JP7039372B2 - X-ray CT device - Google Patents

Description

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

Generally, in an X-ray CT (Computed Tomography) device, a two-dimensional fluoroscopic image (hereinafter referred to as a scanno image) called a scanogram is taken as a positioning image before the CT imaging which is the main scan. Will be done.

Scannographing is performed by running the sleeper without rotating the pedestal having the X-ray tube. Alternatively, the scanno imaging may be performed by irradiating the subject on the bed with X-rays from two directions such as the front direction and the side direction. For example, scanning in the front direction is performed by arranging an X-ray tube at a position of 0 ° facing the subject, irradiating the subject with X-rays from the X-ray tube, and running the sleeper. The scanno imaging in the side surface direction is performed by arranging an X-ray tube at a position on the side surface (90 °) with respect to the subject, irradiating the subject with X-rays from the X-ray tube, and running the sleeper. The two-way scano photographing may be performed first in either the front direction or the side direction.

In this way, a scanno image is captured by either one-way or two-way scanno imaging. After the scanno shooting, the shooting conditions are set based on the scanno image, the sleeper is run, and the rotation of the gantry is started. After that, a tomographic image is taken by this scan.

Such an X-ray CT device is an asymmetric detector having a detection surface that is asymmetric in the channel direction with respect to a center line passing through the focal point of the X-ray tube and the rotation axis of the gantry device, or a symmetric detector in the channel direction. A symmetric detector with a detection plane is used as appropriate. In addition, regardless of whether the asymmetric detector or the symmetry detector is used, when a subject whose physique or posture is outside the imaging range is photographed by scanning, one or both sides of the subject are missing. The scanno image is obtained.

However, when performing the main scan based on such a scanno image, there is a possibility that the main scan cannot be performed properly. On the other hand, it is desirable to be able to appropriately perform this scan even for a subject that is out of the imaging range during scanno imaging.

Japanese Unexamined Patent Publication No. 2007-11515 Japanese Unexamined Patent Publication No. 2010-279532

The problem to be solved by the present invention is to make it possible to appropriately perform this scan even for a subject that is out of the imaging range during scanno imaging.

The X-ray CT apparatus according to the embodiment is estimated to include an X-ray tube, an X-ray detection unit, a first control unit, a first generation unit, a setting unit, a second control unit, and a second generation unit. It is equipped with a part.
The X-ray tube irradiates a subject placed on a top plate with X-rays.
The X-ray detector detects X-rays that have passed through the subject.
The first control unit controls the first scannographing so as to irradiate the X-ray while moving the top plate or the X-ray tube along the longitudinal direction of the top plate.
The first generation unit generates a first scanno image showing a part of the subject along the longitudinal direction based on the output of the X-ray detection unit by the first scanno imaging.
A plurality of the setting units are provided along the longitudinal direction before the second scanno imaging in which the region including a part of the contour of the subject protruding from the first scanno image in the lateral direction of the top plate is photographed. Set the position of.
The second control unit controls the second scanno imaging so that the X-ray tube is stationary at the plurality of positions in order to irradiate the X-ray.
The second generation unit generates a plurality of second scanno images showing a region including a part of the contour based on the output of the X-ray detection unit by the second scanno imaging.
The estimation unit estimates the contour based on each of the first scanno image and the second scanno image.

FIG. 1 is a block diagram showing a configuration of an X-ray CT apparatus according to a first embodiment. FIG. 2 is a schematic diagram for explaining a first scanno image and a second scanno image in the first embodiment. FIG. 3 is a schematic diagram for explaining the setting of the position in the first embodiment. FIG. 4 is a schematic diagram for explaining the setting of the position in the first embodiment. FIG. 5 is a schematic diagram for explaining the number of positions in the first embodiment. FIG. 6 is a schematic diagram for explaining the setting of the position and the angle in the first embodiment. FIG. 7 is a schematic diagram for explaining the second scanno photographing in the first embodiment. FIG. 8 is a time chart for explaining the operation in the first embodiment. FIG. 9 is a flowchart for explaining the operation in the first embodiment. FIG. 10 is a schematic diagram for explaining the operation in the first embodiment. FIG. 11 is a flowchart for explaining the operation in the first embodiment. FIG. 12 is a schematic diagram for explaining the operation in the first embodiment. FIG. 13 is a schematic diagram for explaining the operation in the first embodiment. FIG. 14 is a schematic diagram for explaining the operation in the first embodiment. FIG. 15 is a schematic diagram for explaining the setting of the position in the modified example of the first embodiment. FIG. 16 is a schematic diagram for explaining the second scanno photographing in the modified example of the first embodiment. FIG. 17 is a schematic diagram for explaining the first scanno image in the second embodiment. FIG. 18 is a schematic diagram for explaining the setting of the position and the angle in the second embodiment. FIG. 19 is a schematic diagram for explaining the second scanno photographing in the second embodiment. FIG. 20 is a time chart for explaining the operation in the second embodiment. FIG. 21 is a schematic diagram for explaining the setting of the position in the modified example of the second embodiment. FIG. 22 is a schematic diagram for explaining the second scanno photographing in the modified example of the second embodiment. FIG. 23 is a schematic diagram for explaining X-ray imaging in the third embodiment. FIG. 24 is a time chart for explaining the operation in the third embodiment. FIG. 25 is a flowchart for explaining the operation in the third embodiment. FIG. 26 is a schematic diagram for explaining the operation in the third embodiment.

Hereinafter, the X-ray CT apparatus according to each embodiment will be described with reference to the drawings. The X-ray CT device includes a Rotate / Rotate-Type (3rd generation CT) in which an X-ray tube and an X-ray detector rotate around the subject as a unit, and a large number of X-rays arranged in a ring shape. There are various types such as Stationary / Rotate-Type (4th generation CT) in which the detection element is fixed and only the X-ray tube rotates around the subject, and any type can be applied to the embodiment. Each of the following embodiments will be described by taking a third generation CT as an example.

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of an X-ray CT apparatus according to a first embodiment, and FIG. 2 is a schematic diagram for explaining a first scanno image and a second scanno image. The X-ray CT apparatus 1 irradiates the subject P with X-rays from the X-ray tube 11, and detects the irradiated X-rays with the X-ray detector 12. The X-ray CT apparatus 1 generates a CT image regarding the subject P based on the output from the X-ray detector 12.

The X-ray CT device 1 shown in FIG. 1 includes a gantry device 10, a sleeper device 30, and a console device 40. The gantry device 10 is a scanning device having a configuration for X-ray CT imaging of the subject P. The plurality of gantry devices 10 drawn in FIG. 1 show the front and side surfaces of one gantry device 10. The sleeper device 30 is a device for placing a subject P, which is a target of X-ray CT imaging, and moving it to a position where X-ray CT imaging is performed. The console device 40 is a computer that controls the gantry device 10.

For example, the gantry device 10 and the sleeper device 30 are installed in the CT examination room, and the console device 40 is installed in the control room adjacent to the CT examination room. The console device 40 does not necessarily have to be installed in the control room. For example, the console device 40 may be installed in the same room together with the gantry device 10 and the bed device 30. In any case, the gantry device 10, the sleeper device 30, and the console device 40 are connected to each other by wire or wirelessly so as to be able to communicate with each other.

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

The X-ray tube 11 irradiates the subject P placed on the top plate 33 with X-rays. Specifically, the X-ray tube 11 emits X-rays by irradiating thermoelectrons from the cathode (filament) toward the anode (target) by applying a high voltage from the X-ray high voltage device 14 and supplying a filament current. It is a vacuum tube to generate. The irradiated thermions are converted into X-rays by the energy when they collide with the focal point of the target. As a result, the X-ray tube 11 generates X-rays to irradiate the subject P from the focal point of the target with which the thermions collide. The X-rays generated in the X-ray tube 11 are formed via the collimator 17 and irradiate the subject P on the top plate 33.

