X-ray CT apparatus, setting method, and recording medium

Abstract

To appropriately set a lower limit height related to a moving range of a scanner.SOLUTION: An X-ray CT apparatus includes a scanner, a stand, a detection unit, and a setting unit. The scanner performs X-ray CT imaging of a subject. The stand supports the scanner to be movable in a vertical direction. The detector detects a height of a thigh of the subject from a floor surface. The setting unit sets a lower limit height related to a movement range of the scanner in the vertical direction based on the detected height.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray CT apparatus, a setting method, and a setting program. [Background technology]

[0002] X-ray CT (Computed Tomography) devices can capture images of subjects in various postures. X-ray CT devices can capture images of subjects in a standing or sitting position by moving a horizontally installed scanner vertically.

[0003] In a conventional X-ray CT device, when imaging a subject in a seated position (sitting position), the lower limit height of the scanner's movement range is set to a predetermined value regardless of the subject's physique (size). In this case, depending on the subject's physique, the scanner may not be able to image the subject's region of interest (see FIG. 9). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-121925 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to appropriately set the lower limit height of the scanner's movement range. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of the configurations shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] An X-ray CT apparatus according to an embodiment includes a scanner, a stand, a detector, and a setting unit. The scanner performs X-ray CT imaging of a subject. The stand supports the scanner so that it can move in a vertical direction. The detector detects the height of the subject's thigh from a floor. The setting unit sets a lower limit height for the scanner's movement range in the vertical direction based on the detected height. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing the overall configuration of an X-ray CT apparatus according to this embodiment. [Figure 2] FIG. 4 is a flowchart showing a first examination procedure for X-ray CT imaging according to the present embodiment. [Figure 3] FIG. 10 is an explanatory diagram showing a first method for detecting thigh height according to the first inspection procedure. [Figure 4] FIG. 10 is an explanatory diagram showing a second method for detecting thigh height according to the first inspection procedure. [Figure 5] FIG. 10 is a flowchart showing a process for setting a lower limit height according to the first inspection procedure. [Figure 6] FIG. 10 is an explanatory diagram showing a method for setting a lower limit height according to the first inspection procedure. [Figure 7] FIG. 10 is a flowchart showing a second examination procedure for X-ray CT imaging according to the present embodiment. [Figure 8] FIG. 10 is an explanatory diagram showing a method for detecting thigh height according to the second examination procedure. [Figure 9] FIG. 10 is an explanatory diagram showing a method for setting a lower limit height according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present embodiment will be described with reference to the drawings. Parts with the same reference numerals are considered to be the same, and redundant description will be omitted where appropriate.

[0009] 1 is a schematic diagram showing the overall configuration of an X-ray CT apparatus 1 according to this embodiment. The X-ray CT apparatus 1 is an apparatus for performing X-ray CT imaging of a subject (or a patient). The X-ray CT apparatus 1 includes an imaging module 2 and a control module 3.

[0010] The imaging module 2 is a module for performing X-ray CT imaging of a subject. The imaging module 2 is installed in a CT examination room. The imaging module 2 includes a scanner 21, two stands 22, a rotation drive device 23, and a stand drive device 24.

[0011] The control module 3 is a module (or console) that controls the imaging module 2. The control module 3 is installed in a control room adjacent to the CT examination room. The control module 3 includes, as its components, a processing circuit 31, a memory circuit 32, an input circuit 33, a display circuit 34, and a communication circuit 35. The components are connected to each other via a bus so that they can communicate with each other.

[0012] (Imaging Module 2) The scanner 21 is a cylindrical housing that houses an imaging mechanism for performing X-ray CT imaging of a subject. The scanner 21 has a cylindrical opening OP in the center. The central axis AX of the opening OP intersects perpendicularly (i.e., vertically) with the floor surface FL. The scanner 21 includes an X-ray tube 211, a high-voltage generator 212, an X-ray detector 213, a DAS 214, and a rotating frame 215.

[0013] The X-ray tube 211 is a device that generates X-rays. The X-ray tube 211 generates X-rays based on a high voltage supplied from a high voltage generator 212. The X-ray tube 211 irradiates the generated X-rays onto a subject.

[0014] The high voltage generator 212 is a device that generates a high voltage and supplies the generated high voltage to the X-ray tube 211.

