JP4430971B2 - X-ray CT apparatus and control method thereof - Google Patents

Description

  The present invention relates to an X-ray CT apparatus and a control method thereof, and more particularly to an X-ray CT apparatus including an imaging table with an intermediate support (IMS) that supports a top plate on which a subject is placed so as to be transportable. Therefore, it is preferable.

  In general, the imaging table of the X-ray CT apparatus is configured so that the height of the table can be adjusted. This makes it easy for the patient to get on and off, and allows the patient to be accurately placed in the boa of the scanning gantry. Can be transported. In particular, in an imaging table with an IMS, not only the top plate but also the IMS portion can be carried into the cavity, so that the subject can be transported to a deeper position within the cavity, thereby enabling a long scannable object in the direction of the subject body axis.・ Range is obtained. On the other hand, the scanning gantry of the X-ray CT apparatus is configured such that the head of the gantry can be tilted (tilted) in the direction of the body axis of the subject, so that the slice angle when scanning the subject can be optimally adjusted. .

Conventionally, there has been known an X-ray CT system that improves patient throughput by ensuring the safety of scanning and accurate alignment performance, and by moving the imaging table up and down and / or gantry tilt at high speed. (Patent Document 1).
JP2003-052689 (summary, figure)

  However, especially in the imaging table with IMS, there is an inconvenience between the IMS and the gantry at the time of gantry tilt, and the required tilt cannot be performed as it is, or there is a disadvantage that a short scanable range in which the IMS is withdrawn is taken. there were.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an X-ray CT apparatus and a control method thereof that can achieve both a required gantry tilt and a long scannable range. There is.

  The above problem is solved by the configuration of FIG. That is, the X-ray CT apparatus of the present invention (1) scans a subject to detect X-rays transmitted through the subject carried into the gantry cavity, and tilts back and forth in the subject body axis direction. 30 and a table 20 for moving the table portable part on which the subject is placed so as to be carried in and out of the gantry cavity part and moving the table portable part up and down, An input means for inputting scan plan information including information on the scan range of the subject and tilt angle information of the gantry, and the subject placed on the table transportable part are preliminarily photographed from the side surface and are a perspective image of the subject. Scout image capturing means for acquiring the scout image 100S, and a gantry cavity when the input tilt angle information is tilted within the input scan range Based on predetermined geometric two-dimensional position information G1, G2, H1, H2, etc. between the scout image of the subject including the shape of the table portable portion, a predetermined clearance or more can be secured between them. And an arithmetic means for obtaining the height of the table portable portion.

In the present invention (1), a predetermined gap between the gantry cavity and the scout image of the subject including the shape of the table transportable portion when tilted to the angle of the input tilt angle information in the input scan range. Interference between the gantry cavity and the table transportable part can be effectively avoided by the configuration that calculates the height of the table transportable part that can secure a clearance of a predetermined level or more based on the geometric two-dimensional position information. Therefore, it is possible to achieve both the required gantry tilt and long scanable range. Further, the configuration using the scout image 100S on the side surface of the subject makes it possible to easily adjust the height according to the physique of the subject.

  The table transportable portion of the present invention (1) includes a case of only a top plate (cradle) and a case of a top plate with IMS. In addition, the shape of the table portable portion in the above-mentioned “scout image of the subject including the shape of the table portable portion” is based on the known dimensional information about the table portable portion to cover the input scan range. The shape information of the table transportable part obtained in the above step can be used as a pseudo scant image on the side of the table transportable part.

  By the way, the top plate 21 of the table transportable parts 21 and 22 is made of a substance having a small X-ray absorption so as not to interfere with X-ray transmission. I don't see it. On the other hand, the portion of the IMS 22 is made of metal and its tip is carried into a part of the gantry cavity, but the tip is carried in only until just before the X-ray irradiation region. But no scout statue. Therefore, for the shape of the table transportable portion of the present invention, preferably, the shape (pseudo-scout image) of the table transportable portion side surface is synthesized from the known dimensional information about the table transportable portions 21 and 22.

