JP2011036427A - X-ray ct scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To radiate X-rays from appropriate directions. <P>SOLUTION: The X-ray CT scanner 100 acquires electrocardiographic signals of a subject P. The X-ray CT scanner 100 acquires the position information of an X-ray tube 12 on a circular path centered on the subject P. Subsequently the X-ray CT scanner 100 decides whether or not the position of the X-ray tube 12 shown by the position information indicates the position where photographing can be started and whether or not the electrocardiographic signals indicate the phase where photographing can be started. When deciding that the position of the X-ray tube 12 indicates the position where photographing can be started and that the electrocardiographic signals indicates the phase where photographing can be started, the X-ray CT scanner 100 performs control to make the X-ray tube 12 start exposure to X-rays. After that, the X-ray CT scanner 100 performs control so as to perform exposure to X-rays in a prescribed section on the circular path. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray CT apparatus.

  As one of imaging methods using an X-ray CT (Computed Tomography) apparatus, there is a method of performing imaging in synchronization with a biological signal of a subject. For example, in a method of performing imaging in synchronization with an electrocardiographic signal of a subject (hereinafter referred to as electrocardiographic synchronous imaging), the X-ray CT apparatus is based on an electrocardiographic signal output from an electrocardiograph attached to the subject. Then, X-ray exposure is started so as to synchronize with an electrocardiographic phase suitable for imaging (for example, diastole, systole, etc.) (Patent Document 1, etc.).

  In addition, as one of imaging methods using an X-ray CT apparatus, there is a method of performing X-ray exposure only in a predetermined section in a circular orbit centered on a subject. For example, in a method called half reconstruction (or half scan or the like), X-ray exposure is performed only in a section of 180 degrees corresponding to half of the entire circular orbit. Since half reconstruction is an effective technique in terms of improving time resolution and reducing exposure dose, in recent years, half reconstruction is often combined with electrocardiographic synchronization imaging. Also in this case, the X-ray CT apparatus starts X-ray exposure so as to synchronize with the electrocardiographic phase based on the electrocardiographic signal.

JP 2009-148482 A

  However, in the above-described conventional technique, the position of the tube at the start of X-ray exposure is determined randomly following the electrocardiogram signal, and therefore X-rays are not always emitted from an appropriate direction. There was a problem.

  For example, it is known that the absorbed dose of X-rays in a subject varies depending on organs and tissues. For example, in the mammary gland, the absorbed dose is reduced by irradiating from the back direction rather than irradiating the subject from the front direction. Further, for example, in a hematopoietic organ, the absorbed dose is smaller when irradiation is performed from the side direction than when X-rays are irradiated from the front direction or the back direction of the subject. However, in the conventional technology, X-rays are not always irradiated from a direction with a large absorbed dose, and X-rays are not always irradiated from an appropriate direction.

  Further, for example, the image quality may be improved by irradiating from the front direction or the back direction rather than irradiating the X-ray from the side surface direction of the subject. However, in the conventional technology, X-rays are not always emitted from the direction in which the image quality is improved, and X-rays are not always emitted from an appropriate direction. In addition, for example, it is not possible to cope with a case where the X-ray irradiation direction is limited, such as when a metal is attached to the subject or when a free posture cannot be taken.

  Note that the above-described problem is not limited to the case of electrocardiographic synchronization imaging, and similarly, for example, a technique for performing imaging in synchronization with the breathing of a subject.

  The present invention has been made in view of the above, and an object thereof is to provide an X-ray CT apparatus capable of irradiating X-rays from an appropriate direction.

  In order to solve the above-described problems and achieve the object, the present invention according to claim 1 is a biological signal acquisition means for acquiring a biological signal of a subject, and a tube on a circular orbit centered on the subject. The position information acquisition means for acquiring the position information, the biological signal acquired by the biological signal acquisition means, and the position information acquired by the position information acquisition means are collated, and the tube indicated by the position information The position indicates a position where imaging can be started, and a determination unit for determining whether or not the biological signal indicates a phase where imaging can be started, and the position of the tube indicates the position where imaging can be started by the determination unit. And when it is determined that the biological signal indicates a phase at which imaging can be started, an exposure start control means for controlling to start X-ray exposure from the tube, and X by the exposure start control means Radiation exposure starts When, characterized in that a exposure control means for controlling to perform predetermined section X-ray irradiation on the circular path.

