JP2020195585A - Radiation diagnostic apparatus - Google Patents

Abstract

To appropriately reduce an influence of an afterglow.SOLUTION: A radiation diagnostic apparatus comprises a radiation detector, a reception unit, and a processing unit. The radiation detector includes a scintillator which emits light in response to incident radiation, and an optical sensor which detects the light emitted from the scintillator and outputs a signal according to the light. The reception unit receives an input of scanning conditions. The processing unit reduces an influence of an afterglow on the output from the radiation detector, on the basis of the scanning conditions.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a radiological diagnostic apparatus.

In radiodiagnosis devices such as X-ray CT (Computed Tomography) devices, PET (Positron Emission Tomography) devices, and SPECT (Single Photon Emission Computed Tomography) devices, radiation such as X-rays and gamma rays is converted into visible light by a scintillator. Then, visible light is converted into an analog-type electric signal by an optical sensor such as a photodiode. Then, the analog format electric signal is converted into the digital format electric signal (digital data) by DAS (Data Acquisition System) or the like.

The scintillator has a characteristic of delayed fluorescence (afterglow) in which the emitted light is gradually attenuated over time with respect to the input of X-rays. Afterglow causes light to be emitted from the scintillator over a plurality of subsequent views, for example, in imaging with an X-ray CT apparatus. For this reason, the time resolution of the radiographic image obtained by the radiological diagnostic apparatus deteriorates, artifacts occur in the radiological image, and the radiological image is blurred. For example, in dual energy scans in which the energy of X-rays changes from moment to moment, and in high-speed scans in which the X-ray tube and X-ray detector rotate at high speed, the time resolution deteriorates significantly due to afterglow, or afterglow occurs. The resulting artifacts may be noticeable. In addition, even when a high-speed scan is used to shoot a subject with a relatively fast movement such as the heart, the time resolution is significantly deteriorated due to afterglow, and artifacts due to afterglow are remarkably generated. ..

On the other hand, afterglow improves the S / N (signal-to-noise ratio) of the electric signal output from the optical sensor. Then, for example, when shooting an image with a small movement of bones or the like, the operator wants to improve the S / N even if the influence of afterglow is allowed in order to obtain an image with less noise. There is. Further, for example, when shooting a shooting target that is relatively susceptible to noise such as the trunk, the S / N ratio is good even if the influence of afterglow is allowed in order to obtain an image with less noise. There is an operator's request to do so.

Therefore, it is desired to appropriately reduce the influence of afterglow according to the part to be imaged and the scanning conditions.

Japanese Unexamined Patent Publication No. 10-274675 Special Table 2016-591183 Japanese Unexamined Patent Publication No. 11-160440

An object to be solved by the present invention is to provide a radiological diagnostic apparatus capable of appropriately reducing the influence of afterglow.

The radiation diagnostic apparatus of the embodiment includes a radiation detector, a reception unit, and a processing unit. The radiation detector includes a scintillator that emits light in response to incident radiation, and an optical sensor that detects light emitted from the scintillator and outputs a signal corresponding to the light. The reception unit accepts input of scan conditions. The processing unit executes processing for reducing the influence of afterglow on the output from the radiation detector based on the scanning conditions.

FIG. 1 is a diagram showing an example of the configuration of the X-ray CT apparatus according to the first embodiment. FIG. 2 is a diagram showing an example of the configuration of the X-ray detector according to the first embodiment. FIG. 3 is a flowchart showing a flow of an example of the first process executed by the X-ray CT apparatus according to the first embodiment. FIG. 4 is a diagram showing an example of the configuration of the X-ray detector according to the first modification of the first embodiment. FIG. 5A is a diagram showing an example of the sensational volume of the optical sensor according to the second modification of the first embodiment. FIG. 5B is a diagram showing an example of the felt volume of the optical sensor according to the second modification of the first embodiment. FIG. 6 is a diagram for explaining an example of processing executed by the X-ray CT apparatus according to the third modification of the first embodiment. FIG. 7 is a diagram showing an example of the configuration of the X-ray CT apparatus according to the second embodiment. FIG. 8 is a diagram showing an example of the configuration of the X-ray detector according to the second embodiment. FIG. 9 is a flowchart showing a flow of an example of the second process executed by the X-ray CT apparatus according to the second embodiment. FIG. 10 is a diagram showing an example of the configuration of the X-ray CT apparatus according to the third embodiment. FIG. 11 is a diagram showing an example of the configuration of the X-ray detector according to the third embodiment. FIG. 12 is a flowchart showing a flow of an example of a third process executed by the X-ray CT apparatus according to the third embodiment.

Hereinafter, embodiments of the radiation diagnostic apparatus will be described in detail with reference to the drawings. The contents described in one embodiment or modification may be similarly applied to other embodiments or other modifications.

(First Embodiment)
The configuration of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an example of the configuration of the X-ray CT apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT device 1 includes a gantry device 10, a sleeper device 30, and a console device 40. The X-ray CT apparatus 1 is an example of a radiological diagnostic apparatus.

In FIG. 1, the rotation axis of the rotation frame 13 in the non-tilt state or the longitudinal direction of the top plate 33 of the sleeper device 30 is the Z-axis direction. Further, the axial direction orthogonal to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction. Further, the axial direction orthogonal to the Z-axis direction and the X-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. Note that FIG. 1 is a drawing of the gantry device 10 from a plurality of directions for the sake of explanation, and shows a case where the X-ray CT device 1 has one gantry device 10.

The gantry device 10 includes an X-ray tube 11, an X-ray detector 12, a rotating frame 13, an X-ray high voltage device 14, a control device 15, a wedge 16, a collimator 17, and a DAS 18. The gantry device 10 is an example of a collecting unit.

The X-ray tube 11 is a vacuum tube having a cathode (filament) that generates thermoelectrons and an anode (target) that generates X-rays upon collision of thermions. The X-ray tube 11 generates X-rays to irradiate the subject P by irradiating thermions from the cathode toward the anode by applying a high voltage from the X-ray high voltage device 14. For example, the X-ray tube 11 includes a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermoelectrons. The X-ray tube 11 is an example of an X-ray generating unit.

The X-ray detector 12 detects X-rays irradiated from the X-ray tube 11 and passed through the subject P, and outputs a signal corresponding to the detected X-ray dose to the DAS 18. The X-ray detector 12 has, for example, a plurality of detection element sequences in which a plurality of detection elements are arranged in the channel direction along one arc centered on the focal point of the X-ray tube 11. The X-ray detector 12 has, for example, a structure in which a plurality of detection element sequences in which a plurality of detection elements are arranged in the channel direction are arranged in a row direction (slice direction, row direction). X-rays are an example of radiation.

FIG. 2 is a diagram showing an example of the configuration of the X-ray detector 12 according to the first embodiment. As shown in FIG. 2, the X-ray detector 12 is, for example, an indirect conversion type detector having a scintillator array 12a, an optical sensor array 12b, and a grid (not shown).

The scintillator array 12a has a plurality of scintillators 12a_1. The scintillator 12a_1 has a scintillator crystal that outputs a photon amount of light (scintillation light) according to the incident X dose. That is, the scintillator 12a_1 emits light in response to the incident X-rays. The grid is arranged on the surface of the scintillator array 12a on the X-ray incident side, and has an X-ray shielding plate that absorbs scattered X-rays. The grid may also be called a collimator (one-dimensional collimator or two-dimensional collimator).

