JP5690506B2 - X-ray CT apparatus and control program - Google Patents

Description

The present disclosure relates to an X-ray CT apparatus that captures a medical image using X-rays and a control program .

  An X-ray CT (Computed Tomography) apparatus irradiates a subject with X-rays from various angles, detects X-rays transmitted through the subject, and generates an X-ray CT image of the subject. A tomographic image or a three-dimensional volume image is generated by the X-ray CT apparatus by rotating an X-ray tube and an X-ray detector attached to the inside of an apparatus called a gantry while placing an object placed on the opening of the gantry. It is performed by irradiating X-rays.

  When performing such a scan, a technique for injecting a contrast medium into a subject and highlighting a target portion in the subject has been put into practical use. In order to image a contrast agent that has reached the target region by generating a three-dimensional volume image within the set range (hereinafter simply referred to as a main scan), the timing at which the contrast agent reaches the target region and the main image It is necessary to match the scan start timing. Therefore, the X-ray CT apparatus performs a scan called pre-scan to control the start timing of the main scan. As an example of pre-scanning, one slice of an axial image in the vicinity of the target region is taken and the contrast agent reflected in the image is detected. If a certain amount or more of the contrast agent is reflected, it is determined that the contrast agent has reached the target region. An X-ray CT apparatus that captures a three-dimensional image of a target part is disclosed (for example, see Patent Document 1).

JP 2003-310597 A

  In Patent Document 1 described above, as a pre-scan, an axial image for one slice is taken after injection of a contrast medium. Then, it is determined that the contrast agent has reached the target region based on the fact that a certain amount or more of the contrast agent has been reflected in the region of interest in the axial image (hereinafter simply referred to as ROI: Region Of Interest). However, the contrast medium moving speed in the subject is not always constant, and the contrast medium moving speed at the position where the axial image is taken may be significantly different from that around the target region. In such a case, it is difficult to determine from the single axial image whether or not the contrast agent has reached the entire target region.

  In order to solve this problem, in the conventional X-ray CT apparatus, a method of increasing the injection amount of the contrast agent, or an ROI is reset in a region where the contrast agent arrival is expected to be particularly slow in the axial image. A method for determining the arrival of a contrast medium by using the method is used. However, there is a problem that the increase in the amount of contrast medium injected increases the physical burden on the subject, and the change in the position of the ROI is based on the experience and prediction of the operator, so that the scan start timing becomes uncertain.

Therefore, the X-ray CT apparatus of the present disclosure provides an X-ray CT apparatus and a control program that can more easily control the scan start timing by detecting a contrast agent using a plurality of axial images. With the goal.

In order to solve the above-described problems, an X-ray CT apparatus according to an embodiment includes an X-ray tube that irradiates X-rays, and an X-ray detector that is disposed so as to face the X-ray tube. in X-ray CT apparatus to perform photographing, the X-ray CT apparatus embodiment, X in at different positions in the body axis direction, and the imaging position setting means for setting a plurality of photographing positions spaced previous SL plurality of photographing positions A first imaging unit that performs a first scan for imaging a line CT image, a second imaging unit that performs a second scan for imaging an X-ray CT image in a predetermined imaging range, and the first scan. Control means for starting the second scan when each CT value exceeds a threshold based on the CT values included in each of the plurality of X-ray CT images taken at the plurality of imaging positions. Have.

1 is a block diagram showing a configuration of an X-ray CT apparatus according to an embodiment of the present disclosure. The figure which shows the structure of the collimator which concerns on the embodiment of this indication. The figure which shows a mode that the X-ray irradiation range changes with the movement of the collimator which concerns on the embodiment of this indication. The figure which shows a mode that an X-ray irradiation range changes with another movement of the collimator which concerns on the embodiment of this indication. The figure which shows the positional relationship of the collimator at the time of scano image imaging | photography concerning the embodiment of this indication. The figure which shows the positional relationship of the collimator at the time of the main scan which concerns on the embodiment of this indication. The figure which shows another structure of the collimator which concerns on the embodiment of this indication. Sectional drawing which shows the structure of the rotary body which concerns on the embodiment of this indication. The figure which shows a mode that a collimator moves for the scanogram imaging which concerns on the embodiment of this indication. The figure which shows the image | photographed scano image which concerns on the embodiment of this indication. The figure which shows a mode that a collimator moves for the main scan which concerns on the embodiment of this indication. FIG. 6 is a diagram illustrating a captured prescan image according to an embodiment of the present disclosure. The figure which shows the setting screen of ROI which concerns on the embodiment of this indication. The figure which shows a mode that a collimator moves for the prescan which concerns on the embodiment of this indication. FIG. 6 is a diagram showing a scan start timing control screen according to an embodiment of the present disclosure. The figure which shows a mode that a collimator moves based on the instruction | indication of the pre-scan image imaging position which concerns on the embodiment of this indication. The figure which shows a mode that a collimator moves based on the instruction | indication of another prescan image imaging position which concerns on the embodiment of this indication. 6 is a flowchart showing scan start timing control processing according to an embodiment of the present disclosure.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 is a block diagram showing an internal configuration of an X-ray CT apparatus 1 according to the present invention.

  In an embodiment described later, an operation for capturing a three-dimensional volume image in a predetermined range is simply referred to as a main scan. Further, an axial image (image taken in the xy plane direction in FIG. 1) used for controlling the start timing of the main scan is simply referred to as a pre-scan image. In addition, a pre-scan image taken in a state in which a contrast medium is injected into a subject, and a scan performed to control the main scan start timing is simply referred to as a pre-scan. Further, an X-ray image (image taken in the direction of the yz plane in FIG. 1) used for alignment between the subject and the X-ray tube 301 and the X-ray detector 302 is simply referred to as a scanogram.

(Configuration of X-ray CT apparatus 1)
The control unit 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit 100 includes a scan control unit 102, a reconstruction processing unit 103, an image processing unit 104, a display unit 106, a storage unit 107, and an input unit 108. The control unit 100 performs overall control of the X-ray CT apparatus 1 by processing signals supplied from the respective units and generating various control signals and supplying them to the respective units.

