JP2014054354A - Orbital synchronism helical shuttle scan ct apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct an angle error at an orbital start position of an X-ray vessel to an allowable range in each going passage or each return passage, respectively, in helical shuttle scan.SOLUTION: An orbital synchronism helical shuttle scan CT apparatus includes: X-ray vessel position detecting parts 30, 31 for detecting an angle of an orbital start position of an X-ray vessel 26 in a going route or a return route of a bed top plate; an X-ray vessel angle error detecting part 32 for detecting an angle error of the X-ray vessel 26 at the respective orbital start positions by comparing the angle of the orbital start position in every going passage or return passage; a correction possible/impossible determination part 41 for determining whether or not an angle error is in the correctable range in helical shuttle scanning to collect images by rotating the X-ray vessel 26 and reciprocatingly moving the bed top plate 17; a data creating part 42 for creating angle error correction data when the determination result of the correction possible/impossible determination part 41 falls within the correctable range; and a control part 38 for correcting an angle error in the respective orbital start positions of the going passage and the return passage to an allowable range according to the angle error correction data from the data creating part 42.

Description

  Embodiments described herein relate generally to an orbit-synchronized shuttle helical scan CT apparatus.

  In recent years, an X-ray CT apparatus performs a shuttle helical scan in which an X-ray tube is continuously rotated on a circular orbit centered on the subject P, and a bed top plate on which the subject P is placed is repeatedly reciprocated. An imaging technique is used (see Patent Document 1 below). According to this imaging method, for example, it is possible to obtain an image with a high subtraction effect by imaging the state before and after the administration of the contrast agent.

  FIG. 4 shows an X-ray tube 2 that generates X-rays, an X-ray detector 3 that detects X-rays, an X-ray tube 2 and an X-ray detector 3 in the CT apparatus 1 that performs shuttle helical scanning. A ring-shaped rotating body 4 that can be rotated while holding the object, and a bed top plate that can reciprocate in the hollow portion 5 between the X-ray tube 2 and the X-ray detector 3 on which the subject P is placed. FIG. The rotating direction of the rotating body 4 is a clockwise direction in the drawing. An X-ray irradiation path 7 through which X-rays generated from the X-ray tube 2 reach the X-ray detector 3 is formed in the hollow portion 5.

  For example, when the CT apparatus 1 performs a shuttle helical scan and images the state before and after the administration of the contrast agent, the trajectory start position of the X-ray tube 2 for starting image acquisition is determined in each of the forward path and the return path. Must match. For example, the trajectory start position of the X-ray tube 2 for each forward path (or each return path) is the true position of a specific part of the subject P placed on the couch top 6 as shown by the solid line in FIG. I try to be on top.

Japanese Patent Laid-Open No. 6-125889

  However, due to various factors, the trajectory start position of the X-ray tube 2 when starting image acquisition is at an angle “α” as shown by the broken line with respect to the trajectory start position indicated by the solid line in FIG. An angular error may occur. If this angle error is within the allowable range, a high-accuracy image can be obtained when the images collected in each scan during the shuttle helical scan are overlapped. The accuracy of the image when the images collected by scanning are superimposed is lowered.

Factors that cause the angle error of the angle “α” at the trajectory start position of the X-ray tube 2 include the following factors.
(1) Acceleration from the start of movement of the bed top plate 6 when reciprocating until reaching the expected bed top plate moving speed.
(2) A change in acceleration from the start of movement to the expected position of the couch top with respect to a change in load on the couch top 6.
(3) Change in time from the start of movement to the expected position of the couch top with respect to a change in load on the couch top 6.
(4) The angular position of the X-ray tube 2 rotating at a constant speed when the expected bed top position is reached.
(5) Adjustment of the rotational speed of the X-ray tube 2.
(6) Mechanical constraints on the above factors (1) to (5).
(7) The weight of the subject P.
(8) An imaging range depending on the height of the subject P and the length of the imaging region.

  The present invention has been made to solve such a problem, and the object of the present invention is to ensure that the angle error at the trajectory start position of the X-ray tube is within an allowable range in each of the forward path and the return path during shuttle helical scanning. It is correct | amending so that it may become.

