JP7301607B2 - Radiological diagnostic equipment - Google Patents

Description

An embodiment of the present invention relates to a radiological diagnostic apparatus.

2. Description of the Related Art In radiation diagnostic apparatuses such as X-ray CT (Computed Tomography) apparatuses, PET (Positron Emission Tomography) apparatuses, and SPECT (Single Photon Emission Computed Tomography) apparatuses, scintillators convert radiation such as X-rays and gamma rays into visible light. Visible light is then converted into an analog electrical signal by a photosensor such as a photodiode. Then, the analog electrical signal is converted into a digital electrical signal (digital data) by a DAS (Data Acquisition System) or the like.

A 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 in, for example, X-ray CT imaging. As a result, the time resolution of the radiographic image obtained by the radiodiagnostic apparatus deteriorates, artifacts occur in the radiographic image, and the radiographic image blurs. For example, in a dual energy scan in which the X-ray energy changes moment by moment, or a high-speed scan in which the X-ray tube and X-ray detector rotate at high speed, the afterglow causes a significant deterioration in the time resolution, or the afterglow Artifacts caused by this may occur remarkably. Also, when imaging an object to be imaged that moves relatively quickly, such as the heart, by high-speed scanning, temporal resolution is significantly deteriorated due to afterglow, and artifacts due to afterglow are significantly generated. .

On the other hand, the afterglow also improves the S/N (signal-to-noise ratio) of the electrical signal output from the optical sensor. For example, when photographing an object to be photographed such as a bone whose movement is small, the operator desires to improve the S/N even if the influence of afterglow is allowed in order to obtain an image with less noise. There is Also, for example, when photographing an object relatively susceptible to the effects of noise, such as the torso, in order to obtain an image with little noise, the S/N ratio should be good even if the influence of afterglow is allowed. There is an operator's desire to

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

JP-A-10-274675 Japanese Patent Publication No. 2016-519183 JP-A-11-160440

A problem to be solved by the present invention is to provide a radiological diagnostic apparatus that can appropriately reduce the influence of afterglow.

A radiation diagnostic apparatus according to an 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 a photosensor that detects light emitted from the scintillator and outputs a signal corresponding to the light. The reception unit receives 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 scan conditions.

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

Hereinafter, embodiments of a radiological diagnostic apparatus will be described in detail with reference to the drawings. Note that the contents described in one embodiment or modified example may be similarly applied to other embodiments or other modified examples.

(First embodiment)
The configuration of an 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 an X-ray CT apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus 1 has a gantry device 10, a bed device 30, and a console device 40. As shown in FIG. The X-ray CT apparatus 1 is an example of a radiodiagnostic apparatus.

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

The gantry device 10 has 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 collection 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 with thermoelectrons. The X-ray tube 11 emits thermal electrons from the cathode to the anode by applying a high voltage from the X-ray high voltage device 14, thereby generating X-rays to be irradiated to the subject P. As shown in FIG. For example, the X-ray tube 11 is a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermal electrons. Note that the X-ray tube 11 is an example of an X-ray generator.

The X-ray detector 12 detects X-rays emitted 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 detector element arrays in which a plurality of detector elements are arranged in the channel direction along one circular 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 detector element arrays each having a plurality of detector elements arranged in the channel direction are arranged in the column 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, a photosensor 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) corresponding to the amount of incident X-rays. That is, the scintillator 12a_1 emits light in response to incident X-rays. The grid is arranged on the X-ray incident side of the scintillator array 12a and has an X-ray shielding plate that absorbs scattered X-rays. Note that 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-rays and then immediately attenuated (prompt fluorescence). On the other hand, the light 91 is afterglow, and after being emitted from the scintillator 12a_1 with respect to the incident X-rays, it gradually attenuates over time. Here, the afterglow wavelength (peak wavelength) is generally longer than prompt fluorescence. In this embodiment, the wavelength (peak wavelength) of the light 91 is longer than the wavelength (peak wavelength) of the light 90 .

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

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

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

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

Returning to the description of FIG. 1, the rotation frame 13 supports the X-ray tube 11 and the X-ray detector 12 facing each other, and rotates the X-ray tube 11 and the X-ray detector 12 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 also support the X-ray high voltage device 14, the wedge 16, the collimator 17, the DAS 18, and the like. Additionally, the rotating frame 13 may further support various configurations not shown in FIG. Hereinafter, in the gantry device 10, the rotating frame 13 and the portion that rotates together with the rotating frame 13 are also referred to as a rotating portion.

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 that the X-ray tube 11 generates. and an X-ray controller for controlling the output voltage according to. The high voltage generator may be of a transformer type or an inverter type. The X-ray high-voltage device 14 may be provided on the rotating frame 13 or may be provided on a fixed frame (not shown).

The control device 15 has a processing circuit having a CPU (Central Processing Unit) and the like, and drive mechanisms such as motors and actuators. 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 motions of the bed device 30 and the tabletop 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 input inclination angle (tilt angle) information as control for tilting the gantry device 10 . Note that the control device 15 may be provided in the gantry device 10 or may be provided in the console device 40 .

