JP2020000450A - X-ray ct apparatus and photographing planning device - Google Patents

Abstract

To provide an X-ray CT apparatus and a photographing planning device capable of reducing the degree of exposure when photographing a positioning image.SOLUTION: An X-ray CT apparatus of the embodiment includes an X-ray tube, detector, acquisition part, calculation part, and setting part. The X-ray tube irradiates an X-ray. The detector detects an X-ray which is irradiated from the X-ray tube to transmit the photographing subject. The acquisition part acquires: a first past image, which is the latest image among the past images taken by another medical image diagnostic apparatus, and the photography condition; a second past image, which is taken prior to the first past image by another medical image diagnostic apparatus, and the photography condition; and a photography condition of a third past image which is a CT image taken in the past. The calculation part calculates the variation from the second past image to the first past image on the basis of the first past image and/or the photography condition of the first past image, and the second past image and/or the photography condition of the second past image. The setting part sets a new photography condition for photographing a CT image on a subject on the basis of the photography condition and variation of the third past image.SELECTED DRAWING: Figure 1

Description

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

  When capturing a positioning image (also referred to as a scano image or a scout image), an operator such as a technician determines a capturing start position and a capturing end position. An operator performs imaging by setting a fixed range to a fixed dose. The operator arbitrarily operates the X-ray irradiation from the imaging start position to the imaging end position, and presses the stop button to end the imaging.

The positioning image is an image that is taken for determining the imaging range or for calculating the dose of a scan for main inspection (also referred to as main scan). Therefore, the positioning image is rarely used for diagnosis, and photographing the positioning image leads to unnecessary exposure.
In addition, despite the fact that there is an image of a similar range captured by an X-ray apparatus or a CT (Computed Tomography) apparatus in the past, since a positioning image is normally captured again before the main scan, a previously captured image is used. Has not been used effectively.

JP 2015-130909 A JP 2005-143948 A

  An object to be solved by the present invention is to reduce exposure during positioning imaging.

  The X-ray CT apparatus according to the present embodiment includes an X-ray tube, a detector, an acquisition unit, a calculation unit, and a setting unit. The X-ray tube emits X-rays. The detector detects X-rays emitted from the X-ray tube and transmitted through the subject. The acquisition unit is configured to determine the most recent first past image of the past images taken by the other medical image diagnostic apparatus, the imaging conditions of the first past image, and the other medical image before the first past image. A second past image photographed by the diagnostic device, photographing conditions of the second past image, and photographing conditions of a third past image which is a CT image photographed in the past are acquired. The calculation unit is configured to calculate the second past image and / or the second past image based on the shooting conditions of the first past image and / or the first past image and the shooting conditions of the second past image and / or the second past image. The amount of change to one past image is calculated. The setting unit sets a new imaging condition for imaging the CT image of the subject based on the imaging condition of the third past image and the change amount.

FIG. 1 is a block diagram illustrating a configuration of the X-ray CT apparatus according to the first embodiment. FIG. 2 is a flowchart illustrating the operation of the X-ray CT apparatus according to the first embodiment. FIG. 3 is a conceptual diagram relating to setting of imaging conditions according to the first embodiment. FIG. 4 is a flowchart illustrating details of the photographing range setting process according to the first embodiment. FIG. 5 is a flowchart illustrating details of the setting process of the photographing condition according to the first embodiment. FIG. 6 is a flowchart illustrating another example of the photographing condition setting process according to the first embodiment. FIG. 7 is a diagram illustrating an example of the conversion table according to the first embodiment. FIG. 8 is a conceptual diagram of an X-ray CT apparatus including a projector. FIG. 9 is a diagram illustrating an example of the projection of the imaging range on the subject according to the first embodiment. FIG. 10 is a diagram illustrating an imaging planning device according to the second embodiment. FIG. 11 is a sequence diagram illustrating a shooting condition determination process performed by the shooting management system including the shooting planning device according to the second embodiment.

Hereinafter, an X-ray CT (Computed Tomography) apparatus and an imaging planning apparatus according to the present embodiment will be described with reference to the drawings. In the following embodiments, portions denoted by the same reference numerals perform the same operation, and redundant description will be omitted as appropriate.
Hereinafter, an embodiment will be described with reference to the drawings.

(1st Embodiment)
FIG. 1 is a block diagram illustrating a configuration of an X-ray CT apparatus according to one embodiment. The X-ray CT apparatus 1 illustrated in FIG. 1 includes a gantry device 10, a bed device 30, and a console device 40. FIG. 1 shows that a plurality of gantry devices 10 are drawn for convenience of explanation. In this embodiment, the longitudinal direction of the rotation axis of the rotating frame 13 or the top plate 33 of the bed device 30 in the non-tilted state is perpendicular to the Z-axis direction and the Z-axis direction, and is an axial direction that is horizontal to the floor surface. Are defined orthogonal to the X-axis direction and the Z-axis direction, and the axis direction perpendicular to the floor surface is defined as the Y-axis direction.

