JP2022046946A - X-ray ct apparatus - Google Patents

Abstract

To switch a focal size according to a portion included in an imaging range.SOLUTION: An X-ray CT apparatus according to an embodiment comprises: an imaging system; a specification unit; a decision unit; and a control unit. The imaging system comprises: an X-ray source which irradiates a subject with the X-ray; and a detector which detects the X-ray. The specification unit specifies a plurality of imaging object portions of the subject on the basis of image information of the subject. The decision unit decides a size of an X-ray focus for each of the plurality of specified imaging object portions. The control unit images the plurality of imaging object portions all at once while emitting the X-ray in the decided size of the X-ray focus.SELECTED DRAWING: Figure 1

Description

The embodiments disclosed in this specification and drawings relate to an X-ray CT apparatus.

An X-ray tube in an X-ray CT (Computed Tomography) apparatus has a cathode (filament) that generates thermions and an anode (target) that generates X-rays in response to the collision of thermions. The X-ray tube generates X-rays by irradiating thermions from the filament toward the target by applying a high voltage. Here, an X-ray tube having a plurality of filaments having different focal sizes of thermions irradiated to the target is known.

As such an X-ray tube, for example, an X-ray tube having two filaments, a filament having a small focal size and a filament having a large focal size, for irradiating the thermion toward the target is known. For example, imaging using a filament having a small focal size can obtain a CT image with high resolution, and imaging using a filament having a large focal size can obtain a CT image with low noise.

Japanese Unexamined Patent Publication No. 2011-24806 Japanese Unexamined Patent Publication No. 2019-145435

One of the problems to be solved by the embodiments disclosed in the present specification and the drawings is to make it possible to switch the focal size according to the portion included in the imaging range. However, the problems to be solved by the embodiments disclosed in the present specification and the drawings are not limited to the above problems. The problem corresponding to each effect by each configuration shown in the embodiment described later can be positioned as another problem.

The X-ray CT apparatus according to the embodiment includes an imaging system, a specific unit, a determination unit, and a control unit. The imaging system includes an X-ray source that irradiates the subject with X-rays and a detector that detects the X-rays. The specific unit identifies a plurality of imaging target sites of the subject based on the image information of the subject. The determination unit determines the size of the X-ray focal point for each of the specified plurality of imaging target sites. The control unit photographs the plurality of imaging target portions at once while irradiating X-rays with the size of the determined X-ray focal point.

FIG. 1 is a diagram showing an example of the configuration of the X-ray CT apparatus according to the first embodiment. FIG. 2 is a diagram showing an example of the configuration of the X-ray tube according to the first embodiment. FIG. 3 is a diagram for explaining the control of the focal size by the control function according to the first embodiment. FIG. 4 is a flowchart for explaining a procedure for processing the X-ray CT apparatus according to the first embodiment. FIG. 5 is a diagram showing an example of correspondence information according to the second embodiment. FIG. 6 is a flowchart for explaining a procedure for processing the X-ray CT apparatus according to the second embodiment. FIG. 7 is a diagram for explaining an example of changing the focal size according to the third embodiment. FIG. 8 is a flowchart for explaining a procedure for processing the X-ray CT apparatus according to the third embodiment.

Hereinafter, embodiments of the X-ray CT apparatus will be described in detail with reference to the accompanying drawings. Further, the X-ray CT apparatus 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 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 apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT device 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 longitudinal direction of the rotation axis of the rotation frame 13 in the non-tilt state or 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 device 1 has one gantry device 10.

The gantry device 10 includes an X-ray tube 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). Has 18 and. The X-ray tube 11 (X-ray source) and the X-ray detector 12 are examples of an imaging system.

The X-ray tube 11 is a vacuum tube having a cathode (filament) that generates thermions and an anode (target) that receives the collision of thermions and generates X-rays. The X-ray tube 11 generates X-rays to irradiate the subject P by irradiating thermions from the cathode toward the anode by applying a high voltage from the X-ray high voltage device 14. For example, the X-ray tube 11 includes a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermions. Further, for example, the X-ray tube 11 has an X-ray tube having a plurality of filaments having different focal sizes.

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 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 trains 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 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).

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

The X-ray high-voltage device 14 has an electric circuit such as a transformer and a rectifier, and has a high-voltage generator that generates a high voltage applied to the X-ray tube 11 and an X-ray that is generated by the X-ray tube 11. It has an X-ray control device that controls the output voltage according to the above. 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, 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 11. Specifically, the wedge 16 transmits and attenuates the X-rays emitted from the X-ray tube 11 so that the X-rays emitted from the X-ray tube 11 to the subject P have a predetermined distribution. It is a filter to do. 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, in FIG. 1, a case where the wedge 16 is arranged between the X-ray tube 11 and the collimator 17 is shown, but there is a case where the collimator 17 is arranged between the X-ray tube 11 and the wedge 16. May be good. In this case, the wedge 16 is irradiated from the X-ray tube 11 and transmits and attenuates the X-ray whose irradiation range is limited by the collimator 17.

The DAS 18 collects an X-ray signal 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 of the gantry device 10 (for example, a fixed frame or the like. In FIG. 1). The illustration is omitted), and the light is transmitted to a receiver having a photodiode 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 for moving 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 apparatus 1 to realize its function. Further, for example, the memory 41 stores the setting information. The setting information will be described in detail later. The memory 41 may be realized by a server group (cloud) connected to the X-ray CT device 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 realized by a liquid crystal display, a CRT (Cathode Ray Tube) display, an organic EL display, a plasma display, a touch panel, or the like. The display 42 may be a desktop type, or may be configured by 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. Further, for example, the input interface 43 accepts input operations such as scan conditions, reconstruction conditions when reconstructing CT image data, and image processing conditions when generating post-processed images from CT image data from an operator. ..

For example, the input interface 43 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad for performing an input operation 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 on 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 the one provided with physical operation 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 apparatus 1. For example, the processing circuit 44 executes a control function 441, a preprocessing function 442, a reconstruction processing function 443, an image processing function 444, a specific function 445, and a determination function 446. Here, for example, each processing function executed by the control function 441, the pre-processing function 442, the reconstruction processing function 443, the image processing function 444, the specific function 445, and the determination function 446, which are the components of the processing circuit 44 shown in FIG. Is recorded in the memory 41 in the form of a program that can be executed by a computer. The processing circuit 44 is, for example, a processor, and realizes a function corresponding to each read program by reading and executing each program from the memory 41. In other words, the processing circuit 44 in the state where each program is read out has each function shown in the processing circuit 44 of FIG.

