JP2020199086A - X-ray CT system - Google Patents

Abstract

To improve spatial resolution.SOLUTION: An X-ray CT system in an embodiment includes an X-ray irradiation unit, a detection unit, and a view data generation unit. The X-ray irradiation unit rotates around a subject and radiates an X-ray. The detection part includes a detection element group provided along a channel direction, including a first detection element having a first detection width in the channel direction and a second detection element having a second detection width smaller than the first detection width in the channel direction, and rotates around the subject. The view data generation unit generates view data corresponding to a single view based on a first data group collected by the detection element group when the detection unit is at a first rotation position, and a second data group collected by the detection element group when the detection unit is at a second rotation position different from the first rotation position.SELECTED DRAWING: Figure 1

Description

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

The X-ray Computed Tomography (CT) system collects projection data by irradiating the subject with X-rays and detecting the X-rays that have passed through the subject with an X-ray detector, and the collected projection data. Reconstruct the image from. Here, in the X-ray CT system, for example, the spatial resolution can be improved by reducing the size of the detector element in the X-ray detector.

Japanese Unexamined Patent Publication No. 2016-1550

The problem to be solved by the present invention is to improve the spatial resolution.

The X-ray CT system of the embodiment includes an X-ray irradiation unit, a detection unit, and a view data generation unit. The X-ray irradiation unit rotates around the subject and irradiates X-rays. The detection unit has a first detection element provided along the channel direction and having a first detection width in the channel direction, and the second detection width smaller than the first detection width in the channel direction. It has a second detection element and a group of detection elements including the second detection element, and rotates around the subject. In the view data generation unit, when the detection unit is in the first rotation position, the first data group collected by the detection element group and the detection unit are different from the first rotation position. View data corresponding to a single view is generated based on the second data group collected by the detection element group when it is in the rotation position of 2.

FIG. 1 is a block diagram showing an example of the configuration of the X-ray CT system according to the first embodiment. FIG. 2A is a diagram showing an example of an X-ray detector according to the first embodiment. FIG. 2B is a diagram showing an example of an X-ray detector according to the first embodiment. FIG. 3 is a diagram for explaining processing by the data generation function according to the first embodiment. FIG. 4 is a diagram for explaining control of view data collection according to the first embodiment. FIG. 5A is a diagram for explaining an example of processing by the data generation function according to the first embodiment. FIG. 5B is a diagram for explaining an example of processing by the data generation function according to the first embodiment. FIG. 5C is a diagram showing an example of the configuration of a detection element in the X-ray detector according to the first embodiment. FIG. 5D is a diagram showing an example of the configuration of a detection element in the X-ray detector according to the first embodiment. FIG. 6 is a flowchart for explaining a processing flow of the X-ray CT system according to the first embodiment. FIG. 7 is a diagram for explaining an example of control by the X-ray tube device according to the second embodiment. FIG. 8 is a diagram for explaining control of view data collection according to the second embodiment. FIG. 9 is a flowchart for explaining the processing flow of the X-ray CT system according to the second embodiment. FIG. 10 is a diagram showing an example of an X-ray detector according to another embodiment. FIG. 11 is a diagram for explaining an example of processing by the data generation function according to another embodiment. FIG. 12 is a diagram for explaining an example of processing by the data generation function according to another embodiment. FIG. 13 is a diagram for explaining an example of movement of the X-ray tube device according to another embodiment.

Hereinafter, embodiments of the X-ray CT system will be described in detail with reference to the accompanying drawings. The X-ray CT system according to the present application is not limited to the embodiments shown below. Further, the embodiment can be combined with other embodiments or conventional techniques as long as the processing contents do not conflict with each other.

(First Embodiment)
FIG. 1 is a diagram showing an example of the configuration of the X-ray CT system 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT system 1 according to the first embodiment includes a gantry device 10, a sleeper device 30, and a console device 40.

Here, in FIG. 1, the rotation axis of the rotation frame 13 in the non-tilt state or the longitudinal direction of the top plate 33 of the sleeper device 30 is the Z-axis direction. Further, the axial direction orthogonal to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction. Further, the axial direction orthogonal to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. Note that FIG. 1 is a drawing of the gantry device 10 from a plurality of directions for the sake of explanation, and shows a case where the X-ray CT system 1 has one gantry device 10.

The gantry device 10 includes an X-ray tube device 11, an X-ray detector 12, a rotating frame 13, an X-ray high voltage device 14, a control device 15, a wedge 16, a collimator 17, and a DAS (Data Acquisition System). ) 18 and.

The X-ray tube device 11 has an X-ray tube and a deflection portion. The X-ray tube is a vacuum tube having a cathode (filament) that generates electrons and an anode (target) that generates X-rays in response to collision of thermoelectrons. The X-ray tube irradiates the subject P by irradiating thermoelectrons from the cathode toward the anode by applying a high voltage from the X-ray high-voltage device 14 and emitting X-rays at the focal point of the anode. X-rays are generated. For example, the X-ray tube includes a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermoelectrons.

The deflecting portion deflects thermions emitted from the cathode to change the incident direction of thermions and change the position of the focal point at the anode. That is, the deflection portion changes the direction of the X-rays emitted from the anode. The X-ray tube device 11 is an example of an X-ray irradiation unit.

The X-ray detector 12 has a plurality of detection elements for detecting X-rays. Each detection element in the X-ray detector 12 detects X-rays irradiated from the X-ray tube device 11 and passed through the subject P, and outputs a signal corresponding to the detected X-ray dose to DAS18. The X-ray detector 12 has, for example, a plurality of detection element sequences in which a plurality of detection elements are arranged in a channel direction (channel direction) along one arc centered on the focal point of the X-ray tube device 11. The X-ray detector 12 has, for example, a structure in which a plurality of detection element sequences in which a plurality of detection elements are arranged in the channel direction are arranged in a row direction (slice direction, row direction).

Here, the X-ray detector 12 according to the present embodiment is provided from the first detection element having the first detection width in the channel direction and the first detection width in the channel direction, which are provided along the channel direction. It has a detection element group including a second detection element having a small second detection width, and rotates around the subject. This point will be described in detail later.

For example, the X-ray detector 12 is an indirect conversion type detector having a grid, a scintillator array, and an optical sensor array. The scintillator array has a plurality of scintillators. The scintillator has a scintillator crystal that outputs a photon amount of light according to the incident X dose. The grid is arranged on the surface of the scintillator array on the X-ray incident side and has an X-ray shield plate that absorbs scattered X-rays. The grid may also be called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has a function of converting into an electric signal according to the amount of light from the scintillator, and has, for example, an optical sensor such as a photodiode. For example, the X-ray detector 12 is an energy integration type detector. The X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into an electric signal. The X-ray detector 12 is an example of a detection unit.

The rotating frame 13 is an annular frame that supports the X-ray tube device 11 and the X-ray detector 12 so as to face each other, and rotates the X-ray tube device 11 and the X-ray detector 12 by the control device 15. For example, the rotating frame 13 is a casting made of aluminum. In addition to the X-ray tube device 11 and the X-ray detector 12, the rotating frame 13 can further support the X-ray high voltage device 14, the wedge 16, the collimator 17, the DAS 18, and the like. Further, the rotating frame 13 can further support various configurations (not shown in FIG. 1).

The X-ray high-voltage device 14 has an electric circuit such as a transformer and a rectifier, and generates a high-voltage generator that generates a high voltage applied to the X-ray tube device 11 and an X-ray tube device 11. It has an X-ray control device that controls an output voltage according to X-rays. The high voltage generator may be a transformer type or an inverter type. The X-ray high voltage device 14 may be provided on the rotating frame 13 or on a fixed frame (not shown).

The control device 15 has a processing circuit having a CPU (Central Processing Unit) and the like, and a drive mechanism such as a motor and an actuator. The control device 15 receives an input signal from the input interface 43 and controls the operation of the gantry device 10 and the sleeper device 30. For example, the control device 15 controls the rotation of the rotating frame 13, the tilt of the gantry device 10, the operation of the sleeper device 30 and the top plate 33, and the like. As an example, the control device 15 rotates the rotating frame 13 about an axis parallel to the X-axis direction based on the input tilt angle (tilt angle) information as a control for tilting the gantry device 10. The control device 15 may be provided in the gantry device 10 or in the console device 40.

