JP2825446B2 - X-ray computed tomography device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray computed tomography apparatus for reconstructing a tomographic image from all-angle projection data of a section of a subject.

[0002]

2. Description of the Related Art In an X-ray computed tomography apparatus, from the beginning of development, improvement of image quality and reduction of scan time have been raised as one of the important problems. A helical scan (hereinafter referred to as a helical scan), which solves this problem epoch-making, consists of a motion in which the rotating gantry continuously rotates around the subject, and a technique in which the subject is parallel to the rotation axis of the rotating gantry. Is achieved in combination with a movement that moves continuously along. In this helical scan, when the subject is a fixed system, the X-ray source moves helically along the body axis of the subject.

The helical scan has the following problems. In the helical scan, the rotation angle (hereinafter simply referred to as an angle) of a rotating gantry at the time of acquisition periodically changes, and a slice axis (hereinafter referred to as a Z axis) parallel to the body axis of the subject.
The collection position (hereinafter, referred to as Z position) changes continuously along. When reconstructing one tomographic image of a cross section using the projection data collected at each position on such a spiral orbit, the projection data at this cross section position is reconstructed before and after the Z position of this cross section position. It is necessary to create the two projection data by distance interpolation. There are two methods for this distance interpolation. One is called a simple interpolation method, and the other is called a counter beam interpolation method.

In the simple interpolation method, projection data for two rotations about the position of the reconstruction section is required. The projection data for two rotations is distance-interpolated to the projection data for one rotation. Distance interpolation is the same angle and two different Z positions.
This is a process of weighting and averaging two data according to the distance from the cross-sectional position. From the projection data (weighted average data) for one rotation thus obtained, a tomographic image of the cross section is reconstructed.

As described above, in the helical scan, all-angle projection data necessary for reconstructing a single tomographic image is calculated based on the distance that the subject (top) moves while the rotating gantry rotates twice. Since the area is scattered, that is, the effective slice thickness is large, the reliability of the tomographic image has to be reduced.

[0006] The facing beam interpolation method has been developed to alleviate this problem. The opposing beam interpolation method means that the projection data collected at the position where the angle differs by 180 °, that is, the projection data collected at each of the opposing positions contains the same tissue information (X-ray absorption rate information) in principle. Then, the projection data collected at a certain Z position is handled as projection data at the same Z position, the phase of which is shifted by 180 ° (hereinafter referred to as opposing data). In such an opposed beam interpolation method, all-angle projection data necessary for reconstructing one tomographic image is obtained while the rotation gantry makes one rotation.
Are distributed over the range of the moving distance, so that the effective slice thickness can be reduced to よ り compared with the simple interpolation method, and the reliability of the tomographic image can be improved in principle twice.

However, in the opposed beam interpolation method, since only half of the reconstructed data is actually collected data (the other half is opposed data in which the actually collected data is used), image noise is smaller than in the simple interpolation method. Therefore, the application site is limited to a high-contrast site such as a bone, and is not suitable for a low-contrast site such as an internal organ.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the distance variance of a collection position at which all angular data necessary to reconstruct one tomographic image is obtained, and to perform distance interpolation. And a helical scan type X-ray computed tomography apparatus capable of improving the reliability of a tomographic image reconstructed from the above data.

Another object of the present invention is to provide a helical scan type X-ray computed tomography apparatus realizing a combination of improvement in low contrast resolution by reducing image noise and high spatial resolution in the axial direction due to a small effective slice thickness. It is to provide.

[0010]

According to the first aspect of the present invention, an X-ray source and a subject are relatively rotated, and the X-ray source and the subject are relatively rotated along the body axis direction of the subject. An X-ray computed tomography apparatus capable of performing a helical scan on a subject by moving the subject in a horizontal direction and reconstructing a tomographic image of a desired slice position based on transmitted X-ray data of the subject. A multi-channel X-ray detector arranged in n rows (n is an integer of 2 or more) along the body axis direction of the subject and collecting transmitted X-rays of the subject, and detected by the X-ray detector Opposing data generating means for generating opposing data at a rotational phase opposite to transmission data at an arbitrary rotational phase, and X-ray detectors for all n columns to obtain projection data at the desired slice position. Obtained transmission data
Data and the corresponding data generated from them
Closest to the desired slice position in the body axis direction
Data extraction means for selectively extracting data corresponding to a plurality of positions at predetermined angles , and interpolation for obtaining projection data at the desired slice position by performing an interpolation process based on the data extracted by the data extraction means A computing unit; and a reconstruction unit configured to reconstruct a tomographic image at the desired slice position based on the projection data obtained by the interpolation computing unit.

According to a fourth aspect of the present invention, the X-ray source and the subject are synchronized.
And the X-ray source and the subject
The subject is moved relatively along the body axis direction.
Helical scan is performed on the X-ray
The tomographic image at the desired slice position is reproduced based on the data.
Configurable X-ray computed tomography device
And n rows (n is 2 or more) along the body axis direction of the subject.
Integer) Multi-channel array for collecting transmitted X-rays of the subject
A channel type X-ray detector and the X-ray source
In the body axis direction between the X-ray source and the subject during one round
X-ray detector having a relative position variation distance along the n rows
Is shorter than the total width in the body axis direction of each of the X-ray detectors.
The X-ray source and the subject are arranged so that the trajectories of the rows do not overlap.
Control the relative movement along the body axis direction with the spiral
Scanning control means for performing scanning .

According to a ninth aspect of the present invention, the X-ray source and the subject are synchronized.
And the X-ray source and the subject
By moving relatively along the body axis direction,
A helical scan is performed on the body, and the X
A tomographic image of a desired slice position is obtained based on the line data.
Reconfigurable X-ray computed tomography equipment
And n rows (n is 2 or more) along the body axis direction of the subject.
(Even number) multiple channels arranged to collect transmitted X-rays of the subject
A channel type X-ray detector, and a relative position between the X-ray source and the subject.
Between the X-ray source and the subject during one full rotation
The relative movement distance is equal to the width of the odd-numbered rows of the X-ray detector.
To control the relative movement between the X-ray source and the subject.
Scan control means for performing the spiral scan by controlling
Have. According to the eleventh aspect, the X-ray source and the subject are synchronized.
And the X-ray source and the subject
The subject is moved relatively along the body axis direction.
Helical scan is performed on the X-ray
The tomographic image at the desired slice position is reproduced based on the data.
Configurable X-ray Combination Tomography Apparatus
And n rows (n is 2 or more) along the body axis direction of the subject.
Integer) Multi-channel array for collecting transmitted X-rays of the subject
A channel type X-ray detector, and a relative position between the X-ray source and the subject.
Between the X-ray source and the subject during one full rotation
The relative movement distance is an integral multiple of the row pitch of the X-ray detector.
Between the X-ray source and the subject so that the distance is different from
A scanner for controlling the relative movement and performing the spiral scan
Control means.

[0013]

SUMMARY OF] According to the present invention 1, n columns (n is an integer of 2 or more) and transmission data detected by the array of multichannel X-ray detector, Ru and the opposing data are prepared .
Whether the prepared data is between the transparent data and the opposing data of all columns
The body at the desired slice position, regardless of the row
Extract data corresponding to multiple closest positions in the axial direction
Then, correction data is generated using the extracted data, and image reconstruction is performed.
The effective slice width, that is, extracted
The maximum distance of the corresponding position of the data can be shortened.