  According to the first aspect of the present invention, there is an effect that X-rays can be irradiated from an appropriate direction.

FIG. 1 is a block diagram illustrating the configuration of the X-ray CT apparatus according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration of the gantry driving unit. FIG. 3 is a diagram for explaining an electrocardiogram signal. FIG. 4 is a diagram for explaining the position information of the tube. FIG. 5 is a diagram for explaining the start timing of X-ray exposure. FIG. 6 is a flowchart illustrating a processing procedure performed by the gantry driving unit according to the first embodiment. FIG. 7 is a diagram for explaining the start timing of X-ray exposure. FIG. 8 is a block diagram illustrating the configuration of the gantry driving unit according to the third embodiment. FIG. 9 is a flowchart illustrating a processing procedure performed by the elapsed time determination unit and the rotation period adjustment unit. FIG. 10 is a flowchart illustrating a processing procedure performed by the rotation period adjustment unit. FIG. 11 is a diagram for explaining the start timing of X-ray exposure. FIG. 12 is a diagram for explaining a screen for accepting designation by the operator. FIG. 13 is a diagram for explaining application to segment reconstruction.

  Hereinafter, embodiments of the X-ray CT apparatus according to the present invention will be described in detail. In addition, this invention is not limited by the following examples.

[Configuration of X-ray CT Apparatus According to Embodiment 1]
First, the configuration of the X-ray CT apparatus according to the first embodiment will be described with reference to FIGS. FIG. 1 is a block diagram illustrating the configuration of the X-ray CT apparatus according to the first embodiment.

  As shown in FIG. 1, the X-ray CT apparatus 100 according to the first embodiment includes a gantry device 10, a couch device 20, and a console device 30. As will be described later, in the X-ray CT apparatus 100 according to the first embodiment, the gantry driving unit 16 included in the gantry apparatus 10 controls the start timing of the X-ray exposure.

  The gantry device 10 irradiates the subject P with X-rays, detects X-rays transmitted through the subject P, and outputs them to the console device 30. The gantry device 10 includes a high voltage generation unit 11, an X-ray tube 12, an X-ray detector 13, a data collection unit 14, a rotating frame 15, a gantry driving unit 16, and an electrocardiograph 17.

  The high voltage generator 11 supplies a high voltage to the X-ray tube 12. The X-ray tube 12 is a vacuum tube and generates X-rays by a high voltage supplied from the high voltage generator 11. The X-ray detector 13 detects X-rays that have passed through the subject P. The data collection unit 14 generates projection data using the X-rays detected by the X-ray detector 13. The rotating frame 15 is an annular frame that supports the X-ray tube 12 and the X-ray detector 13 so as to face each other with the subject P interposed therebetween, and rotates at high speed and continuously.

  The gantry driving unit 16 rotates the rotary frame 15 by driving the motor, and rotates the X-ray tube 12 and the X-ray detector 13 on a circular orbit around the subject P. The gantry driving unit 16 controls the start timing of the X-ray exposure. The gantry driving unit 16 will be described in detail later. The electrocardiograph 17 detects a weak current generated from the heart of the subject P via an electrode attached to the subject P, and outputs an electrocardiogram signal based on the detected current.

  The couch device 20 is a table on which the subject P to be imaged is placed, and includes a couchtop 21 and a couch driving unit 22. The top plate 21 is a plate on which the subject P is placed. The bed driving unit 22 moves the top plate 21 by driving a motor. Specifically, it moves in the direction toward the gantry device 10 (slice direction) and in the opposite direction, up and down direction, and left and right direction.

  The console device 30 accepts an operation of the X-ray CT apparatus 100 by the operator and reconstructs an image from the projection data collected by the gantry device 10. Specifically, the console device 30 includes an input device 31, a display device 32, a scan control unit 33, a preprocessing unit 34, a projection data storage unit 35, an image reconstruction processing unit 36, and an image data storage. Unit 37 and a system control unit 38.

  The input device 31 is a mouse, a keyboard, or the like, and receives an instruction input to the X-ray CT apparatus 100 from an operator. For example, the input device 31 accepts setting of imaging conditions, an instruction to start imaging, and the like.

