JP2009207686A - Electrocardiographic-synchronous scan method and x-ray computed tomography apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To retain the quality of an image and set an appropriate X-ray tube current value preventing an excessive X-ray exposure, without depending on an experience and judgment of an inspection engineer in an electrocardiographic-synchronized helical scan. <P>SOLUTION: A scanographic image of a subject P is acquired, an SD setting section 30 sets the SD value of a CT value of the scanographic image, a change in X-ray tube current value I passing through the X-ray tube 4 is found based on the SD value, a maximum X-ray tube current setting section 31 sets a maximum X-ray tube current value Im based on the change in X-ray tube current value I, the X-ray tube 4 is rotated to expose the subject P to the X-ray in a state where an electrocardiographic-synchronous scan section 32 feeds the maximum X-ray tube current value Im to the X-ray tube 4, a two-dimensional X-ray detector 5 detects the X-ray transmitted through the subject P and the projection data are generated and collected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ECG-gated scanning method for collecting projection data according to a specific heartbeat phase of a subject such as a human body, and X-ray CT by reconstructing the projection data collected by this ECG-gated scanning method. The present invention relates to an X-ray computed tomography apparatus for acquiring an image.

  An X-ray CT apparatus has a technology called real EC. This real EC automatically calculates the tube current (mA) flowing in the X-ray tube with respect to the image SD (standard deviation) designated from the CT value of the scanogram, and the tube current is calculated for each rotation of the X-ray tube. Is required. A technique related to real EC is disclosed in, for example, Patent Document 1.

  For example, an electrocardiogram-synchronized helical scan is generally performed for examining a heart or the like that is moving such as a heartbeat. In this ECG-synchronous helical scan, X-rays are scanned with respect to the heart region to collect projection data, and in parallel with this scan, an ECG synchronization signal (trigger signal, R wave signal) or ECG waveform signal (ECG signal) is collected. After the projection data is collected, projection data synchronized with the heartbeat phase is collected using an electrocardiogram waveform signal and the like, and the projection data is reconstructed, for example, segment reconstruction is performed to obtain an image.

  This segment reconstruction is composed of a plurality of projection data sets (referred to as a plurality of segments). The plurality of segment sets respectively correspond to a plurality of heartbeat cycles. The plurality of segment sets are collections of projection data collected within a specific period each having a predetermined time width centered on a specific heartbeat phase. That is, the segment reconstruction is performed by collecting projection data of a plurality of beats, that is, different regions of the subject. For example, FIG. 11 shows three segments A, B, and C collected within a predetermined period centered on a heartbeat phase of 65% from, for example, three heartbeat cycles. The segment reconstruction is performed by collecting projection data of these segments A, B, and C. Technologies relating to the electrocardiogram-synchronized helical scan are disclosed in Patent Documents 2 and 3, for example.

However, real EC cannot be used in the ECG-synchronized helical scan at the time of cardiac region imaging. This is because, in the segment configuration, reconstruction is performed by collecting projection data of different regions of the subject. On the other hand, since the real EC automatically calculates the tube current value flowing through the X-ray tube with respect to the image SD designated from the CT value of the scanogram, different tube current values are calculated in different regions of the subject. It will be. For this reason, if the tube current values are different in different regions of the subject, the image quality is affected. Therefore, in the electrocardiogram-synchronized helical scan at the time of cardiac region imaging, the setting of the tube current value flowing through the X-ray tube is left to the experience and judgment of the laboratory technician.
In general, in imaging of the heart region, image quality is often given priority. When setting a tube current value by an examination engineer, a tube current value higher than an appropriate tube current value may be set, and in this case, excessive X-ray exposure occurs. On the other hand, when the tube current value is too low, the image quality is deteriorated.
It is conceivable to set the tube current value by calculating the tube current using the real EC with the ECG-synchronized helical scan mode turned off. The real EC acquires a scanogram by moving the couch at a bed speed in a normal helical scan, and automatically calculates a tube current flowing through the X-ray tube with respect to an image SD designated from the CT value of the scanogram.

However, in the ECG-synchronized helical scan, imaging is performed at a bed speed slower than the bed speed (HP) used in the normal helical scan. For this reason, the tube current value is not obtained from the bed speed in the ECG-synchronized helical scan, but is obtained from the bed speed used in the normal helical scan, and a high tube current value is set. An optimal tube current value cannot be set for an ECG-synchronized helical scan.
JP 2006-55635 A JP-A-2005-230426 JP 2007-117719 A

  An object of the present invention is to provide an ECG-synchronized scan capable of setting an appropriate tube current value that maintains the image quality and does not cause excessive X-ray exposure, regardless of the experience and judgment of an examination engineer in the ECG-synchronized helical scan. It is to provide a method and an X-ray computed tomography apparatus.

  The electrocardiogram synchronous scanning method according to claim 1, wherein an X-ray tube that exposes X-rays to a subject, an X-ray detector that detects the X-rays transmitted through the subject and generates projection data, In the electrocardiographic synchronous scanning method using an X-ray computed tomography apparatus for acquiring tomographic image data of the subject, a scanogram of the subject is acquired by the X-ray computed tomography apparatus, and the scanogram A standard deviation of CT value variation is set for the image, a change in the tube current value flowing through the X-ray tube is obtained based on the standard deviation, and a predetermined tube current value is set from the change in the tube current value. The X-ray tube is rotated while the X-ray tube is rotated, the X-ray tube is rotated to expose the X-ray to the subject, and the X-ray transmitted through the subject is converted into the X-ray. Detect by detector and collect projection data

  An ECG-gated scanning method according to claim 2, wherein an X-ray tube that exposes X-rays to the subject, an X-ray detector that detects the X-rays transmitted through the subject and generates projection data, In the electrocardiographic synchronous scanning method using an X-ray computed tomography apparatus for acquiring tomographic image data of the subject, a scanogram of the subject is acquired by the X-ray computed tomography apparatus, and the scanogram A standard deviation of CT value variation is set for the image, and a change in the value of the tube current flowing in the X-ray tube is obtained based on the standard deviation according to the imaging conditions by the electrocardiogram synchronous scan. Determining the position for determining the tube current of the ECG-synchronized scan, and setting the tube current value flowing in the X-ray tube according to the position for determining the tube current of the ECG-synchronized scan from the change in the tube current value; This setting With the tube current having a constant tube current value supplied to the X-ray tube, the X-ray tube is rotated to expose the X-ray to the subject, and the X-ray transmitted through the subject is The projection data is collected by detecting with an X-ray detector.

  The ECG-gated scanning method according to claim 6, wherein the X-ray tube is rotated to expose the X-rays to the subject, and the moving speed of the bed on which the subject is placed is moved while being constant or variable. The X-ray transmitted through the subject is detected by an X-ray detector to generate projection data, and the projection data collected according to a specific heartbeat phase of the subject is reconstructed to generate a tomographic image of the subject In an electrocardiographic scanning method using an X-ray computed tomography apparatus for acquiring image data, a scano image of the subject is acquired by the X-ray computer tomography apparatus, and a moving speed of the bed based on the scano image A normal helical scan region in which the moving speed of the bed is constant and an ECG-synchronous helical scan region in which the moving speed of the bed is constant are set, and the CT value varies with respect to the scanogram. A standard deviation is set, and a change in the tube current value for each rotation of the X-ray tube is obtained for the normal helical scan region according to the imaging conditions of the normal helical scan, and the change in the tube current value is set. Then, a change in the tube current value for each rotation of the X-ray tube is obtained for the region of the ECG-synchronized helical scan according to the imaging conditions of the normal helical scan, and a predetermined tube is determined from the change in the tube current value. A current value is set, and the X-ray tube is rotated by rotating the X-ray tube in a state where the tube current changing to the set tube current value is supplied to the normal helical scan region. The X-ray that is exposed to the subject, the X-ray transmitted through the subject is detected by an X-ray detector, the projection data is collected, and the predetermined tube current value that is constant with respect to the region of the ECG-synchronized helical scan The tube current of X While supplying to the tube, said X-ray tube is rotated to exposure to X-rays to the subject, the X-rays transmitted through the subject is detected by the X-ray detector for collecting the projection data.