The wedge 16 is a filter for adjusting the X-ray dose emitted from the X-ray tube device 11. Specifically, the wedge 16 transmits the X-rays emitted from the X-ray tube device 11 so that the X-rays emitted from the X-ray tube device 11 to the subject P have a predetermined distribution. It is a filter that attenuates. For example, the wedge 16 is a wedge filter or a bow-tie filter, which is a filter obtained by processing aluminum or the like so as to have a predetermined target angle and a predetermined thickness.

The collimator 17 is a lead plate or the like for narrowing the irradiation range of X-rays transmitted through the wedge 16, and a slit is formed by a combination of a plurality of lead plates or the like. The collimator 17 may be called an X-ray diaphragm. Further, FIG. 1 shows a case where the wedge 16 is arranged between the X-ray tube device 11 and the collimator 17, but when the collimator 17 is arranged between the X-ray tube device 11 and the wedge 16. There may be. In this case, the wedge 16 is irradiated from the X-ray tube device 11 and transmits and attenuates the X-ray whose irradiation range is limited by the collimator 17.

The DAS 18 collects X-ray signals detected by each detection element included in the X-ray detector 12. For example, the DAS 18 has an amplifier that amplifies an electric signal output from each detection element and an A / D converter that converts the electric signal into a digital signal, and generates detection data. DAS18 is realized by, for example, a processor.

The data generated by the DAS 18 is transmitted from a transmitter having a light emitting diode (LED) provided on the rotating frame 13 by optical communication to a non-rotating portion (for example, a fixed frame or the like. FIG. 1) of the gantry device 10. The light is transmitted to a receiver having a photodiode provided in (not shown in the above) and transferred to the console device 40. Here, the non-rotating portion is, for example, a fixed frame that rotatably supports the rotating frame 13. The method of transmitting data from the rotating frame 13 to the non-rotating portion of the gantry device 10 is not limited to optical communication, and any non-contact data transmission method may be adopted, and the contact-type data transmission method may be used. You may adopt it.

The sleeper device 30 is a device for placing and moving the subject P to be imaged, and has a base 31, a sleeper drive device 32, a top plate 33, and a support frame 34. The base 31 is a housing that supports the support frame 34 so as to be movable in the vertical direction. The sleeper drive device 32 is a drive mechanism that moves the top plate 33 on which the subject P is placed in the long axis direction of the top plate 33, and includes a motor, an actuator, and the like. The top plate 33 provided on the upper surface of the support frame 34 is a plate on which the subject P is placed. In addition to the top plate 33, the sleeper drive device 32 may move the support frame 34 in the long axis direction of the top plate 33.

The console device 40 includes a memory 41, a display 42, an input interface 43, and a processing circuit 44. Although the console device 40 will be described as a separate body from the gantry device 10, the gantry device 10 may include a part of each component of the console device 40 or the console device 40.

The memory 41 is realized by, for example, a RAM (Random Access Memory), a semiconductor memory element such as a flash memory, a hard disk, an optical disk, or the like. The memory 41 stores, for example, projection data and CT image data. Further, for example, the memory 41 stores a program for the circuit included in the X-ray CT system 1 to realize its function. The memory 41 may be realized by a server group (cloud) connected to the X-ray CT system 1 via a network.

The display 42 displays various information. For example, the display 42 displays various images generated by the processing circuit 44, and displays a GUI (Graphical User Interface) for receiving various operations from the operator. For example, the display 42 is a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 42 may be a desktop type, or may be composed of a tablet terminal or the like capable of wireless communication with the console device 40 main body.

The input interface 43 receives various input operations from the operator, converts the received input operations into electric signals, and outputs the received input operations to the processing circuit 44. For example, the input interface 43 receives from the operator input operations such as reconstruction conditions when reconstructing CT image data and image processing conditions when generating a post-processed image from CT image data.

For example, the input interface 43 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad for performing input operations by touching an operation surface, a touch screen in which a display screen and a touch pad are integrated, and an optical sensor. It is realized by the non-contact input circuit, voice input circuit, etc. used. The input interface 43 may be provided in the gantry device 10. Further, the input interface 43 may be composed of a tablet terminal or the like capable of wireless communication with the console device 40 main body. Further, the input interface 43 is not limited to one provided with physical operating parts such as a mouse and a keyboard. For example, an electric signal processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the console device 40 and outputs the electric signal to the processing circuit 44 is also an example of the input interface 43. included.

The processing circuit 44 controls the operation of the entire X-ray CT system 1. For example, the processing circuit 44 executes the control function 441, the preprocessing function 442, the data generation function 443, and the reconstruction function 444. The data generation function 443 is an example of a view data generation unit.

The control function 441 controls various functions of the processing circuit 44 based on the input operation received from the operator via the input interface 43. Further, the control function 441 controls the CT scan performed by the gantry device 10. For example, the control function 441 controls the operations of the X-ray tube device 11, the X-ray detector 12, the X-ray high voltage device 14, the control device 15, the DAS 18, and the sleeper drive device 32 to control the projection data in the gantry device 10. Control the collection process of. As an example, the control function 441 controls the collection process of projection data in the imaging for collecting the positioning image (scano image) and the main imaging (scan) for collecting the image used for diagnosis. Further, the control function 441 controls various image data stored in the memory 41 so as to be displayed on the display 42.

The pre-processing function 442 generates projection data by performing pre-processing such as logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, and beam hardening correction on the detection data output from DAS18. Further, the preprocessing function 442 generates projection data by performing preprocessing such as logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, and beam hardening correction on the view data generated by the data generation function. To do.

The data generation function 443 generates view data using the detection data output from DAS18. Specifically, the data generation function 443 generates view data corresponding to one view using the detection data collected by the plurality of rotation positions. The processing by the data generation function 443 will be described in detail later.

The reconstruction function 444 generates CT image data by performing reconstruction processing using a filter correction back projection method, a successive approximation reconstruction method, or the like on the projection data generated by the preprocessing function 442. The reconstruction function 444 stores the reconstructed CT image data in the memory 41. In addition, the reconstruction function 444 uses a known method to obtain CT image data based on an input operation received from the operator via the input interface 43, such as a tomographic image of an arbitrary cross section or a three-dimensional image obtained by rendering. Convert to. The reconstruction function 444 stores the converted image data in the memory 41.

In the X-ray CT system 1 shown in FIG. 1, each processing function is stored in the memory 41 in the form of a program that can be executed by a computer. The processing circuit 44 is a processor that realizes a function corresponding to each program by reading a program from the memory 41 and executing the program. In other words, the processing circuit 44 in the state where each program is read has a function corresponding to the read program.

Note that FIG. 1 shows a case where each processing function of the control function 441, the preprocessing function 442, the data generation function 443, and the reconstruction function 444 is realized by a single processing circuit 44, but the embodiment shows this. It is not limited to. For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processor may execute each program to realize each processing function. Further, each processing function of the processing circuit 44 may be appropriately distributed or integrated into a single or a plurality of processing circuits.

The overall configuration of the X-ray CT system 1 according to the present embodiment has been described above. Under such a configuration, the X-ray CT system 1 according to the present embodiment makes it possible to improve the spatial resolution or reduce the number of X-ray detecting elements if the spatial resolution is the same. Specifically, in the X-ray CT system 1, the X-ray detector 12 has a first detection element provided along the channel direction and having a first detection width in the channel direction, and a first detection element in the channel direction. It has a detection element group including a second detection element having a second detection width smaller than the detection width of. Then, the control function 441 collects the detection data at each rotation position while rotating the second detection width. Then, the data generation function 443 generates view data which is data corresponding to one view by using the detection data collected at each rotation position. As a result, the X-ray CT system 1 can generate view data with a detection width smaller than the detection width of the first detection element, and can improve the spatial resolution.

