X-ray CT scanner, imaging method, and imaging program

Abstract

To realize a safe, inexpensive CT examination.SOLUTION: An X-ray CT apparatus according to the present embodiment includes a setting unit, a collection unit, and a generation unit. The setting unit sets a plurality of energy bands for discriminating blood. The collection unit is configured to collect spectral data obtained by counting, based on the plurality of energy bands, X-ray photons that have passed through the subject, by performing a CT scan using an X-ray detector while a liquid having X-ray permeability higher than the blood has been injected in a blood vessel. A generation unit generates a medical image in which the blood vessel has been emphasized based on the collected spectral data.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments disclosed in the present specification and drawings relate to an X-ray CT apparatus, an imaging method, and an imaging program. [Background Art]

[0002] In X-ray CT apparatuses, there is an imaging technique in which a contrast medium such as iodine or gadolinium, which absorbs more X-rays than blood, is administered to a patient for visualizing blood vessel courses and lesions. It is necessary to consider side effects of contrast media on the human body, so contrast media cannot be administered to patients with allergies. Furthermore, there is a limit to the dose of contrast medium that can be administered, and due to the daily allowable dose restriction, contrast medium cannot be administered multiple times in a single imaging session. Therefore, if an image in a desired imaging time phase cannot be acquired, contrast-enhanced imaging needs to be performed again, which imposes a burden on the patient. Furthermore, since the contrast medium itself is expensive, there is a problem that it increases the pressure on medical costs. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese National Publication of International Patent Application No. 2018-515160 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] One of the problems to be solved by the embodiments disclosed in the present specification and drawings is to realize a safe and inexpensive CT examination. However, the problems to be solved by the embodiments disclosed in the present specification and drawings are not limited to the above problem. Problems corresponding to respective effects achieved by respective configurations shown in the embodiments described later can also be regarded as other problems. [Means for Solving the Problem]

[0005] The X-ray CT apparatus according to this embodiment includes a setting unit, an acquisition unit, and a generation unit. The setting unit sets a plurality of energy bands for discriminating blood. The acquisition unit collects spectral data by counting X-ray photons that have passed through the subject based on the plurality of energy bands, using a CT scan with an X-ray detector while a liquid with higher X-ray transparency than blood is injected into the blood vessels. The generation unit generates a medical image that highlights the blood vessels based on the collected spectral data. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a block diagram showing an X-ray CT apparatus according to this embodiment. [Figure 2] Figure 2 is a flowchart showing an example of the operation of the X-ray CT apparatus according to this embodiment. [Figure 3] Figure 3 shows an example of energy bin settings in photon counting processing. [Figure 4] Figure 4 shows an example of determining the start timing of contrast imaging according to this embodiment. [Figure 5] Figure 5 shows an example of determining the start timing of contrast imaging according to this embodiment. [Figure 6] Figure 6 shows a first example of how to set and display the shooting protocol according to this embodiment. [Figure 7] Figure 7 shows a second example of how to set and display the shooting protocol according to this embodiment. [Figure 8] Figure 8 shows an example of a contrast-enhanced image according to this embodiment. [Figure 9] Figure 9 shows an example of a contrast-enhanced image when calcification is present in a blood vessel. [Figure 10] Figure 10 shows an example of a contrast-enhanced image in which the vascular region is displayed in a manner similar to a general contrast-enhanced image. [Modes for carrying out the invention]

[0007] The X-ray CT (Computed Tomography) apparatus, imaging method, and imaging program according to this embodiment will be described below with reference to the drawings. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate. One embodiment will be described below with reference to the drawings.

[0008] The X-ray CT apparatus according to this embodiment will be described below with reference to the block diagram in Figure 1. The X-ray CT apparatus 1 shown in Figure 1 includes a gantry unit 10, a patient table unit 30, and a console unit 40 that performs processing for the X-ray CT apparatus. For illustrative purposes, multiple gantry units 10 are shown in Figure 1.

[0009] In this embodiment, the rotation axis of the rotating frame 13 or the longitudinal direction of the top plate 33 of the bed device 30 in the non-tilted state is defined as the Z-axis direction, the axis direction perpendicular to the Z-axis direction is defined as the X-axis direction, the axis direction horizontal to the floor surface is defined as the Z-axis direction, the axis direction perpendicular to the floor surface is defined as the Y-axis direction.

[0010] For example, the rigging system 10 and the patient bed system 30 are installed in the CT examination room, and the console system 40 is installed in a control room adjacent to the CT examination room. However, the console system 40 does not necessarily have to be installed in the control room. For example, the console system 40 may be installed in the same room as the rigging system 10 and the patient bed system 30. In any case, the rigging system 10, the patient bed system 30, and the console system 40 are connected to each other by wired or wireless means so that they can communicate with one another.

