JP2009148482A - X-ray computerized tomographic equipment and image photographing measure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always warrant projection data required for the reconstruction of an image. <P>SOLUTION: When the section of projection data used for the reconstruction is decided from electrocardiogram information and an image corresponding to a predetermined electrocardiogram phase is reconstructed according to the projection data corresponding to two or more heart beats, control is performed so as to extend the exposure period of X rays or a period, in which X-ray intensity is strong, during a period of at least one heart beat among two or more heart beats used for the reconstruction of the image. For example, control is performed so as to extend the exposure period of the X rays during a period of the first heart beat among two or more heart beats used for the reconstruction of the image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray computed tomography apparatus and an imaging method.

  Conventionally, an X-ray computed tomography apparatus (hereinafter referred to as X-ray CT apparatus, CT; Computed Tomography) has exposed X-rays based on projection data obtained by detecting X-rays transmitted through a subject. Many medical practices such as disease diagnosis, treatment, surgical planning, etc. by reconstructing and providing tomographic images showing morphological information of human body tissue in the subject on the plane (tomographic plane) Plays an important role.

  In a cardiac examination in which a heart disease or the like is diagnosed using a cardiac tomographic image of a subject provided by an X-ray CT apparatus, the heart is an organ that is constantly beating, so the time resolution of the cardiac tomographic image is improved. It becomes important. Therefore, in the reconstruction of cardiac tomographic images, projection data at a time when the heart movement is relatively small is prepared for multiple heartbeats using the electrocardiogram information of the subject acquired from the electrocardiograph attached to the subject. In general, an electrocardiographic synchronous reconstruction method for reconstructing a cardiac tomographic image having a high time resolution is generally performed.

  Here, as a method for collecting projection data, a retrospective gating method (retrospective gating method, hereinafter abbreviated as RG method) and a prospective gating method (a prospective gating method, hereinafter abbreviated as PG method). It is written.) In the RG method, X-rays are continuously exposed to continuously collect projection data for a plurality of heart rates, and the heart of the subject simultaneously acquired from the electrocardiograph among each of the continuously collected projection data for the plurality of heartbeats. This is a method of extracting projection data of a specific phase (for example, a phase with little heart motion) based on the radio wave shape, and a method of reconstructing a cardiac tomographic image with high time resolution using the extracted projection data. . On the other hand, in the PG method, a tomographic imaging schedule is determined based on an electrocardiographic waveform of a subject acquired in advance from an electrocardiograph, and X-rays are intermittently exposed or exposed according to the determined imaging schedule. By modulating and increasing the intensity of the emitted X-rays at a specific phase, projection data at a specific phase is collected for a plurality of heartbeats, and a cardiac tomographic image with high time resolution is reconstructed using the acquired projection data. Is the method. Here, generally, in the medical field, it is required to employ the PG method capable of reducing the X-ray exposure amount of the subject.

  In addition, reconstruction of tomographic images includes methods such as HALF reconstruction (half reconstruction), FULL reconstruction (full reconstruction), and segment reconstruction.

  The HALF reconstruction (half reconstruction) is arranged around the subject while the X-ray tube rotates over a range of “180 degrees + α (α is a fan angle)” to face the X-ray tube. This is a method for reconstructing a tomographic image using projection data collected by an X-ray detector, and projection of a “360 degree range” collected by the X-ray detector while the X-ray tube makes one rotation around the subject. When compared with FULL reconstruction (full reconstruction) in which a tomographic image is reconstructed from data, the time resolution can be reduced to about ½.

  On the other hand, segment reconstruction is a technique for reconstructing a tomographic image by dividing and collecting projection data required for reconstruction over a predetermined number of heartbeats. For example, projection data of the same phase in “a range of 180 degrees + α” is divided and collected over a predetermined number of heartbeats, and these collected projection data are combined to form “projection data in a range of 180 degrees + α”. This is a technique for reconstructing a tomographic image by performing HALF reconstruction (half reconstruction) later. In this segment reconstruction, when n is a predetermined number, the temporal resolution can be reduced to about (180 + α) / n as compared with the case where an image is reconstructed from projection data in a 360 degree range, and the HALF reconstruction ( Time resolution can be further improved compared to half reconstruction. In the segment reconstruction, projection data having the same phase in the “360 degree range” is divided and collected over a predetermined number of heartbeats, and the collected projection data is combined to obtain “360 degree range projection data”. After that, the tomographic image may be reconstructed by performing FULL reconstruction (full reconstruction).

  For example, as shown in FIG. 13, in segment reconstruction, projection data in the same phase corresponding to each range obtained by dividing the “range of 180 degrees + α” required for HALF reconstruction (half reconstruction) into three parts. Since the tomographic images are reconstructed by collecting from each of the three heartbeats, it is possible to reconstruct a tomographic image having a time resolution three times that of HALF reconstruction (half reconstruction) using only the heartbeat. it can.

  Here, when HALF reconstruction (half reconstruction) using segment reconstruction is performed by the PG method, an average interval time of R waves acquired in advance from an electrocardiograph attached to the subject (that is, the subject) A predetermined number and a specific phase range are determined from the average heart rate), and an X-ray exposure period for acquiring projection data to be divided and acquired is determined. During tomographic image capturing, as shown in FIG. 13, an X-ray tube and an X-ray detector are collected so that segment data corresponding to each of the ranges obtained by dividing the “range of 180 degrees + α” into three parts is collected. It is necessary to control the rotation of the gantry device on which is mounted.

  Further, in Patent Document 1, the projection data required for reconstruction is lost by changing the range of the specific phase corresponding to the heart rate fluctuation (heart rate fluctuation) of the subject during tomography. Techniques for preventing are disclosed.

JP 2007-117719 A

  Incidentally, the above-described conventional technique has a problem that projection data necessary for image reconstruction is not necessarily guaranteed.

  That is, since the technique using the segment reconstruction described above cannot cope with a sudden change in the heart rate such as arrhythmia, projection data necessary for image reconstruction is not necessarily guaranteed. It was.

  Further, in the technique for changing the range of the specific phase corresponding to the heartbeat fluctuation described above, the rotation phase of the X-ray tube can be rotated so that, for example, a three-divided range can be collected in each of three heartbeats as shown in FIG. If the phase is not reached, the projection data necessary for the image reconstruction cannot be prepared. Therefore, there is a problem that the projection data necessary for the image reconstruction is not necessarily guaranteed.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an X-ray computed tomography apparatus and an image photographing apparatus that can always guarantee projection data necessary for image reconstruction. It aims to provide a method.

  In order to solve the above-mentioned problems and achieve the object, the present invention according to claim 1 collects electrocardiographic information of a subject, collects projection data by exposing X-rays to the subject, An X-ray computed tomography apparatus that reconstructs an image based on collected electrocardiogram information and projection data, and controls X-ray exposure start and exposure stop based on the electrocardiogram information, or X X-ray control means for performing modulation control of the intensity of the line, and a section of projection data used for reconstruction based on the electrocardiogram information, and combining the projection data corresponding to a plurality of heartbeats together with a predetermined electrocardiographic phase Image reconstruction processing means for reconstructing an image corresponding to the X-ray exposure means, wherein the X-ray control means emits X-rays in at least one heartbeat period of a plurality of heartbeats used for the image reconstruction. Extended period or period with high X-ray intensity And controls so as to.

  The present invention according to claim 4 collects electrocardiographic information of a subject, collects projection data by exposing the subject to X-rays, and based on the collected electrocardiographic information and projection data. An X-ray computed tomography apparatus that reconstructs an image, and controls X-ray exposure start and stop or X-ray intensity modulation control based on the electrocardiogram information. And image reconstruction for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats Processing means, wherein the X-ray control means increases the number of heartbeats for collecting projection data when newly collected projection data overlaps any of the already collected projection data, Continue to collect projection data Or, and controls the X-ray exposure so as to stop the acquisition of projection data.