According to the invention of claim 4 , X-ray detection of n columns
It goes without saying that the locus of movement drawn by each container does not overlap
Along the body axis direction between the X-ray source and the subject per revolution
The relative movement distance in the body axis direction of the n rows of X-ray detectors
When the width becomes shorter than the full width, the N-th row of the X-ray detector
The locus drawn by some of the detectors is the
The trajectory when these are combined
Is shorter than the width of one row of detectors, that is,
The spatial resolution of data collection in the body axis direction is one of the detectors
It is higher than the width of the column.

According to the ninth aspect of the present invention, the number of rows of the X-ray detector is n (n is an even number of 2 or more), and the number of rows of the X-ray detector is one while the relative rotation between the X-ray source and the subject is one. X-ray source and subject are X
Since the line detectors are displaced by the width of the odd-numbered columns, the pitches of the spiral orbits of the respective columns when the plurality of rotations are performed are not overlapped, and the data density is improved. Therefore, data at a position closer to the position of the reconstructed cross section can be used, and a tomographic image with a small effective slice thickness can be reconstructed. According to the eleventh aspect, the number of rows of the X-ray detector is n (n is an even number of 2 or more), and the X-ray source and the subject are rotated during one rotation of the relative rotation between the X-ray source and the subject. since the subject is different from the distance displaced from an integral multiple of the row pitch of the X-ray detector, without helical trajectory of each column when the plurality rotated with each other becomes heavy, moreover, N rotation
Locus drawn by some of the n-row X-ray detectors in the eye
Enters between the trajectories of the (N-1) th rotation.
When these are combined, the interval of the trajectory is equivalent to one row of detectors.
Shorter than the width, that is, data collection in the body axis direction
Is higher than the width of one row of detectors. Therefore, data at a position closer to the position of the reconstructed cross section can be used, and a tomographic image with a small effective slice thickness can be reconstructed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the X-ray tomography apparatus according to the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a configuration diagram of an X-ray computed tomography apparatus according to a first embodiment of the present invention. FIG.
(A) is a front view of the rotating gantry of FIG. FIG. 2B is a perspective view showing an arrangement relationship between the X-ray source and the multi-channel X-ray detector row. FIG. 2C is a diagram of the multi-channel X-ray detector array viewed from the X-ray source side.

The rotating gantry 1 includes an X-ray source 2 and a multi-channel detector array 4 including n-channel (n is an integer of 2 or more, where n = 3) multi-channel detector arrays 31 to 33. Hold. The multi-channel detector rows 31 to 33 are arranged to face the X-ray source 2 with the imaging region E interposed therebetween. X
The radiation source 2 emits a cone beam X-ray from the focal point F.
Each of the multi-channel detector rows 31 to 33 includes a plurality of X-ray detection elements 6 arranged along the rotation orbit of the X-ray source 2.
Is provided. Each X-ray detection element 6 independently detects a transmitted X-ray transmitted through the subject. Multi-channel detector
The rows 31 to 33 are arranged at a constant pitch (center between adjacent detector rows) along the object axis perpendicular to the rotation plane of the X-ray source 2 .
Distance) P. Note that the pitch P
2 is defined as follows. Pitch P2 is multi-channel
X-ray source 2 having a pitch P of multiple type detector rows 31 to 33 and multiple channels
Phase around the rotation center of the array of channel detectors 31 to 33
Equivalent distance, that is, the center of rotation radiated from the focal point of the X-ray source 2
Pitch to the multi-channel detector rows 31 to 33 via
Means the width of the X-ray flux irradiated near the center of rotation. Each of the X-ray detection elements 6 is independently used for X-rays passing through the subject.
The line is converted into an electric signal (detection signal) corresponding to the intensity. There are a case where the detection signal of each X-ray detection element 6 corresponds to one channel and a case where the addition of the detection signals of a predetermined number of adjacent X-ray detection elements 6 corresponds to one channel. Hereinafter, for convenience of explanation, the former will be described, but the possibility of the latter is not denied.

As a modification, the rotating gantry 1 holds only the X-ray source 2. In this case, the multi-channel detectors 31 to 33 for one round are fixed along the orbit of the X-ray source 2 opposed to the rotary orbit of the X-ray source 2 with the rotation center interposed therebetween. Here, the former is described in which the X-ray source 2 and the multi-channel detectors 31 to 33 rotate together.

The gantry drive mechanism 7 drives and rotates the rotary gantry 1. The gantry driving mechanism 7 slides the rotating gantry 1 along the body axis of the subject. The couch 8 supports a flat rectangular top plate on which a subject is mounted so as to be slidable along its long axis. The subject is inserted into or pulled out of the imaging region E along the body axis with the sliding of the top plate. The long side of the bed is the axis of rotation of the rotating gantry 1 (the axis passing through the center of rotation C and perpendicular to the paper).
It is installed so that it may become parallel.

The X-ray control unit 9 is a high-voltage generation unit 1
The control signal is output to 0. The high voltage (tube voltage) of the level indicated by the control signal is supplied from the high voltage generation unit 10 to the X-ray source 2.
Is applied to X-rays having an intensity corresponding to the tube voltage are emitted from the X-ray source 2.

The gantry / bed control unit 11 outputs control signals to the gantry driving mechanism 7 and the bed 8, respectively. The gantry driving mechanism 7 continuously rotates the rotary gantry 1 at an angular velocity specified by a control signal supplied from the gantry / bed control unit 11. Further, the gantry driving mechanism 7 continuously slides the rotary gantry 1 at a speed specified by a control signal supplied from the gantry / bed control unit 11. The couch 8 continuously slides on the couchtop at a speed specified by a control signal input from the gantry / couch control unit 11. At least one of the rotating gantry 1 and the top plate is slid. Thereby, the relative position between the rotating gantry 1 and the subject continuously changes along the body axis of the subject. Here, the description will be given on the assumption that the relative position change is performed by stopping the slide of the rotary gantry 1 and sliding only the top plate.

The system control unit 12 controls the gantry / bed control unit 11, the X-ray control unit 9, and the multi-channel type detection units 31 to 33 according to a predetermined sequence. Thus, the helical scan is performed. The gantry / bed control unit 11 controlled by the system control unit 12 rotates the rotary gantry 1 continuously. The bed 8 controlled by the system control unit 12 continuously slides on the tabletop at least while the rotating gantry 1 is rotating. While the rotating gantry 1 is rotating, the X-ray control unit 9 controlled by the system control unit 12 transmits X-rays from the X-ray source 2 continuously or intermittently.
A tube voltage is supplied to the source 2 continuously or intermittently. The multi-channel detectors 31 to 33 controlled by the system control unit 12 determine the X-rays transmitted through the subject while the rotating gantry 1 rotates and the X-ray source 2 emits X-rays. It is detected repeatedly in a cycle. The X-rays emitted from the X-ray source 2 are attenuated according to the sum of the X-ray absorption rates of various tissues existing on the path. The multi-channel detectors 31 to 33 convert the attenuated X-rays into an electric signal of a level corresponding to the intensity. Therefore, the detection signals detected by the multi-channel detectors 31 to 33 include the integrated information of the X-ray absorptivity of each of a plurality of types of tissues existing on the path. This detection signal is digitally converted by the data collection unit 14, and is called projection data in the subsequent processing.