[0011] The rigging device 10 is a scanning device configured for X-ray CT imaging of a subject P. The rigging 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 acquisition device 18 (hereinafter also referred to as DAS (Data Acquisition System) 18).

[0012] The X-ray tube 11 is a vacuum tube that generates X-rays by irradiating thermionic electrons from the cathode (filament) to the anode (target) by applying a high voltage from the X-ray high-voltage device 14 and supplying filament current. Specifically, X-rays are generated when thermionic electrons collide with the target. 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 thermionic electrons. The X-rays generated in the X-ray tube 11 are shaped into a cone beam via, for example, a collimator 17 and irradiated onto the subject P.

[0013] In this embodiment, the X-ray detector 12 is assumed to be a photon-counting type detector. The X-ray detector 12 detects X-rays irradiated from the X-ray tube 11 and passed through the subject P on a photon basis. The X-ray detector 12 has, for example, multiple rows of X-ray detection elements arranged in the channel direction along a single arc centered on the focal point of the X-ray tube 11. The X-ray detector 12 has, for example, a column structure in which multiple rows of X-ray detection elements, each arranged in the channel direction, are arranged in the slice direction (column direction, row direction).

[0014] Specifically, the X-ray detector 12 is an indirect conversion type detector having, for example, a grid, a scintillator array, and a photosensor array. The X-ray detector 12 is an example of a detection unit.

[0015] A scintillator array has multiple scintillators. The scintillators convert incident X-rays into a number of photons corresponding to the intensity of the incident X-rays. The grid is positioned on the X-ray incident side of the scintillator array and has an X-ray shielding plate that absorbs scattered X-rays. The grid is sometimes also called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has the function of amplifying the light received from the scintillator and converting it into an electrical signal, generating an output signal (energy signal) with a pulse height corresponding to the energy of the incident X-rays. For example, it includes optical sensors such as photomultipliers (PMTs). The generated energy signal is output to DAS18.

[0016] It should be noted that although the above-described X-ray detector 12 is assumed to be an indirect conversion type detector, it may also be a direct conversion type detector having a semiconductor element that converts incident X-rays into electrical signals.

[0017] The rotating frame 13 rotatably supports the X-ray generating unit (the X-ray tube 11, the wedge 16 and the collimator 17) and the X-ray detector 12 around the rotation axis. Specifically, the rotating frame 13 is an annular frame that oppositely supports the X-ray tube 11 and the X-ray detector 12, and rotates the X-ray tube 11 and the X-ray detector 12 under the control of the control device 15 described later. The rotating frame 13 is rotatably supported by a fixed frame (not shown) formed of metal such as aluminum. More specifically, the rotating frame 13 is connected to the edge of the fixed frame via a bearing. The rotating frame 13 receives power from the driving mechanism of the control device 15 and rotates at a constant angular velocity around the rotation axis Z.

[0018] In addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 further includes and supports the X-ray high-voltage device 14 and the DAS 18. Such a rotating frame 13 is accommodated in a substantially cylindrical housing formed with an opening (bore) 19 that forms an imaging space. The opening substantially coincides with the field of view (FOV) for imaging. The central axis of the opening coincides with the rotation axis Z of the rotating frame 13. It should be noted that the imaging data generated by the DAS 18 is transmitted, for example, by optical communication from a transmitter having a light emitting diode (LED) to a receiver (not shown) having a photodiode provided at a non-rotating portion of the gantry device (e.g., the fixed frame, not shown in Fig. 1), and then transferred to the console device 40. The method for transmitting imaging data from the rotating frame to the non-rotating portion of the gantry device is not limited to the above-described optical communication, and any non-contact data transmission method may be employed.

[0019] The X-ray high-voltage device 14 includes an electrical circuit such as a transformer and a rectifier, a high-voltage generator that generates the high voltage applied to the X-ray tube 11 and the filament current supplied to the X-ray tube 11, and an X-ray control device that controls the output voltage according to the X-rays irradiated by the X-ray tube 11. The high-voltage generator may be of the transformer type or the inverter type. The X-ray high-voltage device 14 may be installed on the rotating frame 13, which will be described later, or on the fixed frame (not shown) side of the mounting device 10.

[0020] The control device 15 includes a processing circuit having a CPU (Central Processing Unit), etc., and a drive mechanism such as a motor and actuator. The processing circuit has a processor such as a CPU or MPU (Micro Processing Unit) and memory such as ROM (Read Only Memory) or RAM (Random Access Memory) as hardware resources. The control device 15 may also be implemented using an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), another Complex Programmable Logic Device (CPLD), or a Simple Programmable Logic Device (SPLD). The control device 15 controls the X-ray high-voltage device 14 and DAS 18, etc., according to commands from the console device 40. The processor implements the above control by reading a program stored in the memory.