  The X-ray computed tomography apparatus according to claim 7, wherein an X-ray tube that exposes X-rays to a subject, and an X-ray detector that generates projection data by detecting the X-rays transmitted through the subject And a heart rate measuring device for measuring a heart rate of the subject, and the subject based on the projection data generated by the X-ray detector when the subject is exposed to the X-ray from the X-ray tube. A scanogram acquisition unit that acquires a scanogram of a specimen, a standard deviation setting unit that sets a standard deviation of CT value variation with respect to the scanogram, and a tube current value that flows through the X-ray tube based on the standard deviation A tube current value setting unit that sets a predetermined tube current value from the change in the tube current value, and the X-ray tube in a state where the predetermined maximum tube current value is supplied to the X-ray tube. Rotate the tube to expose the X-rays to the subject; An X-ray detector that detects the X-rays that have passed through the subject and collects projection data thereof, and a reconstructor that reconstructs the projection data and obtains tomographic image data of the subject. A component.

  9. The X-ray computed tomography apparatus according to claim 8, wherein an X-ray tube that exposes the X-ray to the subject, and an X-ray detector that generates projection data by detecting the X-ray transmitted through the subject. And a heart rate measuring device for measuring a heart rate of the subject, and the subject based on the projection data generated by the X-ray detector when the subject is exposed to the X-ray from the X-ray tube. A scanogram acquisition unit that acquires a scanogram of a specimen, a standard deviation setting unit that sets a standard deviation of CT value variation with respect to the scanogram, and a tube current value that flows through the X-ray tube based on the standard deviation A tube current calculation unit for obtaining a change in the scan, a scan position determination unit for determining a position for performing an electrocardiogram synchronous scan on the scanogram, and a tube current flowing through the X-ray tube according to the position for performing the electrocardiogram synchronous scan The value of the tube current value A tube current value setting unit to be set from the time of the conversion, and in a state where the tube current of the set constant tube current value is supplied to the X-ray tube, the X-ray tube is rotated and the X-ray is An electrocardiogram-gated scanning unit that detects the X-rays that have been exposed to the subject and transmitted through the subject by the X-ray detector and collects projection data thereof; and the tomogram of the subject by reconstructing the projection data And a reconstruction unit that acquires data.

  An X-ray computed tomography apparatus according to claim 12, wherein an X-ray tube that exposes X-rays to a subject, and an X-ray detector that generates projection data by detecting the X-rays transmitted through the subject And a heart rate measuring device for measuring a heart rate of the subject, and the subject based on the projection data generated by the X-ray detector when the subject is exposed to the X-ray from the X-ray tube. A scano image acquisition unit for acquiring a scanogram of a specimen, a normal helical scan region in which the moving speed of the bed is constant based on the scano image, and an electrocardiographic synchronization helical scan region in which the moving speed of the bed is variable A scan area setting unit for setting the standard deviation setting unit for setting a standard deviation of CT value variation for the scanogram, and the normal helical scan for the normal helical scan area. A change in the tube current value for each rotation of the X-ray tube according to the imaging condition of the X-ray tube, and a first tube current setting unit for setting the change in the tube current value; A second tube for obtaining a change in the tube current value for each rotation of the X-ray tube in accordance with the normal helical scan imaging condition for the region and setting a predetermined tube current value from the change in the tube current value In a state where the tube current that changes to the set tube current value with respect to the normal helical scan region is supplied to the X-ray tube, the X-ray tube is rotated to rotate the X-ray tube. A first projection data acquisition unit that exposes the specimen, detects the X-rays transmitted through the subject by an X-ray detector and collects projection data thereof, and is constant with respect to the region of the ECG-synchronized helical scan The tube current of the predetermined tube current value to the X-ray tube A second projection in which the X-ray tube is rotated to expose the X-ray to the subject, the X-ray transmitted through the subject is detected by an X-ray detector, and projection data is collected. A data acquisition unit; and a reconstruction unit that reconstructs the projection data collected by the first or second data collection unit to obtain tomographic image data of the subject.

  According to the present invention, an ECG-synchronous scan that can maintain an image quality and can set an appropriate tube current value that does not result in excessive X-ray exposure, regardless of the experience and judgment of an examination engineer in an ECG-synchronous helical scan. A method and an X-ray computed tomography apparatus can be provided.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a block diagram of an X-ray computed tomography apparatus. This X-ray computed tomography apparatus includes a scanning unit 1 for collecting projection data relating to a subject (patient) P such as a human body, a bed device 2 for placing the subject P, the scanning unit 1 and the bed device 2. And a console 3 that performs reconstruction processing based on data collected by the scanning unit 1 and image display.

  The scanning unit 1 includes an X-ray tube 4 and a two-dimensional X-ray detector 5. The X-ray tube 4 and the two-dimensional X-ray detector 5 are mounted on a ring-shaped rotating frame 6 in a state of being opposed to each other. A rotary drive device 7 is connected to the rotary frame 6. The rotation driving device 7 rotates in a state in which the X-ray tube 4 and the two-dimensional X-ray detector 5 are disposed to face each other by rotating the rotating frame 6. Thereby, the X-ray tube 4 and the two-dimensional X-ray detector 5 rotate around the subject P. The rotation axis of the rotating frame 6 is defined as the Z axis. In the rotary seat system centered on the Z axis, an axis orthogonal to the Z axis connecting the focal point of the X-ray tube 4 to the detection surface center of the two-dimensional X-ray detector 5 is defined as the X axis. The Y axis is perpendicular to both the Z axis and the X axis.

A high pressure generator 8 is connected to the X-ray tube 4. The high voltage generator 8 applies a high voltage to the X-ray tube 4. Specifically, a high pressure generator 8 is connected between the cathode and anode of the X-ray tube 4. Thus, a tube voltage is applied from the high voltage generator 8 between the cathode and anode of the X-ray tube 4, and a filament current (tube current) is supplied from the high voltage generator 8 to the filament of the X-ray tube 4. X-rays are generated from the anode target of the X-ray tube 4 by applying the tube voltage and supplying the filament current. X-rays emitted from the X-ray tube 4 pass through the collimator 9, pass through the specimen P, and enter the two-dimensional X-ray detector 5.
The collimator 9 is provided on the X-ray tube 4 side between the X-ray tube 4 and the two-dimensional X-ray detector 5. The collimator 9 adjusts the size of the aperture of the collimator 9 by the aperture driving device 10. Actually, the collimator 9 is attached to the X-ray emission window of the X-ray tube 4. The collimator 9 trims X-rays generated at the focal point of the X-ray tube 4 and emitted from the X-ray emission window to an arbitrary size at an arbitrary position.

  The two-dimensional X-ray detector 5 detects X-rays that have passed through the subject P. The two-dimensional X-ray detector 5 may be, for example, a multi-slice type (multi-row type) or a single-slice type (single-row type), but here, a multi-slice detector having a larger exposure reduction effect than the X-ray modulation function. Will be described. The two-dimensional X-ray detector 5 is provided with a plurality of X-ray detection elements that detect X-rays in the channel direction (approximate to the Y-axis direction) and the slice direction (z-axis direction) of the subject P, respectively. For example, about 600 to 1000 X-ray detection elements are arranged in the channel direction, and 24 to 256 columns are arranged in the slice direction, for example. Here, the two-dimensional X-ray detector 5 includes, for example, a plurality of X-ray detection elements arranged in parallel in the channel direction, for example, in a row of 64 rows in the slice direction and a square light receiving surface of 0.5 mm × 0.5 mm, for example. The formed multi-row detector is configured. The plurality of X-ray detection elements include, for example, a scintillator and a photodiode photochip. The two-dimensional X-ray detector 5 includes a multi-slice detector in which X-ray detectors of uniform size are arranged in the slice direction, and a multi-slice type of non-uniform pitch in which a plurality of X-ray detectors having different sizes are arranged in the slice direction. Any detector is applicable.

The two-dimensional X-ray detector 5 is connected to a data acquisition unit (DAS: Data Acquisition System) 11. X-ray detection signals output from the two-dimensional X-ray detector 5 for each channel are collected by the data collection unit 11. The data collection unit 11 converts the X-ray detection signal output for each channel from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data.
The couch device 2 is provided with a top plate 12. The top plate 12 is moved in the slice direction (Z-axis direction) by the bed driving device 13.

  The scan control unit 14 controls the rotation drive unit 7, the high voltage generation unit 8, the aperture drive unit 10, the data collection unit 11, and the bed drive unit 13, and the X-ray tube 4 and the two-dimensional X-ray detector. 5 is rotated at a constant rotational speed while being opposed to each other, and in this state, X-rays emitted from the X-ray tube 4 and transmitted through the subject P are detected by the two-dimensional X-ray detector 5. Projection data is collected, and the top 12 is continuously moved in the slice direction (Z-axis direction) in synchronization with the rotation of the X-ray tube 4 and the two-dimensional X-ray detector 5. As a result, a so-called helical scan in which the X-ray tube 4 is moved in a spiral relative to the subject P and projection data is collected at a plurality of positions on the spiral trajectory can be realized.