Wedge 16 is a filter for adjusting the dose of X-rays emitted from X-ray tube 11 . Specifically, the wedge 16 transmits the X-rays emitted from the X-ray tube 11 so that the distribution of the X-rays emitted from the X-ray tube 11 to the subject P becomes a predetermined distribution. is a filter that attenuates For example, the wedge 16 is a wedge filter or a bow-tie filter, which is a filter made of 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 down the irradiation range of the X-rays transmitted through the wedge 16, and a slit is formed by combining a plurality of lead plates or the like. Note that the collimator 17 may also be called an X-ray diaphragm. 1 shows the case where the wedge 16 is arranged between the X-ray tube 11 and the collimator 17, the case where the collimator 17 is arranged between the X-ray tube 11 and the wedge 16 good too. In this case, the wedge 16 transmits and attenuates the X-rays emitted from the X-ray tube 11 and whose irradiation range is limited by the collimator 17 .

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

In the following description, detection data generated by the DAS 18 based on the first electrical signal (the electrical signal corresponding to the light 90) may be referred to as first detection data. Moreover, the detection data generated by the DAS 18 based on the second electrical signal (the electrical signal corresponding to the light 91) may be referred to as 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 to a non-rotating portion (for example, a fixed frame, etc.) of the gantry 10 by optical communication. (not shown) is transmitted to a receiver having a photodiode and transferred to the console device 40 . Here, the non-rotating portion is, for example, a fixed frame or the like 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 10 is not limited to optical communication, and any non-contact data transmission method may be employed. I don't mind if you hire me.

The bed device 30 is a device for placing and moving a subject P to be scanned, and has a base 31 , a bed driving device 32 , a top board 33 and a support frame 34 . The base 31 is a housing that supports the support frame 34 so as to be vertically movable. The bed drive device 32 is a drive mechanism that moves the table 33 on which the subject P is placed in the longitudinal direction of the table 33, and includes a motor, an actuator, and the like. A top plate 33 provided on the upper surface of the support frame 34 is a plate on which the subject P is placed. Note that the bed driving device 32 may move the support frame 34 in the longitudinal direction of the top plate 33 in addition to the top plate 33 .

The console device 40 has a memory 41 , a display 42 , an input interface 43 and a processing circuit 44 . Although the console device 40 is described as being separate from the gantry device 10 , the console device 40 or a part of each component of the console device 40 may be included in the gantry device 10 .

The memory 41 is implemented by, for example, a RAM (Random Access Memory), a semiconductor memory device such as a flash memory, a hard disk, an optical disk, or the like. The memory 41 stores projection data and reconstructed image data, for example. Also, for example, the memory 41 stores a program for the circuit included in the X-ray CT apparatus 1 to realize its function. Note that 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 the image data generated by the processing circuit 44, and displays a GUI (Graphical User Interface) for receiving various operations from operators such as doctors and radiological technologists. or For example, the display 42 is a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 42 may be of a desktop type, or may be configured by a tablet terminal or the like capable of wireless communication with the main body of the console device 40 .

The input interface 43 receives various input operations from the operator, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 44 . For example, the input interface 43 receives scan conditions from the operator. For example, the scan conditions include the tube voltage value and tube current value in the main scan, setting values related to the rotation speed of the rotating unit, FOV (Field Of View), imaging slice thickness, imaging range, imaging target region, 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 that performs input operations by touching the operation surface, a touch screen that integrates a display screen and a touch pad, and an optical sensor. It is realized by the used non-contact input circuit, voice input circuit, or the like. Note that the input interface 43 may be provided in the gantry device 10 . Also, the input interface 43 may be composed of a tablet terminal or the like capable of wireless communication with the main body of the console device 40 . Also, the input interface 43 is not limited to having physical operation parts such as a mouse and a 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 the processing circuit 44 is an example of the input interface 43. included. The input interface 43 is an example of a reception unit.

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

For example, the processing circuit 44 executes a system control function 441 , a preprocessing function 442 , a process execution function 443 , a reconstruction processing function 444 , an image processing function 445 and an output function 446 . For example, the processing circuit 44 reads out a program (control program) corresponding to the system control function 441 from the memory 41 and executes it, so that the processing circuit 44 may controls 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. , to perform positioning shooting. Further, the processing circuit 44 reads out and executes a program corresponding to the reconstruction processing function 444 from the memory 41 to generate positioning image data based on X-ray signals acquired by positioning imaging. Note that the positioning image data may also be called scanogram image data or 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. The system control function 441 then stores the acquired scan conditions in the memory 41 . Note that the system control function 441 may automatically set the scan conditions for the main 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 to perform a main scan for acquiring projection data, which will be described below. For example, the system control function 441 moves the subject P into the imaging port of the gantry device 10 by controlling the bed driving device 32 . Also, the system control function 441 adjusts the aperture and position of the collimator 17 . Also, the system control function 441 rotates the rotating portion by controlling the control device 15 . Also, the system control function 441 supplies a high voltage to the X-ray tube 11 by controlling the X-ray high voltage device 14 . Thereby, the X-ray tube 11 generates X-rays with which the subject P is irradiated.