During the execution of the helical scan, the rotation angle of the rotating gantry 1 and the coordinates of the top (hereinafter referred to as the top position or simply the position) are supplied from the gantry / bed control unit 11 to the system control unit 12 as needed. . For this reason, the rotary gantry driving mechanism 7 is provided with a rotary encoder that outputs a pulse signal at every predetermined angle in order to detect the rotation angle of the rotary gantry 1. The gantry / bed control unit 11 counts the pulse signals, and measures the rotation angle of the gantry 1 from the counted number. Similarly, the bed 8 is also provided with a rotary encoder that outputs a pulse signal at predetermined angles via a rack and pinion mechanism. The gantry / bed control unit 11 counts this pulse signal, and measures the position of the tabletop from the counted number.

The system control unit 12 determines the timing at which the multi-channel detectors 31 to 33 detect X-rays transmitted through the subject, that is, the rotation angle of the rotating gantry 1 when each detection signal is detected, The position of the plate (top plate coordinates)
The channel number unique to each detection signal and the detector number of each detection signal are output to the memory controller 31.

The memory controller 13 outputs two write address signals to the storage unit 15 in response to one detection signal. One write address signal is created according to the output from the system control unit 12. The other write address signal, different for each channel in accordance with the output from the system control unit 12
It is created by changing the rotation angle . That is, one detection signal is stored at two addresses. Assuming that the detection signal stored at one address is original data, the detection signal stored at the other address is treated as data opposite to the original data. In addition,
The slice position of data is inherently different for each channel.
However, here, for convenience of explanation, the central channel is used.
The slice position of the data facing
Shall be treated as one. Note that the original data
Data in one place instead of two
In other words, it is not stored as facing data,
It may be read as data. Also memory
15 has a plurality of memories 17 to 21
However, this is an explanation to make it easy to understand the type of data
The memory 15 is actually one memory.
It will be implemented as a memory.

The detection signal detected by each of the multi-channel detectors 31 to 33 is transmitted to the data collection unit 14.
, And are sent to the storage unit 15 independently. Data collection unit 14
The digitally converted detection signal is referred to as projection data after this processing. The projection data of each of the multi-channel detectors 31 to 33 is stored at two addresses in accordance with two write address signals from the memory controller 31.

Here, for convenience of explanation, it is assumed that the multi-channel detectors 31 to 33 have n × 2 memories 16 to 21. As described above, n is the number of columns of the multi-channel detector. The first memory 16 stores projection data (original data) of the multi-channel detector 31 in the first column.
Are stored according to one of the address signals. First
'The memory 17 has a multi-channel detector 31 in the first column.
Is stored as opposing data according to the other address signal. The second memory 18 stores the projection data (original data) of the multi-channel detector 32 in the second column in accordance with one address signal. In the second memory 19, the projection data of the multi-channel detector 32 in the second column is stored as opposed data in accordance with the other address signal. In the third memory 20,
The projection data (original data) of the multi-channel detector 33 in the third column is stored according to one address signal. In the third memory 21, the projection data of the multi-channel detector 33 in the third column is stored as opposed data according to the other address signal. Of course,
So that all the original data in all columns is only one memo
The information may be stored in the storage 15.

In the present embodiment, the opposing beam interpolation method need not be adopted. In this case, in order to obtain the same effect as when the above-described counter beam interpolation method is employed, the number of columns (2 × n) which is twice the number n of the columns of the X-ray detector described above is required.

The system control unit 12 is connected to a section setting section 22 such as a mouse or a trackball for the operator to set and input a position for reconstructing a tomographic image.
The system control unit 12 outputs information on the projection data to be read from the storage unit 15 based on the cross-sectional position set by the cross-section setting unit 22.

According to this information, the memory controller 31 supplies a read address signal to each of the memories 16 to 21 of the storage unit 15. With this read address signal, projection data necessary for distance interpolation is selectively read from the storage unit 15.

Specifically, for each rotation angle from 0 ° to 360 °, two projection data are selected (two corresponding projection data having the same rotation angle are treated as one set). You. For example, the rotating base 1
If the detection operation of the detectors 31 to 33 is repeated every time the motor rotates 2 °, 0 °, 2 °, 4 °,.
°, 356 °, 358 ° for each rotation angle
Two detection signals are selected. Two sets of projection data having the same corresponding rotation angle forming one set are output from the section setting unit 2.
The first projection data corresponding to the position closest to the position of the cross section set in Step 2 and the area on the opposite side of the position of the cross section set by the cross section setting unit 22 with respect to the position of the first detection signal. And the second projection data corresponding to the position closest to the position of the cross section set by the cross section setting unit 22 in FIG. In other words, the projection data corresponding to the position closest to the cross-sectional position is read in each of the two regions with the cross-sectional position set by the cross-section setting unit 22 interposed.

As a result, the projection data selectively read out from the storage unit 15 includes the projection data within a range of a predetermined pitch distance of the detectors 31 to 33 around the position of the cross section set by the cross section setting unit 22. It will correspond to the position.

The projection data read from the storage unit 15 is sent to the interpolation processing unit 23. The interpolation processing unit 23 performs distance interpolation (weighted average) on the two pieces of projection data corresponding to the same rotation angle according to the distance from the cross-sectional position set by the cross-section setting unit 22, and calculates weighted average data. . This weighted average data is stored in the section setting unit 22.
Is handled as projection data at the cross-sectional position set in. This distance interpolation processing is repeated for all rotation angles, and weighted average data for all angles corresponding to each rotation angle from 0 ° to 360 ° is obtained.

The weighted average data of all angles from the interpolation processing unit 23 is sent to the reconstruction processing unit 24.
The reconstruction processing method of the reconstruction processing unit 24, such as the successive approximation method or the Fourier calculation method, calculates a two-dimensional distribution of CT values, that is, original data of a tomographic image, from the weighted average data in all angles. This tomographic image is supplied to the output unit 25 and displayed or stored.

Next, the operation of the first embodiment will be described. FIG.
(A) shows the change of the collection position (detection position) and rotation angle of a plurality of projection data (original data (transmission data) of the other channel type detector 31 in the first column) stored in the first memory 16 by a solid line. The change of the collection position and rotation angle of the plurality of projection data (opposite data) stored in the first memory 17 is shown by a thin line. FIG. 3B shows a change in the collection position and rotation angle of a plurality of projection data (original data (transmission data)) stored in the second memory 18 with a solid line.
The change of the collection position and rotation angle of a plurality of projection data (opposite data) stored in the memory 19 is indicated by a thin line. FIG.
(C) shows the change in the collection position and the rotation angle of the plurality of projection data (original data) stored in the third memory 20 by a solid line, and the plurality of projection data (opposite data) stored in the third memory 21. The change of the collection position and the rotation angle is indicated by a thin line.

In the first embodiment, projection data is collected by helical scan. In the present embodiment, projection data of all angles on the cross section is prepared by the opposing beam interpolation processing method. Since the helical scan and the opposing beam interpolation processing method are known, they will be briefly described.