In this embodiment, as an example, a case where projection data obtained by multi-helical scanning, which is simultaneous acquisition of multi-row detectors, is described. However, the present invention is not limited thereto, and the top plate 13 is stationary. Dynamic scan that continuously collects projection data, collects projection data for one rotation while the top 13 is stationary at a certain position, then moves and stops the top 13 and then 1 at the next position The present invention can be applied to a conventional scan that repeats the operation of collecting rotation projection data.
The rotating frame 6 has an opening at the center. During scanning, the subject P placed on the top 12 of the bed apparatus 2 is inserted into the opening.

  An electrocardiograph 15 as a heartbeat measuring device is provided. The electrocardiograph 15 is for detecting an electrocardiogram signal corresponding to the heartbeat of the subject P from an electrode attached to the subject P, and detects a weak current generated from the heart of the subject P. The time change of the detected current is output as electrocardiogram information. However, the electrocardiogram information output from the electrocardiograph 15 includes information on P waves, Q waves, R waves, S waves, and T waves. Of this electrocardiogram information, for example, the heart rate is obtained based on the R wave.

  The console 3 causes the scan unit 1 to perform an ECG-synchronized helical scan based on a command for acquiring a scano image and the electrocardiogram information output from the electrocardiograph 15. The acquired projection data is reconstructed to acquire an image of the subject P. The console 3 has a main control unit 20 composed of a CPU or the like, and a projection data storage unit 21, an image storage unit 22, an electrocardiogram information storage unit 23, a display device 24, and the like for the main control unit 20. The operation unit 25 is connected. Further, in response to a command issued from the main control unit 20, a preprocessing unit 26, a reconstruction unit 27, an image processing unit 28, a scano image acquisition unit 29, a standard deviation (SD) setting unit 30, and a maximum tube current setting. The unit 31 and the electrocardiogram synchronization scanning unit 32 operate.

The preprocessing unit 26 performs correction processing such as offset correction, reference correction, and sensitivity correction on the projection data output from the data collection unit 11. The projection data output from the preprocessing unit 26 is stored in the projection data storage unit 21.
On the other hand, the electrocardiogram information storage unit 23 stores electrocardiogram information output from the electrocardiograph 15.
The projection data is associated with the view representing the rotation angle of the X-ray tube 4 at the time of data collection, each code representing the channel number, the column number, and the like, and is associated with the electrocardiogram information output from the electrocardiograph 15, that is, It is synchronized and stored in the projection data storage unit 21.

The reconstruction unit 27 performs electrocardiographic synchronization reconstruction based on the electrocardiogram information stored in the electrocardiogram information storage unit 23 and the projection data stored in the projection data storage unit 21. The reconstruction unit 27 includes, for example, a half reconstruction function and a segment reconstruction function as the electrocardiogram synchronization reconstruction. In the half reconstruction, the X-ray tube 4 requires a projection data group that covers a range of 180 degrees + α (α: fan-shaped X-ray fan angle). In the segment reconstruction method, a projection data group is composed of a plurality of projection data sets, that is, a plurality of segments. The plurality of segments respectively correspond to a plurality of heartbeat cycles. Each of the plurality of segments is a set of projection data collected within a specific period having a predetermined time width centered on a specific heartbeat phase (reconstruction center phase). For example, FIG. 11 shows three segments A, B, and C collected within a predetermined period centered on a heartbeat phase of 65% from, for example, three heartbeat cycles. In the segment reconstruction, the projection data of these segments A, B, and C are collected and reconstructed to obtain a CT image of the subject P, for example, three-dimensional (3D) image data or 3D image data of a moving image, that is, 4D image data. To do. The 3D image data and 4D image data acquired by the reconstruction by the reconstruction unit 27 are stored in the image storage unit 22.
The image processing unit 28 generates, for example, 3D image data stored in the image storage unit 22 from the 3D image data of 3 orientation sections such as axial, coronal, sagittal, etc. by MPR, and generates MIP images from the 3D image data. The image processing is performed and displayed on the display device 24.

  Before acquiring a CT image of the subject P, the scanogram acquisition unit 29 acquires a two-dimensional scano image of the subject P for determining the scan start position and imaging conditions when acquiring the CT image. To do. In this scanogram of the subject P, the position of the X-ray tube 4 is fixed at a predetermined rotation angle, and the top 12 of the bed apparatus 2 is moved in the slice direction (Z direction). At this time, the X-ray tube 4 exposes X-rays to the subject P. The two-dimensional X-ray detector 5 receives X-rays that have passed through the subject P, and outputs an X-ray detection signal corresponding to the amount of received X-rays for each light receiving element. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. The projection data is stored in the projection data storage unit 21. Accordingly, the scanogram acquisition unit 29 reads the projection data stored in the projection data storage unit 21 and acquires a two-dimensional scano image of the subject P from the projection data.

  The SD setting unit 30 sets a standard deviation (SD value) of CT value variation for the scanogram acquired by the scanano image acquisition unit 29. For example, the SD setting unit 30 sets the SD value of CT value variation in the electrocardiogram synchronous imaging region set for the subject P. The SD setting unit 30 can change and set the SD value again after obtaining the change in the tube current value flowing through the X-ray tube 4 based on the SD value. The electrocardiogram synchronous imaging region is set by operating the operation unit 25 by an operator, for example.

The maximum tube current setting unit 31 automatically calculates and obtains a change in the tube current value flowing through the X-ray tube 4 based on the SD value set by the SD setting unit 30, and determines a predetermined value from the change in the tube current value. The tube current value, here, the maximum tube current value is set. FIG. 2 shows an example of a change in the tube current value I flowing through the X-ray tube 4 obtained by calculation based on the SD value. In the subject P, an area E for performing electrocardiogram synchronous imaging is set.
Specifically, the maximum tube current value setting unit is configured to capture the CT image of the subject P, for example, the rotational speed at which the X-ray tube 4 and the two-dimensional X-ray detector 5 are rotated, and the bed apparatus 2 on which the subject P is placed. Tube current value I for each rotation of the X-ray tube 4 in the electrocardiogram synchronous imaging region E according to the moving speed in the slice direction, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, etc. Is calculated, the maximum tube current value Im is determined from the change in the tube current value I, and the maximum tube current value Im is set. When the SD value is changed and set again by the SD setting unit 30, the maximum tube current value setting unit 31 again changes the tube current value I flowing through the X-ray tube 4 based on the changed and set SD value. Then, the maximum tube current value Im is reset from the change in the tube current value I.

The electrocardiogram synchronous scanning unit 32 receives the maximum tube current value Im set by the maximum tube current value setting unit 31, sets the maximum tube current value Im in the scan control unit 14, and issues a scan command to the scan control unit 14 to output the rotation driving device 7. The X-ray tube in a state where the high-voltage generator 8, the aperture driving device 10, the data collecting unit 11, and the bed driving device 13 are controlled and a constant maximum tube current value Im is supplied to the X-ray tube 4. 4 is rotated to expose X-rays to the subject P, and X-rays transmitted through the subject P are detected by the two-dimensional X-ray detector 5 to generate and collect projection data.
The operation unit 25 includes a pointing device such as a mouse, a keyboard, and the like.

Next, the operation of the ECG synchronized imaging by the apparatus configured as described above will be described according to the ECG synchronized imaging operation flowchart shown in FIG.
In step # 1, the scanogram acquisition unit 29 determines the start position of the scan, the imaging conditions for acquiring the CT image, etc. before acquiring the CT image of the subject P. Get the scano image. That is, the scanogram acquisition unit 29 fixes the position of the X-ray tube 4 to a predetermined rotation angle, and sends a command for moving the top 12 of the bed apparatus 2 in the slice direction (Z direction) through the scan control unit 14. 2 and a command to radiate X-rays from the X-ray tube 4 is sent to the high pressure generator 8 through the scan controller 14. Thereby, the X-ray tube 4 is fixed to a predetermined rotation angle, and moves the bed apparatus 2 and the top plate 12 in the slice direction (Z direction). In this state, the X-ray tube 4 exposes X-rays to the subject P. This X-ray passes through the subject P and enters the two-dimensional X-ray detector 5. The two-dimensional X-ray detector 5 receives X-rays transmitted through the subject P and outputs an X-ray detection signal corresponding to the amount of received X-rays for each light receiving element.

The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21.
The scanogram acquisition unit 29 reads the projection data stored in the projection data storage unit 21, and acquires a two-dimensional scano image of the subject P from the projection data.
Next, the electrocardiogram synchronous imaging region E is input when the operator or the like operates the operation unit 25, for example. In step # 2, the main control unit 20 sets the electrocardiogram synchronous imaging region E input from the operation unit 25 on the two-dimensional scano image of the subject P.

