WO2018020946A1

WO2018020946A1 - X-ray ct device

Info

Publication number: WO2018020946A1
Application number: PCT/JP2017/023856
Authority: WO
Inventors: 悠太鈴木; 光明尾形
Original assignee: 株式会社日立製作所
Priority date: 2016-07-28
Filing date: 2017-06-29
Publication date: 2018-02-01
Also published as: JP2018015296A

Abstract

Provided is an x-ray CT device, comprising: a rotating part whereupon an x-ray source and an x-ray detection device are mounted; an encoder signal generating unit which generates an encoder signal by detecting holes in an encoder tape which is attached to the rotating part; and an encoder signal comparison unit which receives input of the encoder signal and compares the encoder signal with a normal encoder signal. The encoder signal comparison unit identifies a cause of an anomaly from the inputted encoder signal and the normal encoder signal (S103, S106, S109), stores information of the identified cause of the anomaly in a storage medium (S105, S108), and carries out an error display (S112).

Description

X-ray CT system

The present invention relates to an X-ray CT apparatus, and in particular to a technique for identifying an encoder abnormality.

X-ray CT (Computed Tomography) equipment detects the transmitted X-ray dose by irradiating X-rays from around the subject carried in the opening of a rotating disk with an X-ray source and X-ray detector facing each other. Is a device that collects the spatial distribution of transmitted X-rays as digital data.

This X-ray CT apparatus collects data at a specific angle, but the data collection timing is determined based on a data acquisition signal (hereinafter referred to as a view trigger signal) synchronized with the rotation of the rotating disk. In order to generate the view trigger signal, in the X-ray CT apparatus, for example, an encoder tape provided with holes at regular intervals is attached around the rotating disk, and the position of the hole is read by a sensor provided in the stationary part, A method of generating a signal (hereinafter referred to as an encoder signal) synchronized with the rotation of the turntable is used.

The view trigger signal is generated by the encoder signal. When the encoder signal and the view trigger signal are generated using the encoder tape and the sensor as described above, foreign matter is mixed in the hole of the encoder tape, or the encoder tape is blocked. The encoder signal cycle is shifted or lost due to an abnormality such as damage to the sensor or the sensor being shifted, resulting in an abnormality in the view trigger signal. In this case, there is a problem that the image quality of the generated image is deteriorated because the data cannot be taken in at the timing that should be collected. In order to solve such a problem, in Patent Document 1, image quality deterioration is prevented by a method of correcting transmission data itself, and in Patent Document 2 of a method of correcting an acquisition timing signal of transmission data.

Japanese Patent Laid-Open No. 10-155785

JP 2011-245195 A

However, Patent Document 1 and Patent Document 2 are methods for correcting abnormal data or signals, and have not performed identification of the cause of the abnormality. For this reason, the cause of the abnormality cannot be specified until it is visually confirmed at the time of maintenance work, and the maintenance time becomes longer. As a result, the time during which the apparatus is down is also prolonged.

An object of the present invention is to provide an X-ray CT apparatus capable of solving the above-described problems and identifying the cause of an abnormality in an encoder.

In order to achieve the above object, in the present invention, an X-ray CT apparatus having a rotating part on which an X-ray detector that detects a transmitted X-ray dose that is disposed opposite to an X-ray source and transmits a subject is mounted. An encoder signal generation unit that generates an encoder signal by detecting a hole in an encoder tape attached to the rotation unit, an encoder signal generated by the encoder signal generation unit, and a rotation set for the rotation unit An encoder signal comparison unit that compares a normal encoder signal calculated based on the speed, and the encoder signal comparison unit identifies the cause of the encoder signal abnormality from the comparison result of the encoder signal and the normal encoder signal. A line CT system is provided.

According to the present invention, it is possible to provide an X-ray CT apparatus that can identify the cause of the abnormality of the encoder.

The figure which shows the example of whole structure of the X-ray CT apparatus concerning each Example Schematic diagram for explaining an example of encoder tape abnormality Waveform diagram for explaining examples of encoder signal abnormalities Schematic diagram for explaining the HOME hole of the encoder tape The figure which shows the processing flow of the X-ray CT apparatus of Example 1. Schematic diagram showing the sensor part of the X-ray CT apparatus of Example 2 Waveform diagram showing the output of each sensor of the X-ray CT apparatus of Example 2 The figure which shows the processing flow of the X-ray CT apparatus of Example 2. The figure which shows the processing flow of the X-ray CT apparatus of Example 3. The figure which shows the processing flow in the case of providing the additional sensor of the X-ray CT apparatus of Example 3. The figure for demonstrating the cleaning process of the X-ray CT apparatus of Example 3.

Embodiments of an X-ray CT apparatus to which the present invention is applied will be described with reference to the drawings.

Fig. 1 shows one configuration of an X-ray CT apparatus commonly used in each embodiment. The X-ray CT apparatus 1 includes a scanner 2, a bed 3, and a console 4. The scanner 2 includes a stationary part 208, a turntable 202, and a slip ring 206. The stationary unit 208 is equipped with a scanner control device 209 and a rotation sensor 210 that functions as an encoder signal generation unit. The scanner control device 209 is controlled by a system control device 403 provided in the console 4.

The turntable 202 is equipped with an X-ray tube 201, an X-ray detector 207, a high-pressure control device 203, a rotation control device 205, and an encoder tape 204, and rotates around the subject. The X-ray tube 201 is a device that continuously or intermittently irradiates the subject placed on the bed 3 with X-rays. The X-ray detector 207 is arranged opposite to the X-ray tube 201 and collects the spatial distribution of transmitted X-rays as digital data by detecting the X-ray dose transmitted through the subject. The elements are arranged in the rotation direction of the turntable 202, or are arranged two-dimensionally in the rotation direction of the turntable 202 and the rotation axis direction.

The high voltage generator 203 applies or supplies a tube voltage and an X-ray tube current to the X-ray tube in accordance with the X-ray conditions determined by the system controller 403 provided in the console 4. The rotation control device 205 controls the turntable 202 based on a control signal from the scanner control device 209 controlled by the system control device 403 provided in the console 4. The encoder tape 204 is composed of a sheet metal attached to the outer periphery of the rotating disk 202, and the sheet metal is provided with holes at equal intervals.

この This hole is detected by the rotation sensor 210 to generate an encoder signal. For the rotation sensor 210, for example, a laser displacement meter or the like is used. The generated encoder signal is output to the scanner control device 209. The slip ring 206 transmits electric power and a control signal between the stationary part 208 and the rotating disk 202. The bed 3 places the subject on the top and moves up and down and back and forth.

The console 4 includes a display device 401, an input device 402, a system control device 403, an image processing device 404, and a storage device 405. The display device 401 is a device that displays the CT image created by the image processing device 404. The input device 402 is a device for inputting the name of the subject, examination date and time, imaging conditions, and the like. The system control device 403 is a device that controls these devices, the scanner control device 209, the rotation control device 205, and the control device for the bed 3. The image processing apparatus 404 is an apparatus that performs CT processing on the measurement data sent from the X-ray detector 207 and performs CT image reconstruction.

The storage device 405 is a device that records data collected by the X-ray detector 207 and image data of a CT image created by the image processing device 404. The console 4 can be composed of a normal personal computer. This console 4 may be connected to the scanner 2 via a network such as a LAN (Local Area Network), or measurement data collected by the X-ray detector 207 via the network such as the LAN. May be sent to a computer in the data center, and the data center may perform arithmetic processing. Hereinafter, various embodiments of the present invention using the configuration of the X-ray CT apparatus of FIG. 1 will be described.

Embodiment 1 is an embodiment of an X-ray CT apparatus that can identify an abnormality of an encoder signal and the cause of the abnormality. That is, an X-ray CT apparatus having a rotating part on which an X-ray detector that is disposed opposite to the X-ray source and detects a transmitted X-ray dose that passes through the subject is mounted, and is attached to the rotating part An encoder signal generation unit that generates an encoder signal by detecting a hole in the encoder tape, an encoder signal generated by the encoder signal generation unit, and a normal speed calculated based on the rotation speed set for the rotation unit An X-ray CT apparatus is provided that includes an encoder signal comparison unit that compares encoder signals, and the encoder signal comparison unit identifies the cause of the abnormality of the encoder signal from the comparison result of the encoder signal and the normal encoder signal.

As shown in FIG. 2, abnormal encoder signals are generated due to clogging 212 of holes 211 provided at equal intervals in encoder tape 204 (b), or due to damage 213 of encoder tape 204 (c). There is a case (d) due to the positional deviation 214 of the rotation sensor 210 ((a) when normal). The rotation sensor 210 functioning as an encoder signal generation unit that generates an encoder signal outputs “1”, for example, when passing through holes 211 provided at equal intervals on the encoder tape 204, and outputs “0” otherwise.

As shown in FIG. 3, in the case of a normal encoder signal 215, “1” and “0” are regularly arranged and output. When such an abnormality occurs in the hole 211, the output from the rotation sensor 210 is different from the normal encoder signal 215. For example, the portion that was “1” at normal time becomes “0”, and the portion that was “0” becomes “1”. FIG. 3 schematically shows an example of the encoder signal 216 when clogging occurs, the encoder signal 217 when damage occurs, and the encoder signal 218 when sensor deviation occurs.

In this way, the cause of the abnormality can be identified by comparing the current output with the normal output in the scanner control device 209 that functions as an encoder signal comparison unit that compares the encoder signal with the normal encoder signal. .

Further, as shown in FIG. 4, the encoder tape 204 is provided with holes 219 for indicating the home (HOME) separately from the holes 211 provided at equal intervals. Using this HOME hole as a reference, it is possible to determine the number of holes in which an abnormality has occurred from the reference position, and the angle on the disk can be calculated therefrom. By storing this angle information, it is possible to quickly confirm at which position the hole is abnormal during maintenance. The normal encoder signal 215 is calculated using the period of the encoder signal obtained from the rotation speed set in advance for the turntable 202. Further, the position of the hole 219 for indicating the home may be used.

Next, a method for identifying the cause of abnormality in the first embodiment will be described using the processing flow of FIG. After the processing is started, it is determined whether the output of the rotation sensor 210 is normal or abnormal (S101). The determination is performed by comparing the normal encoder signal and the encoder signal output from the rotation sensor 210 by the encoder signal comparison unit of the scanner control device 209. The scanner control device 209 including the encoder signal comparison unit can be realized by executing a program of a central processing unit (CPU) including a memory and the like, and normal encoder signal data is stored in the memory in advance.

The scanner control device 209 performs normal processing (S102) when the determination result in S101 is normal (Yes).

If the judgment result is abnormal (No), the process proceeds to a specific flow of the cause of abnormality (S103, S106, S109). When clogging occurs, as shown in the encoder signal 216, compared to a normal signal, “0” is output at the position where “1” should be output. It is specified that there is (S103). After identification, the angle is calculated from the reference HOME hole position and the position of the clogged hole (S104). The cause of the abnormality is clogged and linked to the angle information and stored in the storage device 405 such as a storage medium (S105). An error is displayed on the display device 401 and the process is terminated (S112).

When the encoder tape 204 is damaged, the encoder signal 217 is longer than the normal signal when the original “1” is output, that is, the signal width becomes longer. Compared with the normal signal, “1” is output at the position where “0” is supposed to be output. Therefore, the difference is identified as the difference (S106). After identification, the same processing as clogging is performed to calculate the angle (S107). The cause of the abnormality is regarded as breakage, and is stored in the storage device 405 in association with the angle information (S108). An error is displayed on the display device 401 and the process is terminated (S112).

If the position deviation of the rotation sensor 210 has occurred, comparing the encoder signal 218 with the normal waveform in the scanner control device 209 shows that there is a deviation in the period of the encoder signal. It is determined whether the rotation sensor 210 is partly misaligned or not (S109). That is, in S109, when the period deviation is the whole (Yes), it is determined as a sensor position deviation. Since the positional deviation of the rotation sensor 210 does not require information such as an angle, the abnormality cause is stored in the storage device 405 as the positional deviation of the rotation sensor 210 (S110). In other cases (No), the cause of the abnormality is stored as unknown in the storage device 405 (S111). An error is displayed on the display device 401 and the process is terminated (S112).

According to the configuration of the present embodiment, an X-ray CT apparatus that can easily check the cause of an abnormality and its position can be provided.

In Example 1, only one rotation sensor 210 is used to identify the cause of an abnormal encoder signal being generated. In Example 2, a sensor for detecting a hole in the encoder tape is further added. An embodiment of an X-ray CT apparatus that can identify the cause of abnormality with higher accuracy by the encoder signal comparison unit of the scanner control apparatus 209 will be described. That is, in Example 2, the encoder signal generation unit includes a rotation sensor that generates an encoder signal and a newly added additional sensor, and the encoder signal comparison unit uses the output signal of the additional sensor in addition to the encoder signal. This is an embodiment of the X-ray CT apparatus configured to identify the cause of the abnormality. In this embodiment, a case where a magnetic sensor for detecting magnetism is used as an additional sensor will be described with reference to FIGS.

FIG. 6 schematically shows a configuration in which a sensor B221 that is a magnetic sensor is added to the sensor A220 corresponding to the rotation sensor 210 of the first embodiment and juxtaposed. This sensor B221 is a sensor that functions as an additional sensor, and is installed in the stationary portion 208 so as to pass through holes 211 provided at equal intervals in the encoder tape 204, similarly to the sensor A220. Similarly to the sensor A220, the sensor B221 outputs “1” when passing through the hole 211 on the encoder tape 204, and outputs “0” otherwise. Foreign matter that closes the hole in the encoder tape 204 is dust or the like, and foreign matter such as dust is detected by an optical sensor such as a laser displacement meter, but is not a substance that inhibits magnetism. Therefore, the sensor A220 outputs “0” when the hole 211 is closed, but the sensor B221 outputs “1”. In this specification, the sensor A220 may be referred to as a first sensor and the sensor B221 may be referred to as a second sensor.

When the sensor A220 and the sensor B221 are separated from each other by one hole 211, as shown in FIG. 7, when the sensor A220 is acquiring the nth signal 223, the sensor B221 is (n-2) That is, the first signal 224 is acquired. Therefore, the scanner control device 209 generates a comparison signal 225 (hereinafter referred to as sensor B ′ signal) obtained by shifting the signal 224 acquired by the sensor B221 by two, and outputs the signal 223 of the sensor A220 and the sensor B ′ signal 225. Compare.

As shown in FIG. 7, the (n + 2), (n + 5), and (n + 6) th signals are missing in the signal 223 of the sensor A220, but the output is obtained in the sensor B ′ signal 225. . Whether or not the sensor B 'signal 225 is normal can be determined by comparison with the normal signal used in identifying the cause of the abnormality in the first embodiment. Therefore, as a result of comparing the sensor B ′ signal 225 with the normal signal, when the sensor B ′ signal 225 is normal, the (n + 2), (n + 5), and (n + 6) -th holes 211 are blocked with a substance such as dust. Judge that it is peeled off and identify the cause of the abnormality as “clogged”. The process after the identification is as shown in the process flow of FIG.

As shown in FIG. 8, when the signal 223 of the sensor A220 is “0” and the sensor B ′ signal 225 that is the output of the sensor B221 is “1” (Yes), the cause of the abnormality is clogged. (S203), and the angle is calculated from the hole position of the reference HOME and the position of the hole where the abnormality is detected (S204). The cause of the abnormality is clogged and associated with the angle information and stored in the storage device 405 such as a storage medium (S205). An error is displayed on the display device 401 and the process is terminated (S212).

In case of damage, it takes longer time for both sensors to output “1”. Therefore, if the signal 223 of the sensor A220 is “1” and the sensor B ′ signal 225 is “1” and there is a difference from the normal signal (Yes), the cause of the abnormality is identified as damage (S206). ). That is, in S206, the encoder signal comparison unit determines whether or not the cause of the abnormality is breakage of the encoder tape using the encoder signal, the output signal of the additional sensor, and the normal encoder signal. After the determination, the same processing as clogging is performed to calculate the angle (S207). The cause of the abnormality is determined to be broken, and is stored in the storage device 405 in association with the angle information (S208). An error is displayed on the display device 401 and the process is terminated (S212).

If NO (No) in S206, the width and period of the signal 223 of the sensor A220 and the width and period of the sensor B 'signal 225 are compared, and if there is a difference between the two, the position of the sensor A220 or sensor B221 is shifted. (S209). After the determination, the abnormality is regarded as a positional deviation of the sensor A220 or the sensor B221 that is the rotation sensor 210, and is stored in the storage device 405 (S210). An error is displayed on the display device 401 and the process is terminated (S212). In other cases, the cause of the abnormality is stored as unknown in the storage device 405 (S211). An error is displayed on the display device 401 and the process is terminated (S112).

According to the present embodiment, by adding a sensor and comparing the signals obtained from each sensor, it is possible to specify with high accuracy whether the cause of the abnormality is clogged, broken, or misaligned. An X-ray CT apparatus that can be performed can be provided.

Embodiment 3 is an embodiment of an X-ray CT apparatus provided with an automatic cleaning unit that realizes an automatic cleaning function for clogging in addition to an abnormality detection function, that is, further includes an automatic cleaning unit for cleaning an encoder tape hole, This is an example of an X-ray CT apparatus configured such that when the signal comparison unit determines that the cause of the abnormality is clogged encoder tape hole, the automatic cleaning unit cleans the encoder tape hole determined to be clogged.

Damage to the encoder tape 204 and misalignment of the rotation sensor 210 are difficult if the operator actually goes to the site and does not perform the work, but in the case of clogging, this will be explained in Examples 1 and 2. It is possible to recover without maintenance by adding an automatic cleaning function using a configuration in which the detected abnormal position is detected and the angle is calculated and stored. The flow up to the detection of the abnormality is the same as in the first and second embodiments. In the third embodiment, as an example of the automatic cleaning function, an automatic cleaning unit equipped with a cleaning brush (hereinafter referred to as a brush) that is movable by motor control is added as shown in FIGS. The processing flow will be described with reference to FIG.

Hereinafter, the case of applying to the configuration of the first embodiment will be described with reference to FIG. 9, and the case of applying to the configuration of the second embodiment will be described with reference to FIG. An automatic cleaning unit including a brush that is movable by motor control (not shown) is mounted on the stationary unit 208. Normally, the brush is retracted to a position where it does not contact the encoder tape 204. When the cause of the abnormality is identified as clogged (Yes in S303 and S403), as shown in FIG. 11, the brush of the automatic cleaning unit moves to a position where it can contact the encoder tape 204 by motor control (S501) and is detected. Clean the hole in position. After cleaning, the brush of the automatic cleaning unit is again retracted to a position where it does not come into contact with the encoder tape 204 by motor control (S502), and the rotation sensor 210 is rotated again so that it passes through the hole where the abnormality is detected (S502). S503), the output of the rotation sensor 210 after cleaning is confirmed (S504). If normal output is obtained by cleaning, the process is terminated. The motor (not shown) is controlled by a scanner control device 209 including an encoder signal comparison unit, like the rotary disk 202 and the like.