  For example, the gantry device 10 and the bed device 30 are installed in a CT examination room, and the console device 40 is installed in a control room adjacent to the CT examination room. Note that 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 with the gantry device 10 and the bed device 30. In any case, the gantry device 10, the bed device 30, and the console device 40 are communicably connected by wire or wirelessly.

  The gantry device 10 is a scanning device having a configuration for performing X-ray CT imaging of the subject P. 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 data collection device 18 (DAS (Data Acquisition System) 18).

  The X-ray tube 11 is a vacuum tube that generates X-rays by irradiating thermoelectrons from a cathode (filament) to an anode (target) by applying a high voltage from an X-ray high voltage device 14 and supplying a filament current. It is. Specifically, X-rays are generated by the collision of the thermal electrons with the target. The X-rays generated by the X-ray tube 11 are formed into a cone beam shape via, for example, a collimator 17 and are irradiated on the subject P.

  The X-ray detector 12 detects X-rays emitted 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 rows in which a plurality of X-ray detection elements are arranged in a channel direction along one arc around the focal point of the X-ray tube 11. The X-ray detector 12 has, for example, a row structure in which a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in a channel direction are arranged in a slice direction (row direction, row direction).

  Specifically, the X-ray detector 12 is, for example, an indirect conversion type detector including a grid, a scintillator array, and an optical sensor array.

  The scintillator array has a plurality of scintillators. The scintillator has a scintillator crystal that outputs light having a photon amount corresponding to the incident X-ray dose.

  The grid has an X-ray shielding plate which is arranged on the surface of the scintillator array on the X-ray incident side and has a function of absorbing scattered X-rays. The grid may be called a collimator (one-dimensional collimator or two-dimensional collimator).

The optical sensor array has a function of amplifying light received from the scintillator and converting the light into an electric signal, and includes, for example, an optical sensor such as a photomultiplier tube (photomultiplier: PMT).
Note that the X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into an electric signal.

  The rotating frame 13 supports the X-ray generation unit and the X-ray detector 12 so as to be rotatable around a rotation axis. Specifically, the rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 so as to face each other, and rotates the X-ray tube 11 and the X-ray detector 12 by a control device 15 described later. It is. The rotating frame 13 is rotatably supported by a fixed frame (not shown) made of metal such as aluminum. Specifically, the rotating frame 13 is connected to an edge of the fixed frame via a bearing. The rotary frame 13 receives power from the drive mechanism of the control device 15 and rotates around the rotation axis Z at a constant angular velocity.

  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 in which an opening (bore) 19 forming an imaging space is formed. The opening substantially matches the FOV. The center axis of the opening coincides with the rotation axis Z of the rotation frame 13. The detection data generated by the DAS 18 is provided on a non-rotating portion (for example, a fixed frame, not shown in FIG. 1) of the gantry device by optical communication from a transmitter having a light emitting diode (LED). The data is transmitted to a receiver (not shown) having a photodiode, and is transmitted to the console device 40. The transmission method of the detection data from the rotating frame to the non-rotating portion of the gantry is not limited to the above-described optical communication, and any method may be adopted as long as it is a non-contact type data transmission.

  The X-ray high voltage device 14 has an electric circuit such as a transformer (transformer) and a rectifier, and has a high voltage having 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 controller that controls the output voltage according to the X-rays emitted by the X-ray tube 11. The high voltage generator may be of a transformer type or an inverter type. The X-ray high-voltage device 14 may be provided on a rotating frame 13 described later, or may be provided on a fixed frame (not shown) of the gantry device 10.

  The control device 15 has a processing circuit having a CPU (Central Processing Unit) and the like, and a driving mechanism such as a motor and an actuator. The processing circuit has, as hardware resources, 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). Further, the control device 15 includes an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and other complex programmable logic devices (CPLDs). ), 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 implements the above control by reading and implementing the program stored in the memory.

  Further, the control device 15 has a function of receiving an input signal from an input interface 43, which will be described later, attached to the console device 40 or the gantry device 10, and controlling the operation of the gantry device 10 and the couch device 30. For example, the control device 15 performs control to rotate the rotating frame 13 in response to the input signal, control to tilt the gantry device 10, and control to operate the bed device 30 and the top board 33. The control for tilting the gantry device 10 is performed by the control device 15 based on the tilt angle (tilt angle) information input by the input interface 43 attached to the gantry device 10 so that the control device 15 rotates the rotation frame about an axis parallel to the X-axis direction. 13 is rotated. Further, the control device 15 may be provided on the gantry device 10 or on the console device 40. Note that, instead of storing the program in the memory, the control device 15 may be configured to directly incorporate the program into the circuit of the processor. 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 amount of X-ray emitted from the X-ray tube 11. Specifically, the wedge 16 transmits and attenuates the X-rays radiated from the X-ray tube 11 so that the X-rays radiated to the subject P from the X-ray tube 11 have a predetermined distribution. Filter. For example, the wedge 16 (wedge filter, bow-tie filter) is a filter formed 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 the X-ray transmitted through the wedge 16, and forms a slit by combining a plurality of lead plates and the like. The collimator 17 may be called an X-ray diaphragm.

