JP7233911B2 - X-ray CT system and processing program - Google Patents

Description

Embodiments of the present invention relate to X-ray CT systems and processing programs.

Conventionally, in an X-ray CT (Computed Tomography) system, it is possible to display a confirmation image for confirming the movement of the subject, the imaging range, and the like immediately after scanning. Specifically, in the X-ray CT system, by quickly providing the operator with confirmation images to check whether the CT image data obtained by scanning has been acquired as planned, the subsequent workflow enable rapid progress. For example, when the operator refers to the confirmation image displayed immediately after scanning and determines that the acquisition is as planned, the operator can quickly remove the subject from the couch apparatus. Also, for example, when the operator determines that confirmation images have not been collected as planned, the operator can quickly perform rescanning. Here, the image for confirmation is, for example, an image generated without performing image processing such as correction on projection data collected by scanning.

In addition, in the X-ray CT system, there are techniques for dual-energy (DE) acquisition using X-rays with two different energies in the scan, and X-rays with three or more different energies in the CT scan. Techniques for Multi-Energy (ME) collection using wires are known. This makes it possible to collect projection data corresponding to each energy and to discriminate the types, atomic numbers, densities, etc. of substances contained in the subject by utilizing the fact that X-ray absorption characteristics differ for each substance. be. DE acquisition or ME acquisition is performed, for example, by a “rapid kV switching method (KV switching method)” in which the energy of X-rays is changed for each irradiation angle of X-rays with respect to the subject. In the “rapid kV switching method”, for example, the energy of X-rays is changed for each one or more views.

JP 2015-62657 A Japanese Patent Publication No. 2016-531692

A problem to be solved by the present invention is to efficiently obtain a confirmation image for the purpose of confirming a photographing range or the like.

An X-ray CT system according to an embodiment includes an X-ray irradiation section, an X-ray control section, an X-ray detection section, a data processing section, and a reconstruction section. The X-ray irradiation unit irradiates the object with X-rays while rotating around the object. The X-ray control unit periodically changes the energy of the X-rays while the X-ray irradiation unit makes one rotation around the subject. An x-ray detector detects the x-rays and collects a projection data set for each rotational position of the x-ray emitter. The data processing unit includes a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated. At least one of the projection data sets is subjected to processing including correction processing according to the difference in the amount of transmission between the X-rays of the first energy and the X-rays of the second energy. The reconstruction unit reconstructs an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set.

FIG. 1 is a block diagram showing an example configuration of an X-ray CT system according to the first embodiment. FIG. 2 is a diagram for explaining scaling processing by the data processing function according to the first embodiment. FIG. 3 is a diagram for explaining processing by the data processing function according to the first embodiment. FIG. 4 is a flowchart for explaining the processing flow of the X-ray CT system according to the first embodiment. FIG. 5 is a diagram for explaining filter processing by a data processing function according to another embodiment. FIG. 6 is a block diagram showing an example configuration of an X-ray CT system according to another embodiment.

Hereinafter, embodiments of an X-ray CT system and a processing program according to embodiments will be described in detail with reference to the accompanying drawings. Note that the line CT system and processing program according to the present application are not limited to the embodiments shown below.

(First embodiment)
First, the configuration of an X-ray CT system 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing an example configuration of an X-ray CT system 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT system 1 has a gantry device 10, a bed device 30, and a console device 40. As shown in FIG. That is, the X-ray CT system 1 according to the first embodiment is also called an X-ray CT 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. Also, the axial direction perpendicular to the Z-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 system 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 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 irradiation unit.

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). Also, the X-ray detector 12 is, for example, an indirect conversion type detector having a grid, a scintillator array, and a photosensor array. The scintillator array has a plurality of scintillators. The scintillator has a scintillator crystal that outputs a photon amount of light corresponding to the amount of incident X-rays. The grid is arranged on the surface of the scintillator array on the X-ray incident side 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). The photosensor array has a function of converting the amount of light from the scintillator into an electrical signal, and has photosensors such as photodiodes, for example. The X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into electrical signals. Also, the X-ray detector 12 is an example of an X-ray detection unit.

The rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 so as to face each other and rotates the X-ray tube 11 and the X-ray detector 12 by the control device 15 . 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 and attenuates the X-rays irradiated from the X-ray tube 11 so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution. It is a filter that 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 the 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. DAS 18 is implemented by, for example, a processor. Note that, hereinafter, detection data generated by the DAS may be referred to as projection data.

Here, the DAS 18 may be a sequential collection DAS that sequentially collects X-ray signals detected by a plurality of detection elements, or may simultaneously collect X-ray signals detected by a plurality of detection elements. A simultaneous collection DAS may be used.

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 CT image data, for example. In addition, for example, the memory 41 stores programs for the circuits included in the X-ray CT system 1 to implement their functions. Note that the memory 41 may be realized by a server group (cloud) connected to the X-ray CT system 1 via a network.

The display 42 displays various information. For example, the display 42 displays a CT image generated by the processing circuit 44, an image for confirmation, and a GUI (Graphical User Interface) for accepting various operations from the operator. 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 allows the operator to input acquisition conditions for acquiring projection data, reconstruction conditions for reconstructing CT image data, image processing conditions for generating CT images from CT image data, and the like. accept. 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.

