JP6925799B2 - X-ray CT device - Google Patents

Description

Embodiments of the present invention relate to an X-ray CT apparatus.

When photographing a subject with an X-ray CT (Computed Tomography) apparatus, positioning imaging may be performed in advance to obtain a positioning image (scano image). The positioning image is generated based on the projection data obtained by fixing the X-ray tube at a predetermined position and irradiating the subject with X-rays while changing the relative positions of the subject and the X-ray tube. By using the positioning image, it is possible to more accurately position the slice position for the main scan and set the shooting conditions.

On the other hand, as an X-ray detector of an X-ray CT apparatus, a two-dimensional array type detector in which a plurality of rows of X-ray detection elements having a plurality of channels in the channel direction are arranged in a slice direction (z direction) has been used in recent years. It has come to be. However, even when this type of two-dimensional array type detector is used, when a positioning image is taken, a plurality of detection element trains continuous in the slice direction are often bundled and used as one slice width. .. Therefore, the resolution of the positioned image is significantly lower than that of the main scan image. Further, in positioning imaging, imaging is often performed while irradiating X-rays continuously in time. In this case, since the positioning imaging tends to take a long time, the tube current is lower than that of the main scan, but the exposure dose of the subject is increased.

Japanese Unexamined Patent Publication No. 2003-175029

An object to be solved by the present invention is to provide an X-ray CT apparatus capable of suppressing the exposure dose of a subject and generating a positioning image having high resolution.

In the X-ray CT apparatus according to the embodiment of the present invention, in order to solve the above-mentioned problems, an X-ray source that generates X-rays and a row of X-ray detection elements having a plurality of channels in the channel direction are arranged in the channel direction. A plurality of rows of X-ray detectors arranged in a row in the body axis direction of the subject orthogonal to the subject and an X-ray detector for detecting the X-ray transmitted through the subject, a pedestal provided with an opening in between, and the pedestal and the subject. Positioning imaging using pulsed X-rays while changing the relative position along the body axis direction with the drive unit for changing the relative position with the sample and the X-ray source fixed at a predetermined position. The X-ray source and the scan control unit that controls the drive unit are provided, and the scan control unit performs the positioning imaging while changing the relative position along the body axis direction. Is irradiated with pulsed X-rays and then repeatedly irradiated with pulsed X-rays when the relative position moves in the body axis direction by a predetermined distance shorter than the slice width from the reference irradiation position. It controls the source and the drive unit.

The block diagram which shows an example of the X-ray CT apparatus which concerns on one Embodiment of this invention. The figure for demonstrating the positional relationship between an X-ray tube and an X-ray detector, and the rotation center of an X-ray tube. A schematic block diagram showing an example of a function realized by a processor of a processing circuit. (A) is an explanatory diagram showing an example of the slice width Δa on the rotation center surface, and (b) is an explanatory diagram showing an example of the slice width Δb on the light receiving surface of the X-ray detection element. The figure for demonstrating the definition of the slice width and the X-ray beam width in the rotation center plane. The figure for demonstrating the method of irradiating the pulse X-ray for every X-ray beam width and taking a scanno image. FIG. 6 is a diagram for explaining a scanno image photographing method for irradiating pulse X-rays even when the slice width Δa is moved by half a distance in addition to the case shown in FIG. FIG. 5 is a flowchart showing an example of a procedure for generating a high-resolution positioning image while suppressing the exposure dose of a subject by a processing circuit of an X-ray CT apparatus. To explain a method of imaging a scan when pulse X-ray irradiation is performed at a position where a predetermined interpolation width is moved in the channel direction immediately after pulse X-ray irradiation when the relative position between the X-ray tube and the subject is changed. figure. The figure for demonstrating the scanno image photographing method in the case where the interpolation width in a scanning direction is half of a slice width, and the interpolation width in a channel direction is half of the center-to-center distance between detection elements along the channel direction. The figure for demonstrating the scanno image photographing method when the interpolation width in a scanning direction is 1/3 of a slice width, and the interpolation width in a channel direction is 1/3 of the center-to-center distance between detection elements along a channel direction. ..