  The scan control unit 102 reads scan parameters that are input from the input unit 108 or read from the storage unit 107 when performing X-ray imaging. The scan control unit 102 outputs to the X-ray tube control unit 201 an X-ray beam irradiation signal for irradiating the X-ray tube 301 with X-rays based on the scan parameters. Further, the scan control unit 102 controls the gantry drive signal for moving the first collimator 401 (a) (b), the second collimator 402 (a) (b), and the third collimator 430 based on the scan parameter. To the unit 202. The scan control unit 102 outputs a gantry drive signal for rotating the rotator 300 to the gantry drive control unit 202 when an X-ray CT image of the subject P is captured by performing a main scan or a pre-scan described later. . Further, the scan control unit 103 outputs a top plate drive signal for moving the top plate 500 to the top plate drive control unit 203 based on the scan parameters.

  The reconstruction processing unit 103 generates a tomographic image of the subject P based on an X-ray detection signal output when the X-ray detector 302 detects an X-ray. When an X-ray CT image of the subject P is captured by performing a main scan, a pre-scan, etc., the reconstruction processing unit 103 is set for each rotation angle of the X-ray tube 301 and the X-ray detector 302 based on the back projection method. Back projection processing is performed on each of the obtained X-ray detection signals to generate tomographic image data. Then, when the reconstruction processing unit 103 generates the tomographic image data, it outputs this to the image processing unit 104. The X-ray detector 302 described later is configured by arranging a plurality of rows of X-ray detection elements for detecting incident X-rays along the channel direction (y direction in FIG. 1). In the main scan and pre-scan, the X-rays are transferred to a plurality of X-ray detection element arrays based on the operations of first collimators 401 (a) and (b) and second collimators 402 (a) and (b) described later. Will be incident. The reconstruction processing unit 103 receives the X-ray detection signal output from each column of the X-ray detection elements, and generates tomographic image data for each column.

  Based on the instruction input from the input unit 108, the image processing unit 104 performs tomographic image data of an arbitrary cross section or rendering processing on the tomographic image data output from the reconstruction processing unit 103 by a known method. Image data such as three-dimensional image data is generated. Further, the image processing unit 104 generates image data of a scanogram of the subject P based on the X-ray detection signal output from the X-ray detector 302. When the image processing unit 104 converts these image data, the image processing unit 104 outputs the converted image data to the display unit 106 or the storage unit 107.

  The display unit 106 includes, for example, a liquid crystal display, and displays image data output from the image processing unit 104, an operation screen for operating the X-ray CT apparatus 1, scan parameters input by the input unit 108, and the like. . In addition, the display unit 106 displays an operation screen for setting a shooting position of a prescan image, which will be described later.

  The storage unit 107 is configured by combining a storage medium such as a ROM, a RAM, a flash memory that is an electrically rewritable and erasable nonvolatile memory, and an HDD (Hard Disc Drive). The storage unit 107 stores the image data output from the image processing unit 104 and stores various applications executed by the CPU of the control unit 100.

  The input unit 108 includes, for example, an input device such as a touch panel display, mechanical buttons, and a mouse, and receives an input made by the user of the X-ray CT apparatus 1 to the input unit 108. When receiving an input such as a scan parameter instruction, a scan start / stop instruction, or a bed movement instruction given by the user, the input unit 108 outputs an input signal corresponding to the instruction given by the user. The control unit 100 executes various processes according to the input signal output from the input unit 108.

  The rotating body 300 is a cylindrical device built in the gantry 3. The rotating body 300 holds an X-ray tube 301, first collimators 401 (a) and (b), second collimators 402 (a) and (b), a third collimator 430, an X-ray detector 302, and the like. A rotating motor is attached to the rotator 300, and the rotator is driven in response to a gantry drive instruction signal output from the gantry drive control unit 202. The rotating body performs a rotating motion around the body axis of the subject P according to the driving of the rotating motor. As the rotator 300 rotates, the X-ray tube 301, the first collimators 401 (a) and (b), the second collimators 402 (a) and (b), the third collimator 430, and the X-rays that the rotator 300 holds. The detector 302 also performs a rotational motion around the body axis of the subject P.

  The X-ray tube control unit 201 receives the X-ray beam irradiation signal output from the scan control unit 102 and applies a voltage for irradiating the X-ray tube 301 with X-rays. This voltage application is performed based on parameters such as tube voltage, tube current, and X-ray pulse width specified by the X-ray beam irradiation signal.

  The X-ray tube 301 receives the voltage applied from the X-ray tube control unit 201 and irradiates the X-ray detector 302 with X-rays. At this time, the X-ray tube 301 irradiates X-rays having a shape spreading in a fan shape in the column direction so that X-rays enter each column of the X-ray detector 302 configured to have a plurality of columns.

  The X-ray detector 302 detects the X-rays emitted from the X-ray tube 301 and outputs this to the reconstruction processing unit 103 as an X-ray detection signal. This X-ray detector 302 arranges X-ray detection elements that detect an incident X-ray dose and generate an electric signal in a plurality of columns along the channel direction (y direction in FIG. 1), thereby providing an X-ray detection element. Are arranged two-dimensionally. More specifically, the X-ray detector 302 performs X along the channel direction (y direction in FIG. 1) of the subject P or along the direction perpendicular to the body axis direction (z axis direction in FIG. 1). The X-ray detection elements are arranged in two dimensions by arranging the X-ray detection elements in a row direction (z-axis direction in FIG. 1). The Hereinafter, the direction in which the rows of X-ray detection elements are arranged (the z-axis direction in FIG. 1) is simply referred to as the row direction.

  The gantry drive control unit 202 receives the gantry drive signal output from the scan control unit 102, receives the first collimators 401 (a) and (b), the second collimators 402 (a) and (b), and a third collimator described later. 430 is moved and the rotating body 300 is rotated. These movements and rotations are controlled based on scan parameters such as a rotation speed and a scan range specified by the input unit 108.

