JPH09262230A - X ray ct apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X ray CT apparatus capable of obtaining high quality image data by efficiently conducting helical scanning. SOLUTION: The X ray CT 1 apparatus compruses plural X ray beam generators 9-1, 9-2 for exposing an object laid on a bed with X rays, X ray detectors 15-1, 15-2 for detecting the exposed X ray from the X ray beam sources 9-1, 9-2, a means for revolving the plural X ray sources 9-1, 9-2 surrounding the object, an X ray source sliding unit 11 for setting the spacing in the direction of the revolution axis of the plural X ray sources 9-1, 9-2. A helical scanning is conducted by revolving at least two X ray sources 9-1, 9-2 and moving the bed in the direction of the revolving axis at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus, and more particularly to an X-ray CT apparatus that performs a helical scan.

[0002]

2. Description of the Related Art In recent years, various continuous-rotation CTs have been proposed which continuously rotate a rotating unit including an X-ray beam generation source (X-ray tube) that emits an X-ray beam. Such a continuous rotation type CT is a slip ring for supplying a high voltage or transmitting a signal from a fixed portion fixed to a gantry to the rotating portion, or transmitting a signal between the fixed portion and the rotating portion. It is realized by using a signal transmission means using light as a medium for performing. In addition, the continuous rotation type CT includes a continuous rotation type third generation CT and a continuous rotation type fourth generation CT.
There is.

The continuous rotation type third generation CT has a detector that rotates in synchronization with each X-ray beam generation source for each X-ray beam generation source. As the detector, there are a single-row detector and a two-dimensional detector, which are shown in FIGS. 38 (a) and 38 (b), respectively. As shown in FIG. 38 (a), the single-row detector 100 has X
The detection units 103 are arranged in a line in an arc shape (or a linear shape) corresponding to the X-ray beam emitted from the line beam generation source 101. In addition, the two-dimensional detector 110 is
As shown in FIG. 38 (b), the X-ray beam generation source 111 has a plurality of arc-shaped detection unit rows 113 in the rotation axis direction (hereinafter, simply referred to as the rotation axis direction). The two-dimensional detector includes a detector having two rows of detectors, a flat detector having a linear detector row, and an image intensifier (II).

A continuous rotation type fourth generation CT is shown in FIG. As shown in FIG. 39, the continuous rotation type fourth generation CT is
An X-ray beam generation source 121 that rotates on a predetermined circumference around a rotation axis, and is fixed to a pedestal and has the rotation axis as a center,
It has a detector 123 arranged in a cylindrical shape having an inner surface as a detection surface.

Further, an X-ray C having a plurality of X-ray beam sources and detectors corresponding thereto and having a moving means for moving the X-ray beam sources in a direction parallel to the rotation axis thereof.
In the T-apparatus, it has been proposed that the X-ray beam generation source can be moved according to the slice thickness. In the case of the third generation CT having an X-ray beam generation source and a detector that rotates in synchronization with the X-ray beam generation source, the detector along with the X-ray beam generation direction is parallel to the rotation axis. Including moving to. Here, the slice thickness is generally defined as a value obtained by projecting the half value width of the sensitivity distribution in the rotation axis direction of the detector array with respect to the incident X-ray onto the rotation center. It should be noted that the thickness at the rotation center of the fan-shaped X-ray beam incident on the detector row may be considered.

The X-ray beam source is moved in a direction parallel to its rotation axis when the slice thickness is changed.
This is to prevent a part that is not photographed or a part that is photographed by overlapping. This makes it possible to perform continuous scanning of a plurality of continuous slices regardless of which slice thickness is selected. The conventional scan is a scan mode in which the top plate on which the subject is placed is not moved during the scan.

Further, in the continuous rotation type third generation CT and the continuous rotation type fourth generation CT, the top plate is continuously moved along with the rotation of the rotating portion, thereby making the image data of the subject into a spiral shape. It is also possible to perform a helical scan to collect. Further, in the continuous rotation type 3rd generation CT and the continuous rotation type 4th generation CT, when helical scan is performed with a two-dimensional detector, the speed of helical scan is improved, the resolution in the slice direction is improved, and the partial volume is increased. This has the effect of reducing artifacts (artifacts that occur when the CT value changes due to the proportion of different substances that occupy part of the unit volume).

[0008]

However, an X-ray CT apparatus having a one-row detector (continuous rotation type third generation C
T, including the continuous rotation type fourth generation CT), the locus of the helical scan in which the horizontal axis represents the scan position in the rotational axis direction of the subject and the vertical axis represents the rotation angle of the X-ray beam source or detector. , As shown in FIG. The trajectory of the helical scan is a spiral trajectory centered on the rotation axis when considered three-dimensionally.

Here, the scan position in the direction of the rotation axis is X
It is represented by the position of the intersection of the rotation axis and the plane defined by the focal point of the line beam generation source and the center of the X-ray incident on the target detector array in the rotation axis direction. It may be considered that the center of the fan-shaped X-ray beam incident on the detector row in the beam thickness direction intersects the rotation axis.

In recent years, it has been required to increase the scanning speed (helical scanning speed) in the rotational axis direction. However, if the point plate feed speed per rotation is fixed,
In order to increase the speed, the speed of the rotating part must be increased. However, there is a mechanical limitation in increasing the speed of the rotating unit, and there is a problem that the helical scan speed is limited by the capacity of the rotating mechanism.

As a method for performing a helical scan at high speed, there is a method using an n-row detector (two-dimensional detector). In the case of the X-ray CT apparatus having the detectors of n rows, the helical scan speed can be increased by n times when the top plate feed per rotation is matched with the total slice thickness.

The trajectory of a helical scan in an X-ray CT apparatus having, for example, a three-row detector as a two-dimensional detector is
If the horizontal axis is the scan position in the rotational axis direction of the subject and the vertical axis is the rotation angle of the X-ray beam source or detector,
It is represented as in FIG. 41. When viewed three-dimensionally, the trajectory of this helical scan becomes a plurality of spiral trajectories centered on the rotation axis.

However, as the detector array is separated from the plane (midplane) perpendicular to the rotation axis including the X-ray beam generation source, the X-ray beam entering the nuclear detector array becomes an angle with respect to the midplane. Since the (cone angle) becomes large, the image quality deteriorates. That is, although the speed is high, the image quality is deteriorated.

As described above, performing the high-quality and high-speed helical scan is limited in the conventional method. Therefore, as a method of high-speed helical scanning that is not affected by the cone angle, an X-ray C having a plurality of X-ray beam generation sources is used.
A helical scan with the T device can be considered.

However, if the position of the X-ray beam generator in the direction of the rotation axis is fixed so that a plurality of consecutive slices can be taken by the conventional scan, the loci of helical scan by the plurality of X-ray beam generators will not be at equal intervals. The problem arises. This will be described by taking an X-ray CT apparatus having two X-ray beam generation sources as an example.

For example, as shown in FIG. 42, it is assumed that two X-ray beam sources A and B are set at an angle of 120 degrees and an interval I _CONV in the direction of the rotation axis to perform a conventional scan. At this time, in order to obtain two consecutive slice images, the slice thickness is set to the interval I _CONV .

[0017] However top plate sliding amount per rotation remains in this interval I _CONV, the helical-scan that twice the interval I _CONV, as shown in FIG. 43, from the trajectory by the X-ray beam source A X a rotation axis direction of the spacing I _Hel1 up trajectories by linear beam source B, becomes a value different from the rotation axis direction of the spacing I _Hel2 from the trajectory by the X-ray beam source B to the locus by X-ray beam source a, The trajectories of the two helical scans are not evenly spaced (I _hel1 ≠ I _hel2 ,
2 × I _CONV = I _hel1 + I _hel2 ).

In FIG. 43, each slice thickness is represented by an interval I.
_When it is set to _CONV , it is shown in Fig.
It looks like 4. It can be seen that in such a helical scan that is not equidistant, there are overlaps and gaps in the locus. Therefore, an overlapped scanned portion and an unscanned missing portion occur, resulting in deterioration of image quality.

Further, as shown in FIG. 45, the three X-ray beam sources C, D and E have an angle of 120 degrees and a rotation axis direction interval I.
It is assumed that _CONV is set and a conventional scan is performed. However, when the top plate slide amount per rotation is kept at this interval I _CONV and a helical scan is performed with three times the interval I _CONV , as shown in FIG. 46, three X-ray beam generators C, D and E are used. The loci of helical scans will overlap each other. As described above, it is understood that the setting of the interval of the X-ray beam generation source of the conventional scan cannot be applied to the helical scan.

Therefore, when the setting of the interval of the X-ray beam source of the conventional scan is applied to the helical scan, the loci of the helical scan corresponding to the respective X-ray beam sources are not at equal intervals, and the slice thickness is taken into consideration. , There are overlaps and missing parts in the trajectory,
There is a problem of causing deterioration of image quality.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an X-ray CT apparatus capable of obtaining high-quality image data by effectively performing a helical scan. .

