X-ray CT device

Abstract

To detect an X-ray having the high independence of an observation energy spectrum.SOLUTION: An X-ray CT apparatus according to an embodiment comprises: an X-ray tube; a first X-ray detector; a rotation part; and a second X-ray detector. The X-ray tube generates the X-ray. The first X-ray detector is arranged so as to be opposed to the X-ray tube and detects the X-ray passing through a subject. The rotation part rotatably supports the X-ray tube and the first X-ray detector. The second X-ray detector detects the characteristic X-ray generated according to a substance in the subject.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray CT apparatus.

Background Art

[0002] Conventionally, an X-ray CT (Computed Tomography) apparatus is known that measures X-ray energy transmitted through a subject and identifies the content of a target substance contained in the subject using the acquired energy spectrum.

[0003] When observing as a transmission spectrum, the observed energy changes according to the response function (energy resolution, escape, pile-up) of the X-ray detector. In particular, in a living body in which a plurality of substances (in addition to the target substance, water, bone, biological tissue) are interposed, the detector response becomes a factor that reduces the independence between the target substance and other substances in the observed energy spectrum.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to detect X-rays with high independence in the observed energy spectrum. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. The problems corresponding to the respective effects of each configuration shown in the embodiments described later can also be regarded as other problems.

Means for Solving the Problems

[0006] The X-ray CT apparatus according to the embodiment comprises an X-ray tube, a first X-ray detector, a rotating unit, and a second X-ray detector. The X-ray tube generates X-rays. The first X-ray detector is positioned opposite the X-ray tube and detects the X-rays that have passed through the object. The rotating unit rotatably supports the X-ray tube and the first X-ray detector. The second X-ray detector detects characteristic X-rays generated according to the substance in the object. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the configuration of an X-ray CT apparatus according to the first embodiment. [Figure 2] Figure 2 shows an example of the configuration of a fluorescence X-ray detector according to the first embodiment. [Figure 3] Figure 3 is a diagram illustrating an example of the process by which an X-ray CT apparatus according to the first embodiment generates fusion image data. [Figure 4] Figure 4 is a flowchart showing an example of the process flow for generating fusion image data according to the first embodiment. [Figure 5] Figure 5 is a diagram illustrating the multiple X-ray fluorescence detectors included in the X-ray CT apparatus according to the second embodiment. [Figure 6] Figure 6 is a diagram illustrating the multiple X-ray fluorescence detectors included in the X-ray CT apparatus according to the fourth embodiment. [Figure 7] Figure 7 is a diagram illustrating the positional relationship between multiple X-ray fluorescence detectors and an X-ray tube, and the positional relationship between multiple X-ray fluorescence detectors and an X-ray detector, according to the fourth embodiment. [Modes for carrying out the invention]

[0008] The following description of an X-ray CT apparatus according to an embodiment will be given with reference to the drawings. Note that the embodiments are not limited to those described below. Furthermore, the contents described in one embodiment are, in principle, applicable to other embodiments as well.

[0009] Furthermore, while the following embodiments describe an X-ray CT apparatus capable of performing photon counting CT as an example, the embodiments are not limited thereto. For example, the following embodiments can also be applied to an X-ray CT apparatus equipped with an integrating type (current mode measurement method) X-ray detector.

[0010] (First embodiment) Figure 1 shows an example of the configuration of an X-ray CT apparatus 1 according to the first embodiment. As shown in Figure 1, the X-ray CT apparatus 1 according to the embodiment has a stand device 10, a patient table device 30, and a console device 40. In this embodiment, a contrast agent composed of a substance such as iodine is administered to the subject P as the subject. The X-ray CT apparatus 1 then detects fluorescent X-rays (characteristic X-rays) generated from the substances constituting the contrast agent when X-rays are irradiated onto the contrast agent and performs quantitative analysis (quantitative imaging).

[0011] In Figure 1, the rotation axis of the rotating frame 13 in the non-tilted state or the longitudinal direction of the top plate 33 of the patient device 30 is defined as the Z-axis direction. The axis direction perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction. The axis direction perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. Note that although the support device 10 is shown in two locations in Figure 1, this is for illustrative purposes, and the X-ray CT apparatus 1 has only one support device 10.

[0012] The mounting 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, an X-ray aperture 17, a DAS (Data Acquisition System) 18, and a fluorescence X-ray detector 19.

[0013] The X-ray tube 11 is a vacuum tube having a cathode (filament) that generates thermionic electrons and an anode (target) that generates X-rays upon collision with thermionic electrons. The X-ray tube 11 generates X-rays to irradiate the subject P by irradiating thermionic electrons from the cathode to the anode when a high voltage is applied from the X-ray high-voltage device 14. For example, there is a rotating anode type X-ray tube 11 that generates X-rays by irradiating a rotating anode with thermionic electrons. The subject P is an example of a subject.

[0014] The rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 opposite each other and rotates the X-ray tube 11 and the X-ray detector 12 by the control device 15. In this way, the rotating frame 13 rotatably supports the X-ray tube 11 and the X-ray detector 12. For example, the rotating frame 13 is a casting made of aluminum. In addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 can also support an X-ray high-voltage device 14, a wedge 16, an X-ray diaphragm 17, a DAS 18, etc. Furthermore, the rotating frame 13 can also support various other components not shown in Figure 1. The rotating frame 13 is an example of a rotating part.

[0015] 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 distribution of X-rays irradiated from the X-ray tube 11 to the subject P becomes a predetermined distribution. For example, the wedge 16 is a wedge filter or a bow-tie filter, which is a filter made of aluminum or the like processed to have a predetermined target angle and thickness.

