JP2012030089A - X-ray diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate good volume data by consecutively generating projection data at a prescribed heartbeat time phase toward the turning direction of an imaging system and reconfiguring the obtained projection data.SOLUTION: The imaging system including an X-ray generating part 1 and an X-ray detecting part 2 is turned around a subject 150 several times, and the projection data are generated in each turn at the prescribed heartbeat phase. An image reconfiguration circuit 73 reconfigures the projection data, which are continuously generated in the turning direction, to form the volume data. In this process, a circuit 31 for setting turn starting timing controls the turning position of the imaging system at the prescribed heart beat phase by setting the starting timing of each turn based on an ECG signal obtained from an ECG unit 10.

Description

The present invention relates to an X-ray diagnostic apparatus and an X-ray imaging method, and in particular, X-ray image data is generated by reconstructing projection data obtained by rotating an X-ray generation unit and an X-ray detection unit. The present invention relates to a line diagnostic apparatus.

Medical image diagnostic technology using X-ray diagnostic equipment, MRI equipment, X-ray CT equipment, etc.
With the development of computer technology in the 1970s, rapid progress has been made and it has become indispensable in today's medicine.

In recent years, X-ray diagnosis has made progress mainly in the field of circulatory organs with the development of catheter procedures. An X-ray diagnostic apparatus for cardiovascular diagnosis usually includes an X-ray generation unit and an X-ray detection unit, a holding mechanism for holding them, a bed (top plate), and a signal processing unit. The C-arm or Ω-arm is used as the holding mechanism, and X-ray imaging from the optimal position and angle is possible for the patient (hereinafter referred to as the subject) when combined with a cantilever couch. I have to.

Conventionally, detectors used in the X-ray detector of the X-ray diagnostic apparatus have been X-ray films and I.D. I. (Image Intensifier) has been used. This I.I. I. In the X-ray imaging method using X-rays, X-ray projection data (hereinafter referred to as projection data) obtained by irradiating the subject with X-rays generated from the X-ray tube of the X-ray generation unit and transmitting through the subject at this time is used. ) I. Is converted into an optical image, and this optical image is taken by an X-ray TV camera and converted into an electric signal. Then, the projection data converted into the electrical signal is displayed on the monitor after A / D conversion.
For this reason, I.I. I. The image pickup method using can enable real-time shooting that was impossible with the film system, and can collect projection data with digital signals, thereby enabling various image processing.

On the other hand, the I.S. I. As an alternative, two-dimensional array flat detectors have attracted attention in recent years, and some of them have already been put into practical use. The X-ray detector provided with the flat panel detector and the X-ray generator are opposed to each other and fixed to a holding mechanism (C arm), and projection data is rotated while rotating about an axis substantially parallel to the body axis of the subject. A collection method has been proposed (see, for example, Patent Document 1).

In the method described in Patent Document 1, a rotating X-ray generation unit sequentially irradiates X-rays in a cone beam shape (two-dimensionally spread beam shape) from a plurality of directions of the subject, The transmitted X-ray dose is detected by a flat detector of the X-ray detection unit arranged behind. And
Projection data is generated from the obtained transmitted X-ray dose, and further, reconstruction processing is performed on the projection data to generate three-dimensional data (hereinafter referred to as volume data).

JP 2002-263093 A

By the way, the rotational speed of the imaging system in the above-described X-ray diagnostic apparatus is usually 40 degrees / second to 60 degrees.
For example, when the fan angle is 20 degrees, the time required for rotation of 180 degrees + fan angle is 3 to 5 seconds. When collecting projection data of the heart or the like in the rotation range of 180 degrees + fan angle using the imaging system having such a rotation speed, the heart beat rate is 1 to 2 times / second. The heart beats 3 to 10 times while the imaging system rotates in the rotation range.

That is, since the rotation speed of the imaging system is not sufficiently high with respect to the heartbeat, projection data at different heartbeat time phases of the heart are collected, and thus obtained by reconstruction processing using these projection data. Artifacts due to heart motion occur in the volume data. With respect to such a problem, the above-mentioned Patent Document 1 does not describe a solution.

On the other hand, the heartbeat synchronization method has been conventionally known as an imaging method for organs that periodically pulsate like the heart, especially by collecting projection data at the end diastole or end systole where the organ movement is relatively small. High-quality reconstructed image data can be generated.

However, during the end diastole or end systole period when there is little movement of the heart, about 30% to 40% of the cardiac cycle
However, projection data cannot be collected for the remaining 60% to 70%. For this reason, since reconstruction processing is performed using projection data from a limited direction, significant artifacts occur in the obtained volume data, and the diagnostic ability is greatly reduced.

FIG. 10 is a diagram for explaining the above problem. FIG. 10A shows an R wave (R1, R2, R3...) Of an electrocardiogram waveform (hereinafter referred to as an ECG signal). X-ray imaging timings t1 to t3, t4 at end diastole T11, T12, T13,.
To t6, t7 to t9,...

On the other hand, the X-ray generation unit and the X-ray detection unit provided in the imaging system of the X-ray diagnostic apparatus are arranged to face each other with the subject interposed therebetween as shown in FIG. It rotates at a predetermined speed. Therefore, at the X-ray irradiation timings t1 to t3 in FIG.
X-rays are irradiated to the X-ray detectors located at A3 to A3 and facing each other at these positions.

Similarly, end diastole T12, T set by ECG signals R2, R3,.
At X-ray irradiation timings t4 to t6 and t7 to t9 at 13..., The X-ray generation units located at A4 to A6 and A7 to A9 emit X-rays to the X-ray detection unit.