[0022]

In order to achieve the above object, the present invention provides a plurality of X-ray beam generators for irradiating a subject on a bed with X-rays, and the X-ray beam generators. Detector for detecting X-rays, rotating means for rotating the plurality of X-ray beam generation sources around the subject, and setting means for setting intervals between the plurality of X-ray beam generation sources in the rotation axis direction. With the above, the gist is to rotate the at least two X-ray generation sources and move the bed in the rotation axis direction to perform the helical scan.

In the X-ray CT apparatus of the present invention, the X-ray beam source setting means sets the distance between the at least two X-ray beam sources used for helical scanning in the rotational axis direction. The helical scan can be effectively performed, and high-quality image data can be obtained.

The setting means may rotate the rotation axes of the plurality of X-ray beam generating sources so that at least two of the X-ray beam generating sources used for helical scanning have helical orbits by helical scanning at equal intervals. You may make it set the space | interval of a direction. In this case, a multi-slice helical scan without the influence of the cone angle becomes possible. Further, the setting means divides the area in the rotation axis direction for helical scanning into a plurality of areas, and for each area, one X-ray beam generation source and a detector corresponding thereto are used to perform helical scanning. You may make it set the space | interval of the rotation axis direction of at least 2 said X-ray beam generation source used for scanning. in this case,
The region in the direction of the rotation axis is divided into a plurality of regions, and each region is set so that a detector corresponding to one X-ray beam generation source performs helical scanning. As a result, the image quality is higher (when the scanning speed is the same) as compared with the case where the orbits of the helical scan are set to have equal intervals. Further, the setting means sets the number of the regions to be the same as the number of the X-ray beam generation sources, and performs helical scanning with a detector corresponding to one X-ray beam generation source for each region. You may make it set the space | interval of the rotation axis direction of the said some X-ray beam generation source.
In this case, the helical scan is completed once. Further, the setting means sets the interval in the rotation axis direction of at least two of the X-ray beam generation sources used for the helical scan so that the boundaries of the regions are overlapped and the helical scan is performed. May be. In this case, in this case, since the data can be reconstructed without using the data in the respective areas, the image quality at the boundary portion is improved. Further, in the data collected by the detector, at least a part of the overlapped portion may be subjected to arithmetic averaging with linear weighting. In this case, artifacts and discontinuity at the boundary can be eliminated. Further, the setting means rotates the at least two X-ray beam generation sources so that at least a part of the spiral orbits of the helical scan of the at least two X-ray beam generation sources used for the helical scan become the same spiral orbit. You may make it set the space | interval of an axial direction. In this case, it is possible to eliminate the artifact caused by the difference in the spiral trajectory due to the helical scan. Further, the X-ray beam generation source may be controlled in its irradiation timing so as to irradiate X-rays only to a region where a helical scan is performed. In this case, exposure can be minimized. Further, the detector may be rotated by the rotating means in synchronization with the corresponding X-ray beam generation source. further,
The detector may have a cylindrical shape having an inner surface as a detection surface. Further, the setting means may move the X-ray beam generation source and the corresponding detector by the same amount as the X-ray beam generation source in the rotation axis direction. In this case, since the X-ray incident position is constant, the detector sensitivity can always be kept the same. Further, the width of the detector in the rotation axis direction can be reduced. Further, the setting means is
The X-ray beam generation source and the detector corresponding thereto may be fixed on the same fixing member, and the X-ray beam generation source and the detector may be moved together with the fixing member.
In this case, it can be guaranteed that the X-ray generation source and the detector have the same amount of movement. Further, the detector may be a two-dimensional detector in which detection segments are two-dimensionally arranged. Further, a unit for performing the helical scan a plurality of times as a series of sequences may be further provided.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an X-ray CT according to the present invention.
It is the block diagram which showed the 1st Embodiment of an apparatus. still,
The X-ray CT apparatus 1 of the first embodiment is a case where it has two X-ray beam generation sources.

In the X-ray CT apparatus 1 of the first embodiment, the distance between the two X-ray beam sources is set so that the trajectories of the two X-ray beam sources in the helical scan are spiral orbits at equal intervals. Is to be set. In addition, here, a case where the present invention is applied to a continuous rotation type third generation CT will be described as an example.

As shown in FIG. 1, the X-ray CT apparatus 1 of the first embodiment has a central control unit 3 and a high voltage generator 5.
, Gantry controller 7, X-ray beam generation sources 9-1, 9
-2, the X-ray beam source slide unit 11, the pre-collimator controller 13, the detectors 15-1 and 15-2, the data acquisition units 17-1 and 17-2, and the image reconstruction unit 19
, Image display unit 21, and data storage unit 23
, A bed 25, a bed controller 27, and a tabletop slide controller 29.

In the central control unit 3, the loci of the X-ray beam generation sources 9-1 and 9-2 are mutually determined in the helical scan based on the helical scan condition input by the operator using an input device (not shown). The setting positions of the X-ray beam generation source 9-2 are calculated so that the spiral orbits are evenly spaced, and the X-ray beam irradiation timing is calculated. Further, the central control unit 3 uses the X-ray beam generation source 9-2.
Setting position of X-ray beam source slide control signal,
Based on the inputted helical scan conditions, X
An X-ray beam source slide control signal indicating the set position of the beam source 9-2 and a pre-collimator width control signal indicating the pre-collimator width are output to the gantry controller 7, and the X-ray beam is emitted. The X-ray beam exposure timing control signal indicating the timing is output to the high voltage generator 5, and the data acquisition control signal indicating the data acquisition timing is output to the data acquisition units 17-1 and 17-2. A top slide control signal indicating the amount of movement of the top 25a is output to the bed controller 27.

The high voltage generator 5 supplies a high voltage for electron acceleration and a filament to the X-ray tubes 9a-1 and 9a-2 based on the X-ray beam irradiation timing control signal output from the central control unit 3. Supply heating current. In this case, two X-ray beam sources 9-1 and 9-2 are used as one high voltage generator 5.
However, the high voltage generator 5 may be provided for each of the X-ray beam generation sources 9-1 and 9-2.

The gantry controller 7 outputs the X-ray beam source slide control signal output from the central control unit 3 to the X-ray beam source slide unit 11. Further, the gantry controller 7 outputs the pre-collimator width control signal output from the central control unit 3 to the pre-collimator controller 13. Further, the gantry controller 7 controls the rotation of a rotating unit (not shown) based on the control signal output from the central control unit 3.

The X-ray beam generators 9-1 and 9-2 include X-ray tubes 9a-1 and 9a-2 for irradiating X-rays and X-ray tubes 9a-1 and 9a-2.
And a high voltage for electron acceleration supplied from the high voltage generator 5 having pre-collimators 9b-1 and 9b-2 provided with slit-shaped openings (not shown) provided on the X-ray irradiation side of The X-rays emitted from the X-ray tube 9a by the filament heating current are emitted as fan beams through the pre-collimators 9b-1 and 9b-2.

The X-ray beam source slide unit 11 slides the position of the X-ray beam source 9-2 based on the X-ray beam source slide control signal output from the gantry controller 7. FIGS. 2A and 2B show an example of the X-ray beam source slide unit 11. 2A is a front view of the X-ray beam generation source slide unit 11, and FIG. 2B is a side view thereof.

As shown in FIG. 2, the X-ray beam source slide unit 11 includes an actuator 43 provided on the upper surface of the rotating frame 41, a ball screw shaft 45 connected to the actuator 43, and a rotation of the ball screw shaft 45. The ball screw block 49 moves on the ball screw shaft 45 according to the angle. An X-ray beam generation source 9-2 is installed on the ball screw block 49 via a slide frame 47. Guides 51 are provided on the frame 41 corresponding to both ends of the ball screw shaft 45. The ball screw shaft 45 and the ball screw block 4
9 and the guide 51 are respectively provided on both sides of the precollimator. The rotation of the actuator 43 is performed by rotating the other ball screw shaft 45 through a belt (not shown).
Is transmitted to

Therefore, by rotating the actuator 43, the inside of the guide 51 is moved into the ball screw block 49.
Moves along the ball screw shaft 45, whereby the X-ray beam generation source 9-2 installed on the slide frame 47 on the upper surface of the ball screw block 49 moves. The rotation amount of the actuator 41 is controlled by the X-ray beam source slide controller 53 based on the X-ray beam source slide control signal output from the gantry controller 7. Further, as the actuator 43, a position control servo controller and a motor may be used, or a pulse motor may be used.

The X-ray beam source slide unit 11 is
Any one may be used as long as the X-ray beam emitted from the X-ray beam generation source 9-2 can be moved in the rotation axis direction.
For example, the target and the cathode are moved in the rotation axis direction inside the X-ray beam generation source 9-2. A plurality of targets and cathodes are provided inside the X-ray beam generation source 9-2, and the target and cathode to be used are switched. Further, this switching is combined with the movement of the target and the cathode. Further, the electron beam is swung by the electromagnetic field to move the X-ray beam focal point position. Furthermore, the above is combined.
Etc.