[0016] The X-ray aperture 17 is a lead plate or the like for narrowing the irradiation range of the X-rays that have passed through the wedge 16, and forms slits by a combination of a plurality of lead plates or the like. Incidentally, the X-ray aperture 17 may be called a pre-collimator. Also, in FIG. 1, the case where the wedge 16 is disposed between the X-ray tube 11 and the X-ray aperture 17 is shown, but the X-ray aperture 17 may be disposed between the X-ray tube 11 and the wedge 16. In this case, the wedge 16 transmits and attenuates the X-rays irradiated from the X-ray tube 11 and whose irradiation range is limited by the X-ray aperture 17.

[0017] The X-ray high voltage device 14 has electric circuits such as a transformer and a rectifier, and includes a high voltage generator that generates a high voltage to be applied to the X-ray tube 11, and an X-ray control device that controls the output voltage according to the X-rays generated by the X-ray tube 11. The high voltage generator may be of a transformer type or an inverter type. Incidentally, the X-ray high voltage device 14 may be provided on the rotating frame 13, or may be provided on a fixed frame not shown.

[0018] The control device 15 has a processing circuit having a CPU (Central Processing Unit) or the like, and a drive mechanism such as a motor and an actuator. The control device 15 receives an input signal from the input interface 43 and controls the operations of the gantry device 10 and the bed device 30. For example, the control device 15 controls the rotation of the rotating frame 13, the tilt of the gantry device 10, the operations of the bed device 30 and the top plate 33, and the like. As an example, as control for tilting the gantry device 10, the control device 15 rotates the rotating frame 13 about an axis parallel to the X-axis direction based on the input tilt angle information. Incidentally, the control device 15 may be provided on the gantry device 10, or may be provided on the console device 40.

[0019] The X-ray detector 12 is arranged to face the X-ray tube 11 and detects the X-rays that have passed through the subject P. Each time an X-ray photon is incident, the X-ray detector 12 outputs a signal capable of measuring the energy value of the X-ray photon. The X-ray photons are, for example, the X-ray photons irradiated from the X-ray tube 11 and passed through the subject P. The X-ray detector 12 has a plurality of detection elements that output an electrical signal (analog signal) of one pulse each time an X-ray photon is incident. By counting the number of electrical signals (pulses), it is possible to count the number of X-ray photons incident on each detection element. Further, the X-ray detector 12 can measure the energy value of the X-ray photon that caused the output of this signal by performing a predetermined arithmetic processing on this signal. A collimator is installed on the X-ray incident surface side of the X-ray detector 12 to reduce scattered X-rays. The collimator may also be called a scatter removal grid or a后置 collimator.

[0020] The above-described detection element is a sensor composed of a plurality of electrodes and detects radiation. For example, the detection element is a combination of a scintillator that generates light (scintillation light) corresponding to the incident X-ray photons and a CMOS (Complementary metal-oxide-semiconductor) image sensor that converts the scintillation light into an electrical signal. That is, the X-ray detector 12 is an indirect conversion type detector that combines a phosphor that is excited by radiation to emit light and a photodetector that converts the light generated by the phosphor into an electrical signal.

[0021] The X-ray detector 12 has multiple detection elements and Application Specific Integrated Circuits (ASICs) connected to the detection elements that count the X-ray photons detected by the detection elements. The ASIC counts the number of X-ray photons incident on the detection elements by discriminating the pulse height of electrical pulses having heights proportional to the individual charge amounts output by the detection elements. The ASIC also measures the energy (energy value) of the counted X-ray photons by performing calculations based on the magnitude of each charge. Furthermore, the ASIC outputs the X-ray photon counting result as digital data to the DAS 18. The X-ray detector 12 is an example of a first type of X-ray detector. The X-ray detector 12 is a photon counting type X-ray detector.

[0022] The X-ray fluorescence detector 19 detects X-ray fluorescence generated in response to substances within the subject P. The X-ray fluorescence detector 19 detects X-ray fluorescence generated from substances constituting the contrast agent administered to the subject P when irradiated with X-rays, and outputs a signal corresponding to the X-ray dose of the detected X-ray fluorescence to the DAS 18. The X-ray fluorescence detector 19 has, for example, multiple arrays of detection elements arranged in the channel direction (channel direction) along a single arc centered on the focal point of the X-ray tube 11. The X-ray fluorescence detector 19 has, for example, a structure in which multiple arrays of detection elements, each arranged in the channel direction, are arranged in the row direction (slice direction, row direction).

[0023] The X-ray fluorescence detector 19 is positioned, for example, as shown in Figure 1, so as not to be in the path of the X-rays irradiated from the X-ray tube 11. In other words, the X-ray fluorescence detector 19 is positioned so as not to be incident on by the X-rays irradiated from the X-ray tube 11. Furthermore, the X-ray fluorescence detector 19 is positioned so as to be incident on by fluorescent X-rays generated from the substances constituting the contrast agent. In other words, the X-ray fluorescence detector 19 is positioned so as to be able to detect fluorescent X-rays among the X-rays irradiated from the X-ray tube 11 and the fluorescent X-rays. Note that fluorescent X-rays emit light isotropically in all directions and are monochromatic.

[0024] For example, the X-ray fluorescence detector 19 is an indirect conversion type detector having a scintillator array and a photosensor array. The scintillator array has multiple scintillators. The scintillators have scintillator crystals that output light in a quantity of photons corresponding to the amount of incident X-rays. The photosensor array has the function of converting the amount of light from the scintillators into an electrical signal, and has, for example, a photosensor such as a photodiode. The X-ray fluorescence detector 19 may also be a direct conversion type detector having a semiconductor element that converts incident X-rays into an electrical signal. Furthermore, the X-ray fluorescence detector 19 may also be a photon counting type X-ray detector.