  The DAS 18 reads an electric signal from the X-ray detector 12 and generates digital data (hereinafter, also referred to as raw data) related to the dose of the X-ray detected by the X-ray detector 12 based on the read electric signal. The raw data is a set of data indicating a channel number, a column number, a view number indicating a collected view (also referred to as a projection angle) of the source X-ray detecting element, and an integrated value of a detected X-ray dose. is there. The DAS 18 is realized by, for example, an ASIC (Application Specific Integrated Circuit) equipped with a circuit element capable of generating raw data. The raw data is transferred to the console device 40.

  For example, DAS 18 includes a preamplifier, a variable amplifier, an integrator, and an A / D converter for each detector pixel. The preamplifier amplifies an electric signal from the connection source X-ray detection element with a predetermined gain. The variable amplifier amplifies the electric signal from the preamplifier with a variable gain. The integrating circuit integrates the electric signal from the preamplifier over one view period to generate an integrated signal. The peak value of the integration signal corresponds to the X-ray dose value detected by the connection source X-ray detection element over one view period. The A / D converter converts the integration signal from the integration circuit from analog to digital to generate raw data.

The couch device 30 is a device on which the subject P to be scanned is placed and moved, and includes a base 31, a couch driving device 32, a top plate 33, and a support frame.
The base 31 is a housing that supports the support frame 34 movably in the vertical direction.

  The couch driving device 32 is a motor or an actuator that moves the table 33 on which the subject P is placed in the longitudinal direction of the table 33. The couch driving device 32 moves the couchtop 33 according to control by the console device 40 or control by the control device 15. For example, the couch driving device 32 moves the table 33 in a direction perpendicular to the object P so that the body axis of the object P placed on the table 33 coincides with the center axis of the opening of the rotating frame 13. I do. Further, the couch driving device 32 may move the couchtop 33 along the body axis direction of the subject P in accordance with X-ray CT imaging performed using the gantry device 10. The couch driving device 32 generates power by being driven at a rotation speed according to a duty ratio of a driving signal from the control device 15 or the like. The couch driving 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. The couch driving device 32 may move the support frame 34 in the longitudinal direction of the top plate 33 in addition to the top plate 33.

  The console device 40 has a memory 41, a display 42, an input interface 43, and a processing circuit 44. Data communication among the memory 41, the display 42, the input interface 43, and the processing circuit 44 is performed via a bus (BUS). Although the console device 40 is described as being separate from the gantry device 10, the gantry device 10 may include the console device 40 or some of the components of the console device 40.

  The memory 41 is a storage device such as a hard disk drive (HDD), a solid state drive (SSD), or an integrated circuit storage device for storing various information. The memory 41 stores, for example, projection data and reconstructed image data. The memory 41 is connected to a portable storage medium such as a CD (Compact Disc), a DVD (Digital Versatile Disc), a flash memory, and a semiconductor memory element such as a RAM (Random Access Memory) in addition to the HDD and the SSD. It may be a driving device for reading and writing various information. The storage area of the memory 41 may be in the X-ray CT apparatus 1 or in an external storage device connected via a network. For example, the memory 41 stores data of a CT image and a display image. The memory 41 stores a control program according to the present embodiment.

  The display 42 displays various information. For example, the display 42 outputs a medical image (CT image) generated by the processing circuit 44, a GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, as the display 42, for example, a liquid crystal display (LCD: Liquid Crystal Display), a CRT (Cathode Ray Tube) display, an organic EL display (OELD: Organic Electro Luminescence Display), a plasma display, or any other display is appropriately used. , Has become available. The display 42 may be provided on the gantry device 10. Further, the display 42 may be a desktop type, or may be configured by a tablet terminal or the like that can wirelessly communicate 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 electric signals to the processing circuit 44. For example, the input interface 43 receives, from the operator, acquisition conditions for acquiring 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. In the present embodiment, the input interface 43 is not limited to an interface including physical operation components such as a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad, and a touch panel display. 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. . The input interface 43 may be provided in the gantry device 10. Further, the input interface 43 may be configured by a tablet terminal or the like capable of wirelessly communicating with the console device 40 main body.