An embodiment of the X-ray CT apparatus according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an example of an X-ray CT apparatus 10 according to an embodiment of the present invention.

The X-ray CT apparatus is a rotation / rotation (ROTATE / ROTATE) type in which an X-ray tube and a detector are integrated to rotate around a subject, and a large number of detection elements are arranged in an annular shape to form an X-ray. There are various types such as a fixed / rotating type in which only the tube rotates around the subject, and a type in which the position of the X-ray source is electronically moved on the target by deflecting the electron beam. However, the configuration shown in this embodiment is applicable to any type. In the type using an electron beam, it can be applied by appropriately reading the X-ray tube as an X-ray source. In the present embodiment, an example is shown in which the X-ray CT apparatus 10 is a rotation / rotation (ROTATE / ROTATE) type in which the X-ray tube and the X-ray detector are integrated and rotate around the subject O.

Further, in recent years, the commercialization of a so-called multi-tube type X-ray CT apparatus in which a plurality of pairs of an X-ray tube and an X-ray detector are mounted on a rotating ring has progressed, and the development of peripheral technologies thereof has progressed. The X-ray CT apparatus 10 according to the present embodiment can be applied to either a single-tube type or a multi-tube type. Here, an example in the case where the X-ray CT apparatus 10 is a single tube type will be described.

As shown in FIG. 1, the X-ray CT apparatus 10 has a pedestal 11, a sleeper apparatus 12, and a console 13.

The gantry 11 has a fixed pedestal 21 and a rotary pedestal 22. The fixed pedestal 21 is fixed to an installation surface such as a floor surface, and has a gantry control circuit 26, a data transmission device 27, and a drive circuit 28. The rotary pedestal 22 integrally holds the X-ray tube 31, the aperture 32, the X-ray detector 33, and the DAS (Data Acquisition System) 34, and rotates around the opening in the central portion. In the present embodiment, the direction parallel to the rotation center axis of the rotary base 22 is defined as the z-axis direction, the normal direction of the installation surface is defined as the y-axis direction, and the direction parallel to the installation surface is defined as the x-axis direction (FIG. 1). reference).

The X-ray tube 31 is controlled by the gantry control circuit 26, and a high voltage generated by a high-voltage power supply (not shown) of the fixed gantry 21 is supplied via, for example, a slip ring. The high-voltage power supply may be provided on the rotary stand 22.

The X-rays generated by the X-ray tube 31 are irradiated toward the subject O as fan beam X-rays or cone beam X-rays.

The aperture 32 is composed of, for example, a wedge filter, and is controlled by a gantry control circuit 26 to cover at least one irradiation range of X-rays emitted from the X-ray tube 31 in the slice direction (z direction, column direction) and the channel direction. adjust.

The X-ray detector 33 is composed of a plurality of X-ray detection elements (charge storage elements). This X-ray detection element (radiation detection element) detects X-rays irradiated from the X-ray tube 31 and transmitted through the subject O. The X-ray tube 31 and the X-ray detector 33 are supported by the rotary pedestal 22 so as to be opposite to each other with the subject O mounted on the sleeper device 12 in between.

As the X-ray detector 33, a so-called two-dimensional array type (multi-slice type) having a plurality of rows such as 320 rows in the slice direction and a plurality of X-ray detection elements in the channel direction can be used. In the case of the multi-slice type, a plurality of rows of X-ray detection elements having a plurality of channels in the channel direction can be used in the slice direction (z direction). Further, in the case of the two-dimensional array type, the X-ray detector 33 can be composed of a plurality of X-ray detection elements densely distributed in both the slice direction (z direction) and the channel direction.

In the following description, in the X-ray detector 33, the rows of X-ray detection elements having a plurality of channels in the channel direction are arranged in a plurality of rows in the body axis direction (slice direction, z direction) of the subject O orthogonal to the channel direction. An example of the case where it is configured is shown. Further, the X-ray CT apparatus 10 according to the present embodiment uses data of a part of elements (for example, 8 rows or 4 rows) of 320 rows in the channel direction in positioning imaging (scano imaging).