  The first collimators 401 (a) and (b), the second collimators 402 (a) and (b), and the third collimator 430 are members made of a substance that shields X-rays such as lead and tungsten. Each collimator is provided so as to block an X-ray irradiation area irradiated by the X-ray tube 301. The gantry drive control unit 202 controls the X-ray irradiation region on the subject by moving each collimator to block a part of the X-rays.

  The first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) are provided so as to control the irradiation region in the body axis direction (z-axis direction in FIG. 1) of the irradiated X-rays. It is done. FIG. 2 shows configurations of the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b). The first collimators 401 (a) and (b) are configured as plate-like members and are provided between the X-ray tube 301 and the top plate 500. A motor (not shown) is attached to the first collimators 401 (a) and (b), and the motor moves the first collimators 401 (a) and (b) in the body axis direction in response to an instruction signal output from the gantry drive control unit 202. It is moved back and forth along (z-axis direction in FIG. 2). As the first collimators 401 (a) and (b) move, the area where X-rays are blocked changes, and as a result, the X-ray irradiation area on the subject in the body axis direction (z-axis direction in FIG. 2) changes. Will change.

  On the other hand, the second collimators 402 (a) and (b) are configured by joining, for example, fine plate-like members. A motor (not shown) is provided at each of the connecting portions of the plate-like members. The motor drives the plate member to move in the body axis direction (z-axis direction in FIG. 2). Thereby, each plate-like member constituting the second collimator 402 (a) (b) transitions between a state where it is extended in the body axis direction (z-axis direction in FIG. 2) and a state where it is folded. Will be. The second collimators 402 (a) and (b) change the expansion / contraction state of each plate-like member to change the region that blocks X-rays. Further, at the end of the second collimator 402 (a) (b) far from the X-ray tube 301, the entire second collimator 402 (a) (b) is oriented in the body axis direction (z-axis direction in FIG. 2). A motor to be moved is connected. When the entire second collimators 402 (a) and (b) move, the second collimators 402 (a) and (b) change the region where X-rays are blocked. That is, the second collimator 402 (a) (b) drives two of a mechanism that relatively expands and contracts each plate-like member and a mechanism that moves the entire second collimator 402 (a) (b). The X-ray irradiation area on the subject in the body axis direction (z-axis direction in FIG. 2) is controlled to be expanded or narrowed, for example, and divided into two or more spaced X-ray irradiation areas, or 1 Control is integrated into one X-ray irradiation area.

  The gantry drive control unit 202 combines the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) to change the region that blocks X-rays, thereby simultaneously capturing a plurality of pre-scan images. An X-ray irradiation region is formed for this purpose. FIG. 3 is a diagram showing a positional relationship between the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) when three pre-scan images are simultaneously captured. The second collimator 402 (a) (b) moves into the X-ray irradiation region in a state where the second collimator 402 (a) (b) is folded with respect to the body axis direction (z-axis direction in FIG. 3). (B) Divides the X-ray irradiation region. Further, the first collimators 401 (a) and (b) move so as to block the end of the X-ray irradiation region, thereby further narrowing the divided X-ray irradiation region. When the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) have the positional relationship shown in FIG. 3, for example, the X-rays emitted from the X-ray tube 301 are in the body axis direction. The beams 3001, 3002, and 3003 having narrower widths (in the z-axis direction in FIG. 3) are incident on the subject P. When the beams 3001, 3002, and 3003 pass through the subject P, they enter the X-ray detector 302, and the reconstruction processing unit 103 generates an axial image, that is, a pre-scan image for one slice, based on the transmission amount of each beam. Generate.

  FIG. 4 is a diagram illustrating a positional relationship between the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) when the photographing position of the pre-scan image is changed. For example, in FIG. 4, the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) are positioned so that the irradiation positions of the beam 3001 and the beam 3003 move in the + z direction in FIG. ing. In order to change the irradiation position of the beam, the gantry drive control unit 202 performs the body axis directions of the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) (the z-axis direction in FIG. 4). ) And the expansion / contraction state of the second collimators 402 (a) and (b) are changed. Specifically, in order to move the beam 3001 in the + z direction in FIG. 4, the gantry drive control unit 202 moves the first collimator 401 (a) in the + z direction in FIG. Accordingly, the gantry drive control unit 202 moves the second collimator 402 (a) in the + z direction in FIG. Thereby, the beam 3001 irradiated from the opening part of the 1st collimator 401 (a) and the 2nd collimator 402 (a) will move to the + z direction in FIG. Further, since the gantry drive control unit 202 moves the beam 3002 in the + z direction in FIG. 4, the gantry drive control unit 202 expands the second collimator 402 (a) and X-rays toward the + z direction in FIG. Stretch the area that will block. Along with this, the gantry drive control unit 202 folds the second collimator 402 (b) and shrinks the region that blocks X-rays toward the + z direction in FIG. Thereby, the beam 3002 irradiated from the opening part of the 2nd collimator 402 (a) and the 2nd collimator 402 (b) will move to the + z direction in FIG.

  FIG. 5 is a diagram showing the positional relationship between the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) when performing scanogram imaging. When performing scanogram imaging, the task control unit 202 forms the first collimator 401 (a) (b) and the second collimator 402 so as to form a narrow beam 3004 that is incident on a predetermined line of the X-ray detector 302. (A) Move (b). Specifically, the gantry control unit 202 brings the first collimators 401 (a) and (b) close to each other so as to shield only the X-rays, leaving only an opening for transmitting the beam 3004. As a result, the beam 3004 irradiated from the openings of the first collimators 401 (a) and (b) is incident on a predetermined line of the X-ray detector 302. In a state where the beam 3004 is irradiated, the top board drive control unit 203 moves the subject P by moving the top board 500 along the body axis direction (z-axis direction in FIG. 5). The image processing unit 104 generates a scanogram based on a change in the transmission amount of the beam 3004 output from the X-ray detector 302. In this embodiment, an example in which the second collimator 402 (a) (b) is compared outside the X-ray irradiation range is shown, but the second collimator 402 (a) (b) is replaced with the second collimator 402 (a) (b). a) (b) may be extended to shield X-rays so that only the opening remains.