Next, in step # 3, the SD setting unit 30 sets the SD value of the CT value variation in the electrocardiogram synchronous imaging region E set for the subject P, for example.
Next, in step # 4, the maximum tube current value setting unit mounts the CT image capturing condition of the subject P, for example, the rotational speed for rotating the X-ray tube 4 and the two-dimensional X-ray detector 5, and the subject P. Depending on the moving speed in the slice direction of the bed apparatus 2 to be placed, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, etc., for example, as shown in FIG. A change in the tube current value I for each rotation of the X-ray tube 4 is automatically calculated and obtained.

In step # 5, the maximum tube current value setting unit displays the change in the tube current value I for each rotation of the X-ray tube 4 automatically calculated and displayed on the display device 24. Here, there is a possibility that the amount of X-ray exposure to the subject P becomes large because the maximum tube current value Im of the change in the tube current value I for each rotation of the X-ray tube 4 in the electrocardiogram synchronous imaging region E is too large. In some cases, for example, an operation of resetting the SD value is performed on the operation unit 25 by an operator or the like. In response to the operation of resetting the SD value from the operation unit 25, the main control unit 20 returns to step # 3 again and issues a command to reset the SD value to the SD setting unit 30.
If the maximum tube current value Im of the change in the tube current value I for each rotation of the X-ray tube 4 in the electrocardiogram synchronous imaging region E is optimum, the maximum tube current value setting unit determines in step # 6 that the tube current value The maximum tube current value Im is obtained from the change in I, and this maximum tube current value Im is set.

  Next, in step # 7, the electrocardiogram synchronous scanning unit 32 receives the maximum tube current value Im set by the maximum tube current value setting unit 31, sets it in the scan control unit 14, and ECG synchronous imaging in which a scan command is issued to control the rotation drive device 7, the high voltage generation unit 8, the aperture drive device 10, the data collection unit 11, and the bed drive device 13 to collect projection data. Let it be done.

  That is, a high voltage is applied to the X-ray tube 4 from the high voltage generator 8 and a tube current having a constant maximum tube current value Im is supplied. Thereby, the X-ray tube 4 emits X-rays. In this state, the X-ray tube 4 and the two-dimensional X-ray detector 5 rotate at a constant rotational speed in a state of being opposed to each other. In synchronization with the rotation of the X-ray tube 4 and the two-dimensional X-ray detector 5, the top 12 of the bed apparatus 2 continuously moves in the slice direction (Z-axis direction) with the subject P placed thereon. To do. As a result, a so-called helical scan is performed in which the X-ray tube 4 is moved in a spiral relative to the subject P and projection data is collected at a plurality of positions on the spiral trajectory. During this helical scan, the X-rays emitted from the X-ray tube 4 pass through the subject P and enter the two-dimensional X-ray detector 5.

  The two-dimensional X-ray detector 5 receives X-rays transmitted through the subject P and outputs an X-ray detection signal corresponding to the amount of received X-rays for each light receiving element. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21.

  At the same time, the electrocardiograph 15 detects an electrocardiogram signal corresponding to the heartbeat of the subject P from the electrode attached to the subject P, that is, a weak current generated from the heart of the subject P, and the time of the detected current The change is output as ECG information. The electrocardiogram information output from the electrocardiograph 15 is stored in the electrocardiogram information storage unit 23. At this time, the projection data is associated with a view representing the rotation angle of the X-ray tube 4 at the time of data collection, each code representing a channel number, a column number, etc., and associated with the electrocardiogram information output from the electrocardiograph 15, It is synchronized and stored in the projection data storage unit 21.

The reconstruction unit 27 performs electrocardiographic synchronization reconstruction based on the electrocardiogram information stored in the electrocardiogram information storage unit 23 and the projection data stored in the projection data storage unit 21. The reconstruction unit 27 performs, for example, half reconstruction or segment reconstruction as the electrocardiogram synchronization reconstruction. Of these, half reconstruction requires a projection data group in which the X-ray tube 4 covers a range of 180 degrees + α. In the segment reconstruction, a projection data group is constituted by a plurality of projection data sets, that is, a plurality of segments. The plurality of segments respectively correspond to a plurality of heartbeat cycles. Each of the plurality of segments is a set of projection data collected within a specific period having a predetermined time width centered on a specific heartbeat phase (reconstruction center phase). For example, FIG. 11 shows three segments A, B, and C collected within a predetermined period centered on a heartbeat phase of 65% from, for example, three heartbeat cycles. In the segment reconstruction, the projection data of these segments A, B, and C are collected and reconstructed to obtain a CT image of the subject P, for example, three-dimensional (3D) image data or 3D image data of a moving image, that is, 4D image data. To do. The 3D image data and 4D image data acquired by the reconstruction by the reconstruction unit 27 are stored in the image storage unit 22.
The image processing unit 28 generates, for example, 3D image data stored in the image storage unit 22 from the 3D image data of 3 orientation sections such as axial, coronal, sagittal, etc. by MPR, and generates MIP images from the 3D image data. The image processing is performed and displayed on the display device 24.

  When resetting another ECG-synchronized imaging region E for the subject P, the main control unit 20 returns to step # 2, and again selects another ECG-synchronized imaging region E input from the operation unit 25. It is set on a two-dimensional scano image of the subject P.

  As described above, according to the first embodiment, a scanogram of the subject P is acquired, an SD value of a CT value is set for the scanogram, and the X-ray tube 4 is set based on the SD value. The change in the flowing tube current value I is obtained, the maximum tube current value Im is set from the change in the tube current value I, and the X-ray tube 4 is rotated while the maximum tube current value Im is supplied to the X-ray tube 4. The X-rays are exposed to the subject P, and the X-rays transmitted through the subject P are detected by the two-dimensional X-ray detector 5 to generate and collect projection data.

  As a result, the image quality of the CT image can be maintained and the excessive X-ray exposure can be maintained without depending on the experience and judgment of the laboratory technician in the ECG-synchronized helical scan and without setting a high tube current value by the laboratory technician. It is possible to set an appropriate tube current value that does not become, that is, a constant maximum tube current value Im. That is, since the real EC automatically calculates the tube current value I flowing through the X-ray tube 4 with respect to the image SD designated from the CT value of the scanogram, different tube current values I in different regions of the subject P are obtained. However, in the present apparatus, since the constant maximum tube current value Im can be set, the image quality of the CT image is not affected. In general, since image quality is often given priority in imaging of the heart region, this apparatus is effective for electrocardiographic synchronization imaging.

Next, a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
FIG. 4 shows a configuration diagram of an X-ray computed tomography apparatus. In the console 3, a tube current calculation unit 40, a scan position determination unit 41, and a tube current value setting unit 42 are operated by a command issued from the main control unit 20.

  The tube current calculation unit 40 is based on the SD value set by the SD setting unit 30. The imaging conditions by the electrocardiogram synchronous scan, for example, the rotational speed for rotating the X-ray tube 4 and the two-dimensional X-ray detector 5, and the subject P 5 flows in the X-ray tube 4 as shown in FIG. 5, for example, according to the moving speed in the slice direction of the bed apparatus 2 on which the patient is placed, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, and the like. The change of the tube current value I is automatically calculated and obtained.

For example, as shown in FIG. 5, the scan position determination unit 41 determines a position H at which an electrocardiographic synchronization scan is performed on the scanogram acquired by the scanogram acquisition unit 29.
For example, as shown in FIG. 5, the tube current value setting unit 42 sets the tube current value If flowing in the X-ray tube 4 according to the position H at which the electrocardiogram synchronous scan is performed from the change in the tube current value I.

  The electrocardiogram synchronous scanning unit 32 receives the tube current value If flowing in the X-ray tube 4 corresponding to the position H where the electrocardiographic synchronous scan set by the tube current value setting unit 42 is performed, and sets the tube current value If in the scan control unit 14. In addition, a scan command is issued to the scan control unit 14 to control the rotation drive device 7, the high voltage generation unit 8, the aperture drive device 10, the data collection unit 11, and the bed drive device 13, and a constant tube current value If. With the X-ray tube 4 supplied, the X-ray tube 4 is rotated to expose the X-rays to the subject P, and the X-rays transmitted through the subject P are detected by the two-dimensional X-ray detector 5. Projection data is generated, and projection data is collected from the heartbeat of the subject P measured by the electrocardiograph 15 according to a specific heartbeat phase.

