JP2019072506A - X-ray ct apparatus - Google Patents

Abstract

To provide an X-ray CT apparatus which can perform bundle processing of signals in both a channel direction and a slice direction.SOLUTION: An X-ray CT apparatus includes an X-ray tube, an X-ray detector, a collection part, and an image generation part. The X-ray tube rotates around a body axis of a subject and generates X-ray. In the X-ray detector, a plurality of columns of detection elements detecting X-ray transmitting the subject is arranged in the channel direction and the slice direction. The collection part includes a prescribed number of detection elements and collects signals of X-ray detected by the group of detection elements where the plurality of detection elements is arranged at least in the channel direction. The image generation part generates an image by using signals collected by the collection part. The collection part sequentially reads signals at different timing among the detection elements arranged in the channel direction when reading the signals detected in the plurality of detection elements arranged in the channel direction at different timings from the X-ray detector. The image generation part generates an image by using signals sequentially read at the timing.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to an X-ray CT apparatus.

  An X-ray CT (Computed Tomography) apparatus is an apparatus that scans an object using X-rays and processes acquired data with a computer to image the inside of the object.

  Specifically, the X-ray CT apparatus irradiates the subject with X-rays a plurality of times from different directions, and detects an X-ray signal transmitted through the subject with the X-ray detector. This X-ray detector is a multi-row detector having a plurality of X-ray detection elements in the channel direction (rotational direction) and the slice direction (body axis direction). The X-ray CT apparatus collects detected signals, performs A / D conversion, and then performs preprocessing and the like to generate projection data. Then, the X-ray CT apparatus performs reconstruction processing based on the projection data to generate image data.

  Further, in the X-ray CT apparatus, in order to obtain a desired spatial resolution or a desired S / N ratio for generated image data, the signal detected by the plurality of X-ray detection elements arranged in the slice direction is bundled. Processing is being performed.

JP 2012-157742 A JP, 2012-200555, A

  The problem to be solved by the present invention is to provide an X-ray CT apparatus that enables signal bundling processing in both the channel direction and the slice direction.

  The X-ray CT apparatus according to the embodiment includes an X-ray tube, an X-ray detector, a collection unit, and an image generation unit. The x-ray tube rotates around the body axis of the subject to generate x-rays. In the X-ray detector, a plurality of detection elements for detecting X-rays transmitted through an object are arranged in the channel direction and the slice direction. The collection unit includes a predetermined number of detection elements, and collects signals of X-rays detected by a detection element group in which a plurality of detection elements are arranged at least in the channel direction. The image generation unit generates an image using the signal acquired by the acquisition unit. When reading signals detected from a plurality of detection elements aligned in the channel direction from the X-ray detector, the collection unit sequentially reads out the signals at different timings between the detection elements aligned in the channel direction. The image generation unit generates an image using the signals sequentially read at the timing.

FIG. 1 is a view showing the arrangement of an X-ray CT apparatus according to the first embodiment. FIG. 2 is a diagram for explaining an X-ray detector in the first embodiment. FIG. 3 is a diagram for explaining the positional relationship between the DAS and the detection element according to the first embodiment. FIG. 4A is a diagram for explaining the four-piece combining mode. FIG. 4B is a diagram for explaining the two-piece combining mode. FIG. 4C is a diagram for explaining the non-synthesis mode. FIG. 5 is a flowchart showing the procedure of the process of switching the combining mode according to the first embodiment. FIG. 6 is a diagram for describing a modification of the positional relationship between the DAS and the detection element according to the first embodiment. FIG. 7 is a diagram for explaining the relationship between the readout of the signal from the detection element and the irradiation period. FIG. 8 is a view showing the arrangement of an X-ray CT apparatus according to the second embodiment. FIG. 9A is a diagram for describing generation of reference data according to the second embodiment. FIG. 9B is a diagram for describing generation of reference data according to the second embodiment. FIG. 9C is a diagram for describing generation of reference data according to the second embodiment. FIG. 10 is a diagram for explaining the positional relationship between the DAS and the detection element in another embodiment.

  An X-ray CT apparatus according to an embodiment will be described below with reference to the drawings. The embodiments are not limited to the following embodiments.

First Embodiment
FIG. 1 is a view showing the arrangement of an X-ray CT apparatus 100 according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus 100 includes a gantry 110, a high voltage generator 120, a preprocessing device 130, a reconstruction device 140, an image processing device 150, a storage device 160, and an input device. A display 170 and a system controller 190 are provided.

  The gantry 110 irradiates X-rays to the subject, detects X-rays transmitted through the subject, and generates raw data. The gantry 110 includes an X-ray tube 111, a slip ring 112, an X-ray detector 115, a frame 113, a rotating unit 114, a data acquisition circuit 116, and a noncontact data transmission device 117.

  The X-ray tube 111 generates X-rays for irradiating the subject with the tube voltage and tube current supplied from the high voltage generator 120 via the slip ring 112. The X-ray detector 115 detects X-rays generated from the X-ray tube 111 and transmitted through the subject. The X-ray detector 115 will be described in detail later.

  The frame 113 is formed in an annular shape and is provided rotatably around the rotation axis RA. The frame 113 supports the X-ray tube 111 and the X-ray detector 115 so as to face each other across the rotation axis RA. The rotating unit 114 rotates the frame 113 around the rotation axis RA. For example, the rotating unit 114 rotates the frame 113 at a high speed at a speed of 0.4 seconds / rotation. Thereby, the rotation unit 114 rotates the X-ray tube 111 and the X-ray detector 115 around the body axis of the subject.