  FIG. 6 is a diagram showing the positional relationship between the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) when performing the main scan. When performing the main scan, the gantry control unit 202 forms the first collimator 401 (a) (b) and the second collimator so as to form a beam 3000 that spreads in a fan shape with respect to the body axis direction (z-axis direction in FIG. 6). 402 (a) and (b) are moved. Specifically, the gantry control unit 202 moves the first collimators 401 (a) and (b) so as to block the end of the X-ray irradiation region. Accordingly, the gantry drive control unit 202 moves the second collimators 402 (a) and (b) to the outside of the X-ray irradiation region. As a result, the beam 3000 irradiated from the openings of the first collimators (a) and (b) spreads in a fan shape in the body axis direction (z-axis direction in FIG. 6) and enters the X-ray detector 302. The reconstruction processing unit 103 generates a three-dimensional image based on the transmission amount of the beam 3000.

  By the above operation, the first collimators 401 (a) and (b) and the second collimators 402 (a) and (b) are driven to form an X-ray irradiation region for simultaneously photographing a plurality of pre-scan images. It has been described that the second collimators 402 (a) and (b) are configured by joining plate-like members so as to be stretchable. However, the present embodiment is not limited to this configuration. For example, the second collimator 402 (a) (b) may be configured by a plate-like member as shown in FIG. Absent. By omitting the telescopic mechanism, the second collimator 402 (a) (b) can be configured more simply, and the motor for moving the second collimator 402 (a) (b) can be configured more compactly. Can do.

  The third collimator 430 is provided so as to control the spread of the irradiated X-ray with respect to the channel direction (arrow direction shown in FIG. 8). The channel direction is a direction in which the X-ray detection elements of the X-ray detector 302 are arranged or a direction in which the rotating body 300 rotates. FIG. 8 shows a cross-sectional view of the rotator 300 viewed from the xy plane and the configuration of the third collimator 430. The X-rays blocked by the third collimator 430 spread in a fan shape in the channel direction and enter the X-ray detector 302 as shown in FIG. A drive motor (not shown) is attached to the third collimator 430, and the third collimator 430 moves in the channel direction to change the region that blocks X-rays, thereby controlling the X-ray irradiation region on the subject.

  The top plate 500 is a plate-like member on which the subject P can be laid down. The top plate 500 is supported by the top plate drive unit 501, and a top plate drive unit 501 described later moves back and forth along the longitudinal direction of the top plate 500 or the body axis direction (z-axis direction in FIG. 1). .

  The top plate driving unit 501 is a device for moving the top plate 500, which is configured by a motor (not shown) or the like. The top plate driving unit 501 is configured by attaching a belt connected to a motor to the top plate 500, for example. The position of the top plate 500 moves in conjunction with the rotation of the motor of the top plate drive unit 501. The top board driving unit 501 receives the top board driving signal output from the scan control unit 102 and moves the top board 500. For example, when the X-ray CT apparatus 1 captures a main scan, a pre-scan image, or a scanogram, the top panel drive unit 501 uses a top panel to match the imaging position of the subject P with the X-ray irradiation range. 500 is moved into the opening of the gantry 3 and the height of the top 500 is changed so that the center of rotation of the rotating body 300 and the body axis of the subject P coincide with each other.

  With the above-described configuration, the X-ray CT apparatus 1 performs various operations such as a scanogram, a prescan image, a prescan, and a main scan with respect to the subject P. Hereinafter, the flow of imaging of the subject P performed by the X-ray CT apparatus 1 will be described.

(Scan process flow)
When imaging a specific part such as a tumor in the subject P, a contrast agent that highlights the specific part on the X-ray image is injected into the subject P. The X-ray CT apparatus 1 performs a main scan in accordance with the timing at which the contrast agent reaches a specific part, and captures a three-dimensional image of the specific part.

  Since this contrast agent moves through the blood vessel of the subject P, the moving speed of the contrast agent varies greatly depending on the blood flow velocity, the distribution of blood vessels, and the like. Therefore, in the X-ray CT apparatus 1 of the present disclosure, the movement of the contrast agent is detected by combining processing such as ROI setting and pre-scan, and the start timing of the main scan is controlled. Specifically, the X-ray CT apparatus 1 of the present disclosure starts the main scan by performing processing in the following order, and captures a three-dimensional image of a specific part of the subject P.

(1) Scanogram imaging (2) Non-contrast X-ray CT image imaging (3) Main scan start condition setting (4) Pre-scan (5) Main scan Below, when imaging the subject P, A process flow of the X-ray CT apparatus 1 will be described.

(1) Imaging of Scano Image As a pre-stage of imaging using a contrast agent, it is necessary to confirm the position of the predetermined part of the subject P before the main scan. In the X-ray CT apparatus 1 of the present disclosure, a scanogram of the subject P is captured to confirm the position of a predetermined portion, and the scan position of the pre-scan image and the main scan position are adjusted using the scanogram. In the present embodiment, the scanogram is a two-dimensional image photographed toward the yz plane in FIG. 9 so as to accommodate a predetermined part of the subject P.

  FIG. 9 is a diagram showing the positional relationship among the X-ray tube 301, the X-ray detector 302, the first collimator 401, and the second collimator 402 when a scanogram is taken. When taking a scanogram, the gantry drive controller 202 controls the first collimator 401 so that the beam 3004 emitted from the X-ray tube 301 enters a predetermined row of the X-ray detector 302. The top plate drive control unit 203 moves the top plate 500 along the body axis direction (z-axis direction in FIG. 9) in a state where the beam 3004 is incident on the X-ray detector 302. The image processing unit 104 receives the X-ray detection signal output from the X-ray detector 302 and generates the scanogram shown in FIG. 10 (hereinafter, the scanogram captured by the beam 3004 will be referred to as the scanogram 600). .