Next, the operation of the ECG synchronized imaging by the apparatus configured as described above will be described according to the ECG synchronized imaging operation flowchart shown in FIG.
In step # 1, the scanogram acquisition unit 29 determines the scan start position and the imaging conditions for acquiring the CT image before acquiring the CT image of the subject P in the same manner as described above. A two-dimensional scano image of P is acquired. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21. The scanogram acquisition unit 29 reads the projection data stored in the projection data storage unit 21, and acquires a two-dimensional scano image of the subject P from the projection data.

Next, the electrocardiogram synchronous imaging region E is input when the operator or the like operates the operation unit 25, for example. The main control unit 20 sets the electrocardiogram synchronous imaging region E input from the operation unit 25 on the two-dimensional scan image of the subject P.
Next, in step # 3, the SD setting unit 30 sets the SD value of the CT value variation in the electrocardiogram synchronous imaging region E set for the subject P, for example.

  Next, in step # 10, the tube current calculation unit 40 determines the imaging conditions by the electrocardiogram synchronous scan based on the SD value set by the SD setting unit 30, for example, the X-ray tube 4 and the two-dimensional X-ray detector 5. FIG. 5 shows, for example, the rotation speed to rotate, the moving speed in the slice direction of the bed apparatus 2 on which the subject P is placed, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, and the like. Such a change in the tube current value I flowing in the X-ray tube 4 is automatically calculated and obtained.

  Next, in step # 5, the tube current calculation unit 40 displays the change in the tube current value I for each rotation of the X-ray tube 4 automatically calculated and displayed on the display device 24. Here, the tube current value I corresponding to the position H at which the ECG synchronous scan is performed is too large due to the change in the tube current value I for each rotation of the X-ray tube 4 in the ECG synchronous imaging region E. When there is a possibility that the amount of X-ray exposure to the specimen P is likely to increase, for example, an operation of resetting the SD value is performed on the operation unit 25 by an operator or the like. In response to the operation of resetting the SD value from the operation unit 25, the main control unit 20 returns to step # 3 again and issues a command to reset the SD value to the SD setting unit 30.

Next, in step # 11, the scan position determination unit 41 determines a position H for determining the tube current of the electrocardiographic scan on the scano image acquired by the scano image acquisition unit 29, for example, as shown in FIG. decide.
Next, in step # 12, the tube current value setting unit 42, for example, as shown in FIG. 5, the tube current value If that flows through the X-ray tube 4 according to the position H for determining the tube current of the ECG synchronous scan. Is set from the change in the tube current value I.

  Next, in step # 7, the electrocardiogram synchronous scanning unit 32 receives the tube current value If set by the tube current value setting unit 42, sets the tube current value If in the scan control unit 14, and scans the scan control unit 14. A command is issued to control the rotation driving device 7, the high voltage generation unit 8, the aperture driving device 10, the data collection unit 11, and the bed driving device 13 to perform electrocardiographic synchronization imaging.

  That is, a high voltage is applied to the X-ray tube 4 from the high voltage generator 8 and a tube current having a constant tube current value If is supplied. Thereby, the X-ray tube 4 emits X-rays. In this state, the X-ray tube 4 and the two-dimensional X-ray detector 5 rotate at a constant rotational speed in a state of being opposed to each other. In synchronization with the rotation of the X-ray tube 4 and the two-dimensional X-ray detector 5, the top 12 of the bed apparatus 2 continuously moves in the slice direction (Z-axis direction) with the subject P placed thereon. To do. As a result, a so-called helical scan is performed in which the X-ray tube 4 is moved in a spiral relative to the subject P and projection data is collected at a plurality of positions on the spiral trajectory. During this helical scan, the X-rays emitted from the X-ray tube 4 pass through the subject P and enter the two-dimensional X-ray detector 5.

  The two-dimensional X-ray detector 5 receives X-rays transmitted through the subject P and outputs an X-ray detection signal corresponding to the amount of received X-rays for each light receiving element. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21.

  At the same time, the electrocardiograph 15 detects a weak current generated from the heart of the subject P, and outputs a time change of the detected current as electrocardiogram information. The electrocardiogram information output from the electrocardiograph 15 is stored in the electrocardiogram information storage unit 23. At this time, the projection data is associated with a view representing the rotation angle of the X-ray tube 4 at the time of data collection, each code representing a channel number, a column number, etc., and associated with the electrocardiogram information output from the electrocardiograph 15, It is synchronized and stored in the projection data storage unit 21.

Similarly to the above, the reconstruction unit 27 performs electrocardiographic synchronization reconstruction based on the electrocardiogram information stored in the electrocardiogram information storage unit 23 and the projection data stored in the projection data storage unit 21. The reconstruction unit 27 performs, for example, half reconstruction or segment reconstruction as the electrocardiogram synchronization reconstruction.
The image processing unit 28 generates, for example, 3D image data stored in the image storage unit 22 from the 3D image data of 3 orientation sections such as axial, coronal, sagittal, etc. by MPR, and generates MIP images from the 3D image data. The image processing is performed and displayed on the display device 24.
When resetting another ECG-synchronized imaging region E for the subject P, the main control unit 20 returns to step # 2, and again selects another ECG-synchronized imaging region E input from the operation unit 25. It is set on a two-dimensional scano image of the subject P.

  As described above, according to the second embodiment, a scanogram of the subject P is acquired, an SD value of CT value variation with respect to the scanogram is set, and an electrocardiographic synchronization scan is performed based on the SD value. The change of the tube current value I flowing through the X-ray tube 4 is obtained according to the imaging conditions, the position H for determining the ECG-synchronized scan tube current is determined on the scan image, and the ECG-synchronized scan tube current is determined. The tube current value If flowing in the X-ray tube 4 corresponding to the position H to be set is set, and the X-ray tube 4 is rotated while the tube current of the set tube current value If is supplied to the X-ray tube 4. X-rays are exposed to the subject P, X-rays transmitted through the subject P are detected by the two-dimensional X-ray detector 5 and the projection data is collected. As a result, the image quality of the CT image can be maintained and the excessive X-ray exposure can be maintained without depending on the experience and judgment of the laboratory technician in the ECG-synchronized helical scan and without setting a high tube current value by the laboratory technician. An appropriate constant tube current value If which cannot be set can be set. That is, since the real EC automatically calculates the tube current value I flowing through the X-ray tube 4 with respect to the image SD designated from the CT value of the scanogram, different tube current values I in different regions of the subject P are obtained. However, in this apparatus, since the tube current value If corresponding to the position H for determining the tube current of the ECG-gated scan can be set, the image quality of the CT image is affected. There is nothing. In general, since image quality is often given priority in imaging of the heart region, this apparatus is effective for electrocardiographic synchronization imaging.

Next, a third embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
FIG. 7 shows a configuration diagram of an X-ray computed tomography apparatus. The computed tomography apparatus performs a variable HP helical scan, and reconstructs projection data acquired by the variable HP helical scan to acquire an image of the subject P. The variable HP helical scan is a scan that changes the moving speed of the top plate 12 of the bed apparatus 2 during one helical scan, and is a combination of an electrocardiogram-synchronized helical scan and a normal helical scan.

The console 3 includes a scan region setting unit 50, a first tube current setting unit 51, a second tube current setting unit 52, a first projection data acquisition unit 53, and a command issued from the main control unit 20. The second projection data acquisition unit 54 operates.
The scan region setting unit 50 includes a normal helical scan region in which the moving speed in the slice direction of the tabletop 12 in the bed apparatus 2 is constant based on the scano image acquired by the scanano image acquisition unit 29, and the bed apparatus 2. An ECG-synchronized helical scan region in which the moving speed of the top 12 in the slice direction is variable is set. For example, as shown in FIG. 8, an area for performing ECG-synchronized imaging including the heart in the subject P is set as an area J for ECG-synchronized helical scan, and other areas for imaging such as the abdomen are defined as areas K for normal helical scan. Set to. The moving speed of the couchtop 2 of the couch device 2 in the electrocardiogram synchronous helical scan area J is set slower than the moving speed of the couchtop 2 of the couch apparatus 2 in the normal helical scan area K.

  The first tube current setting unit 51 places normal helical scan imaging conditions on the normal helical scan region K, for example, the rotational speed for rotating the X-ray tube 4 and the two-dimensional X-ray detector 5, and the subject P. Automatically changes the tube current value for each rotation of the X-ray tube 4 according to the moving speed of the couch device 2 in the slice direction, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, etc. The change of the tube current value is set by calculation.