The helical scan is executed by the system control unit 12 controlling the X-ray control unit 9, the multi-channel detectors 31 to 33, and the gantry / bed control unit 11. Specifically, the gantry / bed control unit 11 controlled by the system control unit 12 rotates the rotary gantry 1 continuously. The bed 8 controlled by the system control unit 12 continuously slides on the tabletop at least while the rotating gantry 1 is rotating.
While the rotating gantry 1 is rotating, the system control unit 1
The X-ray control unit 9 controlled by the X-ray source 2
A tube voltage is supplied to the X-ray source 2 continuously or intermittently in order to continuously or intermittently emit the radiation. Multi-channel detector 3 controlled by system control unit 12
1 to 33, the rotating base 1 rotates and the X-ray source 2
While the line is being exposed, X-rays that have passed through the subject are repeatedly detected at a predetermined cycle.

The X-rays emitted from the X-ray source 2 are attenuated by the tissue on the path, and are multi-channel detectors 31 to 33.
Are detected by the respective detection elements 6. During the execution of the helical scan, the system control unit 12 informs the memory controller 31 of the timing when the multi-channel detectors 31 to 33 detect the X-rays passing through the subject, that is, when the respective detection signals are detected. Each data of the rotation angle of the rotating gantry 1, the position of the tabletop (tabletop coordinates), the channel number unique to each detection signal, and the detector number unique to each detection signal is output.

For example, the first-row multi-channel detector 3
1, when the detection signal of a certain channel is detected, the rotation angle θa of the rotating gantry 1 and the position Pa of the tabletop when the detection signal is detected are transmitted to the memory controller 31 together with the channel number and the detector number. Supplied. The memory controller 31 separately supplies two types of write address signals corresponding to the rotation angle θa, the top panel position Pa, the channel number, and the detector number to the first memory 17 and the first memory 18. . One write address signal is created according to the rotation angle θa, the top panel position Pa, the channel number, and the detector number. The other write address signal has a different rotation for each channel.
It is created according to the rotation angle θa ′ changed to the angle , the top panel position Pa, the channel number, and the detector number. In other words, two identical projection data are stored at different addresses only in the corresponding rotation angles, one of which is original data and the other of which is facing data. Detection signals detected at other timings are similarly stored. Detection signals detected in other channels are also stored. The detection signals detected by the other multi-channel detectors 32 and 33 are similarly stored. Of course,
As described above, only all original data in all columns is 1
It may be stored in one memory 15.

FIG. 4 is a diagram collectively showing FIGS. 3 (a) to 3 (c), showing changes in the collection position and rotation angle of all projection data (original data) detected by helical scanning. indicated by the solid line, it is shown by a thin line a change in rotational angle between the collection location of these plurality of counter data. In FIG. 4, P1 indicates a distance (top plate feed pitch) that the top moves during one rotation of the rotary gantry 1, and P2 indicates a multi-channel.
X-ray source 2 having a pitch P of multiple detector rows 31 to 33 and multiple
In the vicinity of the rotation center of the channel type detector rows 31 to 33
Equivalent distance, that is, the center of rotation emitted from the focal point of the X-ray source 2
Pitch to multi-channel detector rows 31 to 33 via
Indicates the width of the X-ray flux irradiated at the width of P near the center of rotation ,
P3 indicates the data pitch by the opposing beam interpolation method. As shown in FIG. 4, an opposite data string of a certain detector is
It is an important requirement of the present invention that the helical scan be performed so as to be located between the two original data trajectories of the other two detectors, that is, the projection data required to reconstruct a tomographic image. This is one of the important requirements for narrowing the spread (dispersion) of the position and narrowing the effective slice thickness to improve the spatial resolution in the body axis direction. One example for realizing this is the following condition. This condition
The number of rows n of the multi-channel type detector row 4 is slightly different between an odd number and an even number.

When the number n of rows of the multi-channel type detector row 4 is an odd number, the system control unit 12 controls the gantry / bed control unit 11 so as to satisfy the following equation (1). P1 = n × P2 (1) That is, the distance P1 by which the tabletop moves while the rotating gantry 1 makes one rotation, in other words, the rotating gantry 1 and the subject relatively change while the rotating gantry 1 makes one rotation. The distance P1 to be detected is
The system control unit 12 relatively determines the rotational angular velocity of the rotating gantry 1 and the movement of the top board so as to match the full width (n × P2) of 1 to 33.

When the number n of rows of the multi-channel detector row 4 is an even number, the system control unit 12 controls the gantry / bed control unit 11 so as to satisfy the following equation (2). P1 = (n−1) × P2 (2) That is, the distance P1 that the top board moves while the rotating gantry 1 makes one rotation, in other words, the rotating gantry 1 and the subject move while the rotating gantry 1 makes one rotation. The relatively changing distance P1 is detected by the detector 3
The distance obtained by subtracting the parallel pitch P2 from the total width of 1 to 33 ((n
-1) × P2), the rotational angular velocity of the rotary gantry 1 and the movement of the tabletop are relatively related to the system control unit 1
2 In this case, the trajectory of the n-th detector in the last row matches the trajectory of the first detector in the front row, and the existence of the n-th detector is meaningless. Therefore, ideally, the number n of rows of the multi-channel detector row 4 is n.
Is preferably an odd number from the viewpoint of cost performance. However, even if the number n of the multi-channel detector rows 4 is an even number, this does not mean that the effect is lower than that in the case of an odd number.

The memory controller 31 generates two write address signals for one channel of projection data detected by one detector at a certain timing. As described above, one write address signal is generated according to the output from the system control unit 12, and the other write address signal is generated in the same manner as the one write address signal.
However, only the rotation angle of the rotary gantry 1 when the detection signal is detected is changed to a rotation angle shifted by 180 °. That is, one projection data is separately stored at two addresses, that is, for example, the detection signal stored at the address of the first memory 16 at the address of the rotation angle, the top plate position in this case, the channel number, and the column number. The same thing is the first data as the opposite data.
The rotation angle, the top position in this case, the channel number, and the column number address of the memory 17 are stored.

After the helical scan is completed, or during the execution of the helical scan,
A position for reconstructing a tomographic image is set and input. The system control unit 12 outputs data indicating the position range of the projection data to be read from the storage unit 15 and the facing data based on the position of the cross section set by the cross section setting unit 22.

Based on the data of the position range, the detector 31 1 is centered on the position of the section set by the section setting section 22.
A range of distances of .about.33 parallel pitches P2 is designated. FIG. 5 is a diagram corresponding to FIG. 4, and the distribution of the projection data and the counter data read from the storage unit 15 is indicated by a thick line. Z0 in FIG. 5 indicates the position of the cross section set by the cross section setting unit 22.

That is, the parallel pitch P of the detectors 31 to 33 is centered on the position of the section set by the section setting section 22.
All the projection data and the facing data within the range of the distance of 2 are read from the storage unit 15. As mentioned above, such that the opposing beam train of one detector is located between the two original data distributions of the other two detectors,
Since the helical scan is being executed, the projection data and the facing data to be read are read according to the following rules.