[0021] Furthermore, the control device 15 has the function of controlling the operation of the frame device 10 and the bed device 30 by receiving input signals from an input interface 43, which will be described later, attached to the console device 40 or the frame device 10. For example, the control device 15 receives input signals and controls the rotation of the rotating frame 13, the tilt of the frame device 10, and the operation of the bed device 30 and the top plate 33. The control of tilting the frame device 10 is achieved by the control device 15 rotating the rotating frame 13 around an axis parallel to the X-axis direction based on the tilt angle information input by the input interface 43 attached to the frame device 10. The control device 15 may be provided on the frame device 10 or on the console device 40. The control device 15 may be configured to directly incorporate the program into the processor circuit instead of saving the program in the memory. In this case, the processor realizes the above control by reading and executing the program incorporated into the circuit.

[0022] The wedge 16 is a filter used to adjust the amount of X-rays irradiated from the X-ray tube 11. Specifically, the wedge 16 is a filter that transmits and attenuates the X-rays irradiated from the X-ray tube 11 so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution. For example, the wedge 16 (wedge filter, bow-tie filter) is a filter made of aluminum processed to have a predetermined target angle and a predetermined thickness.

[0023] The collimator 17 is a lead plate or the like used to narrow the irradiation area of ​​the X-rays that have passed through the wedge 16, and a slit is formed by combining multiple lead plates or the like. The collimator 17 is sometimes also called an X-ray diaphragm.

[0024] The DAS18 is implemented, for example, by an ASIC (Application Specific Integrated Circuit) equipped with circuit elements capable of generating imaging data. The DAS18 and the X-ray detector 12 constitute a detector unit. If the X-ray detector 12 is a photon counting type detector, the DAS18 generates digital data (hereinafter also referred to as spectral data) indicating the count of X-rays detected by the X-ray detector 12 for each of several energy bands (hereinafter, energy bands are also referred to as energy bins or simply bins). The spectral data is a set of data of count values ​​identified by the channel number, column number, view number (also referred to as projection angle) of the source detector element, and bin number. The spectral data is transferred to the console device 40.

[0025] The patient bed device 30 is a device for placing and moving the subject P to be scanned, and comprises a base 31, a patient bed drive device 32, a top plate 33, and a support frame 34.

[0026] The base 31 is a housing that supports the support frame 34 so that it can move in the vertical direction. The patient bed drive device 32 is a motor or actuator that moves the tabletop 33 on which the subject P is placed in the direction of the long axis of the tabletop 33. The patient bed drive device 32 moves the tabletop 33 according to the control of the console device 40 or the control device 15. For example, the patient bed drive device 32 moves the tabletop 33 in a direction perpendicular to the subject P so that the body axis of the subject P placed on the tabletop 33 coincides with the central axis of the opening of the rotating frame 13. Alternatively, the patient bed drive device 32 may move the tabletop 33 along the body axis of the subject P in accordance with the X-ray CT imaging performed using the rigging device 10. The patient bed drive device 32 generates power by driving at a rotational speed corresponding to the duty cycle of the drive signal from the control device 15. The patient bed drive device 32 is implemented by a motor such as a direct drive motor or a servo motor.

[0027] The top plate 33, provided on the upper surface of the support frame 34, is a plate on which the subject P is placed. In addition to moving the top plate 33, the bed drive device 32 may also move the support frame 34 along the long axis of the top plate 33.

[0028] The console device 40 includes a memory 41, a display 42, an input interface 43, and a processing circuit 44. Data communication between the memory 41, the display 42, the input interface 43, and the processing circuit 44 is performed via a bus (BUS). Although the console device 40 is described separately from the mounting device 10, the mounting device 10 may include the console device 40 or some of its components.

[0029] Memory 41 is a storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or integrated circuit memory device that stores various types of information. For example, memory 41 stores imaging data and reconstructed image data. In addition to HDDs and SSDs, memory 41 may also be a drive device that reads and writes various types of information to portable storage media such as CDs (Compact Discs), DVDs (Digital Versatile Discs), flash memory, or semiconductor memory elements such as RAM (Random Access Memory). Furthermore, the storage area of ​​memory 41 may be located within the X-ray CT apparatus 1 or in an external storage device connected via a network. For example, memory 41 stores data for CT images and displayed images. Memory 41 also stores the control program according to this embodiment.

[0030] The display 42 displays various types of information. For example, the display 42 outputs medical images generated by the processing circuit 44, a GUI (Graphical User Interface) for receiving various operations from the operator, etc. For example, the display 42 can be a liquid crystal display (LCD), a CRT (Cathode Ray Tube) display, an organic electroluminescent display (OELD), a plasma display, or any other display as appropriate. The display 42 may also be mounted on the stand device 10. The display 42 may be a desktop type, or it may consist of a tablet terminal that can communicate wirelessly with the console device 40.