  The present invention according to claim 5 collects electrocardiographic information of a subject, collects projection data by exposing X-rays to the subject, and based on the collected electrocardiographic information and projection data. An X-ray computed tomography apparatus that reconstructs an image, and controls X-ray exposure start and stop or X-ray intensity modulation control based on the electrocardiogram information. And image reconstruction for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats Processing means, wherein the X-ray control means is configured such that the appearance intervals of the characteristic waves in the electrocardiogram information collected before the start of imaging consist of repetition of a plurality of different appearance intervals, and the plurality of different appearance intervals. At least one replays the image Appearance of the characteristic wave in the electrocardiogram information collected after the start of imaging when the necessary projection data, which is necessary for data generation, is a collectable appearance interval that can be collected at a time From the interval, a heartbeat that becomes the collectable appearance interval is predicted, and in the predicted heartbeat, the start and stop of X-ray exposure are controlled so that the necessary projection data is collected at one time, or the X-ray Intensity modulation control is performed.

  The present invention according to claim 7 collects electrocardiographic information of a subject, collects projection data by exposing X-rays to the subject, and based on the collected electrocardiographic information and projection data. An X-ray computed tomography apparatus that reconstructs an image, and controls X-ray exposure start and stop or X-ray intensity modulation control based on the electrocardiogram information. And image reconstruction for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats Processing means, wherein the X-ray control means, based on the electrocardiogram information, the projection data collected during execution of the imaging is projection data required for reconstructing the image Then, to stop the X-ray exposure, Others, and controls so as to weaken the intensity of the X-ray.

  The present invention according to claim 8 collects electrocardiographic information of a subject, collects projection data by exposing X-rays to the subject, and based on the collected electrocardiographic information and projection data. An image capturing method for reconstructing an image, based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the intensity of X-rays; An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; The X-ray control step extends an X-ray exposure period or a period during which the X-ray intensity is high in at least one heart beat period among a plurality of heart beats used for reconstruction of the image. It is characterized by controlling to.

  The present invention according to claim 9 collects electrocardiographic information of a subject, collects projection data by exposing X-rays to the subject, and based on the collected electrocardiographic information and projection data. An image capturing method for reconstructing an image, based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the intensity of X-rays; An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; The X-ray control step includes increasing the number of heartbeats for collecting projection data when newly collected projection data overlaps any of the already collected projection data, and Continue to collect or And controlling the X-ray exposure so as to stop the collection of data.

  The present invention according to claim 10 collects electrocardiographic information of a subject, collects projection data by exposing X-rays to the subject, and based on the collected electrocardiographic information and projection data. An image capturing method for reconstructing an image, based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the intensity of X-rays; An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; In the X-ray control step, the appearance interval of the characteristic wave in the electrocardiogram information collected before the start of imaging is composed of repetition of a plurality of different appearance intervals, and at least one of the plurality of different appearance intervals is To reconstruct the image From the appearance interval of the characteristic wave in the electrocardiogram information collected after the start of imaging, when the required projection data that is required projection data is a collectable appearance interval that can be collected at a time, Control of the start and stop of X-ray exposure or the modulation control of X-ray intensity so as to collect the necessary projection data at a predicted heart rate by predicting a heart rate that can be collected. It is characterized by performing.

  According to the eleventh aspect of the present invention, the electrocardiogram information of the subject is collected, the projection data is collected by exposing the subject to X-rays, and based on the collected electrocardiogram information and projection data. An image capturing method for reconstructing an image, based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the intensity of X-rays; An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; If the projection data collected during the execution of imaging based on the electrocardiographic information is projection data required to reconstruct the image, To stop X-ray exposure, or And controlling to weaken the degree.

  According to the first or eighth aspect of the present invention, even if an arrhythmia occurs at a heart rate other than the selected heart rate and projection data in the set electrocardiographic phase range cannot be collected, projection data necessary for reconstruction at the selected heart rate. Can be collected, and projection data necessary for image reconstruction can always be guaranteed.

  According to the present invention described in claim 4 or 9, it is possible to determine whether or not the projection data collected from now on is resonance, and it is possible to collect only projection data suitable for image reconstruction. become.

  According to the present invention described in claim 5 or 10, when the arrhythmia pattern of the subject is determined as, for example, a two-stage pulse or a three-stage pulse, and the longer RR interval becomes a collectable appearance interval Because it is possible to collect the data for the period necessary for reconstruction at the same time by predicting the heartbeat that can be collected, it is always guaranteed the projection data necessary for image reconstruction corresponding to arrhythmia It becomes possible to do.

  According to the seventh or eleventh aspect of the present invention, for example, when an arrhythmia having a long RR interval occurs due to atrial fibrillation and data for a period necessary for reconstruction is collected at a time, the imaging is terminated. Therefore, it is possible to always guarantee projection data necessary for image reconstruction while preventing unnecessary X-ray exposure in response to arrhythmia.

  Exemplary embodiments of an X-ray computed tomography apparatus and an image imaging method according to the present invention will be described below in detail with reference to the accompanying drawings. In the following description, the X-ray computed tomography apparatus is abbreviated as an X-ray CT apparatus (CT; Computed Tomography).

  In the following, the case of performing tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction will be described, but the present invention is not limited to this, and segment reconstruction is used. It may be a case where tomography for performing full reconstruction (full reconstruction) is performed. In the following, a case where a prospective gating method (a prospective gating method) for predetermining an imaging schedule using the phase range as a projection data collection period as an X-ray exposure period will be described. However, the present invention is not limited to this, and it may be a case where a retrospective gating method (retrospective gating method) for continuously projecting X-rays and collecting projection data in a phase range after tomography is completed.

[Outline and Features of X-ray CT Apparatus in Embodiment 1]
First, the main features of the X-ray CT apparatus according to the first embodiment will be specifically described with reference to FIG. FIG. 1 is a diagram for explaining the outline and features of the X-ray CT apparatus according to the first embodiment.

  The X-ray CT apparatus according to the first embodiment collects electrocardiographic information of a subject, collects projection data by exposing the subject to X-rays, and produces a tomogram based on the collected electrocardiographic information and projection data. The outline of image reconstruction is to divide the range of 180 ° + α, which is the range of projection data for HALF reconstruction (half reconstruction) of a tomographic image, by the set number of segments. Further, tomographic imaging is performed in which each projection data having a segment size corresponding to “range of 180 degrees + α” is collected for each heartbeat of the number of segments in the set phase range of the electrocardiogram waveform.

  Here, the X-ray CT apparatus according to the first embodiment calculates the number of segments and the phase range from the average interval time of the R wave of the electrocardiogram information collected before the start of tomography (that is, the average heart rate of the subject). Tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction is performed.

  For example, in the X-ray CT apparatus according to the first embodiment, when the average heart rate of the subject collected before the start of tomography is a low heart rate smaller than 60 bpm (beat per minute), “number of segments: 1”. If the medium heart rate is 60 bpm to 80 bpm, “Segment number: 2” is set. If the heart rate is higher than 80 bpm, “Segment number: 3” is set. When the average heart rate of the subject collected before the start of tomography is a low heart rate lower than 60 bpm, the diastole of the heart is set as a phase range that is an X-ray exposure period, and 60 bpm When the heart rate is -80 bpm, the systole to diastole of the heart is set as the phase range, and when the heart rate is higher than 80 bpm, the systolic phase of the heart is set as the phase range.

  Note that the number of segments and the phase range may be set based on the above-described heart rate threshold even when the operator of the X-ray CT apparatus refers to the electrocardiogram information collected. The X-ray CT apparatus that holds the threshold may automatically set the number of segments and the phase range with reference to the collected electrocardiogram information. In the present embodiment, the case where the threshold values used for setting the number of segments and the phase range are the same value has been described. However, the present invention is not limited to this and is used for setting the number of segments. The threshold value used and the threshold value used for setting the phase range may be values set independently.

  Here, the main feature of the present invention is that projection data necessary for reconstruction of a tomographic image can always be guaranteed. Briefly explaining this main feature, the X-ray CT apparatus according to the first embodiment uses a selected heartbeat arbitrarily selected from the set number of heartbeats, and “180 degrees + α in a range obtained by extending the set phase range. X-ray exposure is controlled to collect projection data corresponding to “180 ° + α range” divided in the set phase range for other heartbeats. To do.

