WO2016084567A1 - X-ray ct apparatus and control method therefor - Google Patents

X-ray ct apparatus and control method therefor Download PDF

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Publication number
WO2016084567A1
WO2016084567A1 PCT/JP2015/081134 JP2015081134W WO2016084567A1 WO 2016084567 A1 WO2016084567 A1 WO 2016084567A1 JP 2015081134 W JP2015081134 W JP 2015081134W WO 2016084567 A1 WO2016084567 A1 WO 2016084567A1
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signal
encoder
unit
ray
rotation
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PCT/JP2015/081134
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French (fr)
Japanese (ja)
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涼介 土田
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株式会社日立製作所
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Priority to JP2016561473A priority Critical patent/JP6577487B2/en
Publication of WO2016084567A1 publication Critical patent/WO2016084567A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]

Definitions

  • the present invention relates to an X-ray CT apparatus, and more particularly to a technique for correcting an encoder signal generated in synchronization with rotation of a rotating unit.
  • X-ray CT Computer Tomography
  • X-ray CT equipment is an intensity of transmitted X-rays by irradiating X-rays from around a subject carried in an opening of a rotating part arranged with an X-ray source and an X-ray detector facing each other.
  • an encoder tape provided with slits at equal intervals is attached around the rotating part, and the position of the slit is read by a sensor provided in the stationary part, thereby synchronizing with the rotation of the rotating part.
  • a pulse hereinafter referred to as an encoder signal
  • the encoder signal is used for communication control between the rotating unit and the stationary unit and generation of a transmission timing control signal (hereinafter referred to as a view trigger signal) of transmitted X-ray data.
  • Patent Document 1 a method of correcting a missing encoder signal has been devised.
  • the period is calculated from the encoder signal input immediately before, the input timing of the next encoder signal is predicted, and the missing encoder signal is corrected by generating a dummy signal.
  • Patent Document 1 correction can be performed only when the period of the encoder signal is constant, that is, when the rotating part is rotating at a constant speed, and the period of the encoder signal is changed, that is, at the time of acceleration / deceleration of the rotating part. No consideration was given to the correction of the encoder signal.
  • An object of the present invention is to solve the above problems and provide an X-ray CT apparatus capable of correcting a missing encoder signal even during acceleration / deceleration of a rotating unit.
  • an X-ray source and an X-ray detector arranged to face the X-ray source and detecting an X-ray detector that transmits a transmitted X-ray through the subject
  • An encoder signal generation unit that generates an encoder signal that is synchronized with the rotation of the encoder
  • a control unit that outputs a control signal for controlling the rotation unit based on a correction signal that is input with the encoder signal and corrects the encoder signal.
  • the X-ray CT apparatus is configured to calculate a rotation speed change of the rotation unit from the input encoder signal, predict a signal change timing of the next encoder signal, and generate a correction signal at the predicted signal change timing.
  • an X-ray CT apparatus capable of correcting missing encoder signals even during rotation acceleration / deceleration of the rotating unit.
  • FIG. 4 is a time chart for explaining an encoder signal correction process according to the first embodiment. Flowchart for explaining an encoder signal correction process according to the first embodiment. The flowchart figure for demonstrating the detail of the prediction process based on Example 1. FIG. The flowchart figure for demonstrating the detail of the prediction process based on Example 2. FIG. The figure for demonstrating the control system based on Example 3. The flowchart figure for demonstrating the detail of the prediction process based on Example 3. FIG. The flowchart figure for demonstrating the detail of the prediction process based on Example 4. FIG.
  • the X-ray CT apparatus includes an X-ray source and a rotating unit 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 a subject is mounted; and the rotating unit
  • An encoder signal generation unit that generates an encoder signal synchronized with the rotation of the encoder, and a control unit that outputs a control signal that controls the rotation unit based on a correction signal that is input with the encoder signal and corrects the encoder signal.
  • the controller calculates a rotation speed change of the rotating unit from the input encoder signal, predicts a signal change timing of the next encoder signal, and generates the correction signal at the predicted signal change timing It is characterized by.
  • control unit includes an encoder correction unit that receives the encoder signal and generates the correction signal.
  • the encoder correction unit rotates the rotation unit from the encoder signal that is continuously input until immediately before.
  • the correction signal is generated by calculating a speed change rate and predicting the signal change timing.
  • the rotational speed change rate is calculated at the time of rotational acceleration and / or deceleration of the rotating part.
  • the encoder correction unit predicts the signal change timing in consideration of an error amount between the past signal change timing and actual measurement timing recorded for each rotation angle position of the rotation unit.
  • the encoder correction unit further includes an environmental information sensor for measuring environmental information, and the encoder correction unit takes into account an error amount between the past predicted signal change timing and actual measurement timing recorded for each measurement value of the environmental information.
  • the signal change timing is predicted.
  • the encoder correction unit takes the signal change timing into account by adding an error amount between the past predicted signal change timing and the actual measurement timing recorded for each control amount of the control signal for controlling the rotation unit. It is characterized by predicting.
  • control unit uses the correction signal instead of the generated change in the next encoder signal when a change in the next encoder signal occurs at a timing other than the predicted signal change timing. To do.
  • control unit calculates a rotation speed change rate of the rotary unit including the predicted signal change timing, The signal change timing of the encoder signal is predicted.
  • an X-ray source and an X-ray detector that detects the transmitted X-ray dose that is disposed opposite to the X-ray source and transmits the subject are mounted.
  • a step of rotating the rotation unit, a step of generating an encoder signal synchronized with the rotation of the rotation unit, a change in rotation speed of the rotation unit from the input encoder signal, and a signal change timing of the next encoder signal And predicting, generating a correction signal at the predicted signal change timing, and correcting the encoder signal based on the correction signal.
  • an X-ray source and an X-ray detector arranged to face the X-ray source and detecting an X-ray detector that detects a transmitted X-ray dose that passes through the subject, and an encoder signal synchronized with the rotation of the rotating unit are provided.
  • An encoder signal generation unit for generating, and a control unit for outputting a control signal for controlling the rotation unit based on a correction signal to which the encoder signal is input and the encoder signal is corrected, and the control unit receives the input encoder signal 2 is an example of an X-ray CT apparatus configured to calculate a rotation speed change of a rotation unit from the predicted value, predict a signal change timing of the next encoder signal, and generate a correction signal at the predicted signal change timing.
  • the X-ray CT apparatus 1 includes a scanner 2, a bed 3, and a console 4.
  • the scanner 2 includes a stationary part 201, a rotating part 202, and a slip ring 203.
  • the stationary unit 201 includes a scanner control device 210 and a rotation sensor 211 that functions as an encoder signal generation unit.
  • the scanner control device 210 is controlled by the system control device 403 provided in the console 4, and controls the entire scanner 2. Specifically, as shown in FIG. 2, a main control unit A1 that controls the entire scanner 2, a stationary unit communication control unit A2 that controls communication of the stationary unit 201, and a stationary unit that controls the view trigger signal of the stationary unit 201.
  • the view trigger signal control unit A3 and the encoder correction unit A4 that corrects the encoder signal input from the rotation sensor 211 are included.
  • the rotation sensor 211 detects the position of the slit of the encoder tape 224, which will be described later, provided in the rotation unit 202, and outputs a signal (pulse) corresponding to the detection result to the scanner control device 210 as the encoder signal. To do.
  • the rotating unit 202 includes an X-ray tube 220 that is an X-ray source, a high-pressure generator 221, a rotating unit controller 222, an X-ray detector 223, and an encoder tape 224 for generating an encoder signal. Rotate around the subject.
  • the X-ray tube 220 is a device that continuously or intermittently irradiates a subject placed on the bed 3 with X-rays.
  • the high voltage generator 221 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 unit control device 222 controls the rotation unit 202 based on a control signal from the scanner control device 210 controlled by the system control device 403 provided in the console 4. Specifically, as shown in FIG. 2, the rotation unit communication control unit B1 that controls communication of the rotation unit 202, the X-ray tube control unit B2 that controls the X-ray tube 220, and the view trigger signal of the rotation unit 202 are controlled. A rotating part view trigger signal control part B3.
  • the scanner control device 210, the rotation unit control device 222, and the system control device 403 may be collectively referred to as a control unit.
  • the scanner control device 210 and the rotation unit control device 222 can be realized by executing a CPU or FPGA program.
  • the system control device 403 is also a computer CPU or FPGA.
  • the scanner control device 210 and the system control device 403 can be realized by a single CPU or FPGA.
  • the X-ray detector 223 is a device that collects the spatial distribution of transmitted X-rays as digital data by detecting X-rays that are placed opposite to the X-ray tube 220 and transmitted through the subject, and detects a large number of X-rays.
  • the elements are arranged in the rotation direction of the rotation unit 202, or are arranged in two dimensions in the rotation direction of the rotation unit 202 and the rotation axis direction.
  • the encoder tape 224 is composed of a sheet metal 301 attached to the outer periphery of the rotating unit 202.
  • the sheet metal 301 is provided with slits 302 at equal intervals.
  • the number of slits 302 is determined according to the number of views of the X-ray CT apparatus 1 and the number of rotations of the rotation unit 202, and is 2880, for example.
  • the slip ring 203 transmits electric power and a control signal between the stationary part 201 and the rotating part 202.
  • the bed 3 includes a top plate on which a subject is placed, a bed control device, a vertical movement device, and a top drive device.
  • the bed control device controls the vertical movement device so that the height of the bed 3 is appropriate.
  • the top plate driving device is controlled to move the top plate back and forth in the body axis direction, or to move in the direction perpendicular to the body axis and parallel to the top plate (left and right direction).
  • the subject is carried in and out of the X-ray irradiation space of the scanner 2 by moving the top plate back and forth in the body axis direction.
  • the console 4 includes a display device 401, an input device 402, a system control device 403, an image processing device 404 as an image processing unit, and a storage device 405.
  • the display device 401 is a device that displays the CT image created by the image processing device 404, and is specifically a CRT (Cathode-Ray® Tube), an LCD (liquid crystal display), or the like.
  • the input device 402 is a device for inputting a subject's name, examination date and time, imaging conditions, and the like, specifically a keyboard or a pointing device.
  • the system control device 403 is a device that controls these devices and the scanner control device 210, the rotating unit control device 222, and the bed control device that is not shown.
  • the image processing device 404 is an image processing unit that performs CT processing on the measurement data sent from the X-ray detector 223 to perform CT image reconstruction.
  • the storage device 405 is a device that records data collected by the X-ray detector 223 and image data of a CT image created by the image processing device 404, and is specifically an HDD (Hard Disk Drive) or the like.
