JP2020058418A - X-ray CT system and CT scan execution program - Google Patents

Abstract

To improve the efficiency of contrast examination.SOLUTION: An X-ray CT system according to the embodiment includes a scan unit, an image generation unit and an analysis unit. The scan unit executes the first scan including irradiation and detection of an X-ray. The image generation unit generates a plurality of images corresponding to a plurality of time phases on the basis of a plurality of detection data sets corresponding to the plurality of time phases collected by the first scan. The analysis unit divides at least a portion of each of the plurality of images into a plurality of sections, extracts at least one region by integrating the sections having the same or similar time change of pixel values and compares information indicating the feature of the region with reference information. The scan unit executes the second scan including irradiation and detection of the X-ray in accordance with the result of comparison.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to an X-ray CT (Computed Tomography) system and a CT scan execution program.

  There is a medical image diagnostic apparatus that generates medical image data in which a body tissue of a subject is imaged. Examples of the medical image diagnostic apparatus include an X-ray CT system and an MRI (Magnetic Resonance Imaging) system. The X-ray CT system generates CT image data and volume data of an axial tomographic image of the subject based on an electric signal based on the X-ray detected by the X-ray detector by irradiating the subject with X-rays.

  Conventionally, an imaging method called a dynamic scan is performed in the X-ray CT system. The dynamic scan is a method in which after the contrast agent is administered, the scan is continuously performed for a predetermined time according to the speed of the contrast agent flowing in the subject. The X-ray CT system generates non-contrast image data of a subject in a non-contrast state, sets a region of interest (ROI) and a threshold value based on the non-contrast image data, and starts injection of a contrast agent. . Then, the X-ray CT system starts real prep after starting the injection of the contrast agent. The real prep is to detect the start timing (trigger) of the main scan before the main scan such as dynamic scan, and to start the main scan when the CT value in the ROI exceeds a threshold value.

JP, 2005-213749, A

  The problem to be solved by the present invention is to improve the efficiency of contrast examination.

  The X-ray CT system according to the embodiment has a scan unit, an image generation unit, and an analysis unit. The scan unit executes a first scan including irradiation and detection of X-rays. The image generation unit generates a plurality of images corresponding to a plurality of time phases based on a plurality of detection data sets corresponding to a plurality of time phases collected by the first scan. The analysis unit divides at least a part of each of the plurality of images into a plurality of sections and integrates sections having the same or similar temporal changes in pixel values to extract at least one area and information indicating the characteristics of the areas. And compare the reference information. The scanning unit executes a second scan including irradiation and detection of X-rays according to the comparison result.

FIG. 1 is a schematic diagram showing the configuration of an X-ray CT system according to an embodiment. FIG. 2 is a block diagram showing the configuration and functions of the X-ray CT system according to the embodiment. FIG. 3 is a view showing an operation of the X-ray CT system according to the embodiment as a flowchart. FIG. 4 is a diagram showing an operation of the X-ray CT system according to the embodiment as a flowchart. FIG. 5 is a diagram showing a section into which a target area for fractionation is divided in the abdominal contrast image data generated by the X-ray CT system according to the embodiment. FIG. 6 is a diagram showing divisions into which the fractionation target region is divided in the contrast image data of the head generated by the X-ray CT system according to the embodiment. FIG. 7 is a diagram showing a first example of an integrated region generated by the X-ray CT system according to the embodiment. FIG. 8 is a diagram showing a second example of an integrated region generated by the X-ray CT system according to the embodiment. FIG. 9 is a diagram showing an example of TDC in the X-ray CT system according to the embodiment.

  Hereinafter, embodiments of an X-ray CT system and a CT scan execution program will be described in detail with reference to the drawings.

  The data acquisition method by the X-ray CT system includes a rotation / rotation (RR) method in which an X-ray source and an X-ray detector rotate as a unit around the subject, and a ring shape. There are various methods such as a fixed / rotation (SR: Stationary / Rotate) method in which a large number of detection elements are arrayed in the array and only the X-ray tube rotates around the subject. The present invention can be applied to either method. Hereinafter, in the X-ray CT system according to the embodiment, a case will be described as an example in which the third-generation rotation / rotation method, which is currently the mainstream, is adopted.

1. Embodiment FIG. 1 is a schematic diagram showing the configuration of an X-ray CT system according to the embodiment. FIG. 2 is a block diagram showing the configuration and functions of the X-ray CT system according to the embodiment.

  FIG. 1 shows an X-ray CT system 1. The X-ray CT system 1 includes a gantry device 10, a bed device 30, and a medical image processing device according to the first embodiment, that is, a console device 40. The gantry device 10 and the bed device 30 are installed in an examination room. The gantry device 10 acquires X-ray detection data (also referred to as “pure raw data”) regarding the subject (eg, patient) P placed on the bed device 30. The console device 40 generates raw data by preprocessing the detection data for a plurality of views, and reconstructs and displays the CT image data by performing reconstruction processing on the raw data.