While the main scan is being performed by the system control function 441, the DAS 18 collects signals of multiple X-rays detected by multiple detector elements and generates detection data. The processing circuit 44 also preprocesses the detection data output from the DAS 18 by reading out a program corresponding to the preprocessing function 442 from the memory 41 and executing the program. For example, the preprocessing function 442 performs preprocessing such as logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, and beam hardening correction on the detection data output from the DAS 18 . Note that data after preprocessing is also referred to as raw data. The detection data before preprocessing and the raw data after preprocessing are also collectively 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. Also, the second detection data preprocessed by the preprocessing function 442 may be referred to as second raw data.

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

The processing circuit 44 also reads out a program corresponding to the reconstruction processing function 444 from the memory 41 and executes it, thereby reconstructing CT image data based on the raw data after the first processing. Specifically, the reconstruction processing function 444 performs reconstruction processing using the filtered back projection method, the iterative reconstruction method, or the like on the raw data after the first processing, and reconstructs the CT image data. do. The reconstruction processing function 444 is an example of a reconstruction processing unit. CT image data is an example of radiation image data. A CT image is an example of a radiation 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 converts the reconstructed CT image data into tomographic image data or three-dimensional image data of an arbitrary cross section by a known method based on an input operation or the like received from the operator via the input interface 43. Convert to The image processing function 445 also stores the converted tomographic image data and three-dimensional image data in the memory 41 .

Further, the processing circuit 44 reads out a program corresponding to the output function 446 from the memory 41 and executes it to output tomographic image data, three-dimensional image data, CT image data, and the like. For example, the output function 446 causes the display 42 to display various images such as a tomographic image indicated by the tomographic image data and a CT image indicated by the CT image data. The output function 446 is an example of a display controller. Also, for example, the output function 446 outputs tomographic image data, three-dimensional image data, and CT image data to an external device (for example, a server device that stores image data) connected to the X-ray CT apparatus 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 computer-executable program. The processing circuit 44 is a processor that implements 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 a state where each program has been read has a function corresponding to the read program. Note that in FIG. 1, the processing functions 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 are realized by a single processing circuit 44. Although the case is shown, 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 implement each processing function by executing each program. Further, each processing function of the processing circuit 44 may be appropriately distributed or integrated in a single or a plurality of processing circuits and implemented.

The term "processor" used in the above description is, 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 ( Circuits such as Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), or Field Programmable Gate Array (FPGA)). The processor implements functions by reading and executing programs stored in the memory 41 .

In FIG. 1, the single memory 41 has been described as storing programs corresponding to each processing function. However, a configuration may be adopted in which a plurality of memories 41 are distributed and the processing circuit 44 reads corresponding programs from individual memories 41 . Also, instead of storing the program in the memory 41, the program may be configured to be directly embedded in the circuit of the processor. In this case, the processor realizes its function by reading and executing the program embedded in the circuit.

Also, the processing circuit 44 may implement various functions using a processor of an external device connected via a network. For example, the processing circuit 44 reads and executes a program corresponding to each function from the memory 41, and uses an external workstation or server group (cloud) connected to the X-ray CT apparatus 1 via a network as computational resources. , each function shown in FIG. 1 may be realized.

An 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 performs various processes described below so as to appropriately reduce the influence of afterglow.

FIG. 3 is a flow chart showing 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 conditions from the memory 41 storing the scan conditions (step S101).

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

For example, if the object to be imaged included in the scan conditions is a region such as the heart that moves relatively quickly, it is conceivable that afterglow will cause deterioration in temporal resolution and the occurrence of artifacts. Also, when the energy of irradiated X-rays indicated by the scanning conditions changes every moment (for example, in the case of dual energy acquisition), it is conceivable that afterglow will cause deterioration of time resolution and generation of artifacts.

Therefore, in these cases, that is, when suppressing the effect of afterglow (step S102: suppressing the effect of afterglow), the processing execution function 443 proceeds to step S103. In step S103, the process execution function 443 adds raw data obtained by weighting the second raw data by 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. Also, "D1" indicates the first raw data, "D2" indicates the second raw data, and "D3" indicates the third raw data. Also, the coefficient α is a value of 0 or more and less than 1. As the value of the coefficient α approaches 0, the effect of afterglow on the CT image data reconstructed from the third raw data becomes smaller. On the other hand, as the value of the coefficient α approaches 1, the effect of afterglow on the CT image data reconstructed from the third raw data increases. The value of coefficient α is set by the operator, for example.

In Equation (1), "α×D2" indicates 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 reconstruction processing function 444 reconstructs CT image data.

In this way, the processing execution function 443 reduces the contribution of the optical sensor 12b_2 compared to the optical sensor 12b_1 based on the scan conditions. Specifically, the processing execution function 443 determines that the ratio of the second raw data based on the second electrical signal output from the optical sensor 12b_2 to the first raw data based on the first electrical signal output from the optical sensor 12b_1 is A third raw data is generated to be 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 ends. In this case, the reconstruction processing function 444 uses the third raw data to reconstruct the CT image data. Therefore, it is possible to suppress the deterioration of the time resolution of the reconstructed CT image data and the occurrence of artifacts.