  • HDD Hard Disk Drive
  • the control system of the scanner 2 includes a scanner control device 210 provided in the stationary unit 201 and a rotation unit control device 222 provided in the rotation unit 202. Control signals, data, and the like are transmitted between the scanner control device 210 and the rotating unit control device 222.
  • the imaging position condition, the X-ray condition, and the like input to the system control apparatus 403 are transmitted to the main control unit A1 of the scanner control apparatus 210.
  • the main control unit A1 controls the position of the bed 3 and the rotation of the rotating unit 202 according to the imaging position condition input from the system control device 403. That is, the main control unit A1 transmits the X-ray condition input from the system control device 403 to the X-ray tube via the stationary unit communication control unit A2, the slip ring 203, and the rotation unit communication control unit B1 of the rotation unit control device 222. Transmit to control unit B2.
  • the X-ray tube control unit B2 controls the high-voltage generator 221 according to the X-ray conditions set by the main control unit A1, and applies and supplies predetermined X-ray tube voltage and X-ray tube current to the X-ray tube 220. .
  • the rotation sensor 211 is provided in the stationary part 201, detects the slit 302 of the encoder tape 224 interlocked with the rotation of the rotating part 202, and generates a pulse signal (referred to as an encoder signal) corresponding to the rotational speed of the rotating part 202, Send to encoder correction unit A4.
  • the encoder correction unit A4 calculates the rotation speed change rate of the rotation unit 202 from the encoder signal continuously input from the rotation sensor 211, and uses the calculated rotation speed change rate to signal change timing of the next encoder signal. And a dummy encoder signal (referred to as a correction signal) is generated at the predicted timing and sent to the main control unit A1 and the stationary unit view trigger signal control unit A3.
  • the X-ray CT apparatus includes an encoder correction unit that receives an encoder signal and generates a correction signal.
  • the encoder correction unit rotates the rotation unit from the encoder signal that has been continuously input until immediately before.
  • a configuration is provided in which a correction signal is generated by calculating a speed change rate and predicting a signal change timing.
  • the main control unit A1 transmits the correction signal to the rotation unit communication control unit B1 via the stationary unit communication control unit A2 and the slip ring 203.
  • the stationary unit communication control unit A2 and the rotation unit communication control unit B1 perform communication control based on the input correction signal.
  • the stationary part view trigger signal control unit A3 generates a view trigger signal based on the correction signal, and passes through the stationary part communication control unit A2, the slip ring 203, the rotation unit communication control unit B1, and the rotation unit view trigger signal control unit B3. Then, the view trigger signal is transmitted to the X-ray detector 223.
  • the X-ray detector 223 integrates and collects transmitted X-ray data in synchronization with the input view trigger signal, and transmits the data to the image processing apparatus 404 that is an image processing unit.
  • the image processing device 404 generates a subject fluoroscopic image, a tomographic image, and the like based on the acquired transmission X-ray data, and outputs them to the display device 401 and the storage device 405.
  • FIG. 4 is a diagram showing an encoder signal when the rotating unit 202 is accelerating.
  • FIG. 4 shows an encoder signal 303 in a normal state
  • FIG. 4 shows an encoder signal 304 at the time of contamination
  • FIG. 4 shows a correction signal 305 which is an encoder signal at the time of correction.
  • the normal encoder signal 303 is a signal in which, for example, the position of the slit 302 of the encoder tape 224 is “1”, and the other positions are “0”.
  • the encoder signal at the time of foreign matter contamination as shown in FIG. 4B is corrected to the correction signal as shown in FIG. 4C by the encoder correction unit A4 of the scanner controller 210.
  • the encoder correction unit A4 of the scanner controller 210 is corrected at the timing of the lower limit value 306 or the upper limit value 307 of the expected signal change timing to obtain a correction signal.
  • FIG. 5 and FIG. 6 are flowcharts showing the correction procedure of the encoder signal in the first embodiment.
  • the rotation speed of the rotation unit 202 is set by the system control device 403 and transmitted to the scanner control device 210.
  • the scanner control device 210 controls to drive the rotation unit 202 and start rotation according to the set rotation speed.
  • the rotation sensor 211 detects the slit 302 of the encoder tape 224 and outputs it as an encoder signal to the encoder correction unit A4 of the scanner control device 210.
  • the encoder correction unit A4 of the scanner control device 210 that has received the encoder signal from the rotation sensor 211 outputs a correction signal based on the received encoder signal.
  • Encoder correction unit A4 starts elapsed measuring time T n from the time of the inversion detection starts a timer upon detecting inverted such 0-0 from 1,1 of the input encoder signal encoder signal (S100). Thereafter, an encoder signal abnormality determination is performed based on T n (S110).
  • the conditions for determining whether there is an abnormality are as follows.
  • Normal judgment condition (1) T n is within the expected timing range and encoder signal inversion is detected Abnormal judgment condition (1) T n is smaller than the expected timing lower limit value and encoder signal inversion is detected Abnormal judgment condition (2 ) T n is greater than the expected timing upper limit value and the inversion of the encoder signal has not been detected.
  • the correction signal is inverted in accordance with the inversion of the encoder signal (S120a). In this case, the inversion of the correction signal matches the inversion of the input encoder signal.
  • T n becomes the expected timing lower limit. Until T n reaches the lower limit of the expected timing, the correction signal is inverted.
  • the encoder correction unit when a change in the next encoder signal occurs other than the predicted signal change timing, replaces the change in the next generated encoder signal with the predicted signal change. A correction signal generated at timing is used.
  • the encoder correction unit A4 stops the timer and ends the measurement of T n (S130), and predicts the next signal change (inversion) timing based on T n (S140).
  • Correction processing transition number of the correction signal if there is less than the predetermined number of times to start the measurement of the continuous again T n correction processing, when a prescribed number of times the correction process is finished (S150). The specified number of times is determined by the number of slits provided in the encoder tape 224 and the number of scans.
  • next signal change timing prediction process the signal change timing is predicted according to the procedure shown in FIG.
  • correction processing is not performed, that is, when the encoder signal is normal, the rotation speed ⁇ n of the rotating unit 202 is set to the slit interval provided on the encoder tape 224 and the elapsed time T n from the detection of inversion of the encoder signal.
  • S142a When correction processing is performed, that is, when the encoder signal is abnormal, calculation is performed using the slit interval and the previous prediction timing time n-1 (S142b). This rotational speed is retained for use in calculating the next rotational speed change rate.
  • the rotational speed change rate is calculated from the difference between the previous rotational speed and the current rotational speed using the formula described in S143.
  • an average value of a predetermined number of rotation speed change rates calculated up to that point may be used.
  • the calculated predicted the next rotational speed omega n + 1 of the rotating part from the rotation speed variation rate a n (S144), based on the predicted rotational speed calculated by the formula described in S144, the next encoder signal inversion Timing is predicted (S145).
  • the predicted inversion timing has a certain range with margins before and after.
  • the margin is determined by the statistical variation in the rotation speed of the rotation unit 202. Further, the margin is not a fixed value and may be changed while the rotating unit 202 is rotating.
  • the X-ray CT apparatus generates an encoder signal synchronized with the rotation of the rotating unit 202 by the encoder tape 224 and the rotation sensor 211.
  • the scanner control device 210 monitors the encoder signal at the encoder correction unit A4, and corrects it with a correction signal if any is missing. That is, the encoder correction unit A4 calculates the rotation speed change rate of the rotation unit 202 based on the encoder signals that are continuously input until immediately before, and predicts the signal change timing of the next encoder signal. Further, the encoder correction unit A4 inverts the output correction signal at the predicted signal change timing, and this correction signal is used as the corrected encoder signal as the main control unit A1, the stationary unit view trigger signal control unit A3. Is output.
  • an encoder signal can be output at an appropriate timing as in the normal state even when an encoder signal is lost even when an abnormality such as mixing of foreign matter occurs in the encoder tape even during rotation acceleration / deceleration of the rotating part. That is, when a change in the next encoder signal occurs other than the predicted signal change timing, the rotation speed change rate of the rotating unit is calculated including the predicted signal change timing, and the signal change timing of the next encoder signal is further calculated. Prediction makes it possible to correct missing encoder signals even during rotation acceleration / deceleration of the rotating unit, and to provide more stable X-ray CT apparatus performance.
  • the prediction process is performed using the rotation speed change rate of the rotating unit
  • the prediction timing and the actual normal signal change for each rotation angle position of the rotating unit in addition to the rotation speed change rate, the prediction timing and the actual normal signal change for each rotation angle position of the rotating unit.
  • Prediction processing is performed using the difference (error amount) from the timing.
  • the encoder correction unit of the present embodiment predicts the signal change timing by taking into account the difference (error amount) between the past signal change timing and the actual measurement timing recorded for each rotation angle position of the rotation unit.
  • the configuration of the X-ray CT apparatus according to the second embodiment is the same as that described with reference to FIGS.
  • the prediction process of the second embodiment will be described with reference to the flowchart of FIG. As shown in the figure, when the prediction process is started, whether or not the correction process is executed is confirmed (S241). When correction processing is not performed, that is, when the encoder signal is normal, an error amount between the prediction timing and the actual signal change timing is calculated and recorded in association with the rotation angle position (S242a). When correction processing is performed, that is, when the encoder signal is abnormal, the error amount is set to 0 and recorded in association with the rotation angle position (S242b).
  • the amount of error to be recorded is not limited to the amount of error calculated this time, and an average value of the already recorded value and the amount of error calculated this time may be taken.
  • the encoder signal can be corrected with higher accuracy during acceleration / deceleration.
  • the prediction process is performed using the error amount for each rotation angle position in addition to the rotation speed change rate of the rotation section
  • the rotation speed of the rotation section is influenced in addition to the rotation angle position.
  • Prediction processing is performed using an error amount for each environmental information such as ambient temperature and humidity. That is, the third embodiment further includes an environmental information sensor that measures environmental information of the X-ray CT apparatus, and the encoder correction unit records the past predicted signal change timing and actual measurement timing recorded for each measurement value of the environmental information. This is an embodiment of a configuration for predicting signal change timing in consideration of the amount of error.
  • the configuration of the X-ray CT apparatus of the third embodiment is the same as that of the first and second embodiments except that an environmental information sensor 204 for acquiring environmental information is added to the scanner 2 as shown in FIG.
  • the environmental information sensor 204 is, for example, a thermometer or a hygrometer.
  • the environment information temp is first acquired by the environment sensor (S341). After that, whether or not the correction process is executed is confirmed (S342) . If the correction process is not performed, an error amount between the prediction timing and the actual signal change timing is calculated, and the error amount e temp associated with the environment information is updated (S343a ). When the correction process is performed, the error amount e temp associated with the environment information is recorded (held) (S343b).
  • the error amount e temp to be recorded is not limited to the error amount calculated this time, and may be an average value of the already recorded value and the error amount calculated this time.
  • the rotation speed of the rotation unit is calculated (S344), the rotation speed change rate is calculated (S345), and the next rotation speed of the rotation unit is predicted from the rotation speed change rate (S346).
  • the environment information temp ′ is acquired again by the environment sensor (S347), the error amount e temp ′ corresponding to the environment information temp ′ is read (S348), and the next signal change timing is predicted (S349).
  • the environment information may use a plurality of elements such as temperature and humidity. Further, if the environmental change is small, the monitoring frequency of the environmental sensor may be reduced. According to the present embodiment, since the surrounding environment information is taken into account, the encoder signal can be corrected in accordance with the environment information of the apparatus.
  • the prediction process is performed using the error amount for each rotation angle position and the error amount for each environment information in addition to the rotation speed change rate of the rotation unit. Prediction processing is performed using an error amount for each control amount. That is, the encoder correction unit according to the fourth embodiment is configured to predict the signal change timing in consideration of the error amount between the past prediction timing and the actual measurement timing recorded for each control amount of the control signal for controlling the rotation unit. It is.
  • the configuration of the X-ray CT apparatus of the fourth embodiment is the same as that of the first and second embodiments, but a control amount to the rotating unit 202 is sent from the main control unit A1 of the scanner control device 210 to the encoder correction unit A4. It has become.
  • the prediction process in the fourth embodiment will be described with reference to the flowchart of FIG.
  • the control amount u is acquired from the main control unit A1 (S441). Thereafter, whether or not the correction process is executed is confirmed (S442). If the correction process is not performed, an error amount between the prediction timing associated with the control amount u and the actual signal change timing is calculated and recorded (S443a). When the correction process is performed, an error amount associated with the control amount u is recorded (held) (S443b).
  • the amount of error to be recorded is not limited to the amount of error calculated this time, and an average value of the already recorded value and the amount of error calculated this time may be taken.
  • the prediction process is performed using the error amount for each control amount to the rotation unit, it is possible to correct the encoder signal with higher accuracy according to the control amount.
  • the X-ray CT system is a rotation-rotate method in which the X-ray tube and the X-ray detector rotate together while irradiating a wide fan beam that covers the entire subject, and other methods.
  • the present invention is applicable to any type of X-ray CT apparatus.

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Abstract

The purpose of the invention is to provide an X-ray CT apparatus capable of correcting a missing encoder signal even upon acceleration or deceleration of a rotation unit. The X-ray CT apparatus is provided with: a rotation unit that comprises an X-ray tube and an X-ray detector mounted thereon and rotates around a subject; a rotation sensor that generates an encoder signal synchronized with rotation of the rotation unit; and a scanner control device that receives input of the encoder signal and outputs a control signal for controlling the rotation unit on the basis of a correction signal obtained by correcting the encoder signal. The scanner control device calculates a rotation speed change rate of the rotation unit from the encoder signal continuously input until immediately before, predicts the next signal change timing of the encoder signal, and generates a correction signal at the predicted signal change timing.

Description

Ｘ線ＣＴ装置及びその制御方法X-ray CT apparatus and control method thereof
　本発明は、X線CT装置に関し、特に回転部の回転に同期して生成されるエンコーダ信号の補正技術に関する。 The present invention relates to an X-ray CT apparatus, and more particularly to a technique for correcting an encoder signal generated in synchronization with rotation of a rotating unit.
　X線CT(Computed Tomography)装置は、X線源とX線検出器とを対向させて配置した回転部の開口部内に搬入された被検体の周囲からX線を照射して透過X線の強度に関するデータを収集し、収集したデータに基づいて被検体内部のX線吸収係数の分布情報を画像化する装置である。このX線CT装置では、例えば、等間隔にスリットが設けられたエンコーダテープを回転部の周囲に取り付け、静止部に設けられたセンサでスリットの位置を読み込むことにより、回転部の回転に同期したパルス(以下、エンコーダ信号という)を発生させる。エンコーダ信号は、回転部と静止部の通信制御や透過X線データの収集タイミング制御信号(以下、ビュートリガ信号という)の生成に利用される。 X-ray CT (Computed Tomography) equipment is an intensity of transmitted X-rays by irradiating X-rays from around a subject carried in an opening of a rotating part arranged with an X-ray source and an X-ray detector facing each other. Is a device that collects data on X-ray absorption coefficient distribution information inside a subject based on the collected data. In this X-ray CT apparatus, for example, an encoder tape provided with slits at equal intervals is attached around the rotating part, and the position of the slit is read by a sensor provided in the stationary part, thereby synchronizing with the rotation of the rotating part. A pulse (hereinafter referred to as an encoder signal) is generated. The encoder signal is used for communication control between the rotating unit and the stationary unit and generation of a transmission timing control signal (hereinafter referred to as a view trigger signal) of transmitted X-ray data.
　エンコーダテープ及びセンサを用いてエンコーダ信号を発生させる場合、エンコーダテープのスリットに異物が混入してスリットがふさがれてしまうと、エンコーダ信号が欠落し、その結果、回転部と静止部の通信やビュートリガ信号生成に異常が発生し、透過X線データの通信が行えなくなったり画像が劣化したりするという問題があった。 When an encoder signal is generated using an encoder tape and sensor, if foreign matter enters the slit of the encoder tape and the slit is blocked, the encoder signal is lost. There was a problem in that an abnormality occurred in trigger signal generation, and transmission X-ray data could not be communicated or the image deteriorated.
　このような問題を解決するために、特許文献1に示すように、欠落したエンコーダ信号を補正する手法が考案されている。特許文献1では、直前までに入力されたエンコーダ信号から周期を算出し、次のエンコーダ信号の入力タイミングを予測しダミー信号を発生することで欠落したエンコーダ信号を補正している。 In order to solve such a problem, as shown in Patent Document 1, a method of correcting a missing encoder signal has been devised. In Patent Document 1, the period is calculated from the encoder signal input immediately before, the input timing of the next encoder signal is predicted, and the missing encoder signal is corrected by generating a dummy signal.
特開2011-245195号公報JP 2011-245195 A
　しかしながら、特許文献1では、エンコーダ信号の周期が一定の状態、すなわち回転部が等速回転している場合しか補正を行えず、エンコーダ信号の周期が変化する状態、すなわち回転部の加減速時におけるエンコーダ信号の補正に関して配慮がなされてなかった。 However, in Patent Document 1, correction can be performed only when the period of the encoder signal is constant, that is, when the rotating part is rotating at a constant speed, and the period of the encoder signal is changed, that is, at the time of acceleration / deceleration of the rotating part. No consideration was given to the correction of the encoder signal.
　本発明の目的は、上記の課題を解決し、回転部の加減速時においても欠落したエンコーダ信号を補正可能なX線CT装置を提供することにある。 An object of the present invention is to solve the above problems and provide an X-ray CT apparatus capable of correcting a missing encoder signal even during acceleration / deceleration of a rotating unit.
　上記目的を達成するために、本発明においては、X線源とX線源に対向配置され被検体を透過する透過X線量を検出するX線検出器とが搭載された回転部と、回転部の回転に同期したエンコーダ信号を生成するエンコーダ信号生成部と、エンコーダ信号が入力され、エンコーダ信号を補正した補正信号に基づき、回転部を制御する制御信号を出力する制御部と、を備え、制御部は、入力されたエンコーダ信号から回転部の回転速度変化を算出し、次のエンコーダ信号の信号変化タイミングを予測し、予測された信号変化タイミングで補正信号を生成する構成のX線CT装置を提供する。 In order to achieve the above object, in the present invention, an X-ray source and an X-ray detector arranged to face the X-ray source and detecting an X-ray detector that transmits a transmitted X-ray through the subject, An encoder signal generation unit that generates an encoder signal that is synchronized with the rotation of the encoder, and a control unit that outputs a control signal for controlling the rotation unit based on a correction signal that is input with the encoder signal and corrects the encoder signal. The X-ray CT apparatus is configured to calculate a rotation speed change of the rotation unit from the input encoder signal, predict a signal change timing of the next encoder signal, and generate a correction signal at the predicted signal change timing. provide.
　本発明によれば、回転部の回転加減速時においてもエンコーダ信号の欠落を補正することが可能なX線CT装置を提供することができる。 According to the present invention, it is possible to provide an X-ray CT apparatus capable of correcting missing encoder signals even during rotation acceleration / deceleration of the rotating unit.
各実施例に係る、X線CT装置の全体構成例を説明するための図The figure for demonstrating the example of whole structure of the X-ray CT apparatus based on each Example 各実施例に係る、X線CT装置の制御系例を説明するための図The figure for demonstrating the example of a control system of the X-ray CT apparatus based on each Example 各実施例に係る、エンコーダテープの構成例を説明するための図The figure for demonstrating the structural example of the encoder tape based on each Example. 実施例1に係る、エンコーダ信号の補正処理を説明するためのタイムチャート図FIG. 4 is a time chart for explaining an encoder signal correction process according to the first embodiment. 実施例1に係る、エンコーダ信号補正処理を説明するためのフローチャート図Flowchart for explaining an encoder signal correction process according to the first embodiment. 実施例1に係る、予測処理の詳細を説明するためのフローチャート図The flowchart figure for demonstrating the detail of the prediction process based on Example 1. FIG. 実施例2に係る、予測処理の詳細を説明するためのフローチャート図The flowchart figure for demonstrating the detail of the prediction process based on Example 2. FIG. 実施例3に係る、制御系を説明するための図The figure for demonstrating the control system based on Example 3. 実施例3に係る、予測処理の詳細を説明するためのフローチャート図The flowchart figure for demonstrating the detail of the prediction process based on Example 3. FIG. 実施例4に係る、予測処理の詳細を説明するためのフローチャート図The flowchart figure for demonstrating the detail of the prediction process based on Example 4. FIG.
　本発明に係るX線CT装置は、X線源と、前記X線源に対向配置され被検体を透過する透過X線量を検出するX線検出器とが搭載された回転部と、前記回転部の回転に同期したエンコーダ信号を生成するエンコーダ信号生成部と、前記エンコーダ信号が入力され、前記エンコーダ信号を補正した補正信号に基づき、前記回転部を制御する制御信号を出力する制御部と、を備え、前記制御部は、入力された前記エンコーダ信号から前記回転部の回転速度変化を算出し、次のエンコーダ信号の信号変化タイミングを予測し、予測された前記信号変化タイミングで前記補正信号を生成する、ことを特徴とする。 The X-ray CT apparatus according to the present invention includes an X-ray source and a rotating unit 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 a subject is mounted; and the rotating unit An encoder signal generation unit that generates an encoder signal synchronized with the rotation of the encoder, and a control unit that outputs a control signal that controls the rotation unit based on a correction signal that is input with the encoder signal and corrects the encoder signal. The controller calculates a rotation speed change of the rotating unit from the input encoder signal, predicts a signal change timing of the next encoder signal, and generates the correction signal at the predicted signal change timing It is characterized by.
　また、前記制御部は、前記エンコーダ信号が入力され、前記補正信号を生成するエンコーダ補正部を備え、前記エンコーダ補正部は、直前までに連続して入力された前記エンコーダ信号から前記回転部の回転速度変化率を算出して、前記信号変化タイミングを予測することにより、前記補正信号を生成する、ことを特徴とする。 In addition, the control unit includes an encoder correction unit that receives the encoder signal and generates the correction signal. The encoder correction unit rotates the rotation unit from the encoder signal that is continuously input until immediately before. The correction signal is generated by calculating a speed change rate and predicting the signal change timing.
　また、前記回転速度変化率は、前記回転部の回転加速及び/又は減速時に算出すること、ことを特徴とする。 The rotational speed change rate is calculated at the time of rotational acceleration and / or deceleration of the rotating part.
　また、前記エンコーダ補正部は、前記回転部の回転角度位置毎に記録した過去の前記信号変化タイミングと実測タイミングとの誤差量を加味して、前記信号変化タイミングを予測する、ことを特徴とする請求項2に記載のX線CT装置。 The encoder correction unit predicts the signal change timing in consideration of an error amount between the past signal change timing and actual measurement timing recorded for each rotation angle position of the rotation unit. The X-ray CT apparatus according to claim 2.
　また、環境情報を測定する環境情報センサを更に備え、前記エンコーダ補正部は、前記環境情報の測定値毎に記録した過去の前記予測された信号変化タイミングと実測タイミングとの誤差量を加味して、前記信号変化タイミングを予測する、ことを特徴とする。 The encoder correction unit further includes an environmental information sensor for measuring environmental information, and the encoder correction unit takes into account an error amount between the past predicted signal change timing and actual measurement timing recorded for each measurement value of the environmental information. The signal change timing is predicted.
　また、前記エンコーダ補正部は、前記回転部を制御する前記制御信号の制御量毎に記録した過去の前記予測された信号変化タイミングと実測タイミングとの誤差量を加味して、前記信号変化タイミングを予測する、ことを特徴とする。 In addition, the encoder correction unit takes the signal change timing into account by adding an error amount between the past predicted signal change timing and the actual measurement timing recorded for each control amount of the control signal for controlling the rotation unit. It is characterized by predicting.
　また、前記制御部は、予測した前記信号変化タイミング以外で、次のエンコーダ信号の変化が発生した場合、発生した前記次のエンコーダ信号の変化に代えて、前記補正信号を用いる、ことを特徴とする。 Further, the control unit uses the correction signal instead of the generated change in the next encoder signal when a change in the next encoder signal occurs at a timing other than the predicted signal change timing. To do.
　また、前記制御部は、予測した前記信号変化タイミング以外で、次のエンコーダ信号の変化が発生した場合、予測した前記信号変化タイミングを含めて前記回転部の回転速度変化率を算出し、更に次のエンコーダ信号の信号変化タイミングを予測する、ことを特徴とする。 In addition, when a change in the next encoder signal occurs other than the predicted signal change timing, the control unit calculates a rotation speed change rate of the rotary unit including the predicted signal change timing, The signal change timing of the encoder signal is predicted.
　また、本発明に係るX線CT装置の制御方法へ、X線源と、前記X線源に対向配置され被検体を透過する透過X線量を検出するX線検出器と、が搭載された回転部を回転するステップと、前記回転部の回転に同期したエンコーダ信号を生成するステップと、入力された前記エンコーダ信号から前記回転部の回転速度変化を算出し、次のエンコーダ信号の信号変化タイミングを予測するステップと、前記予測された前記信号変化タイミングで補正信号を生成するステップと、前記補正信号に基づき前記エンコーダ信号を補正するステップとを有すること、を特徴とする。 Further, in the method for controlling the X-ray CT apparatus according to the present invention, an X-ray source and an X-ray detector that detects the transmitted X-ray dose that is disposed opposite to the X-ray source and transmits the subject are mounted. A step of rotating the rotation unit, a step of generating an encoder signal synchronized with the rotation of the rotation unit, a change in rotation speed of the rotation unit from the input encoder signal, and a signal change timing of the next encoder signal And predicting, generating a correction signal at the predicted signal change timing, and correcting the encoder signal based on the correction signal.
　以下、本発明の各種の実施形態を図面に従い詳細に説明する。 Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings.
　実施例1は、X線源とX線源に対向配置され被検体を透過する透過X線量を検出するX線検出器とが搭載された回転部と、回転部の回転に同期したエンコーダ信号を生成するエンコーダ信号生成部と、エンコーダ信号が入力され、エンコーダ信号を補正した補正信号に基づき、回転部を制御する制御信号を出力する制御部と、を備え、制御部は、入力されたエンコーダ信号から回転部の回転速度変化を算出し、次のエンコーダ信号の信号変化タイミングを予測し、予測された信号変化タイミングで補正信号を生成する構成のX線CT装置の実施例である。 In the first embodiment, an X-ray source and an X-ray detector arranged to face the X-ray source and detecting an X-ray detector that detects a transmitted X-ray dose that passes through the subject, and an encoder signal synchronized with the rotation of the rotating unit are provided. An encoder signal generation unit for generating, and a control unit for outputting a control signal for controlling the rotation unit based on a correction signal to which the encoder signal is input and the encoder signal is corrected, and the control unit receives the input encoder signal 2 is an example of an X-ray CT apparatus configured to calculate a rotation speed change of a rotation unit from the predicted value, predict a signal change timing of the next encoder signal, and generate a correction signal at the predicted signal change timing.
　以下、実施例1に係るX線CT装置の構成例について図1から図3を用いて説明する。この構成例は他の実施例においても同様に適用可能な構成例である。図1に示すように、X線CT装置1はスキャナ2と、寝台3と、操作卓4とを備える。スキャナ2は静止部201と、回転部202と、スリップリング203とを備えている。静止部201は、スキャナ制御装置210とエンコーダ信号生成部として機能する回転センサ211とを備えている。 Hereinafter, a configuration example of the X-ray CT apparatus according to the first embodiment will be described with reference to FIGS. This configuration example is a configuration example that can be similarly applied to other embodiments. As shown in FIG. 1, the X-ray CT apparatus 1 includes a scanner 2, a bed 3, and a console 4. The scanner 2 includes a stationary part 201, a rotating part 202, and a slip ring 203. The stationary unit 201 includes a scanner control device 210 and a rotation sensor 211 that functions as an encoder signal generation unit.
　スキャナ制御装置210は、操作卓4に備えられているシステム制御装置403に制御され、スキャナ2全体を制御する。具体的には図2に示すように、スキャナ2全体の制御を行う主制御部A1、静止部201の通信制御を行う静止部通信制御部A2、静止部201のビュートリガ信号を制御する静止部ビュートリガ信号制御部A3、回転センサ211から入力されるエンコーダ信号の補正を行うエンコーダ補正部A4を有する。 The scanner control device 210 is controlled by the system control device 403 provided in the console 4, and controls the entire scanner 2. Specifically, as shown in FIG. 2, a main control unit A1 that controls the entire scanner 2, a stationary unit communication control unit A2 that controls communication of the stationary unit 201, and a stationary unit that controls the view trigger signal of the stationary unit 201 The view trigger signal control unit A3 and the encoder correction unit A4 that corrects the encoder signal input from the rotation sensor 211 are included.
　回転センサ211は、回転部202に備えられている後で説明するエンコーダテープ224のスリットの位置を検出し、その検出結果に応じた信号(パルス)を上記のエンコーダ信号としてスキャナ制御装置210に出力する。 The rotation sensor 211 detects the position of the slit of the encoder tape 224, which will be described later, provided in the rotation unit 202, and outputs a signal (pulse) corresponding to the detection result to the scanner control device 210 as the encoder signal. To do.
　回転部202は、X線源であるX線管220と、高圧発生装置221と、回転部制御装置222と、X線検出器223と、エンコーダ信号を生成するためのエンコーダテープ224を備えており、被検体の周囲を回転するものである。X線管220は、寝台3上に載置された被検体にX線を連続的または断続的に照射する装置である。高圧発生装置221は、操作卓4に備えられているシステム制御装置403にて決定されたX線条件に従った管電圧及びX線管電流をX線管に印加または供給する。 The rotating unit 202 includes an X-ray tube 220 that is an X-ray source, a high-pressure generator 221, a rotating unit controller 222, an X-ray detector 223, and an encoder tape 224 for generating an encoder signal. Rotate around the subject. The X-ray tube 220 is a device that continuously or intermittently irradiates a subject placed on the bed 3 with X-rays. The high voltage generator 221 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.
　回転部制御装置222は、操作卓4に備えられているシステム制御装置403に制御されるスキャナ制御装置210からの制御信号に基づき、回転部202を制御する。具体的には図2に示すように、回転部202の通信制御を行う回転部通信制御部B1、X線管220の制御を行うX線管制御部B2、回転部202のビュートリガ信号を制御する回転部ビュートリガ信号制御部B3を有する。 The rotation unit control device 222 controls the rotation unit 202 based on a control signal from the scanner control device 210 controlled by the system control device 403 provided in the console 4. Specifically, as shown in FIG. 2, the rotation unit communication control unit B1 that controls communication of the rotation unit 202, the X-ray tube control unit B2 that controls the X-ray tube 220, and the view trigger signal of the rotation unit 202 are controlled. A rotating part view trigger signal control part B3.
　なお、本明細書において、上記のスキャナ制御装置210、回転部制御装置222、システム制御装置403を総称して制御部と呼ぶ場合がある。X線CT装置1において、上述した通り、スキャナ制御装置210、回転部制御装置222は、CPUやFPGAのプログラム実行で実現可能であり、同様にシステム制御装置403も、コンピュータのCPUや、FPGAでのプログラム実行で実現可能であり、スキャナ制御装置210、及びシステム制御装置403を一個のCPUやFPGAで実現することも可能である。 In the present specification, the scanner control device 210, the rotation unit control device 222, and the system control device 403 may be collectively referred to as a control unit. In the X-ray CT apparatus 1, as described above, the scanner control device 210 and the rotation unit control device 222 can be realized by executing a CPU or FPGA program. Similarly, the system control device 403 is also a computer CPU or FPGA. The scanner control device 210 and the system control device 403 can be realized by a single CPU or FPGA.
　X線検出器223は、X線管220と対向配置され被検体を透過したX線を検出することにより透過X線の空間的な分布をデジタルデータとして収集する装置であり、多数のX線検出素子を回転部202の回転方向に配列したもの、若しくは回転部202の回転方向と回転軸方向との2次元に配列したものである。 The X-ray detector 223 is a device that collects the spatial distribution of transmitted X-rays as digital data by detecting X-rays that are placed opposite to the X-ray tube 220 and transmitted through the subject, and detects a large number of X-rays. The elements are arranged in the rotation direction of the rotation unit 202, or are arranged in two dimensions in the rotation direction of the rotation unit 202 and the rotation axis direction.
　図3に示すように、エンコーダテープ224は、回転部202の外周に取り付けられた板金301で構成される。板金301には、等間隔にスリット302が設けられている。スリット302の数は、X線CT装置1のビュー数及び回転部202の回転数に応じて決定されるものであり、例えば、2880個である。 As shown in FIG. 3, the encoder tape 224 is composed of a sheet metal 301 attached to the outer periphery of the rotating unit 202. The sheet metal 301 is provided with slits 302 at equal intervals. The number of slits 302 is determined according to the number of views of the X-ray CT apparatus 1 and the number of rotations of the rotation unit 202, and is 2880, for example.
　図1、図2に戻り、スリップリング203は、静止部201と回転部202との間で電力と制御信号を伝達する。寝台3は、被検体が載置される天板、寝台制御装置、上下動装置、及び天板駆動装置を備えて構成される。寝台制御装置は、上下動装置を制御して寝台3の高さを適切なものにする。また、天板駆動装置を制御して天板を体軸方向に前後動させたり、体軸と垂直方向であって、かつ天板に平行な方向(左右方向)に移動させたりする。天板を体軸方向に前後動させることにより、被検体がスキャナ2のX線照射空間に搬入及び搬出される。 1 and 2, the slip ring 203 transmits electric power and a control signal between the stationary part 201 and the rotating part 202. The bed 3 includes a top plate on which a subject is placed, a bed control device, a vertical movement device, and a top drive device. The bed control device controls the vertical movement device so that the height of the bed 3 is appropriate. Further, the top plate driving device is controlled to move the top plate back and forth in the body axis direction, or to move in the direction perpendicular to the body axis and parallel to the top plate (left and right direction). The subject is carried in and out of the X-ray irradiation space of the scanner 2 by moving the top plate back and forth in the body axis direction.
　操作卓4は、表示装置401と、入力装置402と、システム制御装置403と、画像処理部である画像処理装置404と、記憶装置405とを備えている。表示装置401は、画像処理装置404で作成されたCT画像を表示する装置であり、具体的にはCRT(Cathode-Ray Tube)やLCD(液晶ディスプレイ)等である。入力装置402は、被検体氏名、検査日時、撮影条件などを入力するための装置であり、具体的にはキーボードやポインティングデバイスである。 The console 4 includes a display device 401, an input device 402, a system control device 403, an image processing device 404 as an image processing unit, and a storage device 405. The display device 401 is a device that displays the CT image created by the image processing device 404, and is specifically a CRT (Cathode-Ray® Tube), an LCD (liquid crystal display), or the like. The input device 402 is a device for inputting a subject's name, examination date and time, imaging conditions, and the like, specifically a keyboard or a pointing device.
　システム制御装置403は、これらの装置及びスキャナ制御装置210と、回転部制御装置222と、図示を省略した寝台制御装置を制御する装置である。画像処理装置404は、X線検出器223から送出される計測データを演算処理してCT画像再構成を行う画像処理部である。 The system control device 403 is a device that controls these devices and the scanner control device 210, the rotating unit control device 222, and the bed control device that is not shown. The image processing device 404 is an image processing unit that performs CT processing on the measurement data sent from the X-ray detector 223 to perform CT image reconstruction.
　記憶装置405は、X線検出器223で収集したデータ及び画像処理装置404で作成されたCT画像の画像データを記録する装置であり、具体的にはHDD(Hard Disk Drive)等である。 The storage device 405 is a device that records data collected by the X-ray detector 223 and image data of a CT image created by the image processing device 404, and is specifically an HDD (Hard Disk Drive) or the like.
　次に、図1、図2を参照して、X線CT装置1の動作機能について説明する。図2に示すように、スキャナ2の制御系は、静止部201に備えられているスキャナ制御装置210と回転部202に備えられている回転部制御装置222により構成され、スリップリング203を介してスキャナ制御装置210と回転部制御装置222との間で制御信号やデータ等が伝達される。 Next, the operation function of the X-ray CT apparatus 1 will be described with reference to FIG. 1 and FIG. As shown in FIG. 2, the control system of the scanner 2 includes a scanner control device 210 provided in the stationary unit 201 and a rotation unit control device 222 provided in the rotation unit 202. Control signals, data, and the like are transmitted between the scanner control device 210 and the rotating unit control device 222.
　システム制御装置403に入力された撮影位置条件やX線条件等は、スキャナ制御装置210の主制御部A1へ伝送される。主制御部A1は、システム制御装置403から入力された撮影位置条件に従い、寝台3の位置や回転部202の回転制御を行う。すなわち、主制御部A1は、システム制御装置403から入力されたX線条件を静止部通信制御部A2、スリップリング203、及び回転部制御装置222の回転部通信制御部B1を介してX線管制御部B2へ伝送する。 The imaging position condition, the X-ray condition, and the like input to the system control apparatus 403 are transmitted to the main control unit A1 of the scanner control apparatus 210. The main control unit A1 controls the position of the bed 3 and the rotation of the rotating unit 202 according to the imaging position condition input from the system control device 403. That is, the main control unit A1 transmits the X-ray condition input from the system control device 403 to the X-ray tube via the stationary unit communication control unit A2, the slip ring 203, and the rotation unit communication control unit B1 of the rotation unit control device 222. Transmit to control unit B2.
　X線管制御部B2は、主制御部A1で設定されたX線条件に従って、高圧発生装置221を制御し、X線管220に所定のX線管電圧、X線管電流を印加・供給させる。 The X-ray tube control unit B2 controls the high-voltage generator 221 according to the X-ray conditions set by the main control unit A1, and applies and supplies predetermined X-ray tube voltage and X-ray tube current to the X-ray tube 220. .
　回転センサ211は静止部201に設けられ、回転部202の回転に連動するエンコーダテープ224のスリット302を検出し、回転部202の回転速度に応じたパルス信号(エンコーダ信号と称する)を発生し、エンコーダ補正部A4へ送出する。 The rotation sensor 211 is provided in the stationary part 201, detects the slit 302 of the encoder tape 224 interlocked with the rotation of the rotating part 202, and generates a pulse signal (referred to as an encoder signal) corresponding to the rotational speed of the rotating part 202, Send to encoder correction unit A4.
　エンコーダ補正部A4は、回転センサ211から連続して入力されるエンコーダ信号から、回転部202の回転速度変化率を算出し、算出された回転速度変化率を用いて次のエンコーダ信号の信号変化タイミングを予測し、予測されたタイミングでダミーのエンコーダ信号(補正信号と称する)を生成し、これを主制御部A1、静止部ビュートリガ信号制御部A3に送る。 The encoder correction unit A4 calculates the rotation speed change rate of the rotation unit 202 from the encoder signal continuously input from the rotation sensor 211, and uses the calculated rotation speed change rate to signal change timing of the next encoder signal. And a dummy encoder signal (referred to as a correction signal) is generated at the predicted timing and sent to the main control unit A1 and the stationary unit view trigger signal control unit A3.
　すなわち、本実施例のX線CT装置は、エンコーダ信号が入力され、補正信号を生成するエンコーダ補正部を備え、エンコーダ補正部は、直前までに連続して入力されたエンコーダ信号から回転部の回転速度変化率を算出して、信号変化タイミングを予測することにより、補正信号を生成する構成を備える。 That is, the X-ray CT apparatus according to the present embodiment includes an encoder correction unit that receives an encoder signal and generates a correction signal. The encoder correction unit rotates the rotation unit from the encoder signal that has been continuously input until immediately before. A configuration is provided in which a correction signal is generated by calculating a speed change rate and predicting a signal change timing.
　主制御部A1は、補正信号を静止部通信制御部A2、及びスリップリング203を経由して回転部通信制御部B1へ伝送する。静止部通信制御部A2および回転部通信制御部B1は入力された補正信号を基に通信制御を行う。静止部ビュートリガ信号制御部A3は、補正信号に基づいてビュートリガ信号を生成し、静止部通信制御部A2、スリップリング203、回転部通信制御部B1、回転部ビュートリガ信号制御部B3を経由してX線検出器223へビュートリガ信号を伝送する。 The main control unit A1 transmits the correction signal to the rotation unit communication control unit B1 via the stationary unit communication control unit A2 and the slip ring 203. The stationary unit communication control unit A2 and the rotation unit communication control unit B1 perform communication control based on the input correction signal. The stationary part view trigger signal control unit A3 generates a view trigger signal based on the correction signal, and passes through the stationary part communication control unit A2, the slip ring 203, the rotation unit communication control unit B1, and the rotation unit view trigger signal control unit B3. Then, the view trigger signal is transmitted to the X-ray detector 223.
　X線検出器223は、入力されたビュートリガ信号に同期して、透過X線データを積分、収集し、画像処理部である画像処理装置404へデータを送信する。画像処理装置404は、取得した透過X線データに基づいて被検体透視画像や断層像等を生成し、表示装置401及び記憶装置405へ出力する。 The X-ray detector 223 integrates and collects transmitted X-ray data in synchronization with the input view trigger signal, and transmits the data to the image processing apparatus 404 that is an image processing unit. The image processing device 404 generates a subject fluoroscopic image, a tomographic image, and the like based on the acquired transmission X-ray data, and outputs them to the display device 401 and the storage device 405.
　次に、実施例1の動作について、図4のタイムチャート、図5及び図6のフローチャートを用いて説明する。図4は回転部202が加速中のエンコーダ信号を示す図である。まず、図4の(a)は正常時のエンコーダ信号303、図4の(b)は異物混入時のエンコーダ信号304、図4の(c)は補正時のエンコーダ信号である補正信号305を示す。正常時のエンコーダ信号303は、例えばエンコーダテープ224のスリット302の位置を「1」、その他の位置を「0」とする信号である。 Next, the operation of the first embodiment will be described with reference to the time chart of FIG. 4 and the flowcharts of FIGS. FIG. 4 is a diagram showing an encoder signal when the rotating unit 202 is accelerating. First, (a) in FIG. 4 shows an encoder signal 303 in a normal state, (b) in FIG. 4 shows an encoder signal 304 at the time of contamination, and (c) in FIG. 4 shows a correction signal 305 which is an encoder signal at the time of correction. . The normal encoder signal 303 is a signal in which, for example, the position of the slit 302 of the encoder tape 224 is “1”, and the other positions are “0”.
　本実施例のX線CT装置では、図4の(b)のような異物混入時のエンコーダ信号をスキャナ制御装置210のエンコーダ補正部A4により図4の(c)のような補正信号に補正する。エンコーダ信号に欠落が生じた場合には、予想信号変化タイミングの下限値306、或いは上限値307のタイミングで欠落を補正して補正信号とする。 In the X-ray CT apparatus of the present embodiment, the encoder signal at the time of foreign matter contamination as shown in FIG. 4B is corrected to the correction signal as shown in FIG. 4C by the encoder correction unit A4 of the scanner controller 210. . When the encoder signal is missing, the missing signal is corrected at the timing of the lower limit value 306 or the upper limit value 307 of the expected signal change timing to obtain a correction signal.
　図5、図6は、実施例1におけるエンコーダ信号の補正手順を示すフローチャートである。まず、システム制御装置403により回転部202の回転速度が設定され、スキャナ制御装置210に伝送される。スキャナ制御装置210は、設定された回転速度に応じて回転部202を駆動し回転を開始するよう制御する。 FIG. 5 and FIG. 6 are flowcharts showing the correction procedure of the encoder signal in the first embodiment. First, the rotation speed of the rotation unit 202 is set by the system control device 403 and transmitted to the scanner control device 210. The scanner control device 210 controls to drive the rotation unit 202 and start rotation according to the set rotation speed.
　図5のフローチャートにおいて、回転部202の回転が開始されると、回転センサ211はエンコーダテープ224のスリット302を検出し、エンコーダ信号としてスキャナ制御装置210のエンコーダ補正部A4に出力する。回転センサ211からのエンコーダ信号を受信したスキャナ制御装置210のエンコーダ補正部A4は、受信したエンコーダ信号に基づき、補正信号を出力する。 In the flowchart of FIG. 5, when the rotation of the rotation unit 202 is started, the rotation sensor 211 detects the slit 302 of the encoder tape 224 and outputs it as an encoder signal to the encoder correction unit A4 of the scanner control device 210. The encoder correction unit A4 of the scanner control device 210 that has received the encoder signal from the rotation sensor 211 outputs a correction signal based on the received encoder signal.
　エンコーダ補正部A4は、入力されたエンコーダ信号の0から1、1から0といった反転を検出したらタイマーを起動しエンコーダ信号の反転検出時からの経過時間Tnの計測を開始する(S100)。その後、Tnに基づいてエンコーダ信号の異常判定を行う(S110)。異常の有無の判定条件は下記と通りである。 Encoder correction unit A4 starts elapsed measuring time T n from the time of the inversion detection starts a timer upon detecting inverted such 0-0 from 1,1 of the input encoder signal encoder signal (S100). Thereafter, an encoder signal abnormality determination is performed based on T n (S110). The conditions for determining whether there is an abnormality are as follows.
　正常判定条件(1) Tnが予想タイミングの範囲内尚且つエンコーダ信号の反転を検出
　異常判定条件(1) Tnが予想タイミング下限値より小さい尚且つエンコーダ信号の反転を検出
　異常判定条件(2) Tnが予想タイミング上限値より大きい尚且つエンコーダ信号の反転を未検出
　エンコーダ信号が正常判定条件(1) を満たす場合は、エンコーダ信号の反転に合わせて補正信号を反転させる(S120a)。この場合、補正信号の反転は、入力されたエンコーダ信号の反転に合致する。 Normal judgment condition (1) T n is within the expected timing range and encoder signal inversion is detected Abnormal judgment condition (1) T n is smaller than the expected timing lower limit value and encoder signal inversion is detected Abnormal judgment condition (2 ) T n is greater than the expected timing upper limit value and the inversion of the encoder signal has not been detected. When the encoder signal satisfies the normal determination condition (1), the correction signal is inverted in accordance with the inversion of the encoder signal (S120a). In this case, the inversion of the correction signal matches the inversion of the input encoder signal.
　エンコーダ信号が異常判定条件(1) を満たす場合、すなわち、スリットの後半部分に異物が混入しエンコーダ信号の「1」の後半部分が欠落している場合は、Tnが予想タイミング下限値になるまで待機しTnが予想タイミング下限値となった後、補正信号を反転させる。 When the encoder signal satisfies the abnormality determination condition (1), that is, when foreign matter is mixed in the latter half of the slit and the latter half of the encoder signal “1” is missing, T n becomes the expected timing lower limit. Until T n reaches the lower limit of the expected timing, the correction signal is inverted.
　また、エンコーダ信号が異常判定条件(2) を満たす場合、すなわち、スリットの前半部またはスリット全体に異物が混入し、エンコーダ信号の「1」の前半部分または全体が欠落しTnが予想タイミング上限値より大きくなった場合は、その時点で即座に補正信号を反転させる(S120b)。言い換えるなら、本実施例の構成において、エンコーダ補正部は、予測した信号変化タイミング以外で、次のエンコーダ信号の変化が発生した場合、発生した次のエンコーダ信号の変化に代えて、予測した信号変化タイミングで生成した補正信号を用いる。 Also, when the encoder signal satisfies the abnormality determination condition (2), that is, foreign matter is mixed in the first half of the slit or the entire slit, the first half or the whole of the encoder signal “1” is missing, and Tn is the upper limit of the expected timing. If it exceeds the value, the correction signal is immediately inverted at that time (S120b). In other words, in the configuration of the present embodiment, the encoder correction unit, when a change in the next encoder signal occurs other than the predicted signal change timing, replaces the change in the next generated encoder signal with the predicted signal change. A correction signal generated at timing is used.
　補正信号の反転後、エンコーダ補正部A4は、タイマーを停止させTnの計測を終了し(S130)、Tnを基に次の信号変化(反転)タイミングを予測する(S140)。補正処理は補正信号の反転回数が規定回数未満の場合は補正処理を継続し再びTnの計測を開始し、規定回数となったら補正処理を終了する(S150)。規定回数は、エンコーダテープ224に設けられたスリットの数及びスキャン回数によって定められる。 After the correction signal is inverted, the encoder correction unit A4 stops the timer and ends the measurement of T n (S130), and predicts the next signal change (inversion) timing based on T n (S140). Correction processing transition number of the correction signal if there is less than the predetermined number of times to start the measurement of the continuous again T n correction processing, when a prescribed number of times the correction process is finished (S150). The specified number of times is determined by the number of slits provided in the encoder tape 224 and the number of scans.
　次の信号変化タイミング予測処理(S140)では、図6に示す手順で信号変化タイミングの予測を行う。補正処理を行っていない場合、すなわち、エンコーダ信号が正常だった場合は、回転部202の回転速度ωnをエンコーダテープ224に設けられたスリット間隔およびエンコーダ信号の反転検出時からの経過時間Tnを用いて算出する(S142a)。補正処理を行った場合、すなわち、エンコーダ信号が異常だった場合は、スリット間隔および前回の予測タイミングtimen-1を用いて算出する(S142b)。今回の回転速度は次回の回転速度変化率の算出に用いるため保持しておく。 In the next signal change timing prediction process (S140), the signal change timing is predicted according to the procedure shown in FIG. When correction processing is not performed, that is, when the encoder signal is normal, the rotation speed ω n of the rotating unit 202 is set to the slit interval provided on the encoder tape 224 and the elapsed time T n from the detection of inversion of the encoder signal. (S142a). When correction processing is performed, that is, when the encoder signal is abnormal, calculation is performed using the slit interval and the previous prediction timing time n-1 (S142b). This rotational speed is retained for use in calculating the next rotational speed change rate.
　次に、回転速度変化率anを算出する(S143)。回転速度変化率は、前回の回転速度と今回の回転速度の差分から、S143に記載の式で算出する。回転速度変化率は、前回の回転速度と今回の回転速度の差分の他に、その時点までに算出した所定数の回転速度変化率の平均値を用いてもよい。次に、算出した回転速度変化率anから回転部の次回の回転速度ωn+1を予測し(S144)、S144に記載の式で算出した予測回転速度に基づき、次のエンコーダ信号の反転タイミングを予測する(S145)。予測する反転タイミングは前後にマージンを持ち一定の範囲を持つ。マージンは、統計的な回転部202の回転速度のばらつきによって定める。また、マージンは固定値ではなく、回転部202の回転中に変更してもよい。 Then, to calculate the rotational speed variation rate a n (S143). The rotational speed change rate is calculated from the difference between the previous rotational speed and the current rotational speed using the formula described in S143. As the rotation speed change rate, in addition to the difference between the previous rotation speed and the current rotation speed, an average value of a predetermined number of rotation speed change rates calculated up to that point may be used. Then, the calculated predicted the next rotational speed omega n + 1 of the rotating part from the rotation speed variation rate a n (S144), based on the predicted rotational speed calculated by the formula described in S144, the next encoder signal inversion Timing is predicted (S145). The predicted inversion timing has a certain range with margins before and after. The margin is determined by the statistical variation in the rotation speed of the rotation unit 202. Further, the margin is not a fixed value and may be changed while the rotating unit 202 is rotating.