  The X-ray detector 115 is a multi-row detector ("multi-slice type") having a plurality of X-ray detection elements (hereinafter simply referred to as "detection elements") in the channel direction (row direction) and slice direction (column direction). Also referred to as "detector", "multi-detector row detector". The channel direction corresponds to the rotation direction of the frame 113, and the slice direction corresponds to the body axis direction of the subject.

  FIG. 2 is a diagram for explaining the X-ray detector 115 in the first embodiment. FIG. 2A is a top view showing the configuration of the X-ray detector 115. As shown in (A), the X-ray detector 115 has, for example, a plurality of detection elements arranged in the channel direction (row direction) and the slice direction (column direction). In addition, (B) of FIG. 2 is a perspective view.

  For example, in the X-ray detector 115, each detection element detects X-rays transmitted through the subject. Then, charge is accumulated in each detection element according to the detected X-ray dose. The charge accumulated in each detection element is appropriately read by a data acquisition circuit 116 described later. In other words, the charge accumulated in each detection element is sent to the data acquisition circuit 116 as an X-ray signal (X-ray transmission signal) transmitted through the subject. In the first embodiment, the case where a plurality of X-ray detection elements having a width of 0.5 mm are arranged in the channel direction and the slice direction will be described. However, the present invention is not limited to this. Line detection elements may be arranged.

  The data acquisition circuit 116 has a plurality of DAS (Data Acquisition System). Each DAS reads (collects) an X-ray signal (X-ray transmission signal) detected by the X-ray detector 115, amplifies it, and converts it into digital signal data (raw data). The noncontact data transmission device 117 transmits the raw data output from each DAS to the preprocessing device 130.

  Here, the DAS according to the first embodiment takes charge of a plurality of detection elements in the channel direction and the slice direction. That is, the relationship between the DAS and the detection element is not one to one, and one DAS processes a signal detected by a group of detection elements. Here, the detection element group is, for example, a set of a plurality of detection elements in which a plurality of detection elements are arranged in each of the channel direction and the slice direction. The DAS is an example of a collection unit.

  FIG. 3 is a diagram for explaining the positional relationship between the DAS and the detection element according to the first embodiment. FIG. 3 illustrates a part of the detection element disposed in the X-ray detector 115 illustrated in FIG. In the example shown in FIG. 3, four detection elements 11, 12, 13, 14, 21, 22, 23, 23, 24, 32, 33, 33, 34, 41, 42, 43 are used. DASs 116A, 116B, 116C and 116D are arranged. Although FIG. 3 illustrates the case where four detection elements are allocated to one DAS as a detection element group, the present invention is not limited to this. For example, the number of detection elements included in the detection element group may be arbitrarily changed. Also, one DAS may be in charge of processing a signal detected by a plurality of detection element groups.

  In FIG. 3, the DAS 116A is in charge of processing the signals detected by the detection elements 11, 12, 21, and 22. Here, the detection elements 11 and 12 exist at different positions in the channel direction. The detection elements 21 and 22 are present at different positions in the channel direction. The detection elements 11 and 21 are present at different positions in the slice direction. The detection elements 12 and 22 are present at different positions in the slice direction. The conducting wire 51 connects the detection elements 11 and 21 arranged in the same channel. Moreover, the conducting wire 52 connects the detection elements 12 and 22 arranged in the same channel. Further, the conducting wire 53 connects the conducting wire 51 and the conducting wire 52. Also, the conductors 51, 52, 53 are connected to the DAS 116A. In the example shown in FIG. 3, the lead 52 is connected to the DAS 116A. A switch for individually switching connection / non-connection between each detection element and the DAS is disposed between each detection element 11, 12, 21, 22 and the DAS 116A. By individually controlling the switches, charges accumulated in the respective detection elements are sequentially read out to the DAS 116A. Moreover, although the case where the conducting wires 51, 52, and 53 were respectively connected was demonstrated on the facilities of description, it is not limited to this. For example, the conducting wires 51, 52, 53 may be configured by a single conducting wire.

  Also, the DAS 116B is in charge of processing the signals detected by the detection elements 31, 32, 41, 42. In this case, the positional relationship between the DAS 116B, the detection elements 31, 32, 41 and 42, and the conducting wires 57, 58 and 59 is the same as the positional relationship between the DAS 116A, the detecting elements 11, 12, 21 and 22 and the conducting wires 51, 52 and 53. is there.

  Further, the DAS 116C is in charge of processing the signals detected by the detection elements 13, 14, 23, 24. In this case, the positional relationship between the DAS 116C, the detection elements 13, 14, 23, 24 and the conducting wires 54, 55, 56 is the same as the positional relationship between the DAS 116A, the detecting elements 11, 12, 21, 22 and the conducting wires 51, 52, 53 is there.

  In addition, the DAS 116D is in charge of processing the signals detected by the detection elements 33, 34, 43 and 44. In this case, the positional relationship between the DAS 116D, the detection elements 33, 34, 43, 44 and the conducting wires 60, 61, 62 is the same as the positional relationship between the DAS 116A, the detecting elements 11, 12, 21, 22 and the conducting wires 51, 52, 53 is there.