For example, when the fan angle φ0 is 20 degrees, the photographing range θ0 necessary for collecting projection data
Becomes 200 degrees, and projection data at the end diastole is collected in about 40% of the imaging range θ0. Therefore, for example, when the projection data is collected while rotating the imaging system in units of 1 degree, 80 projection data are collected in the rotation range θ0. That is, when only the projection data at the end diastole is collected and the reconstruction process is performed, the number of data is greatly reduced, and since these data are obtained at unequal intervals, the volume data obtained by the reconstruction process is obtained. And unacceptable artifacts occur in the image data.

On the other hand, X reconstructs projection data obtained from multiple directions to generate volume data
In line CT, for example, as described in Japanese Patent Application Laid-Open No. 2001-187048, a method for collecting projection data in a predetermined heartbeat time phase in a plurality of segments has been proposed. Since the rotational speed of the system is extremely slow compared with the rotational speed of the gantry in the X-ray CT apparatus, it is difficult to perform segment reconstruction.

The present invention has been made in view of such problems, and an object of the present invention is to repeat the rotation of the imaging system a plurality of times along a predetermined rotation path set around the subject. X-ray image data with high image quality can be generated by reconstructing this projection data by generating projection data in a predetermined heartbeat time phase of the subject substantially continuously by performing radiography. Is to provide an X-ray diagnostic apparatus.

In order to solve the above-described problem, an X-ray diagnostic apparatus according to the present invention according to claim 1 is an imaging unit that performs irradiation and detection of X-rays on a subject, and sets the imaging unit around the subject. Rotation means for performing a plurality of rotations along the predetermined rotation path, and X-ray irradiation in a predetermined heartbeat time phase of the subject while rotating the imaging means around the subject. Projection data generation means for generating projection data by performing detection, and reconstruction processing means for generating volume data by reconstructing the generated projection data are provided.

According to a tenth aspect of the present invention, there is provided an X-ray diagnostic apparatus according to the present invention, an imaging means for irradiating and detecting a subject with X-rays, and a predetermined rotation in which the imaging means is set around the subject. Rotating means for rotating at least three times along the path, and projection data generating means for generating projection data by performing X-ray irradiation and detection while rotating the imaging means around the subject. When,
Reconstruction processing means for reconstructing the generated projection data to generate volume data is provided.

1 is a block diagram showing the overall configuration of an X-ray diagnostic apparatus according to an embodiment of the present invention. The figure which shows the rotation direction of the X-ray generation part and X-ray detection part in the Example. The figure which shows the rotation range of the X-ray generation part in the Example. The figure which shows the left ventricular volume change curve and ECG signal in the diastole and systole of a cardiac cycle. The figure which shows the heartbeat time phase of the subject in the Example of this invention, the rotation position of an imaging system, and an imaging position. The figure which shows the imaging position in multiple rotation by each imaging system of the Example, and each rotation. The figure which shows the setting method of the rotation start timing in the Example. 6 is a flowchart showing a procedure for generating image data in the embodiment. The figure which shows the rotation direction of the imaging system in the modification of a present Example. The figure for demonstrating the problem in the conventional projection data collection method.

  Embodiments of the present invention will be described below with reference to the drawings.

In an embodiment of the present invention described below, an imaging system including an X-ray generation unit and an X-ray detection unit is rotated a plurality of times (N times) along a predetermined rotation path set around the subject. In each rotation, projection data at a predetermined heartbeat time phase (end diastole) of the subject is generated. Then, projection data substantially continuous in the rotation direction is generated by N rotations, and reconstruction processing is performed on the projection data to generate volume data.

(Device configuration)
The configuration of the X-ray diagnostic apparatus according to the embodiment of the present invention will be described with reference to FIGS. However, FIG. 1 is a block diagram showing the overall configuration of the X-ray diagnostic apparatus.

The X-ray diagnostic apparatus 100 of the present embodiment shown in FIG. 1 has an X-ray generator 1 for irradiating a subject 150 with X-rays and a high voltage necessary for X-ray irradiation in the X-ray generator 1. A high voltage generator 4 that supplies the X-ray, a X-ray detector 2 that detects projection data transmitted through the subject 150, a holder 6 that holds the X-ray generator 1 and the X-ray detector 2, and the holder 6 is moved and the X-ray generator 1 and X
A mechanism unit 3 for rotating the line detection unit 2 around the subject 150, rotation position information of the X-ray generation unit 1 and the X-ray detection unit 2 supplied from the mechanism unit 3, and an ECG unit to be described later An irradiation control unit 5 that controls X-ray irradiation based on heartbeat information (ECG waveform) of the subject 150 supplied from 10 is provided.

Further, the X-ray diagnostic apparatus 100 generates volume data by reconstructing the projection data generated by the X-ray detection unit 2, and further generates two-dimensional image data or 3 from the volume data.
Image calculation / storage unit 7 for generating dimensional image data, display unit 8 for displaying these image data, input of object information and various commands, setting of imaging conditions, selection of image display mode, etc. ECG unit 1 that collects ECG signals for the operation unit 9 to be performed and the subject 150
0 and a system control unit 11 that controls the above-mentioned units in an integrated manner.

The X-ray generator 1 includes an X-ray tube 15 that irradiates the subject 150 with X-rays, and an X-ray diaphragm that forms an X-ray weight (cone beam) with respect to the X-rays irradiated from the X-ray tube 15. 16 is provided.
The X-ray tube 15 is a vacuum tube that generates X-rays, and accelerates electrons emitted from a cathode (filament) by a high voltage to collide with a tungsten anode to generate X-rays. The X-ray diaphragm 16 is located between the X-ray tube 15 and the subject 150 and has a function of narrowing the X-ray beam irradiated from the X-ray tube 15 to an irradiation range of a predetermined size in the X-ray detection unit 2. Have.

Next, the X-ray detection unit 2 performs the X-ray I.D. I. 2 using a method and a fine X-ray detector
There is a method using a so-called X-ray plane detector which is dimensionally arranged. In the following, X-ray I.D. I. However, the present invention is not limited to this method, and other methods using an X-ray flat panel detector or the like may be used.

