JP6255245B2 - X-ray CT apparatus and posture determination method - Google Patents

Description

  The present invention relates to an X-ray CT apparatus and a posture determination method, and more particularly, to a posture determination of a subject lying on a bed.

  Conventionally, in order to improve the CT examination workflow, there is a technique for collecting and analyzing information such as a physique and a posture of a subject lying on a bed and setting an imaging condition according to the posture of the subject. . For example, Patent Document 1 discloses a method for determining the posture of a subject based on a mark previously attached to the subject. In the method described in Patent Document 1, video information of a subject is collected by a camera, and the posture of the subject is determined by comparing the video information of the reference posture collected in advance with the current video.

JP 2011-45709 A

  However, when using the method disclosed in Patent Document 1 described above, it is necessary to remove the mark attached to the subject after the examination. For this reason, the work amount in CT inspection increases, and improvement of a workflow cannot be expected. In addition, although it is conceivable to use inspection clothes on which marks are printed in advance, it is necessary to prepare a large number of inspection clothes of a size and a design corresponding to the subject, which increases costs. Further, as described in Patent Document 1, in the method of collating the reference posture information collected in advance with the information on the current posture, the accuracy of posture determination is low when there is a large physique difference between adults and children. There is a risk of becoming. In addition, in order to improve the determination accuracy, it is conceivable to collect reference body position information according to the physique and body position as prior information, but it is necessary to collate the current body position information with all the previously collected reference body position information at the time of body position determination. Since this is necessary, there is a problem that the processing time becomes long.

  The present invention has been made in view of the above problems, and the object of the present invention is to determine the posture of a subject lying on a bed with high speed and high accuracy, and to improve the examination workflow. An object of the present invention is to provide an X-ray CT apparatus and a posture determination method.

In order to achieve the above-described object, the first invention provides the X-ray source that irradiates the subject with X-rays and the X-ray detector that detects the X-rays transmitted through the subject while facing each other. A scan gantry unit that irradiates X-rays from a plurality of angular directions around the subject and obtains transmitted X-ray data transmitted through the subject by the X-ray detector; and the subject in the scan gantry unit A bed that is carried into and out of the radiation irradiation space, a reconstruction processing unit that reconstructs a subject image using transmission X-ray data detected by the X-ray detector, and operations of the scan gantry unit and the bed. A control unit for controlling, a distance measuring device for measuring a distance from a predetermined measuring point to each point on the subject, and a subject from a predetermined reference point of the subject based on the distance measured by the distance measuring device. The body axis direction of the specimen and A distance distribution creating unit that creates a distance distribution in the width direction, a body posture determining unit that determines the posture of the subject based on the distance distribution, and a body posture setting unit that sets the body posture determined by the body posture determining unit as an imaging condition A body motion monitoring region setting unit that sets a monitoring region for monitoring the body motion of the subject based on the body position determined by the body position determining unit, and measuring the body motion in the monitoring region and measuring the body An X-ray CT apparatus comprising: a control unit that controls imaging based on motion .
According to a second aspect of the present invention, an X-ray source for irradiating a subject with X-rays and an X-ray detector for detecting X-rays transmitted through the subject are arranged to face each other at a plurality of angles around the subject. A scan gantry unit that irradiates X-rays from the direction and acquires transmitted X-ray data transmitted through the subject by the X-ray detector, and carries the subject in and out of an X-ray irradiation space in the scan gantry unit A bed, a reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector, a control unit for controlling operations of the scan gantry unit and the bed, and a predetermined unit A distance measuring device that measures the distance from the measurement point to each point on the subject, and the body axis direction and the body width of the subject from the predetermined reference point of the subject based on the distance measured by the distance measuring device Create distance distribution of directions A posture distribution determination unit, a posture determination unit that determines the posture of the subject based on the distance distribution, and a posture setting unit that sets the posture determined by the posture determination unit as an imaging condition. A first body position determination unit configured to determine an intermediate body position indicating a head direction of the subject based on a shape of a distance distribution in the body width direction; and the intermediate body position based on the distance distribution in the body axis direction. A second body position determination unit that determines which of the plurality of body positions is subdivided from the first body position, and the first body position determination unit calculates the distance distribution from the reference point in the body width direction. The X-ray CT apparatus is characterized in that it is multi-valued into a background part, a far part, and a near part based on the size of the image and determines the intermediate body position based on the number of the near part and the far part.
According to a third aspect of the present invention, a plurality of angles around the subject in a state where an X-ray source that irradiates the subject with X-rays and an X-ray detector that detects the X-rays transmitted through the subject are arranged to face each other. A scan gantry unit that irradiates X-rays from the direction and acquires transmitted X-ray data transmitted through the subject by the X-ray detector, and carries the subject in and out of an X-ray irradiation space in the scan gantry unit A bed, a reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector, a control unit for controlling operations of the scan gantry unit and the bed, and a predetermined unit A distance measuring device that measures the distance from the measurement point to each point on the subject, and the body axis direction and the body width of the subject from the predetermined reference point of the subject based on the distance measured by the distance measuring device Create distance distribution of directions A posture distribution determination unit, a posture determination unit that determines the posture of the subject based on the distance distribution, and a posture setting unit that sets the posture determined by the posture determination unit as an imaging condition. A first body position determination unit configured to determine an intermediate body position indicating a head direction of the subject based on a shape of a distance distribution in the body width direction; and the intermediate body position based on the distance distribution in the body axis direction. A second body position determination unit that determines which of the plurality of body positions to be subdivided from, wherein the second body position determination unit calculates the distance distribution from the reference point in the distance distribution in the body axis direction. The X-ray CT apparatus is characterized in that the body position is determined based on the size of the spread in the vicinity of the multi-valued distance distribution based on the multi-valued distance distribution.
According to a fourth aspect of the present invention, a plurality of angles around the subject in a state where an X-ray source that irradiates the subject with X-rays and an X-ray detector that detects the X-rays transmitted through the subject are arranged to face each other. A scan gantry unit that irradiates X-rays from the direction and acquires transmitted X-ray data transmitted through the subject by the X-ray detector, and carries the subject in and out of an X-ray irradiation space in the scan gantry unit A bed, a reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector, a control unit for controlling operations of the scan gantry unit and the bed, and a predetermined unit A distance measuring device that measures the distance from the measurement point to each point on the subject, and the body axis direction and the body width of the subject from the predetermined reference point of the subject based on the distance measured by the distance measuring device Create distance distribution of directions A posture distribution determination unit, a posture determination unit that determines the posture of the subject based on the distance distribution, and a posture setting unit that sets the posture determined by the posture determination unit as an imaging condition. A first body position determination unit configured to determine an intermediate body position indicating a head direction of the subject based on a shape of a distance distribution in the body width direction; and the intermediate body position based on the distance distribution in the body axis direction. And a second body position determination unit that determines which of the plurality of body positions is subdivided from, and determines whether the intermediate body position is leftward, rightward, left-handed, or right-handed in the first body position determination process. In this case, the second body position determination unit acquires the multi-valued body width direction distance distribution, and determines whether it is the foot side or the head side based on the size of the spread in the vicinity. X-ray CT apparatus.

According to a fifth aspect of the present invention, there is provided a step of measuring a distance to each point on the subject lying on a bed by a distance measuring device arranged at a predetermined measurement point, and a predetermined distance of the subject based on the measured distance The calculation device creates a distance distribution in the body axis direction and body width direction of the subject from the reference point, the step of the calculation device determining the posture of the subject based on the distance distribution, and the determined posture is photographed A step of setting as a condition, a step of setting a monitoring region for monitoring the body movement of the subject based on the body position determined by the step of determining the body position, a body movement in the monitoring region is measured and measured. And a step of controlling photographing based on the body movement .

  According to the present invention, it is possible to provide an X-ray CT apparatus and a posture determination method capable of determining the posture of a subject lying on a bed with high speed and high accuracy and improving the CT examination workflow.

