JPH08215184A - Medical x-ray device - Google Patents

Abstract

PURPOSE: To materialize the positional, detection of a X-ray tube measured with a high accuracy at low cost in the medical X-ray device which is provided with a drive source at its one section, and is so constituted that its equipment moving section can be moved to a specified position. CONSTITUTION: The device is provided with an equipment moving section (X-ray tube) 21 or an equipment set-up environment or the stationary section of the device, that is, a positional information obtaining means 210 which is provided, for example, for a wall, and obtains information representing the position of the X-ray tube, and with a position operating means 211 which obtains a deviation between the information representing the position given by the position information obtaining means 210 and the positional information of a specified position, and thereby operates the position of the X-ray tube 21 with respect to the wall.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medical device in which a part of the apparatus, such as a bed, an X-ray irradiating means, an image receiving means, a display means, etc., has a drive source and is movable to a predetermined position by a control means. The present invention relates to improvement of an X-ray apparatus.

[0002]

2. Description of the Related Art A medical X-ray apparatus represented by an X-ray fluoroscopy table and a circulatory organ X-ray inspection apparatus is indispensable in the field of diagnosis, but the diagnosis is diversified and advanced. ,
Along with this, various functions are required. For this reason, the medical X-ray apparatus becomes complicated and large-scaled, and there is a problem of increased cost and reduced reliability.

Recently, it has been used not only for diagnosis but also for treatment. This treatment is carried out under fluoroscopy, for example, by inserting a catheter with various instruments attached to the tip into the subject, and suffers from the pain caused by the conventional surgical treatment to the subject. Can be reduced
Moreover, since it has a great merit that it can be treated at low cost, it is rapidly spreading. Such treatment method is IV
It is called R (Interventional Radiology). In this IVR, the failure of the X-ray device may directly affect the life of the subject, so the reliability required for the device is higher than that used for diagnosis.

An apparatus shown in FIG. 8 has been proposed as a medical X-ray apparatus suitable not only for such diagnosis but also for IVR. That is, the X-ray tube 21, which is an X-ray irradiator, and the image receiving device 23, which converts the transmitted X-rays of the subject (not shown) into an electric signal and is composed of II, a TV camera, or the like, are mechanically separated. It is composed. In this case, the image receiving device 23 is movably supported by a supporting device 24 provided on the ceiling 100, and the X-ray tube 21 is attached to the carriage 22.
Is mounted on the floor and can be moved on the floor by the carriage 22.

Further, the X-ray tube 21 and the image receiving device 23 can be positioned by a positioning means (not shown), and the X-ray tube 21 and the image receiving device 23 are placed on the top plate of the bed 20 for lying the subject. It is made movable so as to be always opposed to each other with the 20a in between. Although not shown in FIG. 8, display means for displaying an image based on an electric signal from the image receiving device 23 is also provided.

Hereinafter, the carriage 22 and the image receiving device 23 will be described.
The supporting device 24 will be described in detail. FIG. 9 corresponds to FIG.
FIG. 9A is a diagram showing an example of a traveling system of a portion A in FIG. 8, that is, the carriage 22, in which FIG.
(B) is a view showing (a) from above, and (c) is (b).
It is the figure which showed the figure from the left.

In FIG. 9, 30 is a carriage 22.
Is the bottom frame. The wheel 31 is rotatably supported by a wheel frame 32 integrally formed with a shaft 45, and is rotatably supported by the frame 30 by thrust bearings 39 and 40. A pulley 50 is provided on the shaft 45. Four sets of such wheel support mechanisms are provided.

That is, a wheel frame 34 that rotatably supports the wheels 33, thrust bearings 41 and 42 that rotatably support the wheel frame 34, a shaft 46 integral with the wheel frame 34, and a shaft 46. A wheel support mechanism including a pulley 51 provided in the wheel frame 37 also integrally supports the wheel frame 37 that rotatably supports the wheels 36, thrust bearings 43 and 44 that rotatably support the wheel frame 37, and the wheel frame 37. Wheel support mechanisms including a shaft 47 and a pulley 53 provided on the shaft 47 are respectively provided, and the wheel 35 and the pulley 5 are further provided.
2 is also supported by the same structure.

The pulleys 50, 51, 52 and 53 provided on the wheels 31, 33, 35 and 36 can be rotated by a belt 54 in an interlocking manner. This belt 54
Is hung on a pulley 57 provided on a speed reducer 58 via pulleys 55 and 56. A carriage direction changing drive motor 59 is attached to the speed reducer 58. Further, carriage driving motors 71, 73 are provided on the wheels 33, 36 via speed reducers 70, 72.

In the traveling system of the carriage 22 configured as described above, the direction of the wheels 31, 33, 35, 36 is changed by rotating the carriage direction changing drive motor 59, and the moving direction of the carriage 22 is changed. be able to. Further, the carriage 22 runs by driving the carriage driving motors 71 and 73. In addition,
The control means for the carriage direction changing drive motor 59 and the carriage drive motors 71 and 73 will be described later.

10A and 10B are views showing an example of the supporting device 24 of the image receiving device 23. FIG. 10A is a partially cut front view and FIG. 10B is a side view. In FIG. 10, rails 101a and 101
b is fixed to the ceiling 100 and has an X-axis direction carriage 104.
Wheels 102a, 102b, 103a, 103b (10
2b is not shown).

The X-axis direction carriage 104 includes a gear 106.
The column X-axis direction driving motor 105 having
Rack 107 and gear 1 fixed to the rail 101a
06 meshes with each other. Further, rails 108a and 108b are fixed to the X-axis direction carriage 104, and wheels 109a and 109 of the Y-axis direction carriage 111 are fixed.
b, 110a, 110b (109b is not shown) are fitted.

The Y-axis direction carriage 111 includes a gear 113.
The motor 112 for driving the column Y-axis direction having
Rack 11 fixed to the rails 108a and 108b
4 and the gear 113 mesh with each other. Furthermore, Y
A column 120 is fixed to the axial carriage 111.

A motor 122 for vertically driving the support column and a speed reducer 123 thereof are built in the support column 120 and the roller 1
25, 126, 127, 128, 129, 130 are attached. These rollers 125, 126, 12
Reference numerals 7, 128, 129, and 130 guide a column 121 to which the image receiving device 23 is attached, and the column 121 is suspended by a wire 124 of the speed reducer 123.

The supporting device 24 constructed as described above is
By driving the column X-axis direction driving motor 105 by the control device described later, the columns 120 and 121, that is, the image receiving device 23 moves in the X direction. Further, by driving the support Y-axis direction driving motor 112 by the control device described later, the support 120, 121, that is, the image receiving device 23.
Moves in the Y direction. Further, by driving the up-and-down direction driving motor 122 by the control device described later, the up-column 121, that is, the image receiving device 23 moves in the Z direction.
With these, the image receiving device 23 can be moved to an arbitrary position.

FIG. 11 shows each motor 5 in FIGS. 9 and 10.
9, 71, 73, 105, 112, 122 control device,
That is, it is a block diagram of a medical X-ray device including a positioning control device for the X-ray tube 21 and the image receiving device 23.

As can be seen from FIG. 11, the column X-axis direction driving motor 105 and the column Y-axis direction driving motor 11
2. The column up / down driving motor 122 is driven by motor control devices 150, 151 and 152, respectively, and the position and speed of the motors 105, 112 and 122 are instructed by the system controller 200. That is, the system controller 200 allows the image receiving device 23 to move to an arbitrary position.

Numerals 153, 154 and 155 are the columns X.
Axial drive motor 105, column Y-axis direction drive motor 112, and column up-and-down direction drive motor 122 are separately connected. By driving these motors 105, 112 and 122, column X-axis movement and column Y-axis direction movement are performed. , A mechanism for moving the column up and down. Also, 156, 157, 1
Reference numeral 58 denotes a column X-axis direction driving motor 105, a column Y-axis direction driving motor 112, and a column vertical direction driving motor 12.
The motors 105, 1 attached to the respective rotary shafts of 2
The encoders 12 and 12 respectively detect the rotational positions of the rotary shafts.

Further, the carriage direction changing drive motor 5
9. The carriage driving motors 71 and 73 are driven by motor control devices 159, 160 and 161, respectively.
The positions and speeds of the motors 59, 71, 73 are commanded by the system controller 200. That is, by the system controller 200, X
The wire tube 21 can be moved to any position.

163 is a carriage driving motor 7
This is a mechanism that is connected to the motors 1 and 73 and drives the motors 71 and 73 to move the carriage. Again 162
Is connected to a carriage direction changing drive motor 59,
A mechanism for changing the carriage movement direction by driving the motor 59. Further 164, 165, 166
Is an encoder attached to each rotation shaft of the carriage direction changing drive motor 59 and carriage drive motors 71 and 73, and detects the rotational positions of the rotation shafts of the motors 59, 71 and 73, respectively.

Further, the motor control devices 150-152, 1
59 to 161 are controlled by a command from the system controller 200 so that the X-ray tube 21 and the image receiving device 23 are always opposed to each other. X-ray tube 21 and image receiving device 23
The detection of the facing position with respect to each motor 59,71,73,1
Encoder 15 attached to 05, 112, 122
The system controller 200 to which the positional information from 6 to 158 and 164 to 166 is given performs.

In the illustrated configuration, the high voltage generator 167 is also controlled by a command from the system controller 200, and controls the high voltage applied to the X-ray tube 21 to control the X-rays. The X-rays pass through the subject 1 on the tabletop 20a, are converted into electric signals by the image receiving device 23, are converted into digital signals by the A / D converter 170, and are then given to the image processing device 171. To be In the image processing device 171, the digital signal is processed into image data that is easy to see, and the image data is converted into an analog signal by the D / A converter 173 through the display gradation processing device 172 and is displayed by the display 174 which is a display means. It is designed to be displayed as an image. The display 174 is supported by the support mechanism 175 from the ceiling 100.

With the above-described structure, the operator (not shown) can switch the switch 20 of the system controller 200.
1, 202 to operate the carriage 22 and the image receiving device 23.
The position of can be controlled to move while the X-ray tube 21 and the image receiving device 23 are always kept facing each other, and the X-ray can be controlled.

According to the medical X-ray apparatus constructed as described above, there are no obstacles around the top plate 20a, and the top plate 20a is eliminated.
The subject 1 on a can be easily approached from any direction. Further, since the X-ray tube 21 is located below the subject 1, the upper part of the subject 1 becomes X-rays that have passed through the subject 1, so that the operator is less exposed to X-rays. It is extremely useful in performing IVR.

[0025]

In the medical X-ray apparatus constructed as described above, the X-ray tube 21 and the image receiving apparatus 23 are sensors capable of detecting the origin somewhere within the moving range in order to specify their positions. Is it necessary to provide an (origin detection sensor) and operate to detect the origin?
Encoder 1 attached to 3, 105, 112, 122
56, 157, 158, 164, 165, 166 must be expensive absolute type ones. If the current position cannot be detected accurately, collisions may occur between the moving parts of the X-ray apparatus, or the moving parts may collide with the operator or subject, which is extremely dangerous.

Since the carriage 22 runs on the floor with some slip (idling), it is necessary to frequently detect the origin when the origin detecting sensor is provided.
Also, the encoders 156, 157, 158, 164, 1
When absolute type 65 and 166 are used, the position may not be specified.

Regarding the support device 24 of the image receiving device 23,
Since a rack is usually used for driving the same, it does not slide like the carriage 22, but an operation for detecting the origin is necessary.

These are moving parts of the circulatory organ X-ray inspection apparatus shown in FIG. 12 and the X-ray fluoroscopy table shown in FIG. 13 (bed top plate 300, C arm 301, X-ray tube 302, image receiving device 303, C). Arm support device 304, bed 310,
Basically the same applies to the X-ray tube supporting device 311).

As described above, in the conventional medical X-ray apparatus having the moving part, the accuracy of the means for detecting the position of the moving part is low, the reliability is lowered, or the cost is increased. There was a problem.

It is an object of the present invention to provide a medical X-ray apparatus capable of accurately detecting the position of a moving part at low cost and improving the reliability of the apparatus.

[0031]

The above object is at least a movable component of a medical X-ray apparatus which has a driving source at least in part and is configured to be movable to a predetermined position by the control means. A position information acquisition unit that is provided in the moving unit or the device installation environment or the stationary unit of the device and acquires information indicating the position of the moving unit with respect to the device installation environment or the stationary unit of the device, and the position from the position information acquisition unit. This is achieved by providing position calculation means for calculating the deviation between the information represented and the position information of the predetermined position to calculate the position of the moving part with respect to the device installation environment or the stationary part of the device.

[0032]

When a part of the device such as the bed, the X-ray irradiating means, the image receiving means, the display means, etc. is moved by the drive source, the position information acquisition means causes the position information acquisition means to move to
Information indicating the position of the moving part with respect to the stationary part of the device, such as a wall, a ceiling or a pillar, a stationary part of the device installation environment or a part that does not move in the device constituent part, for example, a non-driving part of a bed leg is acquired. Further, the position calculation means obtains a deviation between the information indicating the position from the position information acquisition means and the position information of the movement destination (predetermined position) of the moving part with respect to the device installation environment of the moving part or the stationary part of the device. Calculate the position.
As a result, the position of the moving unit can be detected without the need to search for the origin position, and high position accuracy can be obtained at low cost.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a medical X-ray apparatus according to the present invention. In FIG. 1, reference numeral 210 denotes a position information acquisition unit which is provided at least in the moving part of the device or in the device installation environment or the stationary part of the device and which acquires information indicating the position of the moving part with respect to the device installation environment or the stationary part of the device. is there. Reference numeral 211 denotes information indicating the position from the position information acquisition means 210 and the moving destination (predetermined position) of the moving unit.
Position calculation means for calculating the position of the moving part with respect to the device installation environment or the stationary part of the device by obtaining the deviation from the position information. In addition, in FIG. 1, the same reference numerals as those in FIG. 11 denote the same or corresponding portions.

Here, the moving parts of the apparatus are the X-ray tube 21 (carriage 22), the image receiving apparatus 23, and the top plate 20 of the bed 20.
Like a, etc., it means a movable component in the medical X-ray apparatus, and the stationary part of the apparatus installation environment means the floor, wall, ceiling or pillar of the room in which the apparatus is installed. The stationary portion of the apparatus refers to a portion that does not move in the constituent parts of the apparatus, for example, a non-driving portion of the leg portion 20b of the bed 20.

The position information acquisition means 210 is, for example, a PSD (Position Sensitive) as shown in FIG.
A distance sensor (light-use distance sensor) 224 including a Detector) element 220, a light projector 221 including an infrared light emitting diode, and lenses 222 and 223 is used. In the distance sensor 224, after being emitted from the projector 221 and being focused by the lens 223, the light reflected by the environment in which the device is installed or the stationary portion 225 of the device is reflected by the lens 222 and applied as spot light to the PSD element 220. As a result, the distance L to the stationary portion 225 can be measured.

That is, when the spot light is incident on the surface of the P layer of the PSD element 220, the distance sensor 224 outputs a current having a value corresponding to the incident position from the electrode. In other words, the relationship between the output current value of the PSD element 220 and the distance D in the figure is known, and θ in the figure is also known.
The distance L to the stationary portion 225 is calculated by L = Dtan θ.

Such distance sensors 224 are provided at a plurality of locations around the moving part of the apparatus, for example, the traveling system part of the carriage 22 (X-ray tube 21) as shown in FIG. FIG.
, 224a to 224c indicate the distance sensors. 226 is a wall that is a stationary part of the environment in which the device is installed, 2
27 is a non-driving portion of the bed leg portion 20b which is a stationary portion of the apparatus.

Under the illustrated conditions, the distance sensors 224a ...
A signal representing the distances L1 and S1 is obtained from 224c. Here, the wall 226 and the non-driving portion 2 of the bed leg 20b
Since 27 are both stationary parts, and their absolute positions are known, the distances L1 and S from the distance sensors 224a to 224c are shown.
The position calculation means 211 can calculate the position of the carriage 22 by a signal representing 1.

In FIG. 3, three distance sensors 224 (224
a to 224c) are provided. This is because when the carriage 22 is tilted with respect to the wall 226 as shown in FIG. 4, the tilt is calculated by performing geometric calculation based on the measured values L2, L3, S2 of the distance sensors 224a to 224c. This is because the angle can also be obtained. Two (224a, 224b) may be provided if it is not necessary to obtain the tilt angle, or two are similarly provided on the distance sensor 224c side so that the tilt angle of the carriage 22 with respect to the non-driving portion 227 can also be found. Good.

The position calculation means 211 obtains the deviation between the information indicating the position from the position information acquisition means 210 and the position information of the predetermined position as described above, and determines the installation environment of the moving part or the stationary part of the device. The position of the moving portion, here, the calculated position of the carriage 22 is given to the system controller 200.

The system controller 200 receives the position information (actual position) of the carriage 22 from the position calculation means 211, compares this with the position command value of the carriage 22, finds a deviation, and cancels the deviation. A position command is given to the motor control devices 159 to 161, and the carriage 2
2 position compensation is performed.

Further, the system controller 200 receives the position information (actual position) of the carriage 22 from the position calculation means 211 and holds it in advance and the stationary part (2).
26, 227) and the carriage 22
From colliding with the stationary part (226, 227).

It should be noted that the deviation may be obtained by the position calculating means 211, given to the system controller 200, and a position command given from the system controller 200 to each of the motor control devices 159 to 161 so as to cancel the deviation. Good.

Switch 2 of system controller 200
By operating 01 and 202, the positions of the carriage 22 and the image receiving device 23 are controlled to move while the X-ray tube 21 and the image receiving device 23 are always held in the opposed state, and the X-ray control is possible. It is similar to the case of 11.

FIG. 5 is a plan view showing a second example of the position information acquisition means 210. Here, the position information acquisition means 210 is composed of light projectors 230 and 232 and light detection means 231 and 233 in which a plurality of optical sensors are linearly arranged. In this case, the light projector 230 is on the wall 226, the light projector 232 is on the non-driving portion 227 of the bed leg 20b, and the light detecting means 231 and 233 are on the carriage 22 (X-ray tube 2).
They are provided around the traveling system part of 1).

According to this, the light emitted from the projectors 230 and 232 is incident on the light detecting means 231 and 233.
That is, the light incident position (the position of the light sensor) on the light detecting means 231 and 233 becomes the position information of the carriage 22.

The positions of the light projectors 230 and 232 and the light detection means 231 and 233 may be reversed. Further, the number of light projectors and the number of photosensors forming the photodetector are not limited to those shown in the drawings. For example, if another light projector is provided on the wall 226 side separately from the light projector 230 at a constant interval, the inclination angle of the carriage 22 with respect to the wall 226 can be obtained as in the example of FIG.

FIG. 6 is a partially enlarged perspective view showing the third example of the position information acquiring means 210. Here, the position information acquisition means 210 is composed of a magnetic sensor 240 and a mesh-shaped magnetic body 241. In this case, the magnetic sensor 240 is provided at an appropriate position around the traveling system portion of the carriage 22, and the mesh-shaped magnetic body 241 is fixed by covering the floor 242 of the room in which the device is installed or the floor 242. It is embedded in the sheet 243. In this example, the magnetic sensor 240 has a mesh-shaped magnetic body 241.
Is detected and the position information of the carriage 22 is detected by the magnetic sensor 24.
You get it from zero.

In addition, as the position information acquiring means 210, an ultrasonic wave emitting means and an ultrasonic wave detecting means for detecting an ultrasonic wave emitted from the ultrasonic wave or a reflected wave thereof may be used. As described above, the position information acquisition means 21
It is considered that 0 is practically one using light, magnetism, and ultrasonic waves, but is not limited to this.

Further, in the above embodiment, the case where the position information acquisition means 210 is provided in the carriage 22 and the position information of the carriage 22 is directly acquired has been described.
Other than 2, for example, the image receiving device 23, the top plate 20 of the bed 20
a, if the display 174 as a display means is movable, the position information acquisition means 21 is displayed on the display 174 or the like.
The position of the carriage 22 may be indirectly obtained (relative position acquisition) from the calculated position by providing 0. In this case, the image receiving device 23 and the bed 2
The moving parts of the device, such as the top plate 20a of 0 and the display 174, have their positions calculated based on the stationary part of the device whose absolute position is known, for example, the floor or wall of the room in which the device is installed.