  Thus, each DAS 116A-116D takes charge of processing of the signal detected by each detection element 11-44. Each of the DASs 116A to 116D can execute processing in parallel.

  The data acquisition circuit 116 further includes a bundling control unit 200. The processing in the bundling control unit 200 will be described later.

  It returns to the explanation of FIG. The high voltage generator 120 is a device that supplies tube voltage and tube current to the X-ray tube 111 of the gantry 110 to generate X-rays. The preprocessing device 130 performs correction processing such as sensitivity correction on the raw data transmitted from the non-contact data transmission device 117 to generate projection data as a basis of image reconstruction.

  The reconstruction device 140 reconstructs the image data of the object by performing predetermined reconstruction processing on the projection data generated by the preprocessing device 130. The image processing apparatus 150 generates a three-dimensional image, a curved surface multiplanar reconstruction (MPR) image, a cross-cut image, and the like using the image data reconstructed by the reconstruction apparatus 140.

  The storage device 160 stores projection data generated by the preprocessing device 130, image data reconstructed by the reconstruction device 140, various images generated by the image processing device 150, and the like. For example, the storage device 160 is an HDD (Hard Disk Drive) or a DVD (Digital Versatile Disc) drive.

  The input device 170 receives various operations on the X-ray CT apparatus 100 from the operator. For example, the input device 170 is a keyboard or a mouse. The display device 180 outputs various images generated by the reconstruction device 140 or the image processing device 150, a GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, the display device 180 is a liquid crystal panel or a CRT (Cathode Ray Tube) monitor.

  The system controller 190 controls the overall operation of the X-ray CT apparatus 100 based on various operations accepted by the input device 170.

  Further, the system controller 190 bundles the X-ray transmission signals detected by the respective detection elements in a predetermined unit by controlling the below-mentioned bundling control unit 200 based on the scan conditions. Such processing is referred to as "signal bundling processing" and will be described in detail later.

  With such a configuration, the X-ray CT apparatus 100 according to the first embodiment enables signal bundling processing in both the channel direction and the slice direction by performing the following processing. Below, in order to realize this function, processing performed in the bundling control unit 200 of the X-ray CT apparatus 100 will be described.

  The bundling control unit 200 performs signal bundling processing under the control of the system controller 190. Here, the signal bundling process is to combine analog signals detected by each of the plurality of detection elements in at least one of the channel direction and the slice direction in a predetermined unit. By changing this combination unit (combination mode), the resolution of the X-ray transmission signal passed to the DAS can be adjusted. For example, in the example illustrated in FIG. 3, in the combination mode in which the bundling control unit 200 can change, when four detection elements are combined as one unit (four combination mode), two detection elements are as one unit. There are three patterns in the case of combining (two combining mode) and in the case of not combining (non combining mode).

  A combination mode that can be changed by signal bundling processing will be described using FIGS. 4A to 4C. 4A to 4C show four detection elements 11, 12, 21 and 22 assigned to the DAS 116A of FIG. FIG. 4A is a diagram for explaining the four-piece combining mode. FIG. 4B is a diagram for explaining the two-piece combining mode. FIG. 4C is a diagram for explaining the non-synthesis mode. In the example shown in FIGS. 4A to 4C, the detection elements 11, 12, 21 and 22 are arranged at intervals of 0.5 mm.

(4 combination mode)
The four-piece combining mode will be described with reference to FIG. 4A. In this case, the bundling control unit 200 detects each of the detection elements 11, 12, 21 and 22 by individually controlling, for example, the DAS 116A and the switches of the four detection elements 11, 12, 21 and 22. The synthesized signal (charge) is synthesized.

  Specifically, the bundling control unit 200 first turns on the connection between the DAS 116A and the detection element 11. Thereby, the charge accumulated in the detection element 11 moves to the capacitor in the DAS 116A. Next, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 21. Thereby, the charge accumulated in the detection element 21 is transferred to the capacitor in the DAS 116A and added to the accumulated charge. Subsequently, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 12. Thereby, the charge accumulated in the detection element 12 is transferred to the capacitor in the DAS 116A, and is further added to the accumulated charge. Then, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 22. Thereby, the charge stored in the detection element 22 is transferred to the capacitor in the DAS 116A, and is further added to the stored charge. That is, the charges accumulated in each of the four detection elements 11, 12, 21 and 22 are added (combined) in the DAS 116A.

  Thereafter, the bundling control unit 200 causes the DAS 116A to execute signal processing. That is, the DAS 116A converts the synthesized signal into digital signal data (raw data). Then, the bundling control unit 200 resets the charge accumulated in the capacitor in the DAS 116A.

  Thus, the bundling control unit 200 combines the signals detected by the four detection elements 11, 12, 21, and 22. Then, the bundling control unit 200 converts the synthesized signal into raw data, and outputs the raw data. Note that, in the combination mode of four detection elements having a width of 0.5 mm, image data having a spatial resolution equal to that of the detection elements having a width of 1 mm is reconstructed.

(2-piece composition mode)
The two combination mode will be described with reference to FIG. 4B. In this case, the bundling control unit 200 synthesizes a signal for each set of two detection elements by individually controlling, for example, the DAS 116A and the switches of the four detection elements 11, 12, 21 and 22. . Here, as shown by the broken line in FIG. 4B, a case will be described in which signals are respectively synthesized by the pair of detection elements 11 and 21 and the pair of detection elements 12 and 22.