That is, for each rotation angle from 0 ° to 360 °, two sets of projection data (including opposing data) are selected. For example, assuming that the detecting operation of the detectors 31 to 33 is repeated every time the rotating gantry 1 rotates 2 °, 0 °, 2 °, 4 °.
For each rotation angle of 356 ° and 358 °, two sets of projection data (including opposing data) are selected. Moreover,
The two projection data corresponding to the same rotation angle include a first projection data corresponding to a position closest to the position of the cross section set by the cross section setting unit 22, and a cross section setting corresponding to the position of the first projection data. And second projection data corresponding to a position closest to the position of the cross section set by the cross section setting unit 22 in a region on the opposite side of the position of the cross section set by the unit 22.

The projection data and the opposing data selectively read from the storage unit 15 are sent to the interpolation processing unit 23. The interpolation processing unit 23 performs distance interpolation (weighted averaging) on the two projection data and the opposing data corresponding to the same rotation angle in accordance with the distance from the position of the cross section set by the cross section setting unit 22, and performs weighted averaging. The data, that is, an estimated value of the projection data at the position of the cross section set by the cross section setting unit 22 is created.

FIG. 6 is a diagram for explaining the interpolation process.
It is a figure which extracts and shows only the thick line part of FIG. As shown in FIG. 6, for example, regarding the rotation angle θα, the projection data D3 on Z0 of the rotation angle θα is calculated from the two projection data D1 and D2 of the rotation angle θα as shown in equation (3). . A indicates the distance between the positions Z1 and Z0 of D1, and b indicates the distance between the positions Z2 and Z0 of D2.

[0050] D3 = (b × D1 + a × D2) / (a + b) ... (3) Distance interpolation This is repeated for all rotation angles each, all of the rotation angle of the rotation angle 0 ° to 360 DEG All angular weighted average data corresponding to each is obtained.

The whole angular weighted average data from the interpolation processing unit 23 is sent to the reconstruction processing unit 24.
A reconstruction processing method such as the successive approximation method or the Fourier calculation method of the reconstruction processing unit 24 reconstructs a two-dimensional distribution of CT values, that is, a tomographic image, from the weighted average data in all angles. This tomographic image is supplied to the output unit 25 and displayed or stored.

As described above, according to the first embodiment, the spread (effective slice thickness) related to the position of the projection data required for reconstructing a tomographic image can be determined by using the conventional X-ray detection line, the X-ray detection line, or the like. It is possible to improve spatial resolution in the body axis direction by making the line detection line a plurality of lines, in which the top plate moving speed with respect to the rotation angular velocity of the rotating gantry is not controlled as described above, and it is dramatically narrower. it can. Traditionally, this spread
This is the distance P1 of the top board that moves during one rotation of the rotating gantry , and this spread is P1 / 2 even in the conventional case using the opposing beam interpolation method. In contrast, the present invention
P2 / 2, that is, half the detector pitch, and n = 3
(N is the number of columns), P2 × n = P2 × 3 = P1
And P2 / 2 = P1 / 6 .

The rotating gantry 1 includes an X-ray source 2 and n-row (here, n = 10) multi-channel detectors 31 and 32.
.. Are arranged opposite to each other with the imaging region interposed therebetween, and are held rotatably about the center of the imaging region while maintaining this facing relationship. The X-ray source 2 emits cone-beam X-rays from a focal point. The multi-channel detectors 31, 32,..., 3n are arranged in parallel at a predetermined pitch (hereinafter referred to as detector pitch) p along an axis (slice axis or Z axis) perpendicular to the rotation plane of the X-ray source 2. The detector pitch p is defined by the distance between the width centers of adjacent multi-channel detectors. Multi-channel detectors 31, 32 ... 3n
Each includes a plurality of detection elements arranged in parallel in the rotational plane of the X-ray source 2 at an equal distance from the focal point of the X-ray source 2. The detection elements are each independently X transmitted through the subject.
The line is converted into an electric signal according to its intensity. For example, 1
One detecting element or a predetermined number of adjacent detecting elements correspond to one channel. Note that the so-called fourth-generation structure in which only the X-ray source 2 is held by the rotating gantry 1 and the multi-channel detector array 4 for one round is fixed at a position to receive X-rays from the X-ray source 2 is provided. Is also good.

The gantry drive mechanism 7 drives and rotates the rotary gantry 1. The couch 8 supports a top plate 29 on which a subject is mounted so as to be slidable along the longitudinal direction. The couch driving mechanism 26 drives and slides the top board 29, and puts the subject in and out of the imaging region along the body axis direction (the same as the longitudinal direction of the top board 29). As a result, the positions of the imaging region and the subject relatively change. Note that the top plate 29 is fixed, and the gantry 1 slides along the body axis direction of the subject, or the top plate 29 and the gantry 1 move in directions opposite to each other, so that the imaging region and the subject A mechanism that changes the relative positional relationship may be adopted.

The X-ray control unit 9 is a high-voltage generation unit 1
The control signal is output to 0. A high voltage according to the control signal is applied from the high voltage generation unit 10 to the X-ray source 2 as a tube voltage. X-rays having energy corresponding to the tube voltage are emitted from the X-ray source 2.

The gantry / bed control unit 11 sends control signals to the gantry driving mechanism 7 and the gantry driving mechanism 26, respectively.
The gantry drive mechanism 7 rotates the rotary gantry at a constant speed at an angular velocity indicated by a control signal supplied from the gantry / bed control unit 11. The couch driving mechanism 26 slides the couchtop 29 of the couch 8 at a constant speed at a speed specified by a control signal supplied from the gantry / couch control unit 11. Here, the distance that the top plate 29 slides while the rotary gantry 1, in other words, the X-ray source 2 makes one rotation, is determined by the top plate feed pitch d.
Is defined as

The system control unit 12 controls the gantry / bed control unit 11, the X-ray control unit 9, the multi-channel detector array 4, and the data acquisition unit 14 according to a predetermined sequence, and executes a helical scan. The gantry / bed control unit 11 controlled by the system control unit 12 continuously rotates the rotating gantry 1 at a constant angular velocity, and simultaneously slides the top plate 29 of the bed 8 at a constant speed. During this time, the X-ray control unit 9 controlled by the system control unit 12 generates X-rays from the X-ray source 2 continuously or intermittently. Each detection element of the multi-channel detector array 4 controlled by the system control unit 12 converts an X-ray transmitted through the subject into an electric signal of a level corresponding to the intensity thereof at a predetermined period (for example, when the X-ray source 2 is 2 °). Time to rotate 1
Data collection unit 1)
4 is output. The data collection unit 14 controlled by the system control unit 12 sequentially converts the electric signals converted in each channel of the multi-channel detector array 4 into digital data.

During the execution of the helical scan, the rotation angle of the rotating gantry 1 and the
The coordinates (top position) of the system control unit 12
Is taken in at any time. For this purpose, the rotary gantry driving mechanism 7
Is provided with a rotary encoder (not shown) that generates a pulse signal at every predetermined angle, and the gantry / bed control unit 11 counts the pulse signal and measures the rotation angle. Similarly, the top board 29 is provided with a rotary encoder (not shown) via a rack and pinion mechanism, and generates a pulse signal each time the top board 29 slides a predetermined distance. The gantry / bed control unit 11 The signal is counted and the top position is measured.