  For example, since the average heart rate of the subject before the tomography is 90 bpm, the X-ray CT apparatus in Example 1 is set as “number of segments: 3, phase range: systole to diastole” As the selected heart rate, the first heart rate (beat) after the start of tomography is selected, and as shown in FIG. 1, HALF reconstruction (half reconstruction) is performed in the first beat in a range obtained by extending the set phase range. The necessary period is set as the X-ray exposure period, and in the other second and third beats, projection data corresponding to the segment size is collected in the set phase range, that is, the set period is set to X Control the exposure period of the line.

  For this reason, the X-ray CT apparatus according to the first embodiment, for example, generates the first beat even if the arrhythmia occurs at the second and third beats and the projection data in the expected phase range cannot be collected. Thus, projection data necessary for HALF reconstruction (half reconstruction) can be collected, and projection data necessary for reconstruction of a tomographic image can always be guaranteed as described above.

  In this embodiment, the case where the first beat after the start of tomography is selected as the selected heartbeat has been described. However, the present invention is not limited to this, and the selected heartbeat may be other than after the start of tomography. The beat (for example, the second or third beat) may be selected. Further, when the number of segments set is “1”, the period required for HALF reconstruction (half reconstruction) is set in the set phase range or in the range in which the set phase range is expanded. Tomography is performed during the exposure period.

[Configuration of X-ray CT Apparatus in Embodiment 1]
Next, the X-ray CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the X-ray CT apparatus according to the first embodiment.

  As shown in FIG. 2, the X-ray CT apparatus according to the first embodiment includes a gantry device 10, a bed device 20, and a console device 30.

  The gantry 10 is an apparatus that collects projection data by exposing the subject P to X-rays, and includes a high voltage generator 11, an X-ray tube 12, an X-ray detector 13, and a data collector 14. , A rotating frame 15, a gantry driving unit 16, and an electrocardiograph 17.

  The high voltage generator 11 is a device that supplies a high voltage to the X-ray tube 12, and the X-ray tube 12 is a vacuum tube that generates X-rays by the high voltage supplied by the high voltage generator 11. The X-ray detector 13 is a detector that detects X-rays transmitted through the subject P, and the data collection unit 14 generates and collects projection data using the X-rays detected by the X-ray detector 13. It is a device to do.

  The rotating frame 15 is an annular frame that rotates continuously at high speed, and supports the X-ray tube 12 and the X-ray detector 13 so as to face each other with the subject P interposed therebetween. The gantry drive unit 16 is a drive device that rotates the rotary frame 15 to rotate the X-ray tube 12 and the X-ray detector 13 on a circular orbit around the subject P. The electrocardiograph 17 is a device that detects a weak current generated from the heart of the subject P via an electrode attached to the subject P, and outputs an electrocardiogram signal based on the detected current.

  The couch device 20 is a device on which the subject P is placed, and includes a couchtop 22 and a couch driving device 21. The top plate 22 is a plate on which the subject P is placed during imaging, and the bed driving device 21 is a device that moves the top plate 22 in the slice direction.

  The console device 30 is a device that accepts an operation of the X-ray CT apparatus by an operator and reconstructs a tomographic image from projection data collected by the gantry device 10, and includes an input device 31, a display device 32, and scan control. A unit 33, a preprocessing unit 34, a projection data storage unit 35, an image reconstruction processing unit 36, an image storage unit 37, a setting information storage unit 38, and a system control unit 39.

  The input device 31 is a device used by an operator to input an instruction to the X-ray CT apparatus, such as a mouse or a keyboard, and the display device 32 is a device that displays an image stored in an image storage unit 37 described later. . The scan control unit 33 drives the high voltage generation unit 11, the data collection unit 14, the gantry driving unit 16, and the bed driving device 21 under the control of the system control unit 39 to be described later, so that X is placed on the heart of the subject P. A processing unit that collects projection data by exposing a line.

  The preprocessing unit 34 is a processing unit that performs preprocessing such as sensitivity correction on the projection data generated by the data collection unit 14. The projection data storage unit 35 is a projection data that has been preprocessed by the preprocessing unit 34. Is a storage unit.

  The image reconstruction processing unit 36 is a processing unit that reconstructs an image from projection data stored in the projection data storage unit 35 under the control of a system control unit 39 described later. The image reconstruction processing unit 36 has a function of reconstructing a tomographic image by HALF reconstruction (half reconstruction), FULL reconstruction (full reconstruction), or segment reconstruction, and the operator of the X-ray CT apparatus Based on the instruction of the system control unit 39 that has received the input reconstruction conditions via the input device 31, reconstruction of the tomographic image, for example, HALF reconstruction (half reconstruction) using segment reconstruction is performed. .

  The image storage unit 37 is a storage unit that stores the tomographic image reconstructed by the image reconstruction processing unit 36. A display request for the tomographic image input by the operator of the X-ray CT apparatus is input via the input device 31. The received system control unit 39 extracts the tomographic image corresponding to the display request from the tomographic image stored in the image storage unit 37 and displays it on the display device 32.

  The system control unit 39 is a processing unit that performs overall control of the X-ray CT apparatus by controlling operations of the gantry device 10, the couch device 20, and the console device 30. For example, when electrocardiogram synchronous imaging is performed, the system control unit 39 is based on an instruction from an operator input using the input device 31 and an electrocardiogram signal output from the electrocardiograph 17. The projection data is collected by controlling the X-ray exposure from the X-ray tube 12 via the scan control unit 33.

  Specifically, the system control unit 39 outputs an instruction from the electrocardiograph 17 when receiving an instruction from the operator of the X-ray CT apparatus to “perform tomography by segment reconstruction” via the input device 31. The average heart rate of the subject P is calculated from the electrocardiogram signal, and the number of segments and the phase range are determined based on the setting information stored in the setting information storage unit 38. For example, the setting information storage unit 38 stores setting information indicating a low heart rate when the average heart rate is less than 60 bpm, a medium heart rate when the average heart rate is 60 bpm to 80 bpm, and a high heart rate when the average heart rate is greater than 80 bpm. The system control unit 39 sets “number of segments: 1, phase range: diastole” when the calculated average heart rate is a low heart rate, and “number of segments: 2” when it is a middle heart rate. , Phase range: systole to diastole ”, and set to“ number of segments: 3, phase range: systole ”for high heart rate. In the present embodiment, the phase range is an exposure phase in which projection data is collected by exposing X-rays.

  Further, the system control unit 39 drives the gantry via the scan control unit 33 so that the projection data corresponding to each of the divided segment sizes is collected during the execution of tomography when the number of segments and the phase range are set. The rotational phase of the X-ray tube 12 is adjusted by controlling the unit 16.

  Here, since the average heart rate of the subject before tomography is 90 bpm, the system control unit 39 sets “number of segments: 3, phase range: systole to diastole”, and the setting information storage unit Referring to “selected heartbeat: first heartbeat” which is the setting information stored in 38, the first beat is a period required for HALF reconstruction (half reconstruction) in the expanded range of the set phase range. In the other second and third beats, the projection data corresponding to the segment size is collected in the set phase range, that is, the set period is set as the X-ray exposure period. Control is performed (see FIG. 1).

[Procedure for Processing by X-ray CT Apparatus in Embodiment 1]
Next, the process by the X-ray CT apparatus in Example 1 is demonstrated using FIG. FIG. 3 is a diagram for explaining processing of the X-ray CT apparatus according to the first embodiment.

  As shown in FIG. 3, first, the system control unit 39 provided in the console device 30 constituting the X-ray CT apparatus in the first embodiment inputs an instruction “perform tomography by segment reconstruction” from the operator. When received via the device 31, the average heart rate of the subject P is calculated from the electrocardiogram signal output from the electrocardiograph 17, and the number of segments and the phase range are determined based on the setting information stored in the setting information storage unit 38. (Exposure phase) is set (Yes at step S301), and when the first R wave is detected in the electrocardiogram signal output from the electrocardiograph 17 (Yes at step S302), the exposure start time determined by the exposure phase X-ray exposure is started (step S303).

  Specifically, the system control unit 39 controls the scan control unit 33 so as to start the X-ray exposure from the exposure start time, and the scan control unit 33 controls the high voltage generation unit 11. Thus, a voltage is supplied to the X-ray tube 12, and the X-ray tube 12 starts X-ray exposure to the subject P.