  The processing circuit 44 controls the entire operation of the X-ray CT apparatus 1 in accordance with the input operation electric signal output from the input interface 43. For example, the processing circuit 44 has, as hardware resources, a processor such as a CPU, an MPU, and a GPU (Graphics Processing Unit) and a memory such as a ROM and a RAM. The processing circuit 44 includes a system control function 441, a preprocessing function 442, a reconfiguration processing function 443, a search function 444, an acquisition function 445 (an acquisition unit), and a calculation function 446 (a calculation) by a processor that executes a program developed in the memory. Unit) and a setting function 447 (setting unit). Each function (the system control function 441, the preprocessing function 442, the reconfiguration processing function 443, the search function 444, the acquisition function 445, the calculation function 446, and the setting function 447) is limited to the case where it is realized by a single processing circuit. Absent. A processing circuit may be configured by combining a plurality of independent processors, and each processor may execute a program to realize each function.

  The system control function 441 controls each function of the processing circuit 44 based on an input operation received from the operator via the input interface 43. Specifically, the system control function 441 reads the control program stored in the memory 41, expands it on the memory in the processing circuit 44, and controls each unit of the X-ray CT apparatus 1 according to the expanded control program. . For example, the processing circuit 44 controls each function of the processing circuit 44 based on an input operation received from the operator via the input interface 43. For example, the system control function 441 acquires a two-dimensional positioning image of the subject P for determining a scan range, imaging conditions, and the like. Note that the positioning image is also called a scano image or a scout image.

  The preprocessing function 442 generates data obtained by performing preprocessing such as logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, and beam hardening correction on the detection data output from the DAS 18. Note that raw data (detection data) before preprocessing and data after preprocessing are sometimes collectively referred to as projection data.

  The reconstruction processing function 443 performs a reconstruction process on the projection data generated by the preprocessing function 442 using a filtered back projection method (FBP method: Filtered Back Projection), an iterative approximation reconstruction method, or the like. To generate CT image data.

The search function 444 searches for and acquires the latest past image (also referred to as a first past image) and the shooting conditions of the first past image among the past images taken by another medical image diagnostic apparatus. The search function 444 stores a past image (also referred to as a second past image) photographed by another medical image diagnostic apparatus before the first past image and a photographing condition of the second past image, for example, PACS (Picture Archiving and Communication). System) Search from the server. Here, the imaging conditions include an imaging range for the subject P and X-ray conditions.
The search function 444 searches for a CT image captured in the past (also referred to as a third past image or a CT past image) and an imaging condition of the CT past image.
The acquisition function 445 acquires a first past image, a second past image, and a CT past image.

The calculation function 446 calculates the amount of change between the second past image and the first past image with reference to the three types of past images and the imaging conditions respectively associated with the three types of past images.
The setting function 447 sets new imaging conditions when imaging a CT image of the subject P based on the CT past image, the imaging conditions of the CT past image, and the amount of change.

The processing circuit 44 also performs scan control processing, image processing, and display control processing.
The scan control process is a process for controlling various operations related to X-ray scanning, such as supplying a high voltage to the X-ray high-voltage device 14 and irradiating the X-ray tube 11 with X-rays.
The image processing is based on an input operation received from the operator via the input interface 43, and converts CT image data generated by the reconstruction processing function 443 into tomographic image data or three-dimensional image data of an arbitrary cross section by a known method. This is the process of converting to.
The display control process is a process of controlling the display 42 so as to display information on a process or processing result in each function or process of the processing circuit 44.

  The processing circuit 44 is not limited to being included in the console device 40 but may be included in an integrated server that collectively performs processing on detection data acquired by a plurality of medical image diagnostic apparatuses.

  Although the console device 40 has been described as executing a plurality of functions with a single console, the plurality of functions may be executed by separate consoles. For example, the functions of the processing circuit 44 such as the preprocessing function 442 and the reconstruction processing function 443 may be distributed.

Next, the operation of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to the flowchart in FIG.
In step S201, the imaging region of the subject P is determined. Specifically, for example, the processing circuit 44 may acquire the ID of the subject P and information on the inspection target site of the subject P from the inspection order, and determine the imaging site from the information.

In step S202, the processing circuit 44 determines whether there are three types of past images and shooting conditions. The three types of past images and imaging conditions are the same as the first past image and imaging conditions of the other medical image diagnostic apparatus, the second past image and imaging conditions of the other medical image diagnostic apparatus, and the same X-ray CT apparatus 1. Is a CT past image and a photographing condition.
Hereinafter, an X-ray imaging apparatus is assumed as another medical image diagnostic apparatus. An X-ray image is assumed as the first past image and the second past image. Note that the other medical image diagnostic apparatus may be a magnetic resonance imaging (MRI) apparatus, or an MR image captured by an MRI apparatus may be used as a past image. Further, the CT past image may be a positioning image or a CT image photographed by a main scan. The CT image is not limited to an image captured by the same device, and may be any image. For example, CT images taken using the same series of X-ray CT apparatuses, such as having the same model number, or images taken using different series of X-ray CT apparatuses manufactured by the same manufacturer may be used. Alternatively, a CT image obtained by using an X-ray CT apparatus manufactured by a different manufacturer may be used.