  Specifically, the bundling control unit 200 first turns on the connection between the DAS 116A and the detection element 11. Thereby, the charge accumulated in the detection element 11 moves to the capacitor in the DAS 116A. Next, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 21. Thereby, the charge accumulated in the detection element 21 is transferred to the capacitor in the DAS 116A and added to the accumulated charge. Then, the bundling control unit 200 causes the DAS 116A to execute signal processing. That is, the DAS 116A combines the signals detected by the two detection elements 11 and 21 and converts the combined signal into raw data. Then, the bundling control unit 200 resets the charge accumulated in the capacitor in the DAS 116A.

  Subsequently, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 12. Thereby, the charge accumulated in the detection element 12 is transferred to the capacitor in the DAS 116A. Then, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 22. Thereby, the charge stored in the detection element 22 is transferred to the capacitor in the DAS 116A and added to the stored charge. Then, the bundling control unit 200 causes the DAS 116A to execute signal processing. That is, the DAS 116A combines the signals detected by the two detection elements 12 and 22 and converts the combined signal into raw data. Then, the bundling control unit 200 resets the charge accumulated in the capacitor in the DAS 116A.

  As described above, the bundling control unit 200 combines the raw data from the two detection elements 11 and 21 and the two detection elements 12 and 22 by synthesizing a signal for each set of two detection elements. Raw data from which data is derived are sequentially output. Note that, in the combination mode of two detection elements of 0.5 mm width, image data having twice the spatial resolution in the channel direction is reconstructed as compared with the detection element of 1 mm width.

  In the example of FIG. 4B, although the case where the signal is combined with the pair of detection elements 11 and 21 and the pair of detection elements 12 and 22 has been described, the embodiment is not limited to this. For example, by appropriately changing the order of the detection elements that turn on the connection (switch) with the DAS 116A, it is possible to combine signals of arbitrary detection elements with each other.

(Non composition mode)
The non-synthesis mode will be described with reference to FIG. 4C. In this case, for example, the bundling control unit 200 individually controls the switches of the DAS 116A and the four detection elements 11, 12, 21 and 22 to output the signals of the detection elements without combining them.

  Specifically, the bundling control unit 200 first turns on the connection between the DAS 116A and the detection element 11. Thereby, the charge accumulated in the detection element 11 moves to the capacitor in the DAS 116A. Then, the bundling control unit 200 causes the DAS 116A to execute signal processing. That is, the DAS 116A converts the signal detected by the detection element 11 into raw data. Then, the bundling control unit 200 resets the charge accumulated in the capacitor in the DAS 116A.

  Subsequently, the bundling control unit 200 turns on the connection between the DAS 116A and the detection element 21. Thereby, the charge accumulated in the detection element 21 moves to the capacitor in the DAS 116A. Then, the bundling control unit 200 causes the DAS 116A to execute signal processing. That is, the DAS 116A converts the signal detected by the detection element 21 into raw data. Then, the bundling control unit 200 resets the charge accumulated in the capacitor in the DAS 116A.

  Hereinafter, similarly, the bundling control unit 200 sequentially turns on the connection between the DAS 116A and the detection elements 21 and 22. Then, the bundling control unit 200 performs signal processing on the charges accumulated therein.

  As described above, the bundling control unit 200 does not combine the signals of the respective detection elements 11, 21, 12, 22, but raw data derived from the signal of the detection element 11 and raw data derived from the signal of the detection element 21. The raw data derived from the signal of the detection element 12 and the raw data derived from the signal of the detection element 22 are sequentially output. It should be noted that in the non-combination mode of the detection element of 0.5 mm width, the image data of which spatial resolution is 4 times (2 times in the channel direction and 2 times in the slice direction) compared to the detection element of 1 mm width Configured

  In the example of FIG. 4C, the raw data is sequentially output by turning on the switches in the order of the detection elements 11, 21, 12, 22. However, the embodiment is not limited to this. . For example, raw data can be output in an arbitrary order by appropriately changing the order of detection elements that turn on the connection (switch) with the DAS 116A.

  As described above, the bundling control unit 200 performs signal bundling processing to change the number of effective detection elements in the channel direction and the slice direction. The signal bundling process has an effect of averaging noise levels of the respective detection elements. That is, by combining signals from a plurality of detection elements, raw data equivalent to the increase in size of the detection elements can be obtained. This reduces the spatial resolution but is more robust to noise.

  That is, the bundling control unit 200 performs imaging by switching the above combination mode in order to obtain a desired spatial resolution or to obtain a desired SN ratio. As a result, the bundling control unit 200 can cope with both the case of shooting with high spatial resolution and the case of shooting with high SN ratio.

  FIG. 5 is a flowchart showing the procedure of the process of switching the combining mode according to the first embodiment. As shown in FIG. 5, the bundling control unit 200 receives the selection of the combining mode (step S101). For example, the bundling control unit 200 causes a selectable combining mode to be displayed on a graphical user interface (GUI), and receives selection of the combining mode from the operator. As a specific example, the bundling control unit 200 receives selection of any one of the four-piece combining mode, the two-piece combining mode, and the non-composition mode. The bundling control unit 200 is in a standby state until the selection of the combination mode is received (No at step S101).