(2) Non-contrast X-ray CT image imaging When the X-ray CT apparatus 1 captures a scanogram 600, the operator sets a rough position of the main scan based on the captured scanogram 600, for example. When the position of the main scan is set, the X-ray CT apparatus 1 captures an X-ray CT image of the subject P. In the present embodiment, the pre-scan image was captured so as to contain the region in which the contrast agent moves in order to detect the contrast agent moving in the subject P during the process of “(4) pre-scan” described later. It is an axial image (two-dimensional image image | photographed toward xy plane in FIG. 12).

  X-ray CT imaging is performed by irradiating X-rays so as to hold the pre-scan image imaging position assumed from the scanogram 600 and generating a three-dimensional image of the subject P. In this embodiment, an example in which the prescan image capturing position is designated using the scanogram 600 will be described. However, the scan image 600 is extracted from a three-dimensional image of the subject P photographed at an arbitrary time instead of the scanogram 600. A prescan image photographing position to be described later may be designated using a coronal image of the subject P. FIG. 12 shows the positional relationship among the X-ray tube 301, the X-ray detector 302, the first collimator 401, and the second collimator 402 when performing X-ray CT imaging. However, the X-ray irradiation area may be narrowed by appropriately driving the first collimator 401 in accordance with the size of the imaging area. When performing X-ray CT image capturing, the gantry drive control unit 202 moves the second collimator 402 out of the X-ray irradiation area while bringing the first collimator 401 close to narrow the X-ray irradiation area. The gantry drive control unit 202 rotates the rotating body 300 so that the fan-shaped beam 300 is incident on the subject P from various angles. The reconstruction processing unit 103 generates a three-dimensional image of the subject P based on the X-ray detection signal output from the X-ray detector 103. When the beam drive control unit 202 finishes the irradiation of the beam 3000, the gantry 300 stops the rotation of the rotating body 300 and ends the X-ray CT image capturing.

  When a three-dimensional image of the subject P is photographed, the operator sets the photographing position of the pre-scan image based on the three-dimensional image. The pre-scan image is picked up from, for example, a plurality of axial images corresponding to different positions on the body axis (z-axis in FIG. 12), which are adopted as pre-scan images from the three-dimensional images taken. Is done. FIG. 12 shows pre-scan images 601, 602, and 603 selected from the three-dimensional image. In the example of FIG. 12, three axial images are selected as pre-scan images, and the pre-scan images are used for processing of “(3) main scan start condition setting” to be described later. Note that the X-ray CT image imaging method is not limited to the method described here, and may be an image captured by various methods such as a helical scan.

(3) Main scan start condition setting When the X-ray CT apparatus 1 captures the prescan images 600, 601, and 602, the operator sets the main scan start condition using the captured prescan images 600, 601, and 602. . The start of the main scan is triggered by the fact that the CT value in the predetermined area set for each pre-scan image exceeds a preset threshold value. Therefore, the main scan start condition is set by first setting an area for detecting a change in CT value called ROI (Region Of Interest) in each pre-scan image, and setting a threshold for starting the scan for each ROI. Done in In addition to setting a threshold value for starting the main scan, a threshold value for starting reproduction of an audio signal instructing the subject P to stop breathing, raising a hand, etc., and for stopping the transition to the main scan A threshold or the like may be set.

  FIG. 13 is a display example of a setting screen for setting an ROI and a threshold for each photographed prescan image. The setting screen is displayed on the display unit 106, and the operator operates the buttons and input items displayed on the setting screen using the input unit 108 to set the ROI and threshold value. In FIG. 13, as an example, the control unit 100 controls the main scan start timing using three ROIs, ROI1, ROI2, and ROI3, controls the audio reproduction timing using the audio ROI, and further, a fixed ROI described later. It is assumed that the control to stop the transition to the main scan is performed using.

  Hereinafter, each item displayed on the setting screen will be described.

  The ROI 703 is an area for detecting a change in CT value. For example, the ROI 703 is set on the pre-scan image 603, and the control unit 100 changes the size and position of the ROI region according to the input from the input unit.

  A button 811 is a button for changing a pre-scan image to be set for ROI. For example, in FIG. 13, the prescan image 603 is displayed. By operating the button 811, the control unit 100 switches the prescan image displayed on the display unit 106 between the prescan image 601 and the prescan image 602.

  The button 812 is a button for changing the ROI that is the target of changing the area and size. For example, in FIG. 13, ROI 3 is displayed on the pre-scan image 603 and displayed in an editable state. However, by operating a button 812, the control unit 100 displays the ROI displayed on the display unit 106 as ROI 1, ROI 2, audio Switch to ROI, fixed ROI, etc.

  A button 800 is a button for designating the number of ROIs used for controlling the main scan start timing. For example, when “3ROI” is selected as shown in FIG. 13, the control unit 100 controls the main scan start timing using three ROIs set in each prescan image.

  An item 801 is an item in which the CT value in the ROI in the pre-scan image taken in “(2) Pre-scan image shooting” is displayed.

  An item 802 is an item for displaying an SD (Standard Division: Standard Deviation) value in the ROI in the pre-scan image captured in “(2) Capture of pre-scan image”. The SD value is a value indicating the degree of variation of the pixel value, and is used as an index of the amount of noise included in the pixel.

  A button 803 is a button for instructing the control unit 100 to recalculate the CT value and the SD value in the set ROI.

  The button 821 is a button for causing the control unit 100 to perform a prescan designating a time interval in a process of “(4) prescan” described later.

  An item 822 is an item for inputting a prescan time interval.

  An item 823 is an item for setting a threshold for switching the pre-scan from intermittent to continuous. For example, when the pre-scan time interval is designated by the button 821 as shown in FIG. 13, in the process of “(4) pre-scan” described later, the pre-scan is performed with a time interval of 3.0 seconds. For example, when the CT value in ROI1 exceeds 50.00HU set in item 823 due to, for example, the contrast agent being reflected in ROI1, the operation is performed so that the pre-scan is continuously performed without a time interval. Change.