The DAS 34 receives analog signals output by a plurality of X-ray detection elements constituting the X-ray detector 33, and performs processes such as current-voltage conversion, amplification, and analog-digital conversion (AD conversion) on the signals. Then, the DAS 34 generates transmission data using these processed signals and transmits the transmission data to the console 13 via the data transmission device 27. The console 13 performs a reconstruction process based on the projection data included in the transmission data, and generates a reconstruction image.

FIG. 2 is a diagram for explaining the positional relationship between the X-ray tube 31 and the X-ray detector 33 and the rotation center of the X-ray tube 31.

The rotary pedestal 22 integrally holds the X-ray tube 31, the throttle 32, the X-ray detector 33, and the DAS 34, and is supported by the fixed pedestal 21. The rotating pedestal 22 is controlled by the pedestal control circuit 26 to rotate, so that the X-ray tube 31, the throttle 32, the X-ray detector 33, and the DAS 34 are integrally rotated around the rotation center of the X-ray tube 31. , Rotate around subject O. Further, the rotary pedestal 22 may be configured to be tiltable with respect to the fixed pedestal 21. Information on the current rotation speed of the rotary gantry 22, tilt operation, and current tilt angle information is given to the console 13 via the gantry control circuit 26.

The bed device 12 includes a base 36 installed on an installation surface such as a floor surface, a top plate 37 supported by the base 36, and a top plate driving device 38.

The top plate 37 is configured so that the subject O can be placed on it. The top plate drive device 38 is controlled by the drive circuit 28 to move the top plate 37 up and down in the y-axis direction (vertical direction). Further, the top plate drive device 38 is controlled by the drive circuit 28 to move the top plate 37 to the X-ray irradiation field of the opening in the central portion of the rotary base 22 along the z-axis direction (longitudinal direction of the top plate 37). Transfer. Further, the top plate drive device 38 is controlled by the drive circuit 28 to transfer the top plate 37 in the x-axis direction (horizontal direction of the top plate 37). Further, the top plate driving device 38 can be controlled by the driving circuit 28 to rotate the top plate 37 about each axis of the xyz axis. Information regarding the movement of the top plate 37 (movement speed and movement direction) and information on the current position are given to the console 13 via the top plate drive device 38 and the drive circuit 28.

The gantry control circuit 26 has at least a processor and a storage circuit. The gantry control circuit 26 is controlled by the console 13 and executes X-ray CT imaging of the subject O by controlling the gantry 11 according to a program stored in the storage circuit.

Although FIG. 1 shows an example in which the gantry control circuit 26 and the console 13 are connected by wire, the gantry control circuit 26 and the console 13 may be connected so as to be able to transmit and receive data via a network.

The data transmission device 27 performs parallel / serial conversion, electrical / optical / electrical conversion, and serial / parallel conversion on the transmission data output from the DAS 34. The data transmission device 27 includes, for example, a parallel / serial converter (not shown), an electric / optical / electric converter, and a serial / parallel converter (not shown). The multi-channel transmission data output from the DAS 34 is converted into time-series one-channel data by the parallel / serial converter provided on the rotary stand 22, and optical communication using the electric / optical / electric converter, etc. Is supplied to the serial / parallel converter provided on the fixed frame 21.

Subsequently, the transmission data of one channel is returned to the transmission data of a plurality of channels by the above-mentioned serial / parallel converter. The projection data of the plurality of channels obtained in time series is stored in the console 13 with the arrangement position information and rotation angle information of the radiation detection elements in the channel direction and the position information (imaging position) of the projection data in the slice direction as incidental information. ..

The data transmission method by the data transmission device 27 may be another method as long as data transmission between the DAS 34 provided on the rotary gantry 22 and the gantry control circuit 26 provided on the fixed gantry 21 is possible. For example, a device such as a slip ring may be used for data transmission by the data transmission device 27, or a method of non-contact transmission may be used.