[0031] The input interface 43 receives various input operations from the operator, converts the received input operations into electrical signals, and outputs them to the processing circuit 44. For example, the input interface 43 receives from the operator the acquisition conditions when acquiring imaging data, the reconstruction conditions when reconstructing CT images, and the image processing conditions when generating post-processed images from CT images. The input interface 43 can be, for example, a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display, as appropriate. In this embodiment, the input interface 43 is not limited to those equipped with physical operating components such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display. For example, an electrical signal processing circuit that receives electrical signals corresponding to input operations from an external input device separate from the device and outputs these electrical signals to the processing circuit 44 is also included as an example of the input interface 43. The input interface 43 may be provided on the mounting device 10. Furthermore, the input interface 43 may consist of a tablet terminal or the like that can communicate wirelessly with the console device 40.

[0032] The processing circuit 44 controls the operation of the entire X-ray CT apparatus 1 in accordance with the electrical signals of input operations output from the input interface 43. For example, the processing circuit 44 has a processor such as a CPU, MPU, or GPU (Graphics Processing Unit) and memory such as ROM or RAM as hardware resources. The processing circuit 44 executes system control functions 441, setting functions 442, acquisition functions 443, generation functions 444, judgment functions 445, and display control functions 446 using a processor that executes a program loaded into memory. Note that each function (system control function 441, setting function 442, acquisition function 443, generation function 444, judgment function 445, and display control function 446) is not limited to being implemented by a single processing circuit. A processing circuit may be configured by combining multiple independent processors, and each function may be implemented by each processor executing a program.

[0033] The system control function 441 controls each function of the processing circuit 44 based on input operations received from the operator via the input interface 43. Specifically, the system control function 441 reads the control program stored in the memory 41, loads it onto the memory within the processing circuit 44, and controls each part of the X-ray CT apparatus 1 according to the loaded control program. For example, the processing circuit 44 controls each function of the processing circuit 44 based on input operations 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 to determine the scan range, imaging conditions, etc. The positioning image is also called a scan image or scout image. The system control function 441 is an example of a system control unit.

[0034] The setting function 442 sets multiple energy bands for discriminating blood types. The acquisition function 443 drives the X-ray tube 11 and the X-ray detector 12, and while a liquid with higher X-ray transparency than blood is injected into the blood vessels of the subject, a CT scan is performed using the X-ray detector 12 to acquire spectral data by counting the X-ray photons that have passed through the subject based on multiple energy bands. In this embodiment, the description assumes that physiological saline is used as the liquid injected into the blood vessels, but the liquid may also be artificial blood containing a preparation made of perfluorocarbon (PFC), for example. In other words, any liquid that has less impact on the human body, such as allergies, and has higher X-ray transparency than blood is acceptable. Positioning images may also be acquired using the acquisition function 443.

[0035] The generation function 444 generates medical images that highlight blood vessels based on the collected spectral data. For example, the generation function 444 generates medical images by performing reconstruction processing using methods such as filtered back projection (FBP) or iterative reconstruction.

[0036] The determination function 445 determines whether or not a medical image has been acquired at a desired time phase after the injection of the liquid.

[0037] The display control function 446 controls the display 42 to display information about the processing in progress or results of each function or process of the processing circuit 44. Specifically, if a medical image has not been acquired at the desired time phase, it displays information to assist in reinjecting the fluid into the blood vessel. When displaying events in the imaging protocol in chronological order, it displays symbols indicating events related to fluid injection on the chronological order.

[0038] Furthermore, the processing circuit 44 also performs scan control processing and image processing. The scan control process is a process that controls various operations related to X-ray scanning, such as supplying high voltage to the X-ray high-voltage device 14 to irradiate the X-ray tube 11 with X-rays. Image processing is the process of converting CT image data generated by the generation function 444 based on input operations received from the operator via the input interface 43 into tomographic image data or 3D image data of an arbitrary cross-section. The generation of tomographic image data or 3D image data may also be performed directly by the generation function 444.

[0039] The processing circuit 44 is not limited to being included in the console device 40; it may also be included in an integrated server that performs processing on data acquired by multiple medical imaging diagnostic devices in a unified manner. Although the console device 40 has been described as performing multiple functions on a single console, it is also acceptable for multiple functions to be performed by separate consoles. Furthermore, the functions of the processing circuit 44 may be distributed among multiple consoles.

[0040] Next, an example of the operation of the X-ray CT apparatus 1 according to this embodiment will be explained with reference to the flowchart in Figure 2. Here, we assume that the blood vessels of the subject to be injected with saline solution have been secured and that the subject has been positioned on the tabletop 33 of the examination table 30. While the following assumes a helical scan method, a conventional scan (volume scan) using a two-dimensionally arranged X-ray detector may also be used.