Precollimator controllers 13-1, 13
-2 sets the pre-collimator 9b-1 and 9b-2 to the slit width (pre-collimator width) corresponding to the pre-collimator width control signal based on the pre-collimator width control signal output from the gantry controller 7.

The detectors 15-1 and 15-2 convert the X-rays, which are emitted from the X-ray beam generating sources 9-1 and 9-2 and have passed through the subject, into electric signals. Further, the detector 15-2 has a width capable of detecting the X-ray beam even when the X-ray beam generation source 9-2 is moved by the maximum movement width L as shown in FIG. In FIG. 3,
The installation angle difference in the rotation direction of the X-ray beam generation source 9-2 and the detector 15-2 is shown as 0 for convenience of explanation, but in reality, the installation angle difference must be set so that these do not interfere with each other. I have to.

As the detectors 15-1 and 15-2, as in the case of the single-row detector 100 shown in FIG. 1A, the detectors may be arranged in a line in an arc shape (or a linear shape). As in the two-dimensional detector 110 shown in FIGS. 1A and 1B, a plurality of detector rows may be provided. The two-dimensional detector also includes a detector having two rows of detectors, a flat panel detector having a linear detector row, and an image intensifier (II).

The data collection units 17-1 and 17-2 are connected to the detector 1
The electrical signals converted by 5-1 and 15-2 are collected corresponding to the data collection control signal output from the central control unit 3, and are supplied to the image reconstruction unit 19.

The image reconstructing unit 19 reconstructs the electric signals supplied from the data collecting units 17-1 and 17-2 as image data based on the control signal output from the central control unit 3.

The image display unit 21 includes a monitor (not shown), and the image data reconstructed by the image reconstruction unit 19 is displayed on the monitor based on the control signal output from the central control unit 3. indicate.

The data storage unit 23 includes a memory and a magnetic disk (not shown), and the image reconstruction unit 19
The image data reconstructed by the central control unit 3
The data is stored in the memory or the magnetic disk based on the control signal output from the data storage unit 23.

The bed 25 comprises a top plate 25a which is movable in the direction of the rotation axis and in the vertical direction. A subject is placed on the top surface of the top plate 25a.

The bed controller 27 outputs a control signal for instructing the amount of movement of the tabletop 25a to the tabletop slide portion 29 based on the control signal output from the central control unit 3.

The tabletop slide section 29 moves the tabletop 29a based on the control signal output from the bed controller 27.

The central control unit 3, the image reconstruction unit 19, the image display unit 21, the data storage unit 23 and an input device (not shown) constitute a console 31. The central control unit 3, the image reconstruction unit 19, the image display unit 21, the data storage unit 23 and the input device (not shown) are the system bus 33.
a are connected to each other, and signals can be mutually transmitted and received.

Further, the high voltage generator 5, the gantry controller 7, the X-ray beam source 9, the X-ray beam source slide unit 11, the pre-collimator controller 13, the detector 15-
The 1, 15-2 and the data collecting units 17-1, 17-2 are provided in the gantry 33.

Next, the operation of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to the flowchart shown in FIG. 4 which shows the flow of operation up to the diagnosis start of the central control unit 3.

First, the operator uses the input device (not shown) of the console 31 to input the helical scan conditions.

When the helical scan conditions are input, the central control unit 3 causes the X-ray beam so that the trajectories of the X-ray beam sources 9-1 and 9-2 become helical orbits at equal intervals in the helical scan. The setting position of the source 9-2 is calculated, and the exposure timing of the X-ray beam is calculated (step S1).

Here, in the helical scan, an example of setting the position of the X-ray beam generation source 9-2 so that the trajectories of the X-ray beam generation sources 9-1 and 9-2 are spiral orbits at equal intervals. Will be explained.

When two X-ray beam generators 9-1 and 9-2 are provided, the horizontal axis represents the scan position in the direction of the rotation axis of the subject, and the vertical axis represents the rotation angle of the X-ray beam source or detector. And the X-ray beam source 9 in the helical scan
The trajectories of -1, 9-2 are shown in Fig. 5.

At this time, since the relative position of the X-ray beam generation source 9-1 is fixed, the position of the X-ray beam generation source 9-2 is shown by the locus of the X-ray beam generation source 9-2. 5 is calculated so as to be in the middle of the locus by the X-ray beam generation source 9-1 shown by the solid line. That is, the distance I _{hel1 in the} direction of the rotation axis from the locus of the X-ray beam generation source 9-1 to the locus of the X-ray beam generation source 9-2, and X from the locus of the X-ray beam generation source 9-2.
The position where the distance I _{hel2 in the} direction of the rotation axis to the locus by the line beam source 9-1 is equal is calculated.

For example, the X-ray beam generator 9-2 is provided at a position rotated by 120 degrees with respect to the X-ray beam generator 9-1,
The amount of movement of the top plate 25a in the rotation axis direction is S (m
m), the position x of the X-ray beam generation source 9-2 with respect to the X-ray beam generation source 9-1 is calculated from the equation (1) shown below. x = S / 6 (1)

Further, as shown in FIG. 5, an example of the exposure timing of the X-ray beam when the position of the X-ray beam generation source 9-2 with respect to the X-ray beam generation source 9-1 is set is shown in FIG. 6 (a). ，
(B). In addition, in FIGS. 6A and 6B, the horizontal axis represents time (top moving distance).

FIG. 6A shows an example in which the exposure of the X-ray beam is limited to only the imaging area. That is, since the positions of the X-ray beam generation source 9-1 and the X-ray beam generation source 9-2 in the rotation axis direction are different, the timing of starting and ending the X-ray beam irradiation of the X-ray beam generation source 9-1 is It becomes later than the timing of starting and ending the X-ray beam irradiation of the X-ray beam source 9-2. In this case, since the exposure of the X-ray beam is limited to only the imaging region, it is possible to minimize the exposure dose of the subject.

FIG. 6B shows an example in which X-ray beam irradiation is performed simultaneously with the X-ray beam generation source 9-1 and the X-ray beam generation source 9-2. That is, when one enters the imaging area and the exposure of the X-ray beam is started, the other simultaneously starts the irradiation of the X-ray beam, and until both of them go out of the imaging area, both X-ray beams are emitted. Does not end the exposure of. In this case, FIG.
Although the exposure time of the X-ray beam does not change as compared with the case shown in (a), the amount of exposure increases due to the start and end of exposure of both of them at the same time. However, since both start and end the irradiation at the same time, it becomes easy to control the irradiation timing of the X-ray beam. Incidentally, it takes a predetermined time to stably irradiate the designated X-ray dose, but in the above description, the time until the X-ray beam exposure becomes stable is excluded.

The central control unit 3 generates the X-ray beam which indicates the sliding amount of the X-ray beam source 9 from the helical scan condition input by the operator and the calculated setting position of the X-ray beam source 3. Source slide control signal,
A pre-collimator width control signal indicating the pre-collimator width is output to the gantry controller 7 (step S3). Further, the central control unit 3 outputs an X-ray beam exposure timing control signal indicating the exposure timing to the high voltage generator 5 from the calculated X-ray beam exposure timing (step S5). Further, the central control unit 3 outputs a data collection control signal indicating the timing of data collection to the data collection units 17-1 and 17-2, and outputs a top movement control signal indicating the movement amount of the top 25a to the bed controller 27. (Steps S7 and S9).

When the X-ray beam source slide control signal and the pre-collimator width control signal are output from the central control unit 3, the gantry controller 7 sends the X-ray beam source slide control signal to the X-ray beam source slide section 11. In addition to the output, the pre-collimator width control signal is output to the pre-collimator controllers 13-1 and 13-2. Further, the gantry controller 7 determines the rotation speed of a rotating unit (not shown) according to an instruction from the central control unit 3.

Next, the X-ray beam source slide unit 11
Then, when the X-ray beam source slide control signal is output from the gantry controller 7, based on this, the position of the X-ray beam source 9-2 is set via the X-ray beam source slide controller 53 and the actuator 41. Moving. Incidentally, X
If a weight (not shown) for maintaining weight balance in the rotation axis direction is attached in addition to the X-ray beam generation source 9-2 when moving the radiation beam generation source 9-2, this weight is also simultaneously Try to move.

The pre-collimator controller 13-
When the pre-collimator width control signal is output from the gantry controller 7, the reference numerals 1 and 13-2 set the pre-collimator widths of the pre-collimators 9b-1 and 9b-2, respectively.

When the X-ray beam irradiation timing control signal is output from the central control unit 3, the high voltage generator 5 determines the X-ray beam irradiation timing based on this.

When the data collection control signal is output from the central control unit 3, the data collection units 17-1 and 17-2 collect electrical signals from the detectors 15-1 and 15-2 based on the data collection control signal. Decide when to do it.

