating diagnostic parameters such as bone density, it is often unnecessary to use tomographic data obtained from all X-ray sensor arrays. For example, even in an apparatus having thousands of X-ray sensor arrays, diagnostic parameters can be calculated with sufficient accuracy by using tomographic data obtained from about a hundred X-ray sensor arrays. Is possible. That is, when calculating the diagnostic parameters, it is not necessary to use all of the X-ray sensor arrays necessary for constructing a high-definition stereoscopic image.

  The present invention has been made in such a background, and an object of the present invention is to analyze a technique for analyzing only minimum necessary tomographic data in an X-ray CT apparatus that detects an X-ray beam by a plurality of X-ray sensor arrays. It is to provide.

  In order to achieve the above object, an X-ray CT apparatus according to a preferred aspect of the present invention includes an X-ray generator that generates an X-ray beam that passes through a subject, and a grating formed by a plurality of X-ray sensor arrays. An X-ray detection unit that detects the X-ray beam by a plurality of X-ray sensors in an array, and an analysis unit that analyzes tomographic data of the subject obtained for each X-ray sensor array, The analyzing unit analyzes only a part of tomographic data among a plurality of tomographic data obtained from a plurality of X-ray sensor arrays.

  In a preferred aspect, the analysis unit calculates a diagnostic parameter of the subject from each of a plurality of pieces of tomographic data obtained in stages, and the diagnostic parameters until the plurality of diagnostic parameters calculated in stages satisfy a predetermined convergence condition. Is calculated. In a preferred aspect, the predetermined convergence condition is defined by a change rate of a plurality of diagnostic parameters calculated in stages. In a preferred aspect, the predetermined convergence condition is defined by variation coefficients of a plurality of diagnostic parameters calculated in stages. In a preferred aspect, each of the diagnostic parameters is a bone density of a subject. In a preferred aspect, each of the diagnostic parameters is a fat mass of a subject.

  According to the present invention, it is possible to analyze only necessary minimum tomographic data in an X-ray CT apparatus that detects an X-ray beam by a plurality of X-ray sensor arrays. For example, by analyzing only the tomographic data that can ensure the reliability of the analysis result, it is possible to significantly reduce the calculation time for image reconstruction.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows an example of an X-ray CT apparatus. This X-ray CT apparatus is an apparatus suitable for CT measurement of small animals such as mice, rats, mice, guinea pigs, and hamsters. This X-ray CT apparatus is roughly divided into a measurement unit 10 and a calculation control unit 12.

  The measurement unit 10 has a main body 16 having a gantry 18. An opening is formed in the upper surface 16A of the main body 16, and an arm 26 projects upward from the opening. The arm 26 forms a part of a slide mechanism described later. The arm 26 is connected to the container 24 and slides in the direction of the central axis.

  On the other hand, measurement units (X-ray generator, X-ray detector), which will be described later, are accommodated in the gantry 18 and rotate around the rotation center axis. A hollow portion 18A is formed in the central portion of the gantry 18 in the direction of the rotation center axis.

  The container 24 is a capsule that houses a small animal as a subject, and the container 24 has a substantially cylindrical shape in the present embodiment, and is arranged in a state in which the container center axis coincides with the rotation center axis. Specifically, the base end portion 76 of the container 24 is detachably attached to the upper end portion of the arm 26 described above. In this case, examples of the attachment / detachment mechanism include various engagement mechanisms or screwing mechanisms. As described above, the container 24 has a hollow cylindrical shape, and a small animal is disposed therein. With such a configuration, the body hair of the small animal directly contacts the gantry 18. Can be prevented. In addition, it is possible to prevent the problem that small animal excrement or detached hair is released to the outside. Furthermore, since it becomes possible to restrain a small animal as will be described later, problems such as image blurring when a CT image is reconstructed can be prevented. It is desirable to prepare and selectively use a plurality of types of containers having different sizes and shapes.

  After the container 24 is attached to the arm 26, the arm 26 is driven forward along the direction of the rotation center axis, whereby the container 24 is inserted into the cavity 18A of the gantry 18. At this time, the container 24 is positioned so that the X-ray beam is set with respect to the cross section at a predetermined position in the subject. Further, such a measurement position may be changed continuously or stepwise as necessary.