[0015] The X-ray detector 213 is a device that detects X-rays. The X-ray detector 213 generates an electrical signal corresponding to the energy of X-ray photons that have passed through the subject and are incident thereon. The X-ray detector 213 outputs the generated electrical signal to the DAS 214. The X-ray detector 213 may be an energy integration type or a photon counting type.

[0016] The DAS 214 is a system that collects projection data. The DAS 214 integrates the electrical signal input from the energy-integrating X-ray detector 213 over a predetermined time period to collect projection data. The DAS 214 counts the electrical signal input from the photon-counting X-ray detector 213 for each energy bin of X-ray photons to collect projection data. The DAS 214 outputs the collected projection data to the processing circuit 31 of the control module 3. DAS is an abbreviation for Data Acquisition System.

[0017] The rotating frame 215 is an annular frame that rotates while mounting an imaging mechanism. The rotating frame 215 mounts the X-ray tube 211, the high-voltage generator 212, the X-ray detector 213, and the DAS 214. The rotating frame 215 mounts the X-ray tube 211 and the X-ray detector 213 symmetrically about the central axis AX of the aperture OP. The rotating frame 215 rotates about the central axis AX of the aperture OP based on power supplied from the rotation drive device 23.

[0018] The stand 22 is a support that supports the scanner 21 so that it can move in the vertical direction. The stand 22 is installed on the floor surface FL. The two stands 22 hold both sides of the scanner 21 from the outside (double-supported structure). Alternatively, one stand 22 may hold one side of the scanner 21 from the outside (cantilevered structure). The stand 22 moves the scanner 21 in the vertical direction based on power supplied from the stand driving device 24.

[0019] The rotation drive device 23 is a device that generates power for rotating the rotating frame 215. The rotation drive device 23 generates power under the control of the processing circuit 31 of the control module 3. The rotation drive device 23 supplies the generated power to the rotating frame 215. The rotation drive device 23 may tilt the central axis AX of the opening OP about an axis parallel to the floor surface FL (i.e., a horizontal axis).

[0020] The stand driving device 24 is a device that generates power for the stand 22. The stand driving device 24 generates power in accordance with the control of the processing circuit 31 of the control module 3. The stand driving device 24 supplies the generated power to the stand 22.

[0021] (Control Module 3) The processing circuit 31 is a circuit that comprehensively controls each component of the control module 3. The processing circuit 31 has at least one processor. The processor refers to circuits such as a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (PLD). The programmable logic device refers to circuits such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA).

[0022] If the processor is a CPU, the CPU reads and executes each program stored in the storage circuitry 32 to realize each function. If the processor is an ASIC, each function is incorporated as a logic circuit within the ASIC. The processor may be configured as a single circuit or may be configured by combining multiple circuits. The processor realizes the following functions: a detection function 311, a setting function 312, an imaging control function 313, a lock control function 314, and a system control function 315.

[0023] The detection function 311 is a function for performing various detections. The detection function 311 detects the thigh height TH from the floor surface FL of the subject's thigh. The detection function 311 detects the scanner height SH from the floor surface FL of the scanner 21. The thigh height TH may be the height of the knee or the upper part of the thigh. The scanner height SH may be the height of the bottom surface of the scanner 21.

[0024] The setting function 312 is a function for performing various settings. The setting function 312 sets a lower limit height LH related to the movement range (or stroke) of the scanner 21 in the vertical direction based on the thigh height TH detected by the detection function 311.

[0025] The imaging control function 313 is a function that performs various imaging controls. The imaging control function 313 controls the imaging module 2 so that X-ray CT imaging is performed in accordance with predetermined imaging conditions. The imaging control function 313 reconstructs CT image data based on the projection data from the DAS 214. The imaging control function 313 outputs the reconstructed CT image data to the display circuitry 34.

[0026] The imaging control function 313 may perform positioning imaging on the subject. For example, the imaging control function 313 irradiates the subject with X-rays from the X-ray tube 211 at a lower dose than in the main imaging while moving the scanner 21 in the vertical direction with the X-ray tube 211 fixed at a predetermined rotation angle. The imaging control function 313 generates positioning image data for the subject based on the projection data obtained by this irradiation.

[0027] The lock control function 314 is a function that performs various lock controls. When the thigh height TH and the scanner height SH detected by the detection function 311 are equal to or smaller than a predetermined value, the lock control function 314 locks the movement of the scanner 21.

[0028] The system control function 315 is a function that comprehensively controls each component of the control module 3. The system control function 315 provides an operating system (OS) that enables the processing circuit 31 to realize each function.