On the other hand, when the couch controller 27 outputs the couchtop movement control signal from the central control unit 3, the couchtop slide portion 29 vertically positions the couchtop 25a and the couchtop per one rotation of the rotating section. The movement amount of 25a is set.

When the operator presses a key through the diagnosis using the input device (not shown) of the console 31 (step S11), the central control unit 3 issues a diagnosis start command to the gantry controller 7, the high voltage generator 5, The data is output to the data collecting units 17-1 and 17-2 and the bed controller 27 to start the diagnosis by the helical scan (steps S13 and S15).

When the diagnosis is started, the bed controller 2
7 moves the top plate 25a by the set movement amount. On the other hand, the X-ray beam is emitted from the X-ray beam generation source 9 at a predetermined timing, and the X-rays passing through the subject are converted into electric signals by the detectors 15-1 and 15-2. And
The converted electrical signals are data collection units 17-1, 17-2.
Are collected at a predetermined timing by and are supplied to the image reconstruction unit 19. The image reconstruction unit 19 reconstructs the electric signals supplied from the data collection units 17-1 and 17-2 as image data. The image reconstruction unit 1
9 does not process the electric signals supplied from the data collection units 17-1 and 17-2, but can directly store the electric signals in the memory of the data storage unit 23 via the system bus 33a. The electric signals collected by the data collecting units 17-1 and 17-2 are always supplied to the image reconstruction unit 19, and the electric signals required by the image reconstruction unit 19 are controlled by the control signal from the central control unit 3. Alternatively, the data collection units 17-1 and 17-2 may determine which electric signal to supply to the image reconstruction unit 19 based on a signal from the central control unit 3. You can

Then, the reconstructed image data is displayed on the monitor of the image display unit 21. In addition, the image data is stored in the memory of the data storage unit 23 according to a command from the operator.

Thus, the two X-ray beam sources 9-1,
X so that the locus of 9-2 becomes a spiral orbit at equal intervals.
Helical scanning is performed by setting the distance between the line beam generation sources 9-1 and 9-2.

As described above, in the X-ray CT apparatus 1 according to the first embodiment, the trajectories of the two X-ray beam sources 9-1 and 9-2 are spiral orbits at equal intervals, so that the helical scan is performed. Can be effectively performed, and high-quality image data can be obtained.

In the X-ray CT apparatus 1 of the first embodiment, the case where the X-ray CT apparatus 1 is applied to the continuous rotation type third generation CT has been described as an example, but the present invention is not limited to this, and the continuous rotation type. It is also applicable to the type 4th generation CT. In this case, the cylindrical detector having the inner surface as the detection surface has a width capable of detecting the X-ray beam even if the X-ray beam generation source 9 is moved by the maximum movement width L as in the case shown in FIG. And still,
The movement of the X-ray beam generation source when applied to the continuous rotation type fourth generation CT is performed in the same manner as in the case of the X-ray CT apparatus 1.

Further, the X-ray CT apparatus 1 of the first embodiment has been described by taking the case of having two X-ray beam generation sources 9 as an example, but the present invention is not limited to this, and the X-ray CT source 1 is not limited to this. It can also be applied to the case where there are two or more (n) beam generation sources 9. In this case, (n-1) X-ray beam source slide parts 11 are provided.

FIG. 7 is a block diagram showing a second embodiment of the X-ray CT apparatus according to the present invention. The same components as those shown in FIG. 1 are designated by the same reference numerals and detailed description thereof is omitted. The second embodiment is applied to the continuous rotation type third generation CT.

The X-ray CT apparatus 60 of the second embodiment has two X-ray beam generation sources 9-1,
The distance between the two X-ray beam sources 9-1 and 9-2 and the two detectors 15-1 and 15-2 corresponding to the distance so that the loci by 9-2 are spiral orbits at equal intervals. Is to set the interval. Therefore, as shown in FIG.
In the X-ray CT apparatus 60 according to the second embodiment, a detector slide portion 61 is provided in addition to the X-ray CT apparatus 1 according to the first embodiment shown in FIG.

The detector slide section 61 slides the position of the detector 15-2 based on the detector slide control signal output from the gantry controller 7. The detector slide unit 61 may have the same configuration as the X-ray beam generator slide unit 11 shown in FIGS. 2A and 2B, or the X-ray beam generator 9-2 and the detector 15-. You may comprise so that 2 and may be slid simultaneously.

FIGS. 8A and 8B show an example of the detector slide portion 61 having the same structure as the X-ray beam source slide portion 11. 8A is a front view of the detector slide portion 61, and FIG. 8B is a side view thereof. Also,
The same components as those shown in FIGS. 2A and 2B are designated by the same reference numerals and detailed description thereof is omitted.

As shown in FIGS. 8A and 8B, the detector slide portion 61 is the X-ray beam source slide portion X of the X-ray beam generation source slide portion 11.
A detector slide controller 63 is provided in place of the line beam source slide controller 53. The rotation amount of the actuator 41 is controlled by the detector slide controller 63 based on the detector slide control signal output from the gantry controller 7. The detector slide unit 61 operates similarly to the X-ray beam source slide unit 11.

As described above, in the X-ray CT apparatus 60 of the second embodiment, the relative position of the detector 15-2 to the X-ray beam generation source 9-2 is always constant, so that the same X-ray beam thickness is obtained. If so, the position in the rotation axis direction on the detector 15-2 that receives it is always the same, and image quality deterioration due to the non-uniform sensitivity distribution in the rotation axis direction of the detector 15-2 is less likely to occur.

FIGS. 9A and 9B are views showing an X-ray CT apparatus according to the third embodiment of the present invention. The third embodiment has a detector slide portion 61B configured to simultaneously slide the X-ray beam generation source 9-2 and the detector 15-2. Therefore, it is not necessary to have two actuators for the X-ray beam source 9-2 and the detector 15-2, but only one. Incidentally, FIG. 9A shows the detector slide portion 61B.
FIG. 9 (b) is a side view thereof.

As shown in FIGS. 9 (a) and 9 (b), the detector slide portion 61B has a substantially annular rotating portion base frame 6
5, a substantially annular slide frame 67 that is slidably fixed to the inner surface of the rotating portion base frame 65, and a detector slide controller that slides the slide frame 67 along the inner surface of the rotating portion base frame 65. (Not shown) and.

In the detector slide portion 61B, one X-ray beam generation source 9-1 and the corresponding detector 15-1 are fixed to the rotating portion base frame 65, and the other X-ray beam is attached to the slide frame 67. The source 9-2 and the corresponding detector 15-2 are fixed. Then, the X-ray beam generation source 9-2 and the detector 15-2 together with the slide frame 67 are moved in the rotation axis direction by the detector slide controller. A ball bearing or the like is provided on the surface on which the rotary base frame 65 and the slide frame 67 slide. In addition, the detector slide controller,
Slide frame 6 using an actuator (not shown)
7 is slid along the inner surface of the rotating part base frame 65. This actuator has the same structure as the actuator 41.

When the detector slide portion 61B is used, the X-ray beam generation source 9-2 and the detector 15-2 are moved together with the slide frame 67, so that the detection with respect to the X-ray beam generation source 9-2 is performed. The relative position of the container 15-2 can be maintained with high accuracy.

The detector 15-2 of the third embodiment is
When the X-ray beam generation source 9-2 is moved as shown in FIG. 10, it is moved by the same amount. Therefore, the detector 15-2 of the third embodiment is the same as the detector 15-2 of the first embodiment.
Compared with -2, the width of the axis of rotation can be narrower.

In FIG. 10, the mounting angle difference of the X-ray beam generation source 9-2 and the detector 15-2 in the rotation axis direction is shown as 0 for convenience of explanation, but in reality, these interfere with each other. The mounting angle difference must be set so as not to. Further, when the X-ray beam generation source 9-2 and the detector 15-2 are moved, in addition to the X-ray beam generation source 9-2 and the detector 15-2, a weight (Fig. If attached (not shown), move this weight at the same time.

In the example shown in FIG. 10, two X-ray beam sources 9-1 and 9-2 (two detectors 15-1 and 15-
The case of 2) was explained, but as shown in FIG.
Line beam sources 9-1, 9-2, 9-3 (three detectors 15-
1, 15-2, 15-3) may be used. In this case, if the spiral orbits are evenly spaced, the X-ray beam generation sources 9-1, 9-2, 9
The installation positions of -3 are 120 degrees apart.

Next, a fourth embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus according to the fourth embodiment is the same as the X-ray CT apparatus 1 according to the first embodiment shown in FIG. 1 or the X-ray CT apparatus 60 according to the second embodiment shown in FIG. Since they are the same, their illustration and detailed description are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

In the central control unit 3 of the X-ray CT apparatus according to the fourth embodiment, the total slice thickness of the X-ray beam generation source 9-1 and the X-ray beam generation source 9-2 is one rotation of the rotary unit. The moving amount of the top plate 25a is set to be equal.