  In the present invention (2), in the above-mentioned present invention (1), the table portable unit supports the top plate 21 on which the subject is mounted, the top plate 21 so as to be transportable, and is also carried into the gantry cavity itself. The intermediate support part (IMS) 22 which can be carried out is included. The present invention is particularly suitable for application to a table with an IMS.

  In the present invention (3), in the present invention (2), the scan range information includes scan start position and end position information in the subject body axis direction, and scan of the subject on a plane perpendicular to the body axis. Information of the field of view SFOV. Therefore, the required scan range of the subject can be secured safely.

  In the present invention (4), in the above-mentioned present invention (3), the calculation means matches the rotation center ISO of the gantry and the scan visual field center Q of the subject as much as possible within a range in which the clearance of the predetermined value or more is ensured. Thus, the height of the table portable part is obtained. Therefore, the subject and the table portable portion can be safely carried in and out of the gantry cavity, and high image quality can be obtained for the image within the scanning field of view.

  In the present invention (5), in the above-mentioned present invention (3), the calculation means includes the rotation center ISO of the gantry, the highest position of the subject, and the table portable portion within a range that ensures the clearance of the predetermined value or more. The height of the portable table portion is obtained so that the midpoint between the lowest position and the lowest position matches as much as possible. Therefore, the subject and the table portable part can be safely carried into and out of the gantry cavity.

  According to the present invention (6), in the above-mentioned present invention (1), there is provided a detecting means for detecting the height of the table portable part and a manual operation switch for raising / lowering the table portable part, wherein the lamp blinks. The lamp of the manual operation switch on the side where the possible one and the detected table portable part are different from the height determined by the self and turn on or blink, and the operation of the switch thereafter And a table control means for stopping the height change control of the table portable unit when these heights coincide with each other and also turning off the lamp. It is. Therefore, the height of the table can be changed safely and reliably according to the manual operation of an engineer or the like.

  According to the present invention (7), in the present invention (1), the detecting means for detecting the height of the table portable unit, the manual operation switch for raising / lowering the table portable unit, and the detected table The height display means for displaying the height of the portable part and the height obtained by itself, and the height of the table portable part are increased / decreased according to the operation of the manual operation switch. And a table control means for stopping the height change control of the table portable unit when the two match. Therefore, the height of the table can be changed safely and reliably according to the manual operation of an engineer or the like.

  In the present invention (8), in the above-mentioned present invention (2), display means for displaying predetermined information representing the positional relationship between the scout image of the subject including the image of the table portable portion and the gantry cavity on the screen. Is provided. Therefore, the safety of the scan plan can be easily confirmed visually.

  According to the control method of the X-ray CT apparatus of the present invention (9), the subject is scanned to detect the X-ray transmitted through the subject carried into the gantry cavity, and tilted back and forth in the subject body axis direction. A control method for an X-ray CT apparatus comprising: a gantry; and a table for moving a table portable portion on which the subject is placed so as to be carried into and out of the gantry cavity portion and moving the table portable portion up and down. An input step for inputting scan plan information including information on the scan range of the subject and tilt angle information of the gantry; and a fluoroscopic image of the subject obtained by photographing the subject placed on the table portable unit in advance from the side surface A scout image capturing step for acquiring a scout image, and a gantry when tilted to the angle of the input tilt angle information in the input scan range. Based on predetermined geometric two-dimensional position information between the cave and the scout image of the subject including the shape of the table portable unit, a table portable unit capable of ensuring a predetermined clearance or more between them is provided. And a calculation step for obtaining the height.

  In the present invention (10), in the above-mentioned present invention (9), in the calculation step, the rotation center of the gantry and the scan field center of the subject are matched as much as possible within a range in which the clearance equal to or greater than the predetermined is ensured. The height of the table portable part is obtained.

  In the present invention (11), in the above-mentioned present invention (9), the calculating step includes the rotation center of the gantry, the highest position of the subject, and the lowest of the table portable portion within a range that ensures the clearance of the predetermined value or more. The height of the portable table portion is obtained so that the midpoint between the positions matches as much as possible.