[0041] In step S201, the processing circuit 44 performs positional imaging of the subject via the system control function 441 or the acquisition function 443. In step S202, the processing circuit 44 uses the setting function 442 to set the bins based on the data obtained from positional imaging. Specifically, the bins are set so that the iron component of hemoglobin contained in red blood cells can be detected. Since the size and quantity of red blood cells vary from subject to subject, positional imaging can be used as calibration to set the bins based on spectral data.

[0042] In step S203, the processing circuit 44 performs plain radiography using the acquisition function 443 and collects pre-contrast imaging data. The medical images generated from the pre-contrast imaging data obtained by plain radiography are intended to be used, for example, for comparison and analysis with medical images based on subsequent contrast-enhanced radiography. Note that if the positioning images obtained by positioning radiography are used for comparison and analysis with medical images based on contrast-enhanced radiography, step S203 may be omitted. In step S204, saline solution is injected. For example, the system control function 441 may instruct an automatic injector (not shown) to inject saline solution, or a healthcare professional may inject saline solution as appropriate.

[0043] In step S205, the processing circuit 44 performs contrast imaging using physiological saline via the acquisition function 443. Specifically, the processing circuit 44, via the acquisition function 443, takes images when physiological saline is present in the blood vessels within the imaging field of view. In step S206, the processing circuit 44 determines, based on the determination function 445, whether or not the acquisition of the desired contrast-enhanced image has been completed. Specifically, it determines whether or not a contrast-enhanced image at the desired time phase after the injection of saline solution has been obtained. If the desired contrast-enhanced image has been obtained, the process is terminated. If the desired contrast-enhanced image has not been obtained, the process returns to step S204, saline solution is injected again, and the same process is repeated. While there are daily limits on the amount of contrast agents such as iodine that can be injected into blood vessels, it is generally considered safe to inject a certain amount of physiological saline into the bloodstream each day. Therefore, it is possible to inject physiological saline multiple times during a single contrast imaging procedure, allowing for contrast imaging at the desired time phase.

[0044] Next, we will explain an example of bin configuration with reference to Figure 3. Figure 3 is a graph showing the X-ray attenuation curve of the iron (Fe) component, with the vertical axis representing the mass attenuation coefficient and the horizontal axis representing the photon energy. Different energy bands are set up on both sides of the k-edge of the iron atom contained in hemoglobin in the blood. In the example in Figure 3, bottle 301 is set to the left of the photon energy E2 of the k-edge Q, i.e., in the energy band E1-E2 where the photon energy is low, and bottle 302 is set to the right of E2, i.e., in the energy band E2-E3 where the photon energy is high. This allows for the identification of the target iron component. Furthermore, if bottles 301 and 302 are wide, there will be less difference in the counts measured in each bottle. Narrowing the bottle width will make the difference more apparent, and thus make substance discrimination easier.

[0045] Next, an example of determining the start timing for contrast imaging in step S205 will be explained with reference to Figures 4 and 5. Figure 4 shows the time-density curve (TDC) when the count value of the vascular region included in the measurement site after injecting physiological saline into the blood vessel is monitored over time, with the vertical axis representing the count value (or substance index) and the horizontal axis representing time.

[0046] In this embodiment, since the bottle is set for the iron component contained in blood, physiological saline, which is a liquid with higher X-ray transparency than blood, is not counted in the bottle. Therefore, the count value in the area where physiological saline is present is less than the count value in the area where blood is present.

[0047] Therefore, the processing circuit 44, using the acquisition function 443, if the count value is below the threshold 401, which is the lower limit of the count value in which blood is assumed to be flowing, assumes that there is no blood in the vascular region included in the measurement target area within the imaging field, that is, physiological saline is present, and starts the main imaging to obtain spectral data.

[0048] In other words, as shown by the dashed line in Figure 4, the main imaging should start when the TDC first falls below the threshold of 401. The main imaging may be started manually by the user by pressing the execute button, or the processing circuit 44 may be configured to perform imaging when the TDC falls below the threshold of 401.

[0049] In contrast imaging, the main scan is initiated when the CT value exceeds a threshold, indicating that the contrast agent has reached the ROI. Therefore, the vertical axis is reversed compared to the TDC display method shown in Figure 4. As shown in Figure 5, the vertical axis of TDC in Figure 4 may be inverted, with the upper part of the vertical axis representing lower count values ​​and the lower part representing higher count values. This allows users to understand the timing of the main scan in a similar way to general contrast imaging.

[0050] Next, a first example of how to set and display the shooting protocol, such as scan conditions, according to this embodiment will be described with reference to Figures 6 and 7. Figure 6 shows an example of events in an imaging protocol (also called an expert plan or simply a protocol) displayed in chronological order, with the vertical axis representing dose and the horizontal axis representing time.