At this time, when the operator specifies the slice thicknesses by the X-ray beam generating source 9-1 and the X-ray beam generating source 9-2, the central control unit 3 determines the total slice thickness and the rotation. The amount of movement of the top plate 25a per rotation of the rotating unit is determined so that the amount of movement of the top plate 25a per unit rotation is the same. Also, the top plate 25 per one rotation of the rotating unit
When the movement amount of a is designated by the operator, the central control unit 3 determines the total movement amount of the top plate 25a and the total slice thickness of the X-ray beam source 9-1 and the X-ray beam source 9-2. The slice thickness by the X-ray beam generation source 9-1 and the slice thickness by the X-ray beam generation source 9-2 are determined so that

For example, as shown in FIG. 12, the slice thickness W1 by the X-ray beam generator 9-1 and the X-ray beam generator 9-1
The total amount (W1 + W2) of the slice thickness W2 by -2 is made equal to the movement amount of the top plate 25a per one rotation of the rotary unit.

In the example shown in FIG. 12, the slice thickness W1 by the X-ray beam generator 9-1 and the X-ray beam generator 9-2 are used.
Slice thickness W2 by X, the distance I _{hel1 in} the rotation axis direction from the locus by the X-ray beam source 9-1 to the locus by the X-ray beam source 9-2, and X by the locus by the X-ray beam source 9-2. All the distances I _{hel2 in the} direction of the rotation axis to the locus by the line beam source 9-1 _should be equal (W1 = W2 =
I _hel1 = I _hel2 ), the central control unit 3 determines the distance between the X-ray beam source 9-1 and the X-ray beam source 9-2 and the slice thicknesses W 1 and W 2.

As described above, in the X-ray CT apparatus according to the fourth embodiment, the X-ray beam generation source 9-1 and the X-ray beam generation source 9 are used.
Since the total slice thickness of -2 is set to be equal to the movement amount of the top plate 25a per one rotation of the rotating unit, it is possible to scan the imaging region without omission with the minimum exposure.

Next, a fifth embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus of the fifth embodiment is the same as that of the X-ray CT apparatus 1 of the first embodiment shown in FIG. 1 or the X-ray CT apparatus 60 of the second embodiment shown in FIG. Since only the numbers of the X-ray beam generation sources 9 and the detectors 17 are different, illustration and detailed description are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

In the X-ray CT apparatus of the fifth embodiment, three X-ray beam sources 9-1, 9-2, 9-3 are provided at 120 ° intervals, and three detectors are correspondingly provided. It is provided. The X-ray beam generation source 9-3 is fixed to the rotating part, and the X-ray beam generation sources 9-1 and 9-2 are moved in the rotation axis direction by the corresponding X-ray beam generation slide parts 11. It is possible. Further, here, a single-row detector is used as the detector.

As shown in FIG. 12, X of the fifth embodiment
In the X-ray CT system, three X-ray beam sources 9-1, 9-2,
The setting positions of 9-3 are set on the same midplane, that is, on the same plane. Note that, in FIG. 12, the X-ray beam generation source indicated by the dotted line indicates the setting position during conventional scanning.

In this case, the distance I _{hel1 in the} direction of the rotation axis from the locus of the X-ray beam generation source 9-1 to the locus of the X-ray beam generation source 9-2 and the locus of the X-ray beam generation source 9-2 to X The distance I _{hel2 in the} direction of the rotation axis to the trajectory of the X-ray beam generator 9-3 and the X from the trajectory of the X-ray beam generator 9-3
The distance I _hel3 in the direction of the rotation axis to the locus by the line beam source 9-1 becomes equal.

Further, the X-ray beam generators 9-1 and 9 are shown in FIG.
-The exposure timing of the X-ray beam emitted from 9-3 is shown. Since the setting positions of the three X-ray beam sources 9-1, 9-2, 9-3 are on the same midplane, the X-ray beam sources 9-1, 9-2, 9-3 irradiate As shown in FIG. 14, the X-ray beam irradiation timings are the same for all three.

As described above, in the X-ray CT apparatus of the fifth embodiment, the three X-ray beam generation sources 9-1, 9-2, 9-3 are set to one.
The X-ray beam generation source 9-is provided at intervals of 20 degrees.
Since the setting positions of 1, 9-2 and 9-3 are on the same midplane, the X-ray beam irradiation timing can be easily controlled.

In the X-ray CT apparatus of the fifth embodiment,
Helical scanning is performed using all three X-ray beam sources 9-1, 9-2, 9-3.
It is also possible to perform the helical scan by using two or only one of -1, 9-2 and 9-3. For example, when performing a helical scan using the X-ray beam generators 9-1 and 9-2, the X-ray beam generators 9-1 and the X-ray beam generators 9-1 and X-2 are arranged so that the trajectories of the two helical scans are at equal intervals. This can be realized by setting the distance in the direction of the rotation axis from the line beam generation source 9-2.

The combination of the X-ray beam generation source 9-1 and the X-ray beam generation source 9-2 is not limited to the combination of the X-ray beam generation source 9-2, the X-ray beam generation source 9-3, and the X-ray beam generation source. The source 9-1 and the X-ray beam source 9-3 may be used. When the X-ray beam generating source 9-1 and the X-ray beam generating source 9-2 are used, if the two moving amounts are averaged and made equal, the X-ray beam generating sources 9-1, 9 -Travel time of 2 can be shortened.

Although the X-ray CT apparatus of the fifth embodiment uses a single-row detector as a detector, the present invention is not limited to this, and as shown in FIG. 15, a double-row detector is used. The detectors 15-1, 15-2, 15-3 may be used. Also in this case, the setting positions of the three X-ray beam generation sources 9-1, 9-2, 9-3 are set on the same midplane, that is, on the same plane. Incidentally, in FIG. 15, the X-ray beam generation source indicated by the dotted line indicates the setting position during conventional scanning.

In this case, the distance I _{hel11 in the} direction of the rotation axis of the locus of the two detector rows 15-1A and 15-1B of the detector 15-1 and the detector row 15-1B of the detector 15-1. by a detector of the rotation axis direction of the by column 15-2A to trace interval I _{Hel1 2} detector 15-2 from the trajectory, the two detector rows 15-2A detectors 15-2 trajectory by 15-2B a rotation axis direction of the spacing _I hel21, the detector 15-2 of the detector row detector rotation axis direction of the spacing I _Hel22 of by column 15-3A to the locus of the detector 15-3 from the trajectory by 15-2B, detection two detector rows 15-3A vessels 15-3, the rotation axis direction of the spacing I _{he l31} trajectory by 15-3B, detector row 15-3 of the detector 15-3
The distance I _{hel32 in} the rotation axis direction from the locus of B to the locus of the detector array 15-1A of the detector 15-1 is made equal.

Also in this case, since the setting positions of the three X-ray beam sources 9-1, 9-2, 9-3 are on the same midplane, the X-ray beam sources 9-1, 9- The X-ray beam irradiation timings irradiated from 2, 9-3 are all three at the same time as in the case shown in FIG.

Further, the detectors 15-1, 15-2, and 15-3 can be applied to the case of a detector having three or more rows, and to the case of other types of two-dimensional detectors. Can also be applied. In this case, it is not necessary to use all the existing detector rows, and for example, only one detector row may be used to realize helical scan loci at equal intervals. In the case of a detector having three or more detector rows, only some of the rows may be used to realize helical scan loci at equal intervals. Further, some detectors may be used to realize helical scan loci evenly spaced from each other. Furthermore, the use of some detectors and the use of some detector rows may be combined to realize helical scan trajectories at equal intervals.

Next, a sixth embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus according to the sixth embodiment is the same as the X-ray CT apparatus 1 according to the first embodiment shown in FIG. 1 or the X-ray CT apparatus 60 according to the second embodiment shown in FIG. Since only the numbers of the X-ray beam generation sources 9 and the detectors 17 are different, illustration and detailed description are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

The X-ray CT apparatus of the sixth embodiment performs helical scanning with one X-ray beam generation source and a detector corresponding thereto for each predetermined area. Here, as shown in FIG. 16, three X-ray beam generators 9-
1, 9-2, 9-3 are provided at intervals of 120 degrees, and three detectors 15-1, 15-2, 15-3 are provided correspondingly, and the imaging area is divided into three areas for each area. A case of performing a helical scan will be described as an example.

In the example shown in FIG. 16, the X-ray beam generation source 9
-1 helically scans the area a1, the X-ray beam generator 9-2 helically scans the area a2, and the X-ray beam generator 9-3 helically scans the area a3.

In this case, each area (area a
1, the area a2, and the area a3) do not have to be the same in size, but they are the same, and the intervals between the start points of the areas are the same as those of the X-ray beam generators 9-1, 9-2, 9-3. When set to be equal to the interval, the X-ray beam irradiation timings are the same as shown in FIG. 17, and the X-ray beam irradiation timings can be easily controlled.

In the X-ray CT apparatus of the sixth embodiment, the maximum X-ray beam source spacing in the direction of the rotation axis that can be set is I.
If max is set, the total imaging area of the helical scan is I
It is applicable when it is smaller than max * (the number of X-ray beam sources).