In FIG. 1, when each processing function of the control function 441, the preprocessing function 442, the reconstruction processing function 443, the image processing function 444, the specific function 445, and the determination function 446 is realized by a single processing circuit 44. However, the embodiment is not limited to this. 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 control function 441 controls various processes based on the input operation received from the operator via the input interface 43. Specifically, the control function 441 controls the CT scan performed by the gantry device 10. For example, the control function 441 controls the operation of the X-ray tube 11, the X-ray high voltage device 14, the X-ray detector 12, the control device 15, the wedge 16, the collimator 17, the DAS18, and the sleeper drive device 32. It controls the collection process of CT image data in the apparatus 10. As an example, the control function 441 controls the collection process of projection data in the positioning imaging for collecting the positioning image (scano image) and the imaging (main scan) for collecting the image used for diagnosis.

Further, the control function 441 controls the display 42 to display various image data stored in the memory 41, the results of various analysis processes, and the like. Here, the control function 441 according to the first embodiment changes the focal size in the X-ray tube 11 for each imaging region specified by the specific function 445 described later. This point will be described in detail later. Further, the control function 441 is an example of a control unit and a display control unit.

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 detection data output from DAS18.

The reconstruction processing function 443 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 processing function 443 stores the reconstructed CT image data in the memory 41.

The image processing function 444 uses a known method to process CT image data generated by the reconstruction processing function 443 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 rendering processing. Convert to image data such as a three-dimensional image. The image processing function 444 stores the converted image data in the memory 41.

The specific function 445 identifies a plurality of imaging target parts of the subject based on the image information of the subject. The determination function 446 determines the size of the X-ray focal point for each of the specified plurality of imaging target parts. These will be described in detail later. Further, the specific function 445 is an example of a specific unit. Further, the determination function 446 is an example of the determination unit.

The configuration of the X-ray CT apparatus 1 according to the first embodiment has been described above. Under such a configuration, the X-ray CT apparatus 1 makes it possible to switch the focal size according to the portion included in the imaging range. As described above, the X-ray CT apparatus can perform imaging at different focal sizes. For example, the X-ray CT apparatus can determine an appropriate focal size according to the site and perform imaging at the determined focal size.

However, when a plurality of parts are included in the shooting range of one scan, the entire shooting range is shot with the focal size based on one part, so that it is difficult to shoot with an appropriate focal size for each part. Specifically, the maximum mA of the tube current "mA" at the time of photographing is determined for each tube voltage "kV", but as the focal size becomes smaller, the maximum mA also becomes smaller. Therefore, if multiple parts are included in the shooting range of one scan and it is necessary to shoot with a maximum mA or more that can be used with a small focal size, the entire shooting range of one scan is covered. You will be shooting at a large focal size. As a result, in the shooting range of one scan, a portion to be shot with a small focal size in order to obtain high resolution is shot with a large focal size.

Therefore, in the X-ray CT apparatus 1 according to the present embodiment, a plurality of parts included in the imaging range of one scan are specified, the focal size is determined for each specified region, and imaging is performed with the determined focal size. The focal size is switched according to the part included in the imaging range. Hereinafter, the details of this embodiment will be described.

Here, first, the X-ray tube 11 according to the first embodiment will be described. FIG. 2 is a diagram showing an example of the configuration of the X-ray tube 11 according to the first embodiment. As shown in FIG. 2, the X-ray tube 11 includes a target 111, a filament 112a and a filament 112b, and a grid 113. The target 111 receives thermionic irradiation from the filament 112a and the filament 112b to generate X-rays.

The filament 112a and the filament 112b are formed of, for example, tungsten or the like, and emit thermions when energized under the control of the filament control circuit 144. Here, the filament 112a is a filament in which the number of coil turns is smaller and the focal size of thermions irradiated to the target is smaller than that of the filament 112b. Further, the filament 112b is a filament having a larger number of coil turns and a larger focal size of thermions irradiated to the target as compared with the filament 112a. In the following, the filament 112a may be referred to as a filament for a small focus, and the filament 112b may be referred to as a filament for a large focus.

The grid 113 has a pair of electrodes, and under the control of the grid control circuit 143, the grid 113 changes the orbits of thermions emitted from the filament 112a and the filament 112b by generating an electric field by applying a voltage. Thereby, the grid 113 can change the focal size of thermions emitted from the filament 112a and the filament 112b.

Further, as shown in FIG. 2, the X-ray high voltage device 14 includes a high voltage generator 141, a tube voltage control circuit 142, a grid control circuit 143, and a filament control circuit 144. The high voltage generator 141 is a device that generates a high voltage. The high voltage generator 141 may be a transformer type or an inverter type. The tube voltage control circuit 142 controls the tube voltage supplied to the X-ray tube 11 by controlling the high voltage generator 141 under the control of the processing circuit 44.

The grid control circuit 143 controls the orbits of thermions emitted from the filament 112a and the filament 112b by controlling the grid 113 under the control of the processing circuit 44. For example, the grid control circuit 143 controls the orbits of thermions emitted from the filament 122a and the filament 122b by applying a voltage to the grid 113 to change the focal size of the thermions irradiated to the target.

Here, the grid control circuit 143 can change the focal size stepwise by applying a stepwise different voltage to the grid 113. Further, the grid control circuit 143 changes the focal size of thermions emitted from the filament 112a, which is a filament for small focus, and the focal size of thermions emitted from the filament 112b, which is a filament for large focus.

The filament control circuit 144 emits thermions from the filament 112a and the filament 112b by applying a tube voltage and a tube current under imaging conditions to the filament 112a and the filament 112b under the control of the processing circuit 44. For example, in the case of photographing with a small focus filament, the filament control circuit 144 emits thermions from the filament 112a by applying a tube voltage and a tube current under the imaging conditions to the filament 112a. Further, in the case of photographing with a large focus filament, the filament control circuit 144 causes the thermions to be emitted from the filament 112b by applying the tube voltage and the tube current under the imaging conditions to the filament 112b.

The processing circuit 44 controls the X-ray high-voltage device 14 to perform imaging in which the focal size is switched during one scan.