  An operation panel 20 is provided on the upper surface 16A of the main body 16, and the operation panel 20 includes a plurality of switches, indicators, and the like. Using this operation panel 20, the user can operate the operation of the apparatus at the measurement site. A plurality of casters 22 are provided below the main body 16. Incidentally, the height of the measurement unit 10 is, for example, 100 cm.

  Next, the arithmetic control unit 12 will be described. The arithmetic control unit 12 is electrically connected to the measurement unit 10 by a cable 14. The measurement unit 10 and the calculation control unit 12 may be provided in the same room, or may be installed in different places. Moreover, the measurement part 10 and the calculation control part 12 may be formed integrally. For example, the calculation control unit 12 may be incorporated in the apparatus housing of the measurement unit 10. The arithmetic control unit 12 includes an ordinary computer system, and specifically includes a processor 30, a display 32, a keyboard 36, a mouse 38, a storage device 34, a printer 40, and the like. The operation control unit 12 controls the operation of the measurement unit 10, and the configuration of CT images and the calculation of diagnostic parameters are performed based on data transmitted from the measurement unit 10.

  FIG. 2 is a block diagram showing the components of the X-ray CT apparatus shown in FIG. An X-ray generator 52 is provided on one side and an X-ray detector 60 is provided on the other side with the rotation center axis O therebetween. A collimator 54 is provided on the irradiation side of the X-ray generator 52. The X-ray generator 52 generates a three-dimensional divergent (cone beam-shaped) X-ray beam 56. On the other hand, the X-ray detector 60 includes a plurality of X-ray sensors arranged in a grid pattern in which a plurality of (for example, 64) X-ray sensor arrays in which a plurality of (for example, 512) X-ray sensors are arranged in a line. ing. Incidentally, the plurality of X-ray sensors constituting each X-ray sensor array may be arranged linearly or in an arc shape. In FIG. 2, the high voltage source used with the X-ray generator 52 and the data processing circuit used with the X-ray detector 60 are not shown.

  In FIG. 2, reference numeral 58 denotes an effective field of view. This is a circular region in which a CT image can be formed when the X-ray beam 56 is rotationally scanned. Incidentally, the effective visual field 58 is determined according to the positional relationship between the subject or the rotation center axis and the X-ray generator 52 and the X-ray detector 60. In this embodiment, since a displacement mechanism 62 described below is provided, it is possible to mechanically vary the magnification of the CT image by changing their positional relationship.

  That is, the X-ray generator 52 and the X-ray detector 60 are connected to the displacement mechanism 62, and the displacement mechanism 62 maintains the distance between the X-ray generator 52 and the X-ray detector 60. (That is, the measurement unit) has a function of displacing in the beam axis direction of the X-ray beam 56. In this case, the rotation center axis O is not changed, that is, the magnification can be changed by moving the measurement unit without moving the container described above. The displacement mechanism 62 includes a motor 62A for generating a displacement force.

  The gantry rotating mechanism 66 is a mechanism that rotates the entire structure including a displacement mechanism mounted thereon by rotating a rotating base described later. Since the measurement unit is mounted on the displacement mechanism 62, the measurement unit positioned at a desired position by the displacement mechanism 62 is rotationally driven while maintaining the position. The gantry rotating mechanism 66 has a motor 66A for generating the driving force.

  The slide mechanism 68 is a moving mechanism that slides the arm 26 shown in FIG. 1, and the driving force is generated by the motor 68A. The operation panel 20 is provided on the upper surface of the main body as described above. The operation panel 20 may be connected to a local controller (not shown) provided on the measurement unit 10 side so that the local controller and the arithmetic control unit 12 communicate with each other.

  Incidentally, although various mechanisms 62, 66, 68 and the like are shown in FIG. 2, it is desirable to provide a sensor in order to detect a position or a change due to these mechanisms. Then, it is desirable that the arithmetic control unit 12 performs so-called feedback control based on the output signals of those sensors. Further, the magnification change by the displacement mechanism 62 may be performed by user input. For example, the subject size or the container size is automatically detected, and the magnification is automatically set based on the detected data. Also good. Furthermore, when the container type or the like is registered in advance, the magnification may be set using the registered information. Further, in the example shown in FIG. 2, the slide mechanism 68 has the motor 68A as a drive source, but the slide force may be generated artificially.