  As a specific process of step S202, by executing the search function 444, the processing circuit 44 determines that the ID of the subject P and the imaging region are the same, the first past image and the imaging condition, and the second past image. For example, a PACS server is searched for the imaging conditions and the CT past image and the imaging conditions. If the above three types of past images and imaging conditions are not found, the process proceeds to step S203. If the three types of past images and imaging conditions are found, the process proceeds to step S204.

In step S203, the X-ray CT apparatus 1 performs normal positioning imaging (scano imaging), and sets imaging conditions from the captured normal positioning image. Further, the process proceeds to step S210 to execute the main scan.
In step S204, by executing the acquisition function 445, the processing circuit 44 acquires (reads) the three types of past images and imaging conditions found in step S202.
In step S205, the current position of the subject P is recognized. The current position may be recognized from an image captured by, for example, a camera (not shown) disposed above the inner wall of the bore 19.

In step S206, by executing the calculation function 446, the processing circuit 44 causes the three types of past images and shooting conditions, specifically, the shooting conditions of the first past image and / or the first past image and the second past image. And / or by referring to the imaging conditions of the second past image, the amount of change relating to the degree of change between images and / or between imaging conditions is calculated. The change amount indicates, for example, a numerical value, position information (such as coordinate information), a range, and the like.
In step S207, by executing the setting function 447, the processing circuit 44 sets new imaging conditions for CT imaging of the subject P by the X-ray CT apparatus 1 based on the amount of change.
In step S208, the processing circuit 44 controls the control device 15 to perform a main scan on the subject P according to the set new imaging condition. Thus, the operation of the X-ray CT apparatus 1 according to the first embodiment ends.

  If the period between the imaging date of the second past image and the imaging date of the CT past image is too long, the amount of change obtained based on the X-ray image may change the current state of the body of the subject P. It may not be reflected. Thus, for example, by executing the search function 444, the processing circuit 44 causes the system control function 441 to be activated when the period between the acquired date of the second past image and the date of the CT past image is equal to or greater than the threshold. When executed, the processing circuit 44 generates an alert.

  Further, an alert may be generated even when a change in the body of the subject P is large. Specifically, for example, by executing the calculation function 446, the processing circuit 44 obtains an estimated subject thickness (referred to as a current estimated subject thickness) obtained based on the amount of change based on the X-ray image and the CT past image. It is determined whether or not the estimated subject thickness at the time of capturing the CT past image has changed by a threshold value or more (for example, whether or not it has changed by ± 3 cm or more). If it has changed by the threshold or more, the processing circuit 44 generates an alert by executing the system control function 441.

  For example, by executing the system control function 441 and the display control function, the processing circuit 44 may notify the operator of an alert. The alert may be displayed on the display 42 as a message indicating that the period is equal to or longer than the threshold, or may be output from a speaker (not shown) as a sound effect or by reading out the message by voice. That is, any method of alerting may be used as long as it alerts the operator.

Next, setting of shooting conditions according to the first embodiment will be described with reference to the conceptual diagram of FIG.
As shown in FIG. 3, a first past image 51 photographed by an X-ray photographing apparatus, which is another medical image diagnostic apparatus, and photographing conditions 52 (imaging range and X-ray conditions) associated with the first past image 51, The imaging conditions 54 (imaging range and X-ray conditions) associated with the second past image 53 and the second past image 53 are acquired.
By executing the calculation function 446, the processing circuit 44 calculates the amount of change between the first past image 51 and the second past image 53 and the amount of change between the shooting conditions 52 and 54.
Thereafter, the amount of change is added to the imaging condition 51 by a calculation such as multiplying the calculated amount of change to the imaging condition 51 of the CT past image using the X-ray CT apparatus 1 which is the modality that is currently performing imaging. To reflect. Thereby, a new photographing condition 57 is generated.

Next, details of the setting process of the shooting range, which is one of the shooting conditions, will be described with reference to the flowchart of FIG.
In step S2061, by executing the calculation function 446, the processing circuit 44 compares the first past image with the second past image, and determines the amount of change from the second past image to the first past image, here, the subject P Calculate the amount of change in body position. The amount of change in the position of the body is, specifically, the difference between the organ position in the body axis direction between the first past image and the second past image, or the size of the body such as the organ position in the body width direction or the waist circumference. Or a ratio based on these differences. When the subject P is in the growth period, the height may have increased between the shooting time of the second past image and the shooting time of the first past image. , The difference in body size in the body axis direction.