The drive circuit 28 has at least a processor and a storage circuit. The drive circuit 28 is controlled by the console 13 and controls the top plate drive device 38 according to a program stored in the storage circuit. For example, the X-ray tube 31 fixed at a predetermined position in scanno imaging and the subject O The relative position is changed, for example, by moving the top plate 37 at a constant velocity. Further, when the drive circuit 28 is configured to be movable in the z-axis direction along a rail (not shown) provided on the installation surface, the drive circuit 28 is covered with an X-ray tube 31 fixed at a predetermined position in scanning photography. The relative position with respect to the sample O is changed by moving the gantry 11 along the rail at a constant velocity in the z-axis direction. Further, the drive circuit 28 may change the relative position between the X-ray tube 31 and the subject O by moving both the top plate 37 and the gantry 11.

On the other hand, the console 13 of the X-ray CT apparatus 10 is composed of, for example, a general personal computer or a workstation, and has an input circuit 41, a display 42, a storage circuit 43, and a processing circuit 44. The console 13 does not have to be provided independently, and a part of the configurations 41-44 of the console 13 may be provided in a distributed manner on the gantry 11.

The input circuit 41 is composed of general input devices such as a trackball, a switch button, a mouse, a keyboard, and a numeric keypad, and outputs an operation input signal corresponding to the user's operation to the processing circuit 44. For example, the user can set the shooting conditions for scanno shooting via the input circuit 41. In the present embodiment, the imaging conditions include information on the imaging target portion. Some or all of the shooting conditions may be set via the input circuit 41 or may be acquired via the network.

The display 42 is composed of a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display, and displays a real-time reconstructed image or the like under the control of a processing circuit 44.

The storage circuit 43 has a configuration including a recording medium that can be read by a processor, such as a magnetic or optical recording medium or a semiconductor memory. Some or all of the programs and data in these recording media may be configured to be downloaded by communication via an electronic network. The storage circuit 43 stores, for example, the projection data transmitted from the DAS 34, the scanno image generated by the processing circuit 44, and the like.

The processing circuit 44 is a processor that executes a process of generating a high-resolution positioning image while suppressing the exposure dose of the subject O by reading and executing the program stored in the storage circuit 43.

FIG. 3 is a schematic block diagram showing an example of a function realized by the processor of the processing circuit 44. As shown in FIG. 3, the processor of the processing circuit 44 realizes at least the X-ray control function 50, the condition acquisition function 51, the scan control function 52, and the image generation function 53. Each of these functions is stored in the storage circuit 43 in the form of a program.

The X-ray control function 50 is controlled by the scan control function 52 to output an X-ray control signal, and supplies a tube current and a tube voltage from a high-voltage power supply to the X-ray tube 31 at a predetermined timing via a gantry control circuit 26. Let me.

When the user instructs the start of scanno shooting via the input circuit 41, the condition acquisition function 51 acquires the shooting conditions if the shooting conditions are set.

The scan control function 52 positions the X-ray tube 31 by using pulsed X-rays while changing the relative position between the X-ray tube 31 and the subject O along the body axis direction in a state where the X-ray tube 31 is fixed at a predetermined position. The X-ray tube 31 is controlled and the drive circuit 28 is controlled via the X-ray control function 50 so as to perform imaging. Specifically, the scan control function 52 first emits pulsed X-rays at the reference irradiation position when performing positioning imaging while changing the relative positions of the X-ray tube 31 and the subject O along the body axis direction. After irradiation, the X-ray tube 31 and the drive circuit 28 are controlled so that pulse X-rays are repeatedly irradiated when the relative position moves in the body axis direction by a predetermined distance shorter than the slice width from the reference irradiation position. .. Further, the scan control function 52 may move in the channel direction and irradiate the pulse X-ray without waiting for the movement in the slice direction.

FIG. 4A is an explanatory diagram showing an example of the slice width Δa on the rotation center surface, and FIG. 4B is an explanatory diagram showing an example of the slice width Δb on the light receiving surface of the X-ray detection element. FIG. 4 shows an example in which eight rows of detection elements are used in scanno imaging. Further, FIG. 5 is a diagram for explaining the definitions of the slice width and the X-ray beam width in the rotation center plane.