The specific function 445 specifies a part included in the imaging range of one scan. Specifically, the specific function 445 specifies a plurality of imaging target sites of the subject based on the image information of the subject. For example, the identification function 445 identifies the imaging target portion based on the positioning image collected by the positioning imaging. Here, the specifying function 445 can specify the imaging target portion from the two-dimensional positioning image and the three-dimensional positioning image.

As an example, the specific function 445 detects each of a plurality of imaging target portions included in the three-dimensional positioning image. In such a case, the specific function 445 detects a part such as an organ included in the three-dimensional positioning image (volume data) reconstructed by the reconstruction processing function 443 based on the anatomical landmark. .. Here, the anatomical feature point is a point showing the feature of a specific part such as a bone, an organ, a blood vessel, a nerve, or a lumen. That is, the specific function 445 detects bones, organs, blood vessels, nerves, and cavities included in the volume data by detecting anatomical feature points such as specific organs and bones based on the boxel value of the volume data. Etc. are detected. In addition, the specific function 445 can also detect the positions of the head, neck, chest, abdomen, legs, etc. included in the volume data by detecting the characteristic feature points of the human body.

The determination function 446 determines the size of the X-ray focal point for each of the specified plurality of imaging target parts. Specifically, the determination function 446 determines the focus size for each part based on the resolution preset for each part specified by the specific function 445 and the corresponding focus size. For example, the determination function 446 determines a small focal size for the chest and a large focal size for the abdomen.

Here, the determination function 446 first selects a filament and then determines the focal size in the selected filament when determining the focal size. Specifically, the determination function 446 determines whether to use the filament 112a or the filament 112b based on the protocol information (filament information) preset for the specified site. For example, the determination function 446 can be referred to as the filament 112a from the protocol information set for the chest (lung field) and the protocol information set for the abdomen when the chest and abdomen are included in the imaging range. It is determined which of the filaments 112b is used.

Here, for example, when the filament for small focus is set in the protocol of the chest and the filament for large focus is set in the protocol of the abdomen, the determination function 446 is the filament which is the filament for large focus as the filament used for imaging. Select 112b. That is, the determination function 446 selects the filament 112b, which is a filament for large focus, in consideration of the setting of other imaging conditions.

Then, the determination function 446 determines the focal size in the filament 112b based on the resolution preset for the specified portion. For example, the determination function 446 determines the focal size in which the focal size in the filament 112b is reduced as the focal size of the chest, and determines the focal size in the filament 112b as the focal size of the abdomen.

Here, the resolution for each part is arbitrarily determined and stored in the memory 41, but since the resolution also changes depending on the detector size and the reconstruction function, it is determined in consideration of various conditions. For example, the abdominal reconstruction function does not exceed a predetermined resolution, so that the resolution does not improve even when the focal size is set to the minimum. Therefore, the resolution of the abdomen is set to include the reconstruction function. In this way, by determining the resolution for each part in consideration of various conditions, it is possible to have a margin in the heat capacity of the X-ray tube 11 and reduce the occurrence of waiting time due to OLP (Over Load Protection). can do.

As described above, the grid control circuit 143 can change the focal size stepwise by applying a stepwise different voltage to the grid 113. As an example, the grid control circuit 143 applies a voltage of three stages to the grid 113 under the control of the control function 441, so that the focal size of the filament 112a and the focal size of the filament 112b are 4 respectively. A graduated focus size can be achieved.

For example, the grid control circuit 143 narrows down the focal size of the filament 112b, which is a filament for large focal length, to a focal size "L0" in a state where no voltage is applied, and smaller than "L0" by applying a voltage of the first stage. Focus size "L1" in the closed state, focus size "L2" in the state of being narrowed down to be smaller than "L1" by applying a voltage of the second stage higher than the first stage, and higher than the second stage 3 By applying the voltage of the stage, the focal size "L3" in a state of being narrowed down smaller than "L2" is realized.

Further, for example, the grid control circuit 143 has a focal size of the filament 112a, which is a filament for small focus, of the focal size “S0” in a state where no voltage is applied, and is larger than “S0” by applying a voltage of the first stage. Focus size "S1" in a small aperture state, focus size "S2" in a state of being smaller than "S1" by applying a voltage of the second stage higher than the first stage, and more than the second stage By applying a high third-stage voltage, the focal size "S3" in a state of being narrowed down smaller than "S2" is realized.

For example, the determination function 446 determines the focal size “L3” in which the focal size in the filament 112b is reduced as the focal size of the chest, and determines the focal size “L0” in the filament 112b as the focal size of the abdomen.

Further, the determination function 446 determines the shooting conditions associated with the change in the focal size. For example, the determination function 446 determines the imaging conditions of the chest whose focal size has been changed according to the changed focal size. The determination function 446 determines the imaging conditions set in the protocol as the imaging conditions for the entire imaging range when there is no change from the focal size included in the protocol set according to the site.

The control function 441 photographs a plurality of imaging target portions at once while irradiating X-rays with a determined X-ray focal size. Specifically, the control function 441 controls to change the focal size in one filament selected from a plurality of filaments.

FIG. 3 is a diagram for explaining the control of the focal size by the control function 441 according to the first embodiment. Here, FIG. 3 shows control when the chest and abdomen including the lung field are specified as imaging target sites in the positioning image and the focal size is determined for each. For example, the control function 441 sends a control signal to the X-ray high voltage device 14 to control the emission of thermions from the filament 112b when the main scan in the imaging range including the chest and abdomen is started.

Then, as shown in FIG. 3, the control function 441 transmits a control signal to the grid control circuit 143 in scanning the chest region R1 including the lung field so that the focal size becomes “L3”. A voltage is applied to the grid 113. Further, the control function 441 stops the transmission of the control signal to the grid control circuit 143 in the scan of the abdominal region R2, thereby stopping the application of the voltage to the grid 113 so that the focal size becomes “L0”.

In this way, the control function 441 executes imaging at different focal sizes for each part during one scan. As a result, the X-ray CT apparatus 1 can perform imaging with an appropriate focal size for each portion included in the imaging range. Here, for example, a change in the focal size due to filament switching adjusts the resolution in the channel direction, and a change in the focal size due to the grid 113 adjusts the resolution in the slice direction. Therefore, the X-ray CT apparatus 1 can take an image with an appropriate resolution for each part.

In the above-described embodiment, the case where the focal size is changed for each part and the image is taken has been described. Here, the X-ray CT apparatus 1 can further specify the region of interest included in the site and photograph the region of interest and the region other than the region of interest at different focal sizes.