In other words, the X-ray detection unit 2 uses the X-ray I.D. I. 21, an X-ray television camera 22, and an A / D converter 23. X-ray I.D. I. 21 converts X-rays transmitted through the subject 150 into visible light, and further multiplies luminance in the process of light-electron-light conversion to generate highly sensitive projection data. On the other hand, the X-ray television camera 22 converts the above-mentioned optical projection data into an electrical signal using a CCD image pickup device, and the A / D converter 23 performs time-series output from the X-ray television camera 22. An electric signal (video signal) is converted into a digital signal.

Next, the mechanism unit 3 of the X-ray generation unit 1 and the X-ray detection unit 2 (hereinafter collectively referred to as an imaging system) based on the heartbeat information of the subject 150 supplied from the ECG unit 10. A rotation start timing setting circuit 31 for setting a rotation start timing, an imaging system movement control circuit 32 for performing control for rotating the imaging system based on timing information supplied from the rotation start timing setting circuit 31; An imaging system moving mechanism 33 that rotates the imaging system around the subject 150 in accordance with a control signal supplied from the imaging system movement control circuit 32, and a position detector 34 that detects the rotational position of the imaging system. A top plate moving mechanism (not shown) for moving the top plate 17 in the body axis direction of the subject 150 and a top plate movement control circuit (not shown) for controlling the top plate moving mechanism are provided.

Then, the rotation start timing setting circuit 31 performs the X-ray imaging in a predetermined heartbeat time phase while rotating the imaging system N times along the rotation path set around the subject 150. In order to efficiently generate projection data of a predetermined heartbeat time phase that is substantially continuous with respect to the rotation direction, the rotation start timing of the imaging system in rotation 1 to rotation N is based on heartbeat information obtained from the subject 150. To set.

On the other hand, the imaging system movement control circuit 32 sets the rotation angular velocity Vr of the imaging system based on the rotation step number P and the rotation step interval Δθ of the subject 150 obtained from the ECG unit 10 in the predetermined heartbeat time phase T1. The rotation angular velocity Vr and the rotation start timing setting circuit 31 described above.
A control signal for rotating the imaging system is supplied to the imaging system moving mechanism 33 based on the rotation start timing signal supplied from the imaging system.

Further, the imaging system movement control circuit 32 moves the imaging system in the body axis direction of the subject 150 (direction perpendicular to the paper surface of FIG. 1) in accordance with the control signal supplied from the system control unit 11. A control signal is supplied to the image pickup system moving mechanism 33, and the image pickup system moving mechanism 33 moves the image pickup system in the body axis direction based on the control signal, so that the position where projection data is collected, that is, the body axis direction. The position of the rotation path at is set.

Next, rotation of the imaging system performed by the mechanism unit 3 will be described with reference to FIGS. FIG. 2 shows the X-ray generation unit 1 and the X-ray detection unit 2 that are rotated by the imaging system moving mechanism 33, and an X-ray generation unit is provided in the vicinity of the end of the holding unit 6 constituted by the C-arm. 1 and an X-ray detector 2 are provided. 2A shows a method of sliding the holding unit 6 in the R1 direction, and FIG. 2B shows a method of rotating the holding unit 6 in the R2 direction. The imaging system including the generator 1 and the X-ray detector 2 rotates about an axis substantially parallel to the body axis of the subject 150 as a rotation center axis.

On the other hand, FIG. 3 shows the minimum necessary for reconstruction processing when X-ray imaging is performed while rotating the imaging system around the subject 150 and volume data is generated by reconstructing the obtained projection data. The imaging range θ0 of the projection data to be obtained is shown. In this case, reconstruction processing includes 1
Continuous projection data with respect to the rotation direction in the range of 80 degrees + fan angle θf is required. However, the fan angle θf is determined by the irradiation angle of the X-rays emitted from the X-ray generator 1.

The details of the method for setting the rotation start timing by the rotation start timing setting circuit 31 and the method for setting the rotation angular velocity Vr by the imaging system movement control circuit 32 will be described later.

Returning to FIG. 1, the high voltage generator 4 includes a high voltage generator 42 that generates a high voltage to be applied between the anode and the cathode in order to accelerate the thermal electrons generated from the cathode of the X-ray tube 15; A high voltage control circuit 41 that controls X-ray irradiation conditions such as tube current, tube voltage, and irradiation time in the high voltage generator 42 in accordance with an instruction signal from the system control unit 11 is provided.

Next, the irradiation control unit 5 includes an arithmetic circuit and a storage circuit (not shown), sets a predetermined heartbeat time phase T1 based on heartbeat information (heartbeat period T0) of the subject 150 supplied from the ECG unit 10, and The arithmetic circuit is provided with the imaging conditions supplied from the operation unit 9 via the system control unit 11, that is, the imaging range θ0, the imaging system rotation step interval Δθ, the total number of rotation steps M, and the heartbeat time phase T1. Based on the number P of rotation steps, the number Q of overlapping rotation steps, the number N of rotations, and the like, the imaging position in the heartbeat time phase T1 of rotation 1 to rotation N is set and stored in the storage circuit.

Furthermore, the irradiation control unit 5 is high when the rotation position of the imaging system supplied from the position detector 34 of the mechanism unit 3 via the system control unit 11 coincides with the above-described imaging position in the heartbeat time phase T1. An instruction signal for performing X-ray imaging is supplied to the voltage generator 4.

As already described, it is desirable to collect projection data at the end diastole or end systole for an organ such as the heart that periodically pulsates, where the movement is relatively small. FIG. 4 shows a volume change curve (a) in the left heart system and E obtained from the ECG unit 10.
The CG signal (b) is shown, and the ECG signal from the R wave to the T wave is the systole, and from this T wave to the next R wave is the diastole. The change in the left ventricular volume is minimized at the end diastole T1 or the end systole T2.