Here, there is a conventional method of using a measured value of afterglow as a model and correcting it 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 reduced more reliably than the conventional method. Further, according to the X-ray CT apparatus 1 according to the first embodiment, it is possible to reduce the influence of afterglow with less processing load than the processing load when performing correction by a computer in the conventional method.

On the other hand, if the object to be imaged included in the scan conditions is a site such as a bone that moves relatively little, it is conceivable to improve the S/N even if the influence of afterglow is allowed. In addition, even if the object to be imaged included in the scan conditions is a part that is relatively susceptible to noise, such as the trunk of the body, it is conceivable to improve the S/N even if the influence of afterglow is allowed. be done. Therefore, in these cases, that is, when improving the S/N (step S102: improving the S/N), the processing execution function 443 proceeds to step S104.

In step S104, the process execution function 443 generates 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 reconstructing CT image data by the reconstruction processing function 444 . Then, the first process ends. In this case, the reconstruction processing function 444 uses the fourth raw data to reconstruct the CT image data. Therefore, the S/N of the reconstructed CT image data can be improved.

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

(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 sensors 12b_1 and 12b_2 is not limited to this. Therefore, another example of arrangement of the optical sensor 12b_1 and the optical sensor 12b_2 will be described as Modified Example 1 of the first embodiment.

Hereinafter, in the description of Modified Example 1 of the first embodiment, differences from the first embodiment will be mainly described, and the description of the same configuration as 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 Modification 1 of the first embodiment.

As shown in FIG. 4, the optical sensors 12b_1 and 12b_2 are arranged side by side along one surface of the scintillator 12a_1 instead of in the depth direction indicated by the arrow 92 . Therefore, according to Modification 1 of the first embodiment, it is possible to suppress an increase in the dimension of the photosensor array 12b in the depth direction as compared with the first embodiment. That is, according to Modification 1 of the first embodiment, it is possible to suppress an increase in the size of the photosensor array 12b.

Modification 1 of the first embodiment has been described above. According to Modification 1 of the first embodiment, even when the optical sensors 12b_1 and 12b_2 are arranged as shown in FIG. 4, the influence of afterglow is appropriately reduced as in the first embodiment. can be made Further, according to Modification 1 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, the type of material forming the optical sensor 12b_1 and the type of material forming the optical sensor 12b_2 are different. The case where is different is explained. However, the type of material forming the optical sensor 12b_1 and the type of material forming the optical sensor 12b_2 may be the same. The wavelength sensitivity characteristic of the optical sensor 12b_1 and the wavelength sensitivity characteristic of the optical sensor 12b_2 may be different by differentiating the sensitive volume of the optical sensor 12b_1 and the sensitive volume of the optical sensor 12b_2. Therefore, such a modification will be described as Modification 2 of the first embodiment.

Hereinafter, in the description of Modified Example 2 of the first embodiment, differences from the first embodiment will be mainly described, and the description of the same configuration as the first embodiment may be omitted. In Modified Example 2 of the first embodiment, the type of material forming the optical sensor 12b_1 and the type of material forming the optical sensor 12b_2 are the same. However, as will be described later, the sensitive volume of the optical sensor 12b_1 and the sensitive volume of the optical sensor 12b_2 are different.

FIG. 5A is a diagram showing an example of the sensitive volume of the optical sensor 12b_2 according to Modification 2 of the first embodiment. FIG. 5B is a diagram showing an example of the sensitive volume of the optical sensor 12b_1 according to Modification 2 of the first embodiment. Here, the sensitive volume is schematically represented by a rectangular parallelepiped.

As shown in FIGS. 5A and 5B, the sensitive volume of the optical sensor 12b_2 and the sensitive volume of the optical sensor 12b_1 have a common side of length L1 and a side of length L2. One surface F of the two surfaces defined by the side of length L1 and the side of length L2 faces one surface of scintillator 12a_1. The side of length L3 extending in the depth direction indicated by arrow 92 shown in FIG. 5A is longer than the side of 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 photosensors 12b_1 and 12b_1, the deeper the position where carriers are generated in the depth direction. Therefore, the sensitive volume of the optical sensor 12b_2 is larger than the sensitive volume of the optical sensor 12b_1.

With such a configuration, the optical sensor 12b_1 has wavelength sensitivity characteristics capable of detecting the light 90, and the optical sensor 12b_2 has wavelength sensitivity characteristics capable of detecting the light 90 and the light 91. FIG. In Modified Example 2, the X-ray CT apparatus 1 uses the electrical signal output from the optical sensor 12b_1 as the first electrical signal and the electrical signal output from the optical sensor 12b_2 as the second electrical signal. Perform the same processing as for the form.

Modification 2 of the first embodiment has been described above. According to Modification 2 of the first embodiment, even if the type of material forming the optical sensor 12b_1 and the type of material forming the optical sensor 12b_2 are the same, the wavelength sensitivity characteristic of the optical sensor 12b_1 is , the wavelength sensitivity characteristic of the optical sensor 12b_2 can be made different. Moreover, according to the modification 2 of the first embodiment, the same effects as those of the first embodiment are obtained.