  When the selection of the combination mode is received (Yes at step S101), the bundling control unit 200 determines whether four selected combination modes are the combination mode (step S102). Here, if the four-piece combining mode is set (Yes at step S102), the bundling control unit 200 causes the four-piece combining mode to execute imaging (step S103).

  On the other hand, when the four-piece combining mode is not set (No at step S102), the bundling control unit 200 determines whether the selected combining mode is the two-piece combining mode (step S104). Here, if the two-piece combining mode is set (Yes at Step S104), the bundling control unit 200 causes the two-piece combining mode to execute imaging (Step S105).

  On the other hand, if the two-piece combining mode is not set (No at Step S104), the bundling control unit 200 causes the imaging in the non-combination mode to be performed (Step S106).

  Note that the processing procedure of the switching process of the combination mode is not limited to the above example. For example, the bundling control unit 200 acquires from the system controller 190 the imaging condition group (protocol) set in advance at the imaging planning stage. Then, in the imaging condition group, an appropriate combining mode is incorporated in advance according to the imaging conditions, and the bundling control unit 200 may switch the combining mode by referring to the combining mode.

  As described above, in the X-ray CT apparatus 100 according to the first embodiment, the X-ray tube 111 rotates around the body axis of the subject to generate X-rays. Further, in the X-ray CT apparatus 100, in the X-ray detector 115, a plurality of detection elements for detecting X-rays transmitted through the subject are arrayed in the body axial direction of the subject and the rotational direction in which the X-ray tube 111 rotates. Ru. The DAS collects X-ray signals detected by a detector group including a predetermined number of detector elements. In the detection element group, a plurality of detection elements are arranged at least in the rotation direction. Thus, the X-ray CT apparatus 100 according to the first embodiment enables signal bundling processing in both the channel direction and the slice direction.

  Also, for example, the X-ray CT apparatus 100 according to the first embodiment performs imaging by switching a predetermined combination mode in order to obtain a desired spatial resolution or to obtain a desired SN ratio. As a result, the X-ray CT apparatus 100 can cope with both the case of imaging with high spatial resolution and the case of imaging with high SN ratio.

(Modification of the first embodiment)
The positional relationship between the DAS and the detection element described in FIG. 3 is merely an example. For example, this positional relationship may be modified as shown in FIG. FIG. 6 is a diagram for describing a modification of the positional relationship between the DAS and the detection element according to the first embodiment. The arrangement of each detection element and DAS shown in FIG. 6 is the same as the arrangement shown in FIG. 3, but the arrangement of the leads connected to each detection element is different.

  In FIG. 6, the DAS 116A is in charge of processing the signals detected by the detection elements 11, 12, 21, and 22. Here, the detection elements 11 and 12 exist at different positions in the channel direction. The detection elements 21 and 22 are present at different positions in the channel direction. The detection elements 11 and 21 are present at different positions in the slice direction. The detection elements 12 and 22 are present at different positions in the slice direction. The conducting wire 71 connects the detection elements 11 and 12 arranged in the same slice. Moreover, the conducting wire 72 connects the detection elements 21 and 22 arranged in the same slice. Moreover, the conducting wire 73 connects the conducting wire 71 and the conducting wire 72. Moreover, the conductors 71, 72, 73 are connected to the DAS 116A. In the example shown in FIG. 6, the lead 73 is connected to the DAS 116A. A switch for individually switching connection / non-connection between each detection element and the DAS is disposed between each detection element 11, 12, 21, 22 and the DAS 116A. Moreover, although the case where the conducting wire 71, 72, 73 is respectively connected was demonstrated on the facilities of description, it is not limited to this. For example, the conductors 71, 72, 73 may be configured by one conductor.

  Also, the DAS 116B is in charge of processing the signals detected by the detection elements 31, 32, 41, 42. In this case, the positional relationship between the DAS 116B, the detection elements 31, 32, 41, 42, and the conducting wires 77, 78, 79 is the same as the positional relationship between the DAS 116A, the detecting elements 11, 12, 21, 22 and the conducting wires 71, 72, 73. is there.

  Further, the DAS 116C is in charge of processing the signals detected by the detection elements 13, 14, 23, 24. In this case, the positional relationship between the DAS 116C, the detecting elements 13, 14, 23, 24 and the conducting wires 74, 75, 76 is the same as the positional relationship between the DAS 116A, the detecting elements 11, 12, 21, 22 and the conducting wires 71, 72, 73. is there.

  In addition, the DAS 116D is in charge of processing the signals detected by the detection elements 33, 34, 43 and 44. In this case, the positional relationship between the DAS 116D, the detection elements 33, 34, 43 and 44, and the conducting wires 80, 81 and 82 is the same as the positional relationship between the DAS 116A, the detecting elements 11, 12, 21 and 22 and the conducting wires 71, 72 and 73. is there.

  Thus, each DAS 116A-116D reads data from each detection element 11-44. Each of the DASs 116A to 116D can execute read processing in parallel.

Second Embodiment
In the first embodiment, the case where one DAS is in charge of processing signals detected by a plurality of detection elements in the channel direction and slice direction has been described. Here, when one DAS reads signals from a plurality of detection elements, strictly speaking, the X-ray emission time (period) differs among these detection elements.