That is, by performing reconstruction processing on the projection data collected at the end diastole T1 or the end systole T2 at which the heart motion is minimized, it is possible to generate high-quality volume data and image data in which the influence of the motion is suppressed. It becomes possible. In the following, the case of collecting projection data at the end diastole T1 will be described, but it may be at the end systole T2.

Next, the image calculation / storage unit 7 includes a projection data storage circuit 71, an image reconstruction circuit 73, an image data storage circuit 74, and an image calculation circuit 75. The projection data generated by X-ray imaging while rotating the imaging system around the subject 150 N times is the position detector 3 of the mechanism unit 3.
4 is stored in the projection data storage circuit 71 together with the rotation position information of the imaging system detected at 4.

Next, the image reconstruction circuit 73 reads the projection data stored in the projection data storage circuit 71 and the rotation position information thereof, performs reconstruction processing, and generates volume data. The obtained volume data is stored in the image data storage circuit 74. The volume data generation method is well-known as an image reconstruction method for an X-ray CT apparatus, and a detailed description thereof will be omitted.

In addition, the image calculation circuit 75 performs, for example, a volume rendering method, an MPR (Multi-Planar-Reconstruction) method, MIP (Maximum-In) on the obtained volume data.
3D image data and 2D image data are generated by applying the (tensity-projection) method, and these image data are stored in the image data storage circuit 74.

Next, the display unit 8 is for displaying the above-described image data stored in the image data storage circuit 74 of the image calculation / storage unit 7 and combines these image data and its accompanying information. A display data generation circuit 81 for generating display data, and D for the display data
A conversion circuit 82 that generates a video signal by performing A / A conversion and TV format conversion, and a monitor 83 that displays the generated video signal are provided.

The operation unit 9 includes an input device such as a keyboard, a trackball, a joystick, and a mouse, a display panel, and various switches. The operation unit 9 inputs subject information and various command signals, X-ray irradiation conditions, and imaging. Set conditions, select heartbeat time phase, select image display mode, etc.

The imaging conditions include the imaging range θ0, the imaging system rotation step interval Δθ, the total number of rotation steps M, the heartbeat time phase T1, the heartbeat time phase T1, the rotation step number P, and the overlapping rotation step number Q, There are the number of rotations N and the like, and the heartbeat time phase includes end diastole and end systole. Furthermore, the X-ray irradiation conditions include the tube voltage of the X-ray tube 15, the tube current, the X-ray irradiation time, and the like, and the image display modes include three-dimensional image display, MIP image display, MPR image display, and the like.

On the other hand, the ECG unit 10 receives an ECG signal detected from an electrode (not shown) attached to the subject 150 and converts it into a digital signal. The system control unit 11 includes a CPU and a storage circuit (not shown), and the above-described various information input or set by the operator from the operation unit 9 is stored in the storage circuit. On the other hand, the CPU controls each unit of the high voltage generation unit 4, the X-ray detection unit 2, the mechanism unit 3, the irradiation control unit 5, the image calculation / storage unit 7, and further the display unit 8 based on such information. And control the entire system.

(Setting of rotation position and shooting position)
Next, FIG. 5 shows the setting of the rotation position and photographing position of the imaging system in the rotation 1 to rotation N described above.
And it demonstrates using FIG. In the following, for the sake of simplicity of explanation, the imaging system in these drawings performs rotations 1 to 3 (N = 3) along the same rotation path.
End diastole T11, T12, T13, ... End diastole T21, T2 in rotation 2
2, T 23,... The case where X-ray imaging is performed 4 to 6 times in each of the end diastole T 31, T 32, T 33,.

5 shows the time phase of the ECG signal of the subject on the horizontal axis, and the rotation position and imaging position of the imaging system on the vertical axis. FIG. 6 shows the rotation in rotation 1 to rotation 3. The position and the shooting position are indicated by arcs R1 to R3. In either case, the solid line (thick line) in the figure represents the rotation path of the imaging system.
In addition, circles (◯ and ●) indicate the rotation position of the imaging system capable of X-ray imaging at the end diastole in the rotation path. However, the imaging system in FIG. 6 shows a case where the rotation 1 to the rotation 3 are performed along different arcs R1 to R3 for easy understanding of the description. It rotates at a predetermined angular velocity Vr. In the following description, the rotational position of the X-ray generator 1 is described as the rotational position of the imaging system.

As shown in FIG. 5 and FIG. 6, the imaging system movement control circuit 32 of the mechanism unit 3 includes the imaging system movement mechanism 3.
3 is controlled to rotate the imaging system from the rotation position θ1 toward the rotation position θ200 (M = 200) at the rotation angular velocity Vr. And in rotation 1, end diastole T11, T12, T13, ...
When the imaging system reaches predetermined imaging positions θ1 to θ6, θ16 to θ21, θ31 to θ36,..., The irradiation controller 5 controls the high voltage generator 4 to perform X-ray imaging.

If such intermittent X-ray imaging is completed in the rotation 1, the imaging system movement control circuit 3
2 returns the imaging system to the first rotation position θ1 and starts rotation 2 based on the rotation start timing signal supplied from the rotation start timing calculation circuit 31. And end diastole T21, T
22, T23,..., The imaging system is in the shooting positions θ7 to θ11, θ22 to θ26, θ.
When reaching 37 to θ41,..., X-ray imaging is performed.

By the same procedure, the imaging system starts to rotate 3 at the rotation position θ1, and the end diastole T
31, T32, T33,..., Shooting positions θ12 to θ16, θ27 to θ31,
When X is reached, X-ray imaging is performed.