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

Hereinafter, in the description of Modified Example 3 of the first embodiment, differences from the first embodiment will be mainly described, and the description of the same configuration as 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 Modification 3 of the first embodiment.

As shown in FIG. 6, the processing execution function 443 according to Modification 3 of the first embodiment includes data (for example, first raw data) 61 based on the electrical signal output from the optical sensor 12b_1 and the optical sensor 12b_2. A difference D or ratio with data (for example, second raw data) 62 based on the electrical 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 scintillation light propagates inside the scintillator 12a_1, the transmittance of light in the medium of the scintillator 12a_1 varies depending on the wavelength. Therefore, the larger the difference D, the longer the distance that light travels in the scintillator 12a_1. That is, the larger the difference D, the more shallow 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 positions. That is, the processing execution function 443 estimates the energy of the incident X-ray based on the electrical signal output from the optical sensor 12b_1 and the electrical signal output from the optical sensor 12b_2. For example, the processing execution function 443 estimates the energy of incident X-rays based on data based on the electrical signal output from the optical sensor 12b_1 and data based on the electrical signal output from the optical sensor 12b_2.

The energy estimated in this way is used, for example, in applications such as performing spectral CT.

The X-ray CT apparatus 1 according to Modification 3 of the first embodiment has been described above. According to the X-ray CT apparatus 1 according to Modification 3 of the first embodiment, the energy of incident X-rays can be estimated. Further, according to the X-ray CT apparatus 1 according to Modification 3 of the first embodiment, the same effects as those of the first embodiment are obtained.

(Modification 4 of the first embodiment)
When suppressing the influence of afterglow, the DAS 18 may generate a third electrical signal by amplifying the first electrical signal and adding the second electrical signal to the amplified first electrical signal. good. The third electrical signal is a signal that is a source of one-channel raw data used when reconstructing CT image data. Therefore, such a modification will be described as Modification 4 of the first embodiment.

Hereinafter, in the description of Modified Example 4 of the first embodiment, differences from the first embodiment will be mainly described, and descriptions of configurations similar to those of the first embodiment may be omitted.

In variant 4 of the first embodiment, the DAS 18 has processing circuitry and an amplifier. A processing circuit is a circuit capable of processing data in digital form. For example, the processing circuitry is implemented by a processor. The amplifier performs amplification processing for amplifying the first electrical signal.

Then, in Modification 4, the processing execution function 443 acquires the scan conditions from the memory 41 in which the scan conditions are stored, as in the first embodiment. Then, as in the first embodiment, the processing 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 scanning conditions. judge. The processing execution function 443 then transmits determination result information indicating the determination result to the processing circuit of the DAS 18 . The determination result information is information indicating that the influence of afterglow should be suppressed, or that the S/N should be improved while allowing the influence of afterglow.

The processing circuitry of DAS 18 then receives the determination result information. Then, the processing circuit of the DAS 18 causes the amplifier to amplify the first electrical signal when the determination result information indicates that the influence of afterglow should be suppressed. Then, the processing circuitry of DAS 18 generates a third electrical signal by adding an electrical signal obtained by weighting the second electrical signal by a factor α to the amplified first electrical signal. The third electrical signal is data that is the source of 1-channel raw data used when reconstructing CT image data by the reconstruction processing function 444 . Thus, the processing circuitry of the DAS 18 executes processing to increase the contribution of the photosensor 12b_1 relative to the photosensor 12b_2 based on the scan conditions. The DAS 18 according to modification 4 is an example of a processing unit.

DAS 18 then generates detection data from the third electrical signal. A preprocessing function 442 preprocesses the detected data. Then, the reconstruction processing function 444 reconstructs CT image data using the preprocessed detection data (raw data). Therefore, according to Modification 4, it is possible to suppress the deterioration of the temporal resolution of reconstructed CT image data and the occurrence of artifacts.

On the other hand, the processing circuit of the DAS 18 adds the second electrical signal to the first electrical signal when the determination result information indicates that the S/N should be improved while allowing the influence of afterglow. 4 Generate electrical signals. The fourth electrical signal is data that is the source of one-channel raw data used when reconstructing CT image data by the reconstruction processing function 444 .

DAS 18 then generates detection data from the fourth electrical signal. A preprocessing function 442 preprocesses the detected data. Then, the reconstruction processing function 444 reconstructs CT image data using the preprocessed detection data (raw data). Therefore, the S/N of the reconstructed CT image data can be improved.

The X-ray CT apparatus 1 according to Modification 4 of the first embodiment has been described above. The X-ray CT apparatus 1 according to Modification 4 of the first embodiment has the same effects as those of the first embodiment.

It should be noted that in Modification 4, the processing execution function 443 may transmit the scan conditions to the processing circuit of the DAS 18 . Then, the processing circuit of the DAS 18 may determine, from the scan conditions, whether to suppress the influence of afterglow or to improve the S/N while allowing the influence of afterglow.

(Modification 5 of the first embodiment)
Note that when suppressing the influence of afterglow, the X-ray detector 12 is configured such that the charge integration time in the photosensor 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 electrical signal and the second electrical signal obtained under the integration time thus controlled. The electric signal obtained by such addition is the original signal of one-channel raw data used when reconstructing the CT image data. Therefore, such a modification will be described as Modification 5 of the first embodiment.