  The button 824 is a button for causing the control unit 100 to reproduce the sound when the CT value in the sound ROI exceeds a threshold value in the process of “(4) prescan” described later.

  An item 825 is an item for inputting a threshold value for reproducing sound in the process of “(4) prescan” described later.

  An item 831 is an item for inputting a threshold value for shifting to the main scan in the process of “(4) prescan” described later.

  The button 832 is a button for setting a condition for shifting from “(4) pre-scan” processing described later to the main scan. For example, when “AND” is designated for ROI1 and ROI2 by the button 832 as shown in FIG. 13, the CT value in ROI1 exceeds 90.00HU in the process of “(4) prescan” described later, and When the CT value in ROI2 exceeds 130.00HU, the control unit 100 shifts to the main scan. On the other hand, when “OR” is specified for ROI 3, the control unit 100 shifts to the main scan when ROI 1 and ROI 2 satisfy the above-described conditions or the CT value in ROI 3 exceeds 170.00 HU. .

  An item 833 is an item for inputting a threshold value for stopping the shift to the main scan in the process of “(4) prescan” described later. For example, when the fixed ROI threshold is specified as 250.00 ± 20 HU as shown in FIG. 13, if the CT value in the fixed ROI is outside the range of the threshold, it is specified in the above-described ROI1, ROI2, and ROI3. Even if the conditions for shifting to the main scan are satisfied, the control unit 100 does not shift to the main scan.

  By operating the buttons and items in the setting screen described above, the operator inputs conditions for shifting from pre-scan to main scan, such as ROI and threshold. When the X-ray CT apparatus 1 sets the main scan start condition, the X-ray CT apparatus 1 starts pre-scan for the subject P.

(4) Prescan When the X-ray CT apparatus 1 sets the main scan start condition, the X-ray CT apparatus 1 injects a contrast agent into the subject P and starts prescan. Pre-scanning is performed by continuously capturing pre-scan images with imaging positions set in the process of “(2) X-ray CT image imaging” and detecting a contrast agent appearing in each pre-scan image. . FIG. 14 is a diagram illustrating a positional relationship among the X-ray tube 301, the X-ray detector 302, the first collimator 401, and the second collimator 402 when a pre-scan image is captured. When pre-scanning is performed, the gantry drive control unit 202 brings the first collimator 401 close to narrow the X-ray irradiation area, and moves the second collimator 402 to divide the X-ray irradiation area. As a result, the X-rays emitted from the X-ray tube 301 are blocked by the first collimator 401 and the second collimator 402 and become narrow beams 3001, 3002, 3003 for taking an axial image for one slice. Is incident on the subject P. The gantry drive control unit 202 rotates the rotating body 300 so that the beams 3001, 3002, and 3003 are incident on the subject P from various angles. The reconstruction processing unit 103 generates each prescan image based on the X-ray detection signal output from the X-ray detector 103. The control unit 100 continuously displays the pre-scan image as a moving image by continuously performing X-ray irradiation by the X-ray tube 301, rotation of the rotating body 300, and generation of each pre-scan image by the reconstruction processing unit 103. The contrast agent reflected in each prescan image is detected in real time.

  The contrast agent reflected in each pre-scan image is detected by a change in the CT value in the ROI as described above. FIG. 15 is a display example of a detection screen for detecting a contrast agent displayed on the display unit 106 during the prescan. The operator operates the buttons and input items displayed on the detection screen using the input unit 108 to perform operations such as setting the ROI region, setting the shooting position of the prescan image, or changing the threshold value.

  Hereinafter, each item displayed on the detection screen will be described.

  ROIs 701, 702, and 703 are areas for detecting changes in CT values. Each ROI is displayed on the pre-scan images 601, 602, 603, for example.

  An item 901 is an item for displaying a CT value threshold value set in the process of “(3) setting of actual scan start condition”. The control unit 100 changes the threshold according to the input from the input unit 108.

  An item 902 is an item for displaying a CT value in a captured prescan image. As described above, since the pre-scan image is continuously taken, the value in the item 901 varies with the movement of the contrast agent and the movement of the subject P. Further, when the value displayed in the item 902 exceeds the threshold range displayed in the item 901, the corresponding processing is performed by the control unit 100. Specifically, the corresponding processing is that when the threshold set for ROI1, ROI2, and ROI3 is exceeded, the start of the main scan exceeds the threshold set for the voice ROI. When the reproduction exceeds the threshold set for the fixed ROI, the control unit 100 performs a process of stopping the subsequent to the main scan.

  A button 905 is a button for instructing the control unit 100 to shift to the main scan. When this button is operated, the control unit 100 shifts to the main scan regardless of threshold processing using ROI1, ROI2, ROI3, fixed ROI, or the like.

  The button 911 is a button for designating an ROI to be controlled by a button 912 or a button 913 described later. For example, since ROI3 is selected in FIG. 15, control by a button 912 and a button 913 described later is performed on ROI3.

  The button 912 is a button for moving the position of the ROI. By operating the button 912, the control unit 100 moves the position of the ROI in the direction indicated by the input button.

  The button 913 is a button for moving the shooting position of the prescan image. The button 913 is displayed by being partially superimposed on the scanogram 600 indicating the shooting position of the prescan image. In addition, at a location where a pre-scan image is currently captured, the button is highlighted by a method such as reversing the brightness of the button. By operating the button 913, the gantry drive control unit 202 moves the first collimator 401 and the second collimator 402 to move the photographing position of the pre-scan image.

  FIGS. 16A and 16B and FIGS. 17A and 17B are diagrams showing the operation state of the button 913 and the positional relationship between the beams 3001, 3002, and 3003. In FIGS. 16A and 16B, as an example, it is assumed that the prescan image 601 is taken at a position corresponding to “Slice2” in the scanogram 600, and ROI1 is set in the prescan image 601. Similarly, the pre-scan image 602 is taken at a position corresponding to “Slice 5” in the scanogram 600, ROI2 is set in the pre-scan image 602, and the pre-scan image 603 corresponds to “Slice 7” in the scan image 600. It is assumed that ROI3 is set in the pre-scan image 603, which is shot at the position. In addition, it is assumed that the button 911 displays ROI3, and the movement of the shooting position of the prescan image by the button 913 is performed on the prescan image 603 on which the ROI3 is displayed.