In this case, the rotation start timing is set so that the rotation position of the imaging system at the end of expansion of rotation 1 to rotation 3 overlaps as shown in FIGS. 5 and 6. For example, the last rotation position at the end diastole T11, T12, T13 of the rotation 1 and the end diastole T21, T2 of the rotation 2
2 and the initial rotation position at T23 are set to coincide with each other at θ6, θ21, and θ36.

Similarly, the final rotation position and the rotation 3 in the end diastole T21, T22, T23 of the rotation 2
The first rotational positions at the end diastole T31, T32, T33,.
.. coincides with each other at θ41, and the last rotation position at the end diastole T31, T32,... of rotation 3 and the first rotation position at the end diastole T12, T13,.・
• Set to match.

By applying such an X-ray imaging method, for example, the heartbeat period during X-ray imaging differs from the heartbeat period T0 before X-ray imaging of the subject used when setting the rotational angular velocity Vr. Even in this case, projection data at the end diastole can be continuously synthesized with respect to the rotation direction.

That is, when the projection data of the end diastole T11 cannot be obtained at the rotation position θ6 of the rotation 1 due to the fluctuation of the heartbeat period, the projection data of the end diastole obtained by the rotation position θ6 of the rotation 2 is used. It becomes possible to complement. In this case, the irradiation control unit 5 is connected to the ECG unit 10.
The projection data of the end diastole T11 at the rotation position θ6 of the rotation 1 cannot be collected based on the heartbeat information supplied from the position and the rotation position information of the imaging system supplied from the position detector 34 of the mechanism unit 3. Is recognized, the high voltage generator 4 is controlled to stop the X-ray irradiation, and the rotation position θ6 of the rotation 2 is set to a new imaging position.

(Rotation start timing setting)
Next, a method for setting the rotation start timing in the rotation start timing setting circuit 31 of the mechanism unit 3 will be described with reference to FIG. FIG. 7 shows the rotation 1 to rotation 3 when the imaging system rotation 1 to rotation 3 is performed with respect to the rotation positions θ1 to θ200 shown in FIG. 6 to perform X-ray imaging in the end diastole T1. The rotation position and imaging position of the imaging system with respect to the elapsed time with reference to the rotation start timing are shown.

However, in this case as well, in the same manner as in FIG. 5 or FIG. 6, in the imaging system of rotation 1 to rotation 3, six rotation positions are set at the end diastole T1, and predetermined rotation (for example, rotation 2) is performed. The first rotation position θ6 of the end diastole T1 in () coincides with the last rotation position θ6 of the end diastole T1 in the preceding rotation (rotation 1), and the last rotation position in the predetermined rotation (rotation 2). Rotation position θ11 of
Shows the case where it coincides with the first rotation position θ11 in the subsequent rotation (rotation 3), but the number of rotation steps P and the number of overlapping rotation steps Q at the end of each expansion are limited to this embodiment. Not.

First, the rotation start timing setting circuit 31 of the mechanism unit 3 shown in FIG.
In the ECG signal of the subject 150 supplied from the ECG unit 10 via the time phase φ
4 R waves are detected, and the heartbeat period T0 is measured from the RR interval. Next, a time phase φ3 that is set back from each detected R wave by the end diastole T1 is set, and further, time phases φ2 and φ1 that are set back from the time phase φ3 by a period Tx and a period 2Tx are set.

Next, as shown in FIG. 7, the rotation start timing setting circuit 31 sets a time phase φ3 that goes back from the R wave of the ECG signal by the period T1 as the rotation start timing of the rotation 1, and then this setting. The image pickup system movement control circuit 32 controls the image pickup system movement mechanism 33 to rotate the image pickup system at the rotation start timing with the rotation position θ1 as the rotation start position. When the imaging system reaches imaging positions θ1 to θ6, θ16 to θ21,... Preset by the irradiation controller 5, X-ray imaging is performed at these imaging positions.

Similarly, the rotation start timing setting circuit 31 starts the period T11 (from the R wave of the ECG signal.
The time phase φ2 retroactive by T11 = T1 + Tx) is set as the rotation start timing of rotation 2, and the time phase φ1 retroactive by a period T12 (T12 = T1 + 2Tx) from the R wave of the electrocardiographic waveform is rotated by rotation 3. Set to the start timing. Next, the imaging system movement control circuit 32 controls the imaging system movement mechanism 33 based on these rotation start timings, and rotates the imaging system at the rotation start timing with the rotation position θ1 as the rotation start position. . The imaging system in the rotation 2 is the irradiation control unit 5.
If the imaging system in rotation 3 reaches the imaging positions θ12 to θ15, θ27 to θ30,... At the imaging positions θ7 to θ11, θ22 to θ26,. X-ray imaging is performed at the imaging position.

但し、回動ステップ間隔Δθは、回動位置θ１乃至θＭにおける回動ピッチであり撮影
範囲θ０／全回動ステップ数Ｍによって算出される。又、Ｐは既に述べたように拡張末期
Ｔ１における回動ステップ数、Ｑは回動１乃至回動Ｎの間で重複する拡張末期Ｔ１の回動
ステップ数を示しており、図５乃至図７では、θ０＝２００度、Ｍ＝２００，Ｐ＝６、Ｑ
＝１、Δθ＝１度、Ｔ１＝４００ｍｓｅｃの場合について示している。 (Rotation angular velocity setting)
By the way, when the imaging system is rotated in the rotation positions θ1 to θM (M = 200) of the imaging range θ0 (θ0 = 200 degrees), the rotation range of (PQ) Δθ is rotated during the end diastole T1. It is necessary to move. Accordingly, the rotational angular velocity Vr of the imaging system is calculated by the following equation (1).

However, the rotation step interval Δθ is a rotation pitch at the rotation positions θ1 to θM, and is calculated by the shooting range θ0 / the total number M of rotation steps. As described above, P indicates the number of rotation steps at the end diastole T1, Q indicates the number of rotation steps at the end diastole T1 that overlaps between the rotations 1 to N, and FIGS. Then, θ0 = 200 degrees, M = 200, P = 6, Q
= 1, Δθ = 1 degree, and T1 = 400 msec.