As shown in FIG. 2, the scintillator 12a_1 emits short-wavelength light 90 and long-wavelength light 91 in response to incident X-rays. The light 90 is immediately emitted from the scintillator 12a_1 with respect to the incident X-ray, and then immediately attenuated (immediate fluorescence). On the other hand, the light 91 is an afterglow, and after being emitted from the scintillator 12a_1 with respect to the incident X-rays, it is slowly attenuated over time. Here, the afterglow wavelength (peak wavelength) is generally longer than that of immediate fluorescence. In the present embodiment, the wavelength of the light 91 (peak wavelength) is longer than the wavelength of the light 90 (peak wavelength).

The optical sensor array 12b has a plurality of optical sensors 12b_1 and a plurality of optical sensors 12b_2. The optical sensors 12b_1 and 12b_2 according to the first embodiment are realized by, for example, a photodiode or the like. The X-ray detector 12 is configured such that one optical sensor 12b_1 and one optical sensor 12b_2 are associated with a single (one) scintillator 12a_1. As shown in FIG. 2, the scintillator 12a_1, the optical sensor 12b_1, and the optical sensor 12b_2 are arranged in this order along the depth direction indicated by the arrow 92. The optical sensor 12b_1 is an example of the first optical sensor. The optical sensor 12b_2 is an example of a second optical sensor.

The optical sensors 12b_1 and 12b_2 have a function of converting the light from the scintillator 12a_1 associated with the optical sensors 12b_1 and 12b_2 into an electric signal according to the amount of light. That is, the optical sensors 12b_1 and 12b_2 detect the light emitted from the single scintillator 12a_1 and output an electric signal corresponding to the detected light. The X-ray detector 12 is an example of a radiation detector. The electric signal is an example of a signal.

Here, the optical sensor 12b_1 has a wavelength sensitivity characteristic capable of detecting light 90. Further, the optical sensor 12b_2 has a wavelength sensitivity characteristic capable of detecting light 91. That is, the wavelength (peak wavelength) of the light 90 is included in the wavelength band of the light that can be detected by the optical sensor 12b_1. Further, the wavelength (peak wavelength) of the light 91 is included in the wavelength band of the light that can be detected by the optical sensor 12b_2. In the present embodiment, since the type of the material constituting the optical sensor 12b_1 and the type of the material constituting the optical sensor 12b_2 are different, the wavelength sensitivity characteristic of the optical sensor 12b_1 and the wavelength sensitivity characteristic of the optical sensor 12b_2 are different. different.

Therefore, the optical sensor 12b_1 detects the light 90 and outputs an electric signal corresponding to the light 90. Further, the optical sensor 12b_2 detects the light 91 and outputs an electric signal corresponding to the light 91. In the following description, the electric signal corresponding to the light 90 may be referred to as a first electric signal, and the electric signal corresponding to the light 91 may be referred to as a second electric signal.

Returning to the description of FIG. 1, the rotating frame 13 is an annular frame in which the X-ray tube 11 and the X-ray detector 12 are opposed to each other and the X-ray tube 11 and the X-ray detector 12 are rotated by the control device 15. Is. 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 further support the X-ray high voltage device 14, the wedge 16, the collimator 17, the DAS 18, and the like. Further, the rotating frame 13 can further support various configurations (not shown in FIG. 1). In the following, in the gantry device 10, the rotating frame 13 and the portion that rotates and moves together with the rotating frame 13 are also referred to as a rotating portion.

The X-ray high-voltage device 14 has an electric circuit such as a transformer and a rectifier, and has a high-voltage generator that generates a high voltage applied to the X-ray tube 11 and an X-ray that is generated by the X-ray tube 11. It has an X-ray control device that controls the output voltage according to the above. The high voltage generator may be a transformer type or an inverter type. The X-ray high voltage device 14 may be provided on the rotating frame 13 or on a fixed frame (not shown).

The control device 15 includes a processing circuit having a CPU (Central Processing Unit) and 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 operation of the gantry device 10 and the sleeper device 30. For example, the control device 15 controls the rotation of the rotating frame 13, the tilt of the gantry device 10, the operation of the sleeper device 30 and the top plate 33, and the like. As an example, the control device 15 rotates the rotating frame 13 about an axis parallel to the X-axis direction based on the input tilt angle (tilt angle) information as a control for tilting the gantry device 10. The control device 15 may be provided in the gantry device 10 or in the console device 40.

The wedge 16 is a filter for adjusting the X-ray dose emitted from the X-ray tube 11. Specifically, the wedge 16 transmits the X-rays radiated from the X-ray tube 11 so that the distribution of the X-rays radiated from the X-ray tube 11 to the subject P becomes a predetermined distribution. It is a filter that attenuates. For example, the wedge 16 is a wedge filter or a bow-tie filter, which is a filter obtained by processing aluminum or the like so as to have a predetermined target angle and a predetermined thickness.

The collimator 17 is a lead plate or the like for narrowing the irradiation range of X-rays transmitted through the wedge 16, and a slit is formed by a combination of a plurality of lead plates or the like. The collimator 17 may be called an X-ray diaphragm. Further, in FIG. 1, a case where the wedge 16 is arranged between the X-ray tube 11 and the collimator 17 is shown, but there is a case where the collimator 17 is arranged between the X-ray tube 11 and the wedge 16. May be good. In this case, the wedge 16 is irradiated from the X-ray tube 11, and the X-ray whose irradiation range is limited by the collimator 17 is transmitted and attenuated.

The DAS 18 collects X-ray signals detected by each detection element included in the X-ray detector 12. For example, the DAS 18 has an amplifier that amplifies an electric signal output from each detection element and an A / D converter that converts the electric signal into a digital signal, and generates detection data.

In the following description, the detection data generated by the DAS 18 based on the first electric signal (electric signal corresponding to the light 90) may be referred to as the first detection data. Further, the detection data generated by the DAS 18 based on the second electric signal (electric signal corresponding to the light 91) may be referred to as the second detection data.

The data generated by the DAS 18 is transmitted from a transmitter having a light emitting diode (LED) provided on the rotating frame 13 by optical communication to a non-rotating portion (for example, a fixed frame or the like. FIG. 1) of the gantry device 10. The light is transmitted to a receiver having a photodiode provided in (not shown in the above) and transferred to the console device 40. Here, the non-rotating portion is, for example, a fixed frame that rotatably supports the rotating frame 13. The method of transmitting data from the rotating frame 13 to the non-rotating portion of the gantry device 10 is not limited to optical communication, and any non-contact data transmission method may be adopted, and the contact-type data transmission method may be used. You may adopt it.

The sleeper device 30 is a device for placing and moving the subject P to be scanned, and has a base 31, a sleeper 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 as to be movable in the vertical direction. The sleeper drive device 32 is a drive mechanism that moves the top plate 33 on which the subject P is placed in the longitudinal direction of the top plate 33, and includes a motor, an actuator, and the like. 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 the top plate 33, the sleeper drive device 32 may move the support frame 34 in the longitudinal direction of the top plate 33.

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 will be described as a separate body from the gantry device 10, the gantry device 10 may include a part of each component of the console device 40 or the console device 40.

The memory 41 is realized by, for example, a RAM (Random Access Memory), a semiconductor memory element such as a flash memory, a hard disk, an optical disk, or the like. The memory 41 stores, for example, projection data and reconstructed image data. Further, for example, the memory 41 stores a program for the circuit included in the X-ray CT apparatus 1 to realize its function. The memory 41 may be realized by a server group (cloud) connected to the X-ray CT apparatus 1 via a network. The memory 41 is an example of a storage unit.