[0025] Figure 2 shows an example of the configuration of the X-ray fluorescence detector 19 according to the first embodiment. As shown in Figure 2, the X-ray incident side surface of the X-ray fluorescence detector 19 is provided with an identification unit 19a that identifies the incident direction of the X-ray fluorescence detected by the X-ray fluorescence detector 19.

[0026] The identification unit 19a is, for example, a collimator that directs fluorescent X-rays only from a specific incident direction. When the identification unit 19a is a collimator, the collimator may be removable from the X-ray incident side of the fluorescent X-ray detector 19. Alternatively, a collimator appropriate for the size of the subject P may be used as the identification unit 19a.

[0027] The identification unit 19a is not limited to a collimator. For example, the identification unit 19a may have functions similar to those of a Compton camera, and this function may be used to identify the incident direction of the fluorescent X-rays detected by the fluorescent X-ray detector 19. For example, the identification unit 19a may include a scatterer and an absorber, and the incident direction of the incident fluorescent X-rays may be identified by the absorber capturing the scattered fluorescent X-rays after the fluorescent X-rays incident on the scatterer. That is, the identification unit 19a may include a scatterer and identify the incident angle of the fluorescent X-rays based on the scattering angle of the fluorescent X-rays at the scatterer. An example of such a Compton camera is the electron track detection type Compton camera (https: / / www.yamagata-u.ac.jp / jp / information / press / 20181024_01 / ). The electron track detection type Compton camera is also called an electron track type Compton camera.

[0028] DAS18 is an electronic circuit that outputs digital data based on signals output from the X-ray detector 12 and the X-ray fluorescence detector 19, respectively. For example, DAS18 generates detection data (digital data) based on the results of counting processing input from the X-ray detector 12. The detection data is, for example, a sinogram. A sinogram is data that arranges the results of counting processing incident on each detection element at each position in the X-ray tube 11. A sinogram is data that arranges the results of counting processing in a two-dimensional Cartesian coordinate system with the view direction and channel direction as axes. For example, DAS18 generates a sinogram in column units in the slice direction of the X-ray detector 12. Here, the result of the counting processing is data that assigns the number of X-ray photons for each energy bin. For example, DAS18 counts photons (X-ray photons) originating from X-rays irradiated from the X-ray tube 11 and transmitted through the subject P, and discriminates the energy of the counted X-ray photons to obtain the result of the counting processing.

[0029] Furthermore, the DAS 18 includes an amplifier that amplifies the electrical signals output from each detection element of the X-ray fluorescence detector 19, and an A / D converter that converts the electrical signals into digital signals, thereby generating detection data. If the X-ray fluorescence detector 19 is a photon counting type X-ray detector, the DAS 18 may generate detection data based on the counting results input from the X-ray fluorescence detector 19 in the same manner as the method used to generate detection data based on the counting results input from the X-ray detector 12.

[0030] In this embodiment, the X-ray fluorescence detector 19 is incident not only on the target substance (the substance that constitutes the contrast agent), but also on X-ray fluorescence from substances other than the target substance, such as X-ray fluorescence from water and X-ray fluorescence from bone. Therefore, in this embodiment, the DAS 18 generates detection data based on X-ray fluorescence with energy within the energy window corresponding to the target substance, and does not generate detection data from X-ray fluorescence with energy outside this energy window. The energy within the energy window refers to, for example, energy within the range of energy indicated by the energy window. This energy range is the energy range corresponding to the target substance. Similarly, energy outside the energy window refers to, for example, energy outside the range of energy indicated by the energy window. In this way, the DAS 18 generates detection data based on X-ray fluorescence from the target substance, among the X-ray fluorescence from the target substance and X-ray fluorescence from substances other than the target substance. Alternatively, the X-ray fluorescence detector 19 may output to the DAS 18, in a similar manner, an electrical signal based on the X-ray fluorescence emitted from the target substance, among the X-ray fluorescence emitted from substances other than the target substance. In this case, the DAS 18 generates detection data based on the electrical signal based on the X-ray fluorescence emitted from the target substance.

[0031] The DAS18 then transfers the generated detection data to the console device 40. For example, the data generated by the DAS18 is transmitted via optical communication from a transmitter having a light-emitting diode (LED) on the rotating frame 13 to a receiver having a photodiode on the non-rotating part of the mounting device 10 (e.g., a fixed frame, etc., which is not shown in Figure 1), and then transferred to the console device 40. Here, the non-rotating part is, for example, a fixed frame that rotatably supports the rotating frame 13. Note that the method of transmitting data from the rotating frame 13 to the non-rotating part of the mounting device 10 is not limited to optical communication; any non-contact data transmission method or a contact-type data transmission method may be used.

[0032] The patient bed apparatus 30 is a device for placing and moving the subject P to be photographed, and comprises a base 31, a patient bed drive device 32, a top plate 33, and a support frame 34. The base 31 is a housing that supports the support frame 34 so that it can move in the vertical direction. The patient bed drive device 32 is a drive mechanism that moves the top plate 33 on which the subject P is placed in the direction of the long axis of the top plate 33, and includes a motor and actuator, etc. The top plate 33, which is 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 patient bed drive device 32 may also move the support frame 34 in the direction of the long axis of the top plate 33.

[0033] The console device 40 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 mounting device 10, the mounting device 10 may include the console device 40 or some of its components.

[0034] Memory 41 can be implemented using, for example, semiconductor memory elements such as RAM (Random Access Memory) or flash memory, a hard disk, or an optical disc. Memory 41 stores, for example, projection data or CT image data. It can also store, for example, programs for circuits included in the X-ray CT apparatus 1 to perform their functions. Alternatively, memory 41 may be implemented using a group of servers (cloud) connected to the X-ray CT apparatus 1 via a network.