  As described above, according to the present invention, both the required gantry tilt and a long scanable range can be ensured, and the contribution to improving the performance of X-ray CT imaging is extremely large.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 1 is a configuration diagram of a main part of an X-ray CT apparatus according to an embodiment. This apparatus has a scanning gantry unit 30 that scans and reads a subject 100 with an X-ray fan beam XLFB, and a body axis on which the subject 100 is placed. The imaging table 20 is moved in the direction of CLb, and the operation console unit 10 is provided to perform remote control of the above-described units 30 and 20 and to be operated by an engineer or the like.

In the scanning gantry 30, 40 is a rotary anode type X-ray tube, 40 A is an X-ray controller, 50 is a collimator for limiting the X-ray slice width w, 50 A is a collimator controller, and 90 is a large number aligned in the channel CH direction. An X-ray detector in which X-ray detection elements (n = 1000) are arranged in, for example, two rows L1 and L2 in the direction of the body axis CLb, 91 is a projection of the subject based on the detection signal of the X-ray detector 90 A data acquisition unit (DAS: Data Acquisition System) that generates and collects data, 35 is a gantry that supports the X-ray imaging system so as to be rotatable around the subject body axis, 35A is a rotation control unit of the gantry 35, A tilt control unit 70 tilts the scanning gantry unit 30 before / after the subject body axis.

  FIG. 5A shows a schematic side view of the imaging table 20. Reference numeral 21 denotes a top plate (cradle) that mounts a subject and moves in the body axis direction, and 22 denotes an intermediate support portion (IMS) that supports the top plate 21 so as to be transportable in the body axis direction and is also movable in the gantry cavity. ), 23 is a lift control unit for moving the table portable units 21 and 22 in the upward / downward direction, and 24 is a base of the imaging table.

  Returning to FIG. 1, a gantry SW panel 31 operated by an engineer or the like is provided on the front surface of the scanning gantry unit 30, and manual operation buttons U, D, F, and Manual operation buttons FW and BW for operating B and gantry tilt are provided. Here, “U” is the up button of the table transportable parts 21 and 22, “D” is the down button, “F” is the forward button, “B” is the backward button, and “FW” is the gantry 30. A button for tilting (tilting) the head forward in the direction of the subject body axis (direction of the imaging table 20), “BW” indicates the head of the gantry 30 in the rear direction of the subject body axis (direction opposite to the imaging table 20). ) Is a button for tilting. Note that such a SW panel 31 may be provided on the imaging table 20 side.

  In the operation console unit 10, reference numeral 11 denotes a central processing unit that performs main control / processing (scan control, CT tomographic image reconstruction processing, etc.) of the X-ray CT apparatus, 11a denotes its CPU, 11b denotes RAM, ROM, etc. used by the CPU 11a. A main memory (MM) comprising 12 a command and data input device including a keyboard and a mouse, 13 a display device (CRT) for displaying scan plan information and CT tomograms, and 14 a CPU 11a and a scan gantry. A control interface for exchanging various control signals CS and monitor signals MS between the unit 30 and the imaging table 20, 15 a data collection buffer for temporarily storing projection data from the data collection unit 91, and 16 for data collection Projection data from the buffer 15 is accumulated and stored, and various applications necessary for the operation of the X-ray CT apparatus. A down-programs and various arithmetic / correction have secondary storage device stores the data file or the like for (hard disk device).

An inset (a) shows an example of various buttons (icons) for confirming the display by an engineer or the like and performing operations if necessary. “CONFIRM” is a confirmation button for completing the scan plan setting, “Tilt” is a confirmation button for starting the gantry tilt operation, and “Move to Scan” is a confirmation when starting to move the table portable units 21 and 22 to the scan start position. Button, "START
“SCAN” is a confirmation button for starting a scan (X-ray exposure), and “STOP” is a button for interrupting a scan sequence being executed.