  The second tube current setting unit 52 is configured to scan the ECG-synchronized helical scan region J with respect to the ECG-synchronized helical scan imaging conditions, for example, the rotational speed at which the X-ray tube 4 and the two-dimensional X-ray detector 5 are rotated. The tube current value for each rotation of the X-ray tube 4 according to the moving speed in the slice direction of the bed apparatus 2 on which P is placed, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, and the like The change is automatically calculated, and the maximum tube current value is set from the change in the tube current value.

  The first projection data acquisition unit 53 rotates the X-ray tube 4 and supplies X-rays in a state in which the tube current that changes to the tube current value set for the normal helical scan region K is supplied to the X-ray tube 4. Is exposed to the subject P, X-rays transmitted through the subject P are detected by the two-dimensional X-ray detector 5, the projection data is generated, and the projection data is collected.

  The second projection data acquisition unit 54 rotates the X-ray tube 4 and supplies X-rays while the tube current having the maximum tube current value is supplied to the ECG-synchronized helical scan region J. The two-dimensional X-ray detector 5 detects X-rays that have been exposed to the specimen P and transmitted through the subject P, generates projection data, and collects projection data.

  The reconstruction unit 27 reconstructs the projection data collected by the first projection data acquisition unit 53 and the projection data collected by the second projection data acquisition unit 54 to obtain a CT image of the subject P. get. When the reconstruction unit 27 reconstructs the projection data collected by the second projection data acquisition unit 54 during the ECG-synchronized helical scan, the reconstruction unit 27 performs reconstruction based on the electrocardiogram information stored in the electrocardiogram information storage unit 23. I do. At this time, the reconstruction unit 27 performs, for example, half reconstruction or segment reconstruction as the electrocardiogram synchronization reconstruction.

  The variable HP helical scan unit 55 receives the maximum tube current value Im set by the second tube current setting unit 52 for the electrocardiogram-synchronized helical scan region J, sets the maximum tube current value Im in the scan control unit 14, and the scan control unit An electrocardiogram that issues a scan command to 14 to control the rotation drive device 7, the high voltage generation unit 8, the aperture drive device 10, the data collection unit 11, and the bed drive device 13 and collect projection data. Make synchronized shooting.

  The variable HP helical scan unit 55 receives a change in the tube current value I for each rotation of the X-ray tube 4 set by the first tube current setting unit 51 with respect to the normal helical scan region K, and receives a change in the scan control unit. 14 and issues a scan command to the scan control unit 14 to control the rotation drive unit 7, the high voltage generation unit 8, the aperture drive unit 10, the data collection unit 11, and the bed drive unit 13. Then, electrocardiographic synchronized imaging of collecting projection data is performed.

Next, the operation of the ECG synchronous imaging by the variable HP helical scan by the apparatus configured as described above will be described according to the ECG synchronous imaging flowchart of the variable HP helical scan shown in FIG.
In step # 1, the scanogram acquisition unit 29 determines the scan start position and the imaging conditions for acquiring the CT image before acquiring the CT image of the subject P in the same manner as described above. A two-dimensional scano image of P is acquired. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21. The scanogram acquisition unit 29 reads the projection data stored in the projection data storage unit 21, and acquires a two-dimensional scano image of the subject P from the projection data.

  Next, for example, as shown in FIG. 8, an electrocardiogram-synchronized helical scan region J for performing electrocardiogram-synchronized imaging including the heart in the subject P, and a normal helical scan region K for performing imaging of other abdominal regions, for example, an operator or the like. Is input by operating the operation unit 25. In step # 20, the main control unit 20 sets the electrocardiogram-synchronized helical scan region J and the normal helical scan region K input from the operation unit 25.

Next, in step # 3, the SD setting unit 30 sets the SD value of the CT value variation with respect to the scanogram for each of the ECG-synchronized helical scan region J and the normal helical scan region K, for example.
Next, in step # 21, the first tube current setting unit 51 rotates the imaging conditions of the normal helical scan, for example, the X-ray tube 4 and the two-dimensional X-ray detector 5, with respect to the normal helical scan region K. Depending on the speed, the moving speed in the slice direction of the bed apparatus 2 on which the subject P is placed, the slice thickness of the CT image of the subject P obtained by reconstructing the projection data, etc. A change in the tube current value I for each rotation of the tube 4 is automatically calculated and obtained.

  Next, in step # 22, the second tube current setting unit 52 performs electrocardiogram-synchronized helical scan imaging conditions such as the X-ray tube 4 and the two-dimensional X-ray detector 5 in the ECG-synchronized helical scan region J. FIG. 10 shows, for example, the rotation speed of rotating the bed, the moving speed of the bed apparatus 2 on which the subject P is placed in the slice direction, the slice thickness of the CT image of the subject P acquired by reconstructing the projection data, and the like. The change of the tube current value I for every rotation of the X-ray tube 4 as shown is automatically calculated and obtained.

  The first and second tube current setting units 51 and 52 calculate the change between the tube current value I at the normal helical scan and the tube current value I at the ECG-synchronized helical scan, which are automatically calculated and obtained. It is displayed on the display device 24. Here, there is a risk that the amount of X-ray exposure to the subject P will increase because the maximum tube current value Im of the change in the tube current value I for each rotation of the X-ray tube 4 in the ECG-synchronized helical scan region J is too large. If there is, for example, an operation of resetting the SD value is performed on the operation unit 25 by an operator or the like. In response to the operation of resetting the SD value from the operation unit 25, the main control unit 20 returns to step # 3 again and issues a command to reset the SD value to the SD setting unit 30.

Next, in step # 23, the second tube current setting unit 52 automatically changes the tube current value I for each rotation of the X-ray tube 4 obtained by calculating the ECG-synchronized helical scan region J. The maximum tube current value Im is obtained from the above, and this maximum tube current value Im is set.
Next, in step # 24, the first tube current setting unit 51 determines the change in the tube current value I for each rotation of the X-ray tube 4 obtained by automatically calculating the normal helical scan region K as it is. Set.
The setting of the tube current value I during normal helical scanning by the first tube current setting unit 51 and the setting of the maximum tube current value Im during electrocardiographic synchronous helical scanning by the second tube current setting unit 52 are: First, the maximum tube current value Im at the time of the ECG-synchronized helical scan is set by the second tube current setting unit 52, and then the tube current value I at the time of the normal helical scan by the first tube current setting unit 51 is set. Settings may be made.

  Next, the variable HP helical scan unit 55 receives the maximum tube current value Im set by the second tube current setting unit 52 for the electrocardiogram-synchronized helical scan region J in step # 25 and receives the scan control unit 14. And a scan command is issued to the scan control unit 14 to control the rotation drive device 7, the high voltage generation unit 8, the aperture drive device 10, the data collection unit 11, and the bed drive device 13, In addition, ECG synchronous imaging is performed in which projection data is collected according to a specific heartbeat phase from the heartbeat of the subject P measured by the electrocardiograph 15. That is, a high voltage is applied to the X-ray tube 4 from the high voltage generator 8 and a tube current having a constant maximum tube current value Im is supplied. Thereby, the X-ray tube 4 emits X-rays. In this state, the X-ray tube 4 and the two-dimensional X-ray detector 5 rotate at a constant rotational speed in a state of being opposed to each other. In synchronization with the rotation of the X-ray tube 4 and the two-dimensional X-ray detector 5, the top 12 of the bed apparatus 2 continuously moves in the slice direction (Z-axis direction) with the subject P placed thereon. To do. As a result, a so-called helical scan is performed in which the X-ray tube 4 is moved in a spiral relative to the subject P and projection data is collected at a plurality of positions on the spiral trajectory. During this helical scan, the X-rays emitted from the X-ray tube 4 pass through the subject P and enter the two-dimensional X-ray detector 5.

  The two-dimensional X-ray detector 5 receives X-rays transmitted through the subject P and outputs an X-ray detection signal corresponding to the amount of received X-rays for each light receiving element. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21.

  At the same time, the electrocardiograph 15 detects an electrocardiogram signal corresponding to the heartbeat of the subject P from the electrode attached to the subject P, that is, a weak current generated from the heart of the subject P, and the time of the detected current The change is output as ECG information. The electrocardiogram information output from the electrocardiograph 15 is stored in the electrocardiogram information storage unit 23. At this time, the projection data is associated with a view representing the rotation angle of the X-ray tube 4 at the time of data collection, each code representing a channel number, a column number, etc., and associated with the electrocardiogram information output from the electrocardiograph 15, It is synchronized and stored in the projection data storage unit 21.