[0035] The display 42 displays various types of information. For example, the display 42 may display various images generated by the processing circuit 44, or it may display a GUI (Graphical User Interface) to receive various operations from the operator. For example, the display 42 may be a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 42 may be a desktop type, or it may be composed of a tablet terminal or the like that which can communicate wirelessly with the console device 40. The display 42 is just one example of a display unit.

[0036] 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. In addition, the input interface 43 receives input operations from the operator, such as reconstruction conditions when reconstructing CT image data, and image processing conditions when generating post-processed images from CT image data.

[0037] For example, the input interface 43 can be implemented by a mouse, keyboard, trackball, switch, button, joystick, touchpad for input operations by touching the operating surface, touchscreen with an integrated display screen and touchpad, non-contact input circuit using an optical sensor, audio input circuit, etc. The input interface 43 may also be provided on the mounting device 10. Furthermore, the input interface 43 may consist of the console device 40 main unit and a tablet terminal or the like that can communicate wirelessly. Moreover, the input interface 43 is not limited to those equipped with physical operating components such as a mouse or keyboard. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the console device 40 and outputs this electrical signal to a processing circuit 44 is also an example of an input interface 43. The input interface 43 is an example of an input unit.

[0038] The processing circuit 44 controls the operation of the entire X-ray CT apparatus 1. For example, the processing circuit 44 executes system control function 441, preprocessing function 442, reconstruction processing function 443, image processing function 444, scan control function 445, display control function 446, and fusion image generation function 447. Here, for example, each of the processing functions of the processing circuit 44 shown in Figure 1, namely system control function 441, preprocessing function 442, reconstruction processing function 443, image processing function 444, scan control function 445, display control function 446, and fusion image generation function 447, are recorded in memory 41 in the form of programs that can be executed by a computer. The processing circuit 44 is implemented, for example, by a processor, which reads each program from memory 41 and executes each read program to realize the function corresponding to each program. In other words, the processing circuit 44 in the state in which each program has been read has the functions shown in the processing circuit 44 of Figure 1.

[0039] In Figure 1, the system control function 441, preprocessing function 442, reconstruction function 443, image processing function 444, scan control function 445, display control function 446, and fusion image generation function 447 are shown to be implemented by a single processing circuit 44. However, the embodiments are not limited to this. For example, the processing circuit 44 may be composed of a combination of multiple independent processors, with each processor executing its own program to implement each processing function. Furthermore, each processing function of the processing circuit 44 may be implemented by appropriately distributing or integrating them across one or more processing circuits.

[0040] The system control function 441 controls various functions of the processing circuit 44 based on input operations received from the operator via the input interface 43.

[0041] The preprocessing function 442 generates projection data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the detection data output from DAS18.

[0042] The reconstruction processing function 443 generates CT image data by performing reconstruction processing on the projection data generated by the preprocessing function 442, using methods such as filtered back projection and iterative reconstruction. The reconstruction processing function 443 stores the reconstructed CT image data in the memory 41. The CT image data generated by the reconstruction processing function 443 includes CT image data derived from fluorescent X-rays detected by the fluorescent X-ray detector 19 and CT image data derived from X-rays (transmitted X-rays) detected by the X-ray detector 12. When generating CT image data derived from fluorescent X-rays detected by the fluorescent X-ray detector 19, the reconstruction processing function 443 uses information regarding the incident direction of fluorescent X-rays identified by the identification unit 19a.

[0043] Here, the projection data generated from the counting results obtained by photon counting CT contains information about the energy of the X-rays attenuated by passing through the subject P. Therefore, the reconstruction processing function 443 can, for example, reconstruct CT image data of a specific energy component. Furthermore, the reconstruction processing function 443 can, for example, reconstruct CT image data for each of multiple energy components.

[0044] Furthermore, the reconstruction processing function 443 can, for example, assign a color tone corresponding to the energy component to each pixel of CT image data for each energy component, and generate image data by superimposing multiple CT image data that are color-coded according to the energy component. In addition, the reconstruction processing function 443 can, for example, generate image data that enables the identification of a substance by utilizing the substance's unique K absorption edge. Other image data that the reconstruction processing function 443 can generate include monochromatic X-ray image data, density image data, and effective atomic number image data.

[0045] To reconstruct CT image data, projection data covering a full 360° radius around the subject is required, and even with the half-scan method, projection data covering 180° plus the fan angle is necessary. This embodiment is applicable to either reconstruction method. For the sake of simplicity, the following explanation will use the reconstruction method that uses projection data covering a full 360° radius around the subject (full-scan reconstruction).

[0046] The image processing function 444, based on input operations received from the operator via the input interface 43, converts the CT image data generated by the reconstruction processing function 443 into various image data, such as tomographic images of arbitrary cross-sections or 3D images obtained through rendering, using known methods.

[0047] Furthermore, the image processing function 444 applies predetermined image processing to the CT image data derived from fluorescent X-rays, thereby generating image data (labeled distribution image data) in which each pixel is assigned a color corresponding to the intensity of the fluorescent X-rays. In this way, labeled distribution image data is generated in which each pixel is assigned a color corresponding to the concentration of the contrast agent used as a label.

[0048] Using the method described above, the image processing function 444 generates various types of image data. The image processing function 444 then stores the generated (converted) image data in the memory 41.

[0049] The scan control function 445 controls the CT scan performed by the pallet tower 10. For example, the scan control function 445 controls the collection process of counting results in the pallet tower 10 by controlling the operation of the X-ray high-voltage device 14, the X-ray detector 12, the control device 15, the DAS 18, the X-ray fluorescence detector 19, and the patient table drive device 32. To give one example, the scan control function 445 controls the collection process of projection data in the acquisition of positioning images (scan images) and in the main acquisition (scan) that acquires images used for diagnosis.