  Then, the system control unit 39 refers to “selected heartbeat: first heartbeat” which is the setting information stored in the setting information storage unit 38, and at the first beat, HALF reconstruction is performed in a range obtained by extending the set phase range. After the period necessary for (half reconstruction) has elapsed, the exposure is terminated (step S304).

  After that, when the system control unit 39 detects an R wave in the electrocardiogram signal output from the electrocardiograph 17 (Yes in step S305), the system control unit 39 performs X-ray exposure from the exposure start time determined by the exposure phase. Start (step S306), and after the exposure period determined by the set exposure phase has elapsed, the exposure is terminated (step S307).

  Subsequently, the system control unit 39 determines whether X-ray exposure for the set number of segments has been performed, that is, whether the designated number of exposures has been reached (step S308). If the designated number of exposures has not been reached (No at Step S308), the system control unit 39 returns to Step S305 and waits until the next R wave is detected.

  On the other hand, when the designated number of exposures is reached (Yes at Step S308), the system control unit 39 ends the imaging (Step S309) and ends the process. Each time X-rays are exposed, projection data is generated and collected by the data collection unit 14, pre-processing by the pre-processing unit 34, and projection data after pre-processing by the projection data storage unit 35 is stored. After the tomography is completed, the image reconstruction processing unit 36 reconstructs an image from the projection data stored in the projection data storage unit 35 under the control of the system control unit 39.

[Effect of Example 1]
As described above, according to the first embodiment, even when a sudden change in the heart rate such as arrhythmia occurs, the projection data necessary for reconstruction of the tomographic image is collected at the selected heart rate. It becomes possible to always guarantee the projection data necessary for reconstruction.

  Further, according to the first embodiment, it is possible to avoid performing re-imaging because the projection data necessary for reconstruction of the tomographic image is not collected, so that unnecessary exposure of X-rays to the subject can be prevented. It becomes possible to do.

  In this embodiment, the case of performing tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction will be described. However, the present invention is not limited to this, and segment reconstruction is performed. It is also possible to perform tomographic imaging for performing FULL reconstruction (full reconstruction) using. In this embodiment, the case where X-ray exposure is performed only during the projection data collection period has been described. However, the present invention is not limited to this, and the exposure is performed during the projection data collection period. It may be a case where the intensity of X-rays is modulated to increase.

  In the second embodiment, a case will be described in which it is determined whether or not projection data not necessary for reconstruction of a tomographic image has been collected during imaging.

[Outline and Features of X-ray CT Apparatus in Embodiment 2]
First, the main features of the X-ray CT apparatus according to the second embodiment will be specifically described with reference to FIG. FIG. 4 is a diagram for explaining the outline and features of the X-ray CT apparatus according to the second embodiment.

  As in the first embodiment, the X-ray CT apparatus according to the second embodiment has an outline of performing HALF reconstruction (half reconstruction) using segment reconstruction in electrocardiogram synchronous imaging. The main feature is that only appropriate projection data can always be guaranteed.

  In other words, the X-ray CT apparatus according to the second embodiment collects projection data that has already been collected in the latest projection data collection range that is the latest projection data of the segment size corresponding to the divided “range of 180 degrees + α”. If the resonance overlaps with any of the ranges, the X-ray exposure is controlled so as to stop collecting new projection data.

  For example, as shown in FIG. 4, the X-ray CT apparatus according to the second embodiment collects projection data necessary for HALF reconstruction (half reconstruction) at the first beat, and then improves the time resolution. In the second and third heartbeats, projection data having a segment size corresponding to each range is collected. For example, from the detection time of the R wave generated immediately after the second projection data is collected, the following X The rotational phase of the X-ray tube is predicted during the radiation exposure period, and from the predicted rotational phase, the collection range of the projection data collected the third time, which is the latest data, is the collection range of the projection data collected the second time If the resonance overlaps with the above, the X-ray exposure is controlled so as to stop the collection of projection data at the third heartbeat.

  For this reason, in the X-ray CT apparatus according to the second embodiment, the collection range of the latest projection data has already been collected from the expected rotational phase of the X-ray tube when collecting the latest projection data. If it is determined that the projection data overlaps with any acquisition range, X-ray exposure can be stopped, and only projection data appropriate for reconstruction of tomographic images can be guaranteed at all times.

  In the present embodiment, projection data necessary for HALF reconstruction (half reconstruction) is collected at the selected heart rate, and whether or not projection data collected thereafter becomes resonance is determined. However, the present invention is not limited to this, and it is a case where it is determined in anticipation whether or not the latest projection data collected will be resonance without setting the selected heart rate. There may be.

  In the present embodiment, the case where the collection of projection data is stopped when it is determined to be resonance has been described. However, the present invention is not limited to this. For example, the number of segments is increased by a predetermined number. The projection data may be continuously collected without determining the resonance.

[Configuration of X-ray CT Apparatus in Embodiment 2]
Next, the X-ray CT apparatus in Example 2 is demonstrated using FIG. FIG. 2 is a block diagram illustrating the configuration of the X-ray CT apparatus according to the first embodiment. The X-ray CT apparatus according to the second embodiment has the same configuration as that of the X-ray CT apparatus according to the first embodiment. The content of processing performed by 39 is different from that of the first embodiment. Hereinafter, this will be mainly described.

  As in the first embodiment, the system control unit 39 in the second embodiment uses the scan control unit 33 to collect projection data necessary for HALF reconstruction (half reconstruction) at the first beat that is the selected heartbeat. After the control, in order to improve the time resolution, the scan control unit 33 is controlled so as to collect projection data of the segment sizes corresponding to the respective ranges in the second and third heartbeats. As shown in FIG. 4, immediately after the second projection data is collected, X-rays in the next X-ray exposure period are detected from the detection time of the R wave detected by the electrocardiogram signal collected by the electrocardiograph 17. When the rotation phase of the tube 12 is predicted, and it is determined that the collection range of the projection data collected for the third time, which is the latest data, becomes resonance based on the predicted rotation phase, It takes to stop the acquisition of projection data, i.e., to stop the X-ray exposure, and controls the scan control unit 33.

[Processing Procedure by X-ray CT Apparatus in Embodiment 2]
Next, the process by the X-ray CT apparatus in Example 2 is demonstrated using FIG. FIG. 5 is a diagram for explaining processing of the X-ray CT apparatus according to the second embodiment.

  As shown in FIG. 5, first, the system control unit 39 included in the console device 30 constituting the X-ray CT apparatus in the second embodiment performs “tomographic imaging by segment reconstruction” as in the first embodiment. Is received via the input device 31, the average heart rate of the subject P is calculated from the electrocardiogram signal output from the electrocardiograph 17, and based on the setting information stored in the setting information storage unit 38. Then, the number of segments and the phase range (exposure phase) are set (Yes in step S501), and the first R wave is detected in the electrocardiogram signal output from the electrocardiograph 17 (Yes in step S502). X-ray exposure is started from the determined exposure start time (step S503).

  Then, the system control unit 39 refers to “selected heartbeat: first heartbeat” which is the setting information stored in the setting information storage unit 38, and at the first beat, HALF reconstruction is performed in a range obtained by extending the set phase range. After the period necessary for (half reconstruction) has elapsed, the exposure is terminated (step S504).

  Thereafter, when the system control unit 39 detects an R wave in the electrocardiogram signal output from the electrocardiograph 17 (Yes in step S505), the system control unit 39 determines whether or not the collection range in the next projection data is resonance. (Step S506). In the present embodiment, when the R wave at the second heartbeat is detected, the projection data collected at the first time is data corresponding to “range of 180 degrees + α”, and therefore, forcibly. It is determined that it is not resonance. Further, when the R wave at the third heartbeat is detected, it is determined whether or not the second range of the collected projection data is within the collection range and resonance.

  Here, if the system control unit 39 determines that resonance is to occur (Yes at Step S507), the subsequent collection of projection data is stopped, imaging is terminated (Step S511), and the process is terminated.

  On the other hand, if the system control unit 39 determines that the resonance is not achieved (No in step S507), the system control unit 39 starts the X-ray exposure from the exposure start time determined by the exposure phase (step S508), and is set. After the exposure period determined by the exposed exposure phase has elapsed, the exposure is terminated (step S509).