  The display device 32 is a display such as an LCD (Liquid Crystal Display) and displays various types of information. For example, the display device 32 displays an image stored in the image data storage unit 37, a GUI (Graphical User Interface) for receiving an instruction from the operator, and the like.

  The system control unit 38 controls the X-ray CT apparatus 100 as a whole by controlling the gantry device 10, the couch device 20, and the console device 30. For example, the system control unit 38 controls the scan control unit 33 to collect projection data, and controls the image reconstruction processing unit 36 to reconstruct an image from the projection data. The system control unit 38 is, for example, an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or an electronic circuit such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit). is there.

  The scan control unit 33 controls the high voltage generation unit 11, the data collection unit 14, and the gantry driving unit 16 based on the imaging condition instructed from the system control unit 38. The scan control unit 33 controls the bed driving unit 22 under the control of the system control unit 38. The scan control unit 33 is, for example, an integrated circuit such as an ASIC or FPGA, or an electronic circuit such as a CPU or MPU.

  The pre-processing unit 34 performs pre-processing such as sensitivity correction on the projection data generated by the data collection unit 14 and stores it in the projection data storage unit 35. The preprocessing unit 34 is, for example, an integrated circuit such as an ASIC or FPGA, or an electronic circuit such as a CPU or MPU.

  The projection data storage unit 35 stores the projection data that has been preprocessed by the preprocessing unit 34. The projection data storage unit 35 is, for example, a semiconductor memory device such as a RAM (Random Access Memory), a ROM (Read Only Memory), or a flash memory, a hard disk, an optical disk, or the like.

  The image reconstruction processing unit 36 reconstructs an image from the projection data stored in the projection data storage unit 35 based on the reconstruction condition instructed by the system control unit 38, and stores the reconstructed image data as image data. Stored in the unit 37.

  The image data storage unit 37 stores the image data reconstructed by the image reconstruction processing unit 36. Note that the image data storage unit 37 is, for example, a semiconductor memory device such as a RAM, a ROM, or a flash memory, a hard disk, an optical disk, or the like.

  Subsequently, the gantry driving unit 16 will be described in detail with reference to FIGS. 2 is a block diagram showing the configuration of the gantry driving unit, FIG. 3 is a diagram for explaining an electrocardiogram signal, FIG. 4 is a diagram for explaining the position information of the tube, FIG. 5 is a diagram for explaining the start timing of X-ray exposure.

  As shown in FIG. 2, the gantry drive unit 16 includes an electrocardiogram signal acquisition unit 16a, a tube position information acquisition unit 16b, a determination unit 16c, and an exposure control unit 16d.

  The electrocardiogram signal acquisition unit 16a acquires an electrocardiogram signal of the subject P. Specifically, the electrocardiogram signal acquisition unit 16a acquires the electrocardiogram signal of the subject P output from the electrocardiograph 17, and sends the acquired electrocardiogram signal to the tube position information acquisition unit 16b. For example, the electrocardiogram signal acquisition unit 16a acquires an electrocardiogram signal as illustrated in FIG. Here, a frame surrounded by a shown in FIG. 3 indicates a range of an electrocardiographic phase suitable for imaging (for example, diastole, systole, etc.), and an arrow indicates a phase where imaging can be started.

  The tube position information acquisition unit 16b acquires position information of the X-ray tube 12 on a circular orbit centered on the subject P. Specifically, the tube position information acquisition unit 16b starts imaging by the operator, and when rotation of the rotating frame 15 is started, an encoder attached to a motor that rotates the rotating frame 15 reads the motor shaft. The position information of the X-ray tube 12 is acquired by acquiring the rotation angle information and the rotation speed information, and the acquired position information and the electrocardiogram signal sent from the electrocardiogram signal acquisition unit 16a are sent to the determination unit 16c. . For example, as shown in FIG. 4, the tube position information acquisition unit 16b acquires position information indicating a circular orbit centered on the subject P at 360 degrees clockwise with the front direction of the subject P being 0 degrees. To do.

  The determination unit 16c indicates whether or not the position of the X-ray tube 12 indicated by the position information of the X-ray tube 12 indicates a position at which imaging can be started, and whether the electrocardiographic signal of the subject P indicates a phase at which imaging can be started. Determine. Specifically, the determination unit 16c makes a determination using the electrocardiogram signal and position information sent from the tube position information acquisition unit 16b, and sends the determination result to the exposure control unit 16d. Since both the electrocardiogram signal and the position information are continuously acquired by the electrocardiogram signal acquisition unit 16a and the tube position information acquisition unit 16b, the determination by the determination unit 16c is also performed continuously. Become.