[0050] The display control function 446 controls the display 42 to display various images based on various image data stored in the memory 41.

[0051] The fusion image generation function 447 generates fusion image data using image data (morphological image data) generated from X-ray-derived CT image data detected by the X-ray detector 12, and label distribution image data generated from fluorescent X-ray-derived CT image data. For example, the fusion image generation function 447 acquires morphological image data and label distribution image data from memory 41. Then, the fusion image generation function 447 generates fusion image data by combining the morphological image data and label distribution image data. Finally, the fusion image generation function 447 stores the generated fusion image data in memory 41.

[0052] 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)). The processor performs its function by reading a program stored in a memory circuit and executing the read program. Alternatively, instead of storing the program in a memory circuit, the processor may be configured to directly incorporate the program into its circuitry. In this case, the processor performs its function by reading the program incorporated into the circuitry and executing the read program. 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 its function may be achieved in this way.

[0053] Next, an example of the operation of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to Figures 3 and 4. Figure 3 is a diagram illustrating an example of the process by which the X-ray CT apparatus 1 according to the first embodiment generates fusion image data. Figure 4 is a flowchart showing an example of the process flow for generating fusion image data according to the first embodiment.

[0054] As shown in Figures 3 and 4, in step S101, the image processing function 444 generates morphological image data 55 from CT image data originating from X-rays 50 detected by the X-ray detector 12. That is, the reconstruction processing function 443 and the image processing function 444 acquire morphological image data 55, which is reconstructed image data reconstructed based on the data detected by the X-ray detector 12. Morphological image data 55 is an example of the first reconstructed image data. The reconstruction processing function 443 and the image processing function 444 are examples of reconstruction units. Note that the X-rays 50 are X-rays generated by the X-ray tube 11 and transmitted through the subject P.

[0055] Next, in step S102, the image processing function 444 generates labeled distribution image data 56 by applying predetermined image processing to the CT image data derived from the fluorescent X-rays 52 generated from the contrast agent 51. That is, the reconstruction processing function 443 and the image processing function 444 acquire labeled distribution image data 56, which is reconstructed image data reconstructed based on the data detected by the fluorescent X-ray detector 19. The labeled distribution image data 56 is an example of the second reconstructed image data.

[0056] Next, in step S103, the fusion image generation function 447 generates fusion image data 57 by combining the morphological image data 55 and the label distribution image data 56. That is, the fusion image generation function 447 generates fusion image data 57 by associating the morphological image data 55 and the label distribution image data 56. Fusion image data 57 is an example of display image data. The fusion image generation function 447 is an example of a generation unit.

[0057] Next, in step S104, the display control function 446 controls the display 42 to display the fusion image based on the fusion image data 57, and terminates the process shown in Figure 4. The fusion image is an image (composite image) obtained by combining a morphological image based on morphological image data 55 and a label distribution image based on label distribution image data 56.

[0058] The X-ray CT apparatus 1 according to the first embodiment has been described above. The X-ray CT apparatus 1 directly detects (observes) the monochromatic fluorescent X-rays 52 generated from the substances constituting the contrast agent 51. Therefore, the X-ray CT apparatus 1 can detect fluorescent X-rays 52, which are X-rays with high independence in their observed energy spectrum. Furthermore, because the X-ray CT apparatus 1 directly measures the energy of the fluorescent X-rays 52, it is possible to obtain label distribution image data 56 with excellent independence, from which background elements such as water and bone of the subject P have been removed.

[0059] Furthermore, with the X-ray CT scanner 1, the accuracy of identifying labeled substances can be improved by combining a morphological image based on the transmission spectrum with a labeled distribution image, which is a fluorescent X-ray image.

[0060] Furthermore, with the X-ray CT scanner 1, by utilizing fluorescent X-rays 52, the contrast agent, which acts as a label, can be quantitatively visualized in the label distribution image.

[0061] Furthermore, because background elements such as water and bone in subject P are removed, the contrast of the labeled distribution image data 56 can be improved. For example, the CNR (Contrast-to-noise ratio) of the labeled distribution image data 56 is higher than that of image data generated by conventional cone-beam CT.

[0062] (Second embodiment) In the first embodiment, a case was described in which the X-ray CT apparatus 1 is equipped with one X-ray fluorescence detector 19. However, the X-ray CT apparatus 1 may be equipped with multiple X-ray fluorescence detectors 19. Therefore, such an embodiment will be described as the second embodiment. In the description of the second embodiment, the differences from the first embodiment will be mainly described, and descriptions of configurations similar to those of the first embodiment may be omitted.

[0063] Figure 5 is a diagram illustrating the plurality of X-ray fluorescence detectors 19 provided in the X-ray CT apparatus 1 according to the second embodiment. As shown in Figure 5, the X-ray CT apparatus 1 according to the second embodiment includes, for example, eight X-ray fluorescence detectors 19. In the following description of the second embodiment, the case in which the X-ray CT apparatus 1 has eight X-ray fluorescence detectors 19 will be described, but the X-ray CT apparatus 1 may also include multiple X-ray fluorescence detectors 19 other than eight. The eight X-ray fluorescence detectors 19 are arranged outside the X-ray tube 11 and the X-ray detector 12. The eight X-ray fluorescence detectors 19 are also arranged concentrically around the rotation axis of the rotating frame 13. In the following description, when each of the eight X-ray fluorescence detectors 19 is described separately, they will be referred to as X-ray fluorescence detectors 19a to 19h.