The display 42 displays various information. For example, the display 42 displays an image indicated by image data generated by the processing circuit 44, or displays a GUI (Graphical User Interface) for receiving various operations from an operator such as a doctor or a radiological technologist. Or something. For example, the display 42 is a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 42 may be a desktop type, or may be composed of a tablet terminal or the like capable of wireless communication with the console device 40 main body.

The input interface 43 receives various input operations from the operator, converts the received input operations into electric signals, and outputs the received input operations to the processing circuit 44. For example, the input interface 43 receives scan conditions from the operator. For example, the scan conditions include a tube voltage value and a tube current value in the main scan, a set value related to the rotation speed of the rotating portion, a FOV (Field Of View), a imaging slice thickness, an imaging range, an imaging target portion, and the like.

For example, the input interface 43 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad for performing input operations by touching an operation surface, a touch screen in which a display screen and a touch pad are integrated, and an optical sensor. It is realized by the non-contact input circuit, voice input circuit, etc. used. The input interface 43 may be provided in the gantry device 10. Further, the input interface 43 may be composed of a tablet terminal or the like capable of wireless communication with the console device 40 main body. Further, the input interface 43 is not limited to one provided with physical operating parts such as a mouse and a keyboard. For example, an electric signal processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the console device 40 and outputs the electric signal to the processing circuit 44 is also an example of the input interface 43. included. The input interface 43 is an example of the reception unit.

The processing circuit 44 controls the operation of the entire X-ray CT apparatus 1. The processing circuit 44 is not limited to the case where it is included in the console device 40. For example, the processing circuit 44 may be included in an integrated server that collectively performs processing on detection data acquired by a plurality of X-ray CT devices. For example, an integrated server connected to the X-ray CT apparatus 1 via a network may have a processing circuit 44. In this case, the X-ray CT apparatus 1 transmits the collected detection data to the integrated server. Then, the integrated server receives the detection data. Then, the processing circuit 44 of the integrated server executes various processes described below with respect to the received detection data.

For example, the processing circuit 44 executes the system control function 441, the preprocessing function 442, the processing execution function 443, the reconstruction processing function 444, the image processing function 445, and the output function 446. For example, the processing circuit 44 reads a program (control program) corresponding to the system control function 441 from the memory 41 and executes it, and based on the input operation received from the operator via the input interface 43, the processing circuit 44 Control various functions of.

The system control function 441 controls the X-ray CT apparatus 1 to perform positioning imaging. For example, the system control function 441 fixes the position of the X-ray tube 11 at a predetermined rotation angle, and irradiates the subject P with X-rays from the X-ray tube 11 while moving the top plate 33 in the Z direction. , Perform positioning shooting. Further, the processing circuit 44 reads a program corresponding to the reconstruction processing function 444 from the memory 41 and executes it to generate positioning image data based on the X-ray signal collected by the positioning imaging. The positioning image data may be referred to as a scanno image data or a scout image data.

Then, the system control function 441 causes the display 42 to display the positioning image indicated by the positioning image data. Then, the system control function 441 acquires the scan conditions input via the input interface 43 from the operator who confirmed the positioning image. Then, the system control function 441 stores the acquired scan conditions in the memory 41. The system control function 441 may automatically set the scan conditions for this scan based on the positioning image data.

Then, the system control function 441 controls the X-ray CT apparatus 1 based on the scan conditions, and executes the main scan for collecting projection data, which will be described below. For example, the system control function 441 moves the subject P into the photographing port of the gantry device 10 by controlling the sleeper drive device 32. Further, the system control function 441 adjusts the opening degree and the position of the collimator 17. Further, the system control function 441 rotates the rotating portion by controlling the control device 15. Further, the system control function 441 controls the X-ray high voltage device 14 to supply a high voltage to the X-ray tube 11. As a result, the X-ray tube 11 generates X-rays to irradiate the subject P.

While the scan is performed by the system control function 441, the DAS 18 collects a plurality of X-ray signals detected by the plurality of detection elements and generates detection data. Further, the processing circuit 44 reads the program corresponding to the preprocessing function 442 from the memory 41 and executes it to perform preprocessing on the detection data output from the DAS 18. For example, the preprocessing function 442 performs preprocessing such as logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, and beam hardening correction on the detection data output from DAS18. The data after the preprocessing is also referred to as raw data. Further, the detection data before the preprocessing and the raw data after the preprocessing are collectively also referred to as projection data.

In the following description, the first detection data preprocessed by the preprocessing function 442 may be referred to as first raw data. Further, the second detection data preprocessed by the preprocessing function 442 may be referred to as second raw data.

Further, the processing circuit 44 reads a program corresponding to the processing execution function 443 from the memory 41 and executes it, so that the output from the X-ray detector 12, that is, the preprocessed raw data is performed based on the scan conditions. A process (first process) for reducing the influence of afterglow on the data is executed. The processing execution function 443 is an example of a processing unit. Details of the process execution function 443 will be described later.

Further, the processing circuit 44 reconstructs the CT image data based on the raw data after the first processing by reading the program corresponding to the reconstruction processing function 444 from the memory 41 and executing the program. Specifically, the reconstruction processing function 444 reconstructs the CT image data by performing reconstruction processing using a filter correction back projection method, a successive approximation reconstruction method, or the like on the raw data after the first processing. To do. The reconstruction processing function 444 is an example of the reconstruction processing unit. The CT image data is an example of radiographic image data. The CT image is an example of a radiographic image.

Further, the processing circuit 44 performs various image processing on the CT image data by reading a program corresponding to the image processing function 445 from the memory 41 and executing the program. For example, the image processing function 445 uses a known method to convert CT image data reconstructed based on an input operation received from an operator via the input interface 43 into tomographic image data or three-dimensional image data of an arbitrary cross section. Convert to. Further, the image processing function 445 stores the converted tomographic image data and the three-dimensional image data in the memory 41.

Further, the processing circuit 44 outputs tomographic image data, three-dimensional image data, CT image data, and the like by reading a program corresponding to the output function 446 from the memory 41 and executing the program. For example, the output function 446 displays various images such as a tomographic image indicated by the tomographic image data and a CT image indicated by the CT image data on the display 42. The output function 446 is an example of a display control unit. Further, for example, the output function 446 is an external device (for example, a server device for storing image data) in which tomographic image data, three-dimensional image data, and CT image data are connected to the X-ray CT device 1 via a network. Output to.

In the X-ray CT apparatus 1 shown in FIG. 1, each processing function is stored in the memory 41 in the form of a program that can be executed by a computer. The processing circuit 44 is a processor that realizes a function corresponding to each program by reading each program from the memory 41 and executing the program. In other words, the processing circuit 44 in the state where each program is read has a function corresponding to the read program. In FIG. 1, each processing function of the system control function 441, the preprocessing function 442, the processing execution function 443, the reconstruction processing function 444, the image processing function 445, and the output function 446 is realized by a single processing circuit 44. However, the embodiment is not limited to this. For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processor may execute each program to realize each processing function. Further, each processing function of the processing circuit 44 may be appropriately distributed or integrated into a single or a plurality of processing circuits.

