JPH0819532A - X-ray computer tomography device - Google Patents

Abstract

PURPOSE:To enhance the low contrast resolution and achieve a high spatial resolution in the body axis direction by selecting a set of first and second data pieces corresponding to the data collecting positions nearest the restructured section on its both sides among a plurality of transmissive data pieces and confronting data pieces at certain angle intervals, and performing the restructuring process after an interpolating computation. CONSTITUTION:The contrast data and confronting data within a range of distance according to the sensor laying pitch are read centering on the position of the section set by a section setting part 22, and the result is fed to an interpolation processing unit 23. The corresponding contrast data and confronting data for the same rotational angle are subjected to distance interpolation according to the distance from the position of the set section, to serve for preparation of the weighted mean data. i.e., the presumative values of the contrast data in the position of the section. The global angular weighted mean data given from the unit 23 is fed to a restructuring processing unit 24, and the two-dimensional distribution of CT values, i.e., the tomographic image, is restructured from the global angular weighted mean data. The obtained tomographic image is supplied to the output unit 25 and also displayed or stored.

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 projection data of a cross section of a subject at all angles.

[0002]

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

This helical scan has the following problems. In the helical scan, the rotation angle (hereinafter simply referred to as an angle) of the rotary gantry at the time of acquisition periodically changes, and the slice axis parallel to the body axis of the subject (hereinafter referred to as Z axis).
The collection position (hereinafter referred to as the Z position) continuously changes along the line. 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 of this cross sectional position is divided into the front and back of the Z position of this cross sectional position. It is necessary to create 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 an opposite beam interpolation method.

The simple interpolation method requires projection data for two rotations around the reconstructed cross section position. The projection data for two rotations is distance-interpolated to the projection data for one rotation. Distance interpolation is the same angle but two different Z positions.
It is a process of weighted averaging two data according to the distance from the cross-section position. A tomographic image of the cross section is reconstructed from the projection data (weighted average data) for one rotation thus obtained.

As described above, in the helical scan, the all-angle projection data necessary for reconstructing one tomographic image is the distance that the subject (top plate) moves while the rotary gantry makes two rotations. Since they are dispersed in the range, that is, the effective slice thickness is large, the reliability of the tomographic image must be low.

The counter-beam interpolation method was developed to alleviate this problem. The opposed beam interpolation method is a position where angles are different by 180 °, that is, projection data collected at each opposed position theoretically contains the same tissue information (X-ray absorptance information). Therefore, the projection data collected at a certain Z position is treated as projection data at the same Z position and an angle of 180 ° (hereinafter referred to as opposing data). In such an opposed beam interpolation method, all the angular projection data necessary for reconstructing one tomographic image is obtained by subjecting the object (top plate) to one rotation of the rotary gantry.
Are distributed in the range of moving distance, the effective slice thickness can be reduced to 1/2 as compared with the simple interpolation method, and the reliability of the tomographic image can be theoretically doubled.

However, in the opposite beam interpolation method, only half of the reconstructed data is actually collected data (the other half is opposite data obtained by diverting the actually collected data). Therefore, there is a problem that 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 An object of the present invention is to reduce the distance dispersion of the collection positions where all the angular data necessary for reconstructing one tomographic image is reduced, and to perform the distance interpolation. To provide 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 a helical scan type X-ray computer tomography apparatus which realizes a combination of improvement of low contrast resolution by reducing image noise and high spatial resolution in the body axis direction by thin effective slice thickness. Is to provide.