  Subsequently, the system control unit 39 determines whether or not the specified number of exposures has been reached (step S510). Here, when the designated number of exposures is reached (Yes at Step S510), the system control unit 39 ends the imaging (Step S511) and ends the processing.

  On the other hand, when the designated number of exposures has not been reached (No at Step S510), the system control unit 39 returns to Step S505 and detects the R wave in the electrocardiogram signal output from the electrocardiograph 17. Wait until.

[Effect of Example 2]
As described above, according to the second embodiment, the collection range of the latest projection data is any of the projection data that has already been collected from the expected rotation phase of the X-ray tube when collecting the latest projection data. X-ray exposure can be stopped and only projection data appropriate for tomographic image reconstruction can always be guaranteed.

  In this embodiment, the case of performing tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction will be described. However, the present invention is not limited to this, and segment reconstruction is performed. It is also possible to perform tomographic imaging for performing FULL reconstruction (full reconstruction) using. In this embodiment, the case where X-ray exposure is performed only during the projection data collection period has been described. However, the present invention is not limited to this, and the exposure is performed during the projection data collection period. It may be a case where the intensity of X-rays is modulated to increase.

  In the first embodiment described above, the case where the projection data necessary for reconstruction of the tomographic image is collected at the first heartbeat has been described. However, in the third embodiment, the already collected projection data is used to reconstruct the tomographic image. Only when the above condition is not satisfied will be described a case where projection data necessary for reconstruction of a tomographic image is collected at the last heartbeat.

[Outline and Features of X-ray CT Apparatus in Embodiment 3]
First, the main features of the X-ray CT apparatus according to the third embodiment will be specifically described with reference to FIG. FIG. 6 is a diagram for explaining the outline and features of the X-ray CT apparatus according to the third embodiment.

  As in Example 1, the X-ray CT apparatus in Example 3 outlines that HALF reconstruction (half reconstruction) using segment reconstruction is performed in electrocardiogram synchronous imaging, and unnecessary X-ray exposure is performed. The main feature is that it is possible to always guarantee projection data necessary for reconstruction of tomographic images after prevention.

  That is, the X-ray CT apparatus according to the third embodiment selects the final heartbeat that is the heartbeat of the number of segments (third time in the present embodiment) as the selected heartbeat, and the projection data that has already been collected until the final heartbeat occurs. If it is determined that the tomographic image cannot be reconstructed by HALF (half reconstruction), the period required for the HALF reconstruction (half reconstruction) is expanded in the range where the set phase range is expanded in the final heartbeat. If it is determined that the tomographic image can be HALF reconstructed (half reconstructed) with the projection data already collected until the final heartbeat occurs, the segment size corresponds to the set phase range. Control is performed so that projection data is collected, that is, the set period is the X-ray exposure period.

  For example, in the X-ray CT apparatus according to the third embodiment, the projection data collected as corresponding to the segment size in the set phase range at each of the first and second beats, as shown in FIG. In the case of resonance, the condition for reconstructing the tomographic image HALF (half reconstruction) is not satisfied, so the period required for HALF reconstruction (half reconstruction) is used for the final heartbeat, which is the third beat. Is the exposure period. Although not shown in the figure, the projection data collected at the first and second beats is the projection data in the set phase range due to the occurrence of arrhythmia (for example, not the systole but the diastole). (Projection data in the phase range of (2)) is determined not to satisfy the conditions for HALF reconstruction (half reconstruction) of the tomographic image.

  For this reason, the X-ray CT apparatus according to the third embodiment can reconstruct a tomographic image at the last heartbeat only when the already acquired projection data does not satisfy the conditions for reconstructing the tomographic image. Since necessary projection data is collected, it is possible to always guarantee projection data necessary for reconstruction of tomographic images while preventing unnecessary X-ray exposure.

[Configuration of X-ray CT Apparatus in Embodiment 3]
Next, the X-ray CT apparatus in Example 3 is demonstrated using FIG. FIG. 2 is a block diagram illustrating the configuration of the X-ray CT apparatus according to the first embodiment. The X-ray CT apparatus according to the third embodiment has the same configuration as the X-ray CT apparatus according to the first embodiment, but stores setting information. The content stored in the unit 38 and the processing content performed by the system control unit 39 are different from those in the first embodiment. Hereinafter, this will be mainly described.

  The setting information storage unit 38 according to the third embodiment stores the selection of the final heart rate, which is the number-of-segment heart rate, as the selected heart rate. For example, the system control unit 39 sets the number of segments to be “3”. If this happens, the third heartbeat after the start of imaging is stored as the selected heartbeat.

  As in the first embodiment, the system control unit 39 according to the third embodiment sets the number of segments and the phase range. For example, from the set number of segments “3”, the third final heartbeat is set as the selected heartbeat. When the projection data collected as corresponding to the segment size in the set phase range is, for example, resonance in each of the first and second beats, the system control unit 39 displays a tomographic image. Since the conditions for HALF reconstruction (half reconstruction) are not satisfied, scan control is performed so that the period required for HALF reconstruction (half reconstruction) is the exposure period for the final heartbeat, which is the third beat. The unit 33 is controlled.

[Processing Procedure by X-ray CT Apparatus in Example 3]
Next, processing performed by the X-ray CT apparatus according to the third embodiment will be described with reference to FIG. FIG. 7 is a diagram for explaining processing of the X-ray CT apparatus according to the third embodiment.

  As shown in FIG. 7, first, the system control unit 39 included in the console device 30 constituting the X-ray CT apparatus according to the third embodiment is similar to the first and second embodiments. When an instruction to “perform tomography” is received via the input device 31, the average heart rate of the subject P is calculated from the electrocardiogram signal output from the electrocardiograph 17 and stored in the setting information storage unit 38. Based on the setting information, the number of segments and the phase range (exposure phase) are set (Yes at Step S701), and when the first R wave is detected in the electrocardiogram signal output from the electrocardiograph 17 (Yes at Step S702), X-ray exposure is started from the exposure start time determined by the exposure phase (step S703), and after the exposure period determined by the set exposure phase has elapsed, the exposure is terminated (scan). -Up S704).

  Then, the system control unit 39 determines whether or not the next X-ray exposure is the specified number of exposures (segment number) (step S705), and the next X-ray exposure is If it is not the exposure of the designated number of exposures (No at step S705), the process returns to step S702 and waits until the next R wave is detected.

  On the other hand, when the next X-ray exposure is the specified number of times of exposure (Yes at Step S705), the system control unit 39 waits until the next R wave is detected at Step S706. To do.

  Here, when the next R wave is detected (Yes in step S706), the system control unit 39 collects the projection data collected so far (in this embodiment, the projection data collected in the first and second heartbeats). ) Satisfies the conditions for HALF reconstruction (half reconstruction) of tomographic images, that is, is there any data that guarantees HALF reconstruction (half reconstruction) in the data collected so far? It is determined whether or not (step S707).

  When the projection data collected so far is data that guarantees HALF reconstruction (half reconstruction) (Yes at step S707), the system control unit 39 determines the X-ray from the exposure start time determined by the exposure phase. After the exposure period determined by the set exposure phase has elapsed, the exposure ends (step S709), the imaging ends (step S710), and the process ends.

  On the other hand, if the projection data collected so far is not data that guarantees HALF reconstruction (half reconstruction) (No in step S707), the system control unit 39 expands the set phase range. After a period necessary for HALF reconstruction (half reconstruction) has elapsed, exposure is terminated (step S708), imaging is terminated (step S710), and the process is terminated.

[Effect of Example 3]
As described above, according to the third embodiment, only when the already collected projection data does not satisfy the condition for reconstructing the tomographic image, the projection data necessary for the reconstruction of the tomographic image at the last heartbeat. Therefore, it is possible to always guarantee projection data necessary for reconstruction of tomographic images while preventing unnecessary X-ray exposure.

  In this embodiment, the case of performing tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction will be described. However, the present invention is not limited to this, and segment reconstruction is performed. It is also possible to perform tomographic imaging for performing FULL reconstruction (full reconstruction) using. In this embodiment, the case where X-ray exposure is performed only during the projection data collection period has been described. However, the present invention is not limited to this, and the exposure is performed during the projection data collection period. It may be a case where the intensity of X-rays is modulated to increase.