As described above, in the X-ray CT apparatus according to the sixth embodiment, one X-ray beam generation source and a detector corresponding to each area are used to perform the helical scan. Therefore, it is possible to prevent deterioration of image quality caused by a difference in sensitivity between detectors without using a plurality of detectors.

Incidentally, in the X-ray CT apparatus of the sixth embodiment,
Although the X-ray beams are simultaneously emitted from the X-ray beam generation sources 9-1, 9-2, 9-3, as shown in FIG.
By shifting the irradiation timing of the line beam, a wider area can be helically scanned.

In this case, as shown in FIG. 19, first, the X-ray beam generation source 9-1 starts irradiation of the X-ray beam. Next, when the scan position corresponding to the X-ray beam generation source 9-2 approaches the area a2, the X-ray beam generation source 9-2 also starts the X-ray beam irradiation. Similarly, the X-ray beam source 9-3
Also starts irradiation of the X-ray beam at the start point of the region a3. After that, the X-ray beam generation source 9-1 ends the irradiation of the X-ray beam when the scan position passes the end point of the area a1. Similarly, the X-ray beam generators 9-2 and 9-3 also terminate the exposure of the X-ray beam at the end points of the respective regions a2 and a3.

In this case, if the maximum X-ray beam source spacing in the direction of the rotation axis that can be set is Imax, the total imaging area of the helical scan is larger than Imax * (the number of X-ray beam sources). It is generally applied to.

Further, in the X-ray CT apparatus of the sixth embodiment, helical scanning is performed using all three X-ray beam sources 9-1, 9-2, 9-3, but three X-ray beams are used. It is also possible to use two or only one of the sources 9-1, 9-2 and 9-3 to perform the helical scan. For example X
FIG. 20 shows a case where helical scanning is performed using the line beam generation sources 9-1 and 9-2.

As shown in FIG. 20, the photographing area is divided into two areas, and a helical scan is performed for each area. That is, the X-ray beam generation source 9-1 scans the area a1 and the X-ray beam generation source 9-2 scans the area a2. At this time, the sizes of the areas (area a1 and area a2) do not necessarily have to be the same, but they are the same and the intervals between the start points of the areas are set to the X-ray beam generation sources 9-1 and 9-2. When the interval is set to be equal to, the X-ray beam irradiation timings are the same as shown in FIG. 21, and the X-ray beam irradiation timings can be easily controlled. Further, when the X-ray beam generation source 9-1 and the X-ray beam generation source 9-2 are used, if the two movement amounts are averaged to be equal, the X-ray beam generation source 9-
The travel time of 1, 9-2 can be shortened.

Furthermore, in the X-ray CT apparatus of the sixth embodiment, a single-row detector is used as the detector, but the present invention is not limited to this, and as shown in FIG. The column detectors 15-1, 15-2, 15-3 may be used. In this case, the imaging region is divided into three, and the helical scan is performed for each region. That is, the X-ray beam generator 9-1 performs a helical scan on the area a1, the X-ray beam generator 9-2 on the area a2, and the X-ray beam generator 9-3 on the area a3.

In this case, each area (area a
1, the area a2, and the area a3) do not have to be the same in size, but they are the same, and the intervals between the start points of the areas are the same as those of the X-ray beam generators 9-1, 9-2, 9-3. When set to be equal to the interval, the X-ray beam irradiation timings are the same as shown in FIG. 23, and the X-ray beam irradiation timings can be easily controlled.

Furthermore, the X-ray CT apparatus according to the sixth embodiment can be applied to the case where three or more rows of detectors are used as the detector, and another type of two-dimensional detector is used. It can also be applied in cases.

Next, FIG. 24 shows an example of a method of setting the number of areas with respect to the imaging area width and the X-ray beam irradiation timing when the X-ray CT apparatus of the sixth embodiment is used. Here, the maximum settable interval between the X-ray beam generation sources in the rotation axis direction is Imax, and the case is divided into four cases according to the imaging region width designated by the operator.

When the imaging region ≦ Imax (C1YES), the number of regions is set to 1, and one X-ray beam generator (X-ray beam generator 9-1, X-ray beam generator 9-2 or X-ray beam generator) is used. Perform a helical scan using 9-3).

When Imax ≦ shooting area <3 * Imax (C
1NO, C3YES), the number of areas is 2, and the size of each area is imaging area / 2. Two X-ray beam sources (X-ray beam source 9-1 and X-ray beam source 9-2, X-ray beam source 9-2 and X-ray beam source 9-3 or X-ray beam source 9 -3 and an X-ray beam source 9-1) are used to perform a helical scan. The X-ray beam irradiation timings of the two X-ray beam generation sources are the same.

When 2 * Imax ≦ photographing region <3 * Imax (C3NO, C5YES), the number of regions is 3, and the size of each region is photographing region / 3. Helical scanning is performed using three X-ray beam generation sources (X-ray beam generation source 9-1, X-ray beam generation source 9-2 and X-ray beam generation source 9-3). The X-ray beam irradiation timings of the three X-ray beam generation sources are the same.

When 3 * Imax <shooting area (C5 NO),
The number of areas is 3, and the size of each area is
3 is assumed. Three X-ray beam sources (X-ray beam source 9-1, X-ray beam source 9-2 and X-ray beam source 9-3)
Perform a helical scan using. By shifting the X-ray beam irradiation timing from each X-ray beam generation source, a helical scan of a wider area than in the case of 2 * Imax ≦ imaging area <3 * Imax is performed.

In this way, the number of regions and the X-ray beam exposure timing are determined in four cases based on the imaging region width designated by the operator.

Next, a seventh embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus according to the seventh embodiment is the same as that of the X-ray CT apparatus 1 according to the first embodiment shown in FIG. 1 or the X-ray CT apparatus 60 according to the second embodiment shown in FIG. Since only the numbers of the X-ray beam generation sources 9 and the detectors 17 are different, illustration and detailed description are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

The X-ray CT apparatus of the seventh embodiment is such that a plurality of regions having different helical scan conditions are helically scanned by a series of operations.

For example, a helical scan condition as shown in FIG. 25 is set for each photographing area. At this time, the rotation of the imaging area is designated on the scanograph image, and the area width, the number of X-ray beam sources used, the slice thickness, the top plate feed per rotation, the X-ray tube voltage, the X-axis, and the X-ray tube voltage are set for each imaging area. Enter the tube current.
When the number of used X-ray beam generation sources is automatic, the scanning method is determined based on the example shown in FIG.

Here, as shown in FIG. 26, three X
The line beam sources 9-1, 9-2, 9-3 are provided at 120 ° intervals, and three detectors 15-1, 15 are provided correspondingly.
An example will be described in which -2 and 15-3 are provided and a plurality of areas having different top plate feeds per rotation are scanned.

In the example shown in FIG. 26, the photographing areas a1 and a2 having different photographing conditions are divided into three areas, and a helical scan is performed for each of these areas. That is, the X-ray beam generation source 9-1 includes the regions a11 and a21, and the X-ray beam generation source 9-1.
-2 helically scans the regions a12 and a22, and the X-ray beam generator 9-3 helically scans the regions a13 and a23. The difference between the photographing conditions in the photographing regions a1 and a2 is that the top feed per rotation is different. Further, the interval between the X-ray beam generation sources is changed on the way. The X-ray beam irradiation is performed only on the corresponding area.

Here, both the photographing area a1 and the photographing area a2 (areas 11, 12, 13 and areas 21, 2).
FIG. 27 shows the X-ray beam irradiation timing in the case where the distance between the starting points of (2, 23) is made equal to the distance between the X-ray beam generation sources and the sizes of the regions are made equal to each other.

The top speed is changed between the time when the photographing of the photographing area a1 is finished and the time when the photographing of the photographing area a2 is started. During the change of the top speed,
X-ray beam exposure is stopped. Further, the intervals of the X-ray beam generation sources 9-1, 9-2, 9-3 are also changed during this time. In other words, after the imaging area a1 is finished, the X-ray beam generation is performed so that the X-ray beam generation sources 9-1, 9-2, 9-3 are located at the start points of the areas a21, a22, and a23 of the imaging area a2. Source 9
The intervals of -1, 9-2, 9-3 are set, and the helical scan of the imaging area a2 is performed again.

In this case, the two imaging areas a1 and a2 having different top plate feeds per rotation are helically scanned by a series of operations, and the interval between the X-ray beam generating sources is changed on the way. Diagnostic efficiency is improved.

Next, FIG. 28 shows an example including a case where the width of the imaging area a1 is larger than the maximum X-ray beam generation source interval Imax * (the number of X-ray beam generation sources). In this example, the shooting area a1
Then, by shifting the X-ray beam irradiation timings as shown in FIG. 29, a helical scan of a wider area is enabled.

In this case, in addition to the example shown in FIG. 26, the present invention can be applied even when it is larger than the maximum X-ray beam generation source interval Imax * (the number of X-ray beam generation sources).