The details of the X-ray detector 12 and the processing will be described below. 2A and 2B are diagrams showing an example of the X-ray detector 12 according to the first embodiment. Here, in FIGS. 2A and 2B, the horizontal direction in the figure indicates the channel direction. Further, in FIGS. 2A and 2B, only three detection elements are shown for convenience of explanation.

For example, the X-ray detector 12 includes a detection element 122 having a first detection width and a detection element 121 having a second detection width smaller than the first detection width in the channel direction, as shown in FIG. 2A. Has. Here, the second detection width corresponds to the size obtained by equally dividing the first detection width into N (N is an integer of 2 or more). For example, in the X-ray detector 12 shown in FIG. 2A, the second detection width (horizontal width of the detection element 121) divides the detection width (horizontal width) of the detection element 122 in the channel direction into four equal parts. Corresponds to the size of the

That is, the detection element 121 has the same width as the region 1221a in which the detection element 122 is virtually divided into four equal parts, and the widths of the regions 1221b, the region 1221c, and the region 1221d in the channel direction. As an example, when the detection width of the detection element 122 is "0.5 mm", the detection width of the detection element 121 is "0.125 mm". In the X-ray detector 12, an ADC (Analog-to-Digital converter) or the like is arranged after each detection element, and data is read out for each of the detection element 121 and the detection element 122.

The detection width, position, and number of the detection elements 121 are not limited to those shown in the drawings, and can be arbitrarily designed. That is, the detection width of the detection element 121 can be arbitrarily designed depending on how much the detection element 122 is divided. Further, as shown in FIG. 2A, the position of the detection element 121 may be arranged at the end of the detection element or may be arranged between the detection elements 122. Further, the number of detection elements 121 is not limited to one, and a plurality of detection elements 121 may be arranged.

Here, the detection width of the detection element 121 means the width in the channel direction of the region where X-rays are incident, and is not limited to the actual size of the detection element. That is, the detection element 121 may be designed and manufactured in a size of 1/4 of the detection element 122 as shown in FIG. 2A, but the detection element 122 may be, for example, as shown in FIG. 2B. On the other hand, by mounting the X-ray opaque member 123 of 3/4 size of the detection element 122, the width of the region where X-rays are incident on the detection element 122 is reduced to 1/4 size. It may be the one that has been made. In other words, the X-ray detector 12 according to the present embodiment masks the detection element in a normal X-ray detector with an X-ray opaque member having a size of (N-1) / N of the size of the detection element. By doing so, it may be formed. The X-ray opaque member is, for example, lead or the like.

As described above, the X-ray detector 12 includes a detection element 122 having a first detection width and a detection element 121 having a second detection width smaller than the first detection width. The control function 441 controls to collect data every time the rotation is performed by the second detection width. That is, the control function 441 rotates the rotating frame to rotate the second detection width (1 / N of the size of the detection element 122) when the X-ray tube device 11 and the X-ray detector 12 are continuously rotating. ) Control to collect data one by one.

The data generation function 443 uses the detection data collected under the control of the control function 441 to generate the same detection data as that collected by the detection element having the second detection width. That is, the data generation function 443 is actually collected from the data output from the detection element 122 having the first detection width larger than the second detection width by the detection element having the second detection width. Generate similar detection data. Here, the data generation function 443 actually generates the second detection width from the data output from the detection element 122 when generating the same detection data as that collected by the detection element having the second detection width. The detection element of the detection element 121 having the above is used.

FIG. 3 is a diagram for explaining the process by the data generation function 443 according to the first embodiment. FIG. 3 shows the detection data collected by each detection element when the X-ray detector 12 moves by the second detection width (1/4 of the size of the detection element 122). For example, the control function 441 controls to collect the data of the detection element 121 and the detection element 122 at the rotation position shown in “Sample-1” of FIG.

At this time, the detection data collected by the detection element 121 is based on the photon "P1" incident on the detection element 121, as shown in FIG. Further, as shown in FIG. 3, the detection data collected by the detection element 122 includes a photon "P2" incident on the region 1221a of the detection element 122, a photon "P3" incident on the region 1221b, and a region 1221c. Based on the photon "P4" incident on the region 1221d and the photon "P5" incident on the region 1221d. That is, the detection data collected by the detection element 122 is (P2 + P3 + P4 + P5) as shown in FIG.

Next, the control function 441 controls to collect the data of the detection element 121 and the detection element 122 at the rotation position shown in “Sample-2” of FIG. Here, since the movement of the X-ray detector 12 is as small as the second detection width (1/4 of the size of the detection element 122), the X incident on the detection element 121 after the movement is X. It is assumed that the path of the line and the path of the X-ray incident on the region 1221a in the detection element 122 before the movement are substantially the same. In this case, the detection data collected by the detection element 121 at the rotation position shown in “Sample-2” of FIG. 3 is based on the photon “P2” incident on the detection element 121 as shown in FIG. It will be.

Similarly, the detection data collected by the detection element 122 at the rotation position shown in “Sample-2” of FIG. 3 is the photon “P3” incident on the region 1221a of the detection element 122 as shown in FIG. , The photon "P4" incident on the region 1221b, the photon "P5" incident on the region 1221c, and the photon "P6" incident on the region 1221d. That is, the detection data collected by the detection element 122 is (P3 + P4 + P5 + P6) as shown in FIG.

As described above, in the first embodiment, the X-rays having substantially the same path before and after the movement of the X-ray detector 12 are located at positions shifted by the second detection width (1/4 of the size of the detection element 122). Be incidented. The data generation function 443 uses the detection data detected in this way to generate detection data similar to that collected by the detection element having the second detection width. For example, as shown in FIG. 3, the data generation function 443 has the detection data (P2 + P3 + P4 + P5) collected at the rotation position shown in "Sample-1" and the detection data collected at the rotation position shown in "Sample-2". By differentiating from (P3 + P4 + P5 + P6), a value corresponding to "P2-P6" is acquired.

Here, since the detection data based on the photon "P2" is collected by the detection element 121 at the rotation position shown in "Sample-2", the data generation function 443 has a value corresponding to "P2-P6". , The value of the detection data based on the photon "P2" is used to calculate the detection data based on the photon "P6".

As described above, the data generation function 443 generates the same detection data as that collected by the detection element having the second detection width by differentiating the detection data collected at different rotation positions. For example, when the data generation function 443 virtually divides the detection element 122 into four equal parts and generates the detection data corresponding to each region, the data generation function 443 collects each detection data at the rotation position of "(4 + 1) = 5". It is used to generate one view of detection data similar to that collected by the detection element of the second detection width. That is, the data generation function 443 was collected by the detection element having the second detection width using the detection data collected at the rotation position of “N + 1” when the detection element 122 was virtually divided into “N” equal parts. Generates detection data for one view similar to the one.

FIG. 4 is a diagram for explaining control of view data collection according to the first embodiment. Here, FIG. 4 shows a case where detection data for one view is generated by using each detection data collected at five rotation positions. Further, FIG. 4 shows a diagram in which the anode (target) in the X-ray tube device 11 rotates, and the circle on the target indicates the focal point. In FIG. 4, in order to clearly show each rotation position, the targets at each rotation position are shown apart, but the movement of the target is the second detection width (1/4 of the size of the detection element 122). In reality, the targets at each rotation position are almost overlapped because they are only a few minutes.

For example, the control function 441 controls to collect detection data at each rotation position shown in FIG. That is, the control function 441 controls to collect the detection data detected by the detection element 121 and the detection data detected by the detection element 122 at each rotation position. Here, the detection data collected by the control function 551 becomes one view data for every five rotation positions. For example, in FIG. 4, the X-ray irradiation region R1 irradiated while the target moves to the fifth rotation position from the left is regarded as the same path. Further, for example, in FIG. 4, the irradiation region R2 of the X-rays irradiated while the target moves to the 6th to 10th rotation positions is regarded as the same path.