External view showing the entire configuration of the X-ray CT apparatus 1 Hardware block diagram of X-ray CT apparatus 1 Functional configuration diagram regarding posture determination in the X-ray CT apparatus 1 Flow chart showing the overall flow of shooting processing Flow chart showing detailed procedure of tomographic pre-distance image photographing processing (pre-processing) The figure which shows the distance image in each step of the process of FIG. Flowchart explaining the procedure of the body position determination process The figure explaining acquisition of the nearest point 7 and the search range for creating the distance distribution Diagram explaining correction of range image The flowchart which shows the procedure of the posture determination 1st process in the posture determination process of FIG. The figure which shows the typical example of the distance distribution of each body position. (A) Head-side prone both hands raised, (b) Head-side supine hands raised, (c) Head-side supine hands down The figure which shows the typical example of the distance distribution of each body position. (A) Foot-side prone both-hands raised, (b) Leg-side-upped both hands raised, (c) Leg-side-upped both-hands lowered The figure which shows the typical example of the distance distribution of each body position. (A) Head-up, left-hand lift, (b) Head-left The figure which shows the typical example of the distance distribution of each body position. (A) Head-up, right-handed, (b) Head-right The figure which shows the typical example of the distance distribution of each body position. (A) Head side left, (b) Foot side left The figure which shows the typical example of the distance distribution of each body position. (A) Head side right, (b) Foot side right The flowchart which shows the procedure of the intermediate body position determination process in the body position determination 1st process of FIG. The flowchart which shows the procedure of the body position determination 2nd process in the body position determination process of FIG. A diagram explaining the discrimination of the head on its back, prone, and sideways The figure explaining discrimination of the posture of a foot The figure explaining adjustment of a bed position The flowchart which shows the procedure of the body posture determination 2nd process in 2nd Embodiment. Diagram showing the relationship between head posture and body axis direction distance distribution The flowchart which shows the flow of the imaging | photography process containing a body movement determination process The figure explaining the setting of the body movement monitoring area | regions 8a and 8b

[First embodiment]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, the hardware configuration of the X-ray CT apparatus 1 will be described with reference to FIGS. 1 and 2.

  The X-ray CT apparatus 1 includes a scanner 10 including a scan gantry unit 100 and a bed 101 and an operation unit 20. The scan gantry unit 100 includes an X-ray source 102, an X-ray detector 103, a collimator 104, a high voltage generation device 105, a data collection device 106, a drive device 107, and the like. The operation unit 20 includes a control device 200, an input / output device 201, an arithmetic device 202, and the like.

  The X-ray CT apparatus 1 of the present invention includes a distance measurement device 108 that measures the distance from a predetermined measurement point to each point on the subject 3. The distance measuring device 108 is configured by, for example, a depth camera that can measure position information (distance) in the depth direction. In the first embodiment, an example is shown in which the distance measuring device 108 is arranged on the upper part of the scan gantry unit 100 as shown in FIG. In the example of FIG. 1, the distance measuring device 108 is disposed obliquely above the bed 101, and the measurement point and each point on the subject 3 are set with the body axis direction of the subject 3 lying on the bed 101 as the depth direction. Get distance information between. The distance measuring device 108 outputs the measured distance information to the arithmetic device 202 of the operation unit 20.

  When a depth camera is used as the distance measuring device 108, the distance information is input as a distance image representing a distance value to each point in the field of view of the depth camera as a pixel value. The distance image is, for example, a gray scale image in which each pixel is expressed by shading according to the distance value. In the distance image, the distance value is expressed as, for example, a gradation of 256 gradations, such as “dark” gradually in the far direction and “light” gradually in the vicinity.

  The arrangement of the distance measurement device 108 (position of the measurement point) is not limited to the upper part of the scan gantry unit 100, and may be another position. Further, the distance measuring device 108 is not necessarily limited to the one configured integrally with the scan gantry unit 100. For example, the distance measurement device 108 and the scan gantry unit 100 may be separated and can be freely arranged at an arbitrary position. For example, the distance measuring device 108 may be arranged at the upper part of the bed 101 in the width direction. The distance information measured by the distance measuring device 108 is input to the arithmetic unit 202 of the operation unit 20 via a communication interface such as wiring or wireless communication.

  The input / output device 201 includes a display device 211, an input device 212, a storage device 213, and the like. The display device 211 displays the CT image reconstructed by the reconstruction processing device 221 and imaging conditions. The input device 212 is configured by a mouse, a keyboard, a touch panel, and the like, and sends imaging conditions, reconstruction conditions, and the like input by the operator to the control device 200. The storage device 213 includes a storage device 213 that stores various programs and data for realizing the functions of the X-ray CT apparatus 1, a CT image reconstructed by the reconstruction processing device 221, and the like. An operator inputs imaging conditions, reconstruction conditions, and the like via the input / output device 201. The imaging conditions include, for example, X-ray conditions such as X-ray beam width, tube current, tube voltage, an imaging range (body axis direction range), the number of imaging views per round, a bed feeding speed, and the like. The reconstruction condition is, for example, a region of interest, FOV (Field Of View), a reconstruction filter function, or the like.

  The control device 200 is a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The control device 200 generates various control signals necessary for photographing based on the photographing conditions and reconstruction conditions input by the input / output device 201 and transmits them to each unit of the scanner 10.

  The high voltage generator 105 applies and supplies a predetermined tube voltage and tube current to the X-ray source 102 in response to an imaging start signal transmitted from the control device 200. The X-ray source 102 emits X-rays having energy corresponding to the applied tube voltage. The collimator device 104 controls the position of the collimator based on the control signal transmitted from the control device 200, and limits the irradiation range of the X-rays irradiated from the X-ray source 102.

  The driving device 107 rotates the rotating disk of the scan gantry unit 100 around the subject 3 based on the control signal transmitted from the control device 200. The bed 101 adjusts the height of the bed and the position of the top plate based on the control signal transmitted from the control device 200, and carries the subject 3 into and out of the X-ray irradiation space (opening 99).

  X-rays irradiated from the X-ray source 102 and absorbed (attenuated) according to the X-ray attenuation coefficient in each tissue in the subject 3 are transmitted through the subject 3 and detected by the X-ray detector 103. The X-ray detector 103 includes a plurality of detection elements arranged in a two-dimensional direction (a channel direction and a column direction orthogonal thereto). The X-ray signal detected by each detection element of the X-ray detector 103 is converted into digital data by the data collection device 106 and sent to the arithmetic device 202 as transmitted X-ray data.

  The arithmetic device 202 includes a reconstruction processing device 221 and an image processing device 222.

  The reconstruction processing device 221 acquires transmission X-ray data collected by the data processing device 106, and performs various data processing such as LOG conversion and calibration to create projection data necessary for reconstruction of a tomographic image. . The reconstruction processing device 221 reconstructs a tomographic image (CT image) of the subject 3 using the projection data.

  Note that the reconstruction processing device 221 may perform reconstruction processing of a tomographic image or the like based on projection data acquired by imaging and stored in the storage device 213 or a recording medium.

  The reconstruction processing device 221 stores the generated CT image in the storage device 213 and displays it on the display device 211. The image processing device 222 performs image processing on the tomographic image stored in the storage device 213. For example, another subject image is generated using a tomographic image or the like stored in the storage device 213. The image processing device 222 displays the generated subject image on the display device 211 and stores it in the storage device 213.

  The bed 101 includes a top plate on which the subject 3 is placed, a vertical movement device, and a top plate drive device. The control device 200 controls the top plate height up and down, and the top plate in the body axis direction. Move back and forth, or move left and right in the direction perpendicular to the body axis and parallel to the floor (left and right direction). The control device 200 adjusts the bed position based on the posture information determined by the posture determination process described later. During photographing, the couchtop is moved at the bed moving speed determined by the photographing conditions.

  Next, the functional configuration of the X-ray CT apparatus 1 of the present invention will be described with reference to FIG. FIG. 3 particularly shows functional configurations of the arithmetic device 202 and the control device 200.

  The X-ray CT apparatus 1 according to the present invention includes, as main functions, a reference point determination unit 41, a body width direction distance distribution creation unit 42, a body axis direction distance distribution creation unit 43, a first body position determination unit 44, and a second body position. It has the determination part 45, the body posture setting part 46, and the bed position adjustment part 47. The reference point determination unit 41, the body width direction distance distribution creation unit 42, the body axis direction distance distribution creation unit 43, the first body position determination unit 44, and the second body position determination unit 45 are provided in, for example, the arithmetic device 202. In addition, the body position setting unit 46 and the bed adjustment unit 47 are provided in the control device 200, for example.