  FIG. 7 is a diagram for explaining the relationship between the readout of the signal from the detection element and the irradiation period. In FIG. 7, the lateral direction corresponds to time. Also, the downward arrow indicates the timing of reading out the signal (charge). In addition, although detection element 11,21,12,22 is demonstrated as an example in FIG. 7, the same may be said of the other detection element contained in the X-ray detector 115. FIG.

  As shown in FIG. 7, when reading out the signals from the detection elements 11, 21, 12, 22, the DAS 116A reads out the signals (charges) at different times T1 to T8. Here, for example, the signal read at time T5 corresponds to the signal emitted from time T1 to time T5. Also, the signal read out at time T6 corresponds to the one emitted from time T2 to time T6. Further, the signal read out at time T7 corresponds to the one emitted from time T3 to time T7. Also, the signal read out at time T8 corresponds to the one emitted from time T4 to time T8.

  Thus, the signals read out by the DAS 116A may correspond exactly to those exposed for different time periods. For this reason, it is preferable to correct the raw data output from each detection element using the X-ray dose when X-rays are irradiated to each detection element. Therefore, in the second embodiment, the X-ray CT apparatus 100 corrects the raw data output from each detection element using the X-ray dose when the X-ray is irradiated to each detection element that the DAS takes charge of. Explain the case of

  FIG. 8 is a view showing the arrangement of an X-ray CT apparatus 100 according to the second embodiment. The X-ray CT apparatus 100 according to the second embodiment has a configuration similar to that of the X-ray CT apparatus 100 shown in FIG. 1, and a Ref (Reference) detector 210 is installed near the X-ray tube 111. And part of the processing in the data acquisition circuit 116 and the preprocessing unit 130 are different. In the second embodiment, therefore, differences from the first embodiment will be mainly described, and descriptions of points having the same functions as the configurations described in the first embodiment will be omitted.

  The Ref detector 210 according to the second embodiment has a detection element. The detection element of the Ref detector 210 detects an X-ray signal (X-ray non-transmissive signal) which does not pass through the subject. Then, the detection element of the Ref detector 210 sequentially outputs the detected X-ray non-transmissive signal to the data acquisition circuit 116. In addition, as for this detection element, it is desirable to be comprised with the same raw material as the detection elements 11-44.

  The data acquisition circuit 116 according to the second embodiment has the same function as the function described in the first embodiment. Furthermore, the data acquisition circuit 116 has a DAS (DAS for Ref) for processing the X-ray non-transmissive signal detected by the Ref detector 210.

  The Ref DAS generates data (reference data) corresponding to the irradiation time of each detection element in the X-ray detector 115 based on the X-ray non-transmissive signal detected by the Ref detector 210.

  9A to 9C are diagrams for describing generation of reference data according to the second embodiment. In FIGS. 9A-9C, the lateral direction corresponds to time. In the example shown in FIG. 9A, the reference data generated in the non-combination mode is described, in the example shown in FIG. 9B, the reference data generated in the two-piece combination mode is described. In the example shown in FIG. Reference data generated in the synthesis mode will be described.

  As shown in FIG. 9A, in the non-combination mode, the Ref DAS generates reference data 1, 2, 3, 4 for each raw data output from each detection element 11, 12, 21, 22. .

  Specifically, the Ref DAS has a capacitor, and accumulates the X-ray non-transmissive signal (charge) output from the Ref detector 210. Then, the Ref DAS reads out the signal stored in the capacitor at the timing when the detection elements 11, 12, 21 and 22 are read out. In the example of FIG. 9A, the Ref DAS reads signals at timings of T1, T2,. The signals read out here correspond to the charges accumulated by the non-transmissive X-ray in each period of T1 to T2, T2 to T3,..., T7 to T8. Then, the Ref DAS amplifies the signal read out in each period, and further converts it into digital signal data (period data). This period data corresponds to the moving average of the signal of each period.

  Then, as shown in FIG. 9A, the Ref DAS generates reference data corresponding to the period in which each of the detection elements 11, 12, 21, 22 is exposed. Specifically, the DAS for Ref generates reference data for each detection element by adding data for each period. For example, for the detection element 11, the Ref DAS generates reference data 1 by adding data during a period corresponding to the read timing interval (T1 to T5) of the detection element 11. Further, the Ref DAS generates reference data 2 by adding data of a period corresponding to the interval (T2 to T6) of the read timing of the detection element 21 for the detection element 21. Further, the Ref DAS generates reference data 3 by adding data of a period corresponding to the read timing interval (T3 to T7) of the detection element 12 with respect to the detection element 12. Further, the Ref DAS generates reference data 4 by adding data for a period corresponding to the read timing interval (T4 to T8) of the detection element 22 for the detection element 22.

  Then, the data acquisition circuit 116 appends reference data corresponding to each raw data to the raw data derived from each detection element 11, 12, 21, 22. For example, the data acquisition circuit 116 appends the reference data 1 to the raw data derived from the detection element 11. Further, the data acquisition circuit 116 appends the reference data 2 to the raw data derived from the detection element 21. Further, the data acquisition circuit 116 appends the reference data 3 to the raw data derived from the detection element 12. Further, the data acquisition circuit 116 appends the reference data 4 to the raw data derived from the detection element 22.