The data generation function 443 executes a difference process using the detection data collected at each of the five rotation positions, and generates view data for one view. For example, the data generation function 443 executes the difference processing using the detection data of the region R1 shown in FIG. 4 and generates view data for one view. Further, the data generation function 443 executes the difference processing using the detection data of the region R2 shown in FIG. 4 and generates the view data for one view.

Hereinafter, an example of processing by the data generation function 443 will be described with reference to FIGS. 5A and 5B. 5A and 5B are diagrams for explaining an example of processing by the data generation function 443 according to the first embodiment. In FIG. 5A, for convenience of explanation, a case where the X-ray detector 12 has three detection elements 122 and one detection element 121, and the detection elements 121 are arranged between the detection elements 122 is shown. Further, FIG. 5A shows a case where the detection element 122 is virtually divided into four regions. Further, FIG. 5A shows the processing of the data generation function 443 when collecting the view data of one view.

For example, as shown in FIG. 5A, the control function 441 controls the X-ray detector 12 to collect detection data from each detection element every time it moves by the detection width of the detection element 121. That is, as shown in FIG. 5A, the control function 441 is the detection data of the five times of "Sample-1", "Sample-2", "Sample-3", "Sample-4", and "Sample-5". Control collection.

As a result, the control function 441 converts the detection data based on the photon (P1 + P2 + P3 + P4), the detection data based on the photon (P5 + P6 + P7 + P8), the detection data based on the photon "P9", and the photon (P10 + P11 + P12 + P13) in "Sample-1". Collect based detection data.

Further, the control function 441 is based on the detection data based on the photon (P2 + P3 + P4 + P5), the detection data based on the photon (P6 + P7 + P8 + P9), the detection data based on the photon "P10", and the photon (P11 + P12 + P13 + P14) in "Sample-2". Collect detection data.

Further, the control function 441 is based on the detection data based on the photon (P3 + P4 + P5 + P6), the detection data based on the photon (P7 + P8 + P9 + P10), the detection data based on the photon "P11", and the photon (P12 + P13 + P14 + P15) in "Simple-3". Collect detection data.

Further, the control function 441 is based on the detection data based on the photon (P4 + P5 + P6 + P7), the detection data based on the photon (P8 + P9 + P10 + P11), the detection data based on the photon "P12", and the photon (P13 + P14 + P15 + P16) in "Sample-4". Collect detection data.

Further, the control function 441 is based on the detection data based on the photon (P5 + P6 + P7 + P8), the detection data based on the photon (P9 + P10 + P11 + P12), the detection data based on the photon "P13", and the photon (P14 + P15 + P16 + P17) in "Sample-5". Collect detection data.

The data generation function 443 calculates the detection data based on each photon by differentiating the detection data at each rotation position. For example, as shown in FIG. 5A, the data generation function 443 has the detection data (P1 + P2 + P3 + P4) collected at the rotation position shown in "Sample-1" and the detection data collected at the rotation position shown in "Sample-2". By differentiating from (P2 + P3 + P4 + P5), a value corresponding to "P1-P5" is acquired. Further, as shown in FIG. 5A, the data generation function 443 has the detection data (P5 + P6 + P7 + P8) collected at the rotation position shown in "Sample-1" and the detection data collected at the rotation position shown in "Sample-2". By differentiating from (P6 + P7 + P8 + P9), a value corresponding to "P5-P9" is acquired. Further, as shown in FIG. 5A, the data generation function 443 has the detection data (P10 + P11 + P12 + P13) collected at the rotation position shown in "Sample-1" and the detection data collected at the rotation position shown in "Sample-2". By differentiating from (P11 + P12 + P13 + P14), a value corresponding to "P10-P14" is acquired.

Here, since the detection data based on the photon "P9" is collected by the detection element 121 at the rotational position shown in "Sample-1", the data generation function 443 first corresponds to "P5-P9". The value of the detection data based on the photon "P5" is calculated by using the value and the value of the detection data based on the photon "P9". Next, the data generation function 443 calculates the value of the detection data based on the photon "P1" by using the calculated value of the detection data based on the photon "P5" and the value corresponding to "P1-P5". ..

Further, since the detection data based on the photon "P10" is collected by the detection element 121 at the rotation position shown in "Sample-2", the data generation function 443 has a value corresponding to "P10-P14" and a value corresponding to "P10-P14". The value of the detection data based on the photon "P14" is calculated by using the value of the detection data based on the photon "P10".

Similarly, the data generation function 443 differs the detection data collected at the rotation position shown in "Sample-2" from the detection data collected at the rotation position shown in "Sample-3" to "P2". A value corresponding to "-P6", a value corresponding to "P6-P10", and a value corresponding to "P11-P15" are calculated. Further, the data generation function 443 differs the detection data collected at the rotation position shown in "Sample-3" from the detection data collected at the rotation position shown in "Sample-4", thereby "P3-". A value corresponding to "P7", a value corresponding to "P7-P11", and a value corresponding to "P12-P16" are calculated. Further, the data generation function 443 differs the detection data collected at the rotation position shown in "Sample-4" from the detection data collected at the rotation position shown in "Sample-5" to "P4-". A value corresponding to "P8", a value corresponding to "P8-P12", and a value corresponding to "P13-P17" are calculated.

The data generation function 443 includes the value calculated as described above, the value of the detection data based on the photon "P10" collected by the detection element 121 at each rotation position, the value of the detection data based on the photon "P11", and the photon "P11". Using the value of the detection data based on "P12" and the value of the detection data based on the photon "P13", the photons "P6", "P2", "P15", "P7", "P3", "P16" , "P8", "P4", and "P17" to calculate the value of the detection data, respectively.

As a result, the data generation function 443 acquires the values of the detection data of the photons "P1" to "P17" from the detection data obtained from the four detection elements of the three detection elements 122 and one detection element 121. And the spatial resolution can be improved. The data generation function 443 generates the values of the detection data of the photons "P1" to "P17" as view data for one view.

The configuration of the detection element shown in FIG. 5A is an example, and the embodiment is not limited to this. For example, 800 detection elements 122 may be arranged, and each detection element 122 may be virtually divided into four equal parts. In such a case, as shown in FIG. 5A, the projection data for one view is based on the detection data of at least photons "P1" to "P3200" or more. The number of detection data based on each photon constituting the projection data for one view is based on how many detection elements 122 are divided and the number of detection elements 121 included in the X-ray detector 12. For example, when 800 detection elements 122 are arranged, each detection element 122 is virtually divided into four equal parts, and one detection element 121 is included in the detection element 122, the projection data for one view is "(800 x 4). ) + 1 (Number of detection elements 121) + 4 (Number of rotation positions moved by the second detection width) = 3205 "is based on the detection data.

The arrangement of the detection element 121 is arbitrary, but it is desirable that the detection element 121 is arranged near the center in the channel direction of the X-ray detector 12. As described above, in the X-ray CT system 1 of the present application, the detection data based on the photons incident on each region of the detection element 122 is calculated by using the detection data collected by the detection element 121. Therefore, it is desirable that the X-ray detector 12 arranges the detection element 121 so that the detection data collected by the detection element 121 becomes more accurate data. Therefore, for example, the detection element 121 is placed near the center of the X-ray detector 12 in the channel direction so that the X-rays incident on the detection element 121 pass through the subject regardless of the rotation position. To be placed in.

Here, a case where the detection element 121 is arranged at the center of the X-ray detector 12 in the channel direction will be described with reference to FIG. 5B. FIG. 5B shows a case where the X-ray detector 12 has four detection elements 122 and one detection element 121, and the detection element 121 is arranged in the center of the four detection elements 122 for convenience of explanation. .. Further, FIG. 5B shows a case where the detection element 122 is virtually divided into four regions. Further, FIG. 5B shows the processing of the data generation function 443 when collecting the view data of one view.