  In step S2071, by executing the setting function 447, the processing circuit 44 determines a new imaging range of a CT image to be newly captured based on the CT past image and the amount of change in the position of the body of the subject P. . Specifically, the processing circuit 44 may calculate a change amount of the position of the subject P as a ratio and determine a new imaging range by multiplying the ratio by the CT image.

  In step S2072, by executing the setting function 447, the processing circuit 44 sets the new imaging range determined in step S2071 as the imaging field of view (FOV: Field of View) according to the current position of the subject P. I do. In setting a new imaging range, the processing circuit 44 performs registration (registration) of the CT past image with respect to the current position of the subject P. As a registration method, at least one of an enlargement process, a reduction process, a rotation process, and a morphing process may be used. Instead of using a past CT image and a projector, a light projector may be used, and the imaging range may be displayed on the subject P by the light projector.

Next, details of the setting process of the X-ray condition, which is one of the imaging conditions, will be described with reference to the flowchart of FIG.
In step S2062, by executing the calculation function 446, the processing circuit 44 compares the X-ray condition of the first past image with the X-ray condition of the second past image, and converts the second past image to the first past image. The amount of change, here the amount of change in X-ray conditions, is calculated.
As the amount of change in the X-ray conditions, for example, the body thickness of the subject P, the voltage value of the tube voltage, the current value of the tube current, and the irradiation time, between the time of capturing the second past image and the time of capturing the first past image A difference or a ratio may be used.

  The body thickness may be calculated based on aluminum equivalent (Al equivalent), water equivalent, water equivalent thickness, and estimated subject thickness. As an example, an aluminum equivalent is used in estimating a body thickness in an X-ray image, and a water equivalent is used in estimating a body thickness in a CT image. Therefore, for example, for the first past image and the second past image, the X-ray absorption amount is calculated based on the respective pixel values, and the X-ray absorption amount is converted into an aluminum equivalent thickness according to a predetermined conversion formula. The body thickness of the subject P is estimated from the converted aluminum equivalent thickness.

In step S2073, by executing the setting function 447, the processing circuit 44 causes the processing unit 44 to newly acquire a CT image based on the X-ray conditions at the time of CT past image capturing and the amount of change in the X-ray conditions calculated in step S2062. Is set. More specifically, the processing circuit 44 calculates a ratio based on the difference between the tube currents, for example, as the amount of change in the X-ray condition, and multiplies the ratio by the X-ray condition of the CT past image to obtain a new X-ray condition. Just set it.
When the body thickness is calculated as the change amount of the X-ray condition, the ratio in the aluminum equivalent is converted into the ratio in the water equivalent, and the converted ratio may be applied to the X-ray condition of the CT past image.

Next, another example of the X-ray condition setting process will be described with reference to the flowchart in FIG.
In step S2074, by executing the setting function 447, the processing circuit 44 performs the conversion in which the change amount of the X-ray condition of the other medical image diagnostic apparatus is associated with the change amount of the X-ray condition of the X-ray CT apparatus 1. Using the table, the change amount of the X-ray condition in the X-ray CT apparatus 1 corresponding to the change amount calculated in step S2062 is acquired. The processing circuit 44 can set a new X-ray condition by applying the acquired change amount to the X-ray condition of the CT past image.

Here, an example of the conversion table will be described with reference to FIG.
The conversion table 601 is a table in which a change amount (mAs) of a time product of a tube current of an X-ray imaging apparatus, which is another medical image diagnostic apparatus, and a tube current (mA) of the X-ray CT apparatus 1 are associated with each other. .
The conversion table 602 is a table in which a change amount (kV) of a tube voltage of an X-ray imaging apparatus, which is another medical image diagnostic apparatus, and a tube current (mA) of an X-ray CT apparatus are associated with each other. The conversion table 602 may include information on the tube voltage and the type of filter in addition to the tube current.

For example, when the change amount of the time product of the tube current in the X-ray imaging apparatus is “−100 mA”, the change amount of the tube current in the X-ray CT apparatus 1 is “−200 mA”. Similarly, when the change amount of the tube voltage in the X-ray imaging apparatus is “+2 kV”, the change amount of the tube current in the X-ray CT apparatus 1 is “+100 mA”.
As described above, by preparing the conversion table in advance, it is possible to easily obtain the setting value of the imaging condition of the X-ray CT apparatus 1 based on the amount of change of another medical image diagnostic apparatus.