[0029] The memory circuitry 32 is a circuit that stores various types of data. The memory circuitry 32 is configured with a magnetic disk, a semiconductor memory, etc. The memory circuitry 32 stores various programs executed by the processing circuitry 31. The memory circuitry 32 stores various types of image data generated by the processing circuitry 31.

[0030] The input circuitry 33 is a circuit that accepts input operations by an operator. The input circuitry 33 is composed of a mouse, a keyboard, buttons, switches, a trackball, a touch panel, etc. The input circuitry 33 converts the input operations by the operator into electrical signals and outputs these electrical signals to the processing circuitry 31.

[0031] The display circuitry 34 is a circuit that displays various images. The display circuitry 34 is configured with a liquid crystal display, an organic EL (Electro-luminescence) display, or the like. The display circuitry 34 displays a CT image based on the CT image data reconstructed by the processing circuitry 31. The display circuitry 34 displays a GUI (Graphical User Interface) for receiving input operations by the operator. The display circuitry 34 may also have the function of the input circuitry 33.

[0032] The communication circuitry 35 is a circuit for communicating various types of data. The communication circuitry 35 communicates CT image data based on the DICOM (Digital Imaging and Communication in Medicine) standard. The communication circuitry 35 may be connected to an external device via a communication network.

[0033] 2 is a flow chart showing a first examination procedure for X-ray CT imaging according to this embodiment. According to the first examination procedure, a medical technician has a subject assume a seated position and fix the subject in a predetermined position. The X-ray CT apparatus 1 detects the height TH of the subject's thighs using a detection device.

[0034] (Step S1A) First, the laboratory technician sets up a chair. Specifically, the laboratory technician sets up the chair directly below the opening OP of the scanner 21. The chair may be a wheelchair or a stool.

[0035] (Step S2A) Next, the laboratory technician seats the subject. Specifically, the laboratory technician seats the subject on the chair set up in step S1A. The laboratory technician may adjust the position of the subject seated on the chair. In this way, the laboratory technician fixes the subject in a seated position in a predetermined position.

[0036] (Step S3A) Subsequently, the X-ray CT apparatus 1 detects the thigh height TH. Specifically, the detection function 311 detects the thigh height TH of the subject in the state of step S2A based on the detection results (e.g., captured image, distance information, position information) from the detection devices (e.g., cameras, distance sensors, position sensors) (see FIGS. 3 and 4).

[0037] (Step S4A) Subsequently, the X-ray CT apparatus 1 performs processing for setting the lower limit height LH. Specifically, the X-ray CT apparatus 1 sets the lower limit height LH related to the movement range of the scanner 21 based on the thigh height TH detected in step S3A (see FIG. 5).

[0038] (Step S5A) Subsequently, the X-ray CT apparatus 1 determines an imageable area of ​​the subject. Specifically, the imaging control function 313 determines an imageable area of ​​the subject in the state of step S2A based on the lower limit height LH set in step S4A (see FIG. 6).

[0039] The imageable area is a spatial area occupied by the aperture OP of the scanner 21. The imageable area moves along with the movement of the scanner 21. The imageable area of ​​the subject is an imageable area that overlaps with the spatial area occupied by the subject.

[0040] (Step S6A) Finally, the X-ray CT apparatus 1 performs actual imaging. Specifically, the imaging control function 313 performs X-ray CT imaging of the region of interest included in the imageable region of the subject determined in step S5A with a predetermined dose. The imaging control function 313 reconstructs CT image data related to the imaged region of interest, and displays a CT image based on the reconstructed CT image data on the display circuitry 34.

[0041] FIG. 3 is an explanatory diagram showing a first detection method for the thigh height TH according to the first examination procedure. In the first detection method, a camera 51 is used as a detection device. The camera 51 is installed in a position relative to a chair C (particularly a subject carrier) installed on a floor surface FL so as to be able to photograph the thigh T of a subject S seated on the chair C. The camera 51 may be installed in front of the subject S or on a wall surface of the CT examination room. The camera 51 may photograph the range from the top surface of the scanner 21 to the floor surface FL. A medical technician may carry the camera 51 to photograph the thigh T.

[0042] The camera 51 captures an image of the thigh T. The detection function 311 analyzes the image captured by the camera 51 and detects the height TH of the thigh T from the floor FL. A known technique may be applied to the image analysis.