Hereinafter, in the description of Modified Example 5 of the first embodiment, differences from the first embodiment will be mainly described, and descriptions of configurations similar to those of the first embodiment may be omitted.

In variant 5 of the first embodiment, the X-ray detector 12 comprises a processing circuit. In Modified Example 5, the X-ray detector 12 and the processing circuit 44 can communicate with each other. Then, in Modification 5, the processing execution function 443 transmits determination result information to the processing circuit of the X-ray detector 12 . Note that the determination result information according to Modification 5 is the same information as the determination result information according to Modification 4. FIG.

Then, the processing circuit of the X-ray detector 12 receives the determination result information. Then, when the determination result information indicates that the influence of afterglow is suppressed, the processing circuit of the X-ray detector 12 sets the charge integration time in the photosensor 12b_2 to be 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 that The processing circuit of DAS 18 then adds the first electrical signal obtained under the controlled integration time and the second electrical signal. The electric signal obtained by such addition is the original signal of one-channel raw data used when reconstructing the CT image data by the reconstruction processing function 444 . In this case, DAS 18 generates detection data from the electrical signals resulting from such summation. A preprocessing function 442 preprocesses the detected data. Then, the reconstruction processing function 444 reconstructs CT image data using the preprocessed detection data (raw data). Therefore, it is possible to suppress the deterioration of the time resolution of reconstructed CT image data and the occurrence of artifacts.

On the other hand, when the determination result information indicates that the S/N should be improved while allowing the influence of afterglow, the processing circuit of the X-ray detector 12 determines the integration time of the charge 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 processing circuit of DAS 18 then adds the first electrical signal obtained under the controlled integration time and the second electrical signal. The electric signal obtained by such addition is the original signal of one-channel raw data used when reconstructing the CT image data by the reconstruction processing function 444 . In this case, the DAS 18 generates detection data from the electrical signals obtained by summation. A preprocessing function 442 preprocesses the detected data. Then, the reconstruction processing function 444 reconstructs CT image data using the preprocessed detection data (raw data). Therefore, the S/N of the reconstructed CT image data can be improved.

The X-ray CT apparatus 1 according to Modification 5 of the first embodiment has been described above. According to the X-ray CT apparatus 1 according to Modification 5 of the first embodiment, the same effects as those of the first embodiment are obtained.

It should be noted that in Modification 5, the processing execution function 443 may transmit the scan conditions to the processing circuit of the X-ray detector 12 . Then, the processing circuit of the X-ray detector 12 may determine from the scan conditions whether to suppress the influence of afterglow or to improve the S/N while allowing the influence of afterglow. .

In the above-described first embodiment, the processing execution function 443 uses first raw data (preprocessed first detection data) and second raw data (preprocessed second detection data). , the case of executing various processes has been described. However, based on the determination result information, the processing circuit of the DAS 18 detects the first detection data (detection data generated based on the first electrical signal) and the second detection data (detection data generated based on the second electrical signal). data) may be subjected to similar processing. Also, the processing circuitry of DAS 18 may perform similar processing on the first electrical signal and the second electrical signal. Also in this case, the same effect as in the first embodiment can be obtained. The amount of data transmitted from the DAS 18 to the console device 40 can be reduced by the processing circuit of the DAS 18 performing the processing described above.

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

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, differences from the first embodiment will be mainly described, and description of the same configuration as the first embodiment may be omitted. For example, configurations similar to those of the first embodiment may be denoted by the same reference numerals, and description thereof may be omitted.

The processing circuit 44 according to the second embodiment shown in FIG. 7 has a processing execution function 447 instead of the processing execution function 443 according to the first embodiment, unlike the first embodiment shown in FIG. It is different from the processing circuit 44 concerned. Further, as shown in FIG. 7, the second embodiment differs from the first embodiment in that communication between the processing circuit 44 and the X-ray detector 12 is possible.

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 a scintillator array 12a, a photosensor array 12b, a plurality of filters 12c, a plurality of voltage application circuits 12d, and a grid (not shown). type detector.

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

The photosensor array 12b has a plurality of photosensors 12b_3. The optical sensor 12b_3 according to the second embodiment is implemented by, for example, a photodiode. The X-ray detector 12 is configured such that one photosensor 12b_3, one filter 12c, and one voltage application circuit 12d are associated with a single (one) scintillator 12a_1. As shown in FIG. 8, a scintillator 12a_1, a filter 12c, and an 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 electrical signal corresponding to the amount of light. That is, the photosensor 12b_3 detects light emitted from the single scintillator 12a_1 and outputs an electrical signal corresponding to the detected light.

Here, the optical sensor 12b_3 has wavelength sensitivity characteristics that can detect the light 90 and the light 91 . That is, the wavelength band of light detectable by the optical sensor 12b_3 includes the wavelength of the light 90 (peak wavelength) and the wavelength of the light 91 (peak wavelength).