  16 and 17, the configuration of the first collimator and the second collimator is simplified for convenience of drawing. In FIGS. 16 and 17, 10 X-ray detection elements of the X-ray detector 302 are arranged in the body axis direction (z-axis direction in FIG. 16B) for convenience of drawing, and 10 positions are pre-set. It is described so that a scanned image can be acquired. However, the number of X-ray detection elements and the imaging position of the prescan image are not limited to this, and may be appropriately adjusted. In FIG. 16B, beams 3001, 3002, and 3003 are incident on the second, fifth, and seventh X-ray detection elements as viewed from the + z direction in FIG. 16B, and generate prescan images. Correspondingly, the display unit 106 indicates the shooting position of the pre-scan image by inverting “Slice 2”, “Slice 5”, and “Slice 7” of the button 913 in FIG. Here, the case where the operator operates the cursor 999 or the like and operates the button 913 displayed as “Slice 8” will be described. When the button 913 displaying “Slice 8” is operated, the display on the display unit 106 changes to the state shown in FIG. 17A, and the button displaying “Slice 8” is highlighted instead of “Slice 7”. Display. At the same time, the gantry drive control unit 202 drives the first collimator 401 and the second collimator 402 to move the irradiation position of the beam 3001 in the −z direction in FIG. 17B as shown in FIG. Move.

  When the shooting position of the pre-scan image 603 is moved, it is necessary to newly set ROI3 and a threshold corresponding to ROI3. However, in order to easily perform this setting, the control unit 100 changes the shooting position. An operation of taking over the position and threshold value of the ROI set for “Slice 7” at the time to “Slice 8” is performed.

  Using the above detection screen, the operator detects the contrast agent reflected in each pre-scan image, and controls the transition to the main scan based on the preset ROI and threshold. By detecting the contrast agent using multiple pre-scan images at different positions on the subject, the movement of the contrast agent can be captured compared to the case where the contrast agent is detected using a single pre-scan image. It becomes easy. Therefore, it is possible to more reliably detect that the contrast medium has reached the predetermined site and appropriately control the start timing of the main scan.

  Further, by using the detection screen, it is possible to change the position of the ROI, the threshold value, and the shooting position of the prescan image. By changing these conditions during pre-scanning, the operator can change to conditions more suitable for detecting the movement of the contrast agent while observing the state of the contrast agent appearing in the pre-scan image. .

  Further, the beams 3001, 3002, and 3003 used for capturing the pre-scan image are controlled by the first collimator 401 and the second collimator 402 so as to become narrow beams. By controlling each beam to be a narrow beam, unnecessary exposure to the subject P during the prescan can be avoided.

(5) Main scan When the main scan start condition is satisfied or the button 905 is operated during the above-described pre-scan, the control unit 100 shifts to the main scan. The main scan is performed by irradiating X-rays so as to accommodate a predetermined part of the subject P and generating a three-dimensional image including the predetermined part. The positional relationship among the X-ray tube 301, the X-ray detector 302, the first collimator 401, and the second collimator 402 when performing the main scan is the same as that shown in FIG. However, the X-ray irradiation area may be narrowed by appropriately driving the first collimator 401 in accordance with the size of a predetermined part to be imaged. When performing the main scan, the gantry drive control unit 202 brings the first collimator 401 close to narrow the X-ray irradiation area, and moves the second collimator 402 out of the X-ray irradiation area. The gantry drive control unit 202 rotates the rotating body 300 so that the fan-shaped beam 300 is incident on the subject P from various angles. The reconstruction processing unit 103 generates a three-dimensional image of a predetermined part based on the X-ray detection signal output from the X-ray detector 103.

  In addition, when the photographing position of each pre-scan image and the position of the predetermined part are separated, the top panel drive control unit 203 moves the top panel 500 with the start of the main scan, and the predetermined part is moved to the main scan. Control to move to the photographing position may be performed.

(Scan process flowchart)
FIG. 18 is a flowchart showing the flow of each process described in (1) to (5) above. Hereinafter, the flow of the scanning process will be described with reference to FIG.

  First, when the control unit 100 starts a scanning process (step 1000), the control unit 100 drives the gantry driving unit 202 to separate the first collimator 401 and the second collimator. Further, the control unit 100 drives the X-ray tube control unit 201 to irradiate X-rays from the X-ray tube 301 and takes a scanogram of the subject P placed on the top 500 (step 1001).

  When a scanogram of the subject P is captured, the control unit 100 drives the gantry driving unit 202 to rotate the rotating body 300 and drives the X-ray tube control unit 201 to irradiate the X-ray tube 301 with X-rays. Then, an X-ray CT image of the subject P is taken (step 1002).

  When the X-ray CT image of the subject P is captured, the operator is prompted to set the imaging position of the pre-scan image (step 1003).

  When the shooting position of the pre-scan image is set, the control unit 100 displays an axial image corresponding to the shooting position and a setting screen on the display unit 106, and prompts the operator to set the main scan start condition (step 1004). . The main scan start condition includes the position of the ROI in the pre-scan image, the threshold value of the CT value for starting the main scan, and the like.

  When the main scan start condition is set, a contrast medium is injected into the subject P (step 1005).

  When the contrast agent is injected into the subject P, the control unit 100 drives the X-ray tube control unit 201 to irradiate the X-ray from the X-ray tube 301 and rotate the rotating body 300 to Pre-scanning is performed (step 1006).

  When the pre-scan is started, the control unit 100 waits for an instruction to change the pre-scan image shooting position from the input unit 108 (step 1007). When there is an instruction to change the prescan image shooting position (“Yes” in step 1007), the control unit 100 drives the gantry drive control unit 202 to move the first collimator 401 and the second collimator 402, and The shooting position of the scanned image is changed (step 1008). When the control unit 100 changes the shooting position of the prescan image, the control unit 100 returns to step 1005 and continues the prescan.