[0043] 4A and 4B are explanatory diagrams showing a second method for detecting thigh height TH according to the first examination procedure. In the second detection method, a sensor (e.g., an optical sensor, an ultrasonic sensor, or a magnetic sensor) is used as a detection device. In FIG. 4A, a distance sensor 52 is used as the sensor. In FIG. 4B, a position sensor 53 is used as the sensor.

[0044] 4(A), the distance sensor 52 is installed on the lower surface of the scanner 21 (i.e., the surface facing the thigh T). The distance sensor 52 may be installed directly above the thigh T, or may be installed on a flared surface (inclined surface) that is continuous with the lower surface of the scanner 21.

[0045] Distance sensor 52 measures distance D1 between the underside of scanner 21 and thigh T, and measures distance D2 between the underside of scanner 21 and floor FL. Detection function 311 detects the difference (D2-D1) between the two distances D1 and D2 measured by distance sensor 52 as the height TH of thigh T from floor FL. That is, detection function 311 detects thigh height TH based on the distance information from distance sensor 52.

[0046] As shown in Fig. 4(B), the position sensor 53 is installed on a member included in the chair C and located near the thigh T. The member may be an armrest on which the subject S places his or her elbow.

[0047] The position sensor 53 acquires the height of the position sensor 53 itself from the floor surface FL. The detection function 311 estimates that the height of the position sensor 53 is the same as the height of the thigh T, and detects the height TH of the thigh T from the floor surface FL. That is, the detection function 311 detects the thigh height TH based on the position information (especially the height information) from the position sensor 53.

[0048] 5 is a flow chart showing the process of setting the lower limit height LH according to the first examination procedure. According to this setting process, the X-ray CT apparatus 1 lowers the scanner 21 so as to approach the thigh T of the subject S, and sets the lower limit height LH according to the movement range of the scanner 21.

[0049] (Step S41A) Following step S3A, the X-ray CT apparatus 1 lowers the scanner 21. Specifically, the imaging control function 313 (or the setting function 312) controls the stand driving device 24 to lower the scanner 21.

[0050] The imaging control function 313 may cause the scanner 21 to perform X-ray CT imaging (particularly positioning imaging) at a predetermined dose while the scanner 21 is being lowered. The imaging control function 313 reconstructs CT image data obtained by the X-ray CT imaging at the predetermined dose, and displays a CT image based on the reconstructed CT image data on the display circuitry 34. By observing the displayed CT image, the operator can determine the imaging area of ​​the subject before the actual imaging (step S6A).

[0051] (Step S42A) Next, the X-ray CT apparatus 1 detects the scanner height SH. Specifically, the detection function 311 detects the height SH of the scanner 21 from the floor surface FL, for the scanner 21 that was lowered in step S41A. The detection function 311 may detect the scanner height SH based on the detection result from the detection device, similar to step S3A.

[0052] (Step S43A) Next, the X-ray CT apparatus 1 determines whether or not the distance D1 is less than a predetermined value (distance D1<predetermined value). Specifically, the lock control function 314 uses the thigh height TH detected in step S3A and the scanner height SH detected in step S42A. The lock control function 314 determines whether or not the distance D1 between the thigh height TH and the scanner height SH is less than a predetermined value. The predetermined value may be set to any value by the operator. If the distance D1 is less than the predetermined value (step S43A-YES), the process proceeds to step S44A. Conversely, if the distance D1 is equal to or greater than the predetermined value (step S43A-NO), the process proceeds to step S45A.

[0053] (Step S44A) If the distance D1 is less than a predetermined value, the X-ray CT apparatus 1 locks the lowering of the scanner 21. Specifically, the lock control function 314 locks the lowering of the scanner 21 by controlling the stand driving device 24. The lock control function 314 may lock the lowering of the scanner 21 by activating an interlock mechanism mounted on the scanner 21 or the stand 22. After step S44A, the process proceeds to step S46A.

[0054] (Step S45A) If the distance D1 is equal to or greater than the predetermined value, the X-ray CT apparatus 1 determines whether the scanner height SH is equal to the clearance height MH (scanner height SH = clearance height MH). The clearance height MH is the height obtained by adding a predetermined clearance (margin) to the thigh height TH detected in step S3A. The clearance may be set by the operator to any value (e.g., a value smaller than the predetermined value of the distance D1). If the scanner height SH is equal to the clearance height MH (YES in step S45A), the process proceeds to step S46A. This case can also be expressed as a case where the imaging control function 313 has lowered the scanner 21 until it reaches the clearance height MH. Conversely, if the scanner height SH is not equal to the clearance height MH (NO in step S45A), the process returns to step S41A.