[0064] In the second embodiment, the scan control function 445 determines which X-ray fluorescence detector 19 to detect X-ray fluorescence 52 from among the eight X-ray fluorescence detectors 19a to 19h, according to the rotation position of the X-ray tube 11. That is, the scan control function 445 successively switches the X-ray fluorescence detector 19 to detect X-ray fluorescence 52 from among the eight X-ray fluorescence detectors 19a to 19h, according to the rotation position of the X-ray tube 11. For example, if the rotation position of the X-ray tube 11 is the rotation position shown in Figure 5, the scan control function 445 determines the four X-ray fluorescence detectors 19c, 19d, 19f, and 19g, which are located closer to the X-ray detector 12 than the X-ray tube 11, as the X-ray fluorescence detectors 19 to detect X-ray fluorescence 52. Specifically, for example, the scan control function 445 controls the signals output from the four X-ray fluorescence detectors 19c, 19d, 19f, and 19g, which have been determined as X-ray fluorescence detectors 19 for detecting X-ray fluorescence 52, so that they are used when generating the label distribution image data 56. The scan control function 445 is an example of a switching unit.

[0065] Furthermore, for example, if the rotation position of the X-ray tube 11 is the rotation position shown in Figure 5, the scan control function 445 controls the X-ray fluorescence detector 19e, which is located on the opposite side of the X-ray tube 11 from the X-ray detector 12, to not be used as the X-ray fluorescence detector 19 for detecting X-ray fluorescence 52. Specifically, for example, the scan control function 445 controls the system so that the signal output from the X-ray fluorescence detector 19e is not used when generating various image data. Depending on the rotation position of the X-ray tube 11, the scan control function 445 controls the X-ray fluorescence detector 19, which is located on the opposite side of the X-ray tube 11 from the X-ray detector 12, to not be used as the X-ray fluorescence detector 19 for detecting X-ray fluorescence 52. In other words, the scan control function 445 successively switches between the eight X-ray fluorescence detectors 19a to 19h that are not used as the X-ray fluorescence detector 19 for detecting X-ray fluorescence 52, according to the rotational position of the X-ray tube 11.

[0066] The scan control function 445 determines which X-ray fluorescence detector 19 to detect backscattered X-rays from among the eight X-ray fluorescence detectors 19a to 19h, according to the rotation position of the X-ray tube 11. In other words, the scan control function 445 successively switches between the X-ray fluorescence detectors 19a to 19h that detect backscattered X-rays, according to the rotation position of the X-ray tube 11. For example, if the rotation position of the X-ray tube 11 is as shown in Figure 5, the scan control function 445 determines the three X-ray fluorescence detectors 19a, 19b, and 19h located on the X-ray tube 11 side as the X-ray fluorescence detectors 19 that detect backscattered X-rays. Specifically, for example, the scan control function 445 controls the signals output from the three X-ray fluorescence detectors 19a, 19b, and 19h, which have been determined as the X-ray fluorescence detectors 19 that detect backscattered X-rays, so that they are used when generating scattered image data.

[0067] In the second embodiment, the reconstruction processing function 443 generates CT image data derived from backscattered X-rays detected by the fluorescent X-ray detector 19, and the image processing function 444 generates scattering image data showing a scattering image from the CT image data derived from backscattered X-rays. The display control function 446 displays the scattering image based on the scattering image data on the display 42. In the scattering image, information about the surface of the subject P is visualized. Therefore, in the second embodiment, new image information can be obtained, such as the identification of the surface state of the subject P by measuring backscattered X-rays.

[0068] The X-ray CT apparatus 1 according to the second embodiment has been described above. The X-ray CT apparatus 1 according to the second embodiment provides the same effects as the X-ray CT apparatus 1 according to the first embodiment.

[0069] (Third embodiment) The X-ray CT apparatus 1 may include a single ring-shaped X-ray fluorescence detector. Therefore, such an embodiment will be described as the third embodiment. In the description of the third embodiment, the differences from the first and second embodiments will be mainly described, and descriptions of configurations similar to those in the first and second embodiments may be omitted.

[0070] The X-ray CT apparatus 1 according to the third embodiment includes a ring-shaped X-ray fluorescence detector. This ring-shaped X-ray fluorescence detector is positioned outside the X-ray tube 11 and the X-ray detector 12. Furthermore, the ring-shaped X-ray fluorescence detector is formed concentrically around the rotation axis of the rotating frame 13. In other words, in the third embodiment, the X-ray fluorescence detector is arranged in a ring shape around the rotation axis of the rotating frame 13. The X-ray fluorescence detector according to the third embodiment is an example of the second X-ray detector.

[0071] In the third embodiment, the X-ray fluorescence detector comprises a plurality of detection elements. The scan control function 445 according to the third embodiment performs the same control on the plurality of detection elements as the control performed on the plurality of X-ray fluorescence detectors 19 in the second embodiment.

[0072] In the third embodiment, the scan control function 445 determines a detection element for detecting fluorescent X-rays 52 from among a plurality of detection elements included in the ring-shaped fluorescent X-ray detector, according to the rotational position of the X-ray tube 11. That is, the scan control function 445 successively switches the detection element for detecting fluorescent X-rays 52 from among the plurality of detection elements, according to the rotational position of the X-ray tube 11. For example, the scan control function 445 determines a detection element located closer to the X-ray detector 12 than the X-ray tube 11 as the detection element for detecting fluorescent X-rays 52. Specifically, for example, the scan control function 445 controls the signal output from the detection element determined to detect fluorescent X-rays 52 so that it is used when generating the label distribution image data 56.