Before the main scan, the imaging range of the new CT imaging set as described above may be projected onto the subject P using a projector.
FIG. 8 shows a conceptual diagram of the X-ray CT apparatus 1 included in the projector.
The X-ray CT apparatus 1 illustrated in FIG. 8 includes a gantry device 10, a bed device 30, and a projector 70.
The projector 70 is disposed above the inner wall of the bore 19 provided in the gantry device 10 and can project a new imaging range on the subject P on the top board 33.

Next, an example of projection of the imaging range onto the subject P is shown in FIG.
FIG. 9 is an example in which the set imaging range is projected on the subject P. Here, an example is shown in which an imaging range based on a past CT image is projected as a CT image on the body surface of the subject P, but the present invention is not limited to this, and only an outline, a marker, or the like may be displayed.

  According to the first embodiment described above, based on the first past image and the second past image of another medical image diagnostic apparatus relating to the subject, a new imaging range and a new imaging range of a CT image to be newly imaged are obtained. Set the appropriate shooting conditions. This eliminates the need for capturing a positioning image when performing a new CT scan, and reduces exposure during positioning scan.

(Second embodiment)
The process of determining the new CT imaging conditions (imaging range and X-ray conditions) may be performed by an external imaging planning device.

An imaging planning device according to the second embodiment will be described with reference to the block diagram of FIG.
The imaging planning device 90 includes a search function 444, an acquisition function 445, a calculation function 446, and a setting function 447. The imaging planning device 90 is communicably connected to the X-ray CT device 1. Note that the operations of the search function 444, the acquisition function 445, the calculation function 446, and the setting function 447 are the same as the above-described operations, and thus description thereof will be omitted.

Next, an example of a setting process of an imaging range and an X-ray condition by the imaging management system including the imaging planning device 90 will be described with reference to a sequence diagram of FIG. Hereinafter, a case will be described in which, for example, an imaging planning device 90 is included in an RIS (Radiology Information System).
The imaging management system including the imaging planning device 90 illustrated in FIG. 11 includes the X-ray CT device 1, the RIS, and the external storage 95. The external storage 95 is an image server such as a PACS.

In step S901, the RIS determines the imaging region of the subject P, as in step S201. The imaging part may be extracted from information included in the inspection order.
In step S902, by executing the search function 444, the RIS searches for three types of past images and imaging conditions associated with the past images, as in step S202. In the search for the photographing condition, the RIS may execute the search from the image data and the supplementary information stored in the external storage 95. If there are three types of past images, the process proceeds to step S904. If there are no three types of past images, the process proceeds to step S903.

In step S903, as in step S203, normal positioning photographing is performed.
In step S904, the RIS executes the acquisition function 445 to acquire (read) three types of images. When a past CT image is stored in the X-ray CT apparatus 1, the RIS only needs to acquire the past CT image from the X-ray CT apparatus 1.
In step S905, as in step S206, the processing circuit 44 executes the calculation function 446 to calculate the amount of change by referring to three types of past images.
In step S906, as in step S207, the processing function 44 executes the setting function 447 to determine a new shooting condition.
In step S907, the RIS transmits the determined imaging range and X-ray conditions, and the imaging order for the subject P to the X-ray CT apparatus 1.

In step S908, as in step S205, the X-ray CT apparatus 1 images the current position of the subject P using a camera.
In step S909, the X-ray CT apparatus 1 sets the imaging range to the current position of the subject P using the imaging order received from the RIS, the determined imaging range, and the X-ray conditions.
In step S910, the main scan is executed based on the imaging range determined in step S909 and the X-ray conditions received from the RIS.

According to the second embodiment described above, similarly to the first embodiment, it is possible to reduce the exposure in the positioning imaging, and the imaging planning apparatus executes the processing for determining the imaging conditions (imaging range and X-ray conditions). I do. This eliminates the need to perform the determination processing on the X-ray CT apparatus side, and can share the processing. Therefore, the speed of the above-described determination processing can be increased according to the processing capacity of the imaging planning apparatus without excessively requesting the performance of the processing circuit of the X-ray CT apparatus.
It should be noted that the past image is an X-ray image or CT image captured in a standing or sitting position, and the image is converted even when the imaging state is different, such as when a new CT image is in a supine position or vice versa. Thus, the current body thickness can be estimated.

  For example, a conversion table relating to the correction amount of the organ position (organ sag) corresponding to two combinations of the standing position, the sitting position, and the lying position is created in advance. The processing circuit 44 may refer to the photographing state of the past image and the new photographed image and the conversion table.

  The X-ray CT apparatus includes a Rotate / Rotate-Type (3rd generation CT) in which an X-ray tube and a detector rotate integrally around a subject P, and a large number of X-ray detection elements arrayed in a ring shape. There are various types such as Stationary / Rotate-Type (fourth generation CT) in which only the X-ray tube rotates around the subject P, and any type can be applied to the present embodiment.