  As a position at which imaging of the X-ray tube 12 can be started, as shown in FIG. 5A, for example, a range of 90 degrees−20 degrees to 90 degrees + 20 degrees is set in advance. If imaging starts from this range, X-rays are emitted from the back surface of the subject P. Further, it is assumed that a phase indicated by an arrow in FIG. 5B is set in advance as a phase at which imaging of an electrocardiogram signal can be started. Then, the determination unit 16c determines that the position information acquired by the tube position information acquisition unit 16b is within the range shown in FIG. Whether or not the phase of the arrow shown in (B) of FIG. 5 is obtained is continuously determined every time such information is acquired.

  When the exposure control unit 16d determines that the position of the X-ray tube 12 indicated by the position information of the X-ray tube 12 indicates a position where imaging can be started, and the electrocardiogram signal indicates a phase where imaging can be started. The high voltage generator 11 is controlled to start the X-ray exposure from the X-ray tube 12. In addition, when the X-ray exposure is started, the exposure control unit 16d controls the high voltage generation unit 11 so as to perform a predetermined section X-ray exposure on the circular orbit.

  Specifically, when the determination result is sent from the determination unit 16c, the exposure control unit 16d indicates that the determination result indicates “the position of the X-ray tube 12 indicates a position where imaging can be started, and the electrocardiogram signal is It is determined whether or not it is a determination result of “indicating a phase where imaging can be started”. Then, the exposure control unit 16d determines that the X-ray is in the case of a determination result that “the position of the X-ray tube 12 indicates a position at which imaging can be started and the electrocardiogram signal indicates a phase at which imaging can be started”. The high voltage generator 11 is controlled to start the exposure. Further, when the X-ray exposure is started, the exposure control unit 16d determines whether or not the X-ray tube 12 has moved 180 degrees on the circular orbit from the position where the X-ray exposure is started, If it determines with having moved, the high voltage generation part 11 will be controlled so that X-ray exposure may be stopped. The determination as to whether or not the X-ray tube 12 has moved 180 degrees on the circular orbit can be made by, for example, acquiring position information from the tube position information acquisition unit 16b.

[Processing procedure by gantry driving unit in embodiment 1]
Next, a processing procedure by the gantry driving unit 16 in the first embodiment will be described with reference to FIG. FIG. 6 is a flowchart illustrating a processing procedure performed by the gantry driving unit according to the first embodiment. Note that the following processing procedure is executed from a state in which imaging has already been started by the operator and rotation of the rotary frame 15 has started, but X-ray exposure has not started.

  First, in the gantry driving unit 16, the electrocardiogram signal acquisition unit 16a acquires an electrocardiogram signal, and the tube position information acquisition unit 16b acquires the position information of the X-ray tube 12 (step S101).

  Next, the determination unit 16c determines whether the position of the X-ray tube 12 indicated by the position information indicates a position where imaging can be started, and whether the electrocardiogram signal indicates a phase where imaging can be started (step S102). ).

  Subsequently, the exposure control unit 16d determines that the determination result by the determination unit 16c is “the position of the X-ray tube 12 indicates a position where imaging can be started and the electrocardiogram signal indicates a phase where imaging can be started”. It is determined whether it is a result (step S103).

  Then, the exposure control unit 16d determines that “the position of the X-ray tube 12 indicates a position where imaging can be started and the electrocardiographic signal indicates a phase where imaging can be started” (step S103). (Yes), the high voltage generator 11 is controlled to start the X-ray exposure (step S104). In addition, since the electrocardiogram signal and the positional information of the X-ray tube 12 are continuously acquired and the determination by the determination unit 16c is also performed continuously, the determination in step S103 is also “the position of the X-ray tube 12 can start imaging. It is continuously performed until a determination result is obtained that indicates an accurate position and the electrocardiogram signal indicates a phase at which imaging can be started.