The X-ray detector 12 detects X-rays irradiated from the X-ray tube 11 and passed through the subject P, and outputs an electric signal corresponding to the X-ray dose to the DAS 18. The X-ray detector 12 has, for example, a plurality of X-ray detection element trains in which a plurality of X-ray detection elements are arranged in the channel direction along one arc centering on the focal point of the X-ray tube. The X-ray detector 12 has, for example, a structure in which a plurality of X-ray detection element sequences in which a plurality of X-ray detection elements are arranged in the channel direction are arranged in a slice direction (column direction, low direction). Further, the X-ray detector 12 is an indirect conversion type detector having, for example, a grid, a scintillator array, and an optical sensor array. The scintillator array has a plurality of scintillators, and the scintillator has a scintillator crystal that outputs a photon amount of light according to an incident X dose. The grid is arranged on the surface of the scintillator array on the X-ray incident side and has an X-ray shielding plate having a function of absorbing scattered X-rays. The grid may also be called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has a function of converting into an electric signal according to the amount of light from the scintillator, and has, for example, an optical sensor such as a photomultiplier tube (PMT). The X-ray detector 12 may be a direct conversion type detector (semiconductor detector) having a semiconductor element that converts incident X-rays into an electric signal. The X-ray detector 12 is an example of an X-ray detector.

The rotating frame 13 rotatably supports the X-ray tube 11 and the X-ray detector 12 around a rotation axis. Specifically, the rotating frame 13 is an annular frame in which the X-ray tube 11 and the X-ray detector 12 are opposed to each other and the X-ray tube 11 and the X-ray detector 12 are rotated by a control device 15 described later. Is. The rotating frame 13 is rotatably supported by a fixed frame (not shown) made of a metal such as aluminum. Specifically, the rotating frame 13 is connected to the edge of the fixed frame via a bearing. In this embodiment, the present invention can also be applied to a single-tube type X-ray CT apparatus, in which a plurality of pairs of an X-ray tube 11 and an X-ray detector 12 are mounted on a rotating frame 13, so-called multi-tube. It can also be applied to a spherical X-ray CT apparatus. Further, in the present embodiment, the rotation axis of the rotation frame 13 in the non-tilt state or the longitudinal direction of the top plate 33 of the sleeper device 30 is orthogonal to the Z-axis direction and the Z-axis direction, and is horizontal to the floor surface. Is orthogonal to the X-axis direction and the Z-axis direction, and the axial direction perpendicular to the floor surface is defined as the Y-axis direction, respectively. The rotating frame 13 receives power from the drive mechanism of the control device 15 and rotates at a constant angular velocity around the rotation axis Z. The rotating frame 13 further includes and supports an X-ray high voltage device 14 and a DAS 18 in addition to the X-ray tube 11 and the X-ray detector 12. Such a rotating frame 13 is housed in a substantially cylindrical housing having an opening (bore) forming an imaging space. The central axis of the opening coincides with the rotation axis Z of the rotation frame 13. The rotation axis Z of the rotation frame 13 may be referred to as the rotation axis Z of the X-ray tube 11. The detection data generated by the DAS 18 is a photodiode provided in a non-rotating portion (for example, a fixed frame (not shown) of the gantry device by optical communication from a transmitter having a light emitting diode (LED) provided in the rotating frame. Is transmitted to a receiver having a diode and is transferred to the console device 40. The method of transmitting the detection data from the rotating frame to the non-rotating portion of the gantry device is not limited to the above-mentioned optical communication, and any method may be adopted as long as it is a non-contact type data transmission. Further, the rotating frame 13 is an example of a rotating portion.

The X-ray high voltage device 14 has an electric circuit such as a transformer and a rectifier, and has a function of generating a high voltage applied to the X-ray tube 11 and a filament current supplied to the X-ray tube 11. It has a generator and an X-ray control device that controls an output voltage according to the X-rays emitted by the X-ray tube 11. The high voltage generator may be a transformer type or an inverter type. The X-ray high voltage device 14 may be provided on the rotating frame 13 described later, or may be provided on the fixed frame (not shown) side of the gantry device 10. The fixed frame is a frame that rotatably supports the rotating frame 13. Further, the X-ray high voltage device 14 is an example of an X-ray high voltage unit.

The control device 15 has a processing circuit having a CPU (Central Processing Unit) and the like, and a drive mechanism such as a motor and an actuator. The processing circuit has a processor such as a CPU and an MPU (Micro Processing Unit) and a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory) as hardware resources. Further, the control device 15 includes an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and another complex programmable logic device (CPLD). ), It may be realized by a simple programmable logic device (SPLD). The control device 15 controls the X-ray high voltage device 14, the DAS 18, and the like in accordance with a command from the console device 40. The processor realizes the above control by reading and realizing a program stored in the memory. Further, the control device 15 has a function of receiving an input signal from the input interface 43 attached to the console device 40 or the gantry device 10 and controlling the operation of the gantry device 10 and the sleeper device 30. For example, the control device 15 controls to rotate the rotating frame 13 in response to an input signal, controls to tilt the gantry device 10, and controls to operate the sleeper device 30 and the top plate 33. The control for tilting the gantry device 10 is such that the control device 15 rotates around an axis parallel to the X-axis direction based on the tilt angle (tilt angle) information input by the input interface attached to the gantry device 10. It is realized by rotating. The control device 15 may be provided in the gantry device 10 or in the console device 40. Further, the control device 15 is an example of a control unit. The control device 15 may be configured to directly incorporate the program into the circuit of the processor instead of storing the program in the memory. In this case, the processor realizes the above control by reading and executing a program incorporated in the circuit.

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

The collimator 17 is a lead plate or the like for narrowing the irradiation range of X-rays transmitted through the wedge 16, and a slit is formed by a combination of a plurality of lead plates or the like. The collimator 17 may be called an X-ray diaphragm.

The DAS18 (Data Acquisition System) is an amplifier that amplifies the electric signal output from each X-ray detection element of the X-ray detector 12, and an A / D conversion that converts the amplified electric signal into a digital signal. It has a device and generates detection data having a digital value indicated by the digital signal. The detection data is a set of digital values of X-ray intensity identified by the channel number, column number, and view number indicating the collected view of the source X-ray detector. As the view number, the order in which the views are collected (collection time) may be used, or a number representing the rotation angle of the X-ray tube 11 (eg, 1 to 1000) may be used. The detection data generated by the DAS 18 is transferred to the console device 40 via a non-contact data transmission circuit (not shown) housed in the gantry device 10. Further, the DAS 18 may be called a data collection unit.

The sleeper device 30 is a device for placing and moving the subject P to be scanned, and includes a base 31, a sleeper drive device 32, a top plate 33, and a support frame 34.

The base 31 is a housing that supports the support frame 34 so as to be movable in the vertical direction.

The sleeper drive device 32 is a motor or an actuator that moves the top plate 33 on which the subject P is placed in the longitudinal direction of the top plate 33. As a method of moving the top plate 33, for example, a method of moving only the top plate 33 or a method of moving together with the support frame 34 of the sleeper device 30 may be used. In the case of standing CT, a method of moving the patient support mechanism corresponding to the top plate 33 may be used. The sleeper drive device 32 moves the top plate 33 under the control of the console device 40 or the control device 15. For example, the sleeper drive device 32 sets the top plate 33 with respect to the subject P so that the body axis of the subject P placed on the top plate 33 coincides with the rotation axis (central axis of the opening) of the rotation frame 13. Move in the orthogonal direction. Further, the sleeper drive device 32 may move the top plate 33 on which the subject P is placed along the longitudinal direction of the top plate 33 in response to the X-ray CT imaging performed by the gantry device 10. good. The sleeper drive device 32 generates power by driving at a rotation speed according to the duty ratio and the like of the drive signal from the control device 15. The sleeper drive device 32 is realized by, for example, a motor such as a direct drive motor or a servo motor.