If the scanner control device 209 including the encoder signal comparison unit is abnormal even if it is cleaned by the automatic cleaning unit, it is determined that it is not clogged (S505), and the breakage or rotation sensor is detected according to the procedure of the first and second embodiments. If 210 is identified (S306, S309, S406, S409), and if it is identified as broken, the position of the abnormal location is detected based on HOME, and the angle is calculated (S307, S407). The cause of the abnormality is determined to be broken, and is associated with the angle information and stored in the storage device 405 such as a storage medium (S308, S408). An error is displayed on the display device 401, and the process ends (S312, S412). If it is determined that the position of the rotation sensor 210 is misaligned, the cause of the abnormality is the position misalignment of the rotation sensor 210, which is stored in the storage device 405 (S310, S410). In other cases, the cause of the abnormality is set as unknown and stored in the storage device 405 (S311, S411). An error is displayed on the display device 401 and the process is terminated (S312, S412).

According to the X-ray CT apparatus of this embodiment, it is possible to identify the cause of the abnormality such as whether the cause of the abnormality is clogged, damaged, or sensor misalignment, and automatic cleaning in the case of clogging. It is possible to provide an X-ray CT apparatus capable of automatically cleaning a hole clogged in a part.

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included.

For example, the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. For example, instead of the angle information indicating the abnormal location, a number indicating the number of the abnormal hole from the reference position may be stored as the positional information of the abnormal location of the abnormal hole.

Further, the above-described configuration, function, control device, image processing device, and the like have been described as an example of creating a computer program that realizes part or all of them. Needless to say, it may be realized by hardware.
That is, all or part of the functions of the image processing apparatus may be realized by an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA) instead of the program.

1 X-ray CT device, 2 scanner, 201 X-ray tube, 202 turntable, 203 high pressure control device, 204 encoder tape, 205 rotation control device, 206 slip ring, 207 X-ray detector, 208 stationary part, 209 scanner control device , 210 rotation sensor, 211 hole, 212 clogging, 213 damage, 214 sensor displacement, 215, 216, 217, 218 encoder signal, 219 HOME detection hole, 220, 221 sensor A, B, 3 bed, 4 console, 401 display device, 402 input device, 403 system control device, 404 image processing device, 405 storage device

Claims

An X-ray CT apparatus having a rotating part on which an X-ray detector for detecting a transmitted X-ray dose that is disposed opposite to the X-ray source and transmits the subject is mounted,
An encoder signal generating unit that generates an encoder signal by detecting a hole in the encoder tape attached to the rotating unit;
An encoder signal comparison unit that compares the encoder signal generated by the encoder signal generation unit with a normal encoder signal calculated based on a rotation speed set for the rotation unit;
The encoder signal comparison unit
An X-ray CT apparatus, wherein a cause of abnormality of the encoder signal is specified from a comparison result between the encoder signal and the normal encoder signal.
The X-ray CT apparatus according to claim 1,
The encoder signal generation unit includes a sensor that detects the hole,
The encoder signal comparison unit
An X-ray CT apparatus characterized by identifying at least one of the clogging of the hole, damage to the encoder tape, and displacement of the sensor as the cause of the abnormality.
The X-ray CT apparatus according to claim 1,
The encoder signal generation unit includes a first sensor that detects dust and a second sensor that does not detect dust,
The X-ray CT apparatus, wherein the encoder signal comparison unit identifies the cause of abnormality based on a comparison result between an output signal of the first sensor and an output signal of the second sensor.
The X-ray CT apparatus according to claim 1,
An automatic cleaning unit for cleaning the hole;
The automatic cleaning unit, when the encoder signal comparison unit identifies the cause of the abnormality as clogging of the hole, cleans the hole identified as clogging.
The X-ray CT apparatus according to claim 3,
The X-ray CT apparatus, wherein the second sensor is a magnetic sensor.
The X-ray CT apparatus according to claim 2,
The encoder tape is provided with a hole indicating a home separately from the hole detected by the sensor,
The encoder signal comparison unit
An X-ray CT apparatus, wherein an abnormal location of the hole is specified based on a relative position between a position of the hole indicating the home and a position of the hole where the cause of the abnormality is specified.