Next, the operation of X-ray CT imaging with the above configuration will be outlined. The subject 100 is irradiated with the X-ray beam XLFB from the X-ray tube 40 in a state where the subject 100 is positioned in the cavity of the scanning gantry unit 30. In this state, the X-ray fan beam XLFB from the X-ray tube 40 passes through the subject 100 and enters the detector rows L1 and L2 of the X-ray detector 90 all at once. The data collection unit 91 generates projection data g ₁ (X, θ), g ₂ (X, θ) corresponding to each detection row output of the X-ray detector 90 and stores them in the data collection buffer 15. Here, X represents the channel number of the detector, and θ represents the projection (view) angle.

Further, X-ray projection similar to the above is performed at each view angle θ where the scanning gantry 35 is slightly rotated, and thus projection data for one rotation of the scanning gantry is collected and accumulated. At the same time, the imaging table 20 is moved intermittently / continuously in the direction of the body axis CLb in accordance with the axial / helical scan method, thus collecting and accumulating all projection data for the required imaging area of the subject. It is stored in the storage device 16. Then, the CPU 11a reconstructs a CT tomographic image of the subject 100 based on the projection data obtained after the end of all the scans or in parallel with the scans, and displays this on the display device 13.

  2 and 3 are flowcharts (1) and (2) of the X-ray CT imaging process according to the embodiment. After performing a scout scan of the subject 100 in advance, the process 100 is input. FIG. 5A shows an image of scout scanning. Scout scanning is imaging performed by conveying a subject while the gantry is fixed at a constant view angle, and the obtained image corresponds to a conventional two-dimensional X-ray image. Here, a scout image with a view angle of 90 degrees (subject side) is taken. As shown in the figure, in the imaging table with the IMS 22, not only the top plate 21 but also the tip of the IMS 22 is partially carried into the gantry cavity, so that the subject 100 can be transported to a deeper position in the cavity, thereby A long scanable range is obtained in the direction of the specimen body axis. In FIG. 5A, for ease of comparison, the loading limit position when the subject is loaded only with the top plate 21 is indicated by a dotted line 100 '.

  In step S11, a scan plan information setting screen is displayed. FIG. 4 shows an example scan plan information setting screen. In step S12, a technician or the like sets scan parameters for the subsequent axial / helical scan while referring to the scout image 100S of the subject.

  An example of scan plan information for acquiring the image “A” includes: scan type [Scan Type] = axial, scan start position [Start Loc] = z1, scan end position [End Loc] = z4, number of scans [NO. of Image S] = 11 sheets, slice thickness [Thick] = 3 mm, gantry tilt angle = β °, tube voltage [kV] = 120 kV, tube current [mA] = 280 mA.

  In step S13, the height information of the table portable units 21 and 22 is set based on the set scan plan information. In other words, based on the input gantry tilt angle, the scan range in the body axis direction, and the scan field of view SFOV of the subject, within a range that can cover the required scan range while avoiding interference with the gantry cavity. Preferably, the SFOV center Q and the gantry rotation center ISO coincide with each other as much as possible to calculate the height corresponding to the position (position in the body axis direction) of the table transportable parts 21 and 22, and set this to the set value. And Alternatively, the heights of the table transportable portions 21 and 22 are obtained so that the midpoint between the highest position of the subject and the lowest position of the table transportable portion matches the gantry rotation center ISO as much as possible, and this is set. It is also good. Such a setting of the height of the IMS 22 is preferably performed by creating a reference table of a position and height that can realize the optimum clearance for each gantry tilt angle in advance and referring to the table. The best one is automatically selected. A specific example of the shooting table height setting process will be described below.

  FIG. 5B shows a case where the gantry 30 is tilted in the forward direction (FWD). Here, it is assumed that the tip portion of the IMS 22 can be moved up to approximately the middle point of the gantry cavity at the maximum. Further, an effective portion of the scout image of the subject is indicated by a thick solid line, and the scan range of the subject can sufficiently cover, for example, the liver portion. Since all the information such as the dimensions of each device 30, 20 constituting this system, the arrangement, and the height information of the table portable part when the subject is subjected to the scout scan are known, the geometric dimension between them is determined. Accurately required.