Next, the top plate feed per rotation is the same,
FIG. 29 shows the case where other conditions are different. In this example, three X-ray beam sources 9-1 and 9 are used for the imaging area a2.
A part of -2 and 9-3 (X-ray beam generation source 9-1 and X-ray beam generation source 9-2) is used for helical scanning. In the example shown in FIG. 30, since the intervals between the X-ray beam sources 9-1, 9-2, 9-3 are not changed on the way, the X-ray beam irradiation timing is set as shown in FIG. By adjusting, the width of the region to be diagnosed is changed.

In this case, the X-ray beam generators 9-1, 9-2,
Since the 9-3 interval is not changed on the way, X
The movement control of the line beam sources 9-1, 9-2, 9-3 is simplified.

As described above, in the X-ray CT apparatus according to the seventh embodiment, a plurality of regions having different helical scan conditions are helically scanned by a series of operations.
Diagnostic efficiency is improved.

Incidentally, in the X-ray CT apparatus of the seventh embodiment,
The case where the imaging regions are adjacent to each other has been described as an example, but the present invention can be applied even when the imaging regions are not adjacent to each other. It can also be applied when a two-dimensional detector is used as the detector.

Next, an eighth embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus according to the eighth embodiment is the same as the X-ray CT apparatus 1 according to the first embodiment shown in FIG. 1 or the X-ray CT apparatus 60 according to the second embodiment shown in FIG. Since they have the same configuration, illustration and detailed description thereof are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

In order to reconstruct the image data at a predetermined position, it is necessary to interpolate the image data. If it is 360 degree interpolation, it is 360 degrees centered on the reconstructed position, and if it is the counter beam interpolation, it is reconstructed. Image data corresponding to (180 degrees + fan angle of X-ray beam / 2) is required around the constituent position.

When a helical scan is performed with one X-ray beam generation source and a detector corresponding thereto for each adjacent predetermined region, in the vicinity of the boundary portion, one X-ray beam generation source corresponds to one as described above. Since some parts cannot be reconstructed with only the image data, it is necessary to reconstruct using the image data of both areas. However, when helical scanning is performed with one X-ray beam generation source and a detector corresponding thereto for each region, the spiral orbit corresponding to the X-ray beam generation source also differs for different regions, so image quality deterioration such as artifacts occurs. There is a problem that it is easy to cause. In order to prevent the image quality deterioration at the area boundary portion, in the eighth embodiment, the areas are overlapped from each other by a predetermined amount.

FIG. 3 shows a helical scan locus in the case where a helical scan is performed by overlapping the boundaries of the regions.
It is shown in FIG. In this example, the top plate feed per rotation is area a.
1 and the area a2 are equal, and the area to be overlapped (hereinafter referred to as an overlap area) O
1 and O2 are each one rotation from the boundary. The overlapping areas O1 and O2 are (180 degrees +
It may be a fan angle of the X-ray beam / 2). Also,
Even when the top plate feed per rotation is not equal in the areas a1 and a2, the overlapping areas O1 and O2 are each one rotation or (180 degrees + X-ray beam fan angle / 2).

As described above, in the X-ray CT apparatus according to the eighth embodiment, the regions are overlapped by a predetermined amount, so that the image data at any position can be reconstructed by one X-ray. The image data can be reconstructed only by the image data corresponding to the beam generation source.

Incidentally, in the X-ray CT apparatus of the eighth embodiment,
The case where the single-row detector is used as the detector has been described as an example, but the present invention is not limited to this, and can be applied to the case where a two-dimensional detector is used, for example.

FIG. 33 shows a helical scan locus in the case where a two-row detector is used as the detector and the helical scanning is performed by overlapping the boundary portion of the regions. As shown in FIG. 33, in the case of using the two-dimensional detectors 15-1 and 15-2, from the state where the scan position of the detector row closest to the adjacent area is on the boundary, the direction of the adjacent area is further increased. Make one rotation or 180 degrees plus the fan angle overlap. In the example shown in FIG. 33, the top plate feed per rotation is the same in both the areas a1 and a2,
The overlap areas O1 and O2 are each 1 from the boundary.
It is a rotation. The overlap areas O1 and O2 are
Each may be 180 degrees plus the fan angle of the X-ray beam. Also, when the top feed per rotation is not equal in the areas a1 and a2, the overlap area O1,
O2 is equivalent to one rotation or 180 degrees plus X
It is the fan angle of the line beam.

Next, a ninth embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus of the ninth embodiment is the same as that of the X-ray CT apparatus 1 of the first embodiment shown in FIG. 1 or the X-ray CT apparatus 60 of the second embodiment shown in FIG. Since only the numbers of the X-ray beam generation sources 9 and the detectors 17 are different, illustration and detailed description are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

In the ninth embodiment, in order to prevent the image quality from deteriorating at the area boundary portion, the helical scan loci corresponding to the respective X-ray beam sources used for imaging are placed on the same spiral orbit. The distance between the X-ray beam generation sources in the rotation axis direction is set.

When three X-ray beam generators are provided at every 120 degrees, the intervals of the X-ray beam generators in the rotation axis direction are set so that the spiral trajectories drawn by the X-ray beam generators are on the same spiral trajectory. FIG. 34 shows a helical scan locus when performing a helical scan with the setting of. In addition, in order to put them on the same spiral orbit in the previous period, it is necessary that the top plate feed per rotation is the same and the regions are adjacent to each other.

When the X-ray beam generation source is provided at an angle of 120 degrees, the area width is set to the area width = (integer + 1/3) rotation, which is shown in FIG. As described above, the helical scan loci corresponding to the respective X-ray beam generation sources can be placed on the same spiral orbit. The region width differs depending on the number of X-ray beam generators used and the mounting angle thereof. FIG.
In the example shown in, each area width is a top plate feed distance equivalent to 5 and 1/3 rotation.

As described above, the X-ray CT apparatus according to the ninth embodiment can obtain image data of one continuous spiral trajectory,
Artifacts and image discontinuities due to different spiral trajectories can be eliminated. In this case, it is also possible to interpolate and reconstruct the data of the mutual areas without overlapping as in the eighth embodiment.

In the X-ray CT apparatus of the ninth embodiment,
The case where the single-row detector is used as the detector has been described as an example, but the present invention is not limited to this, and can be applied to the case where a two-dimensional detector is used, for example.

In the case of having three X-ray beam generators for every 120 degrees and two row detectors corresponding to the respective X-ray beam generators, the spiral trajectories drawn by the X-ray beam generators have the same spiral orbit. FIG. 35 shows a helical scan locus when a helical scan is performed by setting an interval in the rotation axis direction of the X-ray beam generation source so as to follow the orbit.

As shown in FIG. 35, the two-row detector 15-1,
With 15-2 and 15-3, image data on two continuous spiral trajectories are obtained. Further, in the case of having three or more detector rows, the same number of image data on spiral trajectories as the number of detector rows can be obtained. Furthermore, in the case of a helical scan using a detector row as a part of the two-dimensional detector, the same number of image data on the spiral orbit as the number of rows used is obtained.

Next, the tenth X-ray CT apparatus according to the present invention will be described.
An embodiment will be described. The X-ray C of the tenth embodiment
The configuration of the T apparatus is the X-ray C of the first embodiment shown in FIG.
T apparatus 1 or X-ray C of the second embodiment shown in FIG.
Since it has the same configuration as the T device 60, its illustration and detailed description are omitted. Also, here, the same members as those shown in FIGS. 1 and 7 will be described using the same symbols.

In the tenth embodiment, as shown in FIG. 36, in order to prevent the image quality from deteriorating at the area boundary portion, the spiral scan loci corresponding to the respective X-ray beam generation sources used for imaging have the same spiral. A part of the image data of the overlap region is wholly or completely set by setting the interval of the X-ray beam generation source in the direction of the rotation axis so as to be on the orbit, and performing the helical scan by overlapping the boundary part of the region. The weighting as shown in FIG. 37 is performed.

As shown in FIG. 37, the weighting on the side of the area a1 is linear such that the boundary between the area a1 and the overlap area is "1" and the boundary between the overlap area and the area a2 is "0". The weighting on the side of the area a2 is linear such that the boundary between the area a2 and the overlap area has a weight of "1" and the boundary between the overlap area and the area a1 has a weight of "0". Then, in the overlap area, the arithmetic mean of the weighted image data is used as the image data at that position. Note that this weighting does not necessarily have to be linear. In this case, it goes without saying that the arithmetic mean of the data is the data after correction and logarithmic conversion.

Thus, the X-ray CT of the tenth embodiment
The apparatus sets the intervals of the X-ray beam sources in the rotation axis direction so that the helical scan loci corresponding to the X-ray beam sources used for imaging lie on the same spiral orbit, and the boundary of the region. The parts are overlapped and helical scan is performed, and part or all of the image data in the overlap area is weighted as shown in FIG. 37. Therefore, in the overlap area, addition of the weighted image data is performed. By using the average as the image data at that position, it is possible to prevent image quality deterioration at the region boundary portion.