In such a case, the specific function 445 further specifies the region of interest included in the imaging target portion. For example, the specific function 445 identifies a region of interest included in the site based on anatomical feature points, CAD (Computer aided diagnosis), subject information, and the like. Here, the area of interest is a tumor, a treatment site, or the like. As an example, the specific function 445 identifies a tumor contained in the lung field.

The determination function 446 determines the focal size of the X-ray for the region of interest in the region to be imaged and the region other than the region of interest in the region to be imaged. For example, the determination function 446 determines the focal size for each of the tumor (position containing the tumor in the body axis direction) and the region other than the tumor (position not including the tumor in the body axis direction) in the lung field. The focal size in the region of interest is set according to the type of the region of interest.

The control function 441 photographs the region of interest and the region other than the region of interest at once while irradiating the X-rays with the determined focal size of the X-rays. For example, the control function 441 performs imaging in the lung field at a determined focal size for each of the positions containing the tumor in the body axis direction and the positions containing no tumor in the body axis direction.

In the above-mentioned processing for the region of interest, first, a plurality of parts are specified from the imaging range, the region of interest is specified from any of the specified plurality of parts, and the focal size in the plurality of parts is specified. , And the focal size outside the region of interest and the region of interest may be determined respectively. Alternatively, in the above-mentioned processing for the region of interest, first, a single region is specified from the imaging range, the region of interest is specified from the identified region, and the focal size of the region of interest and the focal size other than the region of interest are determined respectively. It may be the case.

Next, the processing of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart for explaining a procedure for processing the X-ray CT apparatus 1 according to the first embodiment.

Here, steps S101 and S105 in FIG. 4 are steps realized by the processing circuit 44 reading a program corresponding to the control function 441 from the memory 41 and executing the program. Further, step S102 in FIG. 4 is a step realized by the processing circuit 44 reading a program corresponding to the specific function 445 from the memory 41 and executing the program. Further, steps S103 and S104 in FIG. 4 are steps realized by the processing circuit 44 reading a program corresponding to the determination function 446 from the memory 41 and executing the program.

As shown in FIG. 4, in the X-ray CT apparatus 1, first, the processing circuit 44 executes positioning imaging (step S101) and collects positioning images. Then, the processing circuit 44 identifies the imaged portion based on the image information in the positioning image (step S102).

Then, the processing circuit 44 determines the focal size for each specified portion (step S103), and determines the imaging conditions (step S104). After that, the processing circuit 44 executes shooting while changing the focal size during one scan (step S105).

As described above, according to the first embodiment, the imaging system includes an X-ray tube 11 for irradiating a subject with X-rays and an X-ray detector 12 for detecting X-rays. The specific function 445 identifies a plurality of imaging target parts of the subject based on the image information of the subject. The determination function 446 determines the focal size of X-rays for each of the specified plurality of imaging target parts. The control function 441 photographs a plurality of imaging target portions at once while irradiating X-rays with a determined X-ray focal size. Therefore, the X-ray CT apparatus 1 according to the first embodiment makes it possible to switch the focal size according to the portion included in the imaging range.

As a result, for example, in the X-ray CT apparatus 1, one condition affects the other condition even when the X-ray CT apparatus 1 images a part having different required resolutions such as a lung field and an abdomen in a long imaging range including the chest and abdomen. You can shoot without giving.

Further, according to the first embodiment, the specific function 445 further specifies the region of interest included in the imaging target portion. The determination function 446 determines the focal size of the X-ray for the region of interest in the region to be imaged and the region other than the region of interest in the region to be imaged. The control function 441 photographs the region of interest and the region other than the region of interest at once while irradiating the X-rays with the determined focal size of the X-rays. Therefore, the X-ray CT apparatus 1 according to the first embodiment makes it possible to perform imaging with a different focal size in a region other than the region of interest and the region of interest.

Further, according to the first embodiment, the X-ray tube 11 has a plurality of filaments having different focal sizes. The control function 441 controls to change the focal size in one filament selected from a plurality of filaments. Therefore, the X-ray CT apparatus 1 according to the first embodiment makes it possible to change the focal size during scanning.

(Second embodiment)
In the first embodiment described above, a case where the focal size is switched for each part included in the imaging range has been described. In the second embodiment, the case where the focal size is determined based on the site and the tube current will be described. Here, in the X-ray CT apparatus 1 according to the second embodiment, the information stored in the memory 41 and the processing contents by the control function 441 and the determination function 446 are different from those in the first embodiment. Hereinafter, this will be mainly described.

The memory 41 according to the second embodiment stores correspondence information in which the tube current and the focal size are associated with each part. FIG. 5 is a diagram showing an example of correspondence information according to the second embodiment. For example, as shown in FIG. 5, the memory 41 stores the corresponding information in which the “site”, the “mA (tube current)”, and the “focal point size” are associated with each other.

As an example, the memory 41 has "mA: mA <a, focal size: S1", "mA: a≤mA <b, focal size: L3", and "focal size: L3" with respect to "part: head". The correspondence information associated with "mA: b≤mA, focal size: L2" is stored. Such correspondence information indicates that the focal size is "S1" when the imaging region is the "head" and the tube current is "mA <a". Further, it is shown that the focal size is set to "L3" when the imaging portion is the "head" and the tube current is "a≤mA <b". Further, it is shown that the focal size is set to "L2" when the imaging portion is the "head" and the tube current is "b≤mA".

Then, as shown in FIG. 5, the memory 41 stores similar correspondence information with respect to other parts such as the chest and abdomen.

The determination function 446 according to the second embodiment determines the focal size of X-rays to be irradiated to each position of the subject based on the corresponding information in which the tube current and the focal size are associated with each imaging target portion. .. Specifically, the determination function 446 acquires information on the portion to be imaged and information on the tube current, and determines the focal size based on the corresponding information stored in the memory 41.

For example, the determination function 446 acquires information on the site specified by the specific function 445. Here, the site information may be acquired not only from the information specified by the specific function 445 but also from other information. For example, the determination function 446 can acquire information on the part to be imaged from the information of the set protocol, the subject information, the part information input via the input interface 43, and the like.

