JP2003024324A - X-ray ct system and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely synchronize the rotation angle of a gantry rotation part with the position of a top plate. SOLUTION: This X-ray CT system has the gantry rotation part 633 for scanning by detecting transmitted X-rays as the result of irradiating a subject with the X-rays from different angles and the system is provided with a gantry device 620 capable of controlling the rotational speed of the rotation part 633 and a carrying device 640 with controlled carrying speed for carrying the subject to the scanning face of the device 620. The system obtains the logical position of the top plate for every prescribed timing from the rotation angle of the gantry rotation part 633 and corrects a carrying speed set pattern for controlling the carrying speed of the top plate 641 based on a difference between the logical position of the top plate and the measured position of the top plate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an X-ray CT system for obtaining a tomographic image of a subject by X-ray irradiation and a control method therefor.

[0002]

2. Description of the Related Art Generally, an X-ray CT system irradiates a subject (patient) with X-rays and detects the X-rays transmitted through the subject, and various settings are made for the gantry device. It is composed of an operation console that reconstructs and displays an X-ray tomographic image based on the data output from the gantry device, and a transport device that mounts a subject and transports it into the gantry device.

1A and 1B are general X-rays C
It is a front view and a side view of the gantry device 110 and the conveyance device 120 in the T system.
An X-ray tomographic image of the subject is taken by a helical scan.

First, the gantry rotating section 111 inside the gantry device 110 is rotated at a constant rotation speed, and when the rotation speed stabilizes, the subject 123 is placed toward the hollow portion 115 and the top plate held by the table 122. The conveyance of 121 is started. After a predetermined time, when the top plate 121 reaches a position where imaging is started (between X-rays and a rotation plane of the detection unit, which will be referred to as a scan plane hereinafter), the X-ray tube 116 arranged in the gantry rotation unit 111 starts irradiation. At the same time, the detector 117 starts detection.

At this time, it is important whether the rotation angle of the gantry rotating unit 111 (the rotation angle of the gantry rotating unit 111 when the top plate 121 reaches the scan surface) is the optimum imaging start angle of the X-ray tomographic image. Will be. X-ray tomographic image
The X-ray tube 116 and the detector 117, which are attached so as to face the gantry rotating unit 111 with the subject 123 interposed therebetween, relatively rotate once around the subject 123 in a spiral shape, so that One X-ray tomographic image corresponding to the region is reconstructed.

At this time, the reconstructed X-ray tomographic image is added with IQ (correction for improving image quality) corresponding to a predetermined imaging start angle. Therefore, if the imaging start angle is an angle suitable for reconstructing an X-ray tomographic image (hereinafter referred to as an optimum imaging start angle), an X-ray tomographic image with high image quality can be reconstructed. Gantry rotating unit 1 when 121 reaches the position to start shooting
When the rotation angle of 11 is not the optimum imaging start angle of the X-ray tomographic image, the image quality of the X-ray tomographic image is deteriorated.

Therefore, the rotation angle of the gantry rotating unit 111 when the top plate 121 reaches the scan surface, the X-ray tube starts irradiation, and the detector starts detection is
It is desirable that the X-ray tomographic image has an optimum imaging start angle. For this purpose, it is necessary to synchronize the rotation angle of the gantry rotating unit 111 and the position of the top plate 121 in the Z-axis direction.

A conventional method that has been used as a means for achieving such synchronization will be described below with reference to FIGS. 1 to 4.

In FIG. 1, 112 is a gantry rotating unit 1.
The position that is the reference of the rotation angle of 11 is shown. Also, 113
Indicates the current rotation position of the gantry rotation unit 111, and the angle formed by 112 and 113 (that is, the current rotation angle) is θ ₀₀ . Reference numeral 114 indicates the rotation position of the optimum imaging start angle of the X-ray tomographic image.
The angle formed by 14 (that is, the optimum imaging start angle of the X-ray tomographic image) is θ ₀₁ .

At this time, if the rotation speed setting value of the gantry rotating portion 111 is ω ₀ , from the current rotation angle θ ₀₀ ,
The time T _0α required for the gantry rotating unit 111 to rotate to the optimum imaging start angle θ _{01 of the} X-ray tomographic image is T _0α =
It can be expressed by (θ ₀₁ −θ ₀₀ ) / ω ₀ .