[0051] In the example in Figure 6, the imaging protocol is designed for contrast-enhanced liver imaging, and the timing of imaging for positioning, fluid injection (saline injection), early arterial phase, late arterial phase, venous phase, and portal venous phase is indicated by rectangular icons. The action of injecting saline into a blood vessel is indicated by a triangular icon 601. Icon 601 may be displayed in a shape corresponding to the amount and rate of saline solution injection. For example, if the amount of saline solution to be injected is large, the size of icon 601 can be increased, and if the amount to be injected is small, the size of icon 601 can be decreased. Also, if the rate of saline solution injection is fast, for example, the angle of the vertex of the isosceles triangle of icon 601 can be decreased, and if the rate of saline solution injection is fast, the angle of the vertex of the isosceles triangle of icon 601 can be increased. In this way, the user can intuitively understand the amount and rate of saline solution to be injected.

[0052] While icon 601 is assumed to be triangular in this context, it may be represented by any symbol, including squares, circles, arrows, text indicating vascular injection, or combinations thereof.

[0053] By setting icon 601 on the time series of the imaging protocol shown in Figure 6, the user can, for example, have the processing circuit 44, via the system control function 441, determine the imaging timing for the early phase, late phase, portal venous phase, etc., after saline injection, and display it as an imaging protocol as shown in Figure 6.

[0054] Furthermore, saline solution can be injected again during imaging in a single examination. Therefore, the processing circuit 44 may generate and automatically display additional imaging protocols (hereinafter referred to as additional protocols) using the system control function 441 and the display control function 446.

[0055] As a second example of the method for setting and displaying the shooting protocol according to this embodiment, Figure 7 shows an example of displaying an additional protocol. Figure 7 shows a time-series display of the imaging protocol, similar to that in Figure 6. When icon 601 is placed on the time-series display, the system control function 441 causes the processing circuit 44 to set an additional protocol 701 for the time phases where imaging is not expected to be possible with the first saline injection, and displays the additional protocol 701 as an icon on the time-series display. At this time, timings 702 in which saline injection should be avoided can also be set.

[0056] Furthermore, when icon 601 is set, the processing circuit 44 may automatically set the additional protocol 701 via the display control function 446, or it may present the additional protocol 701 as a candidate and ask the user whether or not to implement the additional protocol 701. Alternatively, the processing circuit 44 may present multiple additional protocols 701 via the display control function 446, allowing the user to select the desired additional protocol 701 from among them.

[0057] By setting or presenting additional protocol 701 in this way, even if, for example, the early and late phases were captured but the mid-phase timing was not, the physiological saline can be injected again and only the mid-phase can be captured again, thereby efficiently obtaining the desired medical image. Furthermore, by injecting saline solution multiple times and acquiring contrast-enhanced images at each time phase within predetermined time intervals, it is possible to distinguish the timing of saline solution circulating through arteries, veins, and tumors. This allows for the generation of 3D or 4D medical images to understand the blood flow status of organs or lesions, similar to general contrast-enhanced videos.

[0058] Next, an example of a contrast-enhanced image according to this embodiment is shown in Figure 8. Because the system is set to detect the iron content of blood, areas where saline solution is present in blood vessels will have low count values. When a medical image is reconstructed from spectral data, these blood vessel areas will appear black. This allows users to easily recognize blood vessel areas based on the contrast between the defective areas and other areas.

[0059] Furthermore, Figure 9 shows an example of a contrast-enhanced image according to this embodiment when calcification is present in the blood vessels. In contrast-enhanced images using a typical iodine contrast agent, the calcified areas have CT values ​​similar to those of the contrast agent, making it difficult to distinguish between the contrast-enhanced area and the calcified areas. In contrast, this embodiment generates contrast-enhanced images in which the vascular region is displayed in black, allowing for a clear distinction between the calcified area 901 and the vascular region, as shown in Figure 9.

[0060] Furthermore, the vascular region may be displayed in white, as is common with contrast-enhanced images using conventional contrast agents. An example of a contrast-enhanced image according to this embodiment, in which the vascular region is displayed in white, is shown in Figure 10. For example, the display control function 446 allows the processing circuit 44 to invert the brightness values ​​below a threshold in the medical image shown in Figure 8, i.e., to invert the black and white, thereby generating a medical image with a display pattern similar to that of a typical contrast agent, as shown in Figure 10.

[0061] Alternatively, a pre-trained model that has been machine-learned to enable segmentation of blood vessels may be used to extract vascular regions and obtain results in which the vascular regions are colored. For example, the processing circuit 44, using the generation function 444, can take a CT (Computed Tomography) image as input data, and use a pre-trained model that has been trained on a neural network using images in which the vascular regions contained in the CT image have been segmented as ground truth data, to input a medical image into the pre-trained model, thereby extracting the vascular regions contained in the medical image. Note that a CT image refers to an image in which a CT value is assigned to each pixel.