Further, as shown in FIG. 7, the position information acquisition means 210 and the position calculation means 211 may be provided in each of the carriage 22 and the image receiving device 23. In this case, the same effect as the above-mentioned embodiment can be obtained. To be Further, the position calculation means 21
The configuration of the control system that controls each part of the device based on the position information calculated in 1 is not limited to the examples of FIGS. 1 and 7.

The traveling system of the carriage 22, the support device 24 of the image receiving device 23, the positioning control device of the X-ray tube 21 and the image receiving device 23, and the like are not limited to the configurations of the above embodiments. Further, in the above-described embodiment, the carriage 22 is configured to be freely movable on the floor, but may be configured to be movable on the rail. Further, the image receiving device 23 is not limited to the configuration of II and the television camera as in the above-described embodiment. The present invention is also applicable to the circulatory organ X-ray inspection apparatus shown in FIG. 12 and the X-ray fluoroscope shown in FIG.

[0053]

As described above, according to the present invention, it is possible to realize the position detection of the moving part of the apparatus such as the bed, the X-ray irradiating means, the image receiving means, the display means, etc. at low cost and with high precision,
There is an effect that the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a device of the present invention.

FIG. 2 is a P used as a position information acquisition unit in FIG.
It is a structure explanatory view of a light utilization distance sensor provided with an SD element.

3 is a plan view showing an example of position information acquisition means in FIG. 1. FIG.

FIG. 4 is a plan view showing an example of position information acquisition means in FIG.

FIG. 5 is a plan view showing a second example of the position information acquisition means in FIG.

6 is a partially enlarged perspective view showing a third example of the position information acquisition means in FIG. 1. FIG.

FIG. 7 is a block diagram showing another embodiment of the device of the present invention.

FIG. 8 is a perspective view showing a conventional device.

9 is a diagram showing an example of a portion A (a carriage traveling system) in FIG.

10 is a diagram showing an example of a supporting device of the image receiving device in FIG.

FIG. 11 is a block diagram of a conventional device.

FIG. 12 is a perspective view showing a conventional circulatory organ X-ray inspection apparatus.

FIG. 13 is a front view showing a conventional X-ray transparent table.

[Explanation of symbols]

1 subject 20 bed 20a bed top plate (moving part) 20b bed leg part (stationary part) 21 X-ray tube (X-ray irradiating means; moving part) 22 carriage (moving part) 23 II, image reception consisting of TV camera, etc. Device (moving part) 24 Supporting device for image receiving device 59 Carriage direction changing drive motor 71, 73 Carriage driving motor 100 Ceiling (stationary part) 105 Strut X-axis direction driving motor 112 Strut Y-axis direction driving motor 122 Strut up / down Direction driving motors 150 to 152, 159 to 161 Motor control device 153 Support X axis direction moving mechanism 154 Support Y axis direction moving mechanism 155 Support vertical movement mechanism 156 to 158, 164 to 166 Encoder 162 Carriage moving direction changing mechanism 163 Carriage Moving mechanism 200 System controller 201, 202 System Arm controller switch 224,224a~224c light available distance sensor 225 to the stationary portion 226 wall non-driving portion of the (stationary portion) 227 Bed legs (stationary portion)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mariko Miyamoto 1-1-14 Kanda, Chiyoda-ku, Tokyo Inside Hitachi Medical Co., Ltd.

Claims (2)

[Claims] 1. A medical X-ray apparatus, at least a part of which has a drive source and is configured to be movable to a predetermined position by a control means, at least a movable section or apparatus installation environment or apparatus which is a movable component thereof. Position information acquisition means provided in the stationary part of the device for acquiring information indicating the position of the moving part with respect to the installation environment of the device or the stationary part of the device, and information indicating the position from the position information acquisition means and the predetermined position. A medical X-ray apparatus comprising: a position calculation unit that calculates a deviation from position information and calculates the position of the moving unit with respect to the device installation environment or the stationary unit. 2. The position information acquisition means is a light utilization position information acquisition means comprising a light emission means and a light detection means or an ultrasonic wave utilization position comprised of an ultrasonic wave emission means and an ultrasonic wave detection means provided in the moving section. Information acquisition means, or at least one of the magnetic utilization position information acquisition means including a magnetic body provided on the installation environment or the floor of the stationary part of the device and a magnetic detection means provided on the moving part. The medical X-ray apparatus according to claim 1, which is an information acquisition unit.