[0073] Furthermore, the scan control function 445 controls the detection elements so that the detection elements located on the opposite side of the X-ray tube 11 from the X-ray detector 12 are not used as detection elements for detecting fluorescent X-rays 52. Specifically, for example, the scan control function 445 controls the system so that signals output from detection elements located on the opposite side of the X-ray tube 11 from the X-ray detector 12 are not used when generating various image data. Depending on the rotation position of the X-ray tube 11, the scan control function 445 controls the detection elements so that the detection elements located on the opposite side of the X-ray tube 11 from the X-ray detector 12 are not used as detection elements for detecting fluorescent X-rays 52. In other words, depending on the rotation position of the X-ray tube 11, the scan control function 445 successively switches between detection elements that are not used as detection elements for detecting fluorescent X-rays 52 from among the multiple detection elements.

[0074] The scan control function 445 determines which detection element to use to detect backscattered X-rays from among multiple detection elements, according to the rotational position of the X-ray tube 11. In other words, the scan control function 445 successively switches between the detection elements that detect backscattered X-rays from among multiple detection elements, according to the rotational position of the X-ray tube 11. For example, the scan control function 445 determines the detection element located on the X-ray tube 11 side as the detection element to detect backscattered X-rays. Specifically, for example, the scan control function 445 controls the system so that the signal output from the detection element determined to detect backscattered X-rays is used when generating scattered image data.

[0075] The X-ray CT apparatus 1 according to the third embodiment has been described above. The X-ray CT apparatus 1 according to the third embodiment provides the same effects as the X-ray CT apparatus 1 according to the first embodiment and the X-ray CT apparatus 1 according to the second embodiment.

[0076] (Fourth embodiment) In the first to third embodiments, the case in which the X-ray fluorescence detector is located outside the X-ray detector 12 was described. However, the X-ray fluorescence detector may also be located inside the X-ray detector 12. Therefore, such an embodiment will be described as the fourth embodiment. In the description of the fourth embodiment, the differences from the first to third embodiments will be mainly described, and descriptions of configurations similar to those in the first to third embodiments may be omitted.

[0077] Figure 6 is a diagram illustrating the multiple X-ray fluorescence detectors 19 provided in the X-ray CT apparatus 1 according to the fourth embodiment. Figure 7 is a diagram illustrating the positional relationship between the multiple X-ray fluorescence detectors 19 and the X-ray tube 11, and the positional relationship between the multiple X-ray fluorescence detectors 19 and the X-ray detector 12 according to the fourth embodiment.

[0078] The X-ray CT apparatus 1 according to the fourth embodiment includes, for example, eight X-ray fluorescence detectors 19, as shown in Figure 6. In the following description of the fourth embodiment, the case in which the X-ray CT apparatus 1 has eight X-ray fluorescence detectors 19 will be described, but the X-ray CT apparatus 1 may have more than eight X-ray fluorescence detectors 19. The eight X-ray fluorescence detectors 19 are arranged inside the X-ray tube 11 and the X-ray detector 12. The eight X-ray fluorescence detectors 19 are also arranged concentrically around the rotation axis of the rotating frame 13.

[0079] If X-rays generated from the X-ray tube 11 enter the X-ray fluorescence detector 19, the X-ray fluorescence detector 19 will detect not only the X-ray fluorescence but also the X-rays generated from the X-ray tube 11. In this case, the independence of the observed energy spectrum will be reduced.

[0080] Therefore, as shown in Figure 7, the fluorescent X-ray detector 19 is positioned offset from the X-ray tube 11 and the X-ray detector 12 in the direction of the rotation axis 60 of the rotating frame 13. This makes it possible to suppress the optical X-ray detector 19 from detecting X-rays generated from the X-ray tube 11.

[0081] The X-ray CT apparatus 1 according to the fourth embodiment has been described above. The X-ray CT apparatus 1 according to the fourth embodiment provides the same effects as the X-ray CT apparatus 1 according to the first to third embodiments.

[0082] In the first to fourth embodiments, the case in which the X-ray fluorescence detector is fixed and does not rotate was described. However, a rotating body may rotatably support the X-ray fluorescence detector. This rotating body is a mechanism separate from the rotating frame 13. For example, three X-ray fluorescence detectors may be mounted on the rotating body, 120 degrees apart from each other, with the rotating axis of the rotating body as the center. Each of these three X-ray fluorescence detectors may then rotate by 120 degrees.

[0083] (Other embodiments) In addition to the embodiments described above, the device may be implemented in various other forms.

[0084] For example, each component of the illustrated device is a functional concept and does not necessarily have to be physically configured as shown. In other words, the specific forms of distribution and integration of each device are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads and usage conditions. Furthermore, each processing function performed by each device can be implemented, all or any part of it, by a CPU and the program that is analyzed and executed by that CPU, or by hardware using wired logic.

[0085] Furthermore, among the processes described in the embodiments, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically by known methods. In addition, the processing procedures, control procedures, specific names, and information including various data and parameters shown in the above document and drawings can be arbitrarily changed unless otherwise specified.

[0086] Furthermore, the method described in the embodiment can be implemented by executing a pre-prepared program on a computer such as a personal computer or workstation. This program can be distributed via a network such as the Internet. In addition, this control program can be recorded on a computer-readable non-transient recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and executed by reading it from the recording medium by a computer.

[0087] According to at least one embodiment described above, it is possible to detect X-rays with high independence of the observed energy spectrum.

[0088] 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 are possible 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.