As shown in the drawing, the interference between the subject head (the highest part) and the c-plane of the gantry cavity becomes a problem above the gantry cavity, and the height of the subject head is H1, and the height of the c-plane is G1. Then, the first clearance between the two becomes (G1-H1). In addition, interference between the tip of the IMS 22 and the e-plane of the gantry cavity can be a problem below the gantry cavity.
The tip of 2 cannot reach the e-plane of the cavity. In this case, if the height of the IMS tip is H2 and the height of the e-plane is G2, the second clearance between them is larger than (H2-G2) with a margin. Therefore, within a range in which a predetermined value or more can be secured for each of the first and second clearances, preferably, the table portable unit 21, in such a direction that the gantry rotation center ISO and the center Q of the subject SFOV coincide as much as possible. 21 is obtained and height information is set. In the example shown in the figure, even if the gantry 30 is tilted by α ° in the forward direction, the tilt scan can be performed with the same height of the table portable parts 21 and 22 as when the scout scan of the subject is performed.

  Although not shown, the midpoint between the gantry rotation center ISO and the highest position of the subject that can be observed in the scout image (in the figure, the head of the nose of the subject) and the lowest position of the table portable unit 21/22. And the heights of the table transportable units 21 and 22 may be obtained so as to match as much as possible.

  FIG. 6A shows a case where the gantry tilts backward (BWD). As shown in the figure, the interference between the subject's head and the a surface of the gantry cavity is a problem above the gantry cavity. If the height of the subject head is H1, and the height of the a-plane is G1, the first clearance between them is (G1-H1). On the lower side of the gantry cavity, interference between the tip of the IMS 22 and the f-plane of the gantry cavity becomes a problem. If the height of the IMS tip is H2 and the height of the f-plane is G2, the second between them is the second. The clearance (indicated by the arrow P) is (H2−G2) <predetermined threshold value, which may cause interference. In this case, as shown in FIG. 6B, a second clearance equal to or greater than a predetermined threshold can be obtained by raising the height of the table portable units 21 and 22.

  Returning to FIG. 2, in step S14, the recon plan information is set, and in step S15, input of a setting confirmation “CONFIRM” button is awaited.

  If the scan range cannot be ensured, the process returns to the localization setting in steps S11 and S12. If necessary, a part of the human parameter is changed and the height is set again. Moreover, although the height of the said table portable part 21 and 22 was calculated | required by calculation, an engineer etc. may correct the height calculated | required by the said calculation, seeing the localization screen of FIG.

  Thus, when the “CONFIRM” button is input, the process proceeds to step S16, and the X-ray tube 40 is activated based on the set scan parameters (tube voltage kV, tube current mA, etc.).

  In step S17, it is determined whether or not the current height of the imaging table 20 needs to be changed. The imaging table 20 is normally maintained at the height adopted in scout image shooting, but change control is required if the height set in the scan plan is different from the current height. In this case, in step S18, a message to that effect is displayed on the display unit 13 to prompt the engineer to confirm, and a known auto voice function or an intercom which gives instructions directly to the patient via the microphone of the operation console unit A voice message indicating that the table up / down operation is performed (for example, “table goes up”) is output to the speaker.

The up / down control of the table portable units 21 and 22 is executed by a CPU (not shown) in the table control unit that has received the height instruction information from the CPU 11a, for example. ”/“ D ”button blinks. An engineer who sees this presses the blinking button “U” / “D”, and accordingly the table portable units 20 and 21 are up / down. Eventually, when the table portable parts 21 and 22 reach the instructed height, the table up / down control is stopped and the blinking of the “U” / “D” button is turned off. In addition, the CPU 11a is notified that the up / down control is completed. Although not shown, the imaging table 20 is provided with a height detection means of the table portable portion, and the information on the height detected here is also notified to the CPU 11a side. On the other hand, the CPU 11a waits for the height change to be completed in step S19, and when it is completed, the process proceeds to step S20. If it is not necessary to change the height in step S17, the processes in steps S18 and S19 are skipped.

  Although not shown in the drawing, instead of the method of blinking the “U” / “D” button, the height of the detected table portable portion and the height obtained by itself are displayed in graphs. A display means is provided to increase / decrease the height of the table transportable portion according to the operation of the “U” / “D” button, and stop the height change control of the table transportable portion when these heights match. You may comprise so that it may be made.