  According to the embodiment, the X-ray tube that generates X-rays, the X-ray detector that detects X-rays generated from the X-ray tube, and the X-ray detector and the X-ray tube sandwich the hollow portion. A gantry that is opposed to each other and rotates integrally, a bed top plate that places the subject and reciprocates across the X-ray irradiation path formed in the hollow portion of the gantry, and the table top A bed driving unit for reciprocating the plate, a gantry driving unit for rotating the X-ray tube, and an X-ray tube position detecting unit for detecting the angle of the trajectory start position of the X-ray tube in the forward or return path of the bed top plate And the angle of the trajectory start position detected by the X-ray tube position detection unit for each forward path or return path, and detecting the angle error of the X-ray tube at each trajectory start position. The angle error detected by the detector and the X-ray tube angle error detector rotates the X-ray tube. When the shuttle helical scan that collects images by reciprocating the couchtop and collecting images is within the correctable range during the shuttle helical scan, and the angle when the determination result at the correctable / uncorrectable determining unit is within the correctable range A data creation unit that creates error correction data, and a control unit that corrects the angle error of each of the trajectory start positions of the forward path and the return path within an allowable range by the angle error correction data from the data creation unit. To do.

It is a perspective view which shows an orbit synchronous shuttle helical scan CT apparatus. It is a block diagram which shows the structure of the control system of an orbit synchronous shuttle helical scan CT apparatus. It is a flowchart explaining the detection and correction | amendment of the angle error in the orbit start position of an X-ray tube. It is explanatory drawing of the prior art example explaining the state which the X-ray tube produced the angle error in the orbit start position.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing an orbit synchronization shuttle helical scan CT apparatus 11. The orbit synchronization shuttle helical scan CT apparatus 11 includes a gantry 12, a bed 13, and a console 14.

  The gantry 12 has a housing 16 having a hollow portion 15 formed in the center, and an X-ray tube for generating X-rays and X-rays are generated in the housing 16 as shown in FIG. The X-ray detector to detect, various motors, etc. are accommodated. In the hollow portion 15, an X-ray irradiation path (see FIG. 4) is formed in which X-rays generated from the X-ray tube reach the X-ray detector.

  The couch 13 has a couch top 17 on which the subject P is placed and can be moved in the horizontal and vertical directions. The couch top 17 is placed in the horizontal direction on the subject P placed on the couch top 17. Is moved into and out of the hollow portion 15 of the gantry 12 together with the bed top plate 17. The subject P placed on the couch top 17 that is taken in and out of the hollow portion 15 reciprocates so as to cross the X-ray irradiation path formed in the hollow portion 15.

The console 14 is a part for operating the orbital-synchronized shuttle helical scan CT apparatus 11, and includes a control box 22 that houses a keyboard 18, a microphone 19, a speaker 20, a monitor 21, a control unit described later with reference to FIG. Yes.

  FIG. 2 is a block diagram showing the configuration of the control system of the orbit synchronization shuttle helical scan CT apparatus 11.

  The gantry 12 is provided with a gantry driving unit 23 that drives each part in the gantry 12, and a gantry rotating unit 24 and a gantry tilting unit 25 are connected to the gantry driving unit 23.

  The gantry rotating unit 24 includes an X-ray tube 26 that generates X-rays, an X-ray detector 27 that detects X-rays generated from the X-ray tube 26 and transmitted through the subject P, and an X-ray detector. 27 and the X-ray tube 26 and the X-ray tube 26 and the X-ray tube 26 and the X-ray tube 26 and the X-ray tube 26 and the X-ray tube 26 and the X-ray tube 26. A rotating motor 28 that rotates the device 27 integrally is provided.

  The gantry tilting portion 25 is provided with a holding body (not shown) that holds the rotating body so that it can be tilted with respect to the vertical plane, and a tilting motor 29 that tilts the holding body.

  Further, the gantry 12 is connected to the gantry driving unit 23, and X is the position of the X-ray tube 26 when image collection is started in the outward path in which the bed top plate 17 enters the hollow portion 15 of the gantry 12. In the case where image acquisition is started in the forward X-ray tube position detection unit 30 that detects the angle of the trajectory start position of the tube 26 and the return path in which the bed top plate 17 exits the hollow portion 15 of the gantry 12 The X-ray tube position detection unit 31 for detecting the trajectory start position of the X-ray tube 26, which is the position of the X-ray tube 26, and the X-ray tube position detection unit 30 for the outward path are detected. The angle of the trajectory start position or the angle of the trajectory start position detected by the return path X-ray tube position detector 31 is compared, and the angle error of the X-ray tube 26 at the trajectory start position in each of the forward path and the return path. X-ray tube angle to detect Error detector 32 is provided.