That is, the imaging system movement control circuit 32 of the mechanism unit 3 is configured so that the photographing range θ0, the rotation step interval Δθ, the rotation step number P at the end diastole, and the overlapping rotation are preset by the operation unit 9 or the system control unit 11. Based on the number of steps Q, the rotational angular velocity Vr is set.

The end diastole T1 in the above formula (1) is a value set at a predetermined ratio η with respect to the heartbeat period T0 of the subject. In the above-described embodiment, η = 40%. Therefore, when the heartbeat period T0 of the subject fluctuates with time, the imaging system movement control circuit 32 of the mechanism unit 3 rotates by updating the rotation angular velocity Vr based on the above equation (1). In each of 1 to N, projection data can be reliably generated at the photographing position set in advance by the irradiation controller 5.

(Image data generation procedure)
Next, an image data generation procedure in the X-ray diagnostic apparatus 100 according to the present embodiment will be described with reference to FIGS. FIG. 8 is a flowchart showing a procedure for generating image data.

An operator of the X-ray diagnostic apparatus 100 first inputs subject information regarding the subject 150 in the operation unit 9, selects a heartbeat time phase (end diastole), sets X-ray irradiation conditions and imaging conditions, and selects an image display mode. Etc. The input information, selection information, and setting information described above are stored in the storage circuit of the system control unit 11 (step S1 in FIG. 8).

Further, the above-described imaging conditions are supplied to the irradiation control unit 5 via the system control unit 11 and temporarily stored in the storage circuit. In the following, θ0 = 200 degrees, Δθ = 1 degree, M = 200, P = 6,
Although the case of Q = 1 and N = 3 will be described, the present invention is not limited to this.

When the above input and setting are completed, the operator attaches the electrode of the ECG unit 10 to the subject 150. The ECG unit 10 then obtains the EC of the subject 150 obtained at this time.
The G signal is once converted into a digital signal, and then supplied to the irradiation control unit 5 via the system control unit 11. The irradiation control unit 5 measures the heartbeat period T0 from the R wave interval or heart rate of the ECG signal, The end diastole T1 in the heartbeat cycle T0 is set (step S2 in FIG. 8).

Further, the irradiation controller 5 captures the imaging positions θ1 to θ6, θ16 to θ21, θ of the rotation 1 at the end diastole based on the above-described shooting conditions already stored in the storage circuit and the end diastole period T1.
31 to θ36,..., Rotation 2 shooting positions θ7 to θ11, θ22 to θ26, θ37
Through θ41,..., Rotation 3 shooting positions θ12 through θ15, θ27 through θ30,... Are set (step S3 in FIG. 8).

On the other hand, the rotation start timing setting circuit 31 of the mechanism unit 3 is connected to the E via the system control unit 11.
The R wave of time phase φ4 is detected in the ECG signal of the subject 150 supplied from the CG unit 10, and the heartbeat period T0 is measured from the R wave interval. Next, a time phase φ3 that is set back from each detected R wave by the end diastole T1 is set, and time phases φ2 and φ1 that are set back from the time phase φ3 by a period Tx and 2Tx are set. Then, the time phase φ3, the time phase φ2, and the time phase φ1 are set to the rotation start timing in the rotations 1 to 3 (see FIG. 7).

Further, the rotation start timing setting circuit 31 is connected to the irradiation control unit 5 via the system control unit 11.
Alternatively, the rotational angular velocity V is based on the imaging conditions supplied from the operation unit 9 or the above-described end diastole T1.
r is set (step S4 in FIG. 8).

Next, the imaging system movement control circuit 32 of the mechanism unit 3 is connected to the operation unit 9 via the system control unit 11.
The imaging system moving mechanism 33 is controlled based on the command signal supplied from, and the imaging system is set to the first rotation position θ1. Next, after the operator injects a contrast medium into the diagnostic region of the subject 150 (step S5 in FIG. 8), the operator inputs a command signal for starting X-ray imaging of rotation 1 from the operation unit 9. The command signal is supplied to the system control unit 11 to start the rotation 1 X-ray imaging (step S6 in FIG. 8).

Next, the system control unit 11 performs X-ray irradiation at the time phase φ3 of the ECG signal of the subject 150 supplied from the ECG unit 10 following the imaging start command signal.

At the time of X-ray imaging at the rotational position θ1, the irradiation control unit 5 performs the system control 11 through the time phase φ3 of the ECG signal supplied from the ECG unit 10 and the position detector 34 of the mechanism unit 3.
After confirming the rotation position θ1 of the imaging system supplied from, an X-ray irradiation instruction signal is supplied to the high voltage generator 4. The high voltage control circuit 41 of the high voltage generator 4 receives the instruction signal supplied from the irradiation controller 5 and controls the high voltage generator 42 based on the already set X-ray irradiation conditions. A high voltage is applied to the X-ray tube 15 of the X-ray generator 1.

Next, the X-ray tube 15 to which the high voltage is applied is applied to the subject 150 via the X-ray restrictor 16.
The X-rays irradiated with the X-ray and transmitted through the subject 150 are X-rays I.D. I. 21 is projected. On the other hand, X-ray I.D. I. 21 converts X-rays transmitted through the subject 150 into an optical image, and the X-ray television camera 22 converts the optical image into an electrical signal (video signal).

The video signal output in time series from the X-ray television camera 22 is converted into an A / D converter 2.
3 is converted into a digital signal and stored as projection data in the projection data storage circuit 71 of the image calculation / storage unit 7. In this case, information on the photographing position θ1 is added to the projection data stored in the projection data storage circuit 71 as supplementary information.