[Effect of Example 1]
As described above, the X-ray CT apparatus 100 according to the first embodiment acquires an electrocardiographic signal of the subject P. In addition, the X-ray CT apparatus 100 acquires position information of the X-ray tube 12 on a circular orbit centered on the subject P. Next, the X-ray CT apparatus 100 determines whether or not the position of the X-ray tube 12 indicated by the position information indicates a position where imaging can be started, and the electrocardiogram signal indicates a phase where imaging can be started. When the X-ray CT apparatus 100 determines that the position of the X-ray tube 12 indicates a position where imaging can be started and the electrocardiogram signal indicates a phase where imaging can start, X-ray exposure from the X-ray tube 12 is performed. Control to start. Thereafter, the X-ray CT apparatus 100 performs control so as to perform predetermined section X-ray exposure on the circular orbit.

  For this reason, according to the first embodiment, X-ray exposure is not started at random following the electrocardiogram signal, but is set at a preset “position where imaging can be started”. Began when there is. The preset “position at which imaging can be started” is set in consideration of absorbed dose, image quality, and the like, and is set for the purpose of irradiating X-rays from an appropriate direction. Therefore, according to the first embodiment, it is possible to irradiate X-rays from an appropriate direction, which is effective for imaging in which the X-ray irradiation direction affects the exposure dose and image quality.

  In the first embodiment, since a predetermined range (for example, a range of 90 ° −20 ° to 90 ° + 20 °) is set as the designation of “position where imaging can be started”, there is a degree of freedom and X-ray exposure is performed. It is easy to take the start timing of shooting. The wider the range, the easier it is to take the start timing.

  In the first embodiment, a case where a range of 90 degrees to 20 degrees to 90 degrees +20 degrees is set in advance as a position where the imaging of the X-ray tube 12 can be started is assumed, but the present invention is limited to this. It is not a thing. For example, when it is appropriate to irradiate from the back side of the subject P, and the posture of the subject P placed on the top plate 21 is sideways, 90 degrees −20 degrees to 90 degrees +20 degrees This range is not always appropriate.

  That is, in such a case, it is desirable to set a range centering on the position of 270 degrees shown in FIG. For this reason, for example, as shown in FIG. 7A, for example, a range of 180 degrees −20 degrees to 180 degrees +20 degrees is set in advance as a position where the imaging of the X-ray tube 12 can be started. Further, a phase indicated by an arrow in FIG. 7B is set in advance as a phase at which an electrocardiographic signal can be imaged. Then, the determination unit 16c indicates that the position information acquired by the tube position information acquisition unit 16b is within the range shown in FIG. 7A and the ECG signal acquired by the ECG signal acquisition unit 16a is a graph. Whether or not it is the position of the arrow shown in (B) of Fig. 7 is continuously determined every time such information is acquired. FIG. 7 is a diagram for explaining the start timing of X-ray exposure.

  Further, for example, when it is appropriate to irradiate from the back side of the subject P, when the posture of the subject P placed on the top 21 is prone, imaging of the X-ray tube 12 can be started. As the correct position, the range of 90 ° -20 ° to 90 ° + 20 ° and the range of 180 ° -20 ° to 180 ° + 20 ° are not appropriate.

  That is, in such a case, it is desirable to set a range centered on 0 degrees. For example, as a position where the imaging of the X-ray tube 12 can be started, it is desirable that a range of, for example, 360 ° −20 ° to 0 ° + 20 ° is set.

  In the first and second embodiments, the determination unit 16c indicates that the position of the X-ray tube 12 indicated by the position information indicates a position where imaging can be started, and the electrocardiogram signal indicates a phase where imaging can be started. The method by which the exposure control unit 16d starts imaging at the determined timing has been described. However, when the cycle of the heartbeat and the rotation cycle of the rotary frame 15 are synchronized, it is theoretically considered that the position where the imaging can be started permanently is not achieved. For example, this is the case when the heartbeat cycle is 75 bpm (0.8 sec cycle) and the rotation cycle of the rotating frame 15 is 150 rpm (0.4 sec cycle). Therefore, in Example 3, when the time until the X-ray exposure can be started exceeds a predetermined threshold value, the rotation cycle of the rotating frame 15 is finely adjusted.