Further, the determination function 446 acquires the value of the tube current determined by the Auto Exposure Control (AEC) executed by the control function 441. Here, the control function 441 can determine mA according to the body thickness of the subject by AEC based on the positioning image. For example, the control function 441 sets mA high when the body thickness is thick, and sets mA low when the body thickness is thin. Further, for example, the control function 441 sets mA in a region with a large amount of absorption and a region with a small amount of absorption in the body axis direction, respectively, based on the difference in X-ray absorption in the body axis direction. Further, for example, the control function 441 sets mA for each view based on the difference in X-ray absorption in the axial cross section. The determination function 446 acquires the information of the mA set by the control function 441.

Then, the determination function 446 determines the focal size by comparing the acquired site information and the mA value with the corresponding information. For example, the determination function 446 determines the focal size as "L3" when the acquired site information is "head" and the acquired mA value is "a≤mA <b".

The control function 441 according to the second embodiment is based on a part to be imaged of the subject and an X-ray tube current irradiating each position of the subject determined based on the image information of the subject. The focal size of the X-rays emitted to each position of the above is controlled. Specifically, the control function 441 takes an image while irradiating each position of the subject with X-rays at a determined focal size of X-rays.

As mentioned above, in the second embodiment, the focal size is determined based on the site and tube current. Here, the control described in the second embodiment can be carried out in combination with the control described in the first embodiment. In such a case, for example, the determination function 446 determines the focal size of each of the plurality of sites specified by the specific function 445 based on the site and the tube current. Then, the control function 441 executes imaging with a determined focal size for each of the plurality of portions included in the imaging range.

Next, the processing of the X-ray CT apparatus 1 according to the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart for explaining a procedure for processing the X-ray CT apparatus 1 according to the second embodiment. Note that FIG. 6 shows a process in which the specific function 445 specifies a portion included in the imaging range.

Here, steps S201 and S205 in FIG. 6 are steps realized by the processing circuit 44 reading a program corresponding to the control function 441 from the memory 41 and executing the program. Further, step S202 in FIG. 6 is a step realized by the processing circuit 44 reading a program corresponding to the specific function 445 from the memory 41 and executing the program. Further, steps S203 and S204 in FIG. 6 are steps realized by the processing circuit 44 reading a program corresponding to the determination function 446 from the memory 41 and executing the program.

As shown in FIG. 6, in the X-ray CT apparatus 1, first, the processing circuit 44 executes positioning imaging (step S201) and collects positioning images. Then, the processing circuit 44 identifies the imaged portion based on the image information in the positioning image (step S202).

Then, the processing circuit 44 determines mA based on the image information (step S203), and determines the focal size according to the site and mA (step S204). After that, the processing circuit 44 executes shooting at the determined focal size (step S205).

As described above, according to the second embodiment, the imaging system includes an X-ray tube 11 that irradiates a subject with X-rays and an X-ray detector 12 that detects X-rays. The control function 441 irradiates each position of the subject with X based on the part to be imaged of the subject and the X-ray tube current irradiating each position of the subject determined based on the image information of the subject. Controls the focus size of the line. Therefore, the X-ray CT apparatus 1 according to the second embodiment can determine the focal size from the site information and the tube current information, and enables imaging with a more optimum focal size.

For example, even when the same site is targeted, the appropriate mA may differ for each subject. Further, even when different parts are targeted, the same mA may be set by AEC. Therefore, when setting the focal size, if it is set only from the part information or only the mA information, the focal size may not be appropriate. Therefore, as described above, the X-ray CT apparatus 1 according to the second embodiment enables imaging with a more optimum focal size by determining the focal size from the site information and the tube current information. ..

Further, according to the second embodiment, the determination function 446 focuses the X-rays to be applied to each position of the subject based on the corresponding information in which the tube current and the focal size are associated with each image pickup target portion. Determine the size. The control function 441 takes an image while irradiating each position of the subject with X-rays at a determined focal size of X-rays. Therefore, the X-ray CT apparatus 1 according to the second embodiment makes it possible to easily determine the focal size based on the site and mA.

(Third embodiment)
In the first embodiment described above, a case where the focal size is determined for each of a plurality of regions in the body axis direction and the shooting is performed while switching the focal size has been described. In the third embodiment, a case where the focal size is changed during one rotation will be described. Here, the X-ray CT apparatus 1 according to the third embodiment is different from the first embodiment in the processing contents by the control function 441 and the determination function 446. Hereinafter, these will be mainly described.

The determination function 446 according to the third embodiment determines the focal size at each position during one rotation. For example, the determination function 446 determines the focal size for each view during one rotation by the rotation frame 13 based on the image information of the subject. As an example, the determination function 446 determines the focal size for each view based on the mA set for each view based on the difference in X-ray absorption in the axial cross section.

The control function 441 according to the third embodiment controls to make the focal size of X-rays in the X-ray tube 11 different during one rotation by the rotating frame 13 based on the image information of the subject. For example, the control function 441 shoots while irradiating X-rays with a focal size determined for each view. FIG. 7 is a diagram for explaining an example of changing the focal size according to the third embodiment. Here, FIG. 7 shows a change in the focal size in the axial cross section of the chest. Further, P1 to P4 in FIG. 7 indicate positions during one rotation, the position P1 corresponds to the front side (abdomen) side of the subject, the position P2 corresponds to the right side surface side of the subject, and the position P3 is covered. It corresponds to the back (back) side of the specimen, and the position P4 corresponds to the left side of the subject. That is, the positions P1 to P4 in FIG. 7 are a range of angles obtained by dividing 360 degrees around the subject by 90 degrees.

For example, the determination function 446 determines "S3" as the focal size of the view including the position P1 and the position P3 shown in FIG. 7 based on the mA set for each view, and the position P2 and the position P4 shown in FIG. Determine "S1" as the focal size of the included view.

The control function 441 controls the focus size to be "S3" in the view including the position P1 and the position P3, and controls the focus size to be "S1" in the view including the position P2 and the position P4. Perform shooting.

As described above, in the third embodiment, shooting is performed by changing the focal size during one rotation. In this case, the reconstruction processing function 443 may perform reconstruction in consideration of the focal size in the reconstruction of the projection data collected by changing the focal size. For example, the reconstruction processing function 443 executes reconstruction using the information of the switched focal size when performing reconstruction by the successive approximation reconstruction method.

Further, the above-mentioned third embodiment can be carried out in combination with the first embodiment and the second embodiment as appropriate. For example, when the third embodiment is combined with the first embodiment, the determination function 446 determines the focal size for each view for the plurality of parts. Then, the control function 441 executes the imaging at the focal size determined for each view in the imaging of each portion.