  Note that, in FIG. 1, for convenience of description, a plurality of gantry devices 10 are drawn on the upper and lower sides on the left side, but the actual configuration is one gantry device 10.

  The gantry device 10 includes an X-ray source (for example, an X-ray tube) 11, an X-ray detector 12, a rotating unit (for example, a rotating frame) 13, an X-ray high voltage device 14, a control device 15, a wedge 16, a collimator 17, A data acquisition circuit (DAS: Data Acquisition System) 18 is provided. The gantry device 10 is an example of a gantry unit.

  The X-ray tube 11 is provided on the rotating frame 13. The X-ray tube 11 is a vacuum tube that generates X-rays by radiating thermoelectrons from the cathode (filament) to the anode (target) by applying a high voltage from the X-ray high voltage device 14. For example, the X-ray tube 11 includes a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermoelectrons.

  It should be noted that in the embodiment, both a single-tube type X-ray CT system and a so-called multi-tube type X-ray CT system in which a plurality of pairs of an X-ray tube and an X-ray detector are mounted on a rotating ring. Applicable. The X-ray source 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 that converges an electron beam generated from an electron gun, a deflection coil that electromagnetically deflects, and a target that generates an X-ray by colliding a deflected electron beam that surrounds a half circumference of the patient P X-rays may be generated by a fifth generation method including a ring. The X-ray tube 11 is an example of an X-ray irradiation unit.

  The X-ray detector 12 is provided on the rotating frame 13 so as to face the X-ray tube 11. The X-ray detector 12 detects the X-rays emitted from the X-ray tube 11 and outputs detection data corresponding to the X-ray dose to the DAS 18 as an electric signal. The X-ray detector 12 has, for example, a plurality of X-ray detection element arrays in which a plurality of X-ray detection elements are arranged in the channel direction along one arc centering on the focal point of the X-ray tube. The X-ray detector 12 has, for example, a structure in which a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in the channel direction are arranged in the slice direction (row direction, row direction).

  The X-ray detector 12 is, for example, an indirect conversion type detector having a grid, a scintillator array, and an optical sensor array. The scintillator array has a plurality of scintillators, and the scintillator has a scintillator crystal that outputs a photon amount of light according to the incident X-ray dose. The grid is arranged on the X-ray incident side surface of the scintillator array, and has an X-ray shield having a function of absorbing scattered X-rays. The grid may be called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has a function of converting into an electric signal according to the amount of light from the scintillator, and has, for example, a photosensor such as a photomultiplier tube (photomultiplier: PMT).

  The X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts an incident X-ray into an electric signal. The X-ray detector 12 is an example of an X-ray detector.

  The rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 so as to face each other. The rotating frame 13 is an annular frame that rotates the X-ray tube 11 and the X-ray detector 12 as a unit under the control of the controller 15 described later. In addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 may further include and support an X-ray high voltage device 14 and a DAS 18. The rotating frame 13 is an example of a rotating unit.

  As described above, the X-ray CT system 1 rotates the rotating frame 13 that supports the X-ray tube 11 and the X-ray detector 12 so as to face each other, and rotates the rotating frame 13 around the patient P. Collect 360 ° of detection data. The CT image data reconstruction method is not limited to the full-scan reconstruction method using the detection data of 360 °. For example, the X-ray CT system 1 may employ a half-reconstruction method that reconstructs CT image data based on detection data corresponding to a half circumference (180 °) + fan angle.

  The X-ray high voltage device 14 is provided in the rotating frame 13 or a non-rotating portion (for example, a fixed frame not shown) that rotatably supports the rotating frame 13. The X-ray high-voltage device 14 has electric circuits such as a transformer and a rectifier. The X-ray high voltage device 14 is controlled by a control device 15 described later and a high voltage generator (not shown) having a function of generating a high voltage applied to the X-ray tube 11, and a control device 15 described later. Below, there is an X-ray controller (not shown) that controls the output voltage according to the X-rays emitted by the X-ray tube 11. The high voltage generator may be a transformer type or an inverter type. In FIG. 1, the X-ray high voltage device 14 is arranged at a position in the positive direction of the x-axis with respect to the X-ray tube 11 for convenience of description. You may arrange | position in the position of a direction.

  The control device 15 has a processing circuit and a memory, and a drive mechanism such as a motor and an actuator. The configurations of the processing circuit and the memory are the same as those of the processing circuit 44 and the memory 41 of the console device 40 which will be described later, and thus the description thereof will be omitted.

  The control device 15 has a function of receiving an input signal from an input interface, 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 bed device 30. For example, the control device 15 receives an input signal to rotate the rotating frame 13, tilts the gantry device 10, and controls the bed device 30 and the top plate 33 to operate. 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 attached to the gantry device 10 so that the control device 15 rotates about the axis parallel to the X-axis direction. It is realized by rotating. The control device 15 may be provided in the gantry device 10 or the console device 40. The control device 15 is an example of a control unit.