  Next, the arithmetic control unit 12 will be described. As described above, the display unit 32, the storage device 34, the keyboard 36, the mouse 38, the printer 40, and the like are connected to the processor 30. In addition, a communication unit 42 for communicating with an external device via a network is connected.

  The processor 30 includes a CPU, an operation control program, an image processing program, a diagnostic parameter calculation program, and the like. FIG. 2 shows typical functions thereof, and the processor 30 includes an operation control unit 44 and a reconstruction calculation unit 46. The operation control unit 44 controls the overall operation of the measurement unit 10. The reconstruction calculation unit 46 constructs a CT image (tomographic image data) based on a large amount of data obtained by rotational scanning of the X-ray beam, and further calculates diagnostic parameters of the subject using the constructed tomographic image data. To do. In this case, tomographic image data corresponding to each X-ray sensor array is configured based on data obtained from each X-ray sensor array, and a plurality of tomographic image data obtained from a plurality of X-ray sensor arrays is configured. The However, in this embodiment, as will be described later in detail, only the minimum necessary tomographic image data is required to calculate the diagnostic parameters. Various known methods can be used for the reconstruction operation. Note that, in changing the magnification described above, the arithmetic expression used in the reconstruction calculation can be basically used as it is. However, when a special variable magnification method is applied, a part of the reconstruction calculation expression may be changed as necessary.

  The display 32 displays a tomographic image obtained from the tomographic image data, diagnostic parameters, and the like. In that case, it is desirable to display a numerical value or a scale representing the magnification (enlargement ratio).

  Next, generation and detection principles of the X-ray beam by the above-described X-ray CT apparatus will be described.

  FIG. 3 is a diagram for explaining the principle of rotation of the X-ray beam. In FIG. 3, reference numeral 100 denotes a rotation center axis. In the X-ray CT apparatus, the X-ray generator 52 and the X-ray detector 60 perform rotational movement with the rotation center axis 100 as the rotation center, It moves to position 52 ′ and position 60 ′ indicated by the broken lines. In this case, the effective visual field 102 is defined by an inscribed circle when the X-ray beam 101 is rotationally scanned. This effective visual field 102 corresponds to the photographing range. The X-ray beam 101 is a cone beam having a three-dimensional divergent shape as shown below.

  FIG. 4 is a diagram for explaining a cone-beam shaped X-ray beam and a multi-slice detector. As shown in FIG. 4, the X-ray generator 52 generates a three-dimensional quadrangular pyramid-shaped X-ray beam (cone beam) 56. Then, the X-ray beam 56 passes through the subject 80 and is detected by the X-ray detector 60.

  The X-ray detector 60 is composed of a plurality of X-ray sensors 60A arranged in a lattice pattern. The plurality of X-ray sensors 60A are arranged in a row in the horizontal direction in FIG. 4 to form an X-ray sensor row, and these X-ray sensor rows are arranged in an N row in the vertical direction to form a multi-slice type X-ray sensor 60A. A line detector 60 (multi-slice detector) is configured. Incidentally, the X-ray sensor array includes, for example, several tens to several hundreds (preferably 512) X-ray sensors. The number N of X-ray sensor rows is, for example, several tens to several thousand rows (preferably 64 rows). The plurality of X-ray sensors 60 </ b> A arranged in a lattice shape may be arranged in a planar shape, or may be arranged along a side surface of a cylinder having the rotation center axis 100 as an axis.

  As described above, the X-ray generator 52 and the X-ray detector 60 are connected by the displacement mechanism (reference numeral 62 in FIG. 2), and the displacement mechanism is located between the X-ray generator 52 and the X-ray detector 60. While maintaining the distance, they are rotated about the rotation center axis 100 as the rotation center. Thereby, the X-ray beam (cone beam) 56 that passes through the subject 80 is rotationally scanned.

  Further, based on the detection data obtained from each X-ray sensor row as a result of the rotational scanning, the tomographic image data of the subject 80 is formed for each X-ray sensor row in the reconstruction calculation unit (reference numeral 46 in FIG. 2). Is done. Then, the reconstruction calculation unit calculates a diagnostic parameter of the subject 80 based on the tomographic image data. At this time, in the present embodiment, the minimum necessary and sufficient to ensure the accuracy of the diagnostic parameters without forming all the tomographic image data corresponding to all the X-ray sensor rows (N sensor rows). Only the tomographic image data is constructed.