Further, for example, when the third embodiment is combined with the second embodiment, the determination function 446 determines the focal size of each view based on the mA and the site information set for each view. Then, the control function 441 executes shooting at a focal size determined for each view.

Further, for example, when the third embodiment is combined with the first embodiment and the second embodiment, the determination function 446 has each of the plurality of parts based on the mA and the part information set for each view. Determines the focus size of the view. Then, the control function 441 executes photographing of a plurality of parts with a focal size determined for each view.

Next, the processing of the X-ray CT apparatus 1 according to the third embodiment will be described with reference to FIG. FIG. 8 is a flowchart for explaining a procedure for processing the X-ray CT apparatus 1 according to the third embodiment. Note that FIG. 8 shows a process in which the specific function 445 specifies a portion included in the imaging range.

Here, steps S301 and S305 in FIG. 8 are steps realized by the processing circuit 44 reading a program corresponding to the control function 441 from the memory 41 and executing the program. Further, step S302 in FIG. 8 is a step realized by the processing circuit 44 reading a program corresponding to the specific function 445 from the memory 41 and executing the program. Further, steps S303 and S304 in FIG. 8 are steps realized by the processing circuit 44 reading a program corresponding to the determination function 446 from the memory 41 and executing the program.

As shown in FIG. 8, in the X-ray CT apparatus 1, first, the processing circuit 44 executes positioning imaging (step S301) and collects positioning images. Then, the processing circuit 44 identifies the imaged portion based on the image information in the positioning image (step S302).

Then, the processing circuit 44 acquires the information of mA for each view (step S303), and determines the focal size for each view (step S304). After that, the processing circuit 44 executes shooting while changing the focal size during one rotation (step S305).

As described above, according to the third embodiment, the imaging system includes an X-ray tube 11 for irradiating a subject with X-rays and an X-ray detector 12 for detecting X-rays. The rotating frame 13 supports the imaging system and rotates the imaging system around the subject. The control function 441 controls to make the focal size of the X-ray in the X-ray tube 11 different during one rotation by the rotating frame 13 based on the image information of the subject. Therefore, the X-ray CT apparatus 1 according to the third embodiment can change the focal size during one rotation, and enables imaging with the optimum focal size.

Further, according to the third embodiment, the determination function 446 determines the focal size for each view during one rotation by the rotation frame 13 based on the image information of the subject. The control function 441 shoots while irradiating X-rays with a focal size determined for each view. Therefore, the X-ray CT apparatus 1 according to the third embodiment can control the focal size for each view, and enables shooting with a more optimum focal size.

(Fourth Embodiment)
In the fourth embodiment, a case where various information based on the focal size is displayed will be described. Here, the X-ray CT apparatus 1 according to the fourth embodiment has different processing contents by the control function 441 as compared with the first embodiment. Hereinafter, this will be mainly described.

The control function 441 according to the fourth embodiment displays information based on the amount of heat in the X-ray tube 11 estimated from the imaging conditions including the focal size. Specifically, the control function 441 estimates the change in the amount of heat in the X-ray tube 11 based on the imaging conditions determined by the determination function 446, and displays various information based on the estimation result on the display 42.

As described above, the determination function 446 determines the imaging conditions including the focal size according to the imaging target portion specified based on the positioning image. For example, the determination function 446 determines the imaging conditions including the tube current “mA”, the tube voltage “kV”, the focal size, etc., based on the imaging target portion and the information of the corresponding protocol.

The control function 441 estimates the change in the amount of heat in the target of the X-ray tube 11 when the main scan is executed under the determined imaging conditions. Then, the control function 441 determines whether or not the main scan under the determined shooting conditions is possible based on the current heat quantity at the target, the estimated change in the heat quantity, and the limit heat quantity at the target. Various information based on the determination result is displayed on the display 42.

Here, first, the amount of heat in the target will be described. The target of the X-ray tube 11 has a limit heat amount, which is an allowable heat amount, and control is executed so as not to exceed this limit heat amount. That is, the control function 441 calculates the allowable heat amount from the difference between the current target heat amount and the limit heat amount, and compares the allowable heat amount with the heat amount based on the shooting conditions to determine whether or not the limit heat amount is exceeded. Is determined.

The amount of heat in the target is calculated by, for example, "amount of heat = coefficient x tube voltage (kV) x tube current (mA) x time (t)". The control function 441 calculates the amount of heat based on the imaging conditions by applying each numerical value included in the imaging conditions to the above equation, and compares the amount of heat based on the calculated imaging conditions with the allowable amount of heat.

Here, the control function 441 according to the present embodiment calculates the amount of heat based on the above-mentioned imaging conditions in consideration of the focal size. When the conditions other than the focal size are the same, the change in the amount of heat in the target changes according to the focal size. For example, when the focal size is small, the change in the local amount of heat of the target is large, so that the smaller the focal size, the smaller the margin of the allowable amount of heat. That is, the time during which continuous shooting is possible is reduced.

Therefore, the control function 441 according to the present embodiment calculates the amount of heat based on the shooting conditions based on the above formula plus the focal size factor. Specifically, the control function 441 has a tube current "mA", a tube voltage "kV", a focal size, and a time required for imaging (X-rays are irradiated) included in the imaging conditions determined by the determination function 446. Time) is applied to the equation with the focal size factor added to calculate the amount of heat based on the imaging conditions. The time required for shooting may be calculated from the shooting range, the scanning method (helical scan or non-helical scan), the rotation speed of the rotating frame 13, the moving speed of the top plate 33, and the like.

For example, the determination function 446 determines the tube current “mA”, the tube voltage “kV”, the focal size, and the like from the positioning image and the protocol information. Further, the determination function 446 determines a standard imaging range based on the site information included in the protocol information. Here, the imaging range determined here may include a single imaging target portion, or may include a plurality of imaging target regions. That is, the determination function 446 may determine the imaging conditions for a single imaging target portion, or may determine the imaging conditions for each of the plurality of imaging target regions.

The control function 441 calculates the change in the amount of heat in consideration of the focal size when the main scan is executed based on the shooting conditions determined by the determination function 446. That is, the control function 441 calculates how much heat is generated in the target when the determined imaging range is photographed under the imaging conditions determined by the determination function 446. Here, when the imaging range includes only a single imaging target portion, the control function 441 calculates a change in the amount of heat based on the imaging conditions for the imaging target portion. On the other hand, when a plurality of imaging target portions are included in the imaging range, the control function 441 calculates a change in the amount of heat from each imaging condition for each imaging target portion.