  Further, the control device 15 controls the rotation angle of the X-ray tube 11 and the wedge 16 and the collimator 17 which will be described later, based on the imaging conditions input from an input interface which will be described later and which is attached to the console device 40 or the gantry device 10. Control movements.

  The wedge 16 is provided on the rotating frame 13 so as to be arranged on the X-ray emission side of the X-ray tube 11. The wedge 16 is a filter for adjusting the X-ray dose emitted from the X-ray tube 11 under the control of the controller 15. Specifically, the wedge 16 is a filter that transmits and attenuates the X-rays emitted from the X-ray tube 11 so that the X-rays emitted from the X-ray tube 11 to the patient P have a predetermined distribution. Is. For example, the wedge 16 (a wedge filter or a bow-tie filter) is a filter made of aluminum so as to have a predetermined target angle or a predetermined thickness.

  The collimator 17 is also called an X-ray diaphragm or slit, and is provided on the rotating frame 13 so as to be arranged on the X-ray emission side of the X-ray tube 11. The collimator 17 is a lead plate or the like for narrowing down the irradiation range of the X-rays transmitted through the wedge 16 under the control of the controller 15, and forms an X-ray irradiation opening by a combination of a plurality of lead plates or the like.

  The DAS 18 is provided on the rotating frame 13. The DAS 18 is an amplifier that performs an amplification process on an electric signal output from each X-ray detection element of the X-ray detector 12 under the control of the control device 15, and a digital signal that controls the electric signal under the control of the control device 15. It has an A / D (Analog to Digital) converter for converting into a signal and generates detection data after amplification and digital conversion. The detection data for a plurality of views generated by the DAS 18 is transferred to the console device 40.

  Here, the detection data generated by the DAS 18 is transmitted from a transmitter having a light emitting diode (LED) provided in the rotating frame 13 to a receiver having a photodiode provided in a fixed frame of the gantry device 10 by optical communication. And transferred to the console device 40. The method of transmitting the detection data from the rotary frame 13 to the fixed frame of the gantry device 10 is not limited to the optical communication described above, and any method may be adopted as long as it is non-contact data transmission. The rotating frame 13 is an example of a rotating unit.

  The couch device 30 includes a base 31, a couch driving device 32, a top plate 33, and a support frame 34. The bed device 30 is a device on which the patient P to be scanned is placed and, under the control of the control device 15, the patient P is moved.

  The base 31 is a housing that supports the support frame 34 so as to be movable in the vertical direction (y-axis direction). The bed driving device 32 is a motor or an actuator that moves the top plate 33 on which the patient P is placed in the long axis direction (z-axis direction) of the top plate 33. The top plate 33 provided on the upper surface of the support frame 34 is a plate having a shape on which the patient P can be placed.

  The bed driving device 32 may move the support frame 34 in the long axis direction (z-axis direction) of the top plate 33 in addition to the top plate 33. The bed driving device 32 may be moved together with the base 31 of the bed device 30. When the present invention is applied to the upright CT, the patient moving mechanism corresponding to the top plate 33 may be moved. Further, when performing imaging involving a relative change in the positional relationship between the imaging system of the gantry device 10 and the top plate 33, such as a helical scan or a scano imaging for positioning, the relative change in the positional relationship is not performed. It may be performed by driving the top plate 33, traveling by the fixed portion of the gantry device 10, or a combination thereof.

  In the embodiment, the longitudinal direction of the rotary shaft of the rotary frame 13 or the top plate 33 of the bed apparatus 30 in the non-tilted state is the z-axis direction, orthogonal to the z-axis direction, and the axial direction that is horizontal to the floor surface. Axial directions orthogonal to the x-axis direction and the z-axis direction and perpendicular to the floor surface are defined as the y-axis direction.

  The console device 40 has a configuration as a computer, and includes a memory 41, a display 42, an input interface 43, and a processing circuit 44. Although the console device 40 is described separately from the gantry device 10, the gantry device 10 may include the console device 40 or a part of each component of the console device 40. Further, in the following description, it is assumed that the console device 40 executes all the functions on a single console, but these functions may be executed by a plurality of consoles. The console device 40 is an example of a medical image processing device.

  The memory 41 is composed of, for example, a semiconductor memory device such as a RAM (Random Access Memory) or a flash memory (Flash Memory), a hard disk, an optical disk, or the like. The memory 41 may be composed of a USB (Universal Serial Bus) memory and a portable medium such as a DVD (Digital Video Disk). The memory 41 stores various processing programs used in the processing circuit 44 (including an OS (Operating System) in addition to application programs) and data necessary for executing the programs. Further, the OS may include a GUI (Graphic User Interface) that uses graphics for displaying information on the display 42 to the operator and can perform basic operations with the input interface 43.