On the other hand, in FIG. 1, reference numeral 124 is a top plate 121.
The reference position before the conveyance starts (conveyance reference position)
Numeral 125 indicates a top position (imaging start position) when the scanning plane is reached. _Assuming that the time required for the top plate 121 to move from the transport reference position 124 to the shooting start position 125 is T _0β and the waiting time until the top plate 121 starts transport is T _0wait , the top plate 121 will move to the shooting start position 125. Total time to reach T
_0γ is T _0γ = T _0wait + T _0β . FIG. 2 illustrates such a relationship.

In FIG. 2, the horizontal axis represents time and the vertical axis represents the top speed, and the target speed set value is V _0REF , with the acceleration set value (α ₀ ) after the start of conveyance of the top 121 being constant. It is a figure which shows the speed setting pattern of the top plate 121 in case of.

The top plate 121 has time 0 to time T.
_{0 wait}Transport at 0 speed (that is, stopped state)
At the reference position 124, time T_{0 wait}After acceleration α
₀(Α₀= V _0REF/ (T₀₁-T_{0 wait}))so
Transport starts, time T₀₁Target speed setting value V later_0REF
Reached the constant speed V_0REFBe transported in. did
Therefore, based on the speed setting pattern of the top plate 121,
If the top plate 121 is transported by_0rRear top plate 1
The position of 21 corresponds to the area of the hatched portion 201 in FIG.
It can be obtained more theoretically.

In other words, when the rotation speed setting value ω ₀ of the gantry rotating portion 111, the acceleration setting value α ₀ after the start of the conveyance of the top plate 121, and the target speed setting value V _REF are set to predetermined values, the predetermined time T The position of the top plate 121 after _0r is T
_It depends on _0wait . Therefore, conventionally, T
Gantry rotating unit 11 by _{setting 0wait} to the optimum value
The rotation angle of 1 and the position of the top plate 121 are synchronized. For this purpose, the rotation speed of the gantry rotating unit 111 and the speed of the top plate 121 are controlled as follows.

FIG. 3 is a control block diagram for controlling the rotation speed of the gantry rotating unit 111.

Reference numeral 301 denotes a rotation speed control unit, which outputs an operation amount for a controlled object. Reference numeral 302 represents a transfer function of a control target of a gantry rotation system such as a rotary motor driver or a rotary motor that operates based on an operation amount output from the rotation speed control unit. Further, reference numeral 303 represents a transfer function of the rotation speed detecting encoder, detects a rotation speed which is a control amount, and feeds it back as a rotation speed actual measurement value. The difference between the measured rotation speed fed back and the rotation speed setting value is obtained by the comparator 304, and the difference is used as the input of the rotation speed control unit 301.

With the configuration of the control block diagram, the gantry rotating unit 111 is controlled at a predetermined control cycle so as to rotate at the rotation speed setting value.

FIG. 4 is a control block diagram for controlling the speed of the top plate 121.

Reference numeral 401 denotes a top speed control unit, which outputs an operation amount for a controlled object. Reference numeral 402 represents a transfer function of a control target of a top plate conveyance system such as a top plate motor driver or a top plate motor that operates based on an operation amount output from the top plate speed control unit. Further, 403 represents a transfer function of the encoder for detecting the top speed, and detects the top speed which is a control amount,
It is fed back as a measured value of the top speed. The difference between the fed back measured table speed and the table speed setting pattern is obtained by the comparator 404, and the difference is calculated.
It is input as 1. The top speed setting pattern is
For example, it is the speed setting pattern of the top plate 121 shown in FIG. 2 and changes with time.

With the configuration of the control block diagram, the top 121 is speed-controlled at a predetermined control cycle so as to be conveyed following the top speed setting pattern.

[0021]

However, the actual speed of the top does not always match the top speed setting pattern even if the top speed control as described above is performed.

FIG. 5 shows the actual speed of the top 121 (measured value of the top speed) with respect to the top speed setting pattern. The horizontal axis is time and the vertical axis is the top speed. There is.

_Reference numeral 501 is an example of the top plate speed setting pattern, which is _{ramped up} after the time T _0wait and reaches the target speed set value V _0REF at the time T ₀₁ , after which the top plate is set to a constant value. The speed setting pattern is shown.
On the other hand, the actual speed of the top plate 121 (actually measured top speed 502) follows with a slight delay, and after reaching the target speed set value V _0REF , overshoot occurs and eventually the target speed set value V is reached. Converge to _{0R EF} . This corresponds to each block (401 to 40) in the control block diagram shown in FIG.
3) includes the dead time and the predetermined time constant, respectively.