  Distance information from a predetermined measurement point to each point of the subject 3 lying on the bed 101 is measured by the distance measurement device 108. The measured distance information is input to the reference point determination unit 41, the body width direction distance distribution creation unit 42, and the body axis direction distance distribution creation unit 43 of the arithmetic device 202. The distance information is, for example, a distance image taken by a depth camera (distance measuring device 108).

  The reference point determination unit 41 determines a reference point on the subject 3 based on the acquired distance information. As in the present embodiment, when the distance measuring device 108 is arranged on the upper part of the scan gantry unit 100 and the distance is measured with the longitudinal direction of the bed 101 as the depth direction, the closest point between the distance measuring device 108 and the subject 3 is measured. It is desirable to use 7 (see FIG. 8) as a reference point. The reference point determination unit 41 searches for the nearest point 7 (reference point) from the distance image input from the distance measuring device 108. The reference point determination unit 41 notifies the body width direction distance distribution creation unit 42 and the body axis direction distance distribution creation unit 43 of the position information of the searched nearest point 7.

  The body width direction distance distribution creating unit 42 creates a body width direction (horizontal direction orthogonal to the body axis) distance distribution from the distance information based on the reference point (nearest point 7) determined by the reference point determining unit 41. Then, the first body position determination unit 44 and the second body position determination unit 45 are notified. The body width direction distance distribution is a two-dimensional graph in which the horizontal axis indicates the position in the body width direction from the reference point, and the vertical axis indicates the distance value from the measurement point.

  The body axis direction distance distribution creation unit 43 creates a body axis direction distance distribution from the distance information with reference to the reference point (nearest point 7) determined by the reference point determination unit 41, and the first body position determination unit 44 and The second body position determination unit 45 is notified. The body axis direction distance distribution is a two-dimensional graph in which the horizontal axis indicates the position in the body axis direction from the reference point, and the vertical axis indicates the distance value from the measurement point. In the body axis direction distance distribution, when the positive direction of the horizontal axis is a direction away from the reference point, it is called a far direction body axis direction distance distribution. In addition, when the positive direction of the horizontal axis is a direction from the reference point toward the vicinity, it is referred to as a near body axis direction distance distribution.

  The first body position determination unit 44 determines which intermediate body position the subject 3 corresponds to based on the shape of the body width direction distance distribution notified from the body width direction distance distribution creation unit 42. The intermediate body position indicates the direction of the head of the subject 3, the body position close to the head with respect to the scan gantry unit 100 is “head side”, and the body position with the head far from the scan gantry unit 100 is “ In the case of foot side, lying down, it is “right” or “left”. In addition to these, “single-handed (right-handed, left-handed)” may be added to the intermediate position. The first body position determination unit 44 notifies the second body position determination unit 45 of the determined intermediate body position information.

  Based on the body width direction distance distribution notified from the body width direction distance distribution creation unit 42 and the body axis direction distance distribution notified from the body axis direction distance distribution creation unit 43, the second body position determination unit 45 starts from the intermediate body position. Further, it is determined which of the plurality of subdivided positions is applicable. The second posture determination unit 45 notifies the posture setting unit 46 of the determined posture information. When the intermediate body position is determined to be “head side”, the second body position determination unit 45 further determines “head side depression” and “head side supine”. When the intermediate body position is determined to be “foot side”, the second body position determination unit 45 further determines “foot side prone” and “foot side supine”. When it is determined that the intermediate position is laterally (or raised by one hand), the second body position determination unit 45 performs “head side left hand lift”, “head side right hand lift”, “head side left facing”, “head side right facing”. "," Foot side leftward ", and" foot side rightward "are further determined.

The posture setting unit 46 sets the posture information notified by the second posture determination unit 45 as a photographing condition.
The couch position adjustment unit 47 acquires the couch movement amount calculated based on the body position information notified by the second body position determination unit 45 from the arithmetic unit 202, and moves the height position and the horizontal position of the couch 101. .

  Next, with reference to FIG. 4, an overall flow of imaging processing executed by the X-ray CT apparatus 1 according to the present invention will be described.

  Prior to tomographic imaging, the X-ray CT apparatus 1 first acquires distance information of the subject 3 using the distance measuring device 108 (step S101). The distance information is information indicating the distance from a predetermined measurement point (the position of the distance measurement device 108) to each point on the subject 3. For example, when a depth camera is used as the distance measuring device 108, the distance measuring device 108 (depth camera) acquires a distance image having distance values from the measurement point to each point in the camera visual field as pixel information.

  In step S <b> 101, it is desirable that the distance measuring device 108 captures a moving image of the subject 3 lying on the bed 101 and monitors the movement of the subject 3 to the bed 101 from the time change of the distance image. Among the acquired moving images, the arithmetic device 202 has a frame (no subject) in a state where the subject 3 is not present (a state where only the bed 101 is photographed) from a frame where the subject 3 is photographed (distance image 50 with the subject). The distance image 51) is subtracted, and a distance image (only the subject distance image 52) obtained by capturing only the subject 3 is extracted. In the distance distribution creation processing and the like after this step, only the subject is processed using the distance image 52.

  The arithmetic unit 202 creates and analyzes the distance distribution in the body width direction and the body axis direction of the subject 3 from the distance image 52 only for the subject acquired in step S101, and performs body position determination processing (step S102). In the body posture determination process in step S102, the body posture of the subject 3 is changed to a representative body posture in CT examination (for example, head-side-up, head-side-down, foot-side-up, foot-side-down, head-side left-hand lift, head-side right-hand lift). , Head side left direction, head side right direction, foot side left direction, foot side right direction). The arithmetic device 202 stores the determined body position information in the storage device 213 and outputs it to the control device 200. The storage device 213 acquires the posture information of the subject 3 to be examined and holds it until the examination of the subject 3 is completed. Details of the posture determination process will be described later (FIGS. 7 to 21).

  The control device 200 acquires the posture information determined in step S102, and the orientation of the body axis direction of the subject 3 is the head side or the foot side with respect to the scan gantry unit 100 according to the obtained body position information of the subject 3. Whether the subject 3 is lying on his back, lying down, facing left, or facing right is set as an imaging condition of the X-ray CT apparatus 1 (step S103).

  In addition, the arithmetic device 202 calculates the couch movement amount based on the posture information of the subject 3 determined in step S102 and notifies the control device 200 of it. The control device 200 adjusts the vertical position and horizontal position of the bed 101 based on the movement amount notified from the arithmetic device 202 (step S104).

  After that, when various imaging conditions such as X-ray conditions such as X-ray tube voltage, X-ray tube current, imaging range, gantry rotation speed, bed speed, helical pitch, reconstruction FOV, reconstruction slice thickness are set, The control device 200 starts tomographic image capturing (step S105).

  In step S105, the control device 200 controls the operation of each unit of the scan gantry unit 100 and the bed 101 based on the set imaging conditions. The high voltage generator 105 supplies power to the X-ray source 102 under the control of the control device 200. Further, the driving device 107 rotates the turntable in accordance with photographing conditions such as a rotation speed. During shooting, the bed 101 is moved based on shooting conditions such as the bed speed (spiral pitch).

  X-ray irradiation from the X-ray source 102 and transmission X-ray data measurement by the X-ray detector 101 are repeated as the rotating disk rotates. The data collection device 106 acquires transmission X-ray data measured by the X-ray detector 101 at various angles (views) around the subject 3 and sends it to the reconstruction processing device 221 of the arithmetic device 202. The reconstruction processing device 221 reconstructs a tomographic image or the like of the subject 3 based on the transmitted X-ray data, stores it in the storage device 213 and displays it on the display device 211.

  When the tomographic image capturing is completed, the control device 200 instructs the distance measuring device 108 to capture the distance image. The distance measuring device 108 captures a distance image of the subject 3 lying on the bed 101. Based on the distance image, distance information to each point of the subject 3 is collected (step S106). The control device 200 monitors how the subject 3 moves down from the bed 101 and moves from the time change of the distance information. When the subject 3 moves away from the bed 101, a series of imaging processes is terminated.