[0156]

As described above, according to the present invention, since the setting means for setting the interval of the X-ray beam generation source in the rotation axis direction is used, the helical scan can be effectively performed. Therefore, it becomes possible to obtain high-quality image data.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an X-ray CT apparatus according to the present invention.

FIG. 2 is a diagram showing an example of an X-ray beam generation source slide unit shown in FIG.

FIG. 3 is a diagram showing the detector shown in FIG. 1.

FIG. 4 is a flowchart showing a flow of operations of the central control unit shown in FIG. 1 up to the start of diagnosis.

FIG. 5 is a diagram showing a helical scan locus in the case of having two X-ray beam generation sources in the first embodiment.

FIG. 6 is a diagram showing X-ray beam irradiation timings when X-ray beam irradiation is performed only in the imaging region and (a) when two X-ray beam irradiation sources are simultaneously used. Is.

FIG. 7 is a block diagram showing a second embodiment of an X-ray CT apparatus according to the present invention.

8 is a diagram showing an example of an X-ray beam source slide unit shown in FIG.

FIG. 9 is a diagram showing a third embodiment of the X-ray CT apparatus according to the present invention, showing a detector configured to simultaneously slide an X-ray beam generation source and a detector.

10 is a diagram showing the detector shown in FIG. 7. FIG.

FIG. 11 is a diagram showing an example in which there are three X-ray beam generation sources.

FIG. 12 is a diagram for explaining the fourth embodiment of the X-ray CT apparatus according to the present invention.

FIG. 13 is a diagram for explaining the fifth embodiment of the X-ray CT apparatus according to the present invention.

FIG. 14 is a diagram showing an X-ray beam emission timing in the case shown in FIG.

FIG. 15 is a diagram showing a case where the example shown in FIG. 13 is applied to a two-row detector.

FIG. 16 is a diagram for explaining the sixth embodiment of the X-ray CT apparatus according to the present invention.

FIG. 17 is a diagram showing an X-ray beam emission timing in the case shown in FIG. 16.

FIG. 18 is a diagram showing a case where X-ray beam irradiation timings of three X-ray beam generation sources are shifted.

FIG. 19 is a diagram showing a helical scan locus in the case of having three X-ray beam generation sources.

FIG. 20 is a diagram showing a helical scan trajectory when only two of the three X-ray beam sources are used.

FIG. 21 is a diagram showing X-ray beam emission timing in the case shown in FIG. 20.

22 is a diagram showing a locus by a helical scan when the detector shown in FIG. 16 is replaced with a two-row detector.

FIG. 23 is a diagram showing X-ray beam emission timing in the case shown in FIG. 22.

FIG. 24 is a diagram showing an example of a method of setting the number of areas with respect to the imaging area width and an X-ray beam exposure timing when the X-ray CT apparatus according to the sixth embodiment is used.

FIG. 25 is a diagram showing an example of helical scan conditions for each imaging region.

FIG. 26 is a diagram for explaining the seventh embodiment of the X-ray CT apparatus according to the present invention.

FIG. 27 is a diagram showing X-ray beam emission timing in the case shown in FIG. 26.

FIG. 28 is a width of an imaging region in the seventh embodiment, the maximum interval Imax * of X-ray beam generation sources (number of X-ray beam generation sources).
It is a figure for demonstrating the time including a larger case.

FIG. 29 is a diagram showing an X-ray beam emission timing in the case shown in FIG. 28.

FIG. 30 is a diagram for explaining a case where the top plate feed per rotation is the same and the other conditions are different in the seventh embodiment.

31 is a diagram showing X-ray beam emission timing in the case shown in FIG. 30. FIG.

FIG. 32 is a view for explaining the eighth embodiment of the X-ray CT apparatus according to the present invention.

FIG. 33 is a diagram when the detector shown in FIG. 32 is replaced with a two-row detector.

FIG. 34 is a view for explaining the ninth embodiment of the X-ray CT apparatus according to the present invention.

FIG. 35 is a diagram when the detector shown in FIG. 34 is replaced with a two-row detector.

FIG. 36 is a view for explaining the tenth embodiment of the X-ray CT apparatus according to the present invention.

FIG. 37 is a diagram showing an example of weighting in the case shown in FIG. 36.

FIG. 38 is a diagram showing an example of a single-row detector and a two-dimensional detector.

FIG. 39 is a diagram showing an example of a continuous rotation type fourth generation CT.

FIG. 40 is a diagram showing a helical scan locus in an X-ray CT apparatus having a single-row detector.

FIG. 41 is a diagram showing a helical scan locus in an X-ray CT apparatus having a three-row detector.

FIG. 42 is a diagram for explaining conventional scanning in the case of having two X-ray beam generation sources.

FIG. 43 is a diagram showing a helical scan locus when a helical scan is performed with an X-ray beam generation source set to a conventional scan.

FIG. 44 is a diagram showing a helical scan locus when a helical scan is performed with an X-ray beam generation source set to a conventional scan and the slice thickness is taken into consideration.

FIG. 45 is a diagram for explaining conventional scanning in the case of having three X-ray beam generation sources.

FIG. 46 is a diagram showing a helical scan locus in a case where a helical scan is performed with the X-ray beam generation source having three X-ray beam generation sources set in the conventional scan mode.

[Explanation of symbols]

 1 X-ray CT apparatus 3 Central control unit 5 High voltage generator 7 Stand controller 9 X-ray beam source 11 X-ray beam source slide section 13 Pre-collimator controller 15 Detector 17 Data acquisition section 19 Image reconstruction unit 21 Image display Unit 23 Data storage unit 25 Bed 27 Bed controller 29 Top slide controller 31 Console 33 Frame

Claims (14)

[Claims] 1. A plurality of X-ray beam generators for irradiating a subject on a bed with X-rays, a detector for detecting X-rays emitted from the X-ray beam generators, and the plurality of X's. The at least two X-ray generation sources, comprising: a rotation unit that rotates the X-ray beam generation source around the subject; and a setting unit that sets an interval between the plurality of X-ray beam generation sources in the rotation axis direction. An X-ray CT apparatus characterized by rotating the bed and moving the bed in the rotation axis direction to perform a helical scan. 2. The rotating shafts of the plurality of X-ray beam generating sources are set so that the spiral orbits of the at least two X-ray beam generating sources used for helical scanning by the helical scanning are at equal intervals. The X-ray CT apparatus according to claim 1, wherein an interval between directions is set. 3. The setting means divides an area in the rotation axis direction for helical scanning into a plurality of areas, and one X-ray beam generation source and its corresponding detector perform helical scanning for each area. The X-ray CT apparatus according to claim 1, further comprising: setting at least two intervals of the X-ray beam generation sources used for helical scanning in a rotation axis direction. 4. The setting means sets the number of the areas to the X
The number of X-ray beam generators is the same as the number of X-ray beam generators, and the intervals between the plurality of X-ray beam generators in the direction of the rotation axis are such that helical scanning is performed by a detector corresponding to one X-ray beam generator for each region. 4. The method according to claim 3, wherein
The described X-ray CT apparatus. 5. The setting means sets an interval in the rotation axis direction of at least two of the X-ray beam generation sources used for the helical scan so that a helical scan is performed by overlapping the boundaries of the regions. The X-ray CT apparatus according to claim 3, wherein: 6. The X-ray according to claim 5, wherein, for at least a part of the overlapped portion of the data collected by the detector, arithmetic averaging with linear weighting is performed. CT device. 7. The at least two X-ray beam generators so that at least a part of the spiral orbits of the helical scans of the at least two X-ray beam generators used for the helical scan are the same spiral orbit. The X-ray CT apparatus according to claim 3 or 5, wherein an interval in the direction of the rotation axis is set. 8. The X-ray generation source according to claim 3, wherein the X-ray beam generation source is controlled in its irradiation timing so as to irradiate the X-ray only to a region for helical scanning. CT device. 9. The X according to claim 1, wherein the detector is rotated by the rotating means in synchronization with a corresponding X-ray beam source.
Line CT device. 10. The detector according to claim 1, wherein the detector has a cylindrical shape having an inner surface as a detection surface.
The X-ray CT apparatus according to any one of 1. 11. The setting means moves the X-ray beam generation source and the corresponding detector by the same amount as the X-ray beam generation source in the rotation axis direction. X-ray CT apparatus according to any one of 1. 12. The setting means fixes the X-ray beam generation source and a detector corresponding thereto on the same fixing member, and moves the X-ray beam generation source and the detector together with the fixing member. The X-ray CT apparatus according to claim 11, wherein: 13. The X-ray CT apparatus according to claim 9, wherein the detector is a two-dimensional detector in which detection segments are two-dimensionally arranged. 14. The X-ray C according to claim 1, further comprising means for performing the helical scan a plurality of times as a series of sequences.
T device.