As a result, the position of the top plate 121 deviates from the theoretical value by the area of the hatched portions 503 and 505 in FIG. 5, and the portion 502 shown in black is painted. The position of the top plate 121 deviates by plus the theoretical value by the area (minus means a direction closer to the transport reference position 124 with respect to the theoretically determined position of the top plate 121, plus). Refers to the direction far). And from the area of 503 and 505, 504
The position of the top plate 121 deviates from the theoretical value by the area obtained by subtracting the area of.

As described above, only by _setting T _0wait to the optimum value, the rotation angle of the gantry rotating part 111 and the top plate 121 can be _adjusted.
Could not be fully synchronized with the position of
An X-ray tomographic image with high image quality could not be obtained.

The present invention has been made to solve the above-mentioned problems, and automatically corrects the rotation speed of the gantry rotating part or the speed setting pattern of the top plate to determine the rotation angle and the top plate position of the gantry rotating part. The purpose is to synchronize with a higher accuracy.

[0027]

In order to solve such a problem, for example, an X-ray CT system of the present invention has the following configuration. That is, a gantry rotating unit for irradiating a subject with X-rays from different angles and performing a scan for detecting transmitted X-rays, and a gantry device capable of controlling the rotation speed of the gantry rotating unit are mounted on a top plate. An X-ray CT system comprising: a transfer device capable of controlling a transfer speed for transferring a placed object to a scan surface of the gantry device, wherein a theoretical top plate position at a predetermined timing is a rotation angle of a gantry rotating part. It is characterized in that the carrying speed setting pattern for carrying speed control of the table is corrected based on the difference between the theoretical table position and the actually measured table position.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(First Embodiment) FIG. 6 shows a first embodiment of the present invention.
2 is a system configuration diagram of an X-ray CT system according to the embodiment of FIG.

As shown in FIG. 6, the system irradiates the subject (patient) with X-rays and transmits X-rays through the placed subject.
A gantry device 620 for detecting a line, and an operation console 600 that performs various settings on the gantry device 620 and reconstructs and displays an X-ray tomographic image based on the data output from the gantry device 620, And a transport device 640 that transports the subject on the gantry device.

A gantry device 620 has the following structure including a main controller 622 which controls the entire device.

Reference numeral 621 denotes an interface for communicating with the operation console 600, reference numeral 633 denotes a gantry rotating unit, and an X-ray tube 624 (driving controlled by the X-ray tube controller 623) and X-ray irradiation are provided inside. Collimator 627 that defines the range, adjustment of slit width that defines the X-ray irradiation range of collimator 627, and collimator 627
A collimator motor 626 for adjusting the position of the Z axis (direction perpendicular to the drawing) is provided. The driving of the collimator motor 626 is controlled by the collimator controller 625.

Further, the gantry rotating part indicated by 633 is
A detection unit 631 that detects X-rays that have passed through the subject, and a data collection unit 630 that collects the data obtained by the detection unit 631 are also provided. X-ray tube 624 and collimator 627
And the detection unit 631 are provided at positions facing each other with the cavity portion 634 sandwiched therebetween, and the gantry rotation unit 633 rotates in a state where the relationship is maintained. This rotation is performed by a rotation motor 629 whose rotation speed is controlled at a predetermined control cycle by a drive signal from the rotation motor controller 628. The gantry rotating unit 63
The rotation speed of 3 is an encoder for rotation speed detection, etc. (not shown)
It should be measured using a known technique of

Further, the carrier device 640 includes a top plate 641 on which the subject is actually placed and a table 6 for holding the top plate 641.
42, the top plate 641 is driven by the top plate motor 643, and the driving of the top plate motor 643 is controlled at a predetermined control cycle based on a drive signal from the top plate motor controller 632. The conveyance speed of the top plate 641 is measured by using a known technique such as an encoder for detecting the top plate speed (not shown).

The main controller 622 has an I / F 62.
1, analyzes the various commands received through the X-ray tube controller 1, and based on the analysis, the X-ray tube controller 623, the collimator controller 625, the rotary motor controller 628,
Various control signals are output to the top plate motor controller 632 and the data collection unit 630. Further, the main controller 622 uses the data collection unit 630.
A process of sending the data collected in step S6 to the operation console 600 via the I / F 621 is also performed. Further, data transmission / reception among various controllers (X-ray tube controller 623, collimator controller 625, rotary motor controller 628, and top plate motor controller 632) is also performed via the main controller 622.