  Next, details of the distance image capturing process before tomography in step S101 and the body posture determination process in step S102 will be described with reference to FIGS. In the first embodiment, a depth camera attached to the upper part of the scan gantry 100 near the opening 99 is used as the distance measuring device 108. The depth camera captures a distance image of the subject 3 lying on the bed 101. The distance image includes distance information in the depth direction from the position (measurement point) of the depth camera to each point of the subject (including the subject 3 and the bed 101).

  In order to improve the accuracy of body posture determination, it is desirable to perform a pre-processing for extracting only the subject 3 by deleting the background (the bed 101 or the scan gantry unit 100) other than the subject 3 from the distance image.

  With reference to FIG. 5 and FIG. 6, preprocessing (distance image photographing processing before tomography) will be described. 6A, 6 </ b> B, and 6 </ b> C show distance images obtained when the bed 101 is photographed from the distance measuring device (depth camera) 108 disposed on the upper portion of the scan gantry unit 100. ing. As an example of the body posture, a state in which the subject 3 is leaning on his / her back with his head facing the opening 99 of the scan gantry unit 100 is shown. In FIG. 6, a diagram in the form of a diagram is used, but the actual distance image is a gray scale image or the like having light and shade according to the distance value.

  In the preprocessing (distance image capturing process before tomography) shown in FIG. 5, the control device 200 captures the distance image 50 without the subject using the distance measuring device 108 (step S201). The no-subject distance image 50 is a moving image obtained by photographing the periphery of the bed before the subject 3 to be examined enters the examination room (before the subject 3 touches the bed 101). FIG. 6A shows a distance image 50 at a certain moment (one frame) of the moving image. By the processing in step S201, the arithmetic unit 202 obtains a subject-free distance image 50 including distance information to the bed 101 and distance information to the background. The no-subject distance image 50 is temporarily held in the recording device 213 until the examination of the subject 3 is completed.

  Next, the computing device 202 monitors the operation of the subject 3 based on the moving image of the distance image (step S202). For example, the arithmetic unit 202 obtains a time difference (interframe difference) of moving images from the subject-less distance image 50 as a starting point, and monitors the movement operation of the subject 3 to the bed 101. If the change in the difference between the previous and subsequent frames is greater than or equal to a certain amount within a certain time, it is determined that the subject is moving to the bed and monitoring is continued. When the change in the difference between frames becomes a certain amount or less and a certain amount of time has elapsed, it is determined that the subject 3 is standing on the bed 101 and is in a stationary state, and monitoring is terminated.

  The arithmetic unit 202 captures a moving image of the distance image around the bed while the subject 3 is lying on the bed 101, and acquires the distance image 51 with the subject (step S203). FIG. 6B shows a distance image at a certain moment (one frame) of the distance image 51 with the subject. By the processing in step S202, the arithmetic unit 202 obtains the subject distance image 51 including the distance information to the bed 101, the distance information to the background, and the distance information to the subject 3. The subject presence distance image 51 is temporarily held in the recording device 213 until the examination of the subject 3 is completed.

  The computing device 202 extracts the distance image 52 only for the subject from the difference between the distance image 50 without the subject and the distance image 51 with the subject. FIG. 6C shows an example of the distance image 52 only for the subject. The subject-only distance image 52 is temporarily held in the recording device 213 until the examination of the subject 3 is completed. Posture determination processing is performed based on the image 52 only for the subject 3.

  FIG. 7 is a flowchart showing the procedure of the body position determination process in step S102 of FIG. With reference to FIGS. 7 to 21, the posture determination process executed by the arithmetic unit 202 of the X-ray CT apparatus 1 will be described.

  First, the arithmetic unit 202 determines a reference point from the distance image 52 only for the subject. In the first embodiment, the closest point 7 is set as a reference point (step S301). The closest point 7 is a point where the distance from the measurement point (distance measuring device 108) to the subject 3 is the closest. The arithmetic unit 20 performs body posture determination processing using the closest point 7 searched in step S301 as a reference point for posture determination.

  In step S301, as shown in FIG. 8, only the subject, for example, the lower half area (area below the dotted line A in FIG. 8) of the distance image 52 is set as the closest point search range. In this embodiment, since the distance measuring device 108 is installed in the scan gantry unit 100, the lower side of the distance image is an area close to the measurement point. Therefore, the closest point search range is sufficient to determine the body position if the search range is a predetermined range closer to the measurement point in the entire range of the distance image. Further, the processing can be speeded up by narrowing the search range to some extent.

  The arithmetic unit 202 sets the point closest to the depth camera 108 within the closest point search range as the closest point 7 (x mark in FIG. 8). The closest point 7 is a point having the smallest pixel value on the distance image 52 only for the subject. However, it is assumed that the distance value is larger than “0”.

  When the head is directed toward the scan gantry unit 100 (hereinafter referred to as “head side”), the closest point 7 is the head, and the foot is directed toward the scan gantry unit 100 ( (Hereinafter referred to as “foot side”), the closest point 7 is the foot.

  By the processing in step S301, the nearest point 7 can be found on either the head or the foot regardless of the physique and posture of the subject 3. FIG. 8A shows the distance image 52 only for the subject for adults, and FIG. 8B shows the distance image 52a only for the subject for children.

  Next, the computing device 202 sets the body posture determination area 75 (step S302). This is a process for increasing the accuracy of posture determination. For example, only the subject uses the peripheral portion of the closest point 7 of the distance image 52 as the body posture determination region 75.

  As shown in FIG. 8, when there is only one nearest point 7 included in the subject-only distance image 52, a distance image (a subject-only distance image is displayed with a straight line in the body width direction passing through the nearest point 7 as a reference line 71. 52) and the range of the mirror image (the range below the broken line B in FIGS. 8A and 8B) are set in the body posture determination region 75.

  When there are a plurality of nearest points (nearest points 7a and 7b) as shown in FIG. 9A, the arithmetic unit 202 first obtains the center-of-gravity point 7c of the nearest points 7a and 7b. Next, a straight line passing through the closest points 7a and 7b and the centroid point 7c (referred to as a centroid line 73) is obtained. An approximate straight line may be obtained by a least square method or the like. Then, coordinate conversion of the distance image (only the subject 3 image 53) is performed and corrected based on the centroid point 7c and the centroid line 72. That is, a straight line in the body axis direction (body axis direction of the subject 3) passing through the center of gravity 7c is translated so as to be in the center of the image, and the center of gravity line is horizontal with the body width direction about the center of gravity 7c. Move so that it rotates. The distance values from the measurement points of the closest points 7a 'and 7b' after the coordinate conversion are the average values of the closest points 7a and 7b before the coordinate conversion. Based on the change amount of the position of the nearest points 7a 'and 7b' and the change amount of the distance value, the position and distance value of other pixels are corrected. The conversion coefficient used for coordinate conversion is temporarily held in the recording device 213 until the inspection is completed.

  In the following description, unless otherwise specified, processing is performed on the body position determination area 75.

When the posture determination region 75 is set by the process of step S302, the arithmetic device 202 performs a posture determination first process using information in the posture determination region 75 (step S303).
In the first body posture determination process, the computing device 202 determines an intermediate body posture that represents the orientation of the head based on the distance distribution of the subject 3 in the body width direction. Specifically, the intermediate positions include four types of head side, foot side, right direction, and left direction with respect to the scan gantry unit 100. Furthermore, it is good also as 6 ways which added 2 ways of head side right hand raising and head side left hand raising to these 4 types of intermediate posture groups.

FIG. 10 shows a processing flow of the first body posture determination process.
In the first body posture determination process, the arithmetic unit 202 first creates a body width direction distance distribution from the distance image 52 of only the subject (step S401).

  Next, the arithmetic unit 202 ternizes the body width direction distance distribution created in step S401 (step S402). This is a process for speeding up and stabilizing the posture determination process. In step S402, the arithmetic unit 202 performs threshold processing on the distance distribution in the body width direction created in step S401, and ternizes the background part to “0”, the far part to “1”, and the neighboring part to “2”. . The threshold value for the ternarization processing may be a preset value, or may be set for each subject 3 based on the maximum value and the minimum value of the distance values of the distance distribution.