Therefore, when the light 90 is incident, the optical sensor 12b_3 detects the light 90 and outputs an electrical signal corresponding to the light 90. FIG. In addition, 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 liquid crystal. The filter 12c is provided between the scintillator 12a_1 and the photosensor 12b_3. The filter 12c has an optical characteristic of transmitting light in a wavelength band corresponding to the magnitude of the applied voltage. In this embodiment, when the first voltage is applied, the filter 12c transmits light in a first wavelength band including the peak wavelength of the light 90, and transmits light in a second wavelength band including the peak wavelength of the light 91. block the 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 process execution function 447. FIG. 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 out and executes a program corresponding to the processing execution function 447 from the memory 41, thereby at least reducing the light 91 of the wavelength corresponding to the afterglow based on the scan conditions. , a process (second process) for controlling the optical characteristics of the filter 12c is executed. The processing execution function 447 is an example of a processing unit.

FIG. 9 is a flow chart showing 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 conditions from the memory 41 storing the scan conditions (step S201), as in step S101 of the first process according to the first embodiment. ).

Then, similarly to step S102 of the first process, the processing execution function 447 determines whether to suppress the influence of afterglow or to improve the S/N while allowing the influence of afterglow from the scanning conditions. , is determined (step S202).

If the effect of afterglow is to be suppressed (step S202: suppress the effect of afterglow), the processing 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 process execution function 447 controls the voltage application circuit 12d 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 electrical signal (an electrical signal corresponding to the light 90). In the second embodiment, the first electrical signal is a source signal of one-channel raw data used when reconstructing CT image data by the reconstruction processing function 444 . DAS 18 then generates first detection data from the first electrical signal. DAS 18 then transmits the first sensed data to processing circuitry 44 .

Then, the preprocessing function 442 preprocesses the first detection data. Then, the reconstruction processing function 444 reconstructs the CT image data using the first raw data (preprocessed first detection data). Therefore, 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, if the S/N is to be improved (step S202: S/N improvement), the processing 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 process execution function 447 controls the voltage application circuit 12d 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 electrical signal corresponding to the light 90 and the light 91. FIG.

The DAS 18 then generates detection data corresponding to the light 90 and the light 91 from electrical signals corresponding to the light 90 and the light 91 . DAS 18 then transmits detection data corresponding to light 90 and light 91 to processing circuit 44 .

A pre-processing function 442 pre-processes the detection data corresponding to the light 90 and the light 91 . The raw data obtained by such processing (detection data corresponding to preprocessed light 90 and light 91) is a 1-channel data used when reconstructing CT image data by the reconstruction processing function 444. Data. Then, the reconstruction processing function 444 reconstructs CT image data using such raw data. Therefore, the S/N of the reconstructed CT image data can be improved.

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, an X-ray CT apparatus 1 according to a 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, differences from the first embodiment will be mainly described, and the description of the same configuration as the first embodiment may be omitted. For example, configurations similar to those of the first embodiment may be denoted by the same reference numerals, and description thereof may be omitted.

The processing circuit 44 according to the third embodiment shown in FIG. 10 differs from the first embodiment shown in FIG. 1 in that it includes a process execution function 448 instead of the process execution function 443 according to the first embodiment. It is different from the processing circuit 44 concerned. Further, as shown in FIG. 10, the third embodiment differs from the first embodiment in that communication between the processing circuit 44 and the X-ray detector 12 is possible.

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, a photosensor array 12b, a plurality of bias voltage applying circuits 12e, and a grid (not shown). be.

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

The photosensor array 12b has a plurality of photosensors 12b_4. The optical sensor 12b_4 according to the third embodiment is implemented by, for example, an avalanche photodiode. The X-ray detector 12 is configured such that one photosensor 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 photosensor 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 electrical signal corresponding to the amount of light. That is, the photosensor 12b_4 detects light emitted from the single scintillator 12a_1 and outputs an electrical signal corresponding to the detected light.

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

Therefore, when the third voltage is applied, the photosensor 12b_4 detects the light 90 and outputs a first electrical signal (an electrical signal corresponding to the light 90).

Further, in the present embodiment, the optical sensor 12b_4 has wavelength sensitivity characteristics capable of detecting the light 90 and the 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 band of light detectable by the optical sensor 12b_4 includes the wavelength (peak wavelength) of the light 90 and the wavelength (peak wavelength) of the light 91. . For example, the fourth voltage is greater than the third voltage. A bias voltage is an example of a load voltage.

The bias voltage application circuit 12e is controlled by the process execution function 448 and applies a bias voltage to the photosensor 12b_4. For example, the bias voltage application circuit 12e applies the third voltage or the fourth voltage as the bias voltage to the photosensor 12b_4.

Returning to the description of FIG. 10, the processing circuit 44 reads out a program corresponding to the processing execution function 448 from the memory 41 and executes it, thereby determining the magnitude of the bias voltage applied to the photosensor 12b_4 based on the scan conditions. A 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 based on the scan conditions so as to reduce the output of the signal corresponding to the wavelength corresponding to the afterglow. 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 flow chart showing an example of the 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 conditions from the memory 41 storing the scan conditions, as in step S101 of the first process (step S301).