[0062] According to the embodiment described above, instead of a substance that absorbs X-rays more than blood, such as iodine, a liquid that transmits X-rays more than blood and is less harmful to the subject, such as physiological saline, is injected into the blood vessel. The bottle is set up to visualize the distribution of hemoglobin in the blood, and X-ray imaging is performed using the photon counting method while the liquid is present in the imaging field. A medical image is generated from the spectral data. In this medical image, because the hemoglobin component in the blood is pushed aside by the liquid, when imaged, the defective areas appear black and uncolored. As a result, a contrast-enhanced image with inverted contrast from a typical contrast-enhanced image can be obtained, eliminating the disadvantages of typical contrast agents such as iodine while ensuring the same level of visibility as a typical contrast-enhanced image. While conventional contrast agents have daily limits on their administration due to potential side effects, liquids such as physiological saline can be administered multiple times a day, significantly reducing the risk of allergic reactions. Furthermore, because physiological saline can be injected multiple times, even if an initial scan fails, it can be re-injected with physiological saline until the desired phase of the medical image is obtained, thus greatly reducing the burden on both the patient and the user. In short, it enables safe and inexpensive CT scans.

[0063] In the above description, the term "processor" refers to circuits such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an Application Specific Integrated Circuit (ASIC), or a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)). When the processor is a CPU, for example, it performs its functions by reading and executing a program stored in a memory circuit. On the other hand, when the processor is an ASIC, for example, instead of the program being stored in a memory circuit, the function is directly incorporated as a logic circuit within the processor's circuit. In this embodiment, each processor is not limited to being configured as a single circuit; multiple independent circuits may be combined to form a single processor and perform its functions. Furthermore, multiple components shown in the figure may be integrated into a single processor to perform its functions.

[0064] In addition, each function according to the embodiment can also be realized by installing a program that performs the processing on a computer such as a workstation and loading it into memory. In this case, the program that can cause the computer to execute the method can also be stored and distributed on a storage medium such as a magnetic disk (hard disk, etc.), optical disk (CD-ROM, DVD, etc.), or semiconductor memory.

[0065] While several embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in a variety of other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0066] With respect to the above embodiments, the following additional notes are disclosed as aspects of the invention and selective features. (Note 1) A setting unit for setting multiple energy bands for discriminating blood, A collection unit collects spectral data by counting X-ray photons that have passed through the subject based on the multiple energy bands, while a liquid with higher X-ray transparency than blood is injected into the blood vessels of the subject, using a CT scan with an X-ray detector. A generation unit that generates a medical image emphasizing the blood vessels based on the collected spectral data, An X-ray CT scanner equipped with the following features.

[0067] (Note 2) The spectral data is generated from data collected at the time when the fluid is present in the blood vessels within the imaging field of view. The generation unit may generate a medical image in which the region of blood vessels within the imaging field of view is displayed darker than the surrounding region.

[0068] (Note 3) The spectral data is generated from data collected at the time when the fluid is present in the blood vessels within the imaging field of view. The generation unit may generate a medical image in which the region of blood vessels within the imaging field of view is displayed brighter than the surrounding region.

[0069] (Note 4) The aforementioned liquid may be physiological saline or artificial blood.

[0070] (Note 5) The setting unit may also include a bottle for discriminating the photon energy of the iron component in the blood.

[0071] (Note 6) The acquisition unit monitors the count value in the blood vessel region over time, and may start the main imaging to acquire the spectral data when the count value falls below a threshold.

[0072] (Note 7) A determination unit that determines whether or not a medical image has been acquired at a desired time phase after the injection of the aforementioned liquid, The system may further include a display control unit that displays information to assist in reinjecting the liquid into the blood vessel if a medical image at the desired time phase has not been acquired.

[0073] (Note 8) When displaying events in the imaging protocol in chronological order, the system may further include a display control unit that displays symbols indicating events related to the injection of the liquid on the chronological order.

[0074] (Note 9) The aforementioned symbol may be displayed in a shape corresponding to the amount and rate of injection of the liquid.

[0075] (Note 10) If a medical image at the desired time phase has not been acquired, the display control unit may display new symbols indicating the timing for reinjecting the liquid into the blood vessel and the timing for capturing the medical image at the desired time phase.

[0076] (Note 11) The generation unit may use a CT (Computed Tomography) image as input data and a trained model that has been trained using images segmented with blood vessel regions contained in the CT image as ground truth data, and then input the medical image into the trained model to extract the blood vessel regions contained in the medical image.