On the other hand, the system control unit 11 controls the imaging system movement control circuit 32 of the mechanism unit 3 to rotate the imaging system around the subject 150 at the rotation angular velocity Vr. Further, the position detector 3 of the mechanism unit 3
The irradiation control unit 5 to which the rotation position of the imaging system detected by 4 is supplied via the system control unit 11 is when the rotation position of the imaging system coincides with the imaging position stored in the storage circuit in advance. Is supplied with an instruction signal for X-ray irradiation to the high voltage control circuit 41 of the high voltage generator 4. The projection data at the rotational position θ2 obtained by X-ray imaging based on this instruction signal is stored in the projection data storage circuit 71 together with the imaging position information.

In the same manner, the imaging system rotates the rotation 1 at the rotation angular velocity Vr and performs X-ray imaging at preset imaging positions θ3 to θ6, θ16 to θ21, θ31 to θ36,. The obtained projection data is stored in the projection data storage unit 71 (step S7 in FIG. 8).
.

When the X-ray imaging in the rotation 1 is completed, the imaging system movement control circuit 32 of the mechanism unit 3 controls the imaging system movement mechanism 33 based on the instruction signal supplied from the system control unit 11 to rotate the rotation position. The imaging system is reset to θ1. Next, after the operator injects the contrast medium again into the diagnostic region of the subject 150, the operator inputs a command signal for starting the rotation 2 X-ray imaging in the operation unit 9. This command signal is supplied to the system control unit 11 to rotate 2
X at the photographing positions θ7 to θ11, θ22 to θ26, θ37 to θ41,.
The line shooting is performed by the same procedure as the rotation 1, and the obtained projection data is stored in the projection data storage circuit 71 together with the shooting position information (steps S4 to S6 in FIG. 8).

Further, the projection data obtained by performing X-ray imaging in the same manner for the imaging positions θ12 to θ15, θ27 to θ30,.
1 is stored. That is, the projection data storage circuit 71 stores the projection data of the end diastole T1 obtained by intermittent X-ray imaging in the rotations 1 to 3 together with the imaging position information (steps S5 to S5 in FIG. 8). S7).

Next, the image reconstruction circuit 73 of the image calculation / storage unit 7 performs a convolution process using the projection data stored in the projection data storage circuit 71 and its photographing position information. Further, volume data in the region of interest is generated by back projecting the convolution processed projection data onto a lattice point of a three-dimensional lattice virtually set in the region of interest of the subject 150, and the obtained volume data is converted into an image. The data is stored in the data storage circuit 74 (step S9 in FIG. 8). Note that a method for generating volume data from projection data collected by an X-ray detection unit having a two-dimensional detection element is well known as an image reconstruction technique in an X-ray CT apparatus. Omitted.

The image calculation circuit 75 uses the volume data generated by the above-described method, and uses the volume data generated by the above-described method, based on the image display mode selected by the operator using the operation unit 9, and the desired 3D image data and 2
Dimensional image data is generated, and the obtained image data is temporarily stored in the image data storage circuit 74 (step S10 in FIG. 8).

On the other hand, the system control unit 11 reads out image data corresponding to a preset image display mode from the image data storage circuit 74 and displays it on the monitor 83 of the display unit 8. That is, the system control unit 11 reads out desired image data stored in the image data storage circuit 74 and supplies it to the display data generation circuit 81 of the display unit 8, and the display data generation circuit 81 includes the image data generation circuit. Image data for display is generated by combining the image data supplied from 73 and the accompanying information such as the subject information or imaging conditions supplied from the system control unit 11. Next, the conversion circuit 82 performs D / A conversion and TV format conversion on the display image data, generates a video signal, and displays it on the monitor 83 (step S11 in FIG. 8).

According to the present embodiment described above, the image reconstruction is performed using the projection data collected in the end-diastolic or end-systolic heartbeat time phase in which the movement of the subject is relatively small. Can be reduced. Further, by performing N rotations on the same rotation path, it is possible to continuously generate projection data in a predetermined heartbeat time phase with respect to the rotation direction.

Further, according to the present embodiment, the rotation start timing and the rotation angular velocity of the rotations 1 to N are set or updated based on the heartbeat information obtained from the subject. Regardless of the temporal change, it is possible to always set a suitable position of the imaging system, and to generate projection data continuous in the rotation direction. Further, since the rotation ranges of the rotations 1 to N in the predetermined heartbeat time phase are set so that the end portions overlap each other, the rotation direction even when there is a temporal variation in the heartbeat cycle of the subject. Projection data continuous to each other can be generated. Therefore, it is possible to generate high-quality image data by reconstructing the projection data generated by this embodiment.

Further, according to the above-described embodiment, X-ray imaging is performed only when the imaging system arrives at a predetermined heartbeat time phase with respect to a preset imaging position. Therefore, the same imaging position is overlapped by different rotations. X-ray imaging can be prevented. For this reason, the exposure dose to the subject can be reduced.

As mentioned above, although the Example of this invention has been described, this invention is not limited to said Example, It can change and implement. For example, in the above-described embodiment, the X-ray irradiation is controlled so that X-ray imaging at the same imaging position does not overlap between rotations. However, X-ray imaging at the same imaging position is overlapped between rotations. The projection data effective for the reconstruction process may be selected from the obtained projection data based on the photographing position information.

Further, in all of the rotations 1 to 3 in FIG. 7, the rotation position θ1 is set as the rotation start position, and the rotation starts based on the rotation start timing set for each rotation. For example, the rotation 2 is set to the rotation position θ6, the rotation 3 is set to the rotation position θ11 as the rotation start position, and the rotations 1 to 3 are set to the same rotation start timing. The rotation may be performed at (beat time phase φ3).