  Specifically, the gantry driving unit 16 according to the third embodiment further includes an elapsed time determination unit 16e and a rotation period adjustment unit 16f as illustrated in FIG. FIG. 8 is a block diagram illustrating the configuration of the gantry driving unit according to the third embodiment. The elapsed time determination unit 16e and the rotation period adjustment unit 16f will be described with reference to FIGS. FIG. 9 is a flowchart illustrating a processing procedure performed by the elapsed time determination unit and the rotation cycle adjustment unit, and FIG. 10 is a flowchart illustrating a processing procedure performed by the rotation cycle adjustment unit.

  First, the elapsed time determination unit 16e determines whether or not X-ray exposure has been started (step S201). If it is determined that the X-ray exposure has not started (No in step S201), the elapsed time is determined in advance. It is determined whether or not the threshold is exceeded (step S202). If the elapsed time determination unit 16e determines that the threshold value has been exceeded (Yes in step S202), the determination result is sent to the rotation cycle adjustment unit 16f. Then, the rotation period adjustment unit 16f finely adjusts the rotation period of the rotation frame 15 (step S203). For example, the rotation cycle adjusting unit 16f delays the rotation cycle of the rotating frame 15 by 1 rpm.

  The fine adjustment of the rotation period of the rotating frame 15 may be performed before the start of imaging by the operator. For example, as shown in FIG. 10, before the start of imaging by the operator, the electrocardiogram signal acquisition unit 16a starts to acquire an electrocardiogram signal (step S301).

  Then, the rotation cycle adjustment unit 16f calculates the heartbeat cycle from the electrocardiogram signal acquired by the electrocardiogram signal acquisition unit 16a (step S302), and the calculated heartbeat cycle and the known rotation cycle of the rotation frame 15. Are collated (step S303).

  As a result of the collation, when the periods are the same or close to each other (Yes at Step S304), the rotation period adjustment unit 16f adjusts the rotation period of the rotation frame 15 (Step S305). In this way, it is determined in advance whether the period of the electrocardiogram signal and the rotation period of the X-ray tube 12 are the same or close to each other, and by adjusting the rotation period of the X-ray tube 12 in advance, The start timing of exposure can be made easier. In addition, you may make it obtain permission by an operator, before adjusting the rotation period of the X-ray tube 12 automatically.

  In addition, the present invention may be implemented in various different forms other than the above-described embodiments.

[Range of electrocardiographic phase]
In the above-described embodiment, for example, a range of 90 ° −20 ° to 90 ° + 20 ° is preset as a position where the imaging of the X-ray tube 12 can be started, and one point indicated by an arrow as a phase where an electrocardiographic signal can be imaged However, the present invention is not limited to this. For example, as shown in FIG. 11, not only the range where the imaging of the X-ray tube 12 can be started is designated by “range” (see FIG. 11A), but also the phase where the electrocardiographic signal can be imaged is “range”. (See FIG. 11B). Such designation makes it easier to synchronize the two. A certain point can be set as a position where the imaging of the X-ray tube 12 can be started. FIG. 11 is a diagram for explaining the start timing of X-ray exposure.

[Specify where to start imaging]
In the above-described embodiments, the position where the imaging of the X-ray tube 12 can be started and the phase where the electrocardiographic signal can be started are set in advance. However, the present invention is not limited to this. Each time an image is taken, designation by the operator may be accepted.

  For example, it is assumed that the X-ray CT apparatus 100 displays a GUI as shown in FIG. Then, for example, when the operator thinks that irradiation from the back direction of the subject P is appropriate, the operator clicks the back direction with the mouse on the screen displayed on the display device 32 ( In FIG. 12, the white arrow indicates the position clicked with the mouse).

  Then, for example, the system control unit 38 of the X-ray CT apparatus 100 subtracts 90 degrees from the clicked position (180 degrees), and gives a range of 20 degrees to the range of 90 degrees-20 degrees to 90 degrees. Backcount +20 degrees. Then, the calculation result by the system control unit 38 is sent to the gantry driving unit 16 via the scan control unit 33, and the gantry driving unit 16 is set as a position where the imaging of the X-ray tube 12 designated by the operator can be started. 90 degrees-20 degrees to 90 degrees + 20 degrees are stored and used for determination by the determination unit 16c.

  In addition, for example, an input of the irradiation direction “180 degrees” by the operator may be received, and 90 degrees−20 degrees to 90 degrees + 20 degrees may be calculated from this value. Further, for example, an “trajectory” input by the operator may be received (such as designating the trajectory of the irradiation range with a mouse), and a position where imaging can be started may be obtained from the received “trajectory”. Similarly, it is possible to accept designation by the operator for the phase at which imaging can be started. In addition, FIG. 12 is a figure for demonstrating the screen for designation | designated reception by an operator.