  The bed 13 is provided with a bed driving unit 33 for driving the bed 13. The bed driving unit 33 is provided with a bed table horizontal movement unit 34 for moving the bed table 17 in the horizontal direction and the bed table 17 up and down. A bed top / bottom moving unit 35 that moves in the direction is connected.

  The couchtop horizontal movement unit 34 is provided with a horizontal movement motor 36 that moves the couchtop 17 in the horizontal direction, and the couchtop vertical movement unit 35 is moved up and down to move the couch top 17 up and down. A moving motor 37 is provided.

  The console 14 is provided with a control unit 38 that is connected to the gantry driving unit 23 and the bed driving unit 33 and transmits a control signal to the gantry driving unit 23 and the bed driving unit 33. A human interface 39 including the keyboard 18, microphone 19, speaker 20, monitor 21, and the like shown in FIG. 1 is connected to the control unit 38.

  Further, the console 14 includes an allowable range determination unit 40 that determines whether or not the angle error detected by the X-ray tube angle error detection unit 32 is within the allowable range when collecting images during shuttle helical scan, and the detected angle. A correction enable / disable determination unit 41 that determines whether the error is within a correctable range during shuttle helical scan in which an image is collected by rotating the X-ray tube 26 that generates X-rays and reciprocating the bed top plate 17; Data for creating angle error correction data when the determination result at the propriety determination unit 41 is within the correctable range and for generating uncorrectable data when the determination result at the correction propriety determination unit 41 is outside the correctable range A creation unit 42 is provided. The allowable range determination unit 40 and the data creation unit 42 are connected to the control unit 38.

  Here, the detected angle error being within the allowable range means that the angle error of the X-ray tube 26 when image acquisition is started in each of the forward path and the return path (corresponding to “α” shown in FIG. 4). Angle) is smaller than a preset threshold (allowable range). In this case, a high-accuracy image can be obtained when the images collected in each scan are superimposed without performing correction that further reduces the angular error of the trajectory start position.

  That the determination result in the correction possibility determination unit 41 is within the correctable range means that the angle error of the trajectory start position of the X-ray tube 26 when starting image acquisition in each of the forward path and the return path (shown in FIG. 4). (The angle corresponding to “α”) is larger than a preset threshold (allowable range), but by changing the moving speed of the couch top 17 or changing the rotational speed of the X-ray tube 26. The state in which the angular error can be corrected to be within the allowable range.

  That the determination result by the correction possibility determination unit 41 is out of the correctionable range means that the angle error of the trajectory start position of the X-ray tube 26 when starting image acquisition in each of the forward path and the return path (shown in FIG. 4). The angle corresponding to “α”) is larger than a preset threshold value (allowable range), and the rotational speed of the X-ray tube 26 is varied or the moving speed of the couch top 17 is varied. Is a state in which the angular error cannot be corrected to be within the allowable range. For example, in order to make the angle error within an allowable range, the acceleration of the couch top 17 must be increased rapidly, resulting in an excessive burden and anxiety on the subject P. This is the case where the mechanism of the rotating part may be damaged due to a rapid increase in the rotational speed of the X-ray tube 26.

  In addition, the angle error correction data means that the orbit start position of the X-ray tube 26, which is the position of the X-ray tube 26 when image acquisition is started, causes an angle error as indicated by the solid line and the broken line in FIG. In this case, the rotation speed of the X-ray tube 26 is changed so that the angular error is within the allowable range, or the movement speed of the bed top plate 17 is changed. For example, in the case shown in FIG. 4, by increasing the rotational speed of the X-ray tube and / or decreasing the moving speed of the couch top, both the trajectory start position indicated by the solid line and the broken line are indicated. It is possible to correct the angle error with respect to the trajectory start position indicated by (2) so that it falls within an allowable range.

  Next, detection and correction of the angle error at the trajectory start position of the X-ray tube 26 will be described based on the flowchart of FIG.

  First, after placing the subject P on the couch top 17, the X-ray tube 26 is rotated around the hollow portion 15 by driving the gantry rotating unit 24 (step S 1), and the couch top is moved horizontally. By driving the portion 34, the bed top plate 17 is reciprocated a plurality of times so as to be taken in and out of the hollow portion 15 (step S2). In these steps S1 and S2, the X-ray tube 26 does not generate X-rays.