Similarly to the above, the reconstruction unit 27 performs electrocardiographic synchronization reconstruction based on the electrocardiogram information stored in the electrocardiogram information storage unit 23 and the projection data stored in the projection data storage unit 21. The reconstruction unit 27 performs, for example, half reconstruction or segment reconstruction as the electrocardiogram synchronization reconstruction.
The image processing unit 28 generates, for example, 3D image data stored in the image storage unit 22 from the 3D image data of 3 orientation sections such as axial, coronal, sagittal, etc. by MPR, and generates MIP images from the 3D image data. The image processing is performed and displayed on the display device 24.
When resetting another electrocardiogram synchronous imaging region E for the subject P, the main control unit 20 returns to step # 20 and is input again from another operation unit 25 input from the operation unit 25. An ECG-synchronized helical scan area J and a normal helical scan area K are set.

  The variable HP helical scan unit 55 receives a change in the tube current value I for each rotation of the X-ray tube 4 set by the first tube current setting unit 51 with respect to the normal helical scan region K, and receives a change in the scan control unit. 14 and issues a scan command to the scan control unit 14 to control the rotation drive unit 7, the high voltage generation unit 8, the aperture drive unit 10, the data collection unit 11, and the bed drive unit 13. Collect projection data.

  That is, a high voltage is applied from the high voltage generator 8 to the X-ray tube 4 and a tube current having a tube current value I that varies depending on the scan position is supplied. Thereby, the X-ray tube 4 emits X-rays. In this state, the X-ray tube 4 and the two-dimensional X-ray detector 5 rotate at a constant rotational speed in a state of being opposed to each other. In synchronization with the rotation of the X-ray tube 4 and the two-dimensional X-ray detector 5, the top 12 of the bed apparatus 2 continuously moves in the slice direction (Z-axis direction) with the subject P placed thereon. To do. Thereby, a helical scan is performed. During this helical scan, the X-rays emitted from the X-ray tube 4 pass through the subject P and enter the two-dimensional X-ray detector 5.

The two-dimensional X-ray detector 5 receives X-rays transmitted through the subject P and outputs an X-ray detection signal corresponding to the amount of received X-rays for each light receiving element. The data collection unit 11 converts each X-ray detection signal for each light receiving element output from the two-dimensional X-ray detector 5 into a voltage signal, amplifies it, converts it into a digital signal, and outputs it as projection data. This projection data is stored in the projection data storage unit 21.
At the same time, the electrocardiograph 15 detects a weak current generated from the heart of the subject P, and outputs a time change of the detected current as electrocardiogram information. The electrocardiogram information output from the electrocardiograph 15 is stored in the electrocardiogram information storage unit 23. At this time, the projection data is associated with a view representing the rotation angle of the X-ray tube 4 at the time of data collection, each code representing a channel number, a column number, etc., and associated with the electrocardiogram information output from the electrocardiograph 15, that is, It is synchronized and stored in the projection data storage unit 21.

Similarly to the above, the reconstruction unit 27 performs electrocardiographic synchronization reconstruction based on the electrocardiogram information stored in the electrocardiogram information storage unit 23 and the projection data stored in the projection data storage unit 21. The reconstruction unit 27 performs, for example, half reconstruction or segment reconstruction as the electrocardiogram synchronization reconstruction.
The image processing unit 28 generates, for example, 3D image data stored in the image storage unit 22 from the 3D image data of 3 orientation sections such as axial, coronal, sagittal, etc. by MPR, and generates MIP images from the 3D image data. The image processing is performed and displayed on the display device 24.

  As described above, according to the third embodiment, a scanogram of the subject P is acquired, the normal helical scan region K and the electrocardiogram synchronization helical scan region J are set, and the SD value for the scanogram is set. For the normal helical scan region K, the change in the tube current value I for each rotation of the X-ray tube 4 is determined according to the imaging conditions, and the change in the tube current value I is set. On the other hand, a constant maximum tube current value Im is set from the change in the tube current value I for each rotation of the X-ray tube 4 according to the imaging conditions, and the tube current value I set for the normal helical scan region K is set to X. In the state supplied to the tube 4, normal helical scan is performed to collect projection data, and the electrocardiogram-synchronized helical in the state where the maximum tube current value Im is supplied to the X-ray tube 4 for the ECG-synchronized helical scan region J Do a scan To collect the shadow data.

  This maintains the image quality of the CT image and does not cause excessive X-ray exposure without depending on the experience and judgment of the laboratory technician in the variable HP helical scan and without being set to a high tube current value by the laboratory technician. An appropriate tube current, that is, a tube current value I for the normal helical scan region K and a maximum tube current value Im for the electrocardiogram-synchronized helical scan region J can be set. In general, since image quality is often given priority in imaging of the heart region, this apparatus is effective for electrocardiographic synchronization imaging.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  In the above embodiment, the scanning imaging conditions, for example, the rotational speed for rotating the X-ray tube 4 and the two-dimensional X-ray detector 5, the moving speed in the slice direction of the bed apparatus 2 on which the subject P is placed, and the projection data are obtained. A change in tube current value I for each rotation of the X-ray tube 4 as shown in FIG. Although the maximum tube current value Im is obtained and set from the change in the tube current value I for each rotation of the X-ray tube 4, the present invention is not limited to this, and the middle of the change in the tube current value I for each rotation of the X-ray tube 4. A value, a median value, or an average value may be obtained, and a tube current of these intermediate value, median value, or average value may be set.

1 is a configuration diagram showing a first embodiment of an X-ray computed tomography apparatus according to the present invention. FIG. The figure which shows an example of the change of the tube electric current value which flows into the X-ray tube calculated | required by calculating based on SD value by the standard deviation (SD) setting part in the same apparatus. The figure which shows the electrocardiogram synchronous imaging | photography flowchart in the same apparatus. The figure which shows the maximum tube current value set by the maximum tube current setting part in the same apparatus. The block diagram which shows 2nd Embodiment of the X-ray computed tomography apparatus which concerns on this invention. The figure which shows the electrocardiogram synchronous imaging | photography flowchart in the same apparatus. The block diagram which shows 3rd Embodiment of the X-ray computed tomography apparatus which concerns on this invention. The figure which shows the electrocardiogram synchronous helical scan area | region which performs the electrocardiogram synchronous imaging including the heart in a subject in the subject, and the area | region which performs a normal helical scan. The electrocardiogram synchronous imaging | photography flowchart of the variable HP helical scan in the same apparatus. The figure which shows the setting of the tube current value at the time of the normal helical scan by the same apparatus, and the setting of the maximum tube current value at the time of an electrocardiogram synchronous helical scan. FIG. 6 is a schematic diagram showing each segment in segment reconstruction in an electrocardiogram-synchronized helical scan during cardiac region imaging.

Explanation of symbols

  P: subject (patient), 1: scanning unit, 2: bed apparatus, 3: console, 4: X-ray tube, 5: two-dimensional X-ray detector, 6: rotating frame, 7: rotating drive device, 8: High pressure generating unit, 9: collimator, 10: aperture driving device, 11: data collecting unit, 12: top plate, 13: bed driving device, 14: scan control unit, 15: electrocardiograph, 20: main control unit, 21 : Projection data storage unit, 22: image storage unit, 23: electrocardiogram information storage unit, 24: display device, 25: operation unit, 26: preprocessing unit, 27: reconstruction unit, 28: image processing unit, 29: Scano image acquisition unit, 30: SD setting unit, 31: Maximum tube current setting unit, 32: Electrocardiogram synchronous scanning unit, 40: Tube current calculation unit, 41: Scan position determination unit, 42: Tube current value setting unit, 50 : Scan area setting unit 51: First tube current setting unit 52: Second tube power Setting unit, 53: first projection data acquisition unit, 54: second projection data acquisition unit, 55: Variable HP helical scan unit.