The system control unit 12 determines the rotation angle of the rotary gantry 1 at the timing when the multi-channel detector array 4 detects the transmitted X-rays, the position of the top plate 29, the channel number of each detected data, the multi-channel X Line detectors 31 to 3
n The unique detector number for each
Output to 3. The memory controller 13 controls the rotation angle from the system control unit 12, the position of the top plate 29,
A write address signal is created according to the channel number and the detector number, and output to the storage unit 15.
The detection data digitally converted by the data collection unit 14 is individually sent to the storage unit 15 and stored at each address according to the write address signal output from the memory controller 13. This address is for applying the simple interpolation method.

The system control unit 12 is connected to a section setting unit 22 for specifying the position (slice position or Z position (Z coordinate)) of the tomographic image desired by the operator. The system control unit 12 supplies the information on the reconstructed section position set by the section setting unit 22 to the memory controller 13 together with a data read command. According to this information, the memory controller 13 creates a read address signal and supplies it to the storage unit 15. With this read address signal, data necessary for reconstructing a tomographic image relating to the reconstructed cross-sectional position is selectively read from the storage unit 15. Specifically, two data are read for each minute rotation angle of 0 ° to 360 °. That is, two data corresponding to the same rotation angle are read. One of these two data is the data corresponding to the Z position closest to the reconstruction cross-section position in the area on the plus side of the reconstruction cross-section position with respect to the Z axis, and the other of the two data is the reconstruction data with respect to the Z axis. This is data corresponding to the Z position closest to the reconstructed cross section position in a region on the minus side of the configured cross section position.

Note that this is a condition when only so-called interpolation (interpolation such that the Z position of interpolation data is sandwiched between the Z positions of two original data) is used. As a modification, extrapolation interpolation is used. When (interpolation such that the Z position of the interpolation data is not sandwiched between the Z positions of the two original data) is also used together with the interpolation, the two data having the same rotation angle are simply reconstructed regardless of the area. Two data are obtained in the order closest to the cross-sectional position.

The data read twice from the storage unit 15 for each rotation angle is taken into the distance interpolation unit 23. In the distance interpolation unit 23, the two data corresponding to the same rotation angle are each multiplied by a coefficient (the sum of the two coefficients is 1) corresponding to the distance from the reconstruction sectional position,
Is added. Thus, weighted average data (interpolated data) of the rotation angle for the reconstructed cross-sectional position is created. The generation of the interpolation data is executed for every rotation angle, and finally, weighted average data for all the rotation angles is obtained.

Based on the weighted average data for all the angles, the reconstruction processing unit 24 reconstructs a two-dimensional distribution (tomographic image) of CT values related to the reconstructed cross section by an appropriate reconstruction processing method. The image data of this tomographic image is displayed or stored in the output unit 25.

Next, the operation of this embodiment will be described. Here, the description will be made on the assumption that the number of columns of the multi-channel detectors 31 to 3n is 10, that is, n = 10. 8 and 9 show the rotating base 1
Is expressed by the trajectory of the projection data collected by each of the multi-channel detectors 31 to 310 during three rotations, that is, the Z position of the top plate 29 and the rotation angle of the rotary base 1 when each data is collected. The trajectory is shown, and the setting mode of the top plate feed pitch d is different between FIG. 8 and FIG. One of the modes is selected by the operator via the mode setting unit 28 connected to the system control unit 12. Note that the distance (detector pitch) about the Z-axis between the width centers of adjacent multi-channel detectors is p, and the rotating gantry 1 (X-ray source 2)
Let d be the moving distance (top plate feed pitch) of the top plate 29 that moves during one rotation of. FIG. 8 shows a case where d = 4.5 × p.

FIG. 9 shows the case where d = (10/3) × p.

In any setting mode, the rotating frame 1
Every time it rotates, the Z position of the data is shifted by p / 2 in the setting mode of FIG. 8 and the Z position of the data is shifted by p / 3 in the setting mode of FIG. The top plate feed pitch d is set so that the data trajectories of the multi-channel detectors 31 to 310 do not overlap. Thus, it is possible to increase the density of the original data which is the source of the weighted average data reconstruction cross-sectional position. The origin
As null data, it was not actually collected
Only actual data may be used, or the corresponding position may be shifted
It may be just data, or actual data and corresponding
It may be mixed with the opposite data whose position is shifted. However
Then, image noise is reduced by creating weighted average data only from the original data without using the facing data, and the effective slice thickness is reduced by narrowing the pitch P of the original data, and the spatial resolution in the axial direction is reduced. A high image can be obtained.

In the case of FIG. 8, 10 rows (n = 10) of multi-channel detectors 31 to 310 are installed, and the detector pitch p
The top plate 29 is slid at a top plate feed pitch (d = 4.5 × p) that is 4.5 times that of FIG. As a result, the data pitch P
Can be set to p / 2. Further, 10 rows (n = 10) of multi-channel detectors 31 to 310 are installed, and a top plate feed pitch (d = (10/3) × p) that is 10/3 times the detector pitch p.
The top plate 29 is slid. Thereby, the data pitch P can be set to p / 3.

FIG. 10 shows data extracted from the storage unit 15 for reconstruction in the case of FIG. As described above, a simple interpolation method is employed here instead of the opposed beam interpolation method. Consider a case in which weighted average data corresponding to, for example, a rotation angle of 90 ° is obtained for a reconstructed cross section position set by the operator via the cross section setting unit 22. The two projection data that are the basis of the weighted average data with respect to the rotation angle of 90 ° are the data a closest to the reconstruction section position in the area A on the left side of the reconstruction section position (the multi-channel detector 37 2 in the seventh column). (The data at the rotation angle of 90 ° obtained at the rotation) and the data b (the third row of the multi-channel detector 33 in the third column) closest to the reconstruction cross-section position in the area B on the right side of the reconstruction cross-section position. Obtained data at a rotation angle of 90 °). From these data a and b, weighted average data x at a rotation angle of 90 ° at the reconstruction sectional position is obtained by distance interpolation. By executing this process individually for all rotation angles at the reconstruction cross-sectional position, data (interpolation data or weighted average data) of all angles necessary for the reconstruction process at the reconstruction cross-section position can be obtained. Become. In other words, the original data exists in the portion indicated by the bold line in FIG. 10, that is, the range of p / 2 before and after the reconstruction sectional position, that is, the p of the reconstruction sectional position as the center. The range can be limited (narrowed). Similarly, in the case of FIG. 9, the original data is centered on the reconstructed cross-section position, that is, in the range of p / 3 before and after the reconstructed cross-section position, in other words, on the reconstructed cross-sectional position (2/3).
It can be limited (narrowed) to the range of × p.

If the example described above is generalized to the number n of detector rows, it can be expressed as follows. However, here
Examples of conditions for obtaining the highest sampling density
This is an example, and the present invention is not limited to this. Said earlier
Between the item of paragraph number 0040 and the item of paragraph number 0066
Free as long as the purpose described in either one can be achieved
Changes are possible and may be achieved under other conditions
However, the conditions for obtaining a slightly lower sampling density may be used.
No. The top plate feed pitch d is Under the condition that satisfies the following condition, the top plate feed pitch d is arbitrarily adjusted via the mode setting device, so that the data pitch P
Can be P = p / m. Here, in the case where the opposite beam interpolation is not used and only the interpolation is performed by the simple interpolation method, the projection data necessary for the reconstruction is limited to a range of (2 × p) / m (effective slice thickness). Can be. In FIG. 8, the effective slice thickness is p, and in FIG. 9, the effective slice thickness is (2 /
3) xp When the weighted average data is obtained from the projection data, the original projection data is all the original data actually collected and not the facing data. Excellent noise and image quality equivalent to simple interpolation can be obtained. The pitch of the projection data is p / m
Thus, an effective slice thickness equal to or less than that of the first embodiment can be obtained.