  FIG. 5 is a flowchart showing a diagnostic parameter calculation procedure by the X-ray CT apparatus of the present embodiment. Hereinafter, the processing contents will be described for each step of the flowchart of FIG.

  In S500, X-ray CT imaging of the subject is performed using all X-ray sensor arrays of the N-slice multi-slice detector. That is, the X-ray beam (cone beam) is rotationally scanned with respect to the subject, and the X-ray beam is scanned by all the X-ray sensor rows from the first X-ray sensor row to the N-th X-ray sensor row. Detection is performed (see FIG. 4).

  Incidentally, in the conventional multi-slice X-ray CT apparatus, the tomographic image data corresponding to all the X-ray sensor rows are reconstructed after the X-ray beam is detected by all the X-ray sensor rows. In the present embodiment, only tomographic image data necessary for calculation of diagnostic parameters is reconstructed in S502 to S508 described below.

In S502, it is confirmed whether or not the count value 2 ⁱ for counting the number of X-ray sensor columns exceeds the total number N of X-ray sensor columns. The initial value of i is 0 (zero), and is later incremented by 1 in S508 as necessary. Since i = 0 at the initial stage, the process proceeds from S502 to S504.

In S504, 2 ⁱ pieces of tomographic image data are reconstructed, and diagnostic parameters are calculated based on the reconstructed tomographic image data. In the initial stage, only i = 0, that is, 2 ⁱ = 1 tomographic image data is reconstructed. Here, the reconstructed tomographic image data is data corresponding to the Nth X-ray sensor array (see FIG. 4), for example. That is, the reconstruction calculation unit (reference numeral 46 in FIG. 2) reconstructs only tomographic image data corresponding to the Nth X-ray sensor column based on the data obtained from the Nth X-ray sensor column. The diagnostic parameters are calculated from the reconstructed tomographic image data. The diagnostic parameters are, for example, bone density, visceral fat mass, muscle mass, body fat percentage, and the like.

数１においてＰ_ｉは、Ｘ線センサ列の列数をカウントするためのカウント値２^ｉによって決定される枚数（２^ｉ枚）の断層画像データから得られるパラメータであり、各断層画像データから得られる診断パラメータの平均値である。つまり、例えば、Ｓ５０４において、二枚の断層画像データが形成されて各々に対応した診断パラメータが算出された場合には、二枚の断層画像データから得られる二つの診断パラメータの平均値がＰ_ｉとなる。なお、ｉ＝０つまり２^ｉ＝１枚の初期段階では、一枚の断層画像データから得られる診断パラメータをＰ_ｉとしてもよいし、一枚の断層画像データの場合にはＳ５０６において収束条件を判断せずにＳ５０８へ進むようにしてもよい。 In S506, it is confirmed whether or not the calculated diagnostic parameter satisfies the convergence condition. The convergence condition is defined by, for example, a diagnostic parameter change rate and a diagnostic parameter variation coefficient. Equation 1 shows the convergence condition defined by the rate of change of the diagnostic parameter.

In Equation 1, P _i is a parameter obtained from the number (2 ⁱ ) of tomographic image data determined by the count value 2 ⁱ for counting the number of rows of the X-ray sensor row, and is obtained from each tomographic image data. Is the average value of the diagnostic parameter That is, for example, when two tomographic image data are formed and the diagnostic parameters corresponding to each are calculated in S504, the average value of the two diagnostic parameters obtained from the two tomographic image data is _Pi. It becomes. In the i = 0, i.e. 2 ^{i =} 1 sheet early stage, to the diagnostic parameters obtained from a single tomographic image data may be P _i, in the case of a single tomographic image data convergence condition in S506 You may make it progress to S508, without judging.

In Equation 1, P _i-1 is a parameter obtained from 2 ^i-1 tomographic image data. In S504, which is repeatedly executed until the convergence condition is satisfied, the average value of the diagnostic parameters calculated last time It is. In other words, for example, when i = 2, the difference between P2 at the stage of i = ₂ and P1 at the stage of i = 1 is examined by Equation ₁ . Since the value of P _i−1 cannot be obtained at the initial stage of i = 0, for example, some initial value may be substituted as the value of P _i−1 , or at S506 at the initial stage of i = 0. The process may proceed to S508 without determining the convergence condition.