  While the X-ray tube 26 in a state where X-rays are not generated is rotated and the bed top plate 17 is reciprocated, the angle of the trajectory start position of the X-ray tube 26 in the forward path is set as the forward X-ray tube. The position detection unit 30 detects the angle of the trajectory start position of the X-ray tube 26 on the return path, and the return path X-ray tube position detection unit 31 detects the angle, but here, in order to simplify the explanation, Only the detection in the forward path will be described.

  When the angle of the trajectory start position of the X-ray tube 26 in the forward path is detected (step S3), it is determined whether or not the number of times of angle detection has reached a preset number (N times) (step S4). If the number of detections reaches N (YES in step S4), the angle error of the detected angle is detected by the X-ray tube angle error detection unit 32 (step S5).

  When the angle error is detected by the X-ray tube angle error detection unit 32, the allowable range determination unit 40 determines whether the angle error is within the allowable range (step S6).

  If it is determined that the angle error is within the allowable range (YES in step S6), an image obtained when the images collected in each scan are superimposed without correcting the angle error at the trajectory start position. Therefore, without generating angle error correction data, which will be described later, X-rays are generated from the rotating X-ray tube 26 and the table top 17 is reciprocated to move the subject P. A shuttle helical scan to be inspected is performed (step S7).

  On the other hand, when it is determined in step S6 that the angle error is outside the allowable range (NO in step S6), the correction possibility determination unit 41 determines whether or not the angle error is within the correctable range. (Step S8).

  If it is determined that the angle error is within the correctable range (YES in step S8), the data creation unit 42 creates angle error correction data (step S9), and the created angle error correction data is used as the control unit 38. (Step S10), and drives each part of the gantry 12 and each part of the bed 13 based on the transmitted angle error correction data (Step S11), and generates X-rays from the rotating X-ray tube 26. The table top 17 is reciprocated to perform a shuttle helical scan for inspecting the subject P (step S7).

  If it is determined in step S8 that the angle error is outside the correctable range (NO in step S8), the data creation unit 42 creates uncorrectable data (step S12), and the created uncorrectable data Is transmitted to the control unit 38 (step S13). When the uncorrectable data is transmitted to the control unit 38, the monitor 21 displays that the correction is impossible, and the operator who sees the display performs a necessary measure, for example, an operation such as canceling the scan. .

  In the flowchart of FIG. 3, the detection and correction of the angle error at the trajectory start position of the X-ray tube 26 in the forward path of the bed top plate 17 has been described. Detection and correction of the angle error at the trajectory start position of the sphere 26 are performed.

  In such a configuration, according to the orbit synchronization shuttle helical scan CT apparatus 11, when the shuttle helical scan is performed, the X-ray tube 26 that does not generate X-rays is rotated and the subject P is placed. By reciprocating the bed top 17 a plurality of times, the angle of the trajectory start position of the X-ray tube 26 is detected as described in step S3 of the flowchart of FIG. Then, as described in step S5 of the flowchart of FIG. 3, an angle error of the detected angle is detected. If the detected angle error is within the allowable range as described in step S6 of the flowchart of FIG. 3, the object P is not generated as described in step S7 of the flowchart of FIG. A shuttle helical scan is performed.

  In this case, the shuttle helical scan can be quickly performed without the trouble of creating the angle error correction data. In addition, since the X-ray tube 26 does not generate X-rays until the shuttle helical scan is started, the X-ray exposure amount of the subject P can be reduced.

If the detected angle error is outside the allowable range and the angle error is within the correctable range, as described in step S9 of the flowchart of FIG. Based on the correction data, each part of the gantry 12 and each part of the bed 13 are controlled. Then, by controlling each part of the gantry 12 and each part of the bed 13 based on the angle error correction data, the accuracy of the image obtained when the images collected in each scan at the time of the shuttle helical scan are superimposed is increased. be able to. Further, when controlling each part of the gantry and each part of the bed 13 based on the angle error correction data, when the rotational speed of the X-ray tube 26 is increased or the moving speed of the bed top plate 17 is increased. The amount of X-ray exposure of the subject P during the shuttle helical scan can be reduced.