The word "processor" used in the above description means, for example, a CPU, a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), or a programmable logic device (for example, a simple programmable logic device (for example, a simple programmable logic device). It means a circuit such as a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), or a Field Programmable Gate Array (FPGA). The processor realizes the function by reading and executing the program stored in the memory 41.

In addition, in FIG. 1, it has been described that a single memory 41 stores a program corresponding to each processing function. However, a plurality of memories 41 may be distributed and arranged, and the processing circuit 44 may be configured to read a corresponding program from the individual memories 41. Further, instead of storing the program in the memory 41, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit.

Further, the processing circuit 44 may realize various functions by using a processor of an external device connected via a network. For example, the processing circuit 44 reads a program corresponding to each function from the memory 41 and executes it, and also calculates an external workstation or a server group (cloud) connected to the X-ray CT apparatus 1 via a network. Each function shown in FIG. 1 may be realized by using the above.

The example of the configuration of the X-ray CT apparatus 1 has been described above. Under such a configuration, the X-ray CT apparatus 1 executes various processes described below so that the influence of afterglow can be appropriately reduced.

FIG. 3 is a flowchart showing a flow of an example of the first process executed by the X-ray CT apparatus 1 according to the first embodiment. As shown in the example of FIG. 3, the process execution function 443 acquires the scan condition from the memory 41 in which the scan condition is stored (step S101).

Then, the process execution function 443 determines from the scan conditions whether to suppress the influence of the afterglow or to improve the S / N while allowing the influence of the afterglow (step S102).

For example, when the imaging target included in the scanning conditions is a region such as the heart where the movement is relatively fast, deterioration of time resolution and occurrence of artifacts due to afterglow may be considered. Further, even when the energy of the irradiated X-ray indicated by the scanning condition changes from moment to moment (for example, in the case of dual energy collection), deterioration of time resolution and occurrence of artifacts due to afterglow are considered.

Therefore, in these cases, that is, when suppressing the influence of afterglow (step S102: suppressing the influence of afterglow), the process execution function 443 proceeds to step S103. In step S103, the processing execution function 443 adds the raw data obtained by weighting the second raw data with a predetermined weighting coefficient α to the first raw data according to the following equation (1). By doing so, the third raw data is generated.

D3 = D1 + (α × D2) (1)

However, "+" is a symbol indicating addition, and "x" is a symbol indicating multiplication. Further, "D1" indicates the first raw data, "D2" indicates the second raw data, and "D3" indicates the third raw data. The coefficient α is a value of 0 or more and less than 1. The closer the value of the coefficient α is to 0, the smaller the influence of afterglow on the CT image data reconstructed from the third raw data. On the other hand, the closer the value of the coefficient α is to 1, the greater the influence of afterglow on the CT image data reconstructed from the third raw data. The value of the coefficient α is set by the operator, for example.

In the formula (1), “α × D2” represents the second raw data weighted by a predetermined coefficient α. The third raw data generated in step S103 is 1-channel data used when the CT image data is reconstructed by the reconstruction processing function 444.

As described above, the processing execution function 443 reduces the contribution of the optical sensor 12b_2 as compared with the optical sensor 12b_1 based on the scanning conditions. Specifically, in the processing execution function 443, the ratio of the second raw data based on the second electric signal output from the optical sensor 12b_2 to the first raw data based on the first electric signal output from the optical sensor 12b_1 is set. Generate the third raw data so that it is relatively low. Then, the processing execution function 443 controls so that the third raw data is used when reconstructing the CT image data. Then, the first process is completed. In this case, the reconstruction processing function 444 reconstructs the CT image data using the third raw data. Therefore, deterioration of the time resolution of the reconstructed CT image data and occurrence of artifacts can be suppressed.

Here, there is a conventional method in which the measured value of afterglow is used as a model and correction is performed by software. In contrast to such a conventional method, the X-ray CT apparatus 1 according to the first embodiment reconstructs CT image data using third raw data in which the influence of afterglow is physically suppressed. Therefore, according to the X-ray CT apparatus 1 according to the first embodiment, the influence of afterglow can be surely reduced as compared with the conventional method. Further, according to the X-ray CT apparatus 1 according to the first embodiment, the influence of afterglow can be reduced with a smaller processing load than the processing load when performing correction by a computer in the conventional method.

On the other hand, when the imaging target included in the scanning conditions is a portion such as a bone where the movement is relatively small, it is conceivable to improve the S / N even if the influence of afterglow is allowed. In addition, even if the imaging target included in the scanning conditions is a part that is relatively susceptible to noise such as the trunk, it is possible to improve the S / N even if the effect of afterglow is allowed. Be done. Therefore, in these cases, that is, when the S / N is to be improved (step S102: improvement of the S / N), the process execution function 443 proceeds to step S104.

In step S104, the processing execution function 443 generates the fourth raw data by adding the second raw data to the first raw data according to the following equation (2).

D4 = D1 + D2 (2)

However, "D4" indicates the fourth raw data.

The fourth raw data is 1-channel data used when the CT image data is reconstructed by the reconstruction processing function 444. Then, the first process is completed. In this case, the reconstruction processing function 444 reconstructs the CT image data using the fourth raw data. Therefore, it is possible to improve the S / N of the reconstructed CT image data.

The X-ray CT apparatus 1 according to the first embodiment has been described above. According to the X-ray CT apparatus 1 according to the first embodiment, the influence of afterglow can be appropriately reduced. Further, according to the X-ray CT apparatus 1 according to the first embodiment, a scintillator with high light emission and low cost, which has been difficult to use due to the strong influence of afterglow, is used as the scintillator 12a_1. can do. Further, according to the X-ray CT apparatus 1 according to the first embodiment, the time resolution and the S / N which are in a trade-off relationship with each other can be appropriately adjusted.

(Modification 1 of the first embodiment)
In the first embodiment, the case where the optical sensor 12b_1 and the optical sensor 12b_2 are arranged side by side in the depth direction indicated by the arrow 92 has been described. However, the arrangement of the optical sensor 12b_1 and the optical sensor 12b_2 is not limited to this. Therefore, another example of the arrangement of the optical sensor 12b_1 and the optical sensor 12b_2 will be described as a modification 1 of the first embodiment.

Hereinafter, in the description of the modified example 1 of the first embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted. FIG. 4 is a diagram showing an example of the configuration of the X-ray detector 12 according to the first modification of the first embodiment.

As shown in FIG. 4, the optical sensor 12b_1 and the optical sensor 12b_2 are arranged so as to line up along one surface of the scintillator 12a_1, not in the depth direction indicated by the arrow 92. Therefore, according to the first modification of the first embodiment, it is possible to suppress an increase in the dimension of the optical sensor array 12b in the depth direction as compared with the first embodiment. That is, according to the first modification, the increase in the size of the optical sensor array 12b can be suppressed.

The modification 1 of the first embodiment has been described above. According to the first modification, even when the optical sensors 12b_1 and 12b_2 are arranged as shown in FIG. 4, the influence of the afterglow is appropriately reduced as in the first embodiment. Can be made to. Further, according to the first modification of the first embodiment, it is possible to suppress an increase in the size of the optical sensor array 12b.