  The memory 41 stores, for example, detection data before preprocessing, raw data after preprocessing and before reconstruction, and CT image data after reconstruction based on the raw data. The pre-processing means at least one of logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, beam hardening processing, etc. for the detection data. In addition, a cloud server connectable to the X-ray CT system 1 via a communication network such as the Internet receives a storage request from the X-ray CT system 1 and stores detection data, raw data, or CT image data. May be done.

  The memory 41 also includes an image storage area for storing CT image data as medical image data, an evaluation value storage area for storing evaluation values described below, and a sensitivity parameter for storing sensitivity parameters described below. And at least a storage area (shown in FIG. 2). The memory 41 is an example of a storage unit.

  The display 42 displays various information. For example, the display 42 outputs CT image data generated by the processing circuit 44, GUI (Graphical User Interface) for receiving various operations from the user, and the like. For example, the display 42 is a liquid crystal display, a CRT (Cathode Ray Tube) display, an OLED (Organic Light Emitting Diode) display, or the like. Further, the display 42 may be provided on the gantry device 10. Further, the display 42 may be a desktop type, or may be a tablet terminal or the like capable of wireless communication with the console device 40 main body. The display 42 is an example of a display unit.

  The input interface 43 includes an input device that can be operated by an operator such as a technician, and an input circuit that inputs a signal from the input device. The input device is a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad for performing an input operation by touching an operation surface, a touch screen in which a display screen and a touch pad are integrated, and a non-contact using an optical sensor. It is realized by a contact input circuit, a voice input circuit, or the like. When the input device receives an input operation from the operator, the input circuit generates an electric signal according to the input operation and outputs the electric signal to the processing circuit 44. Further, the input interface 43 may be provided in the gantry device 10. Further, the input interface 43 may be composed of a tablet terminal or the like that can wirelessly communicate with the console device 40 main body. The input interface 43 is an example of an input unit.

  The console device 40 may include a network interface (not shown). The network interface is composed of connectors that meet parallel connection specifications and serial connection specifications. When the X-ray CT system 1 is provided on the medical image system, the network interface transmits / receives information to / from an external device on the network. For example, the network interface receives an inspection order related to a CT inspection from an external device under the control of the processing circuit 44, and also detects the detection data acquired by the X-ray CT system 1, the generated raw data or the CT image. Send data to an external device.

  The processing circuit 44 controls the overall operation of the X-ray CT system 1. The processing circuit 44 means a processor such as a dedicated or general-purpose CPU (Central Processing Unit), MPU (Micro Processor Unit), or GPU (Graphics Processing Unit), as well as an ASIC and a programmable logic device. Examples of the programmable logic device include a simple programmable logic device (SPLD: Simple Programmable Logic Device), a complex programmable logic device (CPLD: Complex Programmable Logic Device), and a field programmable gate array (FPGA). Can be mentioned.

  Further, the processing circuit 44 may be configured by a single circuit, or may be configured by a combination of a plurality of independent processing circuit elements. In the latter case, the memory may be provided individually for each processing circuit element, or a single memory may store a program corresponding to the functions of a plurality of processing circuit elements.

  By executing the program stored in the memory 41, the processing circuit 44 realizes a scan function 441, an image generation function 442, an analysis function 443, a combining function 444, and a display control function 445, as shown in FIG. . Note that all or part of the functions 441 to 445 is not limited to being realized by executing the program of the console device 40, and may be provided in the console device 40 as a circuit such as an ASIC. . Further, all or part of the functions 441 to 445 may be realized not only by the console device 40 but also by the control device 15.

  The scan function 441 controls the gantry device 10, the couch device 30, and the like via the control device 15 according to preset scan conditions to execute a CT scan including irradiation and detection of X-rays. Includes a function to collect detection data for multiple views. Further, for example, the scan condition includes the tube current mA, the tube voltage kV, the X-ray intensity control condition (X-ray modulation condition), the rotation speed of the X-ray tube 11 (or the rotating frame 13), and the like regarding the irradiation X-ray. .

  Here, the CT scan in the embodiment includes a prescan, a real prep scan, a main scan, and the like. The scan function is an example of the scan unit. The real prep scan is an example of the first scan, and the main scan is an example of the second scan.

  The image generation function 442 has a function of collecting raw data of a plurality of views by performing preprocessing on the detection data of a plurality of views collected by the scan by the scan function 441, and a function of collecting the raw data of the plurality of views after the preprocessing. And a function of generating a plurality of CT image data corresponding to a plurality of time phases by an image reconstruction process on the raw data of. The image generation function 441 also stores each CT image data in the memory 41, displays each CT image data as a CT image on the display 42, and transmits each CT image data via a network interface (not shown). It may also include a function of transmitting the data to an external device. The image generation function 441 is an example of an image generation unit.