[0089] With respect to the above embodiments, the following additional notes are disclosed as aspects of the invention and selective features. (Note 1) An X-ray tube that generates X-rays, A first X-ray detector is positioned opposite the X-ray tube and detects the X-rays that have passed through the subject, A rotating part that rotatably supports the X-ray tube and the first X-ray detector, A second X-ray detector for detecting characteristic X-rays generated in response to the substance within the subject, An X-ray CT scanner equipped with [specific features / features]. (Note 2) The second X-ray detector may be arranged in a ring shape around the rotation axis of the rotating part. (Note 3) Multiple second X-ray detectors may be arranged around the rotation axis of the rotating unit. (Note 4) The second X-ray detector may have an identification unit for identifying the incident direction of the detected characteristic X-rays. (Note 5) The identification unit may be a collimator. (Note 6) The identification unit may include a scattering body, and the incident angle of the characteristic X-rays may be identified based on the scattering angle of the characteristic X-rays at the scattering body. (Note 7) The aforementioned X-ray CT apparatus is A reconstruction unit that acquires a first reconstructed image data reconstructed based on data detected by the first X-ray detector and a second reconstructed image data reconstructed based on data detected by the second X-ray detector, The system may further include a generation unit that generates display image data by associating the first reconstructed image data with the second reconstructed image data. (Note 8) The aforementioned X-ray CT apparatus is The system may further include a switching unit that switches the detection element for detecting the characteristic X-rays from among a plurality of detection elements included in the second X-ray detector, depending on the rotational position of the X-ray tube. (Note 9) The aforementioned X-ray CT apparatus is The system may further include a switching unit that switches the second X-ray detector that detects the characteristic X-rays from among the plurality of second X-ray detectors according to the rotational position of the X-ray tube. (Note 10) The switching unit may further switch the detection element that detects backscattered X-rays from among the plurality of detection elements according to the rotational position of the X-ray tube. (Note 11) The switching unit may further switch the X-ray detector that detects backscattered X-rays from among the plurality of X-ray detectors according to the rotational position of the X-ray tube. (Note 12) The switching unit may control the detection element among the plurality of X-ray detection elements that is located on the opposite side of the X-ray tube from the first X-ray detector so as not to be used as the detection element for detecting the characteristic X-rays. (Note 13) The switching unit may control the X-ray detector located on the opposite side of the X-ray tube from the first X-ray detector among the plurality of X-ray detectors so as not to be used as the X-ray detector for detecting characteristic X-rays. (Note 14) The second X-ray detector may be located inside the first X-ray detector and positioned offset from the first X-ray detector in the direction of the rotation axis of the rotating part. (Note 15) An X-ray tube that generates X-rays, A first X-ray detector is positioned opposite the X-ray tube and detects the X-rays that have passed through the subject, A rotating part that rotatably supports the X-ray tube and the first X-ray detector, A plurality of second X-ray detectors for detecting characteristic X-rays generated in accordance with the substance in the subject, A switching unit that switches between the X-ray detectors that detect backscattered X-rays from among the plurality of X-ray detectors according to the rotational position of the X-ray tube, An X-ray CT scanner equipped with [specific features / features]. [Explanation of symbols]

[0090] 1 X-ray CT device 12 X-ray detectors 13 rotation frames 19. X-ray fluorescence detector

Claims

1. An X-ray tube that generates X-rays, A first X-ray detector is positioned opposite the X-ray tube and detects the X-rays that have passed through the subject, A rotating part that rotatably supports the X-ray tube and the first X-ray detector, A second X-ray detector for detecting characteristic X-rays generated in response to the substance within the subject, Equipped with, The second X-ray detector is provided at a position closer to the rotation axis of the rotating part or further away from the rotation axis than the first X-ray detector. X-ray CT device.

2. The X-ray CT apparatus according to claim 1, wherein the second X-ray detector is arranged in a ring shape with respect to the rotation axis of the rotating part.

3. The X-ray CT apparatus according to claim 1, wherein the second X-ray detectors are arranged in a plurality around the rotation axis of the rotating part.

4. The X-ray CT apparatus according to claim 1, wherein the second X-ray detector has an identification unit for identifying the incident direction of the detected characteristic X-rays.

5. The X-ray CT apparatus according to claim 4, wherein the identification unit is a collimator.

6. The X-ray CT apparatus according to claim 4, wherein the identification unit comprises a scattering body and identifies the incident angle of the characteristic X-rays based on the scattering angle of the characteristic X-rays at the scattering body.

7. A reconstruction unit that acquires a first reconstructed image data reconstructed based on data detected by the first X-ray detector and a second reconstructed image data reconstructed based on data detected by the second X-ray detector, The system further comprises a generation unit that generates display image data by associating the first reconstructed image data with the second reconstructed image data. The X-ray CT apparatus according to claim 1.

8. The X-ray CT apparatus according to claim 2, further comprising a switching unit that switches a detection element for detecting characteristic X-rays from among a plurality of detection elements included in the second X-ray detector according to the rotational position of the X-ray tube.

9. The X-ray CT apparatus according to claim 3, further comprising a switching unit that switches a second X-ray detector for detecting characteristic X-rays from among the plurality of second X-ray detectors according to the rotational position of the X-ray tube.

10. The X-ray CT apparatus according to claim 8, wherein the switching unit further switches the detection element for detecting backscattered X-rays from among the plurality of detection elements according to the rotation position of the X-ray tube.

11. The X-ray CT apparatus according to claim 9, wherein the switching unit further switches a second X-ray detector for detecting backscattered X-rays from among the plurality of second X-ray detectors according to the rotational position of the X-ray tube.

12. The X-ray CT apparatus according to claim 8, wherein the switching unit controls the detection element located on the opposite side of the X-ray tube from the first X-ray detector among the plurality of detection elements so as not to be used as a detection element for detecting characteristic X-rays.

13. The X-ray CT apparatus according to claim 9, wherein the switching unit controls the second X-ray detector, among the plurality of second X-ray detectors, that is located on the opposite side of the X-ray tube from the first X-ray detector, so as not to be used as an X-ray detector for detecting characteristic X-rays.

14. The X-ray CT apparatus according to claim 1, wherein the second X-ray detector is provided at a position closer to the rotation axis of the rotating part than the first X-ray detector, and is provided at a position offset in the direction of the rotation axis of the rotating part with respect to the first X-ray detector.

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