For example, as shown in FIG. 5B, the data generation function 443 executes a difference process between "Sample-1" and "Sample-2" to obtain a value corresponding to "P1-P5", "P5". A value corresponding to "-P9", a value corresponding to "P10-P14", and a value corresponding to "P14-P18" are calculated. Further, as shown in FIG. 5B, the data generation function 443 executes a difference process between "Sample-2" and "Sample-3" to obtain a value corresponding to "P2-P6", "P6". A value corresponding to "-P10", a value corresponding to "P11-P15", and a value corresponding to "P15-P19" are calculated.

Further, as shown in FIG. 5B, the data generation function 443 executes a difference process between "Sample-3" and "Sample-4" to obtain a value corresponding to "P3-P7", "P7". A value corresponding to "-P11", a value corresponding to "P12-P16", and a value corresponding to "P16-P20" are calculated. Further, as shown in FIG. 5B, the data generation function 443 executes a difference process between "Sample-4" and "Sample-5" to obtain a value corresponding to "P4-P8", "P8". A value corresponding to "-P12", a value corresponding to "P13-P17", and a value corresponding to "P17-P21" are calculated.

Then, the data generation function 443 acquires the value of the detection data of the photons "P1" to "P21" by using the result of the difference processing and the detection data "P9" to "P13" collected by the detection element 121. To do. As described above, in the X-ray CT system 1 of the present application, the detection data based on each photon can be calculated even when one detection element 121 is arranged at the center in the channel direction.

As an example, in the X-ray CT system 1 of the present application, as shown in FIG. 5C, 800 detection elements 122 having a “width: 0.5 mm” are arranged in the channel direction, and “width: 0.125 mm” is arranged in the center thereof. The X-ray detector 12 in which one detection element 121 is arranged can also calculate the detection data in the same manner as the above-described processing. That is, the 400 detection elements 122 arranged on both sides of the detection element 121 are virtually divided into four equal parts. Then, the control function 441 performs sampling every time the X-ray detector 12 moves by "0.125 mm" and collects the detection data for the five rotation positions.

The data generation function 443 acquires the values of the detection data of the photons "P1" to "P3205" by executing the above-mentioned difference processing using the detection data for the five rotation positions. The data generation function 443 generates view data for one view using the values of the detected data of the photons "P1" to "P3205". As a result, the X-ray CT system 1 can improve the spatial resolution by 4 times.

Further, in the X-ray CT system 1 of the present application, as shown in FIG. 5D, an X-ray detector in which 800 detection elements 122 having a “width: 0.5 mm” are arranged in the channel direction is divided into four blocks, and each of them is divided into four blocks. One detection element 121 may be arranged in the block. That is. In the X-ray detector 12, one detection element 121 may be arranged for every 200 detection elements 122. In such a case, the detection element 121 is arranged in the center of 200 detection elements, for example, as shown in FIG. 5D. Then, the control function 441 performs sampling every time the X-ray detector 12 moves by "0.125 mm" and collects the detection data for the five rotation positions.

The data generation function 443 executes the above-mentioned difference processing for each block using the detection data for the five rotation positions. As a result, the calculation process of the detection data can be executed in parallel, and the calculation time can be shortened. 5C and 5D are diagrams showing an example of the configuration of the detection element in the X-ray detector 12 according to the first embodiment.

As described above, in the X-ray CT system 1, the control function 441 moves every time the X-ray detector 12 moves by the second detection width (the detection width of the detection element having a narrow width in which X-rays are incident). , Perform sampling. Then, the data generation function 443 generates view data for one view by executing the difference processing using the detection data for the "N (number of divisions of the detection element 122) + 1" rotation position.

The control function 441 and the data generation function 443 continuously perform the above-described processing during scanning, and generate view data for the number of views required for reconstruction. For example, the control function 441 continuously performs sampling every time the X-ray detector 12 moves by the second detection width while the X-ray detector 12 is rotating. The data generation function 443 uses the detection data collected at the rotation position next to the rotation position used for generating the view data for one view to generate the next view data. For example, when the detection element 122 is divided into four equal parts and the view data for one view is generated using the detection data at the five rotation positions, the data generation function 443 uses the detection data at the first to fifth rotation positions. One view data is generated, and the next view data is generated using the detection data of the 6th to 10th rotation positions. The data generation function 443 continuously generates view data while the X-ray detector 12 rotates around the subject.

Note that the generation of view data is not limited to the above example, and may be executed at any position as long as the number of views required for reconstruction can be collected. As an example, one view data may be generated using the detection data of the 1st to 5th rotation positions, and the next view data may be generated using the detection data of the 11th to 15th rotation positions. ..

The reconstruction function 444 reconstructs the image data by using the view data generated by the data generation function 443. Specifically, the reconstruction function 444 reconstructs the image data using the projection data generated by preprocessing the view data generated by the data generation function 443 by the preprocessing function 442. For example, the reconstruction function 444 acquires projection data for one view based on the detection data of the photons "P1" to "P3205" for a plurality of views, and uses the acquired projection data for the plurality of views. And reconstruct the image data.

Next, an example of the processing procedure by the X-ray CT system 1 will be described with reference to FIG. FIG. 6 is a flowchart for explaining the processing flow of the X-ray CT system 1 according to the first embodiment. Here, step S101 is a step realized by the processing circuit 44 reading and executing the program corresponding to the control function 441. Steps S102 and S103 are steps realized by the processing circuit 44 reading and executing a program corresponding to the data generation function 443. Step S104 and step S105 are steps realized by the processing circuit 44 reading and executing the program corresponding to the reconstruction function 444.

First, the processing circuit 44 collects data every time the X-ray detector 12 moves by the second detection width (step S101). For example, the processing circuit 44 performs sampling every time the X-ray detector 12 moves by "0.125 mm". Then, the processing circuit 44 determines whether or not the data for the N + 1 rotation position has been collected (step S102). That is, the processing circuit 44 determines whether or not data for the “number of divisions of the detection element 122 + 1” rotation position has been collected.

Here, when the data for the N + 1 rotation position is not collected (step S102, negation), the processing circuit 44 returns to step S101 and continues the data collection. On the other hand, when the data for the N + 1 rotation position is collected (step S102, affirmative), the processing circuit 44 executes the difference processing on the collected data to generate the view data and save it in the memory 41. (Step S103).

After that, the processing circuit 44 determines whether or not the view data of the number of views required for the reconstruction has been collected (step S104). Here, when the view data of the number of views required for the reconstruction is not collected (step S104, negation), the processing circuit 44 returns to step S101 and continues the data collection. On the other hand, when the view data of the number of views required for the reconstruction is collected (step S104, affirmative), the processing circuit 44 executes the reconstruction using the collected view data to generate image data (step S104, affirmative). Step S105).

As described above, according to the first embodiment, the X-ray tube device 11 rotates around the subject and irradiates X-rays. The X-ray detector 12 includes a detection element 122 provided along the channel direction and having a first detection width in the channel direction and a detection element 122 having a second detection width smaller than the first detection width in the channel direction. It has a detection element group including 121 and, and rotates around the subject. In the data generation function 443, when the X-ray detector 12 is in the first rotation position, the first data group collected by the detection element group and the X-ray detector 12 are in the first rotation position. View data corresponding to a single view is generated based on the second data group collected by the detection element group when they are in different second rotation positions. Therefore, the X-ray CT system 1 according to the first embodiment uses the detection data collected by the detection element 121 to generate detection data corresponding to the second detection width of the detection data collected by the detection element 122. By calculating, it is possible to improve the spatial resolution.

Further, as described above, according to the first embodiment, the second detection width corresponds to the size obtained by equally dividing the detection width of the detection element 122 into N (N is an integer of 2 or more). The data generation function 443 generates view data based on the N + 1 data group including a plurality of data groups having different rotation positions of the X-ray detector 12 when collected. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to calculate the divided detection data from the detection data collected by the detection element 122.

Further, as described above, according to the first embodiment, the data generation function 443 includes the first path and emits X-rays along a plurality of paths arranged at intervals corresponding to the second detection width. Based on the data collected by detecting with the detection element 122 and the data collected by detecting X-rays along the second path different from any of the plurality of paths with the detecting element 121, the first It corresponds to X-rays along the path and generates data that forms part of the view data. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to arrange the detection element 121 at an arbitrary position of the X-ray detector 12.