The operation console 600 is a so-called workstation, and as shown in the figure, it stores a CPU 605 which controls the entire apparatus, a boot program, and the like.
An OM 606, a RAM 607 functioning as a main storage device, and the following configuration are provided.

The HDD 608 is a hard disk device in which a diagnostic program for giving various instructions to the OS and the gantry device 620 and reconstructing an X-ray tomographic image based on the data received from the gantry device 620 is stored. Has been done. The VRAM 601 is a memory that expands the image data to be displayed, and by expanding the image data or the like here, it can be displayed on the CRT 602. Reference numerals 603 and 604 are a keyboard and a mouse for making various settings. Further, 609 is an interface for communicating with the gantry device 620.

In the above X-ray CT system, the rotary motor controller 628 and the top plate motor controller 632.
A means for synchronizing the rotation angle of the gantry rotating unit 633 and the position of the top plate 641 by using the main controller 622 will be described below with reference to FIGS. 7 to 9.

In FIG. 7, the same parts as those already shown in FIG. 6 are designated by the same reference numerals, and the description of the same numerals will be omitted.

Reference numeral 701 represents a position serving as a reference for the rotation angle of the gantry rotating portion 633. Reference numeral 702 indicates the current rotation position of the gantry rotation unit 633.
The angle formed by 2 (that is, the current rotation angle) is θ ₀ . Reference numeral 703 denotes a rotation position of the optimum imaging start angle of the X-ray tomographic image, and the angle formed by 701 and 703 (that is, the optimum imaging start angle of the X-ray tomographic image) is θ ₁ .

At this time, when the rotation speed setting value of the gantry rotating unit 633 is ω, the gantry rotating unit 63 is rotated from the current rotation angle θ ₀ to the optimum imaging start angle θ _{1 of the} X-ray tomographic image.
The time T _α required for the rotation of 3 is T _α = (θ ₁ −θ
It can be represented by ₀ ) / ω.

On the other hand, in FIG. 7, reference numeral 704 denotes the subject 70.
6 becomes a reference before the top plate 641 on which the 6 is placed starts to be conveyed.
705 indicates a position (conveyance reference position).
The top position (shooting start position) when it reaches
It is a thing. Shooting start position 70 from the transport reference position 704
The time required for the top plate 641 to move by 5 is T_β,
The waiting time until the top plate 641 starts transportation is T_wait
Then, the top plate 641 reaches the shooting start position 705.
Total time to_γIs T_γ= T_wait+ T _βTona
It FIG. 8 shows such a relationship.

In FIG. 8, the horizontal axis represents time and the vertical axis represents the top plate speed. In the case where the acceleration (α) after the start of conveyance of the top plate 641 is constant and the target speed set value is V _REF. Top 6
It is a figure which shows the speed setting pattern (conveyance speed setting pattern) of 41. From the operation console 600,
The rotation speed setting value ω of the gantry rotation unit 633 and the top plate 64
It is automatically calculated by inputting the acceleration α after the start of conveyance of 1 and the target speed setting value V _REF of the top plate 641.

The top plate 641 has time 0 to time T _wait.
Until the reference position 7
04, and after the time _Twait , the acceleration α (α = V
_REF / (T ₁ −T _wait )) is started and the time T
_The target speed V _REF is reached after 1 and the constant speed V
It is transported by _REF . Therefore, when the top plate 641 is transported based on the speed setting pattern of the top plate 641, the position of the top plate 641 after the time _Tr can be theoretically obtained from the area of the hatched portion 801 in FIG. it can.

The rotation angle θ of the gantry rotating unit 633 at time t can be expressed as θ = ωt (0 ≦ θ ≦ 2π).

