JP2924134B2 - Medical imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention relates to an X-ray CT apparatus, a nuclear magnetic resonance tomography apparatus,
The present invention relates to a medical imaging device represented by a gamma camera device and the like, and more particularly, to a technique for aligning an imaging target portion of an object with an imaging position.

B. Conventional technology An X-ray CT device is taken as an example of a medical imaging device.
A description will be given below of the conventional alignment between the imaging target portion of the subject and the imaging position.

The X-ray CT apparatus includes a gantry section in which an X-ray imaging system such as an X-ray tube and an X-ray detector is inserted, and an imaging table on which a subject is placed and sent into the gantry section. The position is the imaging center position of the X-ray CT apparatus.

Assuming that the imaging target site of the subject is, for example, the head, the head of the subject lying on the imaging table is controlled in the vertical and horizontal movements of the imaging table so that the head is located at the center of the gantry. If the head is to be photographed in an oblique direction, the target part and the photographing position are aligned by inclining the gantry.

Regarding the movement control of the imaging table and the gantry unit, the operator (or the operator) performs empirical judgments when performing a movement operation, or taking a fluoroscopic image of the subject in advance and using the fluoroscopic image to determine the position of the target part. May be calculated, and the position may be automatically adjusted based on the relative relationship between the calculated position of the target part and the photographing position.

In addition, not only the above-mentioned X-ray CT apparatus but also a nuclear magnetic resonance tomography apparatus, a gamma camera apparatus, and the like, similarly control the movement of the imaging table and the imaging apparatus main body to align the target part with the imaging position. Is going.

C. Problems to be Solved by the Invention However, when a simple control by ON / OFF of a drive motor is performed for movement control for a relatively heavy object such as the inclination of the gantry part and the vertical movement of the imaging table. And high alignment accuracy could not be expected. Conversely, in the movement control for a relatively light object such as a horizontal movement of the shooting table, advanced control of changing the movement speed as the set position is approached is performed. If it is used for tilting the gantry or moving the shooting table up and down, it will constitute a rather large-scale device,
Practical application was difficult.

Therefore, for example, when automatically tilting the gantry section by 10 degrees, when the tilt angle of the gantry section reaches 10 degrees, a simple control of stopping the drive motor is performed. In some cases, the gantry part stops at a position slightly deviated from the set angle, and a problem arises in that accurate positioning cannot be performed.

Also, when the operator controls the drive motor ON / OFF by himself, the operator performs the operation while paying attention so that the subject does not come into contact with the gantry part or the like. Yes, there is a large deviation from the set position.

The present invention has been made in view of such circumstances, and provides a medical imaging apparatus capable of improving the positioning accuracy of a device whose positioning is performed simply by ON / OFF control of a drive motor. It is an object.

D. Means for Solving the Problems The present invention has the following configuration to achieve the above object.

That is, the present invention includes a moving mechanism for mutually moving a main body provided with an imaging device and an imaging table on which the subject lies supine by ON / OFF control of a drive motor. In a medical imaging apparatus for performing position adjustment, a coasting amount storage unit that stores in advance a coasting movement amount of a main body or an imaging table by the moving mechanism, and a position detection unit that detects a position of the main body or the imaging table during movement in real time. And a stop position obtained by subtracting the inertial movement amount from a preset target position, and turning off the drive motor of the moving mechanism when the position information output from the position detection unit matches the stop position. And a control unit.

E. Function According to the present invention, by turning on the drive motor of the moving mechanism and operating it, the movement of the photographing main body or the photographing table is started, and the position detection unit outputs position information during movement to the control unit in real time. I do.

On the other hand, the control unit reads out the coasting amount by the moving mechanism from the coasting amount storage unit, and obtains a stop position obtained by subtracting the coasting amount from the preset target position. Then, the position information output from the position detection unit is compared with the stop position, and when the both match, the drive motor of the moving mechanism is turned on.
Turn off to stop driving.

As a result, the moving mechanism stops before the target position by the amount of inertial movement, and then moves by the inertial force to reach the target position.

F. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Also in this embodiment, an X-ray CT apparatus is taken as an example of a medical imaging apparatus as in the conventional example, and in particular, alignment of the inclination angle of the gantry will be described.

First, the outline of the tilting mechanism of the gantry will be described with reference to the perspective view of FIG. 3 and the cross-sectional view of FIG.

The gantry unit 1 has a through hole 2 for inserting a subject (not shown) at a substantially central portion of the front surface, and supports the gantry unit 1 on both side surfaces so as to be rotatable around the X axis. The supporting frame 5 is attached.

A vertically movable imaging table 3 is provided on a floor surface facing the front of the gantry section 1, and a bed 4 on which an object is placed is provided on the upper surface of the imaging table 3 so as to be horizontally movable.

As shown in the cross-sectional view of FIG. 4, a sector gear 6 centered on the X-axis and a gear 7 meshing with the sector gear 6 are connected to the bottom surface of the gantry part 1. A reduction gear 8 is provided, and the reduction gear 8 penetrates the bottom surface of the gantry portion 1 and is meshed with an output gear 10 of a drive motor 9 installed in the support frame 5. These components correspond to the moving mechanism in the present invention.

When the drive motor 9 rotates, the rotating power is reduced by the reduction gear 8,
The gantry unit 1 is transmitted to the sector gear 6 via the gear 7, and is configured to rotate around the X-axis, that is, to tilt in the front-rear direction together with the sector gear 6.

In addition, a potentiometer 12 as a position detection unit for detecting the inclination angle of the gantry unit 1 is mounted on a rotation shaft 11 that rotatably supports the gantry unit 1 with respect to the support frame 5 (FIG. 3). ), And the output of potentiometer 12 is configured to be output to the control system shown in the block diagram of FIG.

Next, the position setting of the inclination angle of the gantry 1 will be described with reference to the control block diagram of FIG.

First, the operator inputs a set angle and specifies the type of device from the console 20 (operation console). The input set angle is output to the differentiator S1, and the device type designation information is output to the arithmetic processing unit 25. This arithmetic processing unit 25
And a comparator H, which will be described later, correspond to a control unit according to the present invention.

Here, the type of the device is specified because the amount of inertia is slightly different depending on the type of the drive motor and the gear provided in various medical imaging devices, and by specifying the type of the corresponding device, This is for setting the inertia amount suitable for the device.

That is, in this control system, information of the inertia amount corresponding to various devices is stored in advance, and this is a memory table indicated by reference numeral 28 (corresponding to the inertia amount storage unit in the present invention). ).

The memory table 28 is a two-dimensional table that stores the relationship between the amount of inertia and the speed (in this example, the angular speed for positioning the tilt angle) determined by an experiment, and includes a plurality of tables corresponding to various devices. It is composed of Expressing an example of the contents of the memory table 28 in a graph format,
As second illustrated, with an increase in angular speed V [theta], and has a tendency also increases inertia weight theta _D. Note that the slope of the curve of this graph varies depending on various devices.

The ROM 27 stores the correspondence between the number of each memory table 28 and the corresponding device type (registered by device number) in a table format.

Therefore, when the type of device is specified from the console 20, the arithmetic processing unit 25 determines the number of the specified device, gives the device number as a read address to the ROM 27, and sends the corresponding memory table 28 Receive the number. Next, the memory table 28 of that number is read, and the information of the memory table 28 is transferred to the RAM 26 provided inside.

The above is the process corresponding to the pre-processing stage. Next, when the operator starts the drive motor 9, the positioning control of the gantry unit 1 is performed as follows.

When the gantry unit 1 starts the tilting operation with the start of the drive motor 9, the potentiometer 12 sets the tilt angle θ _i
And outputs this angle information to the A / D converters 21a and 21b. The angle data θ _i converted into digital data by the A / D converter 21a is output to the differentiator S1. As described above, the data of the set angle θ ₀ is given to one of the differentiators S1, and the differentiator S1 calculates the difference data of the set angle θ ₀ and the current inclination angle θ _i of the gantry unit 1, that is, the remaining angle data theta _n outputs to the comparator H in real time _{(θ n = | | θ i} -θ 0).

On the other hand, the tilt angle θ _i of the gantry unit 1 given to the A / D converter 21b is digitized according to a pulse signal for each set time (t ₀ ) output from the clock pulse generator 22,
Temporarily stored in the register R _1. When the data of the tilt angle θ _{i + 1} digitized at the next pulse signal output timing (t ₀ + t ₀ = t ₁ ) is output to the register R ₁ , the data is first stored in the register R _1. The tilt angle θ _i is transferred to the register R ₂ , and the next tilt angle θ _{i + 1} is newly stored in the register R ₁ .

Therefore, the registers R ₁ and R ₂ register the data of the inclination angle that changes every set time, and these two data are output to the differentiator S2.

The difference device S2 outputs the difference data between the two data, that is, the inclination angle Vθ of the gantry unit 1 at the set time, and the angular velocity Vθ is given to the arithmetic processing unit 25.

The arithmetic processing unit 25 gives the input angular velocity Vθ as a read address to the RAM 26 (to which the information on the angular velocity and the inertia of the corresponding device is transferred), and provides an inertia (an angle shifted by inertia) corresponding to Vθ. ) reads theta _D, and outputs the theta _D to the comparator H.

One of the comparator H, since the remaining angle data theta _n output from the differentiator S1 to the real time as described above has been entered, its remaining angle data theta _n, inertia weight theta _D
The comparator H outputs a “Hi level” signal as a stop signal to the drive motor 9 at the point of time when it is equal to.

That is, as in the conventional case, the inclination angle θ _i of the gantry 1
Does not stop the drive motor 9 at the point in time when the angle θ reaches the set angle θ ₀ (θ _i = θ ₀ ), and subtracts the angle θ _{D corresponding} to the inertial movement from the set angle θ ₀ (θ _i = θ ₀ −
When θ _D ) is reached, the drive motor 9 is stopped.

Therefore, after the drive motor 9 stops, the angle at which the gantry unit 1 stops after the gantry unit 1 moves due to the inertial force is the set angle θ _0.
As in the conventional case, accurate positioning can be performed with simple control of turning on / off the drive motor 9.

In the above embodiment, the inclination angle θ _{i of the} gantry unit 1 is set.
From has led to inertia amount theta _D, this was added angular acceleration, it may be guided inertia weight.

That is, the relationship between the experimentally obtained angular velocity and angular acceleration and the amount of inertia is stored in the memory table 28, and this is used as a three-dimensional table, and the angular velocity output from the differentiator S2 is stored at certain time intervals. Angular acceleration is obtained by sampling and subtracting them, and an angular velocity and an angular acceleration are given as read addresses to a three-dimensional table to derive an inertia amount.

As described above, by obtaining the amount of inertia according to the speed and the acceleration, a more accurate amount of inertia can be obtained, and the accuracy of positioning can be increased.

In the embodiment, the tilt position adjustment of the gantry unit 1 has been described. However, the present invention is not limited to this. For example, a memory table is similarly prepared for the vertical movement of the imaging table 3 to perform accurate movement control. be able to. This is the same for the other medical imaging apparatuses described in the conventional example.

Further, in the embodiment, the drive motor 9 is started manually by the operator. However, this is also applicable to the case where the drive motor 9 is automatically started.

G. Effects of the Invention As is clear from the above description, the medical imaging apparatus according to the present invention stores in advance the amount of inertial movement of the imaging body or the imaging table by the moving mechanism, and calculates the amount of inertial movement from the target position. Since the movement of the main body or the imaging stand is stopped at the difference position, when they are moved by inertia force, control is performed to reach the target position.

Therefore, it is possible to perform high-precision movement control even though it is simple control of ON / OFF of the movement mechanism, and to avoid upsizing of the device when a complicated (advanced) control mechanism is installed. It is possible to improve the alignment accuracy between the target part of the subject and the imaging position.

[Brief description of the drawings]

1 to 4 relate to an embodiment of the present invention, FIG. 1 is a block diagram of a control system, FIG. 2 is a graph showing a relationship between an amount of inertial movement and an angular velocity, and FIG. 3 is an X-ray. FIG. 4 is a perspective view showing a schematic configuration of the CT apparatus, and FIG. 4 is a partial sectional view schematically showing a moving mechanism. 1 gantry section 3 photographic table 12 potentiometer 25 arithmetic processing section 28 memory table

Claims (1)

(57) [Claims] A moving mechanism for moving a main body on which the imaging apparatus is provided and an imaging table on which the subject lies supine by ON / OFF control of a drive motor; In a medical imaging apparatus that performs positioning, a coasting amount storage unit that stores in advance a coasting movement amount of the main body or the imaging table by the moving mechanism, and a position detection unit that detects a position of the main body or the imaging table during movement in real time. A stop position obtained by subtracting the amount of inertial movement from a preset target position, and turning off the drive motor of the moving mechanism when the position information output from the position detection unit matches the stop position. And a medical imaging device.