Further, as described above, according to the first embodiment, in the collection of the data group used for generating the view data, the second path does not completely match any of the plurality of paths including the first path. .. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to realize even if the paths do not completely match.

Further, as described above, according to the first embodiment, the data generation function 443 includes data forming a part of the view data collected at the first rotation position and the view data collected at the second rotation position. The data for each second detection width in the data collected by the first detection element is calculated based on the difference processing with the data forming a part of the above, and the data collected by the second detection element and the second Generate view data based on the data for each detection width. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to calculate the detection data corresponding to the second detection width of the detection data collected by the detection element 122.

Further, as described above, according to the first embodiment, the detection element 121 is arranged near the center of the X-ray detector 12 in the channel direction. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to collect more accurate data.

Further, as described above, according to the first embodiment, the detection element 121 is arranged for each of the plurality of detection elements 122. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to shorten the calculation time.

Further, as described above, according to the first embodiment, the detection element 121 is formed in the dimension of the second detection width, or when the detection element 121 is located at the end of the X-ray detector. Is formed by covering a part of the detection element 122 with an X-ray opaque member so that the width of the incident surface of X-rays becomes the second detection width. Therefore, the X-ray CT system 1 according to the first embodiment can be realized not only when a detection element having a small size is manufactured but also when an existing detection element is masked.

Further, as described above, according to the first embodiment, the reconstruction function 444 is generated by the data generation function 443 while the X-ray tube device 11 and the X-ray detector 12 are rotating around the subject. Image data is reconstructed based on a plurality of view data. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to reconstruct image data with improved spatial resolution without changing the method from the reconstruction normally used.

As described above, in the X-ray CT system 1 according to the first embodiment, the spatial resolution can be significantly improved without increasing the detector elements such as the detection element and the subsequent ADC by the resolution. Further, the X-ray CT system 1 according to the first embodiment performs sampling every time it moves by the second detection width, which is finer than normal sampling, so that there is less blurring in the image data and the image is in focus. It becomes a thing. For example, in normal sampling, in each detection element, photons collected for a certain period of time determined by the rotation speed and the width of the detection element during rotation are integrated. Therefore, in normal image data, the image is out of focus. On the other hand, since the X-ray CT system 1 according to the first embodiment performs finer sampling, it is possible to reduce the deviation of the focus of the image in the image data.

In the X-ray CT system 1 according to the first embodiment, since fine sampling is performed, the S / N (signal-to-noise ratio) of the detected data after the difference processing is lowered. That is, as the number of divisions of the detection element 122 increases, the S / N decreases. Therefore, the number of divisions of the detection element 122 may be determined according to the degree of decrease in S / N.

(Second Embodiment)
In the first embodiment described above, when X-rays having substantially the same path before and after the movement of the X-ray detector 12 (and the X-ray tube device 11) are incident on positions shifted by the second detection width. explained. However, when the X-ray detector 12 (and the X-ray tube device 11) moves, the X-ray irradiation direction changes even if the movement is slight. Therefore, in the second embodiment, a case where the path is controlled to be the same before and after the movement of the X-ray detector 12 will be described. Hereinafter, the same configurations as those in the first embodiment may be designated by the same reference numerals and description thereof may be omitted.

The X-ray tube device 11 according to the second embodiment includes the X-ray detector 12 so that the focus of the X-ray does not rotate together with the X-ray tube device 11 while the detection element group collects the data group of N + 1. The relative position of the focal point of the X-ray is changed. For example, every time the X-ray detector 12 moves by the second detection width, the deflection unit in the X-ray tube device 11 deflects thermions emitted from the cathode, so that the focus of the X-ray tube is the X-ray tube. It is controlled so as not to rotate together with the device 11.

FIG. 7 is a diagram for explaining an example of control by the X-ray tube device 11 according to the second embodiment. Here, in FIG. 7, the control when the view data for one view is generated from the data for the five rotation positions is shown. Further, FIG. 7 shows a diagram in which the anode (target) in the X-ray tube device 11 and the X-ray detector 12 rotate. Further, FIG. 7 shows a case where one detection element 121 (minimum detector in the figure) is arranged at the center of the X-ray detector 12.

For example, as shown in the focal positions 51 to 55 in FIG. 7, the deflection unit is used for X-rays when the X-ray tube device 11 and the X-ray detector 12 rotate to collect data for the five rotation positions. By changing the position of the focal point, the direction in which X-rays are irradiated is controlled to be constant. For example, the deflector deflects the thermionic beam so that the focal point is at position 51 at the first rotation position. Then, the deflecting portion deflects the thermionic beam emitted from the cathode so that the focal point becomes the position 53, the position 54, and the position 55 in order from the position 52 as the rotation occurs. As a result, the X-ray tube device 11 can irradiate the subject with X-rays from a certain direction regardless of the position of the X-ray tube device 11. Therefore, the X-ray CT system 1 can detect X-rays in the same path with different detection elements by executing the above-mentioned control while the X-ray detector 12 is moving.

Then, when the data for the five rotation positions are collected, the deflection unit controls the focus to be the position 56 at the current position of the X-ray tube device 11. That is, the deflection unit controls the position of the focal point on the anode to return to the same position as the position 51 in the next collection of view data.

Here, an example of controlling the position of the focal point by the deflection unit will be described. For example, it is assumed that one view is detected by 800 detection elements for a fan beam having a spread angle of "50 °", and "1 rotation: 0.3s" (rotation speed: 2π / 0.3 [rad /). s] = 21 [rad / s]). When the distance from the rotation center to the focal center is "50 cm", the dimensions of the detection element 121 are "0.5 / 4 = 0.125 mm", and the movement time of "0.125 mm" is "12 μs", the focal center The moving length of is can be calculated by the following equation (1).

Therefore, assuming that the average angle of the target surface at the anode is "45 °", the moving distance of the focal center on the target surface is given by the following equation (2).

As described above, the moving distance of the focal center on the target surface is "0.73 mm", and this moving distance is within the range of the focal moving distance which is a general specification of the current X-ray tube apparatus. .. Therefore, fixing the path by shifting the focus is feasible.

The X-ray CT system 1 according to the second embodiment performs the above-mentioned focus control and the collection of the view data described in the first embodiment in parallel. For example, as shown in FIG. 8, the deflection unit sequentially moves the focal point to positions 51 to 55 when the X-ray tube device 11 and the X-ray detector 12 rotate to collect data for five rotation positions. .. The X-ray region R1 irradiated during that period can be regarded as the same path. The data generation function 443 executes a difference process using the detection data (detection data collected at each rotation position) of the region R1 detected by the X-ray detector 12, and generates view data for one view. ..

When the rotation position reaches the sixth rotation position, the deflection unit moves the focus to the position 56. Then, the deflection unit sequentially moves the focal point with rotation, as in the control described above. The data generation function 443 executes the difference processing using the detection data of the region R2 (detection data collected at the 6th to 10th rotation positions) detected by the X-ray detector 12, and is for one view. Generate view data.

The X-ray tube device 11 and the data generation function 443 repeat the above-mentioned control and collect the view data of the number of views required for the reconstruction. The maximum number of views can be generated by generating the view data for each of the five rotation positions. However, as described above, if the number of views required for reconstruction can be obtained, the view data can be generated at any timing. It may be the case of generating view data. Note that FIG. 8 is a diagram for explaining the control of view data collection according to the second embodiment.

Next, an example of the processing procedure by the X-ray CT system 1 according to the second embodiment will be described with reference to FIG. FIG. 9 is a flowchart for explaining the processing flow of the X-ray CT system 1 according to the second embodiment. Here, step S201 is a step realized by the processing circuit 44 reading and executing the program corresponding to the control function 441. Steps S202 and S203 are steps realized by the processing circuit 44 reading and executing a program corresponding to the data generation function 443. Steps S204 and S205 are steps realized by the processing circuit 44 reading and executing the program corresponding to the reconstruction function 444.