Further, the speed v of the top plate 641 at time t
And the position x can be expressed as: 1) v = 0, x = 0 (0 <t <T_wait) 2) v = αt, x = αt^Two/ 2 (T_wait<T <
T₁) 3) v = V_REF, X = V_REFt + α (T₁-T
_wait)^Two/ 2 (t ≧ T ₁) Therefore, the rotation angle θ of the gantry rotating unit 633 and the top plate
The relationship between the position 641 and the position x can be expressed as follows.
It 4) θ = ωt, x = 0 (0 <t <T_wait) 5) x = αθ^Two/ 2 / ω^Two(T_wait<T <T₁) 6) x = αθ / ω (t ≧ T₁) Becomes Diagram showing the relationship from 4) to 6)
Is shown in FIG. In FIG. 10, the horizontal axis indicates the position x of the top plate and the vertical axis indicates
The rotation angle θ of the gantry rotating part is set to
It is called a "top position-rotation angle pattern". Such figure
Is the speed setting pattern described above and the gantry rotating unit 63.
It is automatically calculated based on the rotation speed setting value ω of 3
It

In the X-ray CT system according to the embodiment of the present invention, in controlling the speed of the top plate 641, the rotation angle of the gantry rotating part 633 is fed back and substituted in the above-mentioned "top position-rotation angle pattern". The control method of deriving a theoretical value of the top plate position and, on the other hand, feeding back an actually measured value of the top plate position and adjusting the top plate speed setting pattern by using an error from the theoretical value as a correction value.

FIG. 9 is a control block diagram showing the above control method. Reference numeral 901 denotes a rotation speed control unit, which outputs an operation amount for a control target. Reference numeral 902 represents a transfer function of a control target of a gantry rotation system such as a rotation motor driver or a rotation motor that operates based on an operation amount output from the rotation speed control unit. Further, reference numeral 903 represents a transfer function of the rotation speed detecting encoder, detects the rotation speed which is a control amount, and feeds it back as a measured rotation speed value. The feedback measured rotation speed value is calculated by a comparator 904 to find a difference from the rotation speed set value, and the difference is calculated.
It is input as 1.

With the configuration of the control block diagram, the gantry rotating unit 633 is speed-controlled at a predetermined control cycle so as to rotate at the rotation speed setting value.

Further, the actually measured value of the rotational speed from the encoder for detecting the rotational speed is integrated by the integrator 905, and the actually measured value of the rotational angle of the gantry rotating section 633 is calculated. The actually measured rotation angle θ _MV of the gantry rotation unit 633 calculated by the integrator 905 is input to the “top position-rotation angle pattern” (906), and the theoretical value x _p of the top position is obtained at 906. As described above, FIG. 10 shows a method for obtaining the theoretical value X _p of the top position based on the “top position-rotation angle pattern”, and 1001 shows the relationship between the top position and the rotation angle. It is a theoretical curve. When the rotation angle is θ _{M V} from the theoretical curve 1001 (in the case of point 1002)
The theoretical value x _p of the position of the top plate can be obtained.

On the other hand, reference numeral 910 represents a top speed control unit,
The operation amount for the controlled object is output. Reference numeral 911 represents a transfer function of a control target of a top plate conveyance system such as a top plate motor driver or a top plate motor which operates based on an operation amount output from the top plate speed control unit. Further, reference numeral 912 denotes a transfer function of the encoder for detecting the top speed, detects the top speed as a control amount, and feeds it back as a measured value of the top speed. The fed back measured value of the top speed is input to the comparator 909.

Further, the actually measured value of the top speed from the encoder for detecting the top speed is integrated by the integrator 913 to calculate the actually measured value x _MV of the top position. Measured value of top position x
_MV and theoretical value x _{p of the} tabletop position obtained in 906 above
Is calculated (the distance indicated by the arrow 1003 in FIG. 10 is also determined by the comparator 907), a correction gain is applied to the difference (908), and a correction value based on the difference between the theoretical value of the top position and the actual measurement value is calculated. Input to the comparator 909.

The comparator 909 subtracts the fed back top speed actual measurement value from the input of the top speed setting pattern and adds a correction value based on the difference between the theoretical value of the top position and the actual measurement value. , Its output is used as an input of the top speed control unit 910.

By constructing such a control system, the gantry rotating part 633 and the top plate 641 are not controlled in speed independently of each other, but the rotating angle of the gantry rotating part 633 is monitored and a theoretical value for the rotating angle is calculated. Correct the delay of the measured top speed with respect to the top speed setting pattern for each predetermined control cycle by calculating the top position and adding the result to the feedback loop of the top speed control as a correction value. Is possible.

That is, it is possible to correct the error between the top speed setting pattern and the actual top speed value, and it is possible to synchronize the rotation angle of the gantry rotating part and the top position with higher accuracy. Become.