A processing circuit 44 controls the operation of the entire X-ray CT system 1 . For example, processing circuitry 44 performs system control functions 441 , data processing functions 442 , preprocessing functions 443 , reconstruction functions 444 and output functions 445 . That is, the processing circuit 44 controls the operation of the entire X-ray CT system 1 by reading out and executing programs corresponding to each function from the memory 41 . Note that the system control function 441 is an example of an X-ray control unit. Also, the data processing function 442 is an example of a data processing unit. Also, the reconstruction function 444 is an example of a reconstruction unit.

In the X-ray CT system 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 the 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.

Although FIG. 2 shows the case where the processing functions of the system control function 441, the data processing function 442, the preprocessing function 443, the reconstruction function 444, and the output function 445 are realized by a single processing circuit 44, , 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 system control function 441 controls various processes in the X-ray CT system 1 based on input operations received from the operator via the input interface 43 . For example, the system control function 441 controls the bed driving device 32, the collimator 17, the control device 15, the X-ray high-voltage device 14, etc. in the X-ray CT system 1 to perform positioning scans and main scans.

Here, the system control function 441 controls the “dual energy imaging” by the “rapid kV switching method”. Specifically, the system control function 441 transmits a control signal for switching between a high voltage and a low voltage to the X-ray high voltage device 14 , so that the X-ray high voltage device 14 transfers the high voltage to the X-ray tube 11 . Control the application of low voltage. Further, the system control function 441 transmits a control signal to the DAS 18 to determine whether the detected detection data is from high-voltage X-ray irradiation or from low-voltage X-ray irradiation. Control to identify whether

The data processing function 442 generates projection data for generating confirmation images by performing various processes on the projection data collected by the “dual energy imaging” by the “rapid kV switching method”. . Specifically, the data processing function 442 generates projection data for generating a confirmation image by performing scaling processing and the like on the detection data (projection data) generated by the DAS 18 . For example, the data processing function 442 may process at least one of the projection data of the first tube voltage (eg, high voltage) and the projection data of the second tube voltage (eg, low voltage). , to generate projection data for generating images for confirmation. The projection data generated by data processing function 442 is stored in memory 41 . Details of the processing by the data processing function 442 will be described later. Further, hereinafter, the projection data of each tube voltage acquired while alternately switching the tube voltage by the "rapid kV switching method" will be referred to as a projection data set.

The preprocessing function 443 performs correction processing such as logarithmic conversion processing, offset correction, sensitivity correction, beam hardening correction, etc. on the detection data (projection data) transmitted from the DAS 18, thereby converting the projection data after preprocessing into to generate For example, the pre-processing function 443 generates a pre-processed projection data set from detected data (projection data) at a first tube voltage (eg, high voltage). Also, the preprocessing function 443 generates a post-preprocessing projection data set from the detection data (projection data) of the second tube voltage (eg, low voltage).

In addition, the preprocessing function 443 uses two types of projection data sets to determine two or more predetermined reference substances (water, iodine, calcium, hydroxyapatite, fat, etc.) present in the imaging target site. To separate. The preprocessing function 443 then generates two or more monochromatic x-ray preprocessed projection data sets corresponding to each of the two or more reference materials. For example, the preprocessing function 443 generates preprocessed projection data sets for water and iodine monochromatic x-rays from the high energy and low energy preprocessed projection data sets, respectively. Note that the preprocessed projection data set generated by the preprocessing function 443 is stored by the memory 41 .

A reconstruction function 444 generates various images from the preprocessed projection data sets stored by the memory 41 and stores the generated images in the memory 41 . For example, the reconstruction function 444 reconstructs CT image data by reconstructing preprocessed projection data by various reconstruction methods (for example, back projection method such as FBP (Filtered Back Projection), iterative approximation method, etc.). It reconstructs and stores the reconstructed CT image data in the memory 41 . The reconstruction function 444 also performs various image processing to generate a CT image such as an MPR image from the CT image data, and stores the generated CT image in the memory 41 .

For example, the reconstruction function 444 reads the preprocessed projection data set of monochromatic X-rays of the reference material stored by the memory 41 and reconstructs the reference material image data (reference material-enhanced image data). In one example, the reconstruction function 444 reconstructs the reference material image data for the water component based on the preprocessed projection data set with the water component enhanced and the preprocessed projection data set with the iodine component enhanced. Reconstruct the reference material image data of the iodine component based on. Further, the reconstruction function 444 generates a water component reference substance image and an iodine component reference substance image by executing image processing on the water component reference substance image data and the iodine component reference substance image data, respectively. do. In addition, the reconstruction function 444 generates various images such as a monochromatic X-ray image, a density image, and an effective atomic number image at a predetermined energy by performing weighting calculation processing using two reference material image data. can be done.

Also, for example, the reconstruction function 444 reads the high-energy preprocessed projection data sets and the low-energy preprocessed projection data sets stored by the memory 41, and reconstructs the CT image data from each preprocessed projection data set. are reconstructed respectively. The reconstruction function 444 can then generate from the CT image data a multicolor x-ray image corresponding to high energy and a multicolor x-ray image corresponding to low energy.

A reconstruction function 444 reconstructs the projection data set generated by the data processing function 442 by various reconstruction methods (for example, back projection method such as FBP (Filtered Back Projection), iterative approximation method, etc.). CT image data is reconstructed by this, and the reconstructed CT image data is stored in the memory 41 . The reconstruction function 444 also performs various image processing to generate a confirmation image from the CT image data, and stores the generated confirmation image in the memory 41 .

The output function 445 causes the display 42 to display a CT image generated by the reconstruction function 444, an image for confirmation, and the like.

The overall configuration of the X-ray CT system 1 according to this embodiment has been described above. With such a configuration, the X-ray CT system 1 according to this embodiment makes it possible to efficiently obtain confirmation images for purposes such as confirmation of the imaging range. Specifically, the X-ray CT system 1 makes it possible to quickly provide images for confirmation while maintaining constant image quality even in imaging at a plurality of different energies by the "Rapid kV switching method".

As described above, in imaging by the “rapid kV switching method”, X-ray energy is changed for each one or a plurality of views, so projection data with different energies are mixed. Therefore, the X-ray transmission amount in the projection data corresponding to each energy is different. For example, at higher energies, more x-rays are transmitted than at lower energies. Therefore, if an image for confirmation is generated using such a projection data set, artifacts may occur and the image may not be used for confirmation. Further, for example, it is possible to generate an image for confirmation using only a projection data set corresponding to one energy, but in this case, the data is thinned out and partially lost, resulting in artifacts. and cannot be used for confirmation.

Therefore, in the X-ray CT system 1 according to the present embodiment, a confirmation image with reduced artifacts is generated by performing correction processing according to the difference in the amount of transmission at different energies. Specifically, in the X-ray CT system 1, the processing of the data processing function 442 reduces the difference in the amount of transmission. In addition, below, the process which reduces the difference in the transmission amount is described as the scaling process.

Data processing function 442 processes a plurality of first projection data sets acquired when X-rays of a first energy are applied and a plurality of second projection data sets acquired when X-rays of a second energy are applied. At least one of the two projection data sets is subjected to processing including correction processing according to the difference in the amount of transmission between the X-rays of the first energy and the X-rays of the second energy. Specifically, the data processing function 442 includes a plurality of first projection data sets and a plurality of Correction processing is performed on at least one of the second projection data sets.

FIG. 2 is a diagram for explaining scaling processing by the data processing function 442 according to the first embodiment. Note that FIG. 2 shows a part of the projection data collected by the “dual energy imaging” by the “rapid kV switching method”. That is, the high-energy rectangle and low-energy rectangle shown in FIG. , respectively.

For example, the data processing function 442 performs a correction process of multiplying the plurality of first projection data sets or the plurality of second projection data sets by a coefficient based on the difference in the amount of transmission. In one example, the data processing function 442 multiplies each high energy projection data set (high energy data in the figure) by a "factor a" as shown in the lower left diagram of FIG. That is, the data processing function 442 multiplies the value of the projection data in each view included in the high energy projection data set by the "factor a". Here, the “coefficient a” is calculated based on the difference in transmission amount, and the X-ray transmission amount in the high-energy projection data set is changed to the X-ray transmission amount in the low-energy projection data set. This is a coefficient for approximation.

Alternatively, for example, the data processing function 442 multiplies each low-energy projection data set (low-energy data in the figure) by a "factor b", as shown in the bottom middle diagram of FIG. That is, the data processing function 442 multiplies the value of the projection data in each view included in the low energy projection data set by the "factor b". Here, the "coefficient b" is calculated based on the difference in transmission amount, and the X-ray transmission amount in the low-energy projection data set is changed to the X-ray transmission amount in the high-energy projection data set. This is a coefficient for approximation.

Here, the “coefficient a” and “coefficient b” described above are calculated in advance and stored in the memory 41 . For example, high-energy data and low-energy data are collected in advance, and the difference in X-ray transmission amount is calculated. Then, a coefficient is calculated from the calculated transmission amount difference and stored in the memory 41 . Such coefficients are stored in the memory 41 for each combination of energies, and the data processing function 442 reads the coefficients corresponding to the currently used combination of energies from the memory 41 and performs scaling processing.

In addition, as another process of multiplying coefficients, for example, the data processing function 442 multiplies a plurality of first projection data sets by a coefficient based on the difference between the first energy and the third energy to obtain a plurality of first projection data sets. A correction process is performed on the two projection data sets by applying a coefficient based on the difference between the second energy and the third energy. That is, the data processing function 442 multiplies the projection data set for each energy by a factor to approximate the amount of X-ray transmission at one target energy. In addition, 3rd energy is energy between 1st energy and 2nd energy, for example.

For example, the data processing function 442 multiplies each of the high energy data by a “coefficient c”, and multiplies each of the low energy data by a “coefficient d”, as shown in the lower right diagram of FIG. Multiply by That is, the data processing function 442 multiplies the projection data value in each view included in the high-energy projection data set by the “coefficient c” to obtain the projection data value in each view included in the low-energy projection data set. is multiplied by "factor d". Here, "coefficient c" is a coefficient for approximating the amount of X-ray transmission in the high-energy projection data set to the amount of X-ray transmission at the energy of the target. "Coefficient d" is a coefficient for approximating the amount of X-ray transmission in the low-energy projection data set to the amount of X-ray transmission at the energy of the target.

Here, the scaling processing using the above-described "coefficient c" and "coefficient d" can be executed by applying the processing in beam hardening correction. For example, beam hardening corrections are performed on the acquired projection data to approximate the amount of targeted monochromatic energy transmission. Therefore, the data processing function 442 performs correction processing on the high-energy projection data set and the low-energy projection data set so as to approximate the amount of transmission of the target monochromatic energy. As a result, the amount of transmission in the high-energy projection data set and the amount of transmission in the low-energy projection data set approximate the amount of transmission of the target monochromatic energy, and the amounts of transmission also approximate each other.

In the above-described embodiment, the case where the coefficient used for scaling processing is calculated from the difference in the actual amount of transmission and the case where the coefficient used for beam hardening correction is applied to the scaling processing coefficient have been described. However, the embodiment is not limited to this, and a theoretically calculated value may be used. For example, the X-ray transmission amount at the first energy and the X-ray transmission amount at the second energy may be calculated logically, and the coefficient may be calculated from the difference between the calculated transmission amounts.

As described above, the data processing function 442 performs correction processing by multiplying the plurality of first projection data sets or the plurality of second projection data sets by a coefficient based on the difference in the amount of transmission. As a result, the X-ray CT system 1 can reduce the difference in the amount of X-ray transmission in projection data sets in which different energies are mixed, and can generate confirmation images with reduced artifacts.

For example, the reconstruction function 444 can generate an artifact-reduced confirmation image using any of the three coefficient-multiplied projection data sets shown in the bottom row of FIG. .

Here, the X-ray CT system 1 according to the first embodiment can further perform processing for reducing artifacts. Specifically, data processing functionality 442 generates a plurality of first interpolated data sets corresponding to rotational positions not exposed to the first energy based on the plurality of first projection data sets, An interpolation process is performed based on the two projection data sets to generate a plurality of second interpolation data sets corresponding to rotational positions not exposed to the second energy. Further, the data processing function 442 generates a first synthesized data set by synthesizing the first projection data set corresponding to the rotational position of the X-ray irradiation unit and the second interpolation data set, A second combined data set is generated by combining the data set and the first interpolated data set.

FIG. 3 is a diagram for explaining processing by the data processing function 442 according to the first embodiment. Here, FIG. 3 shows processing after the scaling processing shown in FIG. That is, the top projection data set in FIG. 3 corresponds to one of the coefficient multiplied bottom projection data sets in FIG.

For example, the data processing function 442 separates a projection data set containing mixed high energy data and low energy data into a high energy data projection data set and a low energy data projection data set, as shown in FIG. . Then, as shown in FIG. 3, the data processing function 442 generates missing portion data for each of the projection data set of high energy data and the projection data set of low energy data by interpolation processing.

For example, the data processing function 442 uses multiple high-energy projection data sets to generate interpolated data sets for missing portions (rotational positions not exposed to high-energy x-rays). Similarly, the data processing function 442 uses the low-energy projection data sets to generate interpolated data sets for missing portions (rotational positions not exposed to low-energy x-rays). That is, the data processing function 442 generates a high-energy interpolated data set for rotational positions irradiated with low-energy X-rays, and a low-energy interpolated data set for rotational positions irradiated with high-energy X-rays. to generate

It should be noted that the method of interpolation processing performed by the data processing function 442 can be any interpolation method that can generate an interpolation data set from a projection data set, such as linear interpolation, Lagrangian interpolation, or sigmoidal interpolation. may be used.

Data processing function 442 then generates a composite data set by combining the actually acquired projection data set and the generated interpolation data set for each rotational position. For example, the data processing function 442 generates a combined data set “(HD1) & (LID1)” by combining the high energy data (HD1) and the low energy interpolated data (LID1), as shown in FIG. The data processing function 442 also generates a combined data set "(HID1) & (LD1)" by combining the high energy interpolation data (HID1) and the low energy data (LD1), as shown in FIG. Similarly, data processing function 442 generates a composite data set that combines the actually acquired projection data set and the generated interpolated data set.

Here, the data processing function 442 weights the actually acquired projection data set rather than the interpolated data set in order to use more of the information of the actually acquired projection data, and performs synthesis processing. For example, the data processing function 442 generates a composite data set “(HD1) & (LID1)” by the formula “(W _b ×HD1)+(1−W _b )×LID1” using the weight “W _b ”. , the weight is set to "W _b =0.75". This increases the information amount of the high energy data (HD1) in the combined data set "(HD1) &(LID1)". The data processing function 442 similarly weights the actually acquired projection data sets over the interpolated data sets when generating other composite data sets.

The reconstruction function 444 generates an image for confirmation by performing reconstruction processing and the like on the projection data sets (a plurality of synthesized data sets) after the synthesis processing by the data processing function 442 . The output function 445 causes the display 42 to display the confirmation image generated by the reconstruction function 444 .

As described above, in the X-ray CT system 1 according to the first embodiment, artifacts are reduced by executing the scaling process, and furthermore, by performing the synthesis process on the projection data set after the scaling process, the A confirmation image with reduced artifacts can be generated.

Next, an example of the procedure of processing by the X-ray CT system 1 will be described with reference to FIG. FIG. 4 is a flowchart for explaining the processing flow of the X-ray CT system 1 according to the first embodiment. Here, FIG. 4 shows a case where the combining process is performed after the scaling process. In addition, FIG. 4 shows a case of displaying an image for confirmation in "imaging by dual energy".

Step S<b>101 is implemented by the processing circuit 44 reading and executing a program corresponding to the system control function 441 . Steps S102 to S106 are steps implemented by the processing circuit 44 reading and executing a program corresponding to the data processing function 442 . Step S<b>107 is a step implemented by the processing circuit 44 reading out and executing a program corresponding to the reconstruction function 444 . Step S108 is a step implemented by the processing circuit 44 reading and executing a program corresponding to the output function 445. FIG.

First, the processing circuit 44 collects high energy data and low energy data by the "rapid kV switching method" (step S101). Next, the processing circuit 44 performs scaling processing (step S102), and separates the data after the scaling processing into high energy data and low energy data (step S103). After that, the processing circuit 44 generates interpolated data in the high energy data and interpolated data in the low energy data (steps S104, 105).

Processing circuitry 44 then performs a weighted addition to include more information from the actually acquired projection data set (step S106). After that, the processing circuit 44 generates a confirmation image using the generated projection data set (step S107), and causes the display 42 to display the confirmation image (step S108).

As described above, according to the first embodiment, the X-ray tube 11 emits X-rays while rotating around the subject. The system control function 441 periodically changes the energy of X-rays while the X-ray tube 11 makes one rotation around the subject. The X-ray detector 12 detects X-rays and collects projection data sets for each rotational position of the X-ray emitter. Data processing function 442 processes a plurality of first projection data sets acquired when X-rays of a first energy are applied and a plurality of second projection data sets acquired when X-rays of a second energy are applied. At least one of the two projection data sets is subjected to processing including correction processing according to the difference in the amount of transmission between the X-rays of the first energy and the X-rays of the second energy. A reconstruction function 444 reconstructs an image based on a composite data set generated based on a plurality of projection data sets, including the processed projection data set. Therefore, the X-ray CT system 1 according to the first embodiment can reduce artifacts due to differences in the amount of X-ray transmission between projection data sets acquired by the "rapid kV switching method", and the imaging range It is possible to efficiently obtain a confirmation image for the purpose of confirming, etc.

The present embodiment can be applied to both a system that switches the tube voltage for each view and a system that switches the tube voltage for each of a plurality of views, and generates confirmation images with reduced artifacts in each. be able to. In particular, in a system that switches the tube voltage for each of a plurality of views, since the rotation angle acquired with the same energy is large, the artifacts that occur in the confirmation image become conspicuous. Therefore, it is more effective to apply this embodiment to a system that switches such tube voltages for each of a plurality of views.

Also, according to the first embodiment, the data processing function 442 is configured to reduce the transmission difference between the X-rays of the first energy and the X-rays of the second energy. Correction processing is performed on at least one of the projection data set and the plurality of second projection data sets. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to reduce the difference in the amount of transmitted X-rays between projection data sets acquired by the "rapid kV switching method".

Further, according to the first embodiment, the data processing function 442 executes correction processing by multiplying a plurality of first projection data sets or a plurality of second projection data sets by a coefficient based on the difference in transmission amount. . Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to easily reduce the difference in X-ray transmission between projection data sets acquired by the "rapid kV switching method". .

Further, according to the first embodiment, the data processing function 442 multiplies the plurality of first projection data sets by a coefficient based on the difference between the first energy and the third energy to obtain a plurality of second projection data sets. A correction process is performed on the projection data set by applying a coefficient based on the difference between the second energy and the third energy. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to match the transmission amount of X-rays in the projection data set acquired by the "rapid kV switching method" to the transmission amount of desired energy.

Further, according to the first embodiment, the processing by the data processing function 442 includes a plurality of first interpolated data corresponding to rotational positions where the first energy was not applied, based on the plurality of first projection data sets. generating a set and, based on the plurality of second projection data sets, generating a plurality of second interpolated data sets corresponding to rotational positions not exposed to the second energy. The data processing function 442 generates a first synthesized data set by synthesizing the first projection data set and the second interpolation data set corresponding to the rotational position of the X-ray tube 11, and generates the second projection data set corresponding to the rotational position of the X-ray tube 11. and the first interpolated data set to generate a second combined data set. A reconstruction function 444 reconstructs the image using the first synthetic data set and the second synthetic data set. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to further reduce artifacts.

Further, according to the first embodiment, the data processing function 442 weights the ratio of the first projection data set and the second projection data set so that the ratio of the first projection data set and the second projection data set is increased to obtain the first synthetic data set and the second synthetic data set. respectively. Therefore, the X-ray CT system 1 according to the first embodiment makes it possible to generate confirmation images that contain more information about the collected data.

(Other embodiments)
Although the first embodiment has been described so far, it may be implemented in various different forms other than the first embodiment described above.

In the above-described first embodiment, a case has been described in which an image for confirmation is generated from a projection data set after synthesis processing. However, embodiments are not limited to this, and further filtering may be applied to the synthesized projection data set. FIG. 5 is a diagram for explaining filter processing by the data processing function 442 according to another embodiment. Here, FIG. 5 shows projection data sets (a plurality of synthesized data sets) after the synthesizing process shown in FIG.

For example, the data processing function 442 applies different filters to multiple projection data sets and then combines the multiple projection data sets after application. In one example, the data processing function 442 duplicates the projection data sets after the synthesis process and applies a smoothing filter and a high-pass filter to each projection data set, respectively, as shown in FIG. Data processing function 442 then combines each filtered projection data set to produce a filtered projection data set.

For example, the data processing function 442 synthesizes the smoothing filtered synthetic data set “(HD1) & (LID1)” and the high pass filtered synthetic data set “(HD1) & (LID1)”. A combined data set “(HD1) & (LID1)” is generated. Similarly, the data processing function 442 generates a composite data set obtained by combining the smoothing filtered composite data set and the high pass filtered composite data set for the composite data set at other rotational positions.

Here, the data processing function 442 can also generate a synthesized data set that equally includes the information in the synthesized dataset with the smoothing filter applied and the information in the synthesized dataset with the high-pass filter applied in the above-described synthesis processing. However, the same weighting as in the combining process described in the first embodiment can also be performed. That is, the data processing function 442 may perform a synthesis process to include more information in either the smoothing filtered synthetic data set or the high pass filtered synthetic data set.

For equal inclusion of information in the smoothed filtered synthetic data set and the information in the high-pass filtered synthetic data set, for example, the data processing function 442 processes the smoothed filtered synthetic data set and the high-pass filtered synthetic data set. Each data set is weighted by 0.5 and synthesized. On the other hand, when the synthesis process is performed so as to include more information of either one, the data processing function 442 performs Synthesize by applying a weight with a larger value.

This can reduce some streak-like artifacts that may remain in the synthetic dataset before filtering. In the above example, the case of performing filter processing using both the smoothing filter and the high-pass filter has been described, but it is also possible to perform filter processing using either filter.

In addition, in the above-described first embodiment, (shooting by Dual-Energy) has been described as an example. However, the embodiments are not limited to this, and even when applied to projection data sets acquired using X-rays of three or more different energies (multi-energy imaging) good.

Further, in the above-described first embodiment, a plurality of high-energy projection data sets are used to generate interpolation data sets for missing portions (rotational positions not irradiated with high-energy X-rays), and low-energy projection data sets are generated. A case has been described in which multiple projection data sets are used to generate interpolation data sets for missing portions (rotational positions not irradiated with low-energy X-rays). However, the embodiment is not limited to this, and an interpolation data set may be generated only for rotational positions corresponding to transition times when switching energies.

For example, when the high energy is set to "140 kVp" and the low energy is set to "80 kVp", a transition time occurs when switching each tube voltage. That is, there is a transition time during which the tube voltage gradually decreases until it changes from "140 kVp" to "80 kVp". Further, there is a transition time during which the tube voltage gradually rises until it changes from "80 kVp" to "140 kVp". During this transition time, a projection data set is acquired in which X-rays are emitted while the tube voltage is changed.

Therefore, the data processing function 442 generates an interpolation data set only for the missing part of the rotational position corresponding to this transition time. That is, data processing function 442 generates an interpolated data set from the actually acquired projection data set for the rotational position corresponding to this transition time in the scaled projection data set.

Also, the X-ray CT system 1 according to the first embodiment has been described as a system (X-ray CT apparatus) in which the gantry device 10, the bed device 30, and the console device 40 are interconnected. However, the embodiments are not limited to this, and for example, the X-ray CT system of the present application may be configured such that part of the above-described processing is distributed and performed by devices on a network. .

FIG. 6 is a block diagram showing an example configuration of an X-ray CT system 100 according to another embodiment. Note that, unlike the X-ray CT system 1 shown in FIG. 1, the X-ray CT system 100 according to another embodiment has an image processing server 2, and the X-ray CT apparatus has a communication interface 45. The difference is that the image processing server 2 is connected to the image processing server 2 via the network NW. Hereinafter, the same reference numerals as those in FIG. 1 are assigned to the same configurations as those described in the first embodiment, and descriptions thereof are omitted.

The communication interface 45 is connected to the processing circuit 44 and controls transmission and communication of various data with the image processing server 2 connected via the network NW. For example, the communication interface 45 is implemented by a network card, network adapter, NIC (Network Interface Controller), or the like. In one example, communication interface 45 transmits projection data sets generated by DAS 18 to image processing server 2 . The communication interface 45 also receives the processed projection data set from the image processing server 2 and outputs it to the processing circuit 44 .

The image processing server 2 has a communication interface 21 , a memory 22 and a processing circuit 23 .

The communication interface 21 is connected to the processing circuit 23 and controls transmission and communication of various data with an X-ray CT apparatus connected via the network NW. For example, the communication interface 21 is implemented by a network card, network adapter, NIC (Network Interface Controller), or the like. In one example, communication interface 21 receives projection data sets from an X-ray CT apparatus and outputs them to processing circuitry 23 . The communication interface 21 also outputs the processed projection data set processed by the processing circuit 23 to the X-ray CT apparatus.

The memory 22 is connected to the processing circuit 23 and stores various data. For example, the memory 22 is realized by semiconductor memory elements such as RAM (Random Access Memory) and flash memory, hard disks, optical disks, and the like. For example, the memory stores projection data sets received from an X-ray CT apparatus. The memory 22 also stores programs corresponding to each processing function executed by the processing circuit 23 .

The processing circuitry 23 performs a data processing function 231 and a reconstruction function 232 . That is, the processing circuit 23 reads and executes a program corresponding to each function from the memory 22 to control the operation of the image processing server. Specifically, the data processing function 231 executes the same processing as the data processing function 442 described above. Also, the reconstruction function 232 executes processing similar to that of the reconstruction function 444 described above. Note that the data processing function 231 is an example of a data processing unit. Also, the reconstruction function 232 is an example of a reconstruction unit.

In the image processing server 2 shown in FIG. 6, each processing function is stored in the memory 22 in the form of a computer-executable program. The processing circuit 23 is a processor that implements a function corresponding to each program by reading the program from the memory 22 and executing the program. In other words, the processing circuit 23 having read each program has a function corresponding to the read program.

Note that FIG. 6 shows a case where the processing functions of the data processing function 231 and the reconstruction function 232 are implemented by a single processing circuit 23, but the embodiment is not limited to this. For example, the processing circuit 23 may be configured by combining a plurality of independent processors, and each processor may implement each processing function by executing each program. Moreover, each processing function of the processing circuit 23 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 includes, for example, a CPU, a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device ( Circuits such as Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). The processor implements its functions by reading and executing programs stored in the memory 41 or memory 22 .

In FIG. 1, the single memory 41 has been described as storing programs corresponding to each processing function. Also, in FIG. 6, the single memory 22 has been described as storing a program corresponding to each processing function. However, embodiments are not so limited. For example, a configuration may be adopted in which a plurality of memories 41 are distributed and the processing circuit 44 reads corresponding programs from the individual memories 41 . Further, for example, a configuration may be adopted in which a plurality of memories 22 are distributed and the processing circuit 23 reads corresponding programs from the individual memories 22 . Also, instead of storing the program in the memory 41 or memory 22, the program may be directly embedded in the circuit of the processor. In this case, the processor implements its functions by reading and executing the program embedded in the circuit.

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.

Further, the processing program described in the above embodiment can be realized by executing a prepared processing program on a computer such as a personal computer or a work station. This processing program can be distributed via a network such as the Internet. In addition, this processing program is recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, DVD, etc., and can be executed by being read from the recording medium by a computer.

According to at least one embodiment described above, it is possible to efficiently obtain a confirmation image for the purpose of confirming the imaging range or the like.

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, 100 X-ray CT system 11 X-ray tube 12 X-ray detector 23, 44 Processing circuit 441 System control function 231, 442 Data processing function 232, 444 Reconstruction function

Claims (14)

an X-ray irradiation unit that emits X-rays while rotating around a subject;
an X-ray control unit that periodically changes the energy of the X-ray while the X-ray irradiation unit makes one rotation around the subject;
an X-ray detector that detects the X-rays and collects a projection data set for each rotational position of the X-ray emitter;
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing unit that performs processing including correction processing according to a difference in transmission amount between the first energy X-rays and the second energy X-rays for at least one of them;
a plurality of projection data sets including a first projection data set and a second projection data set after the processing is performed on at least one of the plurality of first projection data sets and the plurality of second projection data sets; a reconstruction unit for reconstructing an image based on a synthetic dataset generated based on the projection dataset;
An X-ray CT system with an X-ray irradiation unit that emits X-rays while rotating around a subject;
an X-ray control unit that periodically changes the energy of the X-ray while the X-ray irradiation unit makes one rotation around the subject;
an X-ray detector that detects the X-rays and collects a projection data set for each rotational position of the X-ray emitter;
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing unit that performs processing including correction processing according to a difference in transmission amount between the first energy X-rays and the second energy X-rays for at least one of them;
a reconstruction unit configured to reconstruct an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set;
with
The data processing unit reduces a difference in transmission amount between the X-rays of the first energy and the X-rays of the second energy. An X-ray CT system that performs correction processing by multiplying two projection data sets by a coefficient based on the difference in the amount of transmission. an X-ray irradiation unit that emits X-rays while rotating around a subject;
an X-ray control unit that periodically changes the energy of the X-ray while the X-ray irradiation unit makes one rotation around the subject;
an X-ray detector that detects the X-rays and collects a projection data set for each rotational position of the X-ray emitter;
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing unit that performs processing including correction processing according to a difference in transmission amount between the first energy X-rays and the second energy X-rays for at least one of them;
a reconstruction unit configured to reconstruct an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set;
with
The data processing unit performs the following on the plurality of first projection data sets so as to reduce a difference in transmission amount between the X-rays of the first energy and the X-rays of the second energy. Correction by multiplying the plurality of second projection data sets by a coefficient based on the difference between the first energy and the third energy, and multiplying the plurality of second projection data sets by a coefficient based on the difference between the second energy and the third energy. An X-ray CT system that performs the processing. an X-ray irradiation unit that emits X-rays while rotating around a subject;
an X-ray control unit that periodically changes the energy of the X-ray while the X-ray irradiation unit makes one rotation around the subject;
an X-ray detector that detects the X-rays and collects a projection data set for each rotational position of the X-ray emitter;
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing unit that performs processing including correction processing according to a difference in transmission amount between the first energy X-rays and the second energy X-rays for at least one of them;
a reconstruction unit configured to reconstruct an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set;
with
The process generates a plurality of first interpolated data sets corresponding to rotational positions not exposed to the first energy based on the plurality of first projection data sets, and the plurality of second projection data sets. generating a plurality of second interpolated data sets corresponding to rotational positions not exposed to the second energy based on
The data processing unit generates a first combined data set by combining a first projection data set corresponding to the rotational position of the X-ray irradiation unit and a second interpolation data set, and generates a first combined data set by combining a second projection data set corresponding to the rotational position of the X-ray irradiation unit. generating a second composite data set by combining the data set and the first interpolated data set;
The X-ray CT system, wherein the reconstruction unit reconstructs an image using the first synthetic data set and the second synthetic data set. The data processing unit reduces a difference in transmission amount between the X-rays of the first energy and the X-rays of the second energy. 5. An X-ray CT system according to claim 1 or 4 , wherein correction processing is performed on at least one of the two projection data sets. 6. The X according to claim 5 , wherein the data processing unit executes correction processing by multiplying the plurality of first projection data sets or the plurality of second projection data sets by a coefficient based on the difference in the amount of transmission. Line CT system. The data processing unit multiplies the plurality of first projection data sets by a coefficient based on the difference between the first energy and the third energy, and multiplies the plurality of second projection data sets by the 6. The X-ray CT system according to claim 5 , wherein correction processing is performed by applying a coefficient based on the difference between the second energy and the third energy. The process generates a plurality of first interpolated data sets corresponding to rotational positions not exposed to the first energy based on the plurality of first projection data sets, and the plurality of second projection data sets. The X-ray CT according to any one of claims 1 to 3 , comprising interpolation processing for generating a plurality of second interpolation data sets corresponding to rotational positions not irradiated with the second energy based on system. The data processing unit generates a first combined data set by combining a first projection data set corresponding to the rotational position of the X-ray irradiation unit and a second interpolation data set, and generates a first combined data set by combining a second projection data set corresponding to the rotational position of the X-ray irradiation unit. generating a second composite data set by combining the data set and the first interpolated data set;
9. The X-ray CT system according to claim 8 , wherein said reconstruction unit reconstructs an image using said first synthetic data set and said second synthetic data set. 3. The data processing unit generates the first synthetic data set and the second synthetic data set by weighting such that the proportions of the first projection data set and the second projection data set are high. 9. The X-ray CT system according to 4 or 9 . A processing program using a projection data set acquired for each rotational position by periodically changing the energy of X-rays during one rotation around an object,
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing function for executing processing including correction processing according to the difference in the amount of transmission between the first energy X-rays and the second energy X-rays for at least one of them;
a plurality of projection data sets including a first projection data set and a second projection data set after the processing is performed on at least one of the plurality of first projection data sets and the plurality of second projection data sets; a reconstruction function for reconstructing an image based on a synthetic dataset generated based on the projection dataset;
A processing program for realizing on a computer. A processing program using a projection data set acquired for each rotational position by periodically changing the energy of X-rays during one rotation around an object,
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing function for executing processing including correction processing according to the difference in the amount of transmission between the first energy X-rays and the second energy X-rays for at least one of them;
a reconstruction function for reconstructing an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set;
is realized on a computer,
The data processing function is configured to reduce a difference in transmission between the first energy x-rays and the second energy x-rays to reduce the difference in transmission between the plurality of first projection data sets or the plurality of second projection data sets. A processing program for executing a correction process for multiplying two projection data sets by a coefficient based on the difference in the amount of transmission. A processing program using a projection data set acquired for each rotational position by periodically changing the energy of X-rays during one rotation around an object,
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing function for executing processing including correction processing according to the difference in the amount of transmission between the first energy X-rays and the second energy X-rays for at least one of them;
a reconstruction function for reconstructing an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set;
is realized on a computer,
The data processing function performs, for the plurality of first projection data sets, the Correction by multiplying the plurality of second projection data sets by a coefficient based on the difference between the first energy and the third energy, and multiplying the plurality of second projection data sets by a coefficient based on the difference between the second energy and the third energy. A processing program that performs processing. A processing program using a projection data set acquired for each rotational position by periodically changing the energy of X-rays during one rotation around an object,
Among a plurality of first projection data sets acquired when X-rays of a first energy are irradiated and a plurality of second projection data sets acquired when X-rays of a second energy are irradiated a data processing function for executing processing including correction processing according to the difference in the amount of transmission between the first energy X-rays and the second energy X-rays for at least one of them;
a reconstruction function for reconstructing an image based on a composite data set generated based on a plurality of projection data sets including the processed projection data set;
is realized on a computer,
The process generates a plurality of first interpolated data sets corresponding to rotational positions not exposed to the first energy based on the plurality of first projection data sets, and the plurality of second projection data sets. generating a plurality of second interpolated data sets corresponding to rotational positions not exposed to the second energy based on
The data processing function generates a first combined data set by synthesizing a first projection data set and a second interpolation data set corresponding to the rotational position of the X-ray irradiator, and generating second projection data corresponding to the rotational position. generating a second composite data set that combines the set and the first interpolated data set;
A processing program, wherein the reconstruction function reconstructs an image using the first synthetic data set and the second synthetic data set.

Images