First, the processing circuit 44 collects data while moving the position of the focal point of the X-ray every time the X-ray detector 12 moves by the second detection width (step S201). Then, the processing circuit 44 determines whether or not the data for the N + 1 rotation position has been collected (step S202).

Here, when the data for the N + 1 rotation position is not collected (step S202, negation), the processing circuit 44 returns to step S201 and continues the data collection. On the other hand, when the data for the N + 1 rotation position is collected (step S202, affirmative), the processing circuit 44 executes the difference processing on the collected data to generate the view data and save it in the memory 41. (Step S203).

After that, the processing circuit 44 determines whether or not the view data of the number of views required for the reconstruction has been collected (step S204). Here, when the view data of the number of views required for the reconstruction is not collected (step S204, negation), the processing circuit 44 returns to step S201 and continues the data collection. On the other hand, when the view data of the number of views required for the reconstruction is collected (step S204, affirmative), the processing circuit 44 executes the reconstruction using the collected view data to generate image data (step S204, affirmative). Step S205).

As described above, according to the second embodiment, the X-ray tube device 11 prevents the focus of the X-ray from rotating with the X-ray tube device 11 while the detection element group collects the data group of N + 1. , The relative position of the X-ray detector 12 and the focal point of the X-ray is changed. Therefore, the X-ray CT system 1 according to the second embodiment can generate view data using the detection data collected by fixing the X-ray path, and acquires image data with improved spatial resolution. It is possible to improve the accuracy of the system.

(Other embodiments)
Although the first and second embodiments have been described so far, various different embodiments may be implemented in addition to the above-mentioned first and second embodiments.

In the above-described embodiment, the case where the X-ray detector 12 has a row of detection elements has been described as an example. However, the embodiment is not limited to this, and the X-ray detector 12 may be in multiple rows. FIG. 10 is a diagram showing an example of the X-ray detector 12 according to another embodiment. When the present application is applied to a multi-row X-ray detector 12, the X-ray detector 12 has a detection element 121 arranged at the center of each row in the channel direction, for example, as shown in FIG. Then, the data generation function 443 generates view data for each column as described above.

The arrangement of the detection elements 121 in the multi-row X-ray detector 12 is not limited to the one shown in the drawing, and the number and position can be arbitrarily changed. Further, the position of the detection element 121 in the channel direction may be changed for each row.

Further, in the above-described embodiment, the case where the detection elements 122 have the same size has been described. However, the embodiment is not limited to this, and different sizes may be used. FIG. 11 is a diagram for explaining an example of processing by the data generation function 443 according to another embodiment. In FIG. 11, for convenience of explanation, the X-ray detector 12 has three detection elements 122 and one detection element 121, and one of the detection elements 122 is 3/4 of the size of the other detection element 122. The case is shown. Further, FIG. 11 shows a case where the detection element 121 is arranged at the end. Further, FIG. 11 shows a case where the detection element 122 having a large size is virtually divided into four regions and the detection element 122 having a small size is virtually divided into three regions. Further, FIG. 11 shows the processing of the data generation function 443 when collecting the view data of one view.

For example, as shown in FIG. 11, the data generation function 443 according to another embodiment can be changed to “P2-P5” by executing a difference process between “Sample-1” and “Sample-2”. The corresponding value, the value corresponding to "P5-P9", and the value corresponding to "P9-P13" are calculated. Further, as shown in FIG. 11, the data generation function 443 executes a difference process between "Sample-2" and "Sample-3" to obtain a value corresponding to "P3-P6", "P6". A value corresponding to "-P10" and a value corresponding to "P10-P14" are calculated.

Further, as shown in FIG. 11, the data generation function 443 executes a difference process between "Sample-3" and "Sample-4" to obtain a value corresponding to "P4-P7", "P7". A value corresponding to "-P11" and a value corresponding to "P11-P15" are calculated. Further, as shown in FIG. 11, the data generation function 443 executes a difference process between "Sample-4" and "Sample-5" to obtain a value corresponding to "P5-P8", "P8". A value corresponding to "-P12" and a value corresponding to "P12-P16" are calculated.

Then, the data generation function 443 acquires the value of the detection data of the photons "P1" to "P16" by using the result of the difference processing and the detection data "P1" to "P5" collected by the detection element 121. To do. As described above, in the X-ray CT system 1 of the present application, the detection data based on each photon can be calculated even when the size of the detection element 122 is changed. Further, the X-ray detector 12 shown in FIG. 11 can acquire the value of the detection data based on the photon "P5" twice. Therefore, for example, the X-ray CT system 1 can use one of the detected data acquired twice for verification, or can take the average of the two data.

Further, in the above-described example of FIG. 11, a case where the detection element 121 is arranged at the end has been described. However, the embodiment is not limited to this, and for example, the detection element 121 may be arranged inside in the channel direction. FIG. 12 is a diagram for explaining an example of processing by the data generation function 443 according to another embodiment. In FIG. 12, for convenience of explanation, the X-ray detector 12 has three detection elements 122 and one detection element 121, and one of the detection elements 122 is 3/4 of the size of the other detection element 122. The case is shown. Further, FIG. 12 shows a case where the detection element 121 is arranged inside in the channel direction. Further, FIG. 12 shows a case where the detection element 122 having a large size is virtually divided into four regions and the detection element 122 having a small size is virtually divided into three regions. Further, FIG. 12 shows the processing of the data generation function 443 when collecting the view data of one view.

For example, as shown in FIG. 12, the data generation function 443 according to another embodiment can be changed to “P1-P5” by executing a difference process between “Sample-1” and “Sample-2”. The corresponding value, the value corresponding to "P5-P9", and the value corresponding to "P10-P13" are calculated. Further, as shown in FIG. 12, the data generation function 443 executes a difference process between "Sample-2" and "Sample-3" to obtain a value corresponding to "P2-P6", "P6". A value corresponding to "-P10" and a value corresponding to "P11-P14" are calculated.

Further, as shown in FIG. 12, the data generation function 443 executes a difference process between "Sample-3" and "Sample-4" to obtain a value corresponding to "P3-P7", "P7". A value corresponding to "-P11" and a value corresponding to "P12-P15" are calculated. Further, as shown in FIG. 12, the data generation function 443 executes a difference process between "Sample-4" and "Sample-5" to obtain a value corresponding to "P4-P8", "P8". A value corresponding to "-P12" and a value corresponding to "P13-P16" are calculated.

Then, the data generation function 443 acquires the value of the detection data of the photons "P1" to "P16" by using the result of the difference processing and the detection data "P9" to "P13" collected by the detection element 121. To do. As described above, in the X-ray CT system 1 of the present application, the detection data based on each photon can be calculated even when the size of the detection element 122 is changed and the detection element 121 is arranged inside. Further, the X-ray detector 12 shown in FIG. 12 can acquire the value of the detection data based on the photon “P13” twice. Therefore, for example, the X-ray CT system 1 can use one of the detected data acquired twice for verification, or can take the average of the two data.

Further, in the second embodiment described above, a case where the path is fixed by changing the position of the focal point of the X-ray has been described. However, the embodiment is not limited to this, and for example, the path may be fixed by mechanically moving the X-ray tube device 11. FIG. 13 is a diagram for explaining an example of movement of the X-ray tube device 11 according to another embodiment.

As shown in the left figure of FIG. 13, the X-ray tube device 11 and the X-ray detector 12 rotate in the direction of the arrow 61 as the rotating frame 13 rotates. In this case, as shown in the right figure of FIG. 13, the X-ray tube device 11 returns the position of the focal point of the X-ray to the original position by moving in the direction of the arrow 62 opposite to the rotation direction. Fix the path. As a result, only the X-ray detector 12 is rotated, and X-rays of the same path can be detected by different detection elements.

In the case of realizing this, for example, when fixing the X-ray tube device 11 to the rotating frame 13, a rail and a driving device are provided between the X-ray tube device 11 and the rotating frame 13. Then, while the drive device collects the view data for one view under the control of the control function 441, the X-ray tube device 11 is moved in the direction different from the rotation direction of the rotation frame 13 by the second detection width. Control to move.