(Second Embodiment) In the first embodiment, the correction value is added to the top plate speed setting pattern for correction, but a correction value may be added to the rotation speed setting value. .

FIG. 11 is a control block diagram showing this control method. 1101 represents a top speed control unit,
The operation amount for the controlled object is output. Reference numeral 1102 represents a transfer function of a control target of a top plate conveyance system such as a top plate motor driver or a top plate motor that operates based on an operation amount output from the top plate speed control unit. Reference numeral 1103 denotes a transfer function of the encoder for detecting the top speed, which detects the top speed as a control amount and feeds back the measured value as the top speed.
The feedback measured top plate speed value is the comparator 1104.
Then, the difference with the top speed setting pattern is obtained, and the difference is used as the input of the top speed control unit 1101.

With the configuration of the control block diagram, the top plate 641 is speed-controlled at a predetermined control cycle so as to be conveyed in the top-speed setting pattern.

Further, the actually measured value of the top speed from the encoder for detecting the top speed is integrated by the integrator 1105 to calculate the position of the top 641. The actually measured value x _MV of the top position calculated by the integrator 1105 is input to the “top position-rotation angle pattern”, and at 1106, the gantry rotating unit 633.
The theoretical value θ _p of the rotation angle of is obtained.

FIG. 12 shows "top position-rotation angle pattern".
In the figure, 1001 theoretically summarizes the relationship between the top plate position and the rotation angle as described above.
From 01, when the top plate position is X _MV (point 1201
In the case of), the theoretical value θ _p of the rotation angle can be obtained.

Returning to FIG. On the other hand, 1110 represents a rotation speed control unit, which outputs an operation amount for a control target.
Reference numeral 1111 represents a transfer function of a gantry rotation system controlled object such as a rotation motor driver and a rotation motor that operates based on the operation amount output from the rotation speed control unit. Also, 11
12 represents the transfer function of the encoder for detecting the rotation speed,
The rotation speed of the gantry rotating unit 633, which is a control amount, is detected and fed back as an actual rotation speed value. The feedback measured rotation speed of the gantry rotating unit 633 is input to the comparator 1109.

Furthermore, the measured rotation speed value from the rotation speed detection encoder is integrated by the integrator 1113, and the measured rotation angle value θ _{MV of the} gantry rotation unit 633 is calculated. The measured rotation angle θ _{MV of the} gantry rotating unit 633,
The difference from the theoretical value θ _p obtained in the above 1106 is obtained (the distance indicated by the arrow 1203 in FIG. 12 is also found in the comparator 1107), and the difference is multiplied by the correction gain (1108) to rotate the gantry rotating unit 633. The correction value based on the difference between the theoretical value of the angle and the measured value is input to the comparator 1109.

The comparator 1109 subtracts the actually measured value of the fed back rotational speed from the input of the set value of the rotational speed, and also makes a correction value based on the difference between the theoretical value of the rotational angle of the gantry rotating section 633 and the actually measured value. The output is added and the output is used as the input of the rotation speed control unit 1107.

By constructing such a control system, the speed of the gantry rotating unit 633 and the top plate 641 is not controlled independently, but the position of the top plate is monitored and the theoretical gantry rotating unit 633 with respect to the position is monitored. Calculate the rotation angle,
By adding the result as a correction value to the feedback loop of the gantry rotation speed control, it is possible to correct the delay (or advance) of the measured value of the gantry rotation speed with respect to the rotation speed set value.

That is, the speed followability of the top plate 641 can be corrected by changing the rotation speed setting value, and the rotation angle of the gantry rotating part and the top plate position can be synchronized with higher accuracy. It will be possible.

(Third Embodiment) In the first and second embodiments described above, the table 641 may be arranged before or after reaching the scan plane as shown in FIG. 9 or FIG.
Although the control is performed by any one of the control systems shown in FIG. 1, the control may be performed only until the top plate 641 reaches the scan surface. That is, before the top plate 641 reaches the scan surface, it is controlled by either the control system shown in FIG. 9 or FIG. 11, and after reaching the scan surface, it is controlled by the control system (FIGS. 3 and 4) described in the conventional example. You may control. As a result, the rotational speed setting value or the top plate speed setting pattern is corrected at a predetermined control cycle for synchronization before the scan surface arrives, and the constant rotation speed or the top plate speed is obtained after the scan surface arrives. It becomes possible to control.