  In the fourth embodiment, a case will be described in which projection data necessary for image reconstruction is collected after analyzing the characteristics of the heartbeat of the subject before tomography.

[Outline and Features of X-ray CT Apparatus in Embodiment 4]
First, the main features of the X-ray CT apparatus according to the fourth embodiment will be specifically described with reference to FIG. FIG. 8 is a diagram for explaining the outline and features of the X-ray CT apparatus according to the fourth embodiment.

  The X-ray CT apparatus according to the fourth embodiment has an outline of performing HALF reconstruction (half reconstruction) in electrocardiogram synchronous imaging, and always guarantees projection data necessary for reconstruction of tomographic images corresponding to arrhythmia. The main feature is that it becomes possible.

  That is, in the X-ray CT apparatus according to the fourth embodiment, the R wave appearance interval (RR interval) in the electrocardiogram signal collected before the start of tomography consists of a plurality of different RR intervals, and the plurality of different ones. It is determined whether or not at least one of the RR intervals is a collectable appearance interval at which projection data required for HALF reconstruction (half reconstruction) of a tomographic image can be collected at a time. .

  For example, some arrhythmias, such as a two-stage pulse, appear alternately and repeatedly with short RR intervals. That is, as shown in FIG. 8 (A), a two-stage pulse is one in which normal R waves and abnormal R waves appear alternately, and ones with short RR intervals and ones with long ones are alternated. Appears repeatedly.

  Here, the X-ray CT apparatus according to Example 4 calculates the RR interval in the electrocardiogram signal collected from the electrocardiograph, for example, 10 times, and creates a histogram indicating the frequency of the calculated RR interval. It is determined whether or not a different RR interval appears in the histogram. For example, as shown in FIG. 8B, if all the calculated RR intervals are within the same range in the created histogram, it is determined that no arrhythmia has occurred in the subject, and ( As shown in C), if the calculated RR interval is divided into two different ranges in the created histogram, it is determined that an arrhythmia that is a two-stage pulse has occurred in the subject.

  In the X-ray CT apparatus according to the fourth embodiment, for example, as shown in FIG. 8C, the longer RR interval among the RR intervals divided into two different ranges has a tomographic image HALF reconstructed ( It is determined by using a predetermined threshold whether or not the projection data required for performing the half reconstruction is a collectable appearance interval at which the projection data can be collected at one time. Here, as shown in FIG. 8C, since the longer RR interval is larger than a predetermined threshold, it is determined that the longer RR interval is a collectable appearance interval.

  The X-ray CT apparatus according to the fourth embodiment collects from the RR interval in the electrocardiogram signal collected after the start of tomography, for example, when the arrhythmia of the subject is a two-stage pulse including an acquirable appearance interval. A heartbeat as a possible appearance interval is predicted, and X-ray exposure is controlled so that projection data required for HALF reconstruction (half reconstruction) of a tomographic image is performed once at the predicted heartbeat.

  That is, in the X-ray CT apparatus according to the fourth embodiment, when the RR interval calculated from the electrocardiogram signal collected after the start of tomography is the shorter RR interval calculated before the start of tomography, Next, the heartbeat that detected the R wave is predicted to be a heartbeat having a long RR interval that is a collectable appearance interval, and as shown in FIG. X-ray exposure is controlled so that data for a period necessary for HALF reconstruction (half reconstruction) is collected.

  For this reason, in the X-ray CT apparatus according to the fourth embodiment, if the arrhythmia pattern of the subject is determined in advance as a two-stage pulse and the longer RR interval is a collectable appearance interval, Since data for a period necessary for reconstruction can be collected at a time in anticipation of a certain heartbeat, projection data necessary for reconstruction of tomographic images can always be guaranteed.

[Configuration of X-ray CT Apparatus in Embodiment 4]
Next, an X-ray CT apparatus according to the fourth embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating the configuration of the X-ray CT apparatus according to the first embodiment. The X-ray CT apparatus according to the fourth embodiment has the same configuration as the X-ray CT apparatus according to the first embodiment, but stores setting information. The content stored in the unit 38 and the processing content performed by the system control unit 39 are different from those in the first embodiment. Hereinafter, this will be mainly described.

  The setting information storage unit 38 according to the fourth embodiment stores a threshold value used for determining a collectable appearance interval.

  The system control unit 39 in the fourth embodiment calculates an RR interval in an electrocardiogram signal collected from the electrocardiograph 17 before imaging, creates a histogram indicating the frequency of the calculated RR interval, It is determined whether or not a different RR interval appears (see FIGS. 8B and 8C). Then, the system control unit 39 collects projection data required for HALF reconstruction (half reconstruction) of the tomographic image at a time with the longer RR interval among the RR intervals divided into two different ranges at a time. It is determined using the threshold value stored in the setting information storage unit 38 whether or not it is a collectable appearance interval that can be performed. Here, for example, as shown in FIG. 8C, the system control unit 39 determines that the longer RR interval is a collectable appearance interval because the longer RR interval is larger than the threshold value. judge.

  Then, for example, when the arrhythmia of the subject P is a two-stage pulse including a collectable appearance interval, the system control unit 39 determines the collectable appearance interval from the RR interval in the electrocardiogram signal collected after the start of tomography. X-ray exposure is controlled so that projection data required for HALF reconstruction (half reconstruction) of the tomographic image is collected at a time at the predicted heartbeat (see FIG. 8 (D)).

  In addition, although the present Example demonstrated the case where the system control part 39 determined that it was a two-stage pulse including the collection | recoverable appearance interval, this invention is not limited to this, For example, X-ray | X_line It may be a case where the operator of the CT apparatus refers to the electrocardiogram waveform of the electrocardiograph 17 and determines whether or not it is a two-stage pulse including a collectable appearance interval.

[Processing Procedure by X-ray CT Apparatus in Embodiment 4]
Next, processing performed by the X-ray CT apparatus according to the fourth embodiment will be described with reference to FIG. FIG. 9 is a diagram for explaining processing of the X-ray CT apparatus according to the fourth embodiment.

  As shown in FIG. 9, first, the system control unit 39 provided in the console device 30 that constitutes the X-ray CT apparatus in the fourth embodiment uses the electrocardiogram signal collected from the electrocardiograph 17 before imaging to examine the subject. If it is determined that the pulse P is a two-stage pulse including the collection-appearable appearance interval (Yes at step S901), a phase range (exposure phase) is set (step S902). In this case, the system control unit 39 sets a range in which projection data required for HALF reconstruction (half reconstruction) can be collected at a time as the exposure phase.

  When the system control unit 39 detects a heartbeat (beat) with a short RR interval (Yes in step S903), the system control unit 39 determines that the next heartbeat is a collectable appearance interval, and starts exposure determined by the exposure phase. X-ray exposure is started from time, and after a period necessary for HALF reconstruction (half reconstruction) has elapsed, the exposure is terminated (step S904), the imaging is terminated (step S905), and the process is terminated. .

[Effect of Example 4]
As described above, according to the fourth embodiment, if the arrhythmia pattern of the subject is determined in advance as a two-stage pulse and the longer RR interval is a collectable appearance interval, a heartbeat that is a collectable appearance interval is predicted. Since data for a period necessary for reconstruction can be collected at a time, the main feature is that projection data necessary for reconstruction of tomographic images can always be guaranteed.

  Here, in the present embodiment, the case where the pattern of the arrhythmia of the subject is a two-stage pulse has been described, but the present invention is not limited to this, for example, as shown in FIG. The case where the pattern of arrhythmia is a three-stage pulse may be used. Here, FIG. 10 is a diagram for explaining the processing content for the third pulse of the X-ray CT apparatus according to the fourth embodiment.

  As in the case of the 2-stage pulse, the three-stage pulse appears alternately with a short RR interval and a long RR interval. However, with the 3-stage pulse, a pattern with a short, short, long RR interval is repeated. It is. That is, in the case of the three-stage pulse, as in the case of the two-stage pulse, when the RR interval is calculated and a histogram indicating the frequency of the calculated RR interval is created, the histogram shown in FIG. 10 is obtained. Then, as in the case of the two-stage pulse, it is determined using a predetermined threshold value whether or not the longer RR interval is a collectable appearance interval.