(Modification 2 of the first embodiment)
In the first embodiment, since the type of the material constituting the optical sensor 12b_1 and the type of the material constituting the optical sensor 12b_2 are different, the wavelength sensitivity characteristic of the optical sensor 12b_1 and the wavelength sensitivity characteristic of the optical sensor 12b_2 are different. The case where is different from is explained. However, the type of material constituting the optical sensor 12b_1 and the type of material constituting the optical sensor 12b_2 may be the same. Then, the wavelength sensitivity characteristic of the optical sensor 12b_1 may be different from the wavelength sensitivity characteristic of the optical sensor 12b_2 because the sensation volume of the optical sensor 12b_1 and the sensation volume of the optical sensor 12b_2 are different. Therefore, such a modification will be described as a modification 2 of the first embodiment.

Hereinafter, in the description of the modified example 2 of the first embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted. In the second modification of the first embodiment, the type of the material constituting the optical sensor 12b_1 and the type of the material constituting the optical sensor 12b_2 are the same. However, as will be described later, the sensation volume of the optical sensor 12b_1 and the sensation volume of the optical sensor 12b_2 are different.

FIG. 5A is a diagram showing an example of the sensational volume of the optical sensor 12b_2 according to the second modification of the first embodiment. FIG. 5B is a diagram showing an example of the felt volume of the optical sensor 12b_1 according to the second modification of the first embodiment. Here, the felt volume is schematically represented by a rectangular parallelepiped.

As shown in FIGS. 5A and 5B, the side of the length L1 and the side of the length L2 are common in the sensation volume of the optical sensor 12b_2 and the sensation volume of the optical sensor 12b_1. One surface F of the two surfaces defined by the side of length L1 and the side of length L2 faces one surface of the scintillator 12a_1. The side of the length L3 extending in the depth direction indicated by the arrow 92 shown in FIG. 5A is longer than the side of the length L4 extending in the depth direction shown in FIG. 5B. This is because the longer the wavelength of the scintillation light incident on the optical sensors 12b_1 and 12b_1, the deeper the carrier generation position in the depth direction. Therefore, the sensational volume of the optical sensor 12b_2 is larger than the sensational volume of the optical sensor 12b_1.

With such a configuration, the optical sensor 12b_1 has a wavelength sensitivity characteristic capable of detecting light 90, and the optical sensor 12b_1 has a wavelength sensitivity characteristic capable of detecting light 90 and light 91. Then, in the second modification, the X-ray CT apparatus 1 uses the electric signal output from the optical sensor 12b_1 as the first electric signal and the electric signal output from the optical sensor 12b_1 as the second electric signal in the first embodiment. Perform the same processing as the form.

The modified example 2 of the first embodiment has been described above. According to the second modification of the first embodiment, even if the type of the material constituting the optical sensor 12b_1 and the type of the material constituting the optical sensor 12b_2 are the same, the wavelength sensitivity characteristic of the optical sensor 12b_1 , The wavelength sensitivity characteristic of the optical sensor 12b_2 can be made different. Further, according to the second modification of the first embodiment, the same effect as that of the first embodiment is obtained.

(Modification 3 of the first embodiment)
Next, the X-ray CT apparatus 1 according to the third modification of the first embodiment will be described. In the third modification of the first embodiment, the X-ray CT apparatus 1 estimates the X-ray energy.

Hereinafter, in the description of the modified example 3 of the first embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted. FIG. 6 is a diagram for explaining an example of processing executed by the X-ray CT apparatus 1 according to the third modification of the first embodiment.

As shown in FIG. 6, the processing execution function 443 according to the third modification of the first embodiment includes data (for example, first raw data) 61 based on an electric signal output from the optical sensor 12b_1 and the optical sensor 12b_2. The difference D or the ratio with the data (for example, the second raw data) 62 based on the electric signal output from is calculated. Here, the calculated difference D or ratio corresponds to the position where the light is generated in the depth direction of the scintillator 12a_1. For example, when the scintillation light propagates inside the scintillator 12a_1, the transmittance of the light in the medium of the scintillator 12a_1 differs depending on the wavelength. Therefore, the larger the difference D, the longer the distance that the light travels in the scintillator 12a_1. That is, the larger the difference D, the shallower the light is generated in the scintillator 12a_1. Therefore, the processing execution function 443 can estimate the position where the light is generated in the depth direction of the scintillator 12a_1 from the difference D or the ratio. Then, the processing execution function 443 estimates the energy of the X-rays incident on the optical sensors 12b_1 and 12b_2 based on the estimated position. That is, the processing execution function 443 estimates the energy of the incident X-rays based on the electric signal output from the optical sensor 12b_1 and the electric signal output from the optical sensor 12b_2. For example, the processing execution function 443 estimates the energy of the incident X-ray based on the data based on the electric signal output from the optical sensor 12b_1 and the data based on the electric signal output from the optical sensor 12b_1.

The energy estimated in this way is used, for example, in an application that performs spectral CT.

The X-ray CT apparatus 1 according to the third modification of the first embodiment has been described above. According to the X-ray CT apparatus 1 according to the third modification of the first embodiment, the energy of the incident X-ray can be estimated. Further, according to the X-ray CT apparatus 1 according to the third modification of the first embodiment, the same effect as that of the first embodiment is obtained.

(Modification 4 of the first embodiment)
When suppressing the influence of afterglow, even if the DAS 18 amplifies the first electric signal and adds the second electric signal to the amplified first electric signal to generate a third electric signal. Good. The third electrical signal is a signal that is the source of one channel of raw data used when reconstructing CT image data. Therefore, such a modification will be described as a modification 4 of the first embodiment.

Hereinafter, in the description of the modified example 4 of the first embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted.

In variant 4 of the first embodiment, the DAS 18 has a processing circuit and an amplifier. The processing circuit is a circuit capable of processing digital format data. For example, the processing circuit is realized by a processor. The amplifier performs an amplification process for amplifying the first electric signal.

Then, in the modification 4, the processing execution function 443 acquires the scan condition from the memory 41 in which the scan condition is stored, as in the first embodiment. Then, as in the first embodiment, the process execution function 443 determines whether to suppress the influence of afterglow or to improve the S / N while allowing the influence of afterglow from the scan conditions. judge. Then, the processing execution function 443 transmits the determination result information indicating the determination result to the processing circuit of DAS18. The determination result information is information indicating that the influence of the afterglow is suppressed or the S / N is improved while allowing the influence of the afterglow.

Then, the processing circuit of DAS18 receives the determination result information. Then, the processing circuit of DAS18 amplifies the first electric signal to the amplifier when the determination result information indicates that the influence of afterglow is suppressed. Then, the processing circuit of DAS18 generates a third electric signal by adding the electric signal obtained by weighting the second electric signal by the coefficient α to the amplified first electric signal. The third electric signal is data that is the source of the raw data of one channel used when the CT image data is reconstructed by the reconstruction processing function 444. As described above, the processing circuit of the DAS 18 executes a process of increasing the contribution of the optical sensor 12b_1 as compared with the optical sensor 12b_2 based on the scanning conditions. The DAS 18 according to the modified example 4 is an example of the processing unit.

Then, DAS18 generates detection data from the third electric signal. The preprocessing function 442 performs preprocessing on the detected data. Then, the reconstruction processing function 444 reconstructs the CT image data using the preprocessed detection data (raw data). Therefore, according to the modified example 4, it is possible to suppress the deterioration of the time resolution of the reconstructed CT image data and the occurrence of artifacts.

On the other hand, when the determination result information indicates that the S / N is improved while allowing the influence of the afterglow, the processing circuit of the DAS 18 is obtained by adding the second electric signal to the first electric signal. 4 Generates an electrical signal. The fourth electric signal is data that is the source of the raw data of one channel used when the CT image data is reconstructed by the reconstruction processing function 444.