As described above, the scan control function 52 repeats irradiating the pulse X-ray again when the relative position moves in the body axis direction by a predetermined distance shorter than the slice width from the reference irradiation position. FIG. 4 shows an example in which a predetermined distance shorter than the slice width is half the slice width. The scan control function 52 may track the change in the relative position between the X-ray tube 31 and the subject O on the rotation center surface (see FIG. 4A), or may be tracked on the light receiving surface of the detection element. Good (see FIG. 4 (b)).

When tracking the change in the relative position on the rotation center plane and performing X-ray irradiation when the slice width Δa is half the distance in the plane passing through the rotation center of the X-ray tube 31 and orthogonal to the X-ray irradiation axis, The X-ray beam at the center of rotation can be accurately shifted by a desired distance. In the following description, an example will be described in which the change in the relative position between the X-ray tube 31 and the subject O is tracked on the rotation center plane.

Conventionally, in scanning photography, for example, by using four rows of detection elements of 0.5 mm together, X-rays are continuously irradiated with a thick slice width such as 2 mm width, so that the slice width is 0.5 mm. The resolution of the scanno image is lower than that of the main scan image taken.

Therefore, as shown in FIGS. 4 and 5, the X-ray CT apparatus 10 according to the present embodiment has eight rows of 0.5 mm wide slice widths obtained for each 0.5 mm detection element row without bundling. Use a thin slice width, such as using it. Therefore, it is possible to obtain an image having a higher resolution than the conventional scanno image.

FIG. 6 is a diagram for explaining a method of irradiating pulse X-rays for each X-ray beam width to take a scanno image. Further, FIG. 7 is a diagram for explaining a scanno image photographing method for irradiating pulse X-rays even when the slice width Δa is moved by a half distance in addition to the case shown in FIG. Note that FIGS. 6 and 7 show an example in which scannographing is performed using four rows of 0.5 mm detection elements.

As shown in FIG. 6, the resolution of the scanno image can be increased by using a thin slice width. Further, as shown in FIG. 7, when shooting is performed even when the image is moved by a predetermined distance shorter than the slice width, a higher resolution image can be obtained by further dividing the thin slice width of 0.5 mm.

The image generation function 53 generates an image each time a pulse X-ray is irradiated and displays it on the display 42.

Next, an example of the operation of the X-ray CT apparatus 10 according to the present embodiment will be described.

FIG. 8 is a flowchart showing an example of a procedure for generating a high-resolution positioning image while suppressing the exposure dose of the subject O by the processing circuit 44 of the X-ray CT apparatus 10. In FIG. 8, reference numerals with numbers attached to S indicate each step of the flowchart. This procedure starts when the start of scanno shooting is instructed.

First, in step S1, the condition acquisition function 51 acquires the shooting conditions for scanno shooting. The shooting conditions include information on the part to be shot. If the shooting conditions are not set, this step S1 is omitted.

Next, in step S2, the scan control function 52 sets a required resolution based on the information of the imaging target portion included in the imaging conditions. Note that step S2 may be omitted.

For example, when a part such as the head that requires detailed observation is the object to be photographed, the image is often magnified and used at a high magnification. In the case of such an imaging target portion, it is preferable to set the required resolution high and narrow the interpolation width (increase the number of divisions) in the subsequent steps S3 and S4. On the other hand, if it is a part such as the abdomen that can be roughly observed, the required resolution may be set low.

Further, when the required resolution is set in step S2, it is advisable to set the allowable noise of the scanno image according to this resolution. Specifically, when the required resolution is set, the scan control function 52 may set the tube current of the X-ray tube 31 according to this resolution.

Next, in step S3, the scan control function 52 sets the interpolation width in the slice direction (see FIG. 7). This interpolation width may be, for example, a value obtained by dividing the slice width by a positive integer.