The top plate 33 provided on the upper surface of the support frame 34 is a plate on which the subject P is placed. In addition to the top plate 33, the sleeper drive device 32 may move the support frame 34 in the longitudinal direction of the top plate 33. When performing a scan (helical scan, positioning scan, etc.) involving a relative change in the positional relationship of the top plate 33 of the gantry device 10, the relative change in the positional relationship is performed by driving the top plate 33. It may be performed by running the gantry device 10, or may be performed by a combination thereof.

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

The memory 41 is realized by, for example, a RAM (Random Access Memory), a semiconductor memory element such as a flash memory, a hard disk, an optical disk, or the like. The memory 41 stores, for example, projection data, reconstructed image data, a first scanno image, a plurality of second scanno images, data of an image being processed or a display image, and a control program or table according to the present embodiment. Further, the memory 41 is an example of a storage unit.

The first scanno image is a scanno image (positioning image) acquired by the same inspection as this scan. As an example shown in FIG. 2, the first scanno image g10 according to the present embodiment is an image showing a part of the subject P along the longitudinal direction Z of the top plate 33. In the first scanno image g10, the X-ray tube 11 is fixed at a predetermined rotation angle, and the top plate 33 or the X-ray tube 11 is moved along the longitudinal direction Z of the top plate 33 to irradiate X-rays. It is generated from the detection data acquired by shooting. The first scanno image is not limited to a single imaging direction, and may be an image obtained from a plurality of imaging directions.

Each of the second scanno images g21 and g22 is an image (positioning image) showing a region including a part of the contour of the subject P protruding from the first scanno image g10 in the lateral direction X of the top plate 33. Each of the second scanno images g21 and g22 is an image acquired by the second scanno imaging in which the X-ray tube 11 is stationary and irradiated with X-rays in order at a plurality of positions along the longitudinal direction of the top plate. In the second scanno imaging, since the X-ray tube 11 is irradiated at a stationary position, the exposed area is narrower than that in the first scanno imaging in which the X-ray tube 11 is moved and the X-ray is irradiated. Therefore, when taking a scano image of a region protruding from the first scanno image g10, it is better to take a second scano image with a narrow exposed area instead of performing the first scano image with a wide exposed area again. Can be reduced. The first scout image and the second scout image may be referred to as a first positioning image and a second positioning image, respectively, and may be referred to as a first scout image and a second scout image, respectively.

The table may be, for example, information set by associating each of a plurality of positions along the longitudinal direction of the top plate 33 used for the second scanno photographing with the angle around the rotation axis of the X-ray tube 11. The angle of the X-ray tube 11 in the second scanno imaging may be a common value at a plurality of positions or may be a different value. Further, as the angle of the X-ray tube 11 in the second scanno photographing, a value obtained from an empirical rule such as 30 ° or 45 ° can be used.

The storage area of the memory 41 may be in the X-ray CT device 1 or in an external storage device connected by a network.

The display 42 displays various information. For example, the display 42 outputs a medical image generated by the processing circuit 44, a GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, the display 42 may be, for example, a liquid crystal display (LCD), a CRT (Cathode Ray Tube) display, an organic EL display (OELD), a plasma display, or any other display. , Can be used. The display 42 is an example of a display unit. Further, the display 42 may be provided on the gantry device 10. The display 42 may be a desktop type, or may be configured by a tablet terminal or the like capable of wireless communication with the console device 40 main body.

The input interface 43 receives various input operations from the operator, converts the received input operations into electric signals, and outputs the received input operations to the processing circuit 44. For example, the input interface 43 receives from the operator collection conditions for collecting projection data, reconstruction conditions for reconstructing a CT image, image processing conditions for generating a post-processed image from a CT image, and the like. .. As the input interface 43, for example, a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad, a touch panel display, and the like can be appropriately used. Further, the input interface 43 is an example of an input unit. In the present embodiment, the input interface 43 is a physical operation component such as a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad, and a touch panel display. It is not limited to those equipped with. For example, an example of the input interface 43 includes an electric signal processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the device and outputs the electric signal to the processing circuit 44. .. Further, the input interface 43 may be provided in the gantry device 10. Further, the input interface 43 may be composed of a tablet terminal or the like capable of wireless communication with the console device 40 main body.

The processing circuit 44 controls the operation of the entire X-ray CT apparatus 1. For example, the processing circuit 44 has a processor such as a CPU, MPU, and GPU (Graphics Processing Unit) and a memory such as a ROM or RAM as hardware resources. The processing circuit 44 executes a system control function 441, a scan control function 442, a display control function 443, an image generation function 444, an image processing function 445, and the like by a processor that executes each program expanded in the memory. Supplementally, the processing circuit 44 in the state where each program is read out has each function shown in the processing circuit 44 of FIG. Although it has been described in FIG. 1 that each function is executed by a single processor, the function is realized by combining a plurality of independent processors to form a processing circuit 44 and each processor executing a program. It doesn't matter if you do. Further, in FIG. 1, a single memory 41 has been described as storing a program corresponding to each function, but a plurality of memories are distributed and arranged, and the processing circuit 44 stores the corresponding program from the individual memories. It may be configured to be read. Further, the processing circuit 44 is an example of a processing unit.

The system control function 441 controls each function of the processing circuit 44 based on the input operation received from the operator via the input interface 43. Specifically, the system control function 441 reads out the control program stored in the memory 41, expands it on the memory in the processing circuit 44, and controls each part of the X-ray CT apparatus 1 according to the expanded control program. .. Further, the system control function 441 is an example of a control unit.

The scan control function 442 has a first control function, a setting function, and a second control function.

The first control function (first control unit) controls the first scanno imaging so as to irradiate X-rays while moving the top plate 33 or the X-ray tube 11 along the longitudinal direction of the top plate 33.

The setting function (setting unit) is performed on the top plate 33 before the second scanno imaging in which the area including a part of the contour of the subject P protruding from the first scanno image g10 in the lateral direction of the top plate 33 is photographed. Set multiple positions along the longitudinal direction. For example, the setting function manually or automatically sets a plurality of positions z1 and z2 as shown in FIGS. 3 and 4. Specifically, in the case of manual operation, as shown in FIGS. 3 (a) and 4 (a), the coordinates (xa, z1) of the point p1 and the point p2 designated by the operator by the operation of the input interface 43 The positions z1 and z2 along the longitudinal direction may be set based on the coordinates (xb, z2). Alternatively, in the case of automatic, the pixel value distribution in the channel direction is extracted for each position along the longitudinal direction Z in the first scanno image g10, and the pixel is based on the shape or statistical value (average value, variation) of the pixel value distribution. The value distribution may be classified into groups, the pixel value distribution may be selected for each group, and the position in the longitudinal direction Z corresponding to the selected pixel value distribution may be set. In the case of classification based on the shape, some patterns such as a substantially L-shaped shape and a convex shape may be held in advance and classified by comparison with the pattern. In the case of classification based on statistical values, a threshold value may be held in advance for each type of statistics such as mean value and standard deviation, and the threshold value may be compared with the threshold value for classification. For example, as shown in FIG. 3B, the setting function sets the position z1 by classifying the pixel value distribution into the first group based on a substantially L-shaped shape of the pixel value distribution or a low average value. May be good. Specifically, the position z1 may be the central position within the range of the longitudinal direction Z in the pixel value distribution in the first group, or may be the position at a predetermined distance from the end of the first scanno image g10 in the longitudinal direction Z. May be good. Similarly, as shown in FIG. 4B, the setting function classifies the pixel value distribution into the second group based on the convex shape or large variation (standard deviation, variance) of the pixel value distribution. You may set z2. Specifically, the position z2 may be the central position within the range of the longitudinal direction Z in the pixel value distribution in the second group, or may be the position at a predetermined distance from the end of the first scanno image g10 in the longitudinal direction Z. May be good. The plurality of positions are not limited to the two positions z1 and z2, but may be three positions z1 to z3 as shown in FIG. 5, and four or more positions (as long as they are within the scan range of the first scanno shooting). (Not shown) may be used. However, the number of positions for the second scanno imaging is preferably two in consideration of the fact that the exposure dose increases in proportion to the number of positions and that the accuracy of the estimated contour may be low. When the number of positions of the second scanno imaging is two, it is preferable that the two positions are separated from each other by a predetermined distance or more from the viewpoint of ensuring the accuracy of the estimated contour. Further, as shown in FIG. 6, the setting function may be set in association with each of the plurality of positions z1 and x2 and the angles θ1 and θ2 around the rotation axis of the X-ray tube 11. For example, the setting function may set the positions z1 and z2 in association with the angles θ1 and θ2 in the table in the memory 41.