Then, DAS18 generates detection data from the fourth electric signal. The preprocessing function 442 performs preprocessing on the detected data. Then, the reconstruction processing function 444 reconstructs the CT image data using the preprocessed detection data (raw data). Therefore, it is possible to improve the S / N of the reconstructed CT image data.

The X-ray CT apparatus 1 according to the modified example 4 of the first embodiment has been described above. According to the X-ray CT apparatus 1 according to the fourth modification of the first embodiment, the same effect as that of the first embodiment is obtained.

In the fourth modification, the processing execution function 443 may transmit the scan condition to the processing circuit of the DAS 18. Then, it may be determined from the scan conditions whether the processing circuit of the DAS 18 suppresses the influence of the afterglow or improves the S / N while allowing the influence of the afterglow.

(Modification 5 of the first embodiment)
In addition, when suppressing the influence of afterglow, the X-ray detector 12 sets the photosensor 12b_1 and the photosensor so that the charge integration time in the optical sensor 12b_2 is shorter than the charge integration time in the photosensor 12b_1. 12b_2 may be controlled. Then, the DAS 18 may add the first electric signal obtained under the integration time controlled in this way and the second electric signal. The electric signal obtained by such addition is a signal that is the source of one channel of raw data used when reconstructing CT image data. Therefore, such a modification will be described as a modification 5 of the first embodiment.

Hereinafter, in the description of the modified example 5 of the first embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted.

In the fifth modification of the first embodiment, the X-ray detector 12 includes a processing circuit. In the fifth modification, the X-ray detector 12 and the processing circuit 44 can communicate with each other. Then, in the modification 5, the processing execution function 443 transmits the determination result information to the processing circuit of the X-ray detector 12. The determination result information according to the modification 5 is the same information as the determination result information according to the modification 4.

Then, the processing circuit of the X-ray detector 12 receives the determination result information. When the processing circuit of the X-ray detector 12 indicates that the determination result information suppresses the influence of afterglow, the charge integration time in the photosensor 12b_2 is shorter than the charge integration time in the photosensor 12b_1. The optical sensor 12b_1 and the optical sensor 12b_2 are controlled so as to be. Then, the processing circuit of the DAS 18 adds the first electric signal obtained under the integration time controlled in this way and the second electric signal. The electric signal obtained by such addition is a signal that is the source of the raw data of one channel used when the CT image data is reconstructed by the reconstruction processing function 444. In this case, the DAS 18 generates detection data from the electrical signal obtained by such addition. The preprocessing function 442 performs preprocessing on the detected data. Then, the reconstruction processing function 444 reconstructs the CT image data using the preprocessed detection data (raw data). Therefore, deterioration of the time resolution of the reconstructed CT image data and occurrence of artifacts can be suppressed.

On the other hand, when the processing circuit of the X-ray detector 12 indicates that the determination result information aims to improve the S / N while allowing the influence of afterglow, the charge integration time in the photosensor 12b_1 and the charge in the photosensor 12b_2 The optical sensor 12b_1 and the optical sensor 12b_2 are controlled so that the integration time of the above is the same. Then, the processing circuit of the DAS 18 adds the first electric signal obtained under the integration time controlled in this way and the second electric signal. The electric signal obtained by such addition is a signal that is the source of the raw data of one channel used when the CT image data is reconstructed by the reconstruction processing function 444. In this case, the DAS 18 generates detection data from the electrical signal obtained by the addition. The preprocessing function 442 performs preprocessing on the detected data. Then, the reconstruction processing function 444 reconstructs the CT image data using the preprocessed detection data (raw data). Therefore, it is possible to improve the S / N of the reconstructed CT image data.

The X-ray CT apparatus 1 according to the modified example 5 of the first embodiment has been described above. According to the X-ray CT apparatus 1 according to the fifth modification of the first embodiment, the same effect as that of the first embodiment is obtained.

In the modification 5, the processing execution function 443 may transmit the scan condition to the processing circuit of the X-ray detector 12. Then, it may be determined from the scan conditions whether the processing circuit of the X-ray detector 12 suppresses the influence of afterglow or improves the S / N while allowing the influence of afterglow. ..

In the first embodiment described above, the processing execution function 443 performs the first raw data (pre-processed first detection data) and the second raw data (pre-processed second detection data). The case where various processes are executed has been described. However, the processing circuit of DAS18 has the first detection data (detection data generated based on the first electric signal) and the second detection data (detection generated based on the second electric signal) based on the determination result information. The same processing may be executed for the data). Further, the processing circuit of the DAS 18 may execute the same processing on the first electric signal and the second electric signal. Also in this case, the same effect as that of the first embodiment can be obtained. The processing circuit of the DAS 18 performs the processing as described above, so that the amount of data transmitted from the DAS 18 to the console device 40 can be reduced.

(Second Embodiment)
Next, the X-ray CT apparatus 1 according to the second embodiment will be described. In the second embodiment, a filter is provided between the scintillator and the photosensor, and the filter modulates the wavelength of light incident on the photosensor.

FIG. 7 is a diagram showing an example of the configuration of the X-ray CT apparatus 1 according to the second embodiment. Hereinafter, in the description of the second embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted. For example, the same components as those in the first embodiment may be designated by the same reference numerals and the description thereof may be omitted.

The point that the processing circuit 44 according to the second embodiment shown in FIG. 7 includes a processing execution function 447 instead of the processing execution function 443 according to the first embodiment is a feature of the first embodiment shown in FIG. It is different from the processing circuit 44. Further, as shown in FIG. 7, the second embodiment is different from the first embodiment in that the processing circuit 44 and the X-ray detector 12 can communicate with each other.

FIG. 8 is a diagram showing an example of the configuration of the X-ray detector 12 according to the second embodiment. As shown in FIG. 8, the X-ray detector 12 has an indirect conversion having a scintillator array 12a, an optical sensor array 12b, a plurality of filters 12c, a plurality of voltage application circuits 12d, and a grid (not shown). It is a type detector.

The scintillator array 12a has a plurality of scintillators 12a_1 as in the first embodiment.

The optical sensor array 12b has a plurality of optical sensors 12b_3. The optical sensor 12b_3 according to the second embodiment is realized by, for example, a photodiode or the like. The X-ray detector 12 is configured by associating a single (one) scintillator 12a_1 with one optical sensor 12b_3, one filter 12c, and one voltage application circuit 12d. As shown in FIG. 8, the scintillator 12a_1, the filter 12c, and the optical sensor 12b_3 are arranged in this order along the depth direction.

The optical sensor 12b_3 has a function of converting the light from the scintillator 12a_1 associated with the optical sensor 12b_3 into an electric signal according to the amount of light. That is, the optical sensor 12b_3 detects the light emitted from the single scintillator 12a_1 and outputs an electric signal corresponding to the detected light.

Here, the optical sensor 12b_3 has a wavelength sensitivity characteristic capable of detecting light 90 and light 91. That is, the wavelength of the light 90 (peak wavelength) and the wavelength of the light 91 (peak wavelength) are included in the wavelength band of the light that can be detected by the optical sensor 12b_3.

Therefore, when the light 90 is incident, the optical sensor 12b_3 detects the light 90 and outputs an electric signal corresponding to the light 90. Further, when the light 91 is incident, the optical sensor 12b_3 detects the light 91 and outputs an electric signal corresponding to the light 91.