  In step S20, it is determined whether or not tilt control of the scanning gantry unit 30 is necessary. The scanning gantry unit 30 is normally returned to the tilt angle = 0 °, but tilt control is required when the gantry tilt angle set in the scan plan is different from the current tilt angle. In this case, in the same manner as described above, the “Tilt” icon on the display unit 13 blinks in step S21 to prompt the engineer to confirm, and a voice message (for example, that the tilt operation is performed by the auto voice function or the intercom function) "The gantry tilts toward the head") is output to the speaker.

  The tilt control of the scanning gantry unit 30 is executed by, for example, a CPU (not shown) in the tilt control unit 70 that has received the tilt angle instruction information from the CPU 11a. The CPU first performs “FW” / “ BW "button blinks. An engineer who sees this presses the flashing button “FW” / “BW”, and the scanning gantry unit 30 is tilted forward / backward accordingly. Eventually, when the scanning gantry unit 30 is tilted to the instructed angle, the tilt control is stopped and the flashing of the “FW” / “BW” button is turned off. Further, the CPU 11a is notified that the tilt control has been completed. On the other hand, the CPU 11a waits for the tilt to be completed in step S22, and when it completes, the process proceeds to step S23. If it is determined in step S20 that there is no need for gantry tilt, steps S21 and S22 are skipped. In step S23, rotation of the gantry 35 is activated.

  The flow proceeds to FIG. 3. In step S24, the “Move to Scan” icon on the display unit 13 blinks, prompting the engineer to confirm the start of the top board movement, and in step S25, waiting for the input of the “Move to Scan” icon. When input is made, a voice message to the effect that the photographic stand is moved (eg, “the photographic stand is advanced”) is output to the speaker in step S26, and then the movement control of the photographing tables 21 and 22 is energized in step S26. To do. In step S27, scanning preparation is completed (gantry rotation completion and movement of the imaging tables 21 and 22 are completed). When scanning preparation is completed, the process proceeds to step S28.

  In step S28, the “START SCAN” icon blinks, and in step S29, the input of the “START SCAN” icon is waited. When the input is done, scanning from the first scan position is started in step S30. In step S31, projection data for each view angle is collected and accumulated, and in step S32, it is determined whether or not all scans are completed. If not completed, the process returns to step S30. When all the scans are completed, the process proceeds to step S33, and a CT tomographic image of the subject is reconstructed based on the obtained projection data. In step S 34, the obtained CT tomogram is displayed on the display device 13.

  In the above-described embodiment, the case where the guide tilt is performed at the start of scanning has been described, but the present invention is not limited to this. The guide tilt may be performed everywhere during scanning.

Further, although the preferred embodiment of the present invention has been described, it goes without saying that various changes in the configuration, control, processing, and combination of each part can be made without departing from the spirit of the present invention.

It is a principal part block diagram of the X-ray CT apparatus by embodiment. It is a flowchart (1) of the X-ray CT imaging process by embodiment. It is a flowchart (2) of the X-ray CT imaging process by embodiment. It is a figure explaining the scan plan information setting screen by embodiment. It is FIG. (1) explaining the height setting process of the imaging | photography table by embodiment. It is FIG. (2) explaining the height setting process of the imaging | photography table by embodiment.

Explanation of symbols

10 Operation console 11 Central processing unit 11a CPU
11b Main memory (MM)
12 Input device 13 Display device (CRT)
14 Control Interface 15 Data Collection Buffer 16 Secondary Storage Device (Hard Disk Device etc.)
20 Shooting table 21 Top board (cradle)
22 IMS (Inter Midiate Support)
23 Lift control unit 24 Base 30 Scanning gantry unit 31 Gantry SW panel 35 Gantry 40 X-ray tube 50 Collimator 70 Tilt control unit 90 X-ray detector 91 Data collection unit 100 Subject

Claims (11)