As an example of the ternary body width direction distance distribution according to the body position of the subject 3, FIG. 11 (a) head-side prone both-hands raising, FIG. 11 (b) head-side supine raising, FIG. 11 (c) head-side 12 (a) Foot-side prone both-hands raised, FIG. 12 (b) Foot-side supine both-hands raised, FIG. 12 (c) Foot-side supine both-hands lowered, FIG. 13 (a) Head-side supine left-hand raised, FIG. (B) Head-to-left, FIG. 14 (a) Head-up, right-hand lift, FIG. 14 (b) Head-to-right, FIG. 15 (b) Foot-side left, FIG. Indicates.
In each body width direction distance distribution shown in FIGS. 11 to 16, the positive direction of the vertical axis is the vicinity direction from the measurement point. The horizontal axis represents the position in the body width direction (left and right) with the closest point 7 as the center.

  The arithmetic unit 202 estimates the intermediate body position from the shape of the body width direction distance distribution ternarized in step S402 (step S403). The detailed procedure of the intermediate body position determination process is shown in the flowchart of FIG.

  As shown in FIG. 17, the arithmetic unit 202 first determines the number of “mountains” in the ternary body width direction distance distribution (step S <b> 501). A “mountain” represents a region that is not a background portion in the body width direction distance distribution. That is, in the ternary body width direction distance distribution, a group of areas (distant part) with a value of “1” and a group of areas (near part) with a value of “2” are counted as one “mountain”. . The arithmetic unit 202 counts the number of “mountains”.

  For example, the number of “mountains” is 3 in the head-side double-handed position in FIGS. 11A and 11B, and the number of “mountains” is 1 in the head-side double-handed position in FIG. It is a piece. Each “mountain” corresponds to the head, right hand, and left hand. That is, when the number of “mountains” is one or three, the intermediate position is determined as “head side” (step S501; one or three).

  In the case where there is one “mountain”, various postures can be considered as the posture, but in the X-ray CT apparatus 1 of the present invention, a special posture that is not taken by normal CT examination (a posture that makes the foot contact) For example, the case where the toes of the foot are brought into contact with the back of the foot, the foot of the foot is brought into contact with the prone side of the foot, etc. is not treated. Therefore, when there is one “mountain” in the distance distribution in the body width direction, the “mountain” corresponds to the head, so it can be estimated as “the head side”.

  If there are two “mountains” (step S501; two), the process proceeds to step S502.

  When the number of “mountains” is two in the determination in step S501, the arithmetic unit 202 counts the number of nearest points 7. As illustrated in FIGS. 11 to 16, when there are two “mountains” and the number of nearest points 7 (7a, 7b) is two (step S502; two), each “mountain” Corresponds to the right foot. Therefore, the intermediate position can be determined as “foot side”. As shown in FIGS. 12A to 12C, FIG. 15B, and FIG. 16B, there are two “mountains” on the foot side.

  If it is determined in step S502 that the number of closest points 7 is 1, the process proceeds to step S503. In step S503, the arithmetic unit 202 determines the height of each of the two “mountains” (step S503).

  In step S503, when the heights of the “mountains” are approximately the same (step S503; approximately the same), there are two objects at the same distance from the measurement point. It corresponds to the right foot and the left foot. Therefore, the intermediate position is determined as “foot side”.

  When one of the two “mountains” is high, there is a head near the measurement point, the “mountain” on the higher side corresponds to the head, and the “mountain” on the lower side corresponds to the arm. Therefore, when the “mountain” on the left side is higher (step S503; the left side is higher), the intermediate position is “rightward (FIG. 14 (b))” or the head side is raised to the right (FIG. 14 (a)). Is determined. If the “mountain” on the right side is higher (step S503; the right side is higher), the intermediate position is “leftward (FIG. 13 (b))” or head-left-hand raised (FIG. 13 (a)). Is determined.

  If it is determined in step S501 that there are more than three “mountains” or zero (step S501; otherwise), the process proceeds to step S504. In step S504, the control device 200 causes the distance image to be measured again. Thereafter, the arithmetic unit 202 repeats the first body posture determination process in step S403 based on the re-measured distance image. If the intermediate posture cannot be obtained after a plurality of trials, the operator is notified that the posture cannot be determined.

  When the intermediate posture is obtained by the intermediate posture determination process, the arithmetic unit 202 next executes a posture determination second process (step S304 in FIG. 7). In the second posture determination process, the arithmetic device 202 further subdivides the posture of the subject 3 using the intermediate posture information obtained by the first posture determination process and the distance distribution in the body axis direction of the subject 3. To determine. The postures determined in the posture determination second process are, for example, “head-side-up”, “head-side-down”, “foot-side-up”, “foot-side-down”, “head-side left-handed”, “head-side-right-handed”, It is assumed to include 10 types of "head side left", "head side right", "foot side left", and "foot side right".

FIG. 18 shows a detailed procedure of the body posture determination second process.
As shown in FIG. 18, in the posture determination second process, the arithmetic unit 202 acquires the result of the posture determination first process, and performs a process according to the acquired intermediate posture of the subject 3.

As a result of the first body determination process, when the intermediate body position is determined to be “head side”, the arithmetic unit 202 performs the processes of steps S601 to S604.
First, in order to create the body axis direction distance distribution, the arithmetic unit 202 acquires the same non-subject distance image 52 as the image in which the intermediate body position is determined as “head side” in the body position determination first process in step S303 (step S303). S601).

  Next, the computing device 202 creates a body axis direction distance distribution in the far direction from the subject-less distance image 52 acquired in step S601 (step S602). The body axis direction distance distribution in the far direction represents the positive direction of the horizontal axis from the reference point (nearest point 7) to the far direction in the body axis direction, and the vertical axis as the distance value from the measurement point. As shown in FIG. 19, the arithmetic unit 202 is arranged in a straight line passing through the nearest point 7 and parallel to the body axis direction (body axis direction of the subject 3) in the direction from the nearest point 7 toward the far side of the depth camera 108. Collect the distance value from the measurement point of the point, and create the distance direction body axis direction distance distribution.

  The computing device 202 converts the far direction body axis direction distance distribution into three values (step S603). The ternarization processing in step S603 is ternarized into a near portion “2”, a far portion “1”, and a background portion “0” by threshold processing in the same manner as in step S402 in the posture determination first processing in FIG. . The threshold value in step S603 may be a preset value, or may be set for each subject 3 based on the maximum value and the minimum value of the distance values of the distance distribution.

  The computing device 202 evaluates the size of the vicinity of the measurement point based on the ternarized far body axis direction distance distribution obtained in step S603 (step S604). The size of the neighborhood is the spread in the body axis direction of the pixel (neighboring portion) whose ternary body axis direction distance distribution value is “2”, and is the length of the arrows 76, 77, and 78 shown in FIG. It is represented by The sizes 76, 77, and 78 of the vicinity are determined by threshold processing, for example. Since step S604 is processing performed when the closest point 7 is near the upper side of the head, the vicinity here corresponds to the head. As the threshold value of the threshold processing in step S604, a value set in advance may be used, or a value calculated from the ratio between the size of the vicinity and the size of the far portion may be used.

  As shown in FIG. 19A, when the nose of the subject 3 is included in the vicinity, the size 76 of the vicinity is larger than when the nose is not included. Therefore, when the neighborhood portion is larger than the threshold value in the neighborhood size determination process in step S604 (step S604; greater than the threshold value), the arithmetic unit 202 determines that the body posture is “head-to-back”. As shown in FIG. 19B, when the size 77 of the vicinity is equal to or smaller than the threshold (step S604; equal to or smaller than the threshold), it is determined as “head-side depression”.

If the intermediate posture is determined to be “foot side” as a result of the first posture determination process, the arithmetic unit 202 performs the processes of steps S611 to S614 in FIG.
First, in order to create the body axis direction distance distribution, the arithmetic unit 202 acquires the same non-subject distance image 52 as the image in which the intermediate body position is determined as “head side” in the body position determination first process in step S303 (step S303). S611).

  Next, the computing device 202 creates a body axis direction distance distribution in the vicinity direction (step S612). The body axis direction distance distribution in the near direction represents the positive direction of the horizontal axis from the reference point (nearest point 7) to the near direction in the body axis direction, and the vertical axis as the distance value from the measurement point. As shown in FIG. 20, the arithmetic unit 202 is arranged in a straight line passing through the closest point 7 and parallel to the body axis direction (the body axis direction of the subject 3) in the direction from the nearest point 7 to the distance measuring device 108. Collect distance values at points and create a near body axis direction distance distribution.