[Segment reconstruction]
In the above-described embodiments, description has been made assuming half reconstruction, but the present invention is not limited to this, and can be similarly applied to segment reconstruction, for example. FIG. 13 is a diagram for explaining application to segment reconstruction.

  Here, segment reconstruction is a technique for collecting and collecting projection data required for reconstruction over a predetermined number of heartbeats. For example, segment reconstruction divides the range required for half reconstruction into three segments, and collects projection data in the same phase corresponding to each segment from each of three heartbeats.

  In such a case, the X-ray CT apparatus 100 according to the present invention, for example, as shown in FIG. 13, sets the ranges of three segments little by little, and sets the positions where imaging can be started for each segment. specify. That is, three positions are designated as positions where imaging can be started.

  Then, the X-ray CT apparatus 100 collates the electrocardiogram signal with the position information, and the position of the X-ray tube 12 indicated by the position information is any one of the three positions designated as positions where imaging can be started. In addition, it is determined whether or not the electrocardiographic signal indicates a phase corresponding to a segment starting from that position and capable of starting imaging. When making such a determination, the X-ray CT apparatus 100 collects projection data at random in the order of segments with timing.

[Respiratory synchronization]
Further, in the above-described embodiments, the case of electrocardiogram synchronous imaging has been described as an example, but the present invention is not limited to this. For example, the present invention is similarly applied to a method of performing imaging in synchronization with the breathing of a subject. be able to.

DESCRIPTION OF SYMBOLS 100 X-ray CT apparatus 16 Base drive part 16a ECG signal acquisition part 16b Tube position information acquisition part 16c Judgment part 16d Exposure control part

Claims (7)

A biological signal acquisition means for acquiring a biological signal of the subject;
Position information acquisition means for acquiring position information of a tube on a circular orbit centered on the subject;
Whether the position of the tube indicated by the position information acquired by the position information acquisition means indicates a position where imaging can be started, and whether the biological signal acquired by the biological signal acquisition means indicates a phase where imaging can be started Determination means for determining whether or not
When the determination means determines that the position of the tube indicates a position where imaging can be started and the biological signal indicates a phase where imaging can start, X-ray exposure starts from the tube Exposure start control means to control to,
X-ray CT comprising: an exposure control means for controlling to perform a predetermined section X-ray exposure on the circular orbit when X-ray exposure is started by the exposure start control means apparatus. Position designation accepting means for accepting designation of a position where imaging can be started for a tube;
Phase designation accepting means for accepting designation of a phase at which imaging can be started for a biological signal,
The determining means indicates a position where the tube indicated by the position information acquired by the position information acquiring means indicates a position where the imaging can be started received by the position designation receiving means, and the biological signal acquiring means The X-ray CT apparatus according to claim 1, wherein it is determined whether or not the acquired biological signal indicates a phase at which imaging can be started received by the phase designation receiving unit.   The X-ray CT apparatus according to claim 2, wherein the position designation receiving unit receives a specified range as the position where the imaging can be started.   The X-ray CT apparatus according to claim 2, wherein the phase designation accepting unit accepts designation of a predetermined range as designation of a phase at which imaging can be started. The position designation accepting unit accepts designation of a center point of a predetermined section on the circular orbit as designation of a position where the imaging can be started,
The determination means obtains a position where the imaging can be started by back calculation from the center point received by the position designation reception means, and the position of the tube indicated by the position information acquired by the position information acquisition means is The X-ray CT apparatus according to claim 2, wherein it is determined whether or not a position where the imaging can be started is indicated. A period determination means for comparing the period of the biological signal acquired by the biological signal acquisition means with the rotation period of the tube, and determining whether both periods are in the same or close relationship;
6. The adjusting device according to claim 1, further comprising: an adjusting unit that adjusts a rotation cycle of the tube when the cycle determining unit determines that the two cycles are the same or in a close relationship. The X-ray CT apparatus according to any one of the above.   The X-ray CT apparatus according to claim 1, wherein the biological signal acquisition unit acquires an electrocardiographic signal of a subject as the biological signal.

Images