Further, the control function 441 acquires the heat amount of the target at the present time after taking the positioning image and the limit heat amount of the target, and calculates the allowable heat amount by differentiating the acquired values. Then, the control function 441 determines whether or not the shooting in the determined shooting range can be executed by comparing the change in the amount of heat based on the shooting conditions with the allowable amount of heat. That is, the control function 441 determines whether or not the change in the amount of heat based on the shooting conditions exceeds the allowable amount of heat, and if the change in the amount of heat based on the shooting conditions does not exceed the allowable amount of heat, the determined shooting is performed. Judge that shooting in the range is feasible. On the other hand, the control function 441 determines that it is impossible to perform shooting in the determined shooting range in one shooting when the change in heat amount based on the shooting conditions exceeds the allowable heat amount.

Then, the control function 441 displays various information based on the above-mentioned determination result on the display 42. For example, the control function 441 displays the range that can be photographed in the photographing range on the display 42. As an example, when the control function 441 determines that the shooting in the determined shooting range can be performed, the information indicating that the shooting range can be shot in one shot (for example, the positioning image can be shot). The display image) in which the range is superimposed is displayed on the display 42.

On the other hand, when the control function 441 determines that the determined shooting range cannot be shot in one shot, the control function 441 superimposes the shotable range on the positioning image (for example, the information indicating the range that can be shot in one shot). The displayed image) is displayed on the display 42. The control function 441 is once based on the X-ray irradiation time at which the change in the amount of heat based on the imaging conditions is equal to the allowable amount of heat, the moving speed of the top plate 33, and the rotation speed of the rotating frame 13. It is possible to specify the range that can be taken by shooting.

Further, when the control function 441 determines that the determined shooting range cannot be shot in one shot, the control function 441 can shoot in one shot by changing the shooting conditions (for example, increasing the focal size). It is possible to further determine whether or not. That is, the control function 441 changes the shooting conditions in various ways, and determines whether or not the change in the amount of heat based on the changed shooting conditions is less than the allowable amount of heat. Here, when shooting is possible with one shooting, the control function 441 displays the changed shooting conditions on the display 42 as recommended shooting conditions. It should be noted that the change of the shooting condition is executed within the range where the image quality and the like satisfy a predetermined condition.

Further, the control function 441 can reduce the focal size when it is determined that the determined shooting range can be shot in one shot and the focal size included in the shooting conditions is large. Whether or not it can be further determined. That is, the control function 441 changes the focal size to a smaller focal size, and determines whether or not the change in the amount of heat based on the shooting condition in which the focal size is changed is less than the allowable amount of heat. Here, even if the focus size is changed, if it is possible to shoot with one shooting, the control function 441 sets the changed shooting conditions (changed focus size) to the display 42 as recommended shooting conditions. Display.

As described above, according to the fourth embodiment, the control function 441 captures the amount of heat in the X-ray tube 11 when the imaging target portion is imaged while irradiating the X-ray with the determined X-ray focal size. The change is estimated, and the information based on the estimation result is displayed on the display 42. Therefore, the X-ray CT apparatus 1 according to the fourth embodiment makes it possible to estimate the change in the calorific value of the target in consideration of the focal size and present the information based on the estimation result.

Further, according to the fourth embodiment, the control function 441 specifies a range that can be photographed by one X-ray irradiation based on the estimation result, and displays the specified range on the display 42. Therefore, the X-ray CT apparatus 1 according to the fourth embodiment makes it possible to present a range that can be photographed in one imaging.

Further, according to the fourth embodiment, the control function 441 determines whether or not the imaging range including the imaging target portion can be captured by one X-ray irradiation based on the estimation result, and one X-ray. When it is determined that imaging is not possible due to irradiation, it is further determined whether or not the imaging range including the imaging target portion can be photographed with one X-ray irradiation by changing the imaging conditions including the focal size, and once. When it is determined that shooting is possible by X-ray irradiation, the changed shooting conditions are displayed on the display 42. Therefore, the X-ray CT apparatus 1 according to the fourth embodiment can present alternative imaging conditions even when imaging becomes impossible in one imaging, and can reduce the time and effort of the operator. enable.

Further, according to the fourth embodiment, the control function 441 determines whether or not the imaging range including the imaging target portion can be captured by one X-ray irradiation based on the estimation result, and one X-ray. When it is determined that shooting is possible by irradiation, it is further determined whether or not the focal size can be reduced, and when it is determined that the focal size can be reduced, the information on the changed focal size is displayed on the display 42. To display. Therefore, the X-ray CT apparatus 1 according to the fourth embodiment presents imaging conditions that can obtain higher resolution without requiring a waiting time even when imaging is possible in one imaging. Enables.

(Other embodiments)
By the way, although the first to fourth embodiments have been described so far, various different embodiments may be implemented in addition to the first to fourth embodiments described above.

In the above-described embodiment, the case where the X-ray tube 11 has a plurality of filaments (filament 112a and filament 112b) and the focal size in each filament is changed by the grid 113 has been described. However, the embodiment is not limited to this, and any configuration may be used as long as the focal size can be changed during scanning.

For example, the X-ray tube 11 may have a single filament and the focal size in the filament may be changed by the grid 113. Further, for example, the X-ray tube 11 may have a plurality of filaments having different focal sizes and emit electrons from each filament to the same region of the target at the same time to form an intermediate size focal point.

Further, in the third embodiment described above, as an example of changing the focal size for each view, a case where the focal size is changed at positions P1 to P4 in which 360 degrees around the subject is divided every 90 degrees has been described ( See FIG. 7). However, the embodiment is not limited to this, and the change of the focus size for each view can be performed arbitrarily.

For example, the division of 360 degrees around the subject is not limited to the above-mentioned four divisions, and can be set by any number. As an example, the division of 360 degrees around the subject is the number of divisions set by the operator, the number of divisions set for each part, the number of divisions based on the minimum angular interval required for tube current modulation, and the focal size. It is possible to set the number of divisions based on the minimum time interval required to change.

Further, in the example shown in FIG. 7, the boundary position (division position) for changing the focal size is set to 45 degrees, 135 degrees, 225 degrees, and 315 degrees when the front of the subject is 0 degrees. Explained. However, the embodiment is not limited to this, and the division position can be set to an arbitrary position. For example, the division position can be set to a position set by the operator, a position set for each part, and the like.