[0055] (Step S46A) Next, the X-ray CT apparatus 1 sets the lower limit height LH. If the lowering of the scanner 21 is locked in step S44A, the setting function 312 sets the height SH of the locked scanner 21 as the lower limit height LH (SH = LH). If the scanner height SH is equal to the clearance height MH in step S45A, the setting function 312 sets the scanner height SH as the lower limit height LH (SH = MH, LH). After step S46A, the process proceeds to step S5A (see FIG. 6).

[0056] 6A and 6B are explanatory diagrams showing a method for setting the lower limit height LH in the first inspection procedure. Fig. 6A shows a case where the lowering of the scanner 21 is locked in step S44A. Fig. 6B shows a case where the scanner height SH is equal to the clearance height MH in step S45A.

[0057] As shown in FIG. 6(A), the scanner height SH is equal to the lower limit height LH (SH = LH). The height from the floor surface FL increases in the order of the thigh height TH, the clearance height MH, and the scanner height SH (TH < MH < SH). The imaging possible region of the subject S is the range from the top of the head to the upper half of the lung field.

[0058] As shown in FIG. 6(B), the scanner height SH is equal to the clearance height MH and the lower limit height LH (SH = MH, LH). The height from the floor surface FL increases in the order of the thigh height TH and the scanner height SH (TH < SH). The imaging possible region of the subject S is the range from the top of the head to the entire lung field.

[0059] FIG. 7 is a flowchart showing a second inspection procedure for X-ray CT imaging according to the present embodiment. According to the second inspection procedure, the technician makes the subject take a sitting position and fixes the subject at a predetermined position. The X-ray CT apparatus 1 detects the thigh height TH of the subject based on the physical information of the subject (or the seat surface height of the chair).

[0060] (Step S1B) First, the technician installs a chair. Specifically, the technician installs the chair directly below the opening OP of the scanner 21. Step S1B is the same as step S1A.

[0061] (Step S2B) Next, the technician seats the subject. Specifically, the technician seats the subject on the chair installed in step S1B. Step S2B is the same as step S2A.

[0062] (Step S3B) Subsequently, the technician inputs physical information or the seat surface height. Specifically, the technician inputs the physical information (e.g., height, weight) of the subject in the state of step S2B for the subject. Alternatively, the technician inputs the seat surface height of the chair on which the subject is seated. The technician inputs the physical information or the seat surface height through the input circuit 33. Note that the technician may input the name of the subject (or the model number of the chair).

[0063] (Step S4B) Subsequently, the X-ray CT apparatus 1 detects the thigh height TH. Specifically, the detection function 311 detects the thigh height TH based on the physique information or the seat height input in step S3B (see FIG. 8).

[0064] (Step S5B) Subsequently, the X-ray CT apparatus 1 performs processing for setting the lower limit height TH. Specifically, the X-ray CT apparatus 1 sets the lower limit height LH related to the movement range of the scanner 21 based on the thigh height TH detected in step S4B. Step S5B is similar to step S4A.

[0065] (Step S6B) Next, the X-ray CT apparatus 1 determines an imageable area of ​​the subject. Specifically, the imaging control function 313 determines an imageable area of ​​the subject in the state of step S2B based on the lower limit height LH set in step S5B. Step S6B is similar to step S5A.

[0066] (Step S7B) Finally, the X-ray CT apparatus 1 performs the actual imaging. Specifically, the imaging control function 313 performs X-ray CT imaging of the region of interest included in the imageable region of the subject determined in step S6B with a predetermined dose. Step S7B is similar to step S6A.

[0067] 8A and 8B are explanatory diagrams showing a method for detecting thigh height TH according to the second examination procedure. Fig. 8A shows a height table 800A. Fig. 8B shows a seat height table 800B. The height table 800A and the seat height table 800B are stored in the memory circuitry 32.

[0068] As shown in FIG. 8A, height table 800A is a table that associates height with thigh height TH for each subject. Specifically, for subjects S1 to S9, heights of 150.0 cm to 190.0 cm are associated with thigh heights TH1 to TH9. Subjects S1 to S9 may also be names of the subjects. The subjects may be actual subjects imaged by the X-ray CT apparatus 1, or may be statistically estimated virtual subjects. In other words, height table 800A may contain data related to actual subjects imaged by the X-ray CT apparatus 1, or may contain data related to virtual subjects not imaged by the X-ray CT apparatus 1.