  The computing device 202 binarizes the near-direction body axis direction distance distribution by threshold processing (step S613). The binarization process of step S613 is a process performed for speeding up and stabilizing the posture determination process. For example, binarization is performed such that the background portion is “0” and the neighboring portion is “1”. The threshold value in step S613 may be a preset value, or may be set based on the maximum value and the minimum value of the distance values of the distance distribution.

  The computing device 202 calculates the size of the neighborhood (the one closer to the distance measuring device 108) based on the binarized near body axis direction distance distribution obtained in step S613 (the length of the arrows 79, 80, 81). Is evaluated (step S614). Since step S614 is a process that is performed with the intermediate body posture performed on the foot side, the vicinity corresponds to the foot, and the nearest point 7 is the foot sole region (FIG. 20 (a)) and the foot instep region (FIG. 20). (B)), any of the toe periphery (FIG. 20 (c)). The evaluation in step S614 is performed by threshold processing, for example. As the threshold value in step S614, a value set in advance may be used, or a value calculated based on the ratio between the size of the near portion and the size of the far portion may be used.

  As shown in FIG. 20 (a), when the vicinity of the heel of the subject 3 is the nearest point 7, since the vicinity from the heel to the toe portion is included in the vicinity, the size (spread) of the vicinity 79 increases. As shown in FIG. 20C, when the vicinity of the toe of the subject 3 is the closest point 7, since only the toe is included in the vicinity 80, the size (spread) of the vicinity 80 is reduced. As shown in FIG. 20B, when the vicinity of the instep of the subject 3 is the closest point 7, the instep and the toe of the foot are included in the vicinity 81, so the size of the vicinity 81 ( The spread) is smaller than that in the case where the nearest point 7 is a heel (FIG. 20A), and is larger than that in the case where the nearest point 7 is a toe (FIG. 20C). Therefore, the threshold value in step S614 may be set so that the case where the closest point 7 is a foot heel (FIG. 20A) and the other points (FIGS. 20B and 20C) can be distinguished. When the size (spread) of the vicinity is larger than the set threshold, the body position of the subject 3 can be determined for foot-side prone, and when it is equal to or less than the threshold, the position of the subject 3 can be determined.

  As a result of the first posture determination process, if the intermediate posture is determined to be any one of “leftward / rightward / left-handed / right-handed”, the arithmetic unit 202 performs the processes of steps S621 to S626 in FIG.

  First, the arithmetic unit 202 obtains a body width direction ternary distance distribution in which the intermediate body position is determined as one of “leftward / rightward / left-handed / right-handed” in the first body posture determination process of step S303 (step S621). The body width direction ternary distance distribution is calculated in step S402 of FIG.

  Next, the computing device 202 evaluates the size of the vicinity based on the ternary distance distribution in the body width direction (step S622). In step S622, the nearest point 7 is a point near the upper side of the head or near the foot, and the vicinity corresponds to the head or the foot. The evaluation in step S622 is performed by, for example, a predetermined threshold process. As the threshold value, a value set in advance may be used, or a value calculated based on a ratio between the size of the vicinity portion and the size of the far portion may be used.

  As shown in FIGS. 15 (a) and 16 (a), when the closest point 7 is the head, the body width compared to the case where it is not the head (in the case of the foot; FIGS. 15 (b) and 16 (b)) The spreads 82 and 84 in the vicinity (measurement point side) of the direction ternary distance distribution are increased. Therefore, when the size of the spread in the vicinity is equal to or smaller than the threshold value in the threshold processing in step S622 (the arrow 83 in FIG. 15B and the arrow 85 in FIG. 16B), the posture of the subject 3 is the foot side left Determined to be directed or to the right side of the foot.

  If the size of the vicinity is larger than the threshold value in the threshold processing in step S622, the head is left (right) facing up and the head left (right) is raised. The arithmetic device 202 performs the processing of step S623 to step S626 to determine whether the hand is raised or sideways. Note that the left and right sides of the body have already been determined in step S503 of the intermediate body position determination process in FIG.

  The processes in steps S623 to S626 are the same as those in steps S601 to S604. However, the threshold value used in the size determination in step S626 may be set to a value different from the threshold value used in step S504.

  As shown in FIG. 19 (c), when the subject 3 is sideways, the nose of the subject 3 is not included in the vicinity of the distance direction body axis direction distance distribution. When the nose of the subject 3 is included in the vicinity, the expansion of the vicinity in the distant body axis direction distance distribution is larger than when the nose is not included (see FIG. 19A). Therefore, similarly to the determination in step S604, it can be determined that the vicinity of the distant body axis direction distance distribution is larger than a predetermined threshold value, and when it is equal to or less than the threshold value, it is determined to be horizontal direction. Here, the supine posture is a head-side raised posture.

  When the posture is determined by the above-described series of posture determination processes, the arithmetic device 202 notifies the control device 200 of the determined posture information. The control device 200 adjusts the bed position based on the body position information (step S104 in FIG. 4).

The bed position adjustment in step S104 will be described with reference to FIG.
The control device 200 first determines the difference distance between the mounting angle of the distance measuring device 108, the distance from the distance measuring device 108 to the nearest point 7, and the distance from the distance measuring device 108 to the point on the bed 101 corresponding to the nearest point 7. The body thickness of the subject 3 in the vicinity of the nearest point 7 is calculated. The control device 200 adjusts the bed position in the vertical direction so that the center of the calculated body thickness becomes the imaging center.

  Next, the control device 200 sets a bed position adjustment point 86 in the left-right direction (body width direction) according to the body position information with the closest point 7 as a reference. The bed position adjustment point in the left-right direction may be determined according to the body position information of the subject 3 and the imaging region. For example, when the posture of the subject 3 is head-to-back, it is set near the chest. The control device 200 adjusts the couch position in the left-right direction with reference to the coordinates of the couch position adjustment point 86 in the left-right direction within the camera field of view (within the measurement range of the distance measuring device 108). The control device 200 notifies the bed 101 of the movement amount of the bed 101.

  When the bed position is adjusted so that the bed position adjustment point 86 corresponding to the body position information is centered, the control device 200 starts tomographic image capturing (step S105 in FIG. 4).

  When the tomographic image capturing is completed, the control device 200 captures a distance image using the distance measuring device 108 (step S106 in FIG. 4). The control device 200 monitors the movement operation of the subject 3 from the bed 101 by photographing in step S106. If the change in the difference between the previous and subsequent frames is greater than or equal to a certain amount within a certain time, it is determined that the couch moving operation of the subject 3 is continuing and monitoring is continued. When the change becomes a certain amount or less and a certain time has elapsed, it is determined that the subject 3 has moved from the bed 101 and left the examination room, and the monitoring is terminated. When it is determined that the subject 3 has left the examination room, the control device 200 returns the state of each unit to the initial state for the next examination, and ends a series of imaging processes.

  As described above, the X-ray CT apparatus 1 according to the first embodiment is provided on the subject 3 lying on the bed 101 by the distance measuring device 108 arranged at a predetermined measurement point, such as the upper part of the scan gantry unit 100. The distance to each point is measured, and based on the measured distance information, the calculation device 202 distributes the distance from the predetermined reference point (nearest point 7) of the subject 3 to the body axis direction and the body width direction of the subject 3 Create Further, the body position of the subject 3 is determined by the arithmetic device 202 based on the distance distribution, and the determined body position information is set as an imaging condition of the X-ray CT apparatus 1.

  Accordingly, it is possible to easily determine the posture of the subject 3 using only the distance information from the predetermined measurement point to each point of the subject 3 lying on the bed 101. Therefore, it is possible to eliminate the burden of visual position determination by the operator in the normal CT examination workflow, and to shorten the imaging preparation time. In addition, since no special clothing is required for posture determination, a new cost burden is not imposed on the user side.

  In addition, since the control unit 200 adjusts the position of the bed 101 based on the determined body position information, there is no need for the manual position setting operation of the operator and the operator's visual / manual work of adjusting the position of the bed. Can be improved.