Further, in the third embodiment described above, as an example of changing the focal size for each view, changing the focal size at positions P1 to P4, which is a range of angles every 90 degrees, has been described. That is, in the third embodiment described above, the view group included in the angle range of the position P1, the view group included in the angle range of the position P2, the view group included in the angle range of the position P3, and the position P4. The case where the focal size is changed for each of the views included in the angle range has been described. However, the embodiment is not limited to this, and the focal size may be changed every one view, which is a projection from a specific tube position, or every few views.

Further, in the above-described embodiment, it has been described that the processing circuit 44 executes a plurality of functions, but the embodiment is not limited to this. For example, a plurality of functions may be provided in the console device 40 as independent circuits so that each circuit executes each function.

Each component of each device illustrated in 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 them may be functionally or physically distributed / physically in arbitrary units according to various loads and usage conditions. 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.

Further, among the processes described in the above-described embodiment, a part of the processes described as being automatically performed can be manually performed, or all the processes described as being manually performed can be performed. Alternatively, a part may be automatically performed by a known method. In addition, the processing procedure, control procedure, specific name, and information including various data and parameters shown in the above document and drawings can be arbitrarily changed unless otherwise specified.

The word "processor" used in the above description is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an integrated circuit for a specific application (Application Specific Integrated Circuit: ASIC), or a programmable logic device (programmable logic device). For example, 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 the function by reading and executing the program stored in the memory 41. 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. It should be noted that each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, and a plurality of independent circuits may be combined to form one processor to realize its function. good. Further, a plurality of components in each figure may be integrated into one processor to realize the function.

Here, the method described in the above-described embodiment can be realized by executing a program prepared in advance on a computer such as a personal computer or a workstation. This program is provided in advance in a ROM (Read Only Memory), a memory, or the like. This program is a file in a format that can be installed or executed on these devices, such as CD (Compact Disk) -ROM, FD (Flexible Disk), CD-R (Recordable), DVD (Digital Versatile Disk), etc. It may be stored and provided on a computer-readable storage medium. Further, this program may be stored on a computer connected to a network such as the Internet, and may be provided or distributed by being downloaded via the network. For example, this program is composed of modules including each functional part described later. As actual hardware, the CPU reads a program from a storage medium such as a ROM and executes the program, so that each module is loaded on the main storage device and generated on the main storage device.

According to at least one embodiment described above, the focal size can be switched according to the portion included in the imaging range.

Although some embodiments 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 embodiments, and various omissions, replacements, changes, and combinations of embodiments can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 X-ray CT device 11 X-ray tube 12 X-ray detector 44 Processing circuit 112a, 112b Filament 441 Control function 445 Specific function 446 Decision function

Claims (11)

An imaging system including an X-ray source that irradiates a subject with X-rays and a detector that detects X-rays,
Based on the image information of the subject, a specific part that specifies a plurality of imaging target parts of the subject, and a specific portion.
A determination unit that determines the focal size of X-rays for each of the specified plurality of imaging target parts, and
A control unit that captures a plurality of imaging target sites at once while irradiating X-rays with the determined focal size of the X-rays.
X-ray CT apparatus. An imaging system including an X-ray source that irradiates a subject with X-rays and a detector that detects X-rays,
X-rays to irradiate each position of the subject based on the part to be imaged of the subject and the tube current of the X-ray to irradiate each position of the subject determined based on the image information of the subject. A control unit that controls the focal size of the
X-ray CT apparatus. An imaging system including an X-ray source that irradiates a subject with X-rays and a detector that detects X-rays,
A rotating part that supports the imaging system and rotates the imaging system around the subject.
A control unit that controls the focus size of X-rays in the X-ray source to be different during one rotation by the rotating unit based on the image information of the subject.
X-ray CT apparatus. The specific portion further identifies the region of interest included in the imaging target portion, and further identifies the region of interest.
The determination unit determines the focal size of X-rays for the region of interest in the region to be imaged and the region other than the region of interest in the region to be imaged.
The X-ray CT apparatus according to claim 1, wherein the control unit photographs a region of interest and a region other than the region of interest at once while irradiating X-rays with the determined focal size of the X-rays. Further provided with a determination unit for determining the focal size of X-rays to irradiate each position of the subject based on the corresponding information in which the tube current and the focal size are associated with each imaging target portion.
The X-ray CT apparatus according to claim 2, wherein the control unit takes an image while irradiating each position of the subject with X-rays at the determined focal size of the X-rays. Further provided with a determination unit for determining the focal size for each view during one rotation by the rotation unit based on the image information of the subject.
The X-ray CT apparatus according to claim 3, wherein the control unit shoots while irradiating X-rays with a focal size determined for each view. The X-ray source has a plurality of filaments having different focal sizes, and the X-ray source has a plurality of filaments having different focal sizes.
The X-ray CT apparatus according to any one of claims 1 to 6, wherein the control unit controls to change the focal size in one filament selected from the plurality of filaments. A display control unit that estimates changes in the amount of heat in the X-ray source and displays information based on the estimation results on the display unit when the area to be imaged of the subject is imaged while irradiating X-rays at the focal size. The X-ray CT apparatus according to any one of claims 1 to 7, further comprising. The X-ray CT apparatus according to claim 8, wherein the display control unit specifies a range that can be imaged by one X-ray irradiation based on the estimation result, and displays the specified range on the display unit. Based on the estimation result, the display control unit determines whether or not the imaging range including the imaging target portion can be captured by one X-ray irradiation, and determines that the imaging range cannot be captured by one X-ray irradiation. In this case, by changing the imaging conditions including the focal size, it is further determined whether or not the imaging range including the imaging target portion can be photographed with one X-ray irradiation, and the imaging can be performed with one X-ray irradiation. The X-ray CT apparatus according to claim 8, wherein when it is determined, the changed imaging condition is displayed on the display unit. When the display control unit determines whether or not the imaging range including the imaging target portion can be captured by one X-ray irradiation based on the estimation result, and determines that the imaging range can be captured by one X-ray irradiation. Further, it is determined whether or not the focal size can be reduced, and when it is determined that the focal size can be reduced, the information on the changed focal size is displayed on the display unit. Item 8. The X-ray CT apparatus according to Item 8.

Images