[0067]

As described above, according to the present invention,
By automatically correcting the rotation speed of the gantry rotating unit or the speed setting pattern of the top plate, it becomes possible to synchronize the rotation angle of the gantry rotating unit and the position of the top plate with higher accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a gantry device and a carrier device in a conventional X-ray CT system.

FIG. 2 is a diagram showing an example of a top plate speed setting pattern in a conventional X-ray CT system.

FIG. 3 is a control block diagram for controlling the rotation speed of a gantry rotating unit in a conventional X-ray CT system.

FIG. 4 is a control block diagram for controlling the speed of a top board in a conventional X-ray CT system.

FIG. 5 is a diagram showing actually measured top plate speed values with respect to a top plate speed setting pattern in a conventional X-ray CT system.

FIG. 6 is an overall system configuration diagram of an X-ray CT system according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a gantry device and a transfer device in the X-ray CT system according to the first embodiment of the present invention.

FIG. 8 is a diagram showing an example of a top speed setting pattern in the X-ray CT system according to the first embodiment of the present invention.

FIG. 9 is a control block diagram in the X-ray CT system according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a top plate position-rotation angle pattern of the X-ray CT system according to the first embodiment of the present invention.

FIG. 11 is a control block diagram in the X-ray CT system according to the second embodiment of the present invention.

FIG. 12 is a diagram showing a top plate position-rotation angle pattern of the X-ray CT system according to the second embodiment of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Aihiko Eguchi             127, 4-7 Asahigaoka, Hino City, Tokyo             GE Yokogawa Medical System Co., Ltd.             Within F-term (reference) 4C093 AA22 BA10 EC42 EC46 ED07                       FA36 FA43 FA54 FA55 FA56

Claims (24)