  As described above, if the arrhythmia of the subject has a certain pattern and includes the collectable appearance intervals, the processing of the present embodiment can be applied.

  In this embodiment, the case of performing tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction will be described. However, the present invention is not limited to this, and segment reconstruction is performed. It is also possible to perform tomographic imaging for performing FULL reconstruction (full reconstruction) using. In this embodiment, the case where X-ray exposure is performed only during the projection data collection period has been described. However, the present invention is not limited to this, and the exposure is performed during the projection data collection period. It may be a case where the intensity of X-rays is modulated to increase.

  In the fourth embodiment described above, the case where the projection data necessary for image reconstruction is collected after analyzing the characteristics of the heartbeat of the subject before tomography is described. In the fifth embodiment, the tomography is being performed. Next, a case will be described in which the characteristics of the heartbeat of the subject are detected and projection data necessary for image reconstruction is collected.

[Outline and Features of X-ray CT Apparatus in Embodiment 5]
First, the main features of the X-ray CT apparatus according to the fifth embodiment will be specifically described with reference to FIG. FIG. 11 is a diagram for explaining the outline and features of the X-ray CT apparatus according to the fifth embodiment.

  As in Example 1, the X-ray CT apparatus in Example 5 outlines that HALF reconstruction (half reconstruction) using segment reconstruction is performed in ECG-synchronous imaging, and unnecessary X-ray exposure is performed. The main feature is that it is possible to always guarantee projection data necessary for reconstruction of tomographic images after prevention.

  That is, the X-ray CT apparatus according to the fifth embodiment determines the number of segments and the phase range from the average heart rate of the subject collected before the start of tomography, and uses segment reconstruction as in the first embodiment. The tomography is performed to perform the HALF reconstruction (half reconstruction), but the X-ray exposure start phase is set from the electrocardiogram signals collected in advance, and then the R wave is detected from the exposure start phase. This is different from the first embodiment in that the range is set as a phase range as an exposure period in which X-rays are exposed. For example, when the average heart rate of the subject is a high heart rate greater than 80 bpm, the X-ray CT apparatus according to the fifth embodiment sets “number of segments: 3” and applies a predetermined phase of the systole to the exposure. Set as start phase.

  In the X-ray CT apparatus according to the fifth embodiment, the projection data collected during execution of tomography is necessary projection data that is necessary for HALF reconstruction (half reconstruction) of a tomographic image. If so, the X-ray exposure is controlled so as to stop collecting new projection data.

  Here, some arrhythmias have long RR intervals due to atrial fibrillation, as shown in FIG. Therefore, in the X-ray CT apparatus according to the fifth embodiment in which the exposure end time is set until the next R wave is detected, as shown in FIG. If the acquired data is the necessary projection data, the X-ray exposure is controlled to stop collecting new projection data, and the imaging is finished. .

  For this reason, the X-ray CT apparatus according to the fifth embodiment, for example, when arrhythmia having a long RR interval occurs due to atrial fibrillation and collects data for a period necessary for reconstruction at a time, Since the imaging can be completed, it is possible to always guarantee projection data necessary for reconstruction of a tomographic image while preventing unnecessary X-ray exposure.

[Configuration of X-ray CT Apparatus in Embodiment 5]
Next, an X-ray CT apparatus according to the fifth embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating the configuration of the X-ray CT apparatus according to the first embodiment. The X-ray CT apparatus according to the fifth embodiment has the same configuration as the X-ray CT apparatus according to the first embodiment, but stores setting information. The content stored in the unit 38 and the processing content performed by the system control unit 39 are different from those in the first embodiment. Hereinafter, this will be mainly described.

  For example, the setting information storage unit 38 according to the fifth embodiment has a low heart rate when the average heart rate is less than 60 bpm, a medium heart rate when the average heart rate is 60 bpm to 80 bpm, and a case when the average heart rate is greater than 80 bpm, as in the first embodiment. If the average heart rate calculated by the system control unit 39 is a low heart rate, “number of segments: 1, exposure start phase: predetermined set phase in diastole” is stored. If the heart rate is middle heart rate, it is stored as “number of segments: 2, exposure start phase: first set phase in systole”, and if the heart rate is high, “number of segments: 3, exposure time”. Shooting start phase: stored as “second set phase in systole”.

  The system control unit 39 according to the fifth embodiment calculates an average heart rate from the RR interval in the electrocardiogram signal collected from the electrocardiograph 17 before imaging, and the calculated average heart rate and the setting information storage unit 38 store it. The number of segments and the exposure start phase are determined with reference to the setting information to be performed.

  Further, the system control unit 39 is a period in which the collection period of projection data collected during the execution of tomography is a period during which HALF reconstruction (half reconstruction) can be guaranteed, and the collected data is necessary projection data. Controls the X-ray exposure so as to stop the collection of new projection data, and ends the imaging.

[Processing Procedure by X-ray CT Apparatus in Example 5]
Next, processing performed by the X-ray CT apparatus according to the fifth embodiment will be described with reference to FIG. FIG. 12 is a diagram for explaining processing of the X-ray CT apparatus according to the fifth embodiment.

  As shown in FIG. 12, first, the system control unit 39 included in the console device 30 constituting the X-ray CT apparatus in the fifth embodiment is similar to the first to third embodiments in that the operator performs “tomographic imaging by segment reconstruction”. Is received via the input device 31, the average heart rate of the subject is calculated from the electrocardiogram signal output from the electrocardiograph 17, and the setting information stored in the setting information storage unit 38 is stored in the setting information. Based on this, the number of segments and the exposure start phase are set (Yes at Step S1201), and when an R wave is detected in the electrocardiogram signal output from the electrocardiograph 17 (Yes at Step S1202), it is determined by the exposure start phase. X-ray exposure is started from the exposure start time (step S1203).

  Then, when detecting the next R wave in the electrocardiogram signal output from the electrocardiograph 17 (step S1204), the system control unit 39 controls to end the X-ray exposure (step S1205), and HALF It is determined whether or not projection data has been collected for a period during which reconstruction (half reconstruction) can be guaranteed (step S1206).

  Here, if the system control unit 39 determines that projection data has not been collected for a period in which HALF reconstruction (half reconstruction) can be guaranteed (No in step S1206), it determines whether or not the specified number of exposures has been reached. If it is determined (step S1207) and the designated number of exposures has not been reached (No at step S1207), the process returns to step S1203 and waits until the X-ray exposure start time is reached. On the other hand, when the next X-ray exposure has reached the designated number of exposures (Yes at Step S1207), the system control unit 39 ends the imaging (Step S1208) and ends the processing.

  On the other hand, if the system control unit 39 determines that the projection data has been collected for a period in which HALF reconstruction (half reconstruction) can be guaranteed (Yes in step S1206), the system control unit 39 ends the imaging (step S1208) and performs processing. finish.

[Effect of Example 5]
As described above, according to the fifth embodiment, for example, when an arrhythmia having a long RR interval occurs due to atrial fibrillation and data for a period necessary for reconstruction is collected at a time, imaging is terminated. Therefore, it is possible to always guarantee projection data necessary for reconstruction of tomographic images while preventing unnecessary X-ray exposure.

  In this embodiment, the case of performing tomography for performing HALF reconstruction (half reconstruction) using segment reconstruction will be described. However, the present invention is not limited to this, and segment reconstruction is performed. It is also possible to perform tomographic imaging for performing FULL reconstruction (full reconstruction) using. In this embodiment, the case where X-ray exposure is performed only during the projection data collection period has been described. However, the present invention is not limited to this, and the exposure is performed during the projection data collection period. It may be a case where the intensity of X-rays is modulated to increase.

  Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Further, all or any part of each processing function performed in each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

  The tomography method described in the present embodiment can be realized by executing a program prepared in advance on a computer such as a personal computer or a workstation. This program can be distributed via a network such as the Internet. The program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, and a DVD and being read from the recording medium by the computer.

  As described above, the X-ray computed tomography apparatus and the imaging method according to the present invention are useful when performing image reconstruction based on electrocardiogram synchronization, and in particular, always guarantee projection data necessary for image reconstruction. Suitable for doing.