  The hardware that generates X-rays is not limited to the X-ray tube 11. For example, instead of the X-ray tube 11, a focus coil for focusing an electron beam generated from an electron gun, a deflection coil for electromagnetic deflection, and an electron beam that deflects around a half circumference of the subject P and deflects X-rays. X-rays may be generated using a fifth generation method including a target ring to be generated.

  Further, in the present embodiment, a so-called multi-tube X-ray CT apparatus in which a plurality of pairs of an X-ray tube and a detector are mounted on a rotating ring, as well as a single-tube X-ray CT apparatus. Applicable.

  In addition, each function according to the embodiment can also be realized by installing a program for executing the processing on a computer such as a workstation and expanding the program on a memory. At this time, a program capable of causing the computer to execute the method can be stored in a storage medium such as a magnetic disk (such as a hard disk), an optical disk (such as a CD-ROM or a DVD), or a semiconductor memory and distributed. .

  While some embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 X-ray CT apparatus 10 Mount apparatus 11 X-ray tube 12 X-ray detector 13 Rotating frame 14 X-ray high-voltage apparatus 15 Controller 16 Wedge 17 Collimator 18 Data acquisition device (DAS)
19 Opening (bore)
Reference Signs List 30 bed apparatus 31 base 32 bed driving apparatus 33 top plate 34 support frame 40 console apparatus 41 memory 42 display 43 input interface 44 processing circuit 70 projector 90 photography planning apparatus 95 external storage 441 system control function 442 preprocessing function 443 reconstruction processing Function 444 Search Function 445 Acquisition Function 446 Calculation Function 447 Setting Function 601, 602 Conversion Table

Claims (10)

An X-ray tube for irradiating X-rays,
A detector for detecting X-rays emitted from the X-ray tube and transmitted through the subject;
The most recent first past image of the past images taken by the other medical image diagnostic apparatus and the imaging conditions of the first past image, and the other medical image diagnostic apparatus taking the image before the first past image An acquisition unit configured to acquire the acquired second past image, the imaging condition of the second past image, and the imaging condition of the third past image that is a CT image acquired in the past;
From the second past image to the first past image, based on the first past image and / or the shooting condition of the first past image and the shooting condition of the second past image and / or the second past image. A calculating unit for calculating the amount of change of
A setting unit configured to set a new imaging condition when imaging the CT image of the subject based on the imaging condition of the third past image and the change amount;
X-ray CT apparatus comprising:   The X-ray CT apparatus according to claim 1, wherein the change amount includes information on a body thickness of the subject.   The X-ray CT apparatus according to claim 2, wherein the information on the body thickness of the subject is any one of a virtual aluminum equivalent, a water equivalent thickness, and an estimated subject thickness.   4. The setting unit according to claim 1, wherein the setting unit sets the new imaging condition with reference to a conversion table regarding conversion of imaging conditions between the X-ray CT apparatus and the other medical image diagnostic apparatus. An X-ray CT apparatus according to claim 1. The acquisition unit acquires the first past image and the second past image,
The calculation unit calculates, as the change amount, a change amount of the position of the body of the subject by comparing the second past image and the first past image,
The apparatus according to claim 1, wherein the setting unit sets a new imaging range when imaging a CT image of the subject based on an imaging range of the third past image and an amount of change in a position of the body of the subject. The X-ray CT apparatus according to claim 4.   The X-ray CT apparatus according to claim 5, wherein the setting unit performs at least one of an enlargement process, a reduction process, a rotation process, and a morphing process on the third past image when setting the imaging range.   The X-ray CT apparatus according to claim 5, further comprising a projector configured to project the new imaging range onto the subject.   The controller according to any one of claims 1 to 7, further comprising: a control unit that notifies an alert when a period between the shooting date of the second past image and the shooting date of the third past image is equal to or longer than a threshold. An X-ray CT apparatus according to the item.   2. The control apparatus according to claim 1, further comprising: a control unit configured to notify an alert when an amount of change in the size of the subject between the time of capturing the second past image and the time of capturing the third past image is equal to or greater than a threshold. 9. The X-ray CT apparatus according to any one of 8. The most recent first past image of the past images taken by the other medical image diagnostic apparatus and the imaging conditions of the first past image, and the other medical image diagnostic apparatus taking the image before the first past image An acquisition unit configured to acquire the acquired second past image, the imaging condition of the second past image, and the imaging condition of the third past image that is a CT image acquired in the past;
From the second past image to the first past image, based on the first past image and / or the shooting condition of the first past image and the shooting condition of the second past image and / or the second past image. A calculating unit for calculating the amount of change of
A setting unit configured to set a new imaging condition when imaging a CT image of a subject based on the imaging condition of the third past image and the change amount;
An imaging planning device comprising: