JP6577487B2 - X-ray CT apparatus and control method thereof - Google Patents

Description

  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 (Computed Tomography) equipment is an intensity of transmitted X-rays by irradiating X-rays from around the subject carried into the opening of a rotating part arranged with the X-ray source and 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.

  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.

  In order to solve such a problem, as shown in Patent Document 1, a technique for 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.

JP 2011-245195 A

  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.

  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.

  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.

  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.

The figure for demonstrating the example of whole structure of the X-ray CT apparatus based on each Example The figure for demonstrating the example of a control system of the X-ray CT apparatus based on each Example The figure for demonstrating the structural example of the encoder tape based on each Example. 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 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.

  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.

  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 X-ray CT apparatus according to claim 2.

  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.

  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.

  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.

  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.

  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.

  Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings.

  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.

  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.

  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.

  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.

  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.

  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.

  Returning to FIG. 1 and FIG. 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.

  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.

  Next, an operation function of the X-ray CT apparatus 1 will be described with reference to FIGS. 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.

  Imaging position conditions, X-ray conditions, and the like input to the system control device 403 are transmitted to the main control unit A1 of the scanner control device 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.

  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.

  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.

  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”.

In the X-ray CT apparatus of the present embodiment, the encoder signal 304 at the time of foreign matter mixing as shown in (b) of FIG. 4 is converted into a correction signal 305 as shown in (c) of FIG. 4 by the encoder correction unit A4 of the scanner controller 210. to correct. 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.

  FIG. 5 and FIG. 6 are flowcharts showing the procedure for correcting 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.

  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.

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. 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.

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.

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.

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.

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.

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.

  As described above, the X-ray CT apparatus of 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.

  As a result, an encoder signal can be output at an appropriate timing as in the normal state even when an abnormality such as mixing of foreign matters occurs in the encoder tape and the encoder signal is lost even during the rotation acceleration / deceleration of the rotating portion. 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.

  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.

  The prediction process according to 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.

  Thereafter, the rotational speed is calculated (S243), the rotational speed change rate is calculated (S244), and the next rotational speed of the rotating unit is predicted from the rotational 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).

  According to the present 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.

  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.

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.

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).

  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.

  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.

  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.

  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.

  Thereafter, the rotation speed of the rotation unit is calculated (S444), the rotation speed change rate is calculated (S445), and the next rotation speed of the rotation unit is predicted 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).

  According to the configuration of the present embodiment, since the prediction process is performed using the error amount for each control amount to the rotating unit, the encoder signal can be corrected with higher accuracy according to the control amount.

  While various embodiments of the present invention have been described above, the present invention is not limited to these.

  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.

  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-ray CT system, 2 scanner, 3 bed, 4 console, 201 stationary part, 202 rotating part, 203 slip ring, 210 scanner controller, 211 rotation sensor, 220 X-ray tube, 221 high pressure generator, 222 rotating part 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 (7)

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 With a correction unit,
The encoder correction unit generates the correction signal by calculating the rotation speed change rate of the rotation unit from the encoder signal continuously input until immediately before and predicting the signal change timing,
The rotational speed variation rate is, X-rays CT apparatus characterized by calculating the time of rotation acceleration and / or deceleration of the rotating part. 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 With a correction unit,
The encoder correction unit generates the correction signal by calculating the rotation speed change rate of the rotation unit from the encoder signal continuously input until immediately before and predicting the signal change timing,
Wherein the encoder correction unit, in consideration of the amount of error between the signal change timing and the measured timing of the past recorded for each rotation angle position of the rotating portion, predicts the signal change timing, characterized in that X Line CT device. 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 With a correction unit,
The encoder correction unit generates the correction signal by calculating the rotation speed change rate of the rotation unit from the encoder signal continuously input until immediately before and predicting the signal change timing,
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. X- ray CT system. 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 With a correction unit,
The encoder correction unit generates the correction signal by calculating the rotation speed change rate of the rotation unit from the encoder signal continuously input until immediately before and predicting the signal change timing,
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. , X-rays CT device you wherein a. 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, generates the correction signal at the predicted signal change timing,
Wherein the control unit, other than the signal change timing predicted, when the change of the next encoder signal is generated, in place of the change of the generated following the encoder signal, using said correction signal, characterized in that X- ray CT system. 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. The X-ray CT apparatus according to claim 5 , wherein a signal change timing of the signal is predicted. 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 and generating an encoder signal, and calculates a rotational speed change rate from the encoder signal input continuously until just before the rotation portion during rotation acceleration and / or deceleration of the rotating part, the signal of the next encoder signal An X-ray CT comprising: predicting a change timing; generating a correction signal at the predicted signal change timing; and correcting the encoder signal based on the correction signal. Control method of the device.

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