Next, in step S4, the scan control function 52 sets the interpolation width in the channel direction. The interpolation width may be a value obtained by dividing the distance between the centers of the detection elements along the channel direction by a positive integer.

Note that step S4 may be omitted. On the other hand, if the relative position of the X-ray tube 31 and the subject O may not be constantly changed and the image may be taken by so-called step-and-shoot, it is moved in the slice direction after the pulse X-ray irradiation. The pulse X-ray irradiation may be performed by moving the interpolation width only in the channel direction without moving the interpolation width.

FIG. 9 shows a scanno image imaging method in which pulse X-ray irradiation is performed at a position where a predetermined interpolation width is moved in the channel direction immediately after pulse X-ray irradiation when the relative positions of the X-ray tube 31 and the subject O are changed. It is a figure for demonstrating.

Even when the relative positions of the X-ray tube 31 and the subject O are constantly changing, the scan control function 52 immediately after the pulse X-ray irradiation at the reference irradiation position, without waiting for the movement in the slice direction. , The irradiation position may be moved by the interpolation width in the channel direction to perform pulse X-ray irradiation.

In this case, the relative positions of the X-ray tube 31 and the subject O slightly move in the slice direction while the irradiation position is moved in the channel direction by the interpolation width. Therefore, in this case, it is preferable to adopt a method capable of changing the irradiation position in the channel direction at high speed, for example, by moving the focal length of the X-ray by the FFS method (Flying Focal Spot method). If the focal position of the X-ray is moved by the FFS method immediately after the pulsed X-ray irradiation at the reference irradiation position, the reference irradiation position and the reference irradiation position in the slice direction are clearly shown by comparing the first and second times in FIG. Pulse X-ray irradiation can be performed by shifting the irradiation position in the channel direction by the interpolation width at substantially the same position.

Further, the method shown in FIG. 9 in which the focal position of the X-ray is moved by the FFS method immediately after the pulsed X-ray irradiation at the reference irradiation position and the interpolation method in the slice direction shown in FIG. 7 may be combined. .. In this case, first, pulse X-ray irradiation is performed at the reference irradiation position (see the first time in FIG. 9), and immediately the focal position of the X-ray is moved by the FFS method to perform pulse X-ray irradiation (see the second time in FIG. 9). .. Subsequently, pulse X-ray irradiation is performed when the distance is shorter than the slice width by a predetermined distance (see the second time in FIG. 7), and the focal position of the X-ray is immediately moved again by the FFS method to perform pulse X-ray irradiation. Then, when pulse X-ray irradiation is performed at all the interpolation positions within the slice width, the position where the relative position between the X-ray tube 31 and the subject O moves in the body axis direction by the X-ray beam width from the reference irradiation position is newly changed. The reference irradiation position may be set, and pulse X-ray irradiation may be performed at this new reference irradiation position (see the third time in FIG. 7).

FIG. 10 is a diagram for explaining a scanno image photographing method when the interpolation width in the scanning direction is half the slice width and the interpolation width in the channel direction is half the center-to-center distance between the detection elements along the channel direction. be. Further, FIG. 11 shows a scanno image photographing method in the case where the interpolation width in the scanning direction is 1/3 of the slice width and the interpolation width in the channel direction is 1/3 of the center-to-center distance between the detection elements along the channel direction. It is a figure for demonstrating.

As shown in FIGS. 10 and 11, when the relative position between the X-ray tube 31 and the subject O is continuously changed at a constant velocity, for example, and the relative position is moved by the interpolation width in the slice direction, it is set in the channel direction. The relative position between the X-ray tube 31 and the subject O may be moved in the channel direction by the amount of the interpolation width to irradiate the pulse X-ray. As a method of moving the relative position between the X-ray tube 31 and the subject O in the channel direction, for example, a method of moving the focal position of the X-ray by the FFS method, a method of moving the top plate 37 in the x-axis direction, and the like are used. Conceivable. Further, the interpolation width in the slice direction may be shorter than the slice width, and is not limited to the width obtained by dividing the slice width by a positive integer. That is, if pulse X-ray irradiation is performed at one or more interpolation positions that are shorter than the slice width from the reference irradiation position and pulse X-ray irradiation is performed at all interpolation positions within the slice width, the pulse X-ray irradiation is performed from the reference irradiation position. The position where the relative position between the X-ray tube 31 and the subject O moves in the body axis direction by the X-ray beam width is set as a new reference irradiation position, and pulse X-ray irradiation may be performed at this new reference irradiation position (Fig.). See the 3rd time of 7 etc.). Similarly, the interpolation width in the channel direction is not limited to the value obtained by dividing the center-to-center distance between the detection elements along the channel direction by a positive integer.

Next, in step S5, the scan control function 52 sets the imaging start position as the reference irradiation position and irradiates the pulse X-ray at the reference irradiation position to perform imaging.

Next, in step S6, when the scan control function 52 moves by the interpolation width set in the slice direction, it irradiates pulse X-rays and takes a picture. At this time, if the interpolation width is set in the channel direction, the scan control function 52 changes the relative positional relationship in the channel direction to perform shooting. The scan control function 52 keeps changing the relative positional relationship between the X-ray tube 31 and the subject O even during imaging.

Next, in step S7, the image generation function 53 generates an image based on the projection data obtained by pulse X-ray irradiation.

Next, in step S8, the scan control function 52 sets the tube current in the next pulse X-ray irradiation according to the numerical value related to the image quality of the generated image. As the numerical value related to the image quality, a value evaluated by evaluating the noise of the image as a standard deviation value, a value evaluated by spatial frequency analysis of the image resolution by Fourier transform, and the like can be used.

If the shooting is not completed at all the interpolation positions within the slice width (NO in step S9), the process returns to step S6. On the other hand, when the shooting is completed at all the interpolation positions within the slice width (YES in step S9), the scan control function 52 determines whether or not the shooting of the entire shooting range of the scanno shooting is completed.

If the entire imaging range of the scanno imaging has not yet been completed (NO in step S10), the scan control function 52 detects the X-ray beam width (for example, 0.5 mm slice width) from the previous reference position in step S11. Pulse X-ray photography is performed with the position where the relative position has moved in the slice direction by 4 mm in the case of 8 rows of instruments as a new reference irradiation position, and the process returns to step S6. At this time, if the relative position is moved in the channel direction, pulse X-ray imaging is performed with the position where the movement amount in the channel direction is returned to zero as a new reference irradiation position.

On the other hand, when the shooting of the entire shooting range of the scanno shooting is completed (step S10YES), the series of procedures is completed.

By the above procedure, it is possible to generate a high-resolution positioning image while suppressing the exposure dose of the subject O.

According to at least one embodiment described above, pulse X-rays can be taken with a thin slice width and can be taken at an interpolated position in the slice direction. Therefore, the exposure of the subject O is higher than that in the case of continuous X-rays. The dose can be suppressed and a high-resolution positioning image can be generated.

Note that pulse X-ray irradiation may be performed only when moving to a new reference irradiation position (step S11), and continuous X-ray irradiation may be performed from the reference irradiation position to the imaging at the last interpolation position within the same slice width. Even in this case, the Hiba dose of the subject can be sufficiently reduced as compared with the case where continuous X-ray irradiation is continuously performed.

The scan control function 52 of the processing circuit 44 in this embodiment is an example of a scan control unit within the scope of claims. Further, the drive circuit 28 in this embodiment is an example of a drive unit within the scope of claims.

In the above embodiment, the term "processor" refers to, for example, a dedicated or general-purpose CPU (Central Processing Unit), GPU (Graphics Processing Unit), or application specific integrated circuit (ASIC). It shall mean a circuit such as a programmable logic device (for example, a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and an FPGA). The processor realizes various functions by reading and executing a program stored in a storage medium.

Further, in the above embodiment, an example in which a single processor of the processing circuit realizes each function is shown, but a processing circuit is formed by combining a plurality of independent processors, and each processor realizes each function. May be good. When a plurality of processors are provided, the storage medium for storing the program may be provided individually for each processor, or one storage medium collectively stores the programs corresponding to the functions of all the processors. May be good.

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

10 ... X-ray CT device 11 ... Stand 31 ... X-ray tube 33 ... X-ray detector 52 ... Scan control function

Claims (8)

The X-ray source that generates X-rays and a plurality of rows of X-ray detection elements having a plurality of channels in the channel direction are arranged in a plurality of rows in the body axis direction of the subject orthogonal to the channel direction, and the subject has passed through the subject. An X-ray detector that detects X-rays, a pedestal provided with an opening in between, and
A drive unit for changing the relative position between the gantry and the subject,
With the X-ray source fixed at a predetermined position, the X-ray source and the driving unit are controlled so as to perform positioning imaging using pulsed X-rays while changing the relative position along the body axis direction. Scan control unit and
With
The scan control unit
When performing the positioning imaging while changing the relative position along the body axis direction, after irradiating the pulse X-ray, the relative position is the body axis by a predetermined distance shorter than the slice width from the reference irradiation position. The X-ray source and the driving unit are controlled so as to repeatedly irradiate pulsed X-rays when moving in a direction.
The scan control unit further
Immediately after irradiating the pulse X-ray at the reference irradiation position, or when the relative position moves in the body axis direction by the predetermined distance from the reference irradiation position, the relative position is moved in the channel direction to the X. Irradiation of pulsed X-rays is repeated by moving the line detection elements by a second predetermined distance shorter than the center-to-center distance along the channel direction.
X-ray CT device. The scan control unit
When pulsed X-rays are irradiated at all interpolation positions within the slice width, the relative position is a position moved in the body axis direction by the X-ray beam width from the reference irradiation position, and the relative position in the channel direction. The position where the movement of the position is returned to zero is set as the new reference irradiation position, and the pulse X-ray is irradiated at this new reference irradiation position.
The X-ray CT apparatus according to claim 1. The scan control unit
The relative position is changed in the channel direction by moving the focal position of the X-ray in the channel direction by the second predetermined distance.
The X-ray CT apparatus according to claim 1 or 2. The X-ray source that generates X-rays and a plurality of rows of X-ray detection elements having a plurality of channels in the channel direction are arranged in a plurality of rows in the body axis direction of the subject orthogonal to the channel direction, and the subject has passed through the subject. An X-ray detector that detects X-rays, a pedestal provided with an opening in between, and
A drive unit for changing the relative position between the gantry and the subject,
With the X-ray source fixed at a predetermined position, the X-ray source and the driving unit are controlled so as to perform positioning imaging using pulsed X-rays while changing the relative position along the body axis direction. Scan control unit and
With
The scan control unit
When performing the positioning imaging while changing the relative position along the body axis direction, after irradiating the pulse X-ray, the relative position is the body axis by a predetermined distance shorter than the slice width from the reference irradiation position. The X-ray source and the driving unit are controlled so as to repeatedly irradiate pulsed X-rays when moving in a direction.
The scan control unit further
The predetermined distance is set based on the information of the imaging target portion included in the imaging conditions of the positioning imaging.
X-ray CT device. The predetermined distance shorter than the slice width is the distance obtained by dividing the slice width by a predetermined positive integer.
The X-ray CT apparatus according to any one of claims 1 to 4. The predetermined distance is a distance in a plane that passes through the rotation center of the X-ray source and is orthogonal to the irradiation axis of the X-ray, or a distance in the light receiving surface of the X-ray detection element.
The X-ray CT apparatus according to any one of claims 1 to 5. The scan control unit
The tube current for irradiating the next pulse X-ray is set according to the numerical value related to the image quality of the image generated each time the pulse X-ray is irradiated.
The X-ray CT apparatus according to any one of claims 1 to 6. The scan control unit
The predetermined distance is set based on the information of the imaging target portion included in the imaging conditions of the positioning imaging.
The X-ray CT apparatus according to any one of claims 1 to 3.

Images