  As shown in FIG. 9B, in the two-piece combining mode, the Ref DAS is a reference for each pair of detection elements 11, 12, 21 and 22 used in the two-piece combining mode under the control of the bundling control unit 200. Generate data. For example, the Ref DAS generates reference data corresponding to the irradiation time of any of the detection elements included in each set.

  For example, the Ref DAS generates reference data 5 corresponding to the irradiation time (T1 to T5) of the detection element 11 in order to correct the raw data derived from the set of the detection elements 11 and 21. The process of generating the reference data 5 is the same as the process of generating the reference data 1 of FIG. 9A, and thus the description thereof is omitted.

  Also, for example, the Ref DAS generates reference data 6 corresponding to the irradiation time (T3 to T7) of the detection element 12 in order to correct the raw data derived from the set of the detection elements 12 and 22. The process of generating the reference data 6 is the same as the process of generating the reference data 3 of FIG. 9A, and thus the description thereof is omitted.

  Then, the data acquisition circuit 116 appends the reference data 5 to the raw data derived from the two detection elements 11 and 21. Further, the data acquisition circuit 116 appends the reference data 6 to the raw data derived from the two detection elements 12 and 22. In addition, in FIG. 9B, in order to correct the raw data derived from the set of detection elements 11 and 21, reference data 5 corresponding to the irradiation time (T1 to T5) of the detection element 11 is generated. It is not limited to this. For example, reference data (corresponding to the reference data 2 in FIG. 9A) corresponding to the irradiation time (T2 to T6) of the detection element 21 may be generated. That is, in the case of generating reference data in the two-piece combination mode, reference data corresponding to the irradiation time of any of the detection elements included in each set may be generated.

  As shown in FIG. 9C, in the four-piece combining mode, one of the detection elements 11, 12, 21, and 22 used in the four-piece combining mode is controlled by the bundling control unit 200 for the Ref DAS. Reference data corresponding to the irradiation time of the detection element is generated.

  For example, the Ref DAS generates reference data 7 corresponding to the irradiation time (T2 to T6) of the detection element 21. The process of generating the reference data 7 is the same as the process of generating the reference data 2 of FIG. 9A, and thus the description thereof is omitted.

  Then, the data acquisition circuit 116 appends the reference data 7 to the raw data derived from the four detection elements 11, 12, 21, 22. In addition, in FIG. 9C, in order to correct the raw data derived from the four detection elements 11, 12, 21, and 22, the reference data 7 corresponding to the irradiation time (T2 to T6) of the detection element 21 is generated. However, the embodiment is not limited to this. For example, reference data (corresponding to reference data 3 in FIG. 9A) corresponding to the irradiation time (T3 to T7) of the detection element 12 may be generated. That is, even in the case of generating reference data in the four-piece combining mode, reference data corresponding to the irradiation time of any one of the detecting elements to be combined may be generated. However, in order to prevent the difference between the irradiation time for which the reference data is intended and the irradiation time for each detection element becoming large, among the detection elements to be synthesized, the detection time of which the irradiation time is near the center Preferably, corresponding reference data is generated. Alternatively, as in FIG. 9A, four reference data corresponding to each detection element may be generated, and an appropriate one may be appropriately selected from these reference data.

  The preprocessing device 130 according to the second embodiment performs a correction process of correcting each raw data, using the reference data attached to each raw data. For example, the output ratio (= raw data / reference data) is determined. This output ratio represents the attenuation of x-rays by the subject.

  For example, in the non-synthesis mode, the data acquisition circuit 116 divides the raw data derived from the detection element 11 by the reference data 1. Further, the data acquisition circuit 116 divides the raw data derived from the detection element 21 by the reference data 2. In addition, the data acquisition circuit 116 divides the raw data derived from the detection element 12 by the reference data 3. Also, the data acquisition circuit 116 divides the raw data derived from the detection element 22 by the reference data 4.

  Further, for example, in the two-piece combining mode, the data acquisition circuit 116 divides the raw data derived from the detection elements 11 and 21 by the reference data 5. Further, the data acquisition circuit 116 divides the raw data derived from the detection elements 12 and 22 by the reference data 6.

  Further, for example, in the four-piece combining mode, the data acquisition circuit 116 divides the raw data derived from the detection elements 11, 12, 21, 22 by the reference data 7.

  As described above, the X-ray CT apparatus 100 according to the second embodiment uses the X-ray dose when X-rays are irradiated to each detection element that the DAS takes charge of, and outputs from each detection element in each synthesis mode It is possible to correct the raw data being

(Other embodiments)
In the first and second embodiments described above, the case where four detection elements are allocated to one DAS has been described, but the present invention is not limited to this. For example, the number of detection elements assigned to one DAS may be eight or two. When the number of detection elements allocated to one DAS is two, at least signal bundling processing in the channel direction can be performed by arranging the two detection elements in the channel direction. That is, in the detection element group allocated to one DAS, a plurality of detection elements may be disposed at least in the channel direction.

  FIG. 10 is a diagram for explaining the positional relationship between the DAS and the detection element in another embodiment. FIG. 10 shows an example in which eight or more detection element groups are assigned to one DAS. That is, in FIG. 10, all of the detection element groups G1-1, G2-1, G3-1, G4-1, G1-2, and G2-2 are the four detection elements described in the above-described embodiment. And a set of a plurality of detection elements in which two detection elements are arranged in each of the channel direction and the slice direction.