Although the present embodiment has been described based on the simple interpolation method as described above, the counter beam interpolation method may of course be applied. For example, FIG. 11 shows a data trajectory when the opposite beam interpolation method is applied under the conditions of FIG. In this case, the data pitch is p / 2m. Since one of the projection data for obtaining the weighted average data is the opposite beam, the image noise increases compared to the simple interpolation method. However, the reduction of the data pitch has the effect of further reducing the effective slice thickness.

As described above, according to the present embodiment, in addition to the high speed, which is the effect of the multi-slice helical scan, the image data can be obtained in a short time, with little image noise, low contrast resolution, and high spatial resolution in the body axis direction. (Voxel data) can be obtained. The reason is that the original data whose data trajectory crosses the reconstructed cross section is larger than that in the first embodiment, so that it is possible to perform reconstruction using only the original data without increasing the effective slice thickness, thereby reducing image noise. Because you do.

The present invention is not limited to the embodiments described above, but can be implemented with various modifications. For example, in the above-described embodiment, since the top plate feeding speed is reduced, an artifact may occur when a scan time is long and an image of a fast-moving part is photographed, or when the subject is intense due to respiration or the like. there were. In order to avoid this problem, it is important to be able to select a mode in which the top plate can be slid at high speed without being limited by the above-mentioned conditions of the top plate feed pitch. It is.

[0073]

According to the first aspect of the present invention, an X-ray source for irradiating X-rays and a subject to be irradiated with the X-rays are relatively rotated, and the X-ray source and the subject are rotated. By relatively moving the subject along the body axis direction, a spiral scan is performed on the subject, and X-rays transmitted through the subject are detected by an X-ray detector array. In an X-ray computed tomography apparatus capable of reconstructing a tomographic image of a desired reconstruction cross-sectional position in the body axis direction, n rows (n is an integer of 2 or more) parallel along the body axis direction of the subject And the transmission X of the subject during the spiral scan
An X-ray detector array for collecting transmission data by X-rays;
Facing data generating means for generating facing data having a rotating phase opposed to data of an arbitrary rotating phase detected by the line detector row for each of the X-ray detector rows; The first data corresponding to the closest acquisition position and the first data corresponding to the acquisition position closest to the reconstruction sectional position in a region opposite to the acquisition position of the first data with respect to the reconstruction sectional position. Data extracting means for selectively extracting a set consisting of the second data at every predetermined angle from the transmission data and the opposed data, and interpolating based on the first and second data extracted by the data extracting means. An interpolating means for obtaining projection data at the reconstructed cross-sectional position by performing an operation, and reconstructing a tomographic image at the reconstructed cross-sectional position based on the projection data obtained by the interpolating means. ; And a reconstruction unit.

According to the first aspect of the present invention, the first data corresponding to the acquisition position closest to the reconstruction section and the first data corresponding to the acquisition position of the first data on the opposite side with respect to the reconstruction section. A set consisting of the second data corresponding to the acquisition position closest to the reconstruction cross section in the region is selected from a plurality of transmission data and counter data at each predetermined angle, and is subjected to reconstruction processing after interpolation calculation. Can be done. Therefore, since the tomographic image is reconstructed from the data closest to the reconstructed cross-section position in each of the two regions sandwiching the reconstructed cross-section, the reliability of the tomographic image is improved.

According to a sixth aspect of the present invention, an X-ray source for irradiating X-rays and a subject irradiated with the X-rays are relatively rotated,
And, by relatively moving the X-ray source and the subject along the body axis direction of the subject, a helical scan is performed on the subject, and X-rays transmitted through the subject are scanned.
In an X-ray computed tomography apparatus capable of reconstructing a tomographic image of a desired reconstruction cross-sectional position in the body axis direction by detecting a line with an X-ray detector row, A plurality of X-ray detector rows that are arranged in parallel along the X-ray detector and collect transmission data of transmitted X-rays of the subject during the spiral scan; and a first X-ray detector row corresponding to the collection position closest to the reconstruction cross-sectional position. A set consisting of data and second data corresponding to an acquisition position closest to the reconstructed cross-sectional position in a region opposite to the reconstructed cross-sectional position with respect to the collection position of the first data is described above. A data extracting means for selectively extracting each of the transmission data obtained by the X-ray detector row;
Interpolation calculating means for obtaining projection data at the reconstructed cross-sectional position by performing an interpolation calculation based on the second data, and a tomographic pattern at the reconstructed cross-sectional position based on the projection data obtained by the interpolation calculating means. Reconstructing means for reconstructing an image.

According to the sixth aspect of the invention, the same operation as that of the first aspect of the invention is obtained, but so-called counter beam interpolation is not employed. Therefore, the invention of claim 6 improves the reliability of the tomographic image in a range that is not as great as that of the invention of claim 1.

According to the eleventh aspect of the present invention, the X-ray source for irradiating X-rays and the subject to which the X-rays are irradiated are relatively rotated, and the X-ray source and the subject are connected to the subject. A spiral scan is performed on the subject by relatively moving the subject along the body axis direction, X-rays transmitted through the subject are detected by an X-ray detector, and the detection data is used. In the X-ray computed tomography apparatus for reconstructing a tomographic image at a desired reconstruction cross-sectional position in the body axis direction, n rows (n is an integer of 2 or more) along the body axis direction of the subject
A multi-channel X-ray detector arranged in parallel, moving means for relatively moving the positional relationship between the X-ray source and the subject in the body axis direction, and
In order that the trajectories of the data detected by the line detector do not overlap,
And control means for controlling a movement pitch at which the X-ray source and the subject relatively move during one rotation of the X-ray source.

According to the eleventh aspect of the present invention, since the density of detection data in the body axis direction increases, an image can be reconstructed only from actually detected data. Therefore, image noise can be reduced while suppressing an increase in effective slice thickness. , A low contrast resolution can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an X-ray computed tomography apparatus according to a first embodiment.

FIG. 2 is a structural diagram of an X-ray source and an X-ray detector of FIG.

FIG. 3 shows a collection trajectory of detection data and this opposing data as X
The figure shown for every line detector.

FIG. 4 is a diagram showing a collection trajectory of all detected data and the facing data.

FIG. 5 is a diagram showing an effective slice thickness of the first embodiment.

FIG. 6 is a diagram illustrating a distance interpolation method.

FIG. 7 is a configuration diagram of an X-ray computed tomography apparatus according to a second embodiment.

FIG. 8 is a diagram showing a collection trajectory of detection data for three rotations under a first condition.

FIG. 9 is a diagram showing a collection trajectory of detection data for three rotations under a second condition.

FIG. 10 is a diagram showing the effective slice thickness of the second embodiment.