  When the control unit 100 does not receive an instruction to change the prescan image shooting position (“No” in step 1007), the control unit 100 refers to the CT value in the ROI set for each prescan image, It is determined whether or not the CT value satisfies the main scan start condition (step 1009).

  When the control unit 100 determines that the main scan start condition is not satisfied (“No” in step 1009), the control unit 100 returns to step 1006 to continue the pre-scan and waits for the CT value to change. On the other hand, when the control unit 100 determines that the main scan start condition is satisfied, or determines that the main scan start instruction is received from the button 905 (“Yes” in step 1009), the control unit 100 drives the gantry drive control unit 202. Then, the first collimator 401 is separated, and the second collimator 402 is moved out of the X-ray irradiation range to perform the main scan (step 1010). When the main scan is completed, the control unit 100 ends the process (step 1011).

  With the above processing, the X-ray CT apparatus 1 of the present disclosure detects the movement of the contrast agent using a plurality of pre-scan images, and controls the main scan start timing. By detecting the contrast medium using a plurality of pre-scan images at positions separated on the subject P, the state of the moving contrast medium can be detected reliably, and the main scan is started at a more appropriate timing. be able to.

  In addition, the X-ray CT apparatus 1 of the present disclosure can perform the above processing so that the narrow beams 3000, 3001, and 3002 can be obtained so that a pre-scan image for one slice can be obtained during pre-scan imaging. And the second collimator 402 is moved. As a result, the collimator shields X-rays that are irradiated outside the imaging range of the prescan image during prescan. Therefore, unnecessary exposure to the subject P during the prescan can be prevented.

  Further, the X-ray CT apparatus 1 of the present disclosure changes the imaging position of the pre-scan image during the pre-scan by the above processing. By changing the imaging position of the prescan image during the prescan, the imaging position can be moved to a position more suitable for capturing the movement of the contrast agent according to the movement of the contrast agent during the prescan.

  Further, through the above processing, the X-ray CT apparatus 1 of the present disclosure displays the button 913 on the scanogram, and changes the imaging position of the pre-scan image using the button 913. By instructing the imaging position of the pre-scan image using the scanogram, it is possible to more easily grasp the position on the subject P where the imaging position of the pre-scan image is located.

  In addition, this invention is not limited to what was disclosed by the said embodiment, A various invention can be formed with a proper combination of the some component currently disclosed by the said embodiment. For example, in the present embodiment, as described in step 1001 of FIG. 18, it is described that scanogram imaging is performed before X-ray CT image imaging. However, the configuration of the present disclosure is not limited to this, and for example, scanning of a scanogram may be omitted.

  In the present embodiment, an example in which pre-scanning is performed using three pre-scan images has been described. However, the number of prescan images is not limited to this, and a plurality of second collimators 402 may be added to increase the number of prescan images.

Further, for example, some constituent elements may be deleted from all the constituent elements shown in the embodiments, or constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 X-ray CT apparatus 3 Gantry 100 Control part 102 Scan control part 103 Reconstruction process part 104 Image processing part 106 Display part 107 Storage part 108 Input part 201 X-ray tube control part 202 Base drive control part 203 Top-plate drive control part 300 Rotating body 301 X-ray tube 302 X-ray detector 401 First collimator 402 Second collimator 430 Third collimator 500 Top panel 501 Top panel drive controller

Claims (8)

An X-ray CT apparatus that includes an X-ray tube that irradiates X-rays and an X-ray detector that is disposed opposite to the X-ray tube and that captures an X-ray CT image. Imaging position setting means for setting a plurality of spaced imaging positions; first imaging means for performing a first scan for imaging X-ray CT images at the plurality of imaging positions; and X-rays in a predetermined imaging range A second imaging means for performing a second scan for imaging a CT image , and a CT value included in each of the X-ray CT images at the plurality of imaging positions captured by the first scan ; An X-ray CT apparatus comprising: a control unit that starts the second scan when a CT value exceeds a threshold value . The X-ray CT apparatus according to claim 1, further comprising: a collimator that blocks a part of the X-ray based on the plurality of imaging positions and divides the X-ray irradiation area into a plurality of separated areas. The X-ray CT apparatus according to claim 2 , wherein the collimator includes a first collimator that blocks an end of the X-ray irradiation range, and a second collimator that divides the X-ray irradiation range. Further comprising an input hand stage for inputting a plurality of photographing positions, the first imaging means, during recording of the X-ray CT images of the plurality of photographing positions, the imaging based on the input of the input means X-ray CT apparatus according to any one of claims 1 to 3 to change the position. A third imaging unit that generates an X-ray image based on the X-rays detected by the X-ray detector; and an operation that indicates the plurality of imaging positions on the X-ray image generated by the third imaging unit. The X-ray CT apparatus according to claim 4 , further comprising display means for displaying a screen, wherein the input of the imaging position by the input means is performed based on the operation screen. Based on the comparison condition that is associated with each X-ray CT images taken by the first imaging means, further comparison means to compare the comparison condition photographed with X-ray CT image by the first imaging means The control means starts the second scan based on the comparison result of the comparison means, and the first imaging means applies to the X-ray CT image whose imaging position has been changed. , X-rays CT apparatus according to any one of claims 1 to 5 relate the comparison condition of X-ray CT images before change. The X-ray CT apparatus according to claim 1, wherein the threshold is set for each of the plurality of imaging positions. An X-ray CT apparatus for taking an X-ray CT image, comprising an X-ray tube for irradiating X-rays and an X-ray detector arranged opposite to the X-ray tube; Imaging position setting means for setting a plurality of spaced imaging positions at different positions, first imaging means for performing a first scan for imaging X-ray CT images at the plurality of imaging positions, X in a predetermined imaging range A second imaging means for performing a second scan for imaging a line CT image , based on CT values included in each of the X-ray CT images at the plurality of imaging positions, which are imaged by the first scan , A control program that functions as control means for starting the second scan when a CT value exceeds a threshold value .

Images