Further, in the above-described embodiment, the case where the difference processing is executed using the detection data generated by DAS has been described. However, the embodiment is not limited to this, and for example, the difference processing may be executed using the projection data generated by the preprocessing function 442.

Further, in the above-described embodiment, the case where the reconstruction function 444 reconstructs using a plurality of view data has been described. Here, the reconstruction function 444 may use the original detection data for reconstruction. As described above, in the X-ray CT system 1 of the present application, since the sampling is finely performed, the S / N of the detected data after the difference processing is lowered. However, the detection element 122 actually collects detection data based on a plurality of photons. Therefore, the detection data based on each photon calculated after the difference processing can be improved to the same S / N as the S / N of the original detection data.

Therefore, the reconstruction function 444 may improve the S / N by using the original detection data when reconstructing using a plurality of view data. Explaining an example with reference to FIG. 5A, the reconstruction function 444 detects detection data (P1 + P2 + P3 + P4) when reconstruction is performed using a plurality of view data including view data based on photons “P1” to “P17”. Reconstruction is performed so as to improve the S / N by using the original detection data such as.

Further, in the above-described embodiment, the case where the difference processing is performed to reconstruct the image data with improved spatial resolution has been described. However, the embodiment is not limited to this, and the reconstruction function 444 can also reconstruct the image data using the original detection data.

Further, in the above-described embodiment, the case where the X-ray detector 12 is an energy integral type detector has been described. However, the embodiment is not limited to this, and for example, the X-ray detector 12 may be a photon counting type detector. In such a case, the above-mentioned detection data becomes a count value for each energy. That is, the data generation function 443 executes the difference processing on the count value for each energy in each detection element.

Further, in the above-described embodiment, the X-ray CT apparatus has been described as an example of the X-ray CT system. However, the embodiment is not limited to this, and the X-ray CT system may be, for example, an X-ray angiography system capable of rotational imaging by an arm. In such a case, the X-ray tube device 11 and the X-ray detector 12 are held by the arm. Then, when rotating imaging with the arm is performed and three-dimensional image data is collected, the processing circuit in the angiography system controls to collect the data every time the arm rotates by the second detection width of the arm. .. Then, the processing circuit in the angiography system collects the view data for one view by executing the difference processing on the collected data.

Further, in the above-described embodiment, the case where the X-ray tube device 11, the X-ray detector 12, the data generation function 443, and the reconstruction function are included in a single device has been described. However, the embodiment is not limited to this, and the X-ray tube device 11, the X-ray detector 12, the data generation function 443, and the reconstruction function may be distributed and arranged in a plurality of devices. .. That is, the X-ray CT system 1 may be realized by a plurality of devices.

For example, an X-ray CT system 1 is realized by connecting an X-ray CT device that collects detection data and a reconstruction device that performs reconstruction to each other via a network and executing processing in cooperation with each other. It may be the case. In such a case, for example, the X-ray CT apparatus generates a plurality of view data and transmits the generated plurality of view data to the reconstruction apparatus on the network. The reconstructing device reconstructs the image data using the received plurality of view data.

The term "processor" used in the above description means, for example, a CPU, a GPU (Graphics Processing Unit), an integrated circuit for a specific application (ASIC), or a programmable logic device (for example, a simple programmable logic device (for example, a simple programmable logic device). It means a circuit such as a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA). The processor realizes a function by reading and executing a program stored in a memory or a storage circuit.

In addition, in FIG. 1, it has been described that a single memory 41 stores a program corresponding to each processing function. However, the embodiment is not limited to this. For example, a plurality of memories 41 may be distributed and arranged, and the processing circuit 44 may read the corresponding program from the individual memories 41. Further, instead of storing the program in the memory 41, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit.

Further, the processing circuit 44 may realize the function by utilizing the processor of the external device connected via the network. For example, the processing circuit 44 reads a program corresponding to each function from the memory 41 and executes it, and also uses an external workstation or cloud connected to the X-ray CT system 1 via a network as a computational resource. , Each function shown in FIG. 1 is realized.

Each component of each device according to the above-described embodiment is a functional concept, and does not necessarily have to be physically configured as shown in the figure. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or part of the device is functionally or physically distributed in arbitrary units according to various loads and usage conditions. It can be integrated and configured. Further, each processing function performed by each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

According to at least one embodiment described above, the spatial resolution can be improved. Alternatively, if the spatial resolution is the same, the number of detection elements of the X-ray detector can be reduced.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 X-ray CT system 11 X-ray tube device 12 X-ray detector 121, 122 Detection element 441 Control function 442 Preprocessing function 443 Data generation function 444 Reconstruction function

Claims (15)

An X-ray irradiation unit that rotates around the subject and irradiates X-rays,
A first detection element provided along the channel direction having a first detection width in the channel direction and a second detection element having a second detection width smaller than the first detection width in the channel direction. A detection element having a detection element group including an element and rotating around the subject,
When the detection unit is in the first rotation position, the first data group collected by the detection element group and the detection unit are in a second rotation position different from the first rotation position. Occasionally, a view data generator that generates view data corresponding to a single view based on the second data group collected by the detection element group.
X-ray CT system equipped with. The second detection width corresponds to the size obtained by dividing the first detection width into N (N is an integer of 2 or more) equally.
The view data generation unit generates the view data based on an N + 1 data group including the first data group and the second data group, which have different rotation positions of the detection unit when collected. The X-ray CT system according to claim 1. The X-ray irradiation unit is relative to the detection unit and the X-ray focus so that the X-ray focus does not rotate with the X-ray irradiation unit while the detection element group collects the N + 1 data group. The X-ray CT system according to claim 2, wherein the position is changed. The view data generation unit
Data collected by detecting X-rays along a plurality of paths including the first path and arranged at intervals corresponding to the second detection width by the first detection element, and the plurality of paths. Based on the data collected by detecting the X-rays along the second path different from any of the above by the second detection element, the view data corresponds to the X-rays along the first path. The X-ray CT system according to any one of claims 1 to 3, which generates data forming a part of the above. The X according to claim 4, wherein in the collection of the first data group and the second data group, the second path does not completely match any of the plurality of paths including the first path. Line CT system. The view data generation unit
The first detection is based on the difference processing between the data forming a part of the view data collected at the first rotation position and the data forming a part of the view data collected at the second rotation position. The data for each of the second detection widths in the data collected by the element is calculated, and the view data based on the data collected by the second detection element and the data for each of the second detection widths is generated. The X-ray CT system according to claim 4 or 5. The X-ray CT system according to any one of claims 1 to 6, wherein the second detection element is arranged near the center of the detection unit in the channel direction. The X-ray CT system according to any one of claims 1 to 6, wherein the second detection element is arranged for each of the plurality of first detection elements. When the second detection element is formed with the dimensions of the second detection width or is arranged at the end of the detection unit, the width of the incident surface of the X-ray is the second detection. The X-ray according to any one of claims 1 to 8, which is formed by covering a part of the detection element having the dimension of the first detection width with an X-ray opaque member so as to have a width. CT system. The X-ray irradiation unit and the detection unit further include a reconstruction unit that reconstructs image data based on a plurality of view data generated by the view data generation unit while rotating around the subject. The X-ray CT system according to any one of claims 1 to 9. The X-ray CT system according to claim 10, wherein the X-ray irradiation unit, the detection unit, the view data generation unit, and the reconstruction unit are included in a single device. A first device having the X-ray irradiation unit, the detection unit, and the view data generation unit, and a second device having the reconstruction unit are provided.
The X-ray CT system according to claim 10, wherein the first device and the second device are connected via a network. The X-ray CT system according to any one of claims 1 to 12, wherein the detection unit is an energy integration type detector. The X-ray CT system according to any one of claims 1 to 12, wherein the detection unit is a photon counting type detector. The X-ray CT system is
An arm for holding the X-ray irradiation unit and the detection unit is provided.
The X-ray CT system according to any one of claims 1 to 12, which is an X-ray angiography system capable of rotationally photographing by the arm.

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