The filter 12c is realized by a polarizing film such as a liquid crystal. The filter 12c is provided between the scintillator 12a_1 and the optical sensor 12b_3. The filter 12c has an optical property of transmitting light in a wavelength band according to the magnitude of the applied voltage. In the present embodiment, when the first voltage is applied, the filter 12c transmits light in the first wavelength band including the peak wavelength of light 90, and light in the second wavelength band including the peak wavelength of light 91. Block. Further, when a second voltage different from the first voltage is applied, the filter 12c transmits light in the first wavelength band and light in the second wavelength band.

The voltage application circuit 12d applies a voltage to the filter 12c under the control of the processing execution function 447. For example, the voltage application circuit 12d applies a first voltage or a second voltage to the filter 12c.

Returning to the description of FIG. 7, the processing circuit 44 reads the program corresponding to the processing execution function 447 from the memory 41 and executes it, thereby at least reducing the light 91 having a wavelength corresponding to the afterglow based on the scanning conditions. As described above, the process of controlling the optical characteristics of the filter 12c (second process) is executed. The processing execution function 447 is an example of a processing unit.

FIG. 9 is a flowchart showing a flow of an example of the second process executed by the X-ray CT apparatus 1 according to the second embodiment. As shown in the example of FIG. 9, the process execution function 447 acquires the scan condition from the memory 41 in which the scan condition is stored, similarly to the step S101 of the first process according to the first embodiment (step S201). ).

Then, the process execution function 447 determines whether to suppress the influence of the afterglow from the scan conditions or to improve the S / N while allowing the influence of the afterglow, as in the step S102 of the first process. , (Step S202).

When suppressing the influence of the afterglow (step S202: suppressing the influence of the afterglow), the process execution function 447 proceeds to step S203. In step S203, the process execution function 447 controls the voltage application circuit 12d so that the first voltage is applied to the filter 12c. For example, the processing execution function 447 controls the voltage application circuit 12d so as to apply the first voltage to the filter 12c.

In this case, the optical sensor 12b_3 detects the light 90 and outputs a first electric signal (an electric signal corresponding to the light 90). In the second embodiment, the first electrical signal is a signal that is the source of one channel of raw data used when the CT image data is reconstructed by the reconstruction processing function 444. Then, the DAS 18 generates the first detection data from the first electric signal. Then, the DAS 18 transmits the first detection data to the processing circuit 44.

Then, the preprocessing function 442 performs preprocessing on the first detection data. Then, the reconstruction processing function 444 reconstructs the CT image data by using the first raw data (the first detection data that has been preprocessed). Therefore, deterioration of the time resolution of the reconstructed CT image data and occurrence of artifacts can be suppressed.

On the other hand, when improving the S / N (step S202: improving the S / N), the process execution function 447 proceeds to step S204. In step S204, the process execution function 447 controls the voltage application circuit 12d so that the second voltage is applied to the filter 12c. For example, the processing execution function 447 controls the voltage application circuit 12d so as to apply the second voltage to the filter 12c.

In this case, the optical sensor 12b_3 detects the light 90 and the light 91 and outputs an electric signal corresponding to the light 90 and the light 91.

Then, the DAS 18 generates detection data corresponding to the light 90 and the light 91 from the electric signals corresponding to the light 90 and the light 91. Then, the DAS 18 transmits the detection data corresponding to the light 90 and the light 91 to the processing circuit 44.

Then, the preprocessing function 442 performs preprocessing on the detection data corresponding to the light 90 and the light 91. The raw data (detection data corresponding to the preprocessed light 90 and light 91) obtained by such processing is of one channel used when the CT image data is reconstructed by the reconstruction processing function 444. It is data. Then, the reconstruction processing function 444 reconstructs the CT image data using such raw data. Therefore, it is possible to improve the S / N of the reconstructed CT image data.

The X-ray CT apparatus 1 according to the second embodiment has been described above. According to the X-ray CT apparatus 1 according to the second embodiment, the influence of afterglow can be appropriately reduced as in the first embodiment.

(Third Embodiment)
Next, the X-ray CT apparatus 1 according to the third embodiment will be described. In the third embodiment, an optical sensor whose wavelength sensitivity characteristic can be changed is used.

FIG. 10 is a diagram showing an example of the configuration of the X-ray CT apparatus 1 according to the third embodiment. Hereinafter, in the description of the third embodiment, the points different from those of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment may be omitted. For example, the same components as those in the first embodiment may be designated by the same reference numerals and the description thereof may be omitted.

The point that the processing circuit 44 according to the third embodiment shown in FIG. 10 is provided with the processing execution function 448 instead of the processing execution function 443 according to the first embodiment is the first embodiment shown in FIG. It is different from the processing circuit 44. Further, as shown in FIG. 10, the third embodiment is different from the first embodiment in that the processing circuit 44 and the X-ray detector 12 can communicate with each other.

FIG. 11 is a diagram showing an example of the configuration of the X-ray detector 12 according to the third embodiment. As shown in FIG. 11, the X-ray detector 12 is an indirect conversion type detector having a scintillator array 12a, an optical sensor array 12b, a plurality of bias voltage application circuits 12e, and a grid (not shown). is there.

The scintillator array 12a has a plurality of scintillators 12a_1 as in the first embodiment.

The optical sensor array 12b has a plurality of optical sensors 12b_4. The optical sensor 12b_4 according to the third embodiment is realized by, for example, an avalanche photodiode. The X-ray detector 12 is configured such that one optical sensor 12b_4 and one bias voltage application circuit 12e are associated with a single (one) scintillator 12a_1. As shown in FIG. 11, the scintillator 12a_1 and the optical sensor 12b_4 are arranged in this order along the depth direction.

The optical sensor 12b_4 has a function of converting the light from the scintillator 12a_1 associated with the optical sensor 12b_4 into an electric signal according to the amount of light. That is, the optical sensor 12b_4 detects the light emitted from the single scintillator 12a_1 and outputs an electric signal corresponding to the detected light.

Here, the optical sensor 12b_4 has a wavelength sensitivity characteristic that changes according to the magnitude of the applied bias voltage. In the present embodiment, the optical sensor 12b_4 has a wavelength sensitivity characteristic that can detect the light 90 and cannot detect the light 91 when a third voltage is applied as the bias voltage. That is, when the third voltage is applied, the wavelength of the light 90 (peak wavelength) is included in the wavelength band of the light that can be detected by the optical sensor 12b_4, but the wavelength of the light 91 (peak wavelength). ) Is not included.

Therefore, when the third voltage is applied, the optical sensor 12b_4 detects the light 90 and outputs the first electric signal (electric signal corresponding to the light 90).

Further, in the present embodiment, the optical sensor 12b_4 has a wavelength sensitivity characteristic capable of detecting light 90 and light 91 when a fourth voltage different from the third voltage is applied as the bias voltage. That is, when the fourth voltage is applied, the wavelength of the light 90 (peak wavelength) and the wavelength of the light 91 (peak wavelength) are included in the wavelength band of the light that can be detected by the optical sensor 12b_4. .. For example, the fourth voltage is larger than the third voltage. The bias voltage is an example of the load voltage.

The bias voltage application circuit 12e applies a bias voltage to the optical sensor 12b_4 under the control of the processing execution function 448. For example, the bias voltage application circuit 12e applies a third voltage or a fourth voltage to the optical sensor 12b_4 as the bias voltage.