  If the detected angular error is outside the correctable range, as described in step S12 of the flowchart of FIG. 3, the correction impossible data is created so that the operator can take necessary measures. Optimal measures can be taken according to the condition at that time. Then, it is possible to prevent an excessive burden and anxiety on the subject P by rapidly increasing the acceleration of the bed top 17 in order to correct the angle error, and to correct the angle error. Therefore, it is possible to prevent the mechanism of the rotating part from being damaged due to a sudden increase in the rotational speed of the X-ray tube 26.

  In the present embodiment, when the shuttle helical scan is performed, the bed top plate 17 on which the subject P is placed is reciprocated a plurality of times so that the trajectory start position according to the weight of the subject P is reached. Although the case where the angle error of the X-ray tube 26 is detected has been described as an example, it is also effective to create a plurality of simulated angle error correction data in advance using various human models having different weights and heights. It is. By preparing such simulated angular error correction data in advance, if the shuttle helical scan needs to be urgently performed, the angle of the X-ray tube 26 is based on the simulated angular error correction data. Shuttle helical scan that eliminates the error can be performed.

  According to the embodiment described above, the angle of the trajectory start position of the X-ray tube 26 in the forward path or the return path of the bed top plate 17 is detected a plurality of times by the X-ray tube position detection units 30 and 31 for the forward path or the return path. Then, the detected angle of the trajectory start position is compared for each forward path or return path, the angle error of the X-ray tube 26 at each trajectory start position is detected by the X-ray tube angle error detection unit 32, and the detected angle Whether or not the error is within the correctable range at the time of image collection is determined by the correctability determination unit 41, and when the determination result is within the correctable range, the data creation unit 42 creates angle error correction data and creates the created angle By correcting the angle error of the trajectory start position of the X-ray tube 26 between the forward path and the return path at the time of the shuttle helical scan with the error correction data, each time at the shuttle helical scan is corrected. It is possible to increase the accuracy of the resulting image when superimposed images collected by scanning.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 12 Gantry 15 Hollow part 17 Bed top plate 23 Gantry drive part 26 X-ray tube 27 X-ray detector 30 Outbound X-ray tube position detection part 31 Return X-ray tube position detection part 32 X-ray tube angle error Detection unit 33 Sleeper drive unit 38 Control unit 41 Correction determination unit 42 Data creation unit

Claims (5)

An X-ray tube that generates X-rays;
An X-ray detector for detecting X-rays generated from the X-ray tube;
A gantry in which the X-ray detector and the X-ray tube are disposed opposite to each other with a hollow portion interposed therebetween, and are rotated together;
A bed top plate that places the subject and reciprocates across the X-ray irradiation path formed in the hollow portion of the gantry.
A bed driving unit for reciprocating the bed table;
A gantry driving unit for rotating the X-ray tube;
An X-ray tube position detector for detecting an angle of the trajectory start position of the X-ray tube in the forward path or the return path of the bed top;
The angle of the trajectory start position detected by the X-ray tube position detection unit is compared for each forward path or return path, and the angle error of the X-ray tube at each trajectory start position is detected. An error detector;
Determining whether the angle error detected by the X-ray tube angle error detector is within a correctable range during shuttle helical scan in which the X-ray tube is rotated and the bed top plate is reciprocated to collect images. A correction propriety determination unit to perform,
A data creation unit that creates angle error correction data when the determination result in the correction possibility determination unit is within a correctable range;
A control unit that corrects the angular error of each of the trajectory start positions of the forward path and the return path within an allowable range based on the angular error correction data from the data generation unit;
An orbit-synchronized shuttle helical scan CT apparatus comprising:   2. An orbit-synchronized shuttle helical scan CT apparatus according to claim 1, wherein the generation of X-rays from the X-ray tube is performed at the time of shuttle helical scan after detecting an angle error of the X-ray tube. .   The orbit synchronization shuttle according to claim 1 or 2, wherein the control unit corrects an angular error of the orbit start position to be within an allowable range by changing a rotation speed of the X-ray tube. Helical scan CT system.   The orbit synchronization shuttle helical according to claim 1 or 2, wherein the control unit corrects an angular error of the orbit start position to be within an allowable range by changing a moving speed of the bed top plate. Scan CT device. 5. The trajectory synchronization according to claim 1, wherein the data creation unit creates uncorrectable data when a determination result by the correction enable / disable determination unit is outside a correctable range. 6. Shuttle helical scan CT system.

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