Then, K in number 1 is a constant defining the degree of convergence of the parameter P _i (accuracy). The set value of K is, for example, 0.2 (percent). As described above, in S506, it is determined whether or not the convergence is made from the comparison with the set value K by using the convergence condition of Formula 1 defined by the change rate. If it is determined in S506 that it has not converged, the process proceeds to S508.

In S508, ⁱ of the count value 2 i is incremented by one. Then, the process proceeds to S502 again, and it is confirmed whether or not the count value 2 ⁱ exceeds the total number N of X-ray sensor columns. If the total number N of X-ray sensor rows is not exceeded, the process proceeds to S504 again, 2 ⁱ tomographic image data are reconstructed, and diagnostic parameters are calculated based on the reconstructed tomographic image data. Is done.

That is, in S504, 2 ⁱ = 1, 2, 4, 8,... Tomographic image data is reconstructed step by step as i increases. As described above, when i = 0, that is, 2 ⁱ = 1, tomographic image data corresponding to the X-ray sensor array of the Nth column (see FIG. 4) is reconstructed. When i = 1, that is, 2 ⁱ = 2, in addition to the Nth X-ray sensor row, tomographic image data corresponding to the N / 2nd X-ray sensor row is reconstructed. The Further, in the case of i = 2, that is, 2 ⁱ = 4, in addition to the X-ray sensor columns of the Nth column and the N / 2th column, the N / 4th column, the third N / 4th column Tomographic image data corresponding to the X-ray sensor array is reconstructed.

As described above, in S504, the tomographic image corresponding to the (N / 2 ⁱ ) × L-th row (L = 1, 2, 4,..., 2 ⁱ ) X-ray sensor row as i increases. Data is reconstructed, and further diagnostic parameters are calculated from each tomographic image data. Then, every time the tomographic image data is reconstructed stepwise in accordance with the increase of i, the convergence condition is determined in S506.

That is, in the flowchart of FIG. 5, every time it is determined in S506 that the convergence has not occurred, i is incremented by 1 in S508, and the processing from S502 to S506 is repeatedly executed. As a result of incrementing i, if it is determined in S502 that the count value 2 ⁱ exceeds the total number N of X-ray sensor columns, the process proceeds to S510. If it is determined in S506 that the process has converged, the process proceeds to S510. In S510, the calculated diagnostic parameter value and the like are displayed as an image. The display of diagnostic parameters will be described later with reference to FIG.

数２においてＰ_ｉは、数１における定義と同じであり、Ｘ線センサ列の列数をカウントするためのカウント値２^ｉによって決定される枚数（２^ｉ枚）の各断層画像データから得られる診断パラメータの平均値である。そして、数２における変動係数ＣＶは、Ｐ_ｉに関する標準偏差ＳＤや平均値ＡＶによって定義される。また、数２におけるＭは、変動係数の算出範囲であり、例えば、Ｍ＝３に設定される。また、数２におけるＣＶＫは、変動係数の収束度合い（精度）を定義する定数であり、ＣＶＫは、例えば、０．２（パーセント）などに設定される。 In S506 of FIG. 5, the convergence condition of the following equation defined by the variation coefficient of the diagnostic parameter may be used.

In Equation 2, P _i is the same as the definition in Equation 1, and is obtained from the tomographic image data of the number (2 ⁱ ) determined by the count value 2 ⁱ for counting the number of columns of the X-ray sensor array. The average value of the diagnostic parameter. Then, variation in the number 2 coefficient CV is defined by the standard deviation SD or average value AV about _{P i.} M in Equation 2 is the calculation range of the variation coefficient, and is set to M = 3, for example. Further, CVK in Equation 2 is a constant that defines the degree of convergence (accuracy) of the variation coefficient, and CVK is set to 0.2 (percent), for example.

As described above, in S506, the convergence condition of Formula 2 defined by the variation coefficient may be used. When the convergence condition of Formula 2 is used, the calculation range for obtaining the standard deviation and the average value is set to M = 3, so that four (M + 1) parameters (P ₃ , P ₂ , P ₁ , P ₀ ) are calculated, and then convergence determination is performed.