Returning to the description of FIG. 10, the processing circuit 44 reads the program corresponding to the processing execution function 448 from the memory 41 and executes it to determine the magnitude of the bias voltage applied to the optical sensor 12b_4 based on the scanning conditions. The process to be controlled (third process) is executed. Further, the processing circuit 44 executes a program corresponding to the processing execution function 448 to reduce the magnitude of the bias voltage so as to reduce the output of the signal corresponding to the wavelength corresponding to the afterglow based on the scan conditions. The process to be controlled is executed as the third process. The processing execution function 448 is an example of a processing unit.

FIG. 12 is a flowchart showing a flow of an example of a third process executed by the X-ray CT apparatus 1 according to the third embodiment. As shown in the example of FIG. 12, the process execution function 448 acquires the scan condition from the memory 41 in which the scan condition is stored, as in step S101 of the first process (step S301).

Then, the process execution function 448 determines whether to suppress the influence of the afterglow or to improve the S / N while allowing the influence of the afterglow from the scan conditions, as in the step S102 of the first process. , (Step S302).

When suppressing the influence of the afterglow (step S302: suppressing the influence of the afterglow), the process execution function 448 proceeds to step S303. In step S303, the process execution function 448 controls the bias voltage application circuit 12e so that the third voltage is applied to the optical sensor 12b_4. For example, the processing execution function 447 controls the bias voltage application circuit 12e so as to apply the third voltage to the optical sensor 12b_4.

In this case, the optical sensor 12b_4 detects the light 90 and outputs a first electric signal (an electric signal corresponding to the light 90). The first electric signal is a signal that is the source of the raw data of one channel that is the source of the CT image data that is reconstructed by the reconstruction processing function 444. Then, the DAS 18 generates the first detection data from the first electric signal. Then, the DAS 18 transmits the first detection data to the processing circuit 44.

Then, the preprocessing function 442 performs preprocessing on the first detection data. Then, the reconstruction processing function 444 reconstructs the CT image data by using the preprocessed first detection data (first raw data). Therefore, deterioration of the time resolution of the reconstructed CT image data and occurrence of artifacts can be suppressed.

On the other hand, when improving the S / N (step S302: improving the S / N), the process execution function 448 proceeds to step S304. In step S304, the process execution function 448 controls the bias voltage application circuit 12e so that the fourth voltage is applied to the optical sensor 12b_4. For example, the processing execution function 448 controls the bias voltage application circuit 12e so as to apply the fourth voltage to the optical sensor 12b_4.

In this case, the optical sensor 12b_3 detects the light 90 and the light 91 and outputs an electric signal corresponding to the light 90 and the light 91.

Then, the DAS 18 generates detection data corresponding to the light 90 and the light 91 from the electric signals corresponding to the light 90 and the light 91. Then, the DAS 18 transmits the detection data corresponding to the light 90 and the light 91 to the processing circuit 44.

Then, the preprocessing function 442 performs preprocessing on the detection data corresponding to the light 90 and the light 91. The reconstruction processing function 444 reconstructs the CT image data by using the raw data thus obtained (preprocessed detection data corresponding to the light 90 and the light 91). Therefore, it is possible to improve the S / N of the reconstructed CT image data.

The X-ray CT apparatus 1 according to the third embodiment has been described above. According to the X-ray CT apparatus 1 according to the third embodiment, the influence of afterglow can be appropriately reduced as in the first embodiment.

In the third embodiment, the case where the processing execution function 448 controls the magnitude of the bias voltage so as to reduce the output of the electric signal corresponding to the wavelength corresponding to the afterglow has been described in step S303. However, in step S303, the magnitude of the bias voltage may be controlled so that the processing execution function 448 increases the output of the electric signal corresponding to the wavelength corresponding to the main peak (peak wavelength of the light 90). In this case, the reconstruction processing function 444 reconstructs the CT image data by using the detection data (raw data) corresponding to the light 90 and the light 91, which has been preprocessed by the preprocessing function 442.

In each of the above-described embodiments and modifications, the case where the X-ray CT apparatus 1 executes various processes has been described. However, similar to the X-ray CT apparatus 1, a PET apparatus including a scintillator and a radiation detector including an optical sensor, and a radiodiagnostic apparatus such as a SPECT apparatus perform the same processing as various processes performed by the X-ray CT apparatus 1. May be executed.

Each component of each device according to the above-described embodiment is a functional concept, and does not necessarily have to be physically configured as shown in the figure. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or part of the device is functionally or physically distributed in arbitrary units according to various loads and usage conditions. It can be integrated and configured. Further, each processing function performed by each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

In addition, the various processes described in the above-described embodiment can be realized by executing a program prepared in advance on a computer such as a personal computer or a workstation. This program can be distributed via a network such as the Internet. The program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and read from the recording medium by the computer.

According to at least one embodiment or modification described above, the influence of afterglow can be appropriately reduced.

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

1 X-ray CT device 12 X-ray detector 43 Input interface 443 Processing execution function

Claims (9)

A radiation detector including a scintillator that emits light in response to incident radiation and an optical sensor that detects light emitted from the scintillator and outputs a signal corresponding to the light.
The reception section that accepts input of scan conditions and
A processing unit that executes a process of reducing the influence of afterglow on the output from the radiation detector based on the scan conditions, and a processing unit.
A radiological diagnostic device. The photodetector is configured by associating a single scintillator with a first photosensor and a second photosensor that detects light having a wavelength longer than that of the first photosensor.
The processing unit executes the processing that reduces the contribution of the second optical sensor as compared with the first optical sensor based on the scanning conditions.
The radiological diagnostic apparatus according to claim 1. The processing unit was obtained by adding data based on a signal output from the second optical sensor weighted by a predetermined coefficient to data based on a signal output from the first optical sensor. Control the data or the data based on the signal output from the first optical sensor among the first optical sensor and the second optical sensor so as to be used when reconstructing the radiographic image data. Perform the above process,
The radiological diagnostic apparatus according to claim 2. The photodetector is configured by associating a single scintillator with a first photosensor and a second photosensor that detects light having a wavelength longer than that of the first photosensor.
The processing unit executes the processing of increasing the contribution of the first optical sensor as compared with the second optical sensor based on the scanning conditions.
The radiological diagnostic apparatus according to claim 1. The radiological diagnostic apparatus according to any one of claims 2 to 4, wherein the sensational volume of the second optical sensor is larger than the sensational volume of the first optical sensor. Any of claims 2 to 5, wherein the processing unit estimates the energy of the incident radiation based on the signal output from the first optical sensor and the signal output from the second optical sensor. The radiological diagnostic apparatus according to one. The radiation detector further comprises a filter provided between the scintillator and the photosensor.
The radiation diagnostic apparatus according to claim 1, wherein the processing unit executes the processing for controlling the characteristics of the filter so as to reduce at least light having a wavelength corresponding to afterglow based on the scanning conditions. The optical sensor has a wavelength sensitivity characteristic that changes according to a load voltage.
The processing unit controls the load voltage based on the scanning conditions.
The radiological diagnostic apparatus according to claim 1. The optical sensor is an avalanche photodiode.
The processing unit reduces the output of the signal corresponding to the wavelength corresponding to the afterglow based on the scanning condition, or increases the output of the signal corresponding to the wavelength corresponding to the main peak. Controls the bias voltage applied to
The radiological diagnostic apparatus according to claim 8.

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