Claims (14)

An X-ray tube that exposes the X-ray to the subject, and an X-ray detector that detects the X-ray transmitted through the subject and generates projection data, and obtains tomographic image data of the subject In an electrocardiogram synchronous scanning method using an X-ray computed tomography apparatus,
A scanogram of the subject is acquired by the X-ray computed tomography apparatus;
Set the standard deviation of the CT value variation for the scanogram,
Obtain a change in the tube current value flowing in the X-ray tube based on the standard deviation, set a predetermined tube current value from the change in the tube current value,
With the predetermined tube current value being supplied to the X-ray tube, the X-ray tube is rotated to expose the X-ray to the subject, and the X-ray that has passed through the subject is detected by X-ray. Collecting the projection data detected by the instrument,
An ECG synchronous scanning method characterized by the above. An X-ray tube that exposes the X-ray to the subject, and an X-ray detector that detects the X-ray transmitted through the subject and generates projection data, and obtains tomographic image data of the subject In an electrocardiogram synchronous scanning method using an X-ray computed tomography apparatus,
A scanogram of the subject is acquired by the X-ray computed tomography apparatus;
Set the standard deviation of the CT value variation for the scanogram,
Based on the standard deviation, the change in the value of the tube current flowing in the X-ray tube is determined according to the imaging conditions by the ECG synchronous scan,
Determine the position to determine the ECG-synchronized scan tube current on the scanogram,
A tube current value flowing through the X-ray tube according to a position for determining the tube current of the ECG synchronous scan is set from a change in the tube current value,
In a state where the tube current having the set constant tube current value is supplied to the X-ray tube, the X-ray tube is rotated to expose the X-ray to the subject, and the X-ray transmitted through the subject. The line is detected by an X-ray detector and its projection data is collected,
An ECG synchronous scanning method characterized by the above.   3. The ECG-gated scanning method according to claim 1, wherein an ECG-synchronized imaging region is set in the scanogram, and a standard deviation of the CT value variation is set in the ECG-synchronized imaging region. .   The predetermined tube current value is obtained by calculating a change in the tube current value for each rotation of the X-ray tube in the electrocardiogram synchronous imaging region in accordance with imaging conditions of the tomographic image data of the subject. 4. The electrocardiogram synchronous scanning method according to claim 3, wherein the maximum tube current value is set from the change of the ECG. After determining the change in the tube current value flowing through the X-ray tube based on the standard deviation, again change the standard deviation,
A change in the tube current value flowing through the X-ray tube is obtained again based on the changed standard deviation, and a predetermined tube current value is reset from the change in the tube current value.
The electrocardiogram synchronous scanning method according to claim 1. The X-ray tube is rotated to irradiate the subject with X-rays, and the movement speed of the bed on which the subject is placed is fixed or variable, and the X-rays transmitted through the subject are converted into X-rays. An X-ray computed tomography apparatus is used that generates projection data detected by a detector and reconstructs the projection data collected according to a specific heartbeat phase of the subject to obtain tomographic image data of the subject. In the ECG synchronous scan method
A scanogram of the subject is acquired by the X-ray computed tomography apparatus;
A normal helical scan area that varies the moving speed of the bed based on the scano image and an ECG-synchronized helical scan area that makes the moving speed of the bed constant,
Set the standard deviation of the CT value variation for the scanogram,
Determine the change in the tube current value for each rotation of the X-ray tube according to the normal helical scan imaging conditions for the normal helical scan region, and set the change in the tube current value,
A change in the tube current value for each rotation of the X-ray tube is obtained for the ECG-synchronized helical scan region in accordance with the imaging conditions of the ECG-synchronized helical scan, and a constant tube is determined from the change in the tube current value. Set the current value,
With the tube current that changes to the set tube current value for the normal helical scan region being supplied to the X-ray tube, the X-ray tube is rotated to expose the X-ray to the subject. The X-ray transmitted through the subject is detected by an X-ray detector and the projection data is collected,
With the tube current of the maximum tube current value supplied to the X-ray tube with respect to the region of the ECG-synchronized helical scan, the X-ray tube is rotated to expose the X-ray to the subject, The X-ray transmitted through the subject is detected by an X-ray detector and the projection data is collected.
An ECG synchronous scanning method characterized by the above.   The imaging conditions include at least a rotational speed for rotating the X-ray tube and the X-ray detector, a moving speed of a bed on which the subject is placed, and image data of the subject obtained by reconstructing the projection data 7. The electrocardiographic synchronous scanning method according to claim 2, wherein the slice thickness is as follows. An X-ray tube that exposes X-rays to the subject;
An X-ray detector that detects the X-ray transmitted through the subject and generates projection data;
A heartbeat measuring device for measuring the heartbeat of the subject;
A scanogram acquisition unit that acquires a scanogram of the subject based on the projection data generated by the X-ray detector when the subject is exposed to the X-ray from the X-ray tube;
A standard deviation setting unit for setting a standard deviation of variations in CT values for the scanogram;
A tube current value setting unit that obtains a change in the tube current value flowing through the X-ray tube based on the standard deviation and sets a predetermined tube current value from the change in the tube current value;
In a state where the predetermined tube current value is supplied to the X-ray tube, the X-ray tube is rotated to expose the X-ray to the subject, and the X-ray transmitted through the subject is An electrocardiogram-synchronized scanning unit that detects and collects projection data detected by an X-ray detector;
A reconstruction unit that reconstructs the projection data and obtains tomographic image data of the subject;
An X-ray computed tomography apparatus comprising: An X-ray tube that exposes X-rays to the subject;
An X-ray detector that detects the X-ray transmitted through the subject and generates projection data;
A heartbeat measuring device for measuring the heartbeat of the subject;
A scanogram acquisition unit that acquires a scanogram of the subject based on the projection data generated by the X-ray detector when the subject is exposed to the X-ray from the X-ray tube;
A standard deviation setting unit for setting a standard deviation of variations in CT values for the scanogram;
A tube current calculation unit for obtaining a change in a tube current value flowing in the X-ray tube according to an imaging condition by an electrocardiogram synchronous scan based on the standard deviation;
A scan position determining unit for determining a position for determining a tube current of an electrocardiogram-synchronized scan on the scanogram;
A tube current value setting unit for setting a tube current value flowing in the X-ray tube according to a position for determining the tube current of the ECG synchronous scan from a change in the tube current value;
With the tube current having the set constant tube current value supplied to the X-ray tube, the X-ray tube was rotated to expose the X-ray to the subject, and transmitted through the subject. An electrocardiogram synchronous scanning unit that detects the X-rays with the X-ray detector and collects projection data thereof;
A reconstruction unit that reconstructs the projection data and obtains tomographic image data of the subject;
An X-ray computed tomography apparatus comprising:   10. The X-ray computer according to claim 8, wherein the standard deviation setting unit sets a standard deviation of variations in the CT value in an electrocardiogram synchronous imaging region set for the scanogram. Tomography equipment.   The tube current value setting unit obtains a change in the tube current value for each rotation of the X-ray tube in the electrocardiogram synchronous imaging region in accordance with imaging conditions of the tomographic image data of the subject. 9. The X-ray computed tomography apparatus according to claim 8, wherein the maximum tube current value is set based on the change of the X-ray. The standard deviation setting unit obtains a change in the tube current value flowing through the X-ray tube based on the standard deviation, and then changes and sets the standard deviation again.
The tube current value setting unit obtains again a change in the tube current value flowing through the X-ray tube based on the changed standard deviation, and resets the maximum tube current value from the change in the tube current value.
The X-ray computed tomography apparatus according to claim 8. An X-ray tube that exposes X-rays to the subject;
An X-ray detector that detects the X-ray transmitted through the subject and generates projection data;
A heartbeat measuring device for measuring the heartbeat of the subject;
A scanogram acquisition unit that acquires a scanogram of the subject based on the projection data generated by the X-ray detector when the subject is exposed to the X-ray from the X-ray tube;
A scan area setting unit for setting a normal helical scan area for changing the moving speed of the bed based on the scanogram and an electrocardiogram-synchronized helical scan area for making the moving speed of the bed constant;
A standard deviation setting unit for setting a standard deviation of variations in CT values for the scanogram;
A change in the tube current value for each rotation of the X-ray tube is obtained for the normal helical scan region according to the imaging conditions of the normal helical scan, and a first tube current for setting the change in the tube current value is obtained. A setting section;
A change in the tube current value for each rotation of the X-ray tube is obtained for the ECG-synchronized helical scan region in accordance with the imaging conditions of the ECG-synchronized helical scan, and a predetermined tube is determined from the change in the tube current value. A second tube current setting unit for setting a current value;
With the tube current that changes to the set tube current value for the normal helical scan region being supplied to the X-ray tube, the X-ray tube is rotated to expose the X-ray to the subject. A first projection data acquisition unit that detects the X-ray transmitted through the subject by an X-ray detector and collects projection data;
The X-ray tube is rotated and the X-ray is exposed to the subject while the tube current having a predetermined tube current value is supplied to the X-ray tube with respect to the ECG-synchronized helical scan region. A second projection data acquisition unit that detects the X-ray transmitted through the subject by an X-ray detector and collects projection data;
A reconstruction unit for reconstructing the projection data collected by the first or second data collection unit to obtain tomographic image data of the subject;
An X-ray computed tomography apparatus comprising:   The imaging conditions include at least a rotational speed for rotating the X-ray tube and the X-ray detector, a moving speed of a bed on which the subject is placed, and image data of the subject obtained by reconstructing the projection data 14. The X-ray computed tomography apparatus according to claim 9, wherein the X-ray computed tomography apparatus has a slice thickness of

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