[0077] (Note 12) With a liquid that has higher X-ray transparency than blood injected into the blood vessels of the subject, a CT scan using an X-ray detector is performed to count the X-ray photons that have passed through the subject based on the multiple energy bands, and spectral data is collected. Based on the collected spectral data, a medical image highlighting the blood vessels is generated. Shooting method.

[0078] (Note 13) On the computer, A setting function that allows setting multiple energy bands for blood differentiation, A fluid with higher X-ray transparency than blood is injected into the blood vessels of the subject, and a CT scan using an X-ray detector collects spectral data by counting the X-ray photons that have passed through the subject based on the multiple energy bands. A generation function that generates a medical image emphasizing the blood vessels based on the collected spectral data, A shooting program that makes this a reality. [Explanation of symbols]

[0079] 1 X-ray CT device 10. Mounting device 11 X-ray tube 12 X-ray detectors 13 rotation frames 14 X-ray high-voltage equipment 15 Control device 16 Wedge 17 Collimator 18 Data Collection Device 19 Aperture 30 Bed equipment 31 base 32 Bed drive mechanism 33 Top plate 34 Support Frame 40 Console device 41 memory 42 displays 43 Input Interfaces 44 Processing Circuits 301,302 bottles 401 threshold 441 System control function 442 Settings function 443 Collection function 444 Generation function 445 Judgment function 446 Display control function 601 Icons 701 Additional Protocols 702 Timing 901 Calcified area

Claims

1. A setting unit for setting multiple energy bands for discriminating blood, Without using a contrast agent, a liquid with higher X-ray transparency than blood is injected into the blood vessels of the subject, and a CT scan using an X-ray detector collects spectral data by counting the X-ray photons that have passed through the subject based on the multiple energy bands. A generation unit that generates a medical image emphasizing the blood vessels based on the collected spectral data, An X-ray CT scanner equipped with the following features.

2. The spectral data is generated from data collected at the time when the fluid is present in the blood vessels within the imaging field of view. The X-ray CT apparatus according to claim 1, wherein the generation unit generates a medical image in which the region of blood vessels within the imaging field of view is displayed darker than the surrounding region.

3. The spectral data is generated from data collected at the time when the fluid is present in the blood vessels within the imaging field of view. The X-ray CT apparatus according to claim 1, wherein the generation unit generates a medical image in which the region of blood vessels within the imaging field of view is displayed brighter than the surrounding region.

4. The X-ray CT apparatus according to any one of claims 1 to 3, wherein the liquid is physiological saline or artificial blood.

5. The X-ray CT apparatus according to any one of claims 1 to 4, wherein the setting unit sets a bottle for discriminating the photon energy of the iron component in the blood.

6. The X-ray CT apparatus according to any one of claims 1 to 5, wherein the acquisition unit monitors the count value in the blood vessel region over time, and when the count value falls below a threshold, it starts the main imaging to acquire the spectral data.

7. A determination unit that determines whether or not a medical image has been acquired at a desired time phase after the injection of the aforementioned liquid, The X-ray CT apparatus according to any one of claims 1 to 6, further comprising: a display control unit that displays information to assist in reinjecting the liquid into the blood vessel if a medical image at the desired time phase has not been acquired.

8. The X-ray CT apparatus according to any one of claims 1 to 7, further comprising a display control unit that displays symbols indicating events related to the injection of the liquid on the time series when displaying events in the imaging protocol in chronological order.

9. The X-ray CT apparatus according to claim 8, wherein the symbol is displayed in a shape corresponding to the amount and rate of injection of the liquid.

10. The X-ray CT apparatus according to claim 8 or 9, wherein the display control unit newly displays symbols indicating the timing for reinjecting the liquid into the blood vessel and the timing for capturing the medical image in the desired phase, if a medical image has not been acquired in the desired phase.

11. The X-ray CT apparatus according to any one of claims 1 to 10, wherein the generation unit takes a CT (Computed Tomography) image as input data, and uses a trained model that has been trained with images segmented to show the blood vessel regions included in the CT image as ground truth data, and inputs the medical image into the trained model to extract the blood vessel regions included in the medical image.

12. A computer, By setting multiple energy bands for blood discrimination, Without using a contrast agent, a liquid with higher X-ray transparency than blood is injected into the blood vessels of the subject, and spectral data is collected by counting the X-ray photons that have passed through the subject based on the multiple energy bands using a CT scan with an X-ray detector. A method for generating a medical image that highlights the blood vessels based on the collected spectral data.

13. On the computer, A setting function that allows setting multiple energy bands for blood differentiation, A collection function that collects spectral data by counting X-ray photons that have passed through the subject based on multiple energy bands, while a liquid with higher X-ray transparency than blood is injected into the subject's blood vessels without using a contrast agent, and a CT scan using an X-ray detector. A generation function that generates a medical image emphasizing the blood vessels based on the collected spectral data, A shooting program that makes this a reality.

Images