  The analysis function 443 divides at least a part of each of the plurality of CT image data stored in the memory 41 (hereinafter, referred to as “fractionation target area”) into a plurality of sections, and the time change of the pixel value is the same or similar. It includes a function of extracting at least one area (hereinafter, referred to as “integrated area”) by integrating the sections. The analysis function 443 also includes a function of comparing the information indicating the characteristics of the integrated area with the reference information.

  Here, the analysis function 443 sets the entire image of the CT image data as a segmentation target region, and extracts the integrated region by segmenting the entire image. Alternatively, the analysis function 443 sets a region of interest (ROI) in the image of the CT image data as a segmentation target region, and extracts the integrated region by segmenting the ROI. When the inside of the ROI is fractionated, it is not affected by the pixel values outside the ROI, so that the accuracy of the integration process in the subsequent stage is improved. Hereinafter, unless otherwise specified, a case will be described in which the analysis function 443 uses the ROI as a segmentation target region and fractionates the inside of the ROI.

  In addition, the information indicating the characteristics of the integrated region is at least one of information about the pixel value (for example, CT value) of a pixel included in the integrated region, information about the size of the integrated region, and information about the shape of the integrated region. Including. The reference information includes at least one of information about the pixel value of the blood vessel, information about the size of the blood vessel, and information about the shape of the blood vessel. The analysis function 443 compares the information about the size of the integrated region with the information about the size of the blood vessel. For example, in the case of the ascending aorta, the blood vessel size is less than 3 [cm] in the abdomen and less than 1 [cm] in the neck. Further, the analysis function 443 compares the information about the size of the integrated area with the information about the size of the blood vessel, and compares the information about the shape of the integrated area with the information about the shape of the blood vessel. The analysis function 443 is an example of an analysis unit.

  Then, the scan function 441 executes a main scan including X-ray irradiation and detection according to the result of the comparison by the analysis function 443. That is, the scanning function 441 analyzes the analysis function 443 so that the accuracy of the information regarding the size of the integrated region obtained from the CT image data with respect to the information regarding the size of the blood vessel is equal to or greater than a preset threshold value, or the accuracy is set to When it is determined that the number exceeds the limit, the start timing of the main scan is detected. When the scan function 441 detects the start timing of the main scan, the scan function 441 controls the gantry device 10, the bed device 30 and the like via the control device 15 according to a preset scan condition to execute the main scan.

  The synthesizing function 444 includes a function of synthesizing at least one of the plurality of CT image data generated by the image generating function 442 with the integrated region extracted by the analysis function 443 to generate synthetic image data. The combining function 444 is an example of a combining unit.

  The display control function 445 includes a function of displaying the combined image data generated by the combining function 444 on the display 42. The display control function 445 is an example of the display control unit.

  The operations of the functions 441 to 445 will be described later with reference to FIGS.

  3 and 4 are diagrams showing the operation of the X-ray CT system 1 as a flowchart. In FIG. 3 and FIG. 4, each step of the code flowchart in which “ST” is numbered is shown.

  First, FIG. 3 will be described. The scan function 441 controls the gantry device 10, the bed device 30 and the like via the control device 15 according to a preset scan condition before the real prep scan and the main scan, thereby performing a pre-scan for the patient P without imaging. Execute (step ST1).

  The image generation function 442 generates non-contrast image data based on the data collected by the gantry device 10 by the prescan (step ST2). The non-contrast image data generated in step ST2 is displayed on the display 42 as a non-contrast image and / or stored in the memory 41.

  The analysis function 443 sets the ROI as the fractionation target region so as to include the blood vessel region based on the non-contrast image data generated in step ST2 (step ST3). For example, in step ST3, the analysis function 443 displays the non-contrast image data on the display 42, and based on the input signal input by the operator via the input interface 43 while watching the non-contrast image data displayed on the display 42. And set the ROI.

  The analysis function 443 sets the size or number of sections that divide the ROI (step ST4). For example, in step ST4, the analysis function 443 sets the size or the number of sections dividing the ROI based on the input signal input by the operator via the input interface 43. When the partition size in the ROI is set, the number of partitions is also determined, and when the number of partitions in the ROI is set, the partition size is also determined.

  The analysis function 443 may set a value set in advance for each imaging region by setting the size or number of sections that divide the ROI, and / or the ROI set in step ST3. It may be set according to the size of. The minimum unit of the partition size is a pixel.

  The section size (or the number of sections) is set so that the accuracy can be ensured according to the blood vessel size to be detected. For example, when the detected blood vessel size is relatively large, the partition size is set large (or the number of partitions is small), while when the detected blood vessel size is relatively small, the partition size is small (or the number of partitions). Is set).