　以上説明したように、本実施例のX線CT装置は、エンコーダテープ224と回転センサ211とにより回転部202の回転に同期したエンコーダ信号を生成する。このとき、スキャナ制御装置210はエンコーダ補正部A4にて、エンコーダ信号を監視し欠落がある場合は補正信号により補正する。すなわち、エンコーダ補正部A4は、直前までに連続して入力されたエンコーダ信号に基づいて回転部202の回転速度変化率を算出し、次のエンコーダ信号の信号変化タイミングを予測する。また、エンコーダ補正部A4は、予測された信号変化タイミングでその出力である補正信号を反転し、この補正信号は、補正されたエンコーダ信号として、主制御部A1、静止部ビュートリガ信号制御部A3へ出力される。 As described above, the X-ray CT apparatus according to the present embodiment generates an encoder signal synchronized with the rotation of the rotating unit 202 by the encoder tape 224 and the rotation sensor 211. At this time, the scanner control device 210 monitors the encoder signal at the encoder correction unit A4, and corrects it with a correction signal if any is missing. That is, the encoder correction unit A4 calculates the rotation speed change rate of the rotation unit 202 based on the encoder signals that are continuously input until immediately before, and predicts the signal change timing of the next encoder signal. Further, the encoder correction unit A4 inverts the output correction signal at the predicted signal change timing, and this correction signal is used as the corrected encoder signal as the main control unit A1, the stationary unit view trigger signal control unit A3. Is output.
　その結果、回転部の回転加減速時においてもエンコーダテープに異物の混入などの異常が生じエンコーダ信号が欠落した場合でも、正常時と同じように適正なタイミングでエンコーダ信号を出力できる。すなわち、予測した信号変化タイミング以外で、次のエンコーダ信号の変化が発生した場合、予測した信号変化タイミングを含めて回転部の回転速度変化率を算出し、更に次のエンコーダ信号の信号変化タイミングを予測することにより、回転部の回転加減速時においてもエンコーダ信号の欠落を補正することが可能となり、より安定したX線CT装置性能を提供可能となる。 As a result, an encoder signal can be output at an appropriate timing as in the normal state even when an encoder signal is lost even when an abnormality such as mixing of foreign matter occurs in the encoder tape even during rotation acceleration / deceleration of the rotating part. That is, when a change in the next encoder signal occurs other than the predicted signal change timing, the rotation speed change rate of the rotating unit is calculated including the predicted signal change timing, and the signal change timing of the next encoder signal is further calculated. Prediction makes it possible to correct missing encoder signals even during rotation acceleration / deceleration of the rotating unit, and to provide more stable X-ray CT apparatus performance.
　実施例1では、回転部の回転速度変化率を用いて予測処理を行うの対し、実施例2では回転速度変化率に加えて回転部の回転角度位置毎に予測タイミングと実際の正常な信号変化タイミングとの差分(誤差量)を用いて予測処理を行う。言い換えるなら、本実施例のエンコーダ補正部は、回転部の回転角度位置毎に記録した過去の信号変化タイミングと実測タイミングの差分(誤差量)を加味して、信号変化タイミングを予測する。実施例2のX線CT装置の構成については、実施例1と同様、図1-図3で説明した構成である。 In the first embodiment, the prediction process is performed using the rotation speed change rate of the rotating unit, whereas in the second embodiment, in addition to the rotation speed change rate, the prediction timing and the actual normal signal change for each rotation angle position of the rotating unit. Prediction processing is performed using the difference (error amount) from the timing. In other words, the encoder correction unit of the present embodiment predicts the signal change timing by taking into account the difference (error amount) between the past signal change timing and the actual measurement timing recorded for each rotation angle position of the rotation unit. The configuration of the X-ray CT apparatus according to the second embodiment is the same as that described with reference to FIGS.
　実施例2の予測処理について図7のフローチャートを用いて説明する。同図に示すように、予測処理を開始したら補正処理の実行の有無を確認する(S241)。補正処理を行っていない場合、すなわち、エンコーダ信号が正常な場合は予測タイミングと実際の信号変化タイミングの誤差量を算出し回転角度位置に関連付けて記録する(S242a)。補正処理を行った場合、すなわち、エンコーダ信号が異常な場合は、誤差量を0として回転角度位置に関連付けて記録する(S242b)。記録する誤差量は、今回算出した誤差量に限定されず、既に記録されている値と今回算出した誤差量の平均値をとってもよい。 The prediction process of the second embodiment will be described with reference to the flowchart of FIG. As shown in the figure, when the prediction process is started, whether or not the correction process is executed is confirmed (S241). When correction processing is not performed, that is, when the encoder signal is normal, an error amount between the prediction timing and the actual signal change timing is calculated and recorded in association with the rotation angle position (S242a). When correction processing is performed, that is, when the encoder signal is abnormal, the error amount is set to 0 and recorded in association with the rotation angle position (S242b). The amount of error to be recorded is not limited to the amount of error calculated this time, and an average value of the already recorded value and the amount of error calculated this time may be taken.
　その後、回転速度を算出し(S243)、回転速度変化率を算出し(S244)、回転速度変化率から回転部の次回の回転速度を予測する(S245)。次に、前回の回転時に記録した回転部202の回転角度位置に対応した誤差量を読み込む(S246)。そして、誤差量を加味した予測タイミングを算出する(S247)。 Then, the rotation speed is calculated (S243), the rotation speed change rate is calculated (S244), and the next rotation speed of the rotating unit is predicted from the rotation speed change rate (S245). Next, an error amount corresponding to the rotation angle position of the rotation unit 202 recorded at the previous rotation is read (S246). And the prediction timing which considered the error amount is calculated (S247).
　本実施例によれば、誤差量を勘案して予測タイミングを算出するため、より高精度に加減速時におけるエンコーダ信号の補正を行うことができる。 According to this embodiment, since the prediction timing is calculated in consideration of the error amount, the encoder signal can be corrected with higher accuracy during acceleration / deceleration.
　実施例2では、回転部の回転速度変化率に加えて回転角度位置毎の誤差量を用いて予測処理を行うのに対し、実施例3では回転角度位置の他に回転部の回転速度に影響を与える周囲の温度や湿度などの環境情報毎の誤差量を用いて予測処理を行う。すなわち、実施例3は、X線CT装置の環境情報を測定する環境情報センサを更に備え、エンコーダ補正部は、環境情報の測定値毎に記録した過去の前記予測された信号変化タイミングと実測タイミングの誤差量を加味して、信号変化タイミングを予測する構成の実施例である。実施例3のX線CT装置の構成は、図8に示すようにスキャナ2に環境情報を取得するための環境情報センサ204が追加されている以外では実施例1、2と同様である。環境情報センサ204は、例えば温度計や湿度計などである。 In the second embodiment, the prediction process is performed using the error amount for each rotation angle position in addition to the rotation speed change rate of the rotation section, whereas in the third embodiment, the rotation speed of the rotation section is influenced in addition to the rotation angle position. Prediction processing is performed using an error amount for each environmental information such as ambient temperature and humidity. That is, the third embodiment further includes an environmental information sensor that measures environmental information of the X-ray CT apparatus, and the encoder correction unit records the past predicted signal change timing and actual measurement timing recorded for each measurement value of the environmental information. This is an embodiment of a configuration for predicting signal change timing in consideration of the amount of error. The configuration of the X-ray CT apparatus of the third embodiment is the same as that of the first and second embodiments except that an environmental information sensor 204 for acquiring environmental information is added to the scanner 2 as shown in FIG. The environmental information sensor 204 is, for example, a thermometer or a hygrometer.
　実施例3における予測処理について図9のフローチャートを用いて説明する。同図に示すように、先ず環境センサにより環境情報tempを取得する(S341)。その後、補正処理の実行の有無を確認し(S342)、補正処理を行っていない場合は予測タイミングと実際の信号変化タイミングの誤差量を算出し環境情報に関連付ける誤差量etempを更新する(S343a)。補正処理を行った場合は、環境情報に関連付ける誤差量etempを記録(保持)する(S343b)。記録する誤差量etempは、今回算出した誤差量に限定されず、既に記録されている値と今回算出した誤差量の平均値をとってもよい。 The prediction process in the third embodiment will be described with reference to the flowchart of FIG. As shown in the figure, the environment information temp is first acquired by the environment sensor (S341). After that, whether or not the correction process is executed is confirmed (S342) .If the correction process is not performed, an error amount between the prediction timing and the actual signal change timing is calculated, and the error amount e temp associated with the environment information is updated (S343a ). When the correction process is performed, the error amount e temp associated with the environment information is recorded (held) (S343b). The error amount e temp to be recorded is not limited to the error amount calculated this time, and may be an average value of the already recorded value and the error amount calculated this time.
　その後、回転部の回転速度の算出(S344)、回転速度変化率の算出(S345)、回転速度変化率から回転部の次回の回転速度を予測する(S346)。そして、再び環境センサにより環境情報temp’を取得(S347)し、環境情報temp’に対応した誤差量etemp’を読み込み(S348)、次の信号変化タイミングを予測する(S349)。 Thereafter, the rotation speed of the rotation unit is calculated (S344), the rotation speed change rate is calculated (S345), and the next rotation speed of the rotation unit is predicted from the rotation speed change rate (S346). Then, the environment information temp ′ is acquired again by the environment sensor (S347), the error amount e temp ′ corresponding to the environment information temp ′ is read (S348), and the next signal change timing is predicted (S349).
　なお、環境情報は温度と湿度というように複数の要素を用いてもよい。また、環境の変化が少ない状況であるならば環境センサの監視頻度を少なくしてもよい。本実施例によれば、周囲の環境情報を考慮するため、装置の環境情報に応じた、エンコーダ信号の補正を行うことができる。 Note that the environment information may use a plurality of elements such as temperature and humidity. Further, if the environmental change is small, the monitoring frequency of the environmental sensor may be reduced. According to the present embodiment, since the surrounding environment information is taken into account, the encoder signal can be corrected in accordance with the environment information of the apparatus.
　実施例2、3では、回転部の回転速度変化率に加えて回転角度位置毎の誤差量や環境情報毎の誤差量を用いて予測処理を行うのに対し、実施例4では回転部への制御量毎の誤差量を用いて予測処理を行う。すなわち、実施例4のエンコーダ補正部は、回転部を制御する制御信号の制御量毎に記録した過去の予測タイミングと実測タイミングの誤差量を加味して、信号変化タイミングを予測する構成の実施例である。 In the second and third embodiments, the prediction process is performed using the error amount for each rotation angle position and the error amount for each environment information in addition to the rotation speed change rate of the rotation unit. Prediction processing is performed using an error amount for each control amount. That is, the encoder correction unit according to the fourth embodiment is configured to predict the signal change timing in consideration of the error amount between the past prediction timing and the actual measurement timing recorded for each control amount of the control signal for controlling the rotation unit. It is.