  As described above, in the present embodiment, it is sufficient to analyze only tomographic image data that can ensure the reliability of the diagnostic parameter by determining the convergence condition in S506, so that the calculation time for image reconstruction is reduced. It can be greatly shortened. For example, assuming that it takes 1.0 second to reconstruct one tomographic image and 0.3 seconds to calculate a diagnostic parameter from one tomographic image, 1000 tomographic images are assumed. In order to reconstruct an image and obtain diagnostic parameters for 1000 sheets, it takes a calculation time of 1000 + 300 = 1300 seconds. On the other hand, in the present embodiment, for example, when the convergence condition is satisfied with 32 tomographic images, (0.3 seconds + 1.0 seconds) × 32 sheets = 41.6 seconds with sufficiently accurate diagnosis It is possible to obtain parameters.

  FIG. 6 shows a graph (A) showing a convergence process of diagnostic parameters and a display mode (B) of diagnostic parameters obtained as a result of convergence.

FIG. 6A is a graph in which the horizontal axis represents i and the vertical axis represents bone density, which is a diagnostic parameter. As described with reference to FIG. 5, in this embodiment, the average value P _i of the diagnostic parameter satisfies the convergence condition while ⁱ of the count value 2 ⁱ for counting the number of columns of the X-ray sensor row is incremented. Analysis is performed until it is satisfied. FIG. 6A shows an example in which the convergence condition is satisfied when i is incremented and i = 7. That is, the average value of the bone density obtained from 2 ⁷ = 128 pieces of tomographic image data is 1.000 mg / cm ³ and the convergence condition is satisfied.

In this case, as shown in FIG. 6B, the bone density (average value of bone density) (1.000 mg / cm ³ ) at the convergence stage, the number of tomographic image data at the convergence stage (number of slices to be analyzed) ) Value (128) is displayed on the display unit (reference numeral 32 in FIG. 2) or the like. The graph shown in FIG. 6A may be displayed on the display portion.

  Note that the display mode shown in FIG. 6 is merely an example. For example, if necessary, a tomographic image obtained from tomographic image data to be analyzed may be displayed. Further, if the processing time for image reconstruction is sufficient, 3D images of the subject may be displayed based on tomographic image data obtained from all X-ray sensor arrays.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. For example, in the above-described embodiment, an apparatus suitable for CT measurement of a small animal is shown. However, the present invention may be applied to an apparatus suitable for human CT measurement by appropriately changing the size of the apparatus. Needless to say, in an apparatus for measuring a person, it is necessary to design an apparatus that sufficiently considers the influence of the X-ray on the human body, particularly the influence of X-ray exposure.

1 is an overall configuration diagram of an X-ray CT apparatus according to the present invention. 1 is a block diagram showing an overall configuration of an X-ray CT apparatus according to the present invention. It is a figure for demonstrating the rotation principle of a X-ray beam. It is a figure for demonstrating a cone beam and a multi-slice detector. It is a flowchart which shows the calculation procedure of the diagnostic parameter by the X-ray CT apparatus which concerns on this invention. It is a figure which shows the display mode of the graph which shows a convergence process, and a diagnostic parameter.

Explanation of symbols

  10 measurement unit, 12 calculation control unit, 30 processor, 46 reconstruction calculation unit, 52 X-ray generator, 56 X-ray beam, 60 X-ray detector.

Claims (5)

An X-ray generator that generates an X-ray beam that passes through the subject;
An X-ray detection unit for detecting the X-ray beam by a plurality of X-ray sensors in a grid-like arrangement formed by a plurality of X-ray sensor arrays;
An analysis unit for analyzing the tomographic data of the subject obtained for each X-ray sensor array;
Have
The analysis unit calculates the diagnostic parameters of the subject for each stage based on the tomographic data obtained while increasing the number of sheets in stages, until the diagnostic parameters calculated in each stage satisfy a predetermined convergence condition , Repeat the calculation of diagnostic parameters across multiple stages,
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1 ,
The predetermined convergence condition is defined by a change rate of a plurality of diagnostic parameters calculated in stages.
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1 ,
The predetermined convergence condition is defined by a coefficient of variation of a plurality of diagnostic parameters calculated in stages.
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to any one of claims 1 to 3 ,
Each diagnostic parameter is a bone density of the subject.
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1 ,
Each diagnostic parameter is the fat mass of the subject,
The predetermined convergence condition is defined based on an average value regarding a plurality of fat amounts corresponding to a plurality of tomographic data.
An X-ray CT apparatus characterized by that.

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