  The scan function 441 starts the injection of the contrast agent (step ST5), and controls the gantry device 10, the bed device 30, and the like via the control device 15 according to the preset scan condition, thereby performing the prep scan for the patient P. Start (step ST6). For example, in step ST5, the scan function 441 starts the injection of the contrast agent based on the input signal input by the operator via the input interface 43.

  The image generation function 442 generates contrast image data by real-time reconstruction based on the data collected by the gantry device 10 by the prep scan (step ST7). The image generation function 442 causes the display 42 to display the contrast image data generated in step ST7 as a contrast image and stores the contrast image data in the memory 41 (step ST8).

  Moving to the description of FIG. 4, the analysis function 443 determines whether the ROI of the contrast image data of the latest frame generated in step ST7 and the ROI of the contrast image data of the past (for example, the immediately preceding frame) stored in the memory 41. And are divided into a plurality of sections according to the setting of step ST4 (step ST9).

  FIG. 5 is a diagram showing divisions into which the fractionation target region is divided in the abdominal contrast image data. FIG. 5A is a diagram showing the ROI set in the contrast image data. FIG. 5 (B) is a diagram showing a section for dividing the ROI in FIG. 5 (A). FIG. 5C is a diagram showing a section that divides the entire image of the contrast image data.

  FIG. 6 is a diagram showing divisions into which a target area for division is divided in contrast image data of the neck. FIG. 6A is a diagram showing the ROI set in the contrast image data. FIG. 6 (B) is a diagram showing sections that divide the ROI of FIG. 6 (A). FIG. 6C is a diagram showing a section that divides the entire image of the contrast image data.

  When the number or size of the sections is set, the sections are arranged in the ROI as shown in FIGS. 5B and 6B. Further, when the number or size of the sections is set when the ROI is not set, the sections are arranged in the entire image of the contrast image data as shown in FIGS. 5 (C) and 6 (C). It should be noted that, in the plurality of sections within the region, the size of the end section is appropriately adjusted.

  Returning to the explanation of FIG. 4, the analysis function 443 measures the time change of the representative pixel value (for example, the average pixel value) of the pixel group existing in each section in the ROI (step ST10). Examples of the representative pixel value include an average pixel value that is the average value of the pixel values that the pixel group shows, a maximum pixel value that is the maximum pixel value that the pixel group shows, and a minimum value of the pixel values that the pixel group shows. An example is a minimum pixel value. Hereinafter, a case where the representative pixel value is the average pixel value will be described as an example. In step ST10, the analysis function 443 measures the time change of the average pixel value of the pixel group existing in each section in the ROI by the difference processing between the contrast image data of the latest frame and the contrast image data of the past frame. .

  In addition, when the segmentation target region is the entire image and the entire image is segmented into a plurality of sections, the analysis function 443 performs the difference processing between the contrast image data of the latest frame and the contrast image data of the past frame. In addition, it is preferable to correct the positional deviation between both image data. For example, the analysis function 443 performs a correction for performing a linear conversion on the image so as to match the local areas of the image data, as the positional deviation correction between the image data. The analysis function 443 corrects the positional deviation between the two pieces of image data, and divides each corrected image as a whole into a plurality of sections.

  The analysis function 443 integrates (groups) the sections whose pixel values have the same or similar temporal changes to generate an integrated area (step ST11). In step ST11, the analysis function 443 sets, for example, a boundary threshold value for classifying each section into one of a plurality of levels, and determines which level each section belongs to. The boundary threshold value may be a fixed value or may be changed according to the elapsed time from the start of injection of the contrast agent. Further, the analysis function 443 sets in advance a predetermined range of the time change of the average pixel value in consideration of the elapsed time from the start of the injection of the contrast agent, and integrates only the sections having the average pixel value within the range. Can be Thereby, the load of the integration process can be reduced.

  FIG. 7 is a diagram showing a first example of the integrated area. FIG. 7A is a diagram showing an integrated region within the ROI in the contrast image data of the neck. FIG. 7B is a diagram showing an integrated region of the entire image in the contrast image data of the neck. FIG. 7C is contrasted with FIGS. 7A and 7B and is a reference diagram showing an integrated region of the entire image in the non-contrast image data of the neck.

  FIG. 7 (A) is an integrated region when the fractionation target region is the ROI, and shows an integrated region L1 caused by the contrast agent. The integrated region L1 is a set of a plurality of sections having an average pixel value between the lower limit threshold and the upper limit threshold in the ROI. On the other hand, FIG. 7B shows an integrated region L2 including the integrated region L1 caused by the contrast agent, which is an integrated region when the fractionation target region is the entire image. The integrated region L2 is a set of a plurality of sections having an average pixel value between the lower limit threshold and the upper limit threshold in the entire image. The integrated areas L1 and L2 are generated for each frame (for each thinned frame).

  Comparing FIGS. 7A and 7B, FIG. 7A in which the fractionation target region is set as the ROI is the integration outside the ROI caused by the body movement of the patient P shown in FIG. 7B. This is advantageous in that the area can be excluded.