FIG. 11 is a view showing detection data for three rotations and a collection trajectory of facing data under the first condition when the second embodiment is applied to the facing beam method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotary stand, 2 ... X-ray source, 31-3n ... Multi-channel type X-ray detector, 6 ... X
Line detection element, 7 ... gantry drive mechanism,
8: bed, 9: gantry / bed control unit,
10 ... High pressure generation unit, 11 ... X-ray control unit,
12 ... system control unit, 13 ...
Memory controller, 14: Data collection unit, 15: Storage unit,
16-21: memory, 22: cross section setting unit,
23 ... interpolation processing unit, 24 ... reconstruction processing unit, 25 ... output unit.

Claims (17)

(57) [Claims] 1. An X-ray source and a subject are relatively rotated,
A spiral scan is performed on the subject by relatively moving the X-ray source and the subject along the body axis direction of the subject, and a desired scan is performed based on the transmitted X-ray data of the subject. An X-ray computed tomography apparatus capable of reconstructing a tomographic image of a slice position to be sliced, wherein n rows (n is an integer of 2 or more) are arranged along the body axis direction of the subject and transmitted X-rays of the subject are collected A multi-channel type X-ray detector, and opposing data generating means for generating opposing data in a rotational phase opposite to transmission data of an arbitrary rotational phase detected by the X-ray detector; To obtain the projection data of the slice position ,
Transmission data obtained by all X-ray detectors in n columns and it
In the body axis direction with the oncoming data generated from
At a plurality of positions closest to the desired slice position.
Data extraction means for selectively extracting corresponding data for each predetermined angle; interpolation calculation means for obtaining projection data at the desired slice position by performing interpolation processing based on the data extracted by the data extraction means; X-ray computed tomography apparatus characterized by comprising: reconstruction means for reconstructing a tomographic image at the desired slice position based on the projection data obtained by the interpolation calculation means. 2. The method according to claim 1, wherein each of the selectively extracted data is the transmission data and the opposing data sandwiching the desired slice position. The interpolation operation means interpolates the transmission data and the opposing data. The X-ray computed tomography apparatus according to claim 1, wherein 3. The method according to claim 1, wherein each of the selectively extracted data is the transmission data and the opposing data, and the interpolation calculating means performs extrapolation using the transmission data and the opposing data. The X-ray computed tomography apparatus according to claim 1, wherein: 4. An X-ray source and a subject are relatively rotated,
A spiral scan is performed on the subject by relatively moving the X-ray source and the subject along the body axis direction of the subject, and a desired scan is performed based on the transmitted X-ray data of the subject. An X-ray computed tomography apparatus capable of reconstructing a tomographic image of a slice position to be sliced, wherein n rows (n is an integer of 2 or more) are arranged along the body axis direction of the subject and transmitted X-rays of the subject are collected A multi-channel X-ray detector, and the X-ray source while the X-ray source makes one round around the subject.
Variation of relative position between source and subject along body axis
The distance is shorter than the total width in the body axis direction of the n-row X-ray detectors
Scan control for controlling the relative movement of the X-ray source and the subject along the body axis direction so that the movement trajectories of the respective rows of the X-ray detector do not overlap with each other. X-ray computed tomography apparatus comprising: 5. An apparatus according to claim 1, further comprising: facing data generating means for generating facing data having a rotating phase opposed to transmission data having an arbitrary rotating phase detected by said X-ray detector. 4. The X-ray computed tomography apparatus according to 4. 6. The data detected by the X-ray detector includes:
6. The X-ray computed tomography apparatus according to claim 5, wherein the data is transmission data of a predetermined column and the counter data of the predetermined column or another column. 7. The data detected by the X-ray detector includes:
5. The X-ray computed tomography apparatus according to claim 4, wherein the transmission data includes a predetermined column and transmission data of the predetermined column or another column. 8. The X-ray computed tomography apparatus according to claim 6, wherein the opposed data is of a channel near the center of the X-ray detector. 9. An X-ray source and a subject are relatively rotated,
Further, the X-ray source and the subject are relatively moved along the body axis direction of the subject to perform a spiral scan on the subject, and a desired scan is performed based on the transmitted X-ray data of the subject. An X-ray computed tomography apparatus capable of reconstructing a tomographic image at a slice position, wherein n rows (n is an even number of 2 or more) arranged along the body axis direction of the subject are transmitted X-rays of the subject. A multi-channel X-ray detector to be collected; and a relative movement distance between the X-ray source and the subject during one rotation of the relative rotation between the X-ray source and the subject.
Scan control means for controlling the relative movement between the X-ray source and the subject so as to coincide with the width of the odd-numbered rows of the line detector and performing the spiral scan. Ray computed tomography device. 10. The control of the relative movement between the X-ray source and the subject by the scan control means is as follows: P1 = (n−1) × P2 where P1 is a relative value between the X-ray source and the subject. 1 rotation
The X-ray detector according to claim 9, wherein the rotation is performed based on a relative movement distance between the X-ray source and the subject during rotation, and P2 is a pitch between adjacent detector rows. Ray computed tomography device. 11. The X-ray source and the subject are relatively rotated, and the X-ray source and the subject are relatively moved along the body axis direction of the subject, whereby the X-ray source and the subject are moved relative to the subject. A helical scan is performed, and X to reconstruct a tomographic image at a desired slice position based on the transmitted X-ray data of the subject
A multi-channel X-ray detector arranged in n rows (n is an integer of 2 or more) along the body axis direction of the subject and collecting transmitted X-rays of the subject; The relative movement distance between the X-ray source and the subject during one rotation of the relative rotation between the X-ray source and the subject is represented by X
Scan control means for controlling the relative movement between the X-ray source and the subject so as to perform the spiral scan so that the distance is different from an integral multiple of the row pitch of the line detector. X-ray computed tomography apparatus. 12. A set consisting of first data and second data for obtaining projection data at the desired slice position is selectively extracted from data detected by the X-ray detector at every predetermined angle. Data extracting means; interpolation calculating means for performing an interpolation process based on the first and second data extracted by the data extracting means to obtain projection data at the desired slice position; 5. The apparatus according to claim 4, further comprising: reconstructing means for reconstructing a tomographic image at the desired slice position based on the obtained projection data.
Ray computed tomography device. 13. The first and second data are transmission data of a predetermined column and transmission data of the predetermined column or another column, and the interpolation operation means performs interpolation with the transmission data. 13. The X-ray computed tomography apparatus according to claim 12, wherein the apparatus is an apparatus. 14. The first and second data are transmission data of a predetermined column and transmission data of the predetermined column or another column, and the interpolation calculation means performs extrapolation using the transmission data. 13. The X-ray computed tomography apparatus according to claim 12, wherein the apparatus is an apparatus. 15. An opposing data generating means for generating opposing data having a rotational phase opposite to transmission data having an arbitrary rotational phase detected by the X-ray detector, wherein the data extracting means comprises: 13. The X-ray computed tomography apparatus according to claim 12 , wherein the X-ray computed tomography apparatus is configured to selectively extract the transmission data and the facing data for each predetermined angle. 16. The first and second data are transmission data of a predetermined column and opposing data of a predetermined column or another column, and the interpolation calculating means interpolates the transmission data and the opposing data. Claims characterized by interpolating
12 X-ray computed tomography apparatus according. 17. The first and second data are transmission data in a predetermined column and opposing data in a predetermined column or another column, and the interpolation operation means extrapolates the transmission data and the opposing data. Claims characterized by interpolating
16. The X-ray computed tomography apparatus according to 15 .