[0069] The detection function 311 identifies a record (or row) in the height table 800A that is most similar to the height of the subject input in step S3B. The detection function 311 detects the thigh height TH associated with the identified record. In this way, the detection function 311 uses the height table 800A to detect the thigh height TH associated with the specific subject.

[0070] As shown in FIG. 8(B), seat height table 800B is a table that associates seat height with thigh height TH for each chair. Specifically, for chairs C1 to C5, seat heights of 38 cm to 46 cm are associated with thigh heights TH1 to TH5. Chairs C1 to C5 may be the model numbers (names) of the chairs. Thigh heights TH1 to TH5 may be the thigh heights TH when an average adult sits on chairs C1 to C5. Thigh heights TH1 to TH5 may be the height obtained by adding a predetermined value (e.g., 10 cm) to the seat height.

[0071] The detection function 311 identifies a record (or row) in the seat height table 800B that is most similar to the seat height of the chair input in step S3B. The detection function 311 detects the thigh height TH associated with the identified record. In this way, the detection function 311 uses the seat height table 800B to detect the thigh height TH associated with the subject seated on the specific chair.

[0072] If the name of the subject is input in step S3B, the detection function 311 may identify a record in the height table 800A that matches the input name. If the model number of the chair is input in step S3B, the detection function 311 may identify a record in the seat height table 800B that matches the input model number. The detection function 311 may detect the thigh height TH associated with the identified record.

[0073] According to the present embodiment described above, the X-ray CT apparatus 1 detects the thigh height TH of the subject when the subject is seated on a chair (sitting posture). The X-ray CT apparatus 1 sets the lower limit height LH for the movement range of the scanner 21 based on the detected thigh height TH.

[0074] Therefore, the X-ray CT apparatus 1 can appropriately set the lower limit height LH for each subject based on the physique of each subject. By setting the lower limit height LH to be greater than the thigh height TH of the subject, the X-ray CT apparatus 1 can prevent the scanner 21 from pinching the subject's thigh. In particular, by setting the lower limit height LH to be slightly greater than the thigh height TH of the subject, the X-ray CT apparatus 1 can bring the scanner 21 as close as possible to the subject's thigh. At this time, the imageable area of ​​the subject (or the movement range of the scanner 21) is maximized, improving the reliability with which the scanner 21 can image the subject's region of interest.

[0075] Fig. 9 is an explanatory diagram showing a method for setting the lower limit height LH according to the prior art. According to the prior art, the X-ray CT device 1 sets the lower limit height LH related to the movement range of the scanner 21 to a predetermined value regardless of the physique of the subject S. The X-ray CT device 1 images the lung field L of the subject S as the region of interest. Fig. 9(A) shows a case where the subject S has a relatively small physique. Fig. 9(B) shows a case where the subject S has a relatively large physique.

[0076] 9(A), the lower limit height LH is set to half the height of the lung field L of the subject S. In this case, the X-ray CT device 1 can image the upper half of the lung field L, but cannot image the lower half of the lung field L (i.e., the entire lung field L).

[0077] As shown in Fig. 9(B), the lower limit height LH is set to a height lower than the lower end of the lung field L of the subject S. In this case, the X-ray CT device 1 can image the entire lung field L. As in the example using Figs. 9(A) and (B), in imaging using conventional technology in which the entire lung field is the region of interest, depending on the physique of the subject, it may be possible to image the entire lung field or a part of the lung field may not be imaged.

[0078] According to this embodiment, the X-ray CT apparatus 1 detects the thigh height TH of the subject S and sets the lower limit height LH that is greater than the detected thigh height TH. When the subject S has a relatively small build (see FIG. 9(A)), the X-ray CT apparatus 1 can set the lower limit height LH to a height that is lower than the lower end of the lung field L. Therefore, the X-ray CT apparatus 1 can image the entire lung field L without omission, regardless of the build of the subject S.

[0079] (Variation) The detection device in step S3A may be used in the actual imaging in step S6A. Specifically, the detection device may activate an interlock mechanism that locks the movement of the scanner 21. If the scanner 21 gets too close to the subject's thigh, the detection device activates the interlock mechanism to lock the movement of the scanner 21. In this way, the detection device can prevent the scanner 21 from pinching the subject's thigh.