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

If the effect of afterglow is suppressed (step S302: suppress the effect of afterglow), the processing 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 photosensor 12b_4. For example, the process execution function 447 controls the bias voltage application circuit 12e to apply the third voltage to the photosensor 12b_4.

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

Then, the preprocessing function 442 preprocesses the first detection data. Then, the reconstruction processing function 444 reconstructs CT image data using the preprocessed first detection data (first raw data). Therefore, 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, if the S/N is to be improved (step S302: S/N improvement), the processing 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 photosensor 12b_4. For example, the process execution function 448 controls the bias voltage application circuit 12e to apply the fourth voltage to the photosensor 12b_4.

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

The DAS 18 then generates detection data corresponding to the light 90 and the light 91 from electrical signals corresponding to the light 90 and the light 91 . DAS 18 then transmits detection data corresponding to light 90 and light 91 to processing circuit 44 .

A pre-processing function 442 pre-processes the detection data corresponding to the light 90 and the light 91 . The reconstruction processing function 444 reconstructs CT image data using the raw data thus obtained (preprocessed detection data corresponding to the light 90 and the light 91). Therefore, the S/N of the reconstructed CT image data can be improved.

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, similarly to the first embodiment, it is possible to appropriately reduce the influence of afterglow.

In the third embodiment, in step S303, the processing execution function 448 controls the magnitude of the bias voltage so as to reduce the output of the electrical signal corresponding to the wavelength corresponding to afterglow. However, in step S303, the process execution function 448 may control the magnitude of the bias voltage so as to increase the output of the electrical signal corresponding to the wavelength corresponding to the main peak (the peak wavelength of the light 90). In this case, the reconstruction processing function 444 reconstructs CT image data using detection data (raw data) corresponding to the light 90 and light 91 preprocessed by the preprocessing function 442 .

In each of the embodiments and modifications described above, cases where the X-ray CT apparatus 1 executes various types of processing have been described. However, similar to the X-ray CT apparatus 1, a PET apparatus equipped with a radiation detector including a scintillator and an optical sensor, and a radiation diagnostic apparatus such as a SPECT apparatus perform the same processing as the various processes executed by the X-ray CT apparatus 1. may be executed.

Each component of each device according to the above-described embodiments is functionally conceptual, and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution/integration of each device is not limited to the illustrated one, and all or part of them can be functionally or physically distributed/integrated in arbitrary units according to various loads and usage conditions. Can be integrated and configured. Furthermore, all or any part of each processing function performed by each device can be implemented by a CPU and a program analyzed and executed by the CPU, or implemented as hardware based on wired logic.

Also, various processes described in the above-described embodiments can be realized by executing a prepared program 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 recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, DVD, etc., and executed by being read from the recording medium by a computer.

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

While several embodiments of the invention have been described, these embodiments have been presented by way of example 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 modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 X-ray CT apparatus 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 a photosensor that detects light emitted from the scintillator and outputs a signal corresponding to the light;
a reception unit that receives an input of scanning conditions including a region to be imaged or a tube voltage value ;
a first process for reducing the influence of afterglow on the output from the radiation detector or output from the radiation detector based on the imaging target site or the tube voltage value included in the scan conditions; a processing unit that performs a second process of controlling the radiation detector so as to produce an output with a reduced effect of glow;
A radiological diagnostic device comprising: The radiation detector is configured such that a first photosensor and a second photosensor that detects light having a longer wavelength than the first photosensor are associated with a single scintillator,
The processing unit performs the first process of reducing the contribution of the second photosensor compared to the first photosensor based on the scan condition.
The radiation diagnostic apparatus according to claim 1. The processing unit adds data based on the signal output from the second photosensor weighted by a predetermined coefficient to data based on the signal output from the first photosensor. Data, or data based on a signal output from the first optical sensor out of the first optical sensor and the second optical sensor, is controlled to be used when reconstructing radiation image data. executing the first process;
The radiation diagnostic apparatus according to claim 2. The radiation detector is configured such that a first photosensor and a second photosensor that detects light having a longer wavelength than the first photosensor are associated with a single scintillator,
The processing unit performs the first process of increasing the contribution of the first photosensor compared to the second photosensor based on the scan condition.
The radiation diagnostic apparatus according to claim 1. 5. The radiation diagnostic apparatus according to claim 2, wherein the sensitive volume of said second photosensor is larger than the sensitive volume of said first photosensor. 6. The processing unit estimates the energy of the incident radiation based on the signal output from the first photosensor and the signal output from the second photosensor. 1. A radiological diagnostic apparatus according to claim 1. The radiation detector further comprises a filter provided between the scintillator and the photosensor,
2. The radiation diagnostic apparatus according to claim 1, wherein said processing unit executes said second processing of controlling characteristics of said filter so as to at least reduce light of a wavelength corresponding to afterglow based on said scanning conditions. . The optical sensor has a wavelength sensitivity characteristic that changes according to the load voltage,
The processing unit executes the second process of controlling the load voltage based on the scan conditions.
The radiation 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, or increases the output of the signal corresponding to the wavelength corresponding to the main peak, based on the scanning conditions. controls the bias voltage applied to
A radiation diagnostic apparatus according to claim 8 .

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