Furthermore, in the above-described embodiment, the case where the imaging system in the rotation 1 to the rotation 3 rotates in the same direction as shown in FIG. 6 is described. For example, as shown in FIG. It may be changed alternately. In this case, the movement control of the imaging system is somewhat complicated, but the time required for collecting projection data can be reduced.

On the other hand, in the above-described embodiment, the case where the projection data is generated for the subject into which the contrast agent is injected has been described. However, the projection data is obtained by a plurality of rotations before and after the contrast agent injection. Volume data may be generated by reconstructing projection data newly generated by subtraction of projection data before injection of contrast agent and projection data after injection of contrast agent.

In the above-described embodiment, the end diastole T1 is set to 40% of the cardiac cycle T0 in order to simplify the drawing.
However, in order to eliminate the influence of the movement of the region to be imaged, it is desirable to set the end diastole T1 further smaller. Therefore, the number of rotations N is set in the range where the time required for generating projection data does not become so large. It is desirable to set a larger value than in the embodiment.

On the other hand, ECG signals are collected in order to obtain heartbeat information of the subject, but other biological information such as a left ventricular volume change curve shown in FIG. 4 may be used.

In the above-described embodiment, the volume data obtained by the image reconstruction process of the projection data is volume-rendered three-dimensional image data, MIP image data, or MP
Although the case of generating two-dimensional image data such as R image data has been described, the present invention is not limited to this.

On the other hand, the period during which X-ray irradiation is performed is not limited to the end diastole but may be the end systole. In this case, the number P of rotation steps, the imaging range θ0, the rotation pitch Δθ, the number Q of overlapping rotation steps, the rotation step interval Δθ, etc. at the end diastole or end systole are limited to the values shown in the above embodiments. Not.

Further, in the above-described embodiment, the case where X-ray imaging is performed only in a predetermined heartbeat time phase (end diastole) has been shown, but projection data obtained by performing X-ray imaging at predetermined intervals while rotating the imaging system. The projection data obtained at the end diastole may be selected from among the above and reconstructed. In this case, the amount of X-ray exposure to the subject increases, but there is an advantage that control for X-ray imaging is simplified.

In addition, the injection of the contrast medium into the subject may be performed every time imaging is performed at the rotation 1 to rotation N as shown in the above-described embodiment. The shooting in motion N may be performed continuously. The latter method can reduce the amount of contrast medium to be injected, but the former method is suitable for a subject whose breath holding time cannot be long.

According to at least one embodiment described above, it is possible to generate projection data of a subject at a predetermined heartbeat time phase substantially continuously in the rotation direction, and by reconstructing the projection data Good quality image data can be generated.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... X-ray generation part 2 ... X-ray detection part 3 ... Mechanism part 4 ... High voltage generation part 5 ... Irradiation control part 6 ... Holding part 7 ... Image calculation and memory | storage part 8 ... Display part 9 ... Operation part 10 ... ECG unit 11 ... System control unit 15 ... X-ray tube 16 ... X-ray restrictor 17 ... Top plate 21 ... X-ray I.D. I.
22 ... X-ray TV camera 23 ... A / D converter 31 ... rotation start timing setting circuit 32 ... imaging system movement control circuit 33 ... imaging system movement mechanism 34 ... position detector 41 ... high voltage control circuit 42 ... high voltage generation Projector 71 ... Projection data storage circuit 73 ... Image reconstruction circuit 74 ... Image data storage circuit 75 ... Image operation circuit 81 ... Display data generation circuit 82 ... Conversion circuit 83 ... Monitor 100 ... X-ray diagnostic apparatus 150 ... Subject

Claims (10)

Imaging means for irradiating and detecting X-rays on the subject;
Rotation means for rotating the imaging means a plurality of times along a predetermined rotation path set around the subject;
Irradiation control means for controlling X-ray irradiation in a predetermined heartbeat time phase of the subject based on heartbeat information of the subject and rotation position information of the imaging means;
Projection data generating means for generating projection data by performing X-ray irradiation and detection under the control of the irradiation control means;
Reconstructing processing means for reconstructing the generated projection data to generate volume data,
The X-ray diagnostic apparatus characterized in that the irradiation control means controls so that a part of X-ray irradiation positions by the plurality of rotations in a predetermined heartbeat time phase of the subject overlap each other. The X-ray diagnostic apparatus according to claim 1, wherein the rotation unit rotates the imaging unit at least three times in the rotation path. The X-ray diagnostic apparatus according to claim 1, wherein the reconstruction processing means performs reconstruction processing on projection data substantially continuous in a rotation direction generated by the plurality of rotations. 3. The X-ray diagnostic apparatus according to claim 2, wherein the reconstruction processing means reconstructs the projection data based on rotation position information of the imaging means added as incidental information of the projection data. . Heart rate information collecting means for collecting heart rate information of the subject and position detecting means for detecting the rotational position of the imaging means, wherein the irradiation control means is the heart rate information of the subject supplied from the heart rate information collecting means The X-ray diagnostic apparatus according to claim 1, wherein X-ray irradiation in the imaging unit is controlled based on rotation position information of the imaging unit supplied from the position detection unit. The X-ray diagnostic apparatus according to claim 1, wherein the rotation unit sets or updates a rotation angular velocity of the imaging unit based on heartbeat information of the subject. The X-ray diagnosis apparatus according to claim 1, wherein the rotation unit sets a rotation start timing of the imaging unit based on heartbeat information of the subject. The X-ray diagnostic apparatus according to claim 1, wherein the projection data generation unit generates projection data in a range of 180 degrees + fan angle or more. The X-ray diagnostic apparatus according to claim 5, wherein the heartbeat information collecting unit collects an ECG signal of the subject as the heartbeat information. Image data generating means, wherein the image data generating means generates three-dimensional image data or two-dimensional image data by applying any one of a volume rendering method, an MPR method, and a MIP method to the volume data. The X-ray diagnostic apparatus according to claim 1.

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