[0080] The detection device in step S3A may be disabled if the scanner 21 does not interfere with (or contact) the subject and the chair, and the scanner 21 can move within its maximum range of motion because the disabled detection device does not activate the interlock mechanism.

[0081] In the above-described embodiment, the detection function detects the height of the subject's thigh from the floor, and the setting function sets the lower limit height of the scanner's vertical movement range based on the detected height. However, the detection function may detect the positional relationship between the subject's thigh and the scanner by means other than the above example, and the setting function may set the lower limit height of the scanner's vertical movement range based on the positional relationship. For example, the detection function may detect the distance between the scanner's bottom surface and the subject's thigh, and the setting function may set the lower limit height of the scanner's vertical movement range based on the distance.

[0082] According to at least one of the embodiments described above, the lower limit height of the scanner movement range can be appropriately set.

[0083] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0084] 1 X-ray CT device 2. Shooting module 3 Control Module 21 Scanner 22 Stand 23 Rotational drive unit 24 Stand drive unit 31 Processing circuit 32 Memory circuit 33 Input circuit 34 Display circuit 35 Communication Circuit 51 Camera 52 Distance Sensor 53 Position Sensor 211 X-ray tube 212 High Voltage Generator 213 X-ray detector 214 DAS 215 Rotating Frame 311 Detection Function 312 Setting Function 313 Shooting control function 314 Lock Control Function 315 System Control Functions 800A Height Table 800B seat height table AX center axis C. Chair D1,D2 distance FL floor surface L lung field LH Lower limit height MH Free height OP Opening S subject SH Scanner height T Thigh TH Thigh height

Claims

1. a scanner for taking an X-ray CT image of a subject; a stand that supports the scanner so that the scanner can move in a vertical direction; a detection unit that detects the height of the subject's thigh from a floor surface; a setting unit that sets a lower limit height for a movement range of the scanner in the vertical direction based on the detected height; An X-ray CT device comprising:

2. the detection unit detects the height based on a detection result from a detection device. The X-ray CT apparatus according to claim 1.

3. the detection device is a camera; The detection unit detects the height based on a photographed image of the thigh taken by the camera. The X-ray CT apparatus according to claim 2.

4. the detection device is a distance sensor; the scanner has the distance sensor on a surface facing the thigh; The detection unit detects the height based on distance information from the distance sensor. The X-ray CT apparatus according to claim 2.

5. the detection device is a position sensor of a chair on which the subject is seated, The detection unit detects the height based on position information from the position sensor. The X-ray CT apparatus according to claim 2.

6. the detection unit further detects a height of the scanner from the floor surface based on the detection result from the detection device; a lock control that locks movement of the scanner when a distance between the detected height of the thigh and the detected height of the scanner is less than a predetermined value. The X-ray CT apparatus according to claim 2.

7. the detection unit detects the height based on physique information of the subject. The X-ray CT apparatus according to claim 1.

8. the detection unit detects the height of the subject based on a table in which the physique information is associated with the height of the thigh from a floor surface. The X-ray CT apparatus according to claim 7.

9. the detection unit detects the height based on a seat height of a chair on which the subject is seated. The X-ray CT apparatus according to claim 1 .

10. the detection unit detects the height of the subject based on a table in which the seat height and the height of the thigh from the floor are associated with each other. The X-ray CT apparatus according to claim 9.

11. the setting unit sets the lower limit height by lowering the scanner until it reaches a margin height obtained by adding a margin to the detected height. The X-ray CT apparatus according to claim 1 .

12. an imaging control unit that causes the scanner to perform X-ray CT imaging at a predetermined dose while the scanner is descending until it reaches the clearance height; The X-ray CT apparatus according to claim 11.

13. a scanner for taking an X-ray CT image of a subject; a stand that supports the scanner so that the scanner can move in a vertical direction; A setting method for an X-ray CT apparatus comprising: The computer Detecting the height of the subject's thigh from a floor surface; setting a lower limit height for a movement range of the scanner in the vertical direction based on the detected height; How to set it up.

14. a scanner for taking an X-ray CT image of a subject; a stand that supports the scanner so that the scanner can move in a vertical direction; A setting program for an X-ray CT apparatus comprising: On the computer, a detection function for detecting a height of the subject's thigh from a floor surface; a setting function for setting a lower limit height of a movement range of the scanner in the vertical direction based on the detected height; A configuration program that makes this possible.

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