　実施例4のX線CT装置の構成は実施例1、2と同様であるが、スキャナ制御装置210の主制御部A1からエンコーダ補正部A4に対して回転部202への制御量が送られるようになっている。実施例4における予測処理について図10のフローチャート用いて説明する。 The configuration of the X-ray CT apparatus of the fourth embodiment is the same as that of the first and second embodiments, but a control amount to the rotating unit 202 is sent from the main control unit A1 of the scanner control device 210 to the encoder correction unit A4. It has become. The prediction process in the fourth embodiment will be described with reference to the flowchart of FIG.
　図10に示すように、先ず主制御部A1から制御量uを取得する(S441)。その後、補正処理の実行の有無を確認し(S442)、補正処理を行っていない場合は制御量uに関連付ける予測タイミングと実際の信号変化タイミングの誤差量を算出し記録する(S443a)。補正処理を行った場合は、制御量uに関連付ける誤差量を記録(保持)する(S443b)。記録する誤差量は、今回算出した誤差量に限定されず、既に記録されている値と今回算出した誤差量の平均値をとってもよい。 As shown in FIG. 10, first, the control amount u is acquired from the main control unit A1 (S441). Thereafter, whether or not the correction process is executed is confirmed (S442). If the correction process is not performed, an error amount between the prediction timing associated with the control amount u and the actual signal change timing is calculated and recorded (S443a). When the correction process is performed, an error amount associated with the control amount u is recorded (held) (S443b). The amount of error to be recorded is not limited to the amount of error calculated this time, and an average value of the already recorded value and the amount of error calculated this time may be taken.
　その後、回転部の回転速度の算出(S444)、回転速度変化率の算出(S445)、回転速度変化率から回転部の次回の回転速度を予測する(S446)。そして、主制御部A1から次回の制御量u’を取得し(S447)、制御量u’に対応した誤差量を読み込み(S448)、次の信号変化タイミングを予測する(S449)。 Thereafter, calculation of the rotation speed of the rotation unit (S444), calculation of the rotation speed change rate (S445), and prediction of the next rotation speed of the rotation unit from the rotation speed change rate (S446). Then, the next control amount u ′ is acquired from the main control unit A1 (S447), the error amount corresponding to the control amount u ′ is read (S448), and the next signal change timing is predicted (S449).
　本実施例の構成によれば、回転部への制御量毎の誤差量を用いて予測処理を行うため、制御量に応じたより高精度なエンコーダ信号の補正を行うことができる。 According to the configuration of the present embodiment, since the prediction process is performed using the error amount for each control amount to the rotation unit, it is possible to correct the encoder signal with higher accuracy according to the control amount.
　以上、本発明の種々の実施例を述べたが、本発明はこれらに限定されるものではない。 Although various embodiments of the present invention have been described above, the present invention is not limited to these.
　例えば、上記した実施例は本発明のより良い理解のために詳細に説明したのであり、必ずしも説明の全ての構成を備えるものに限定されものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることが可能であり、また、ある実施例の構成に他の実施例の構成を加えることが可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。X線CT装置は、被検体全体をカバーするワイドファンビームを照射しつつX線管とX線検出器とが一体となり回転する回転-回転方式(Rotate-Rotate方式)、その他の方式のものがあるが、本発明はいずれの方式のX線CT装置にも適用可能である。 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. The X-ray CT system is a rotation-rotate method in which the X-ray tube and the X-ray detector rotate together while irradiating a wide fan beam that covers the entire subject, and other methods. However, the present invention is applicable to any type of X-ray CT apparatus.
　更に、上述した各構成、機能、制御装置等は、それらの一部又は全部を実現するプログラムを作成する例を説明したが、それらの一部又は全部を例えば集積回路で設計する等によりハードウェアで実現しても良いことは言うまでもない。また、当業者であれば、本願で開示した技術的思想の範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、それらについても当然に本発明の技術的範囲に属する。 Further, the above-described configurations, functions, control devices, and the like have been described as examples in which a program that realizes part or all of them is created. Needless to say, it can be realized with this. In addition, it is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. .
　1　X線CT装置、2　スキャナ、3　寝台、4　操作卓、201　静止部、202　回転部、203　スリップリング、210　スキャナ制御装置、211　回転センサ、220　X線管、221　高圧発生装置、222　回転部制御装置、223　X線検出器、224　エンコーダテープ、301　板金、302　スリット、303、304　エンコーダ信号、305　補正信号、306　下限値、307　上限値、401　表示装置、402　入力装置、403　システム制御装置、404　画像処理装置、405　記憶装置 1 X-ray CT device, 2 scanner, 3 bed, 4 console, 201 stationary unit, 202 rotating unit, 203 slip ring, 210 scanner control device, 211 rotation sensor, 220 X-ray tube, 221 high pressure generator, 222 rotating unit Control device, 223 X-ray detector, 224 encoder tape, 301 sheet metal, 302 slit, 303, 304 encoder signal, 305 correction signal, 306 lower limit value, 307 upper limit value, 401 display device, 402 input device, 403 system control device, 404 image processing device, 405 storage device

Claims (9)

  1. 　X線源と、前記X線源に対向配置され被検体を透過する透過X線量を検出するX線検出器とが搭載された回転部と、前記回転部の回転に同期したエンコーダ信号を生成するエンコーダ信号生成部と、前記エンコーダ信号が入力され、前記エンコーダ信号を補正した補正信号に基づき、前記回転部を制御する制御信号を出力する制御部と、を備え、
    　前記制御部は、入力された前記エンコーダ信号から前記回転部の回転速度変化を算出し、次のエンコーダ信号の信号変化タイミングを予測し、予測された前記信号変化タイミングで前記補正信号を生成する、ことを特徴とするX線CT装置。     A rotating unit on which an X-ray source and 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 are mounted, and an encoder signal that is synchronized with the rotation of the rotating unit is generated. An encoder signal generation unit; and a control unit that outputs a control signal that controls the rotation unit based on a correction signal that is input with the encoder signal and that corrects the encoder signal.
    The control unit calculates a rotation speed change of the rotation unit from the input encoder signal, predicts a signal change timing of the next encoder signal, and generates the correction signal at the predicted signal change timing. X-ray CT apparatus characterized by that.
  2. 　前記制御部は、前記エンコーダ信号が入力され、前記補正信号を生成するエンコーダ補正部を備え、
    　前記エンコーダ補正部は、直前までに連続して入力された前記エンコーダ信号から前記回転部の回転速度変化率を算出して、前記信号変化タイミングを予測することにより、前記補正信号を生成する、ことを特徴とする請求項1に記載のX線CT装置。     The control unit includes an encoder correction unit that receives the encoder signal and generates the correction signal;
    The encoder correction unit generates the correction signal by calculating a rotation speed change rate of the rotation unit from the encoder signal continuously input until immediately before and predicting the signal change timing. The X-ray CT apparatus according to claim 1, wherein:
  3. 　前記回転速度変化率は、前記回転部の回転加速及び/又は減速時に算出すること、
    　ことを特徴とする請求項2に記載のX線CT装置。     The rotation speed change rate is calculated at the time of rotation acceleration and / or deceleration of the rotating unit,
    3. The X-ray CT apparatus according to claim 2, wherein
  4. 　前記エンコーダ補正部は、前記回転部の回転角度位置毎に記録した過去の前記信号変化タイミングと実測タイミングとの誤差量を加味して、前記信号変化タイミングを予測する、ことを特徴とする請求項2に記載のX線CT装置。 The encoder correction unit predicts the signal change timing in consideration of an error amount between the past signal change timing and actual measurement timing recorded for each rotation angle position of the rotation unit. X-ray CT apparatus according to 2.
  5. 　環境情報を測定する環境情報センサを更に備え、
    　前記エンコーダ補正部は、前記環境情報の測定値毎に記録した過去の前記予測された信号変化タイミングと実測タイミングとの誤差量を加味して、前記信号変化タイミングを予測する、ことを特徴とする請求項2に記載のX線CT装置。     An environmental information sensor for measuring environmental information is further provided.
    The encoder correction unit predicts the signal change timing in consideration of an error amount between the past predicted signal change timing and actual measurement timing recorded for each measurement value of the environment information. The X-ray CT apparatus according to claim 2.
  6. 　前記エンコーダ補正部は、前記回転部を制御する前記制御信号の制御量毎に記録した過去の前記予測された信号変化タイミングと実測タイミングとの誤差量を加味して、前記信号変化タイミングを予測する、ことを特徴とする請求項2に記載のX線CT装置。 The encoder correction unit predicts the signal change timing in consideration of an error amount between the past predicted signal change timing and actual measurement timing recorded for each control amount of the control signal for controlling the rotation unit. The X-ray CT apparatus according to claim 2, wherein
  7. 　前記制御部は、予測した前記信号変化タイミング以外で、次のエンコーダ信号の変化が発生した場合、発生した前記次のエンコーダ信号の変化に代えて、前記補正信号を用いる、ことを特徴とする請求項1に記載のX線CT装置。 The control unit uses the correction signal instead of the generated change in the next encoder signal when a change in the next encoder signal occurs at a timing other than the predicted signal change timing. Item 2. The X-ray CT apparatus according to Item 1.
  8. 　前記制御部は、予測した前記信号変化タイミング以外で、次のエンコーダ信号の変化が発生した場合、予測した前記信号変化タイミングを含めて前記回転部の回転速度変化率を算出し、更に次のエンコーダ信号の信号変化タイミングを予測する、ことを特徴とする請求項7に記載のX線CT装置。 When the next encoder signal change occurs at a time other than the predicted signal change timing, the control unit calculates the rotation speed change rate of the rotary unit including the predicted signal change timing, and further calculates the next encoder. 8. The X-ray CT apparatus according to claim 7, wherein a signal change timing of the signal is predicted.
  9. 　X線源と、前記X線源に対向配置され被検体を透過する透過X線量を検出するX線検出器と、が搭載された回転部を回転するステップと、前記回転部の回転に同期したエンコーダ信号を生成するステップと、入力された前記エンコーダ信号から前記回転部の回転速度変化を算出し、次のエンコーダ信号の信号変化タイミングを予測するステップと、前記予測された前記信号変化タイミングで補正信号を生成するステップと、前記補正信号に基づき前記エンコーダ信号を補正するステップと、を有すること、を特徴とするX線CT装置の制御方法。 An X-ray source, 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, a step of rotating the rotating unit mounted thereon, and synchronized with the rotation of the rotating unit A step of generating an encoder signal, a step of calculating a rotation speed change of the rotating unit from the inputted encoder signal, predicting a signal change timing of the next encoder signal, and a correction using the predicted signal change timing A method for controlling an X-ray CT apparatus, comprising: generating a signal; and correcting the encoder signal based on the correction signal.
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