It is a figure for demonstrating the outline | summary and the characteristic of the X-ray CT apparatus in Example 1. FIG. 1 is a block diagram showing a configuration of an X-ray CT apparatus in Embodiment 1. FIG. It is a figure for demonstrating the process of the X-ray CT apparatus in Example 1. FIG. It is a figure for demonstrating the outline | summary and the characteristic of the X-ray CT apparatus in Example 2. FIG. It is a figure for demonstrating the process of the X-ray CT apparatus in Example 2. FIG. It is a figure for demonstrating the outline | summary and the characteristic of the X-ray CT apparatus in Example 3. FIG. FIG. 10 is a diagram for explaining processing of an X-ray CT apparatus according to a third embodiment. It is a figure for demonstrating the outline | summary and the characteristic of the X-ray CT apparatus in Example 4. FIG. FIG. 10 is a diagram for explaining processing of an X-ray CT apparatus according to a fourth embodiment. It is a figure for demonstrating the processing content with respect to the 3 step pulse of the X-ray CT apparatus in Example 4. FIG. It is a figure for demonstrating the outline | summary and the characteristic of the X-ray CT apparatus in Example 5. FIG. FIG. 10 is a diagram for explaining processing of an X-ray CT apparatus according to a fifth embodiment. It is a figure for demonstrating a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stand apparatus 11 High voltage generation part 12 X-ray tube 13 X-ray detector 14 Data collection part 15 Rotating frame 16 Mount drive part 17 Electrocardiograph 20 Sleeper apparatus 21 Sleeper drive apparatus 22 Top plate 30 Console apparatus 31 Input apparatus 32 Display Device 33 Scan control unit 34 Preprocessing unit 35 Projection data storage unit 36 Image reconstruction processing unit 37 Image storage unit 38 Setting information storage unit 39 System control unit

Claims (11)

X-ray computed tomography apparatus that collects electrocardiogram information of a subject, collects projection data by exposing X-rays to the subject, and reconstructs an image based on the collected electrocardiogram information and projection data Because
X-ray control means for controlling the start and stop of X-ray exposure or modulation control of X-ray intensity based on the electrocardiogram information;
Image reconstruction processing means for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats With
The X-ray control means performs control so as to extend an X-ray exposure period or a period during which the X-ray intensity is strong in at least one heart beat period among a plurality of heart beats used for reconstruction of the image. X-ray computed tomography apparatus.   The X-ray control means performs control so as to extend an X-ray exposure period or a period with a high X-ray intensity in a first heart beat period among a plurality of heart beats used for the reconstruction. The X-ray computed tomography apparatus according to claim 1.   The X-ray control means, based on the electrocardiogram information, when it is determined that the projection data necessary for the reconstruction cannot be collected, in the last heartbeat period of the plurality of heartbeats used for the reconstruction, 2. The X-ray computed tomography apparatus according to claim 1, wherein the X-ray computed tomography apparatus is controlled so as to extend an X-ray exposure period or a period during which the X-ray intensity is strong. X-ray computed tomography apparatus that collects electrocardiogram information of a subject, collects projection data by exposing X-rays to the subject, and reconstructs an image based on the collected electrocardiogram information and projection data Because
X-ray control means for controlling the start and stop of X-ray exposure or modulation control of X-ray intensity based on the electrocardiogram information;
Image reconstruction processing means for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats With
When the newly collected projection data overlaps any of the already collected projection data, the X-ray control means increases the number of heartbeats for collecting the projection data and continues to collect the projection data. Or an X-ray computed tomography apparatus that controls X-ray exposure so as to stop the collection of projection data. X-ray computed tomography apparatus that collects electrocardiogram information of a subject, collects projection data by exposing X-rays to the subject, and reconstructs an image based on the collected electrocardiogram information and projection data Because
X-ray control means for controlling the start and stop of X-ray exposure or modulation control of X-ray intensity based on the electrocardiogram information;
Image reconstruction processing means for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats With
The X-ray control means includes an appearance interval of feature waves in the electrocardiogram information collected before the start of imaging consisting of a plurality of different appearance intervals, and at least one of the plurality of different appearance intervals represents the image. The feature wave in the electrocardiogram information collected after the start of imaging when the necessary projection data, which is projection data required for reconstruction, is a collectable appearance interval that can be collected at a time. From the appearance interval, a heartbeat that is the collectable appearance interval is predicted, and control of the start and stop of X-ray exposure so as to collect the necessary projection data at the predicted heartbeat, or X-ray An X-ray computed tomography apparatus characterized by performing intensity modulation control. Determination means for determining whether or not the collectable appearance interval is included in the electrocardiogram information collected before the start of tomography,
The X-ray control means, when the determining means determines that the collectable appearance interval is included, from the appearance interval of the characteristic wave in the electrocardiogram information collected after the start of tomography, the collectable appearance Predicting a heartbeat as an interval, and controlling the start and stop of X-ray exposure or modulation control of X-ray intensity so as to collect the necessary projection data at the predicted heartbeat. The X-ray computed tomography apparatus according to claim 5. X-ray computed tomography apparatus that collects electrocardiogram information of a subject, collects projection data by exposing X-rays to the subject, and reconstructs an image based on the collected electrocardiogram information and projection data Because
X-ray control means for controlling the start and stop of X-ray exposure or modulation control of X-ray intensity based on the electrocardiogram information;
Image reconstruction processing means for reconstructing an image corresponding to a predetermined electrocardiographic phase by determining a section of projection data used for reconstruction based on the electrocardiogram information and combining projection data corresponding to a plurality of heartbeats With
The X-ray control means, based on the electrocardiogram information, exposes X-rays if the projection data collected during imaging is projection data required for reconstructing the image. An X-ray computed tomography apparatus which is controlled to stop shooting or to reduce the intensity of X-rays. An image capturing method for collecting electrocardiogram information of a subject, exposing X-rays to the subject, collecting projection data, and reconstructing an image based on the collected electrocardiogram information and projection data ,
Based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the X-ray intensity;
An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; Including,
The X-ray control step performs control so as to extend an X-ray exposure period or a period where the X-ray intensity is strong in at least one heart beat period among a plurality of heart beats used for reconstruction of the image. An image photographing method characterized by the above. An image capturing method for collecting electrocardiogram information of a subject, exposing X-rays to the subject, collecting projection data, and reconstructing an image based on the collected electrocardiogram information and projection data ,
Based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the X-ray intensity;
An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; Including,
In the X-ray control step, when newly collected projection data overlaps any of the already collected projection data, the number of heartbeats for collecting the projection data is increased and the collection of the projection data is continued. Or X-ray exposure is controlled so as to stop the collection of projection data. An image capturing method for collecting electrocardiogram information of a subject, exposing X-rays to the subject, collecting projection data, and reconstructing an image based on the collected electrocardiogram information and projection data ,
Based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the X-ray intensity;
An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; Including,
In the X-ray control step, the appearance interval of the characteristic wave in the electrocardiogram information collected before the start of imaging is a repetition of a plurality of different appearance intervals, and at least one of the plurality of different appearance intervals represents the image. The feature wave in the electrocardiogram information collected after the start of imaging when the necessary projection data, which is projection data required for reconstruction, is a collectable appearance interval that can be collected at a time. From the appearance interval, a heartbeat that is the collectable appearance interval is predicted, and control of the start and stop of X-ray exposure so as to collect the necessary projection data at the predicted heartbeat, or X-ray An image photographing method characterized by performing intensity modulation control. An image capturing method for collecting electrocardiogram information of a subject, exposing X-rays to the subject, collecting projection data, and reconstructing an image based on the collected electrocardiogram information and projection data ,
Based on the electrocardiogram information, an X-ray control process for controlling the start and stop of X-ray exposure or the modulation control of the X-ray intensity;
An image reconstruction processing step of determining a section of projection data used for reconstruction based on the electrocardiogram information, and reconstructing an image corresponding to a predetermined electrocardiographic phase by combining projection data corresponding to a plurality of heartbeats; Including,
In the X-ray control step, if the projection data collected during the execution of imaging based on the electrocardiogram information is the projection data required to reconstruct the image, the X-ray exposure step is performed. An image capturing method characterized by controlling to stop shooting or to reduce the intensity of X-rays.

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