  In the example of FIG. 10, for example, the detection element group G1-1 and the detection element group G1-2 are assigned to one DAS "DAS1". Further, as shown in FIG. 10, the detection element group G1-1 and the detection element group G1-2 are not arranged adjacent to each other, and between them, “DAS2” different from “DAS1”, “DAS3” (shown in FIG. Are omitted), and a detection element group assigned to “DAS 4” (not shown) is arranged.

  In the case of the positional relationship of FIG. 10, for example, “DAS1” first reads the charge from the detection element group G1-1 and then reads the charge from the detection element group G1-2. On the other hand, the read timing from the detection element group G1-1 by "DAS1", the read timing from the detection element group G2-1 by "DAS2", the read timing from the detection element group G3-1 by "DAS3", The read timing from the detection element group G4-1 by “DAS4” substantially matches. In this way, by allocating the assignment of detection element groups having close physical positional relationships to different DASs, it becomes possible to make the read timings from the detection element groups having close physical positional relationships substantially coincide. As a result, it is possible to contribute to the improvement of the image quality.

  Note that although generation of reference data has been described in the second embodiment, this point will be supplementarily described using FIG. For example, as described in the non-synthesis mode in the second embodiment, it is assumed that reference data is individually generated to correspond to each X-ray emission time of each detection element. In the case of the example, four reference data are generated for the detection element group G1-1, and the same reference data is also applied to the detection element group G2-1, the detection element group G3-1, and the detection element group G4-1. It will be done. Further, although four reference data are generated also for the detection element group G1-2 and the detection element group G2-2, this is generated for the detection element group G1-1 and the detection element group G2-1. Different from the reference data.

  On the other hand, for example, as described in the four-piece combining mode in the second embodiment, assuming that one representative reference data corresponding to any of the detection elements is applied, as shown in FIG. In the case of the example, one reference data is generated for the detection element group G1-1, and the same reference data is also generated for the detection element group G2-1, the detection element group G3-1, and the detection element group G4-1. Applied. In addition, although one reference data is generated for the detection element group G1-2 and the detection element group G2-2, this is generated for the detection element group G1-1 and the detection element group G2-1. It is different from the reference data to be

  According to at least one embodiment described above, signal bundling processing in both channel direction and slice direction is enabled.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

100 X-ray CT apparatus 111 X-ray tube 115 X-ray detector 116 data acquisition circuit 116A to 116D DAS
140 Reconfigurable Equipment

Claims (11)

An x-ray tube that rotates around the body axis of the subject and generates x-rays;
An X-ray detector in which a plurality of detection elements for detecting X-rays transmitted through the subject are arranged in the channel direction and the slice direction;
An acquisition unit configured to acquire an X-ray signal detected by a detection element group including a predetermined number of the detection elements and arranged with at least a plurality of detection elements in the channel direction;
An image generation unit that generates an image using the signal acquired by the acquisition unit;
Equipped with
The collection unit sequentially reads the signals at different timings between the detection elements arranged in the channel direction when reading out the signals detected from the plurality of detection elements arranged in the channel direction from the X-ray detector.
The X-ray CT apparatus, wherein the image generation unit generates the image using signals sequentially read at the timing. The image generation unit further includes a correction signal collection unit that collects a correction signal used for correction when an image is generated.
The correction signal collection unit individually collects correction signals according to the readout timing of the signal,
The image generation unit applies the correction signals respectively corresponding to the signals sequentially read at the timing to generate the image.
The X-ray CT apparatus according to claim 1. The correction signal collection unit individually collects correction signals according to readout timings of the signals by moving average of X-ray signals detected without passing through the subject.
The X-ray CT apparatus according to claim 2. The correction signal collection unit reads out one of the signals to be synthesized when the signals detected by the plurality of detection elements included in the detection element group are synthesized in a predetermined unit. Collect correction signal according to the timing,
The X-ray CT apparatus according to claim 2 or 3. The correction signal collection unit is configured to be located near the center of the readout timing of each signal to be synthesized when the signals detected by each of the plurality of detection elements included in the detection element group are synthesized in a predetermined unit. Collecting a correction signal according to the read timing,
The X-ray CT apparatus according to claim 2 or 3. The image generation unit includes a first mode in which signals detected from a plurality of detection elements aligned in the channel direction among the detection element group are combined and output from the collection unit, and a plurality of lines aligned in the channel direction The image is generated in response to switching to a second mode in which each of the signals detected from the detection element is individually output from the collection unit.
The X-ray CT apparatus according to any one of claims 1 to 4. The detection element group further includes a plurality of detection elements arranged in the slice direction.
The X-ray CT apparatus according to any one of claims 1 to 6. A first conducting wire connecting a plurality of detection elements arranged in the slice direction;
And a second wire connecting the plurality of first wires aligned in the channel direction.
The X-ray CT apparatus according to claim 7. The collection unit synthesizes signals detected by each of a plurality of detection elements arranged in the slice direction.
The X-ray CT apparatus according to claim 8. A first conducting wire connecting a plurality of detecting elements arranged in the channel direction;
And a second conductor connecting the plurality of first conductors arranged in the slice direction.
The X-ray CT apparatus according to claim 7. The collection unit combines signals detected by each of a plurality of detection elements arranged in the channel direction.
The X-ray CT apparatus according to claim 10.

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