The second control function (second control unit) controls the second scanno imaging so that the X-ray tube 11 is stopped in order at the set plurality of positions z1 and z2 to irradiate X-rays. As shown in FIGS. 6 and 7, the second control function makes the X-ray tube 11 stationary and X-rays at an angle θ1 (or θ2) associated with the stationary position z1 (or z2). X-rays may be irradiated with the tube 11 arranged. By such second scanno imaging, the second scanno images g21 and g22 are generated by the image generation function 444 described later.

The display control function 443 controls the display 42 so as to display various kinds of information.

The image generation function 444 has a first generation function and a second generation function for generating a scanno image based on the output of the X-ray detector 12. The output of the X-ray detector 12 is transferred to the console device 40 as detection data via the DAS 18 and a non-contact data transmission circuit (not shown).

The first generation function (first generation unit) performs a part of the subject P along the longitudinal direction of the top plate 33 based on the output of the X-ray detection unit (X-ray detector 12) by the first scanno imaging. The first scanno image g10 shown is generated.

The second generation function (second generation unit) is a plurality of second generations indicating a region including a part of the contour of the subject P based on the output of the X-ray detector (X-ray detector 12) by the second scanno imaging. 2 Scanno images g21 and g22 are generated.

In addition to this, the image generation function 444 generates data obtained by subjecting the detection data output from the DAS 18 to preprocessing such as logarithmic conversion processing, offset correction processing, and sensitivity correction processing between channels. The data before preprocessing (detection data) and the data after preprocessing may be collectively referred to as projection data or raw data.

The image generation function 444 generates CT image data by performing reconstruction processing using a filter correction back projection method, a successive approximation reconstruction method, or the like on the generated projection data. When reconstructing a CT image, the full-scan reconstruction method requires projection data for 360 ° around the subject, and the half-scan reconstruction method also requires projection data for 180 ° + fan angle. .. It is applicable to this embodiment to any reconstruction method of full scan or half scan. The CT image data represents the spatial distribution of CT values for subject P. The CT value is a value for expressing a CT image, and refers to a relative value defined as 0 for water and -1000 for air. The CT value is determined by the X-ray attenuation coefficient, and calibration is performed so that the X-ray attenuation coefficient μ_water of water becomes 0 and the X-ray attenuation coefficient μ_air of air becomes −1000. Therefore, a tissue having a higher X-ray attenuation coefficient than water has a higher CT value. When the X-ray attenuation coefficient of the tissue is μ, the CT value [HU] of the tissue can be obtained from the following equation.
Tissue CT value [HU] = 1000 × (μ－μ_water) / μ_water
The image processing function 445 has an estimation function. The estimation function is based on each of the first scanno image g10 and the second scanno images g21 and g22 generated by the image generation function 444, and the subject protrudes from the first scanno image g10 in the lateral direction X of the top plate 33. Estimate the contour of a part of P. For example, the estimation function is a part of the contour included in the region indicated by each of the second scanno images g21 and g22 in a state where the first scanno image g10 and the plurality of second scanno images g21 and g22 are partially overlapped. The contour may be estimated by connecting the two with a line.

In addition to this, the image processing function 445 uses a known method to obtain CT image data generated by the image generation function 444 based on an input operation received from the operator via the input interface 43, and tomographic image data of an arbitrary cross section. And convert to 3D image data. The converted tomographic image data and the three-dimensional image data are data having distribution information of CT values in the three-dimensional space. It is displayed on the display 42. As known methods, for example, three-dimensional image processing such as volume rendering, surface rendering, image value projection processing, MPR (Multi-Planer Reconstruction) processing, and CPR (Curved MPR) processing can be appropriately used. .. The image processing function 445 is an example of an image processing unit.

The system control function 441, the scan control function 442, the display control function 443, the image generation function 444, and the image processing function 445 may be mounted by the processing circuit 44 of one board, or may be mounted by the processing circuit 44 of a plurality of boards. It may be implemented in a distributed manner. Similarly, although the console device 40 has been described as executing a plurality of functions on a single console, a plurality of functions may be executed by different consoles. The processing circuit 44 is not limited to the case where it is included in the console device 40, and may be included in an integrated server that collectively performs processing on detection data acquired by a plurality of medical image diagnostic devices (not shown).

Next, the operation of the X-ray diagnostic apparatus configured as described above will be described with reference to FIGS. 8 to 14. 8 is a time chart, and 9 and 11 are flowcharts. 10 and 12 to 14 are schematic views.

First, the X-ray CT apparatus 1 acquires subject information (patient information) regarding a subject to be inspected from an inspection reservation system or the like via a communication interface (not shown). The subject information is patient ID, patient name, date of birth, age, body weight, gender, and examination site. The subject information may include implant information indicating the implant of the subject.

Subsequently, in the X-ray CT apparatus 1, the patient is set on the top plate 33 by the operator. Further, by operating the input interface 43 by the operator, the top plate 33 moves to the start position zs of the first scanno shooting as shown in FIG. By operating the input interface 43 by the operator, a preset scan plan is selected, and detailed conditions for the scan plan are set.

Then, in step ST1 shown in FIGS. 8 and 9, the scan control function 442 of the processing circuit 44 causes the top plate 33 to irradiate X-rays while moving the top plate 33 along the longitudinal direction Z of the top plate 33 according to the scan plan. The first scanno shooting is controlled so as to. As a result, the first scannographing of the subject P is executed. When the top plate 33 reaches the end position ze of the first scanno shooting, the scan control function 442 stops the top plate 33 and ends the first scanno shooting.

After step ST1, in step ST2, as shown in FIG. 10, the image generation function 444 of the processing circuit 44 sets a part of the subject P to the sky based on the output of the X-ray detector 12 by the first scanno photographing. A first scanno image g10 shown along the longitudinal direction of the plate 33 is generated. The first scanno image g10 is stored in the memory 41.

After step ST2, in step ST3, the scan control function 442 photographs a region including a part of the contour of the subject P protruding from the first scanno image g10 in the lateral direction X of the top plate 33. Before, a plurality of positions z1 and z2 along the longitudinal direction Z of the top plate 33 are set. At this time, the scan control function 442 sets each of the plurality of positions z1 and x2 in association with the angles θ1 and θ2 around the rotation axis of the X-ray tube 11.

This step ST3 may be executed, for example, as shown in steps ST3-1 to ST3-5 of FIG. For example, the scan control function 442 reads the first scanno image g10 from the memory 41 (step ST3-1), and obtains a pixel value distribution in the channel direction for each position along the longitudinal direction Z in the first scanno image g10. Extract (step ST3-2). Since the "pixel value distribution" indicates the distribution of the detected value of the X-ray transmittance with respect to the subject P, it may be referred to as the "detected value distribution". Subsequently, the scan control function 442 classifies the pixel value distribution into groups according to the shape or statistical value (step ST3-3), and selects the pixel value distribution for each group (step ST3-4). After that, the scan control function 442 sets the position in the longitudinal direction Z corresponding to the selected pixel value distribution (step ST3-5). Further, the scan control function 442 sets each of the plurality of positions z1 and x2 in association with the angles θ1 and θ2 around the rotation axis of the X-ray tube 11.

After step ST3, in step ST4, the scan control function 442 controls the second scanno imaging so that the X-ray tube 11 is stopped in order at the set plurality of positions z1 and z2 to irradiate X-rays. In the present embodiment, the scan control function 442 keeps the X-ray tube 11 stationary and arranges the X-ray tube 11 at an angle θ1 (or θ2) associated with the stationary position z1 (or z2). Irradiate with X-rays. The timing for arranging the X-ray tube 11 at the angle θ1 (or θ2) may be during the movement of the top plate 33 or the X-ray tube 11, and after the top plate 33 or the X-ray tube 11 is stationary at the position z1 (or z2). But it may be. The X-ray detector 12 detects the X-rays that have passed through the subject P. The output of the X-ray detector 12 is transferred to the console device 40 as detection data via the DAS 18 and a non-contact data transmission circuit (not shown). In this way, the second scanno shooting is executed.

After step ST4, in step ST5, the image generation function 444 is a plurality of second scanno images showing a region including a part of the contour of the subject P based on the output of the X-ray detector 12 by the second scanno imaging. Generate g21 and g22.

After step ST5, in step ST6, the image processing function 445 protrudes from the first scanno image g10 in the lateral direction X of the top plate 33 based on each of the first scanno image g10 and the second scanno images g21 and g22. The contour of a part of the subject P is estimated. For example, as shown in FIG. 12, the image processing function 445 identifies a point p1c indicating a part of the contour from a portion having a large change in the pixel value distribution in the channel direction of the second scanno image g21. Similarly, for example, as shown in FIG. 13, the image processing function 445 has a contour from the outermost portion of the subject P among the portions having a large change in the pixel value distribution in the channel direction of the second scanno image g22. The point p2c indicating the part is specified. After that, in the image processing function 445, as shown in FIG. 14, each of the second scanno images g21 and g22 is in a state where the first scanno image g10 and the plurality of second scanno images g21 and g22 are partially overlapped. The contour Cp of the subject P is estimated by connecting the points p1c and p2c indicating a part of the contour included in the indicated region with a line. The line connecting the points p1c and p2c is preferably a straight line in consideration of the ease of processing and the fact that the accuracy of the estimated contour may be low. However, the line connecting the points p1c and p2c is not limited to a straight line, and may be a predetermined curve. Alternatively, the line connecting the points p1c and p2c may be an inverted contour line obtained by inverting the contour line of the subject in the first scanno image g10 to the center of the spine. That is, as the line connecting the points p1c and p2c, it is sufficient to know the field of view (FOV) of the present scan range, so that a line having an arbitrary shape such as a straight line or a curved line can be appropriately used. Further, the line connecting the points p1c and p2c may be drawn by the operation of the input interface 43 of the operator. In any case, the contour of the subject P is estimated by step ST6.

Further, the image processing function 445 stores the scanno image g30 including the estimated contour Cp in the memory 41 as shown in FIG.

After step ST6, in step ST7, the display control function 443 controls the display 42 so as to display the scanno image g30 in the memory 41. As a result, the display 42 displays the scanno image g30 including the estimated contour Cp.

Hereinafter, the scan plan used by the operator for the main scan is determined based on the displayed scanno image g30. Subsequently, the X-ray CT apparatus 1 sets a shooting range using the scanno image in the memory 41 in response to the operation of the input interface 43 by the operator, and moves the top plate 33 to the shooting start position. After that, the X-ray CT apparatus 1 performs the main scan according to the determined scan plan.

As described above, according to the first embodiment, the first scannographing is controlled so as to irradiate X-rays while moving the top plate or the X-ray tube along the longitudinal direction of the top plate. Based on the output of the X-ray detector by the first scanno imaging, a first scanno image showing a part of the subject along the longitudinal direction is generated. Prior to the second scanno imaging in which the region including a part of the contour of the subject protruding from the first scanno image in the lateral direction of the top plate is photographed, a plurality of positions along the longitudinal direction are set. The second scanno imaging is controlled so that the X-ray tube is stationary and the X-ray is irradiated to the plurality of positions in order. Based on the output of the X-ray detector by the second scanno imaging, a plurality of second scanno images showing a region including a part of the contour are generated. The contour is estimated based on each of the first scanno image and the second scanno image.

In this way, even if a first scanno image in which one side of the subject is missing can be obtained, the contour of the subject can be estimated using each of the second scanno images. (FOV) can be selected appropriately. Therefore, this scan can be appropriately executed even for a subject that is out of the imaging range during scanno imaging.

In addition, since the second scanno imaging irradiates X-rays at a position where the X-ray tube is stationary, the exposed area is narrower than that of the first scanning imaging in which the X-ray tube is irradiated while moving the X-ray tube, so that the patient is exposed to radiation. The amount is low. In addition, unlike the present embodiment, if the first scanno-photographing is performed twice on the subject outside the imaging range, the exposure dose of the scano-imaging will be doubled.

Therefore, in addition to the above-mentioned effects, when the area outside the first scanno image is scanned, the second scano image with a narrow exposed area is performed. Can be reduced. For this reason, even if the detector width is reduced and the number of examinations in which a part of the subject does not fall within the range of scanno imaging increases in the future, the contour of the subject is suppressed while suppressing the exposure dose during scanning. Can be estimated.

Further, according to the first embodiment, a part of the contour included in the region indicated by each of the second scanno images is drawn by a line in a state where the first scanno image and the plurality of second scanno images are partially overlapped. By tying, the contour can be estimated. In this case, the contour can be estimated by a simple process of connecting a part of the contour shown by each of the second scanno images with a line.

Further, according to the first embodiment, before the second scanno imaging, each of the plurality of positions in the longitudinal direction is set in association with the angle around the rotation axis of the X-ray tube. At the time of the second scanno photographing, the X-ray tube is made stationary, and the X-ray tube is irradiated with the X-ray tube arranged at the angle corresponding to the position to be made stationary. In this case, the X-ray tube can be arranged so that the irradiation position and irradiation direction of the X-ray are appropriate at the time of the second scanno imaging.

<Modification example>
Next, a modification of the first embodiment will be described. In this modification, in the above-mentioned X-ray CT apparatus 1, the angle of the X-ray tube 11 is fixed at the time of the second scanno imaging, and the X-ray tube 11 (including the gantry device 10) or the top plate 33 is placed on the top plate. It is configured to move along the lateral direction X of 33.

Along with this, as shown in FIG. 15, the setting function (setting unit) of the scan control function 442 includes each of the plurality of positions z1 and z2 along the longitudinal direction Z of the top plate 33 and the short side of the top plate 33. The positions x1 and x2 in the direction X are associated with each other and set. For example, the setting function may set the positions z1 and z2 and the positions x1 and x2 in association with each other in the table in the memory 41.

As shown in FIGS. 15 and 16, the second control function (second control unit) of the scan control function 442 makes the X-ray tube 11 or the top plate 33 stationary at the plurality of set positions z1 and z2 in order. At the same time, X-rays are irradiated with the X-ray tube 11 facing the positions x1 and x2 in the lateral direction corresponding to the stationary positions z1 and z2. By such second scanno imaging, the image generation function 444 generates the second scanno images g21 and g22.

Other configurations are the same as in the first embodiment.

According to the modification of the configuration as described above, after the first scanno image is generated, each of the plurality of positions along the longitudinal direction of the top plate is set in association with the position in the lateral direction of the top plate. do. Subsequently, in the second scanno imaging, the X-ray tube or the top plate is stationary at the set plurality of positions in order, and the X-ray tube is opposed to the position in the lateral direction corresponding to the stationary position. Irradiate with X-rays in the state of being. Therefore, according to the modified example, the same effect as that of the first embodiment can be obtained except for the effect related to the angle of the X-ray tube 11.

<Second embodiment>
Next, the X-ray CT apparatus according to the second embodiment will be described.

The second embodiment is different from the first embodiment, and as shown in FIG. 17, relates to a configuration in which the contours on both the left and right sides of the subject P protrude from the first scanno image g11.

In this case, the setting function (setting unit) of the scan control function 442 sets a part of the contour on the right side of the subject P and a part of the contour on the left side of the subject P, as shown in FIGS. 18 and 19. Each of the plurality of positions z1 and z2 and the two angles (θ1a, θ1b) and (θ2a, θ2b) around the rotation axis of the X-ray tube 11 are set in association with each other so as to be photographed separately.

Other configurations are the same as in the first embodiment.

Next, the operation of the X-ray CT apparatus configured as described above will be described with reference to the time chart of FIG.

Now, it is assumed that step ST1 is executed in the same manner as described above.

After step ST1, in step ST2, as shown in FIG. 17, the image generation function 444 of the processing circuit 44 sets a part of the subject P to the sky based on the output of the X-ray detector 12 by the first scanno photographing. A first scanno image g11 shown along the longitudinal direction of the plate 33 is generated. In this example, the first scanno image g11 shows the torso protruding from both the left and right sides of the subject P as a part of the subject P. Such a first scanno image g11 is stored in the memory 41.

After step ST2, in step ST3, the scan control function 442 photographs a region including a part of the contour of the subject P protruding from the first scanno image g11 in the lateral direction X of the top plate 33. Before, a plurality of positions z1 and z2 along the longitudinal direction Z of the top plate 33 are set. Specifically, the scan control function 442 sets each of the plurality of positions z1 and z2 so as to separately capture a part of the contour on the right side of the subject P and a part of the contour on the left side of the subject P. , The two angles (θ1a, θ1b) and (θ2a, θ2b) around the rotation axis of the X-ray tube 11 are set in association with each other.

After step ST3, in step ST4, the scan control function 442 controls the second scanno imaging so that the X-ray tube 11 is stopped in order at the set plurality of positions z1 and z2 to irradiate X-rays. In the present embodiment, the scan control function 442 makes the X-ray tube 11 stationary at the position z2, and arranges the X-ray tube 11 at an angle θ2a (or θ2b) associated with the stationary position z2. Irradiate the line. The timing for arranging the X-ray tube 11 at the angle θ2a (or θ2b) may be during the movement of the top plate 33 or the X-ray tube 11 or after the top plate 33 or the X-ray tube 11 is stationary at the position z2. The X-ray detector 12 detects the X-rays that have passed through the subject P. The output of the X-ray detector 12 is transferred to the console device 40 as detection data via the DAS 18 and a non-contact data transmission circuit (not shown). Similarly, the scan control function 442 makes the X-ray tube 11 stationary at the position z1 and emits X-rays in a state where the X-ray tube 11 is arranged at an angle θ1a (or θ1b) associated with the stationary position z1. Irradiate. The timing for arranging the X-ray tube 11 at the angle θ1a (or θ1b) may be during the movement of the top plate 33 or the X-ray tube 11 or after the top plate 33 or the X-ray tube 11 is stationary at the position z1. The X-ray detector 12 detects the X-rays that have passed through the subject P. The output of the X-ray detector 12 is transferred to the console device 40 as detection data via the DAS 18 and a non-contact data transmission circuit (not shown). In this way, the second scanno shooting is executed.

After step ST4, in step ST5, the image generation function 444 is a plurality of second scanno images showing a region including a part of the contour of the subject P based on the output of the X-ray detector 12 by the second scanno imaging. Generate g21a, g21b, g22a, g22b.

After step ST5, in step ST6, the image processing function 445 is based on each of the first scanno image g11 and the second scanno image g21a, g21b, g22a, g22b, and the short side of the top plate 33 from the first scanno image g10. The contour Cp of a part of the subject P protruding in the direction X is estimated. The estimation method is the same as that of the first embodiment. For example, as shown in FIG. 19, the image processing function 445 identifies points p1a and p1b indicating a part of the contour from a portion having a large change in the pixel value distribution in the channel direction of the second scanno images g21a and g21b. Similarly, for example, the image processing function 445 is a point p2a showing a part of the contour from the outermost part of the subject P among the parts having a large change in the pixel value distribution in the channel direction of the second scanno images g22a and g22b. , P2b are specified. After that, the image processing function 445 performs the second scanno images g21a, g21b, g22a, g22b in a state where the first scanno image g11 and the plurality of second scanno images g21a, g21b, g22a, g22b are partially overlapped. The contour Cp of the subject P is estimated by connecting the points p1a, p1b, p2a, and p2b indicating a part of the contour included in the region indicated by. As the line connecting each point, a straight line, a curved line, and an inverted contour line can be appropriately used as described above. In any case, the contour Cp of the subject P is estimated by step ST6.

Further, the image processing function 445 saves the scanno image including the estimated contour Cp in the memory 41.

Hereinafter, the processes after step ST7 are executed in the same manner as described above.

As described above, according to the second embodiment, when the contours on both the left and right sides of the subject protrude from the first scanno image, a part of the contour on the right side of the subject and a part of the contour on the left side of the subject. And are set in association with each of the plurality of positions and the two angles around the rotation axis of the X-ray tube so as to photograph the images separately.

As a result, even if the contours on both the left and right sides of the subject protrude from the first scanno image, a part of the contour on the right side of the subject and a part of the contour on the left side of the subject are captured during the second scanno imaging. Can be taken separately. Therefore, even when the contours on both the left and right sides of the subject protrude from the first scanno image, the exposure dose for scanno imaging can be reduced as in the first embodiment.

<Modification example>
Next, a modified example of the second embodiment will be described. In this modification, in the above-mentioned X-ray CT apparatus 1, the angle of the X-ray tube 11 is fixed at the time of the second scanno imaging, and the X-ray tube 11 (including the gantry device 10) or the top plate 33 is placed on the top plate. It is configured to move along the lateral direction X of 33.

Along with this, as shown in FIG. 21, the setting function (setting unit) of the scan control function 442 is on the right side of the subject P when the contours on both the left and right sides of the subject P protrude from the first scanno image g11. Each of the plurality of positions z1 and z2 along the longitudinal direction Z of the top plate 33 and the short side of the top plate 33 so that a part of the contour and a part of the contour on the left side of the subject P are photographed separately. The two positions (x1a, x1b) and (x2a, x2b) in the direction X are set in association with each other. For example, the setting function may set the positions z1 and z2 in association with the positions (x1a, x1b) and (x2a, x2b) in the table in the memory 41.

As shown in FIGS. 21 and 22, the second control function (second control unit) of the scan control function 442 makes the X-ray tube 11 or the top plate 33 stationary at the plurality of set positions z1 and z2 in order. At the same time, X-rays are irradiated with the X-ray tube 11 facing the positions (x1a, x1b) and (x2a, x2b) in the lateral direction corresponding to the stationary positions z1 and z2. By such second scanno imaging, the image generation function 444 generates the second scanno images g21a, g21b, g22a, g22b.

Other configurations are the same as in the first embodiment.

According to the modification of the configuration as described above, when the contours on both the left and right sides of the subject protrude from the first scanno image after the first scanno image is generated, a part of the contour on the right side of the subject and the subject are covered. Each of the plurality of positions and the two positions in the lateral direction are set in association with each other so that a part of the contour on the left side of the sample is photographed separately. Subsequently, in the second scanno imaging, the X-ray tube or the top plate is stationary at the set plurality of positions in order, and the X-ray tube is opposed to the position in the lateral direction corresponding to the stationary position. Irradiate with X-rays in the state of being. Therefore, according to the modified example, the same effect as that of the second embodiment can be obtained except for the effect related to the angle of the X-ray tube 11.

<Third embodiment>
Next, the X-ray CT apparatus according to the third embodiment will be described.

The third embodiment is a modification of the first or second embodiment, and relates to a configuration for estimating a tube current value for this scan. Specifically, the reason why this scan cannot be performed properly is that the correct dose cannot be obtained from the missing first scanno image, not only when the field of view (FOV) is unknown, and the AEC (Auto Exposure Control) in this scan is automatic. The accuracy of exposure control) may decrease. The third embodiment prevents such a decrease in accuracy and makes it possible to appropriately execute this scan. The following description is mainly based on a modification of the second embodiment (when the contours on both the left and right sides of the subject P protrude from the first scanno image g11) among the first and second embodiments. Will be described.

Specifically, the setting function of the scan control function 442 is a length corresponding to a part of the protruding contour when the contours on the left and right sides or both sides of the subject P protrude from the first scanno image g10 or g11. The position z2 along the direction Z is set. As described above, the setting function may set a plurality of positions z1 and z2 along the longitudinal direction of the top plate 33.

Further, the scan control function 442 has an X-ray imaging control function in addition to the above-mentioned function. The X-ray imaging control function (X-ray imaging control unit) makes the X-ray tube 11 stationary at the position z2 set by the setting function, and within the X-ray irradiation range within the angle around the rotation axis of the X-ray tube 11. X-ray imaging is controlled so that X-rays are irradiated with the X-ray tube arranged at an angle (eg, 90 °) at which the contours on both the upper and lower sides of the subject P enter.

The image generation function 444 has an X-ray image generation function in addition to the above-mentioned function. As shown in FIG. 23, the X-ray image generation function (X-ray image generation unit) is an X-ray image g showing a part of a region of the subject P based on the output of the X-ray detector 12 in X-ray imaging. Generate (90 °). In addition, "X-ray photography" and "X-ray image" may be referred to as "third scanno photography" and "third scanno image", respectively.

The image processing function 445 has a tube current estimation function in addition to the above-mentioned function. The tube current estimation function (tube current estimation unit) is set based on the difference value between the pixel value of the first scanno image g10 or g11 and the pixel value of the X-ray image g (90 °) at the position set by the setting function. Estimate the tube current value for the main scan at the specified position.

Here, the tube current estimation function may execute the following two processes (i) and (ii) when the contours on both the left and right sides of the subject P protrude from the first scanno image g11.

(I) A process of adding half of the difference value to the pixel value of the first scanno image g11 and obtaining the pixel value of the addition result. Here, the "difference value" corresponds to the protruding region (both left and right sides) of the subject P. The "half value of the difference value" corresponds to one of the left and right sides of the subject P protruding. In the case where only one of the left and right sides originally protrudes (first scanno image g10), "half the value of the difference value" may be read as "difference value".

(Ii) A process of estimating the tube current value for the main scan based on the pixel value of the addition result and the pixel value of the reference image of the main scan.

Other configurations are the same as in the first or second embodiment. However, from the viewpoint of estimating the tube current value, the above-mentioned function related to the second scanno imaging is not essential and may be omitted. Here, as the functions related to the second scanno shooting that can be omitted, there are a second control function for controlling the second scanno shooting, a second generation function for generating the second scanno image, and an estimation unit for estimating the contour.

Next, the operation of the X-ray CT apparatus configured as described above will be described with reference to the time chart of FIG. 24, the flowchart of FIG. 25, and the schematic diagram of FIG. 26. The following description will be described mainly by taking as an example the case where the contours on both the left and right sides of the subject P protrude from the first scanno image g11.

In this operation, when the steps ST1 to ST7 for estimating the contour described above are executed, the steps ST4X, ST5X, and ST6X for estimating the tube current value are executed. Steps ST4X, ST5X, and ST6X are executed, for example, immediately before steps ST4, ST5, and ST6, respectively.

Now, it is assumed that steps ST1 to ST3 are executed in the same manner as described above. However, one of the positions set in step ST3 is also used in steps ST4X and ST6X.

After step ST3, in step ST4X, the scan control function 442 makes the X-ray tube 11 stationary at the set position z2, and the subject is within the X-ray irradiation range within the angle around the rotation axis of the X-ray tube 11. X-ray imaging is controlled so that X-rays are irradiated with the X-ray tube arranged at an angle (eg, 90 °) at which the contours on both the upper and lower sides of P enter.

After step ST4X, step ST4 is executed in the same manner as described above.

After step ST4, in step ST5X, the image generation function 444 generates an X-ray image g (90 °) showing a part of the region of the subject P based on the output of the X-ray detector 12 in the X-ray imaging. do.

After step ST5X, step ST5 is executed in the same manner as described above.

After step ST5, in step ST6X, the image processing function 445 was set based on the difference value between the pixel value of the first scanno image g11 at the set position z2 and the pixel value of the X-ray image g (90 °). The tube current value for the main scan at position z2 is estimated. For example, the image processing function 445 adds half the value of the difference value to the pixel value of the first scanno image g11, and obtains the pixel value of the addition result. After that, the image processing function 445 estimates the tube current value for the main scan based on the pixel value of the addition result and the pixel value of the reference image of the main scan.

For example, the pixel value of the addition result is set to the pixel value Px1 of the scanno shooting, and the tube current value of the scanno shooting is set to Ti1. Further, the pixel value of the reference image of the main scan is Px2, and the tube current value for the main scan is Ti2. At this time, there is the following relationship.

Px1: Ti1 = Px2: Ti2
Therefore, the tube current value Ti2 for this scan is estimated as shown in the following equation.

Ti2 = Ti1 x Px2 / Px1
As shown in FIG. 26, for example, the estimated tube current value Ti2 for the main scan is the position of the abdomen as compared with the solid line showing the tube current value for the main scan when the loss from the first scanno image is not taken into consideration. It shows a high value at z2. The same applies to the foot position zf illustrated in FIG. 26. However, since the foot portion illustrated in FIG. 26 is missing on one of the left and right sides, the difference value is added instead of adding half the value of the difference value. On the other hand, since the head position zh illustrated in FIG. 26 has no defect from the first scanno image, the solid line not considering the defect and the point considering the defect overlap. Further, although not shown, similarly, when other parts are also out of the irradiation range and are missing from the first scan image g11, the tube current value for the main scan of the other parts is estimated to be higher than the solid line. To.

After step ST6X, the processes after step ST6 are executed in the same manner as described above.

As described above, according to the third embodiment, when the contours on both the left and right sides of the subject protrude from the first scanno image, the position along the longitudinal direction corresponding to a part of the protruding contour is set. .. The X-ray tube is stationary at the set position, and the X-ray tube is placed at an angle within the X-ray irradiation range where the contours on both the upper and lower sides of the subject are within the angle around the rotation axis of the X-ray tube. X-ray photography is controlled so as to irradiate X-rays. Based on the output of the X-ray detector in the X-ray imaging, an X-ray image showing a part of the area of the subject is generated. The tube current value for the main scan at the set position is estimated based on the difference value between the pixel value of the first scanno image at the set position and the pixel value of the X-ray image.

Therefore, even if a first scanno image in which both sides of the subject are missing is obtained, the tube current value for this scan is determined using the X-ray image taken by X-ray at an angle that includes the contours of the upper and lower sides of the subject. Since it can be estimated, it is possible to prevent a decrease in the accuracy of AEC in this scan. Therefore, this scan can be appropriately executed even for a subject that is out of the imaging range during scanno imaging. Further, since the X-ray tube is kept stationary when the X-ray image is taken at an angle where the contours on both the upper and lower sides of the subject are included, the exposed area due to the X-ray image can be narrowed. Therefore, it is possible to reduce the exposure dose in X-ray imaging for estimating the tube current value for the subject outside the imaging range.

Further, according to the third embodiment, when estimating the tube current value, half the value of the difference value is added to the pixel value of the first scanno image, and the pixel value of the addition result is obtained. The tube current value for the main scan is estimated based on the pixel value of the addition result and the pixel value of the reference image of the main scan. Therefore, when the left and right sides of the subject are defective at the same ratio, the tube current value for this scan can be estimated by adding half the difference value.

Further, according to the third embodiment, since the steps ST1 to ST7 of the second embodiment can be executed, the effects of the second embodiment can be obtained together.

According to at least one embodiment described above, the first scannographing is controlled so as to irradiate X-rays while moving the top plate or the X-ray tube along the longitudinal direction of the top plate. Based on the output of the X-ray detector by the first scanno imaging, a first scanno image showing a part of the subject along the longitudinal direction is generated. Prior to the second scanno imaging in which the region including a part of the contour of the subject protruding from the first scanno image in the lateral direction of the top plate is photographed, a plurality of positions along the longitudinal direction are set. The second scanno imaging is controlled so that the X-ray tube is stationary and the X-ray is irradiated to the plurality of positions in order. Based on the output of the X-ray detector by the second scanno imaging, a plurality of second scanno images showing a region including a part of the contour are generated. The contour is estimated based on each of the first scanno image and the second scanno image.

Therefore, this scan can be appropriately executed even for a subject that is out of the imaging range during scanno imaging.

The word "processor" used in the above description is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an integrated circuit for a specific application (Application Specific Integrated Circuit (ASIC)), or a programmable logic device (for example). , Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). The processor realizes the function by reading and executing the program stored in the memory. Instead of storing the program in the memory, the program may be directly embedded in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit. It should be noted that each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, and a plurality of independent circuits may be combined to form one processor to realize its function. good. Further, a plurality of components in FIG. 1 may be integrated into one processor to realize the function.

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

1 X-ray CT device 10 Mount device 11 X-ray tube 12 X-ray detector 13 Rotating frame 14 X-ray high voltage device 15 Control device 16 Wedge 17 Collimator 18 DAS
30 Sleeper device 31 Base 32 Sleeper drive device 33 Top plate 34 Support frame 40 Console device
41 Memory 42 Display 43 Input interface 44 Processing circuit 441 System control function 442 Scan control function 443 Display control function 444 Image generation function 445 Image processing function P Subject g10, g11 1st scanno image g21, g22 2nd scanno image

Claims (9)

An X-ray tube that irradiates the subject placed on the top plate with X-rays,
An X-ray detector that detects X-rays that have passed through the subject,
A first control unit that controls first scanno imaging so as to irradiate the X-ray while moving the top plate or the X-ray tube along the longitudinal direction of the top plate.
A first generation unit that generates a first scanno image showing a part of the subject along the longitudinal direction based on the output of the X-ray detection unit by the first scanno imaging.
Prior to the second scanno imaging in which the region including a part of the contour of the subject protruding from the first scanno image in the lateral direction of the top plate is photographed, a plurality of positions along the longitudinal direction are set. Setting part and
A second control unit that controls the second scanno imaging so that the X-ray tube is stationary at the plurality of positions in order to irradiate the X-ray.
A second generation unit that generates a plurality of second scanno images showing a region including a part of the contour based on the output of the X-ray detection unit by the second scanno imaging.
An X-ray CT apparatus including an estimation unit for estimating the contour based on each of the first scanno image and the second scanno image. The estimation unit partially overlaps the first scanno image and the plurality of second scanno images, and connects a part of the contour included in the region indicated by each of the second scanno images with a line. The X-ray CT apparatus according to claim 1, wherein the contour is estimated accordingly. The setting unit sets each of the plurality of positions in association with the angle around the rotation axis of the X-ray tube.
The second control unit makes the X-ray tube stationary and irradiates the X-ray in a state where the X-ray tube is arranged at the angle corresponding to the stationary position, according to claim 1 or 2. X-ray CT device. When the contours on both the left and right sides of the subject protrude from the first scanno image, the setting unit separately separates a part of the contour on the right side of the subject and a part of the contour on the left side of the subject. The X-ray CT apparatus according to claim 3, wherein each of the plurality of positions and two angles around the rotation axis of the X-ray tube are set in association with each other so as to take an image. The setting unit sets each of the plurality of positions in association with the position in the lateral direction.
In the second control unit, the X-ray tube or the top plate is stationary at the plurality of positions in order, and the X-ray tube is opposed to the position in the lateral direction corresponding to the stationary position. The X-ray CT apparatus according to claim 1 or 2, wherein the X-ray is irradiated with the X-ray. When the contours on both the left and right sides of the subject protrude from the first scanno image, the setting unit separately separates a part of the contour on the right side of the subject and a part of the contour on the left side of the subject. The X-ray CT apparatus according to claim 5, wherein each of the plurality of positions and the two positions in the lateral direction are set in association with each other so as to take an image. An X-ray tube that irradiates the subject placed on the top plate with X-rays,
An X-ray detector that detects X-rays that have passed through the subject,
A first control unit that controls first scanno imaging so as to irradiate the X-ray while moving the top plate or the X-ray tube along the longitudinal direction of the top plate.
A first generation unit that generates a first scanno image showing a part of the subject along the longitudinal direction based on the output of the X-ray detection unit by the first scanno imaging.
When the contours of the left and right sides or both sides of the subject protrude from the first scanno image, a setting unit for setting a position along the longitudinal direction corresponding to a part of the protruding contours, and a setting unit.
The X-ray tube is stationary at the set position, and the X-ray tube is at an angle around the rotation axis of the X-ray tube so that the contours on both the upper and lower sides of the subject are within the irradiation range of the X-ray. An X-ray imaging control unit that controls X-ray imaging so as to irradiate the X-rays with the X-rays arranged.
An X-ray image generation unit that generates an X-ray image showing a part of a region of the subject based on the output of the X-ray detection unit in the X-ray imaging.
A tube current estimation unit that estimates the tube current value for the main scan at the set position based on the difference value between the pixel value of the first scanno image and the pixel value of the X-ray image at the set position. Equipped with X-ray CT device. The tube current estimation unit is
When the contours on both the left and right sides of the subject protrude from the first scanno image, half of the difference value is added to the pixel value of the first scanno image, and the pixel value of the addition result is obtained. ,
The X-ray CT apparatus according to claim 7, wherein the process of estimating the tube current value for the main scan is executed based on the pixel value of the addition result and the pixel value of the reference image of the main scan. It further includes a second control unit, a second generation unit, and an estimation unit.
The setting unit sets a plurality of positions along the longitudinal direction and sets a plurality of positions.
The second control unit controls the second scanno imaging so that the X-ray tube is stopped in order at the plurality of set positions and the X-ray is irradiated.
The second generation unit generates a plurality of second scanno images showing a region including a part of the contour based on the output of the X-ray detection unit by the second scanno imaging.
The X-ray CT apparatus according to claim 7, wherein the estimation unit estimates the contour based on each of the first scanno image and the second scanno image.

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