  Returning to the description of FIG. 4, the combining function 444 combines the contrast image data generated in step ST7 of FIG. 3 with the integrated region (illustrated in FIGS. 7A and 7B) generated in step ST11. Then, composite image data is generated (step ST12). The display control function 445 causes the display 42 to display the combined image data generated in step ST12 as a combined image (step ST13). In step ST13, the display control function 445 can also cause the display 42 to color-display the portion (illustrated in FIGS. 7A and 7B) of the integrated area of the combined image data. The display control function 445 may display the integrated area generated in step ST11 on the display 42 alone. In that case, the display control function 445 can also individually display the integrated area (shown in FIGS. 7A and 7B) in color on the display 42.

  The analysis function 443 compares the information indicating the characteristics of the integrated area generated in step ST11 with the reference information (step ST14). In step ST14, for example, the analysis function 443 obtains the blood vessel-likeness of the information indicating the characteristics of the integrated region, that is, the accuracy of the information indicating the characteristics of the integrated area with respect to the blood vessel, and compares the accuracy with a threshold value.

  In step ST14, the analysis function 443 performs a process of generating the accuracy of the information indicating the characteristic of the integrated region with respect to the blood vessel, based on the information indicating the characteristic of the integrated region. This processing may be performed by automatic recognition such as matching with an atlas (standard organ) image, or by CNN (convolutional neural network) or convolutional deep belief network (CDBN). Alternatively, it may be performed by deep learning using a multilayer neural network.

  As a result of the comparison in step ST14, the analysis function 443 determines whether or not the accuracy of the information indicating the characteristics of the integrated region with respect to the blood vessel is equal to or higher than the threshold (or exceeds the threshold) (step ST15). If the determination in step ST15 is NO, that is, if the accuracy of the information indicating the characteristics of the integrated region with respect to the blood vessel is less than (or less than) the threshold value, contrast image data is generated for the next frame. (Step ST7 of FIG. 3).

  On the other hand, if YES in the determination in step ST15, that is, if the accuracy of the information indicating the characteristics of the integrated region with respect to the blood vessel is equal to or greater than (or exceeds) the threshold value, the scan function 441 is set in advance. By controlling the gantry device 10, the bed device 30, and the like via the control device 15 according to the scan conditions described above, the main scan for the patient P is performed (step ST16). It should be noted that the plurality of contrast image data generated by the prep scan and the image data generated based on the detection data set collected by the main scan are provided as separate series on DICOM (Digital Imaging and COmmunications in Medicine). It is preferably stored in the memory 41. That is, the X-ray CT system 1 can manage a plurality of contrast image data generated by the prep scan and the image data generated by the main scan as separate series.

  Note that, when the analysis function 443 generates a plurality of integrated regions having different levels of difference in average pixel values, it is determined that the accuracy of information indicating one of the features of the plurality of integrated regions is equal to or higher than a threshold value. Sometimes it is enough to shift to the main scan.

  FIG. 8 is a diagram showing a second example of the integrated area. FIG. 8A is a diagram showing an integrated region in the ROI in the contrast image data of the neck. FIG. 8B is a diagram showing an integrated region of the entire image in the contrast image data of the neck. 8C is contrasted with FIGS. 8A and 8B and is a reference diagram showing an integrated region of the entire image in the non-contrast image data of the neck.

  FIG. 8A is an integrated region when the fractionation target region is the ROI, and shows a plurality of integrated regions Ls1 caused by the contrast agent. On the other hand, FIG. 8B shows a plurality of integrated regions Ls2 including a plurality of integrated regions Ls1 caused by the contrast agent, which are integrated regions when the fractionation target region is the entire image. The integrated regions Ls1 and Ls2 are generated for each frame (for each thinned frame).

  In step ST12 of FIG. 4, the combining function 444 combines the contrast image data with the integrated areas shown in FIGS. 8A and 8B to generate combined image data, and the display control function 445 causes the display control function 445 of FIG. In step ST13, the composite image data may be displayed on the display 42 as a composite image. In this case, the display control function 445 causes the display 42 to color-display the portion of the integrated area of the combined image data (shown in FIGS. 8A and 8B) and according to the magnitude of the difference between the average pixel values. The color (any of hue, saturation, and lightness) can be changed. The display control function 445 may cause the display 42 to display the integrated area alone. In this case, the display control function 445 causes the display 42 to display the integrated region (shown in FIGS. 8A and 8B) alone in color, and also to display the color (hue, Either the saturation or the brightness) can be changed.

  Returning to the explanation of FIG. 4, even when it is determined that the accuracy of the information indicating the characteristics of the integrated region with respect to the reference information is equal to or greater than the threshold value, the analysis function 443 determines the fraction measured in step ST10. When the temporal change of the average pixel value in the target area shows a high value, it may be determined as NO in the determination in step ST16, assuming that the patient P has moved.