A gantry that scans the subject and detects X-rays transmitted through the subject carried into the gantry cavity and tilts back and forth in the direction of the subject body axis, and a table portable portion on which the subject is placed An X-ray CT apparatus comprising a table that moves to and from the gantry cavity and moves the table portable portion up and down,
Input means for inputting scan plan information including information on the scan range of the subject and tilt angle information of the gantry;
Scout image photographing means for photographing a subject placed on the table portable unit in advance from the side surface and obtaining a scout image that is a fluoroscopic image of the subject;
In the input scan range, a predetermined geometric shape between the gantry cavity and the scout image of the subject including the shape of the table transportable portion when tilted to the angle of the input tilt angle information. An X-ray CT apparatus comprising: an arithmetic unit that obtains a height of a portable table portion that can ensure a predetermined clearance or more based on two-dimensional position information. The table portable unit includes a top plate on which a subject is mounted, and an intermediate support unit that supports the top plate so as to be transportable and can be carried into and out of the gantry cavity. The X-ray CT apparatus described. The information on the scan range includes information on a scan start position and an end position in the direction of the subject body axis, and information on a scan field of view of the subject in a plane perpendicular to the body axis. X-ray CT system. The calculating means obtains the height of the portable table portion so that the rotation center of the gantry and the scan field center of the subject coincide as much as possible within a range in which a clearance equal to or greater than the predetermined value is ensured. Item 4. The X-ray CT apparatus according to Item 3. The calculation means is configured to allow the rotation center of the gantry and the midpoint between the highest position of the subject and the lowest position of the table portable part to match as much as possible within a range that secures the clearance of the predetermined value or more. The X-ray CT apparatus according to claim 3, wherein the height of the portable part is obtained. Detecting means for detecting the height of the portable table portion;
A manual operation switch for raising / lowering the table transportable part, which can blink the lamp,
Since the detected height of the portable table portion is different from the height determined by itself, the lamp of the manual operation switch on the side that matches them is turned on or blinked, and the portable table portion is then operated according to the operation of the switch. And a table control means for stopping the height change control of the table portable unit when the heights coincide with each other and also turning off the lamp. Item 2. The X-ray CT apparatus according to Item 1. Detecting means for detecting the height of the portable table portion;
A manual operation switch for raising / lowering the table portable part,
Height display means for displaying the detected height of the table portable part and the height determined by the self, respectively,
And a table control means for increasing / decreasing the height of the portable table portion according to the operation of the manual operation switch and stopping the height change control of the portable table portion when these heights coincide with each other. The X-ray CT apparatus according to claim 1, wherein: 3. The X-ray CT according to claim 2, further comprising display means for displaying predetermined information representing a positional relationship between a scout image of a subject including an image of a table portable part and a gantry cavity on a screen. apparatus. A gantry that scans the subject and detects X-rays transmitted through the subject carried into the gantry cavity and tilts back and forth in the direction of the subject body axis, and a table portable portion on which the subject is placed A control method for an X-ray CT apparatus comprising a table that moves to and from the gantry cavity and moves the table transportable portion up and down,
An input step for inputting scan plan information including information on the scan range of the subject and tilt angle information of the gantry;
A scout image photographing step of photographing a subject placed on the table portable unit in advance from a side surface and obtaining a scout image that is a fluoroscopic image of the subject;
In the input scan range, a predetermined geometric shape between the gantry cavity and the scout image of the subject including the shape of the table transportable portion when tilted to the angle of the input tilt angle information. A control method for an X-ray CT apparatus, comprising: a calculation step for obtaining a height of a portable table portion capable of ensuring a predetermined clearance or more based on two-dimensional position information. The computing step is characterized in that the height of the portable table portion is obtained so that the rotation center of the gantry and the center of the scan field of the subject coincide as much as possible within a range in which the clearance of the predetermined value or more is ensured. Item 10. A method for controlling an X-ray CT apparatus according to Item 9. In the calculation step, the rotation center of the gantry and the midpoint between the highest position of the subject and the lowest position of the table portable portion are matched as much as possible within a range in which the clearance equal to or greater than the predetermined is ensured. The method for controlling an X-ray CT apparatus according to claim 9, wherein the height of the portable part is obtained.

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