[Claims] 1. Irradiating a subject with X-rays from different angles,
A gantry device having a gantry rotating part for performing a scan for detecting transmitted X-rays and capable of controlling the rotation speed of the gantry rotating part, and an object mounted on a top plate are conveyed to a scan surface of the gantry device. An X-ray CT system including a transport device capable of controlling a transport speed, wherein a theoretical top position at each predetermined timing is derived from a rotation angle of a gantry rotating part, and the theoretical top position is actually measured. An X-ray CT system characterized by correcting a carrying speed setting pattern for controlling the carrying speed of the top plate based on a difference from a plate position. 2. A conveyance speed setting pattern for controlling the conveyance speed of the top plate, a rotation speed set value of the gantry rotating part, a set value of the conveyance acceleration of the top plate, and a target speed of the top plate. The X-ray CT system according to claim 1, wherein the X-ray CT system is calculated based on a set value and a top plate position when the scan surface is reached. 3. The relationship between the top plate position and the rotation angle of the gantry rotating part is calculated based on a conveyance speed setting pattern of the top plate and a rotation speed setting value of the gantry rotating part. The X-ray CT system according to claim 2. 4. The rotation speed control of the gantry rotating unit is performed based on a difference between a rotation speed setting value of the gantry rotating unit and a measured rotation speed value of the gantry rotating unit. X-ray CT system. 5. The X-ray according to claim 4, wherein the conveyance speed control of the top plate is performed based on a difference between a conveyance speed setting pattern of the top plate and a measured conveyance speed of the top plate. CT system. 6. The X-ray CT system according to claim 5, wherein in the conveyance speed control of the top plate, the correction of the conveyance speed setting pattern is performed until the top plate reaches the scan surface. . 7. The subject is irradiated with X-rays from different angles,
A gantry device having a gantry rotating part for performing a scan for detecting transmitted X-rays and capable of controlling the rotation speed of the gantry rotating part, and an object mounted on a top plate are conveyed to a scan surface of the gantry device. An X-ray CT system including a transfer device capable of controlling a transfer speed, wherein a theoretical rotation angle of a gantry rotating part at predetermined timing is derived from a top plate position, and the theoretical rotation angle of the gantry rotating part is determined. And a rotational speed setting value for controlling the rotational speed of the gantry rotating unit is corrected based on the difference between the measured rotational angle of the gantry rotating unit and X.
X-ray CT system. 8. A conveyance speed setting pattern for controlling the conveyance speed of the tabletop, a rotation speed set value of the gantry rotating unit, a set value of the conveyance acceleration of the tabletop, and a target speed of the tabletop. The X-ray CT system according to claim 7, wherein the X-ray CT system is calculated based on a set value and a top plate position when the scan surface is reached. 9. The relationship between the top plate position and the rotation angle of the gantry rotating part is calculated based on a transfer speed setting pattern of the top plate and a rotation speed setting value of the gantry rotating part. The X-ray CT system according to claim 8. 10. The rotation speed control of the gantry rotating unit is performed based on a difference between a rotation speed setting value of the gantry rotating unit and a measured rotation speed value of the gantry rotating unit. X-ray CT system. 11. The X-ray according to claim 10, wherein the conveyance speed control of the top plate is performed based on a difference between a conveyance speed setting pattern of the top plate and an actually measured conveyance speed of the top plate. CT system. 12. In the rotation speed control of the gantry, the correction of the rotation speed set value is performed until the top plate reaches the scan surface.
X-ray CT system described in. 13. A gantry device having a gantry rotating part for irradiating a subject with X-rays from different angles and performing a scan for detecting transmitted X-rays, and a gantry device capable of controlling the rotation speed of the gantry rotating part, A control method in an X-ray CT system, comprising: a transfer device capable of controlling a transfer speed for transferring an object placed on a plate to a scan surface of the gantry device, wherein a theoretical top plate position for each predetermined timing is determined. Derived from the rotation angle of the gantry rotating unit, and based on the difference between the theoretical top position and the actually measured top position, the transfer speed setting pattern for controlling the transfer speed of the top is corrected. And a control method in the X-ray CT system. 14. A transfer speed setting pattern for controlling the transfer speed of the top plate, a rotation speed set value of the gantry rotating part, a set value of the transfer acceleration of the top plate, and a target speed of the top plate. The control method in the X-ray CT system according to claim 13, wherein the calculation is performed based on a set value and a top plate position when the scan surface is reached. 15. The relationship between the position of the top plate and the rotation angle of the gantry rotating portion is determined by the transfer speed setting pattern,
The control method in the X-ray CT system according to claim 14, wherein the calculation is performed based on a rotation speed setting value of the gantry rotation unit. 16. The rotation speed control of the gantry rotating unit is performed based on a difference between a rotation speed setting value of the gantry rotating unit and an actual measurement value of the rotation speed of the gantry rotating unit. Control method in the X-ray CT system. 17. The X-ray according to claim 16, wherein the conveyance speed control of the top plate is performed based on a difference between a conveyance speed setting pattern of the top plate and an actually measured conveyance speed of the top plate. Control method in CT system. 18. The method of correcting the transport speed setting pattern for controlling the transport speed of the top plate until the top plate reaches a scan surface.
7. The control method in the X-ray CT system according to 7. 19. A gantry device having a gantry rotating unit for irradiating a subject with X-rays from different angles and performing a scan for detecting transmitted X-rays, and a gantry device capable of controlling the rotation speed of the gantry rotating unit, A control method in an X-ray CT system, comprising a transport device capable of controlling a transport speed for transporting an object placed on a plate to a scan surface of the gantry device, the method comprising: A rotation speed for deriving a rotation angle from the top plate position and controlling the rotation speed of the gantry rotation unit based on the difference between the theoretical rotation angle of the gantry rotation unit and the measured rotation angle of the gantry rotation unit. A control method in an X-ray CT system, characterized by correcting a set value. 20. A conveyance speed setting pattern for controlling the conveyance speed of the tabletop, a rotation speed set value of the gantry rotating part, a set value of the conveyance acceleration of the tabletop, and a target speed of the tabletop. The control method in the X-ray CT system according to claim 19, wherein the calculation is performed based on a set value and a top plate position when the scan surface is reached. 21. The relationship between the top plate position and the rotation angle of the gantry rotating part is calculated based on a conveyance speed setting pattern of the top plate and a rotation speed setting value of the gantry rotating part. The X-ray CT according to claim 20.
Control method in the system. 22. The rotation speed control of the gantry rotating unit is performed based on a difference between a rotation speed setting value of the gantry rotating unit and an actual measurement value of the rotation speed of the gantry rotating unit. Control method in the X-ray CT system. 23. The X-ray according to claim 22, wherein the conveyance speed control of the top plate is performed based on a difference between a conveyance speed setting pattern of the top plate and an actually measured conveyance speed of the top plate. Control method in CT system. 24. The rotation speed set value for controlling the rotation speed of the gantry rotating unit is corrected until the top plate reaches a scan surface. A control method in an X-ray CT system.