  As described above, the X-ray CT system 1 uses the reference information (ideal blood vessel at the time of inflow of a contrast agent) of the reference information (pixel value or the like) indicating the characteristics of the integrated region in the fractionation target region (for example, ROI). When the accuracy of the pixel value etc.) is high, the main scan is performed. With this configuration, even when the patient P moves, it is possible to detect an increase in the pixel value due to the contrast agent. In addition, even when it is difficult to set the ROI at an appropriate position on the image of the non-contrast image data with an appropriate size, such as when imaging the neck, it is appropriate within the roughly set ROI. Since the timing of transition to the main scan can be measured by performing various processes, the load of ROI operation can be reduced.

2. Modifications Up to this point, the case where the analysis function 443 measures the time change of the average pixel value of the pixel group existing in each section in the image data between two frames has been described, but the invention is not limited to this case. . The analysis function 443 may measure the time change of the average pixel value of the pixel group existing in each section in the image data for three or more frames. The analysis function 443 can use TDC (Time-Density Curve) as the time change of the average pixel value of the pixel group existing in each section in the image data for three or more frames. For example, the analysis function 443 generates the TDC for each frame based on the average pixel value of the pixel group existing in each section in the ROI as the division target area, and the difference between the TDC and the ideal TDC is The same or similar sections are integrated.

  FIG. 9 is a diagram showing an example of TDC. FIG. 9A shows TDC in a section. FIG. 9B shows an ideal TDC in the blood vessel region.

  The analysis function 443 compares the TDC shown in FIG. 9 (A) with the portion of the ideal TDC shown in FIG. 9 (B) corresponding to the frame, and thereby, The difference can be calculated.

  According to the configuration of the modification of the X-ray CT system 1, the same effects as those of the X-ray CT system 1 described above can be obtained from the image data of 3 frames or more.

  The scan function 441 is an example of a scan unit. The image generation function 442 is an example of an image generation unit. The analysis function 443 is an example of an analysis unit. The combining function 444 is an example of a combining unit. The display control function 445 is an example of a display control unit.

  According to at least one embodiment described above, the efficiency of contrast examination can be improved.

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

1 X-ray CT system 40 console device (medical image processing device)
44 processing circuit 441 scan function 442 image generation function 443 analysis function 444 composition function 445 display control function

Claims (11)

A scan unit for performing a first scan including irradiation and detection of X-rays;
An image generation unit that generates a plurality of images corresponding to the plurality of time phases based on a plurality of detection data sets corresponding to the plurality of time phases collected by the first scan;
At least a part of each of the plurality of images is divided into a plurality of sections, and at least one area is extracted by integrating sections whose pixel values have the same or similar temporal changes, and reference is made to information indicating characteristics of the areas. An analysis unit that compares information,
Equipped with
The scan unit executes a second scan including irradiation and detection of X-rays according to a result of the comparison.
X-ray CT system. The information indicating the characteristic of the area includes at least one of information about a pixel value of a pixel included in the area, information about a size of the area, and information about a shape of the area.
The X-ray CT system according to claim 1. The analysis unit divides the entire images of the plurality of images to extract the region,
The X-ray CT system according to claim 1. The analysis unit corrects the positional deviation of the plurality of images, fractionates the entire images of the corrected plurality of images, and extracts the region.
The X-ray CT system according to claim 1. The analysis unit divides a region of interest in each image of the plurality of images to extract the region,
The X-ray CT system according to claim 1. At least one of the plurality of images, and a combining unit that combines the regions to generate a combined image,
A display control unit for displaying the composite image on a display unit,
The X-ray CT system according to any one of claims 1 to 5, further comprising: The images generated based on the plurality of images and the detection data set collected by the second scan are managed as separate series,
The X-ray CT system according to any one of claims 1 to 6. The analysis unit presets a predetermined range of time change of pixel values, and sets only sections having pixel values within the range as integration targets.
The X-ray CT system according to any one of claims 1 to 7. The analysis unit sets a section size or the number of sections, and sets the plurality of sections according to the set section size or the set number of sections,
The X-ray CT system according to any one of claims 1 to 8. The analysis unit sets the section size or the number of sections according to an imaging region,
The X-ray CT system according to claim 9. On the computer,
The ability to perform a first scan that includes X-ray irradiation and detection;
A function of generating a plurality of images corresponding to the plurality of time phases based on a plurality of detection data sets corresponding to the plurality of time phases collected by the first scan;
At least a part of each of the plurality of images is divided into a plurality of sections, and at least one area is extracted by integrating sections whose pixel values have the same or similar temporal changes, and reference is made to information indicating characteristics of the areas. The ability to compare information,
A function of performing a second scan including irradiation and detection of X-rays according to the result of the comparison;
A CT scan execution program that realizes