  In the first embodiment, after the intermediate posture is determined by the first posture determination process, the final posture determination is performed by performing the second posture determination process. By using this two-step procedure, it is possible to increase the processing speed of posture determination and obtain a determination result with high accuracy. This is because the posture determination process of the present invention is intended for determination of several postures taken in a normal CT examination, and the determination of specific postures is intentionally excluded. Therefore, the posture determination process of the present invention is particularly suitable for a test that does not perform imaging in a specific posture, such as a CT test in a general health checkup.

  Further, in the body position determination process, the body position of the subject 3 is determined based on the shape of the created distance distribution and the like, so that it is not necessary to perform complicated processing such as matching with a predetermined reference image as conventionally performed. Therefore, the processing load on the arithmetic device 202 can be reduced and the processing speed can be increased.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, a description will be given of a method for improving the determination accuracy of the body posture in the vertical direction of the subject 3 (“upwardly”, “depressed”) in the posture determination of the subject 3 lying on the bed 101.

  The hardware configuration and functional configuration of the arithmetic device 202 of the second embodiment are the same as those in FIGS. In the following description, the same parts are denoted by the same reference numerals, and redundant description is omitted.

  In 2nd Embodiment, the arithmetic unit 202 adds the process of step S701-step S704 shown in FIG. 22 after the process of step S601-step S604 of the posture determination 2nd process of FIG. The body posture information of the subject 3 obtained by the processing in steps S601 to S604 is set as a head-side supine candidate or a head-side prone candidate.

  In step S701, the computing device 202 acquires the distant body axis direction distance distribution (body axis direction distance distribution before ternarization) created in step S602 (step S701). Next, the computing device 202 determines the rate of change of the distance value at the boundary between the near part and the far part of the body axis direction distance distribution acquired in step S701 (step S702).

  In the case of the head-back position, as shown in FIG. 23A, the change in the distance value from the measurement point in the far direction from the nearest point 7 around the top of the head to the nose of the subject 3 is small. And since it will become a trunk | drum when it exceeds a nose tip, a distance value will change rapidly. On the other hand, in the subject 3 in the head-down position, the distance from the head, neck, and torso gradually increases as shown in FIG. 23B (the change in the distance value is small). That is, when the nose of the subject 3 is included in the vicinity, the boundary between the vicinity and the far part of the body axis direction distance distribution before the ternarization becomes steep. Therefore, by evaluating the rate of change of the boundary distance value, it can be determined whether the subject 3 is supine or prone.

  The threshold value of the change rate of the distance value at the boundary between the far part and the vicinity part of the body axis direction distance distribution before the ternarization may be a preset value, or the average change rate or the far part of the vicinity part. A value calculated based on the average rate of change may be used.

  In the determination of the change rate in step S702, if the above change rate is greater than the threshold value for the head-side supine candidate (step S702; supine candidate-> greater than the threshold value), the arithmetic unit 202 sets the body position to "head-side supine". The position information is determined and notified to the control device 200. When the above-mentioned rate of change is below a threshold (Step S702; supine candidate-> below threshold), it progresses to Step S703. In step S703, the control device 200 re-acquires the distance image and performs body posture determination from the beginning (step S301 in FIG. 7).

  In the determination of the rate of change in step S702, for the head-side prone candidate, if the above-described rate of change is less than or equal to the threshold value (step S702; face-down candidate → below the threshold value), the arithmetic unit 202 determines that the posture is “head-sided prone”. Then, this posture information is notified to the control device 200. When the above change rate is larger than the threshold (step S702; prone candidate → larger than threshold), the process proceeds to step S704. In step S704, the control device 200 re-acquires the distance image and performs body posture determination from the beginning (step S301 in FIG. 7).

  With the above processing, in the second embodiment, the difference in characteristics between the case of lying on the back and the case of lying down is determined based on the change rate of the distance value from the measurement point using the acquired distance distribution. Therefore, it is possible to improve the accuracy of the posture determination in the vertical direction of the subject 3 using only the distance distribution without performing complicated and time-consuming processing such as face recognition.

[Third Embodiment]
Next, the third embodiment of the present invention will be described in detail with reference to FIGS.

  In the third embodiment, during tomography in step S105 in FIG. 4, the body movement of the subject 3 lying on the bed 101 is monitored using a distance image, and tomography is performed according to the magnitude of the body movement. A method of controlling will be described.

  The control device 200 executes the photographing process according to the procedure shown in the flowchart of FIG. That is, as a pre-process, a distance image is taken by the distance measuring device 108 to create an image of only the subject 3 (step S101), and a body posture determination process is executed (step S102). The body posture determination process in step S102 may be any of the processes in the first and second embodiments. When the control apparatus 200 obtains the body position information of the subject 3 as a result of the body position determination process, it performs processing such as setting of imaging conditions (step S103) and bed position adjustment (step S104) based on the body position information. Tomography is started (step S105).

The subsequent processing will be described with reference to FIG.
When tomography is started by the processing up to step S105 (step S801), the control device 200 captures a distance image by the distance measuring device 108 during tomography (step S802). In the distance image capturing process of step S802, it is desirable to create, for example, the image 52 of the subject 3 by the arithmetic unit 202 as the distance image. Only the subject 3 image 52 is created by the processing procedure of steps S201 to S204 in FIG.

  Next, the arithmetic device 200 performs a body movement determination process (step S803). In the body motion determination process in step S803, the arithmetic device 200 first sets a body motion monitoring region for monitoring body motion in the distance image acquired by the distance measuring device 108. As shown in FIG. 25A, the body movement monitoring region may be a region 8a having a predetermined area separated from the nearest point 7 by a predetermined distance, or only the subject 3 as shown in FIG. 25B. An area where the body motion of the moving image 55 of the image is large may be used. Alternatively, the entire subject 3 may be used as a body movement monitoring region.

  For example, in the case of the body motion monitoring region in the vicinity of the torso near the chest, in the example of FIG. 25 (a), the closest point 7 is on the head of the subject 3, so ) Is set as a body movement monitoring region 8a within a predetermined distance. In the example of FIG. 25B, if the subject 3 does not hold his / her breath during tomography, the chest area is the body movement monitoring region 8a.

  The arithmetic device 200 monitors the movement of the body motion monitoring areas 8a and 8b of the distance image (moving image) during tomography and determines whether or not the amount of change in body motion is equal to or greater than a threshold value within a predetermined time. The threshold value may be a value set in advance, or may be a value calculated based on the amount of change in body movement during a predetermined period.

  If the change amount of the body movement is equal to or greater than the threshold value within the predetermined time (step S803; equal to or greater than the threshold value), the subject 3 may not be in a resting state, and thus the process proceeds to step S804. In step S804, the computing device 202 notifies the control device 200 to stop the X-rays irradiating the subject 3, and proceeds to step S807.

  When the amount of change in body movement in the body movement monitoring area is smaller than the threshold value within a predetermined time (step S803; smaller than the threshold value), it is regarded as a natural action in a resting state, and the process proceeds to step S805. The arithmetic unit 202 records the temporal change of body movement as body movement data in the storage device 213 (step S805). In order to be able to be used in the image reconstruction process performed by the image reconstruction device 221, the body so that it can be temporally consistent with the transmission X-ray data of the subject 3 obtained by the data collection device 106 during tomography. It is desirable to record dynamic data.

  When the change in body movement obtained in step S805 is periodic (for example, body movement accompanying breathing of the subject 3), X-ray irradiation control may be performed in accordance with the body movement period (step S806). The arithmetic device 202 notifies the control device 200 to perform X-ray irradiation at a suitable timing.

  Thereafter, tomographic imaging is performed for a predetermined imaging range, and when imaging is completed for the imaging range (step S807), a series of imaging processing ends.

  As described above, in the third embodiment, the distance measurement device 108 detects the body movement of the subject 3 being imaged and controls the imaging. For example, if imaging is interrupted when it is determined that the subject 3 is large and the subject 3 is not in a resting state, invalid exposure can be reduced. Further, by measuring the body movement of the subject 3, it is possible to perform an image reconstruction process considering the body movement. As a result, it is possible to provide an image in which artifacts due to body movement are reduced.

  As described above, as described in each embodiment, according to the X-ray CT apparatus 1 of the present invention, the distance from a predetermined measurement point to each point on the subject 3 is measured, and based on the measured distance information. Then, a distance distribution in the body axis direction and the body width direction is created from a predetermined reference point of the subject 3, the posture of the subject 3 is determined based on the distance distribution, and the determined posture is set as an imaging condition. Therefore, the posture of the subject 3 lying on the bed can be determined at high speed and with high accuracy, and the CT examination workflow can be improved.

  In each of the above-described embodiments, the example in which the distance measuring device 108 is arranged on the upper portion of the scan gantry unit 100 is shown, but the present invention is not limited to this. In addition, although the example in which the reference point of the distance distribution is the closest point between the measurement point and the subject 3 has been shown, the present invention is not limited to this. For example, when the arrangement (measurement point) of the distance measuring device 108 is set to the upper side in the horizontal direction of the subject 3, the reference point may be defined as the point closest to the scan gantry portion of the subject 3 region. Moreover, although the depth camera was shown as an example of the distance measuring device 108 and the example which acquires distance information from a distance image was shown, it is not limited to this. The distance measuring device 108 may be any device as long as it can measure distance information in the depth direction of the subject 3 from the measurement point.

  In the above-described embodiment, the calculation device 202 provided in the operation unit 20 performs processing such as creation of distance distribution and posture determination. The measuring device 108 may be provided. In this case, the calculation unit of the distance measurement device 108 may perform posture determination based on the distance information measured by the distance measurement device 108 and notify the control device 200 of the posture information that is the determination result.

  The preferred embodiments of the X-ray CT apparatus and the posture determination method according to the present invention have been described above, but the present invention is not limited to the above-described embodiments. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

DESCRIPTION OF SYMBOLS 1 ... X-ray CT apparatus 3 ... Test object 10 ... Scanner 20 ..... Operation unit 100 ..... Scan gantry 101 ..... Bed 102 ..... ... X-ray source 103 ... X-ray detector 104 ... Collimator 105 ...・ ・ ・ ・ ・ High voltage generator 106 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Data collector 107 ・ ・ ・ ・ ・ ・ Driver 200 ・ ・ ・ ・ ・ ・... Control device 201 ... I / O device 202 ... Operation device 211 ... Display Device 212 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Input Device 213... Storage device 221... Reconstruction processing device 222. ························································ ……・ Distance image of subject only 7, 7a, 7b ... Recent point 75 ... Position determination area 86 ... ..Couch position adjustment points 8a, 8b

Claims (6)

X-rays are irradiated from a plurality of angular directions around the subject with an X-ray source for irradiating the subject with X-rays and an X-ray detector for detecting X-rays transmitted through the subject facing each other. A scan gantry unit that acquires transmission X-ray data transmitted through the subject by the X-ray detector;
A bed for carrying the object into and out of the X-ray irradiation space in the scan gantry unit;
A reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector;
A control unit for controlling operations of the scan gantry unit and the bed;
A distance measuring device that measures the distance from a predetermined measurement point to each point on the subject;
A distance distribution creating unit that creates a distance distribution in the body axis direction and body width direction of the subject from a predetermined reference point of the subject based on the distance measured by the distance measuring device;
A body position determination unit that determines the body position of the subject based on the distance distribution;
A posture setting unit that sets the posture determined by the posture determination unit as a photographing condition;
A body movement monitoring region setting unit that sets a monitoring region for monitoring the body movement of the subject based on the body position determined by the body position determination unit;
A controller that measures body movement in the monitoring area and controls imaging based on the measured body movement;
An X-ray CT apparatus comprising: X-rays are irradiated from a plurality of angular directions around the subject with an X-ray source for irradiating the subject with X-rays and an X-ray detector for detecting X-rays transmitted through the subject facing each other. A scan gantry unit that acquires transmission X-ray data transmitted through the subject by the X-ray detector;
A bed for carrying the object into and out of the X-ray irradiation space in the scan gantry unit;
A reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector;
A control unit for controlling operations of the scan gantry unit and the bed;
A distance measuring device that measures the distance from a predetermined measurement point to each point on the subject;
A distance distribution creating unit that creates a distance distribution in the body axis direction and body width direction of the subject from a predetermined reference point of the subject based on the distance measured by the distance measuring device;
A body position determination unit that determines the body position of the subject based on the distance distribution;
A posture setting unit that sets the posture determined by the posture determination unit as a photographing condition;
Equipped with a,
The posture determination unit
A first body position determination unit that determines an intermediate body position indicating a head direction of the subject based on a shape of a distance distribution in the body width direction;
A second body position determination unit that determines which of a plurality of body positions subdivided from the intermediate body position based on the distance distribution in the body axis direction,
The first body position determination unit
Based on the magnitude of the distance value from the reference point, the distance distribution in the body width direction is multivalued into a background part, a far part, and a neighboring part, and the intermediate body position based on the number of the neighboring part and the far part X-ray CT apparatus characterized by determining X-rays are irradiated from a plurality of angular directions around the subject with an X-ray source for irradiating the subject with X-rays and an X-ray detector for detecting X-rays transmitted through the subject facing each other. A scan gantry unit that acquires transmission X-ray data transmitted through the subject by the X-ray detector;
A bed for carrying the object into and out of the X-ray irradiation space in the scan gantry unit;
A reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector;
A control unit for controlling operations of the scan gantry unit and the bed;
A distance measuring device that measures the distance from a predetermined measurement point to each point on the subject;
A distance distribution creating unit that creates a distance distribution in the body axis direction and body width direction of the subject from a predetermined reference point of the subject based on the distance measured by the distance measuring device;
A body position determination unit that determines the body position of the subject based on the distance distribution;
A posture setting unit that sets the posture determined by the posture determination unit as a photographing condition;
Equipped with a,
The posture determination unit
A first body position determination unit that determines an intermediate body position indicating a head direction of the subject based on a shape of a distance distribution in the body width direction;
A second body position determination unit that determines which of a plurality of body positions subdivided from the intermediate body position based on the distance distribution in the body axis direction,
The second body position determination unit
The distance distribution in the body axis direction is multi-valued based on the distance value from the reference point, and the posture is determined based on the size of the spread in the vicinity of the multi-valued distance distribution. X-ray CT apparatus. The second body position determination unit
Furthermore, it is characterized in that it is determined whether the subject is supine or prone on the basis of a change rate of a distance value at a boundary portion between a near portion and a far portion in the distance distribution in the body axis direction. X-ray CT apparatus according to 3. X-rays are irradiated from a plurality of angular directions around the subject with an X-ray source for irradiating the subject with X-rays and an X-ray detector for detecting X-rays transmitted through the subject facing each other. A scan gantry unit that acquires transmission X-ray data transmitted through the subject by the X-ray detector;
A bed for carrying the object into and out of the X-ray irradiation space in the scan gantry unit;
A reconstruction processing unit for reconstructing a subject image using transmission X-ray data detected by the X-ray detector;
A control unit for controlling operations of the scan gantry unit and the bed;
A distance measuring device that measures the distance from a predetermined measurement point to each point on the subject;
A distance distribution creating unit that creates a distance distribution in the body axis direction and body width direction of the subject from a predetermined reference point of the subject based on the distance measured by the distance measuring device;
A body position determination unit that determines the body position of the subject based on the distance distribution;
A posture setting unit that sets the posture determined by the posture determination unit as a photographing condition;
Equipped with a,
The posture determination unit
A first body position determination unit that determines an intermediate body position indicating a head direction of the subject based on a shape of a distance distribution in the body width direction;
A second body position determination unit that determines which of a plurality of body positions subdivided from the intermediate body position based on the distance distribution in the body axis direction,
In the first posture determination process, when it is determined that the intermediate posture is any one of leftward, rightward, left-handed, and right-handed, the second posture determining unit obtains the multi-valued distance distribution in the body width direction, and the vicinity An X-ray CT apparatus characterized by determining whether the foot side or the head side based on the size of the spread of the part . Measuring a distance to each point on the subject lying on the bed by a distance measuring device arranged at a predetermined measurement point;
A calculation device that creates a distance distribution in the body axis direction and body width direction of the subject from a predetermined reference point of the subject based on the measured distance;
A step in which the arithmetic device determines the posture of the subject based on the distance distribution;
Setting the determined body position as a shooting condition;
Setting a monitoring region for monitoring body movement of the subject based on the posture determined by the step of determining the posture;
Measuring body movement in the monitoring area, and controlling imaging based on the measured body movement;
A body posture determination method comprising:

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