[0010]

According to a first aspect of the present invention, an X-ray source for irradiating X-rays and an object to be irradiated with the X-rays are relatively rotated, and the X-ray source and the X-ray source are provided. By moving the subject relative to the subject along the body axis direction of the subject, a spiral scan is performed on the subject, and X-rays transmitted through the subject are detected by the X-ray detector array. In an X-ray computed tomography apparatus capable of reconstructing a tomographic image at a desired reconstruction cross-sectional position in the body axis direction by detecting, n rows (n is 2 or more) along the body axis direction of the subject. An integer) of X-ray detectors that are arranged in parallel and collect transmission data by the transmission X-rays of the subject during the spiral scan, and data of an arbitrary rotational phase detected by the X-ray detectors. Each of the above X-ray detectors is provided with the counter data in the rotational phase opposed to the X-ray detector. Opposing data generating means for generating each, first data corresponding to the collection position closest to the reconstructed cross-section position, and the opposite side across the reconstructed cross-section position with respect to the collection position of the first data. Data extraction means for selectively extracting a set of second data corresponding to a collection position closest to the reconstruction cross-sectional position in the region from the transmission data and the opposing data at predetermined angles, and the data extraction Based on the projection data obtained by the interpolation calculation means, and interpolation calculation means for obtaining projection data at the reconstructed cross-section position by performing interpolation calculation based on the first and second data extracted by the means. Reconstructing means for reconstructing a tomographic image at the reconstruction cross-section position.

According to a sixth aspect of the present invention, the X-ray source for irradiating the X-ray and the subject to be irradiated with the X-ray are relatively rotated,
In addition, the X-ray source and the subject are relatively moved along the body axis direction of the subject, thereby performing a spiral scan on the subject, and X passing through the subject.
In an X-ray computed tomography apparatus capable of reconstructing a tomographic image at a desired reconstruction cross-sectional position in the body axis direction by detecting X-rays with an X-ray detector array, in the body axis direction of the subject. A plurality of rows are arranged in parallel along the X-ray detector row for collecting transmission data by the transmission X-rays of the subject at the time of the spiral scan, and a first collection row corresponding to a collection position closest to the reconstruction cross-section position. A set of data and a second data corresponding to a collection position closest to the reconstruction cross-section position in a region opposite to the collection position of the first data across the reconstruction cross-section position is set forth above. Data extraction means for selectively extracting from each transmission data obtained by the X-ray detector array, and the first data extracted by the data extraction means.
And an interpolation calculation means for obtaining projection data at the reconstructed cross-section position by performing an interpolation calculation based on the second data, and a slice at the reconstructed cross-section position based on the projection data obtained by the interpolation calculation means. Reconstructing means for reconstructing an image.

According to the invention of claim 11, an X-ray source for irradiating X-rays and an object to be irradiated with the X-rays are relatively rotated, and the X-ray source and the object to be inspected. By relatively moving the specimen along the body axis direction, a spiral scan is performed on the subject, X-rays that pass through the subject are detected by an X-ray detector, and the detected data is used. In an 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.
Multi-channel X-ray detectors 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 each of the X-rays for spiral scanning.
Make sure that the traces of the data detected by the line detector do not overlap.
The X-ray source includes a control unit that controls a movement pitch at which the X-ray source and the subject relatively move while the X-ray source makes one rotation.

[0013]

According to the first aspect of the present invention, the first data corresponding to the collection position closest to the reconstructed section and the opposite side of the reconstructed section with respect to the collection position of the first data. A set consisting of the second data corresponding to the collection position closest to the reconstruction cross section in the area is selected from a plurality of transmission data and counter data for each predetermined angle, and subjected to reconstruction processing after interpolation calculation. Sent. 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.

The invention of claim 6 can obtain the same operation as that of the invention of claim 1, but so-called counter beam interpolation is not adopted. Therefore, in the invention of claim 6, the reliability of the tomographic image is improved in a range not as large as that of the invention of claim 1.

According to the eleventh aspect of the present invention, since the density of the detected data increases in the body axis direction, the image can be reconstructed from only the actually detected data. Therefore, the image noise can be suppressed while suppressing the increase of the effective slice thickness. It is possible to improve low contrast resolution by reducing

[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 block diagram of an X-ray computer tomography apparatus according to the first embodiment of the present invention. Figure 2
(A) is a front view of the rotary mount of FIG. FIG. 2B is a perspective view showing the arrangement relationship between the X-ray source and the multi-channel type X-ray detector array. FIG. 2C is a diagram of the multi-channel X-ray detector array viewed from the X-ray source side.

The rotary mount 1 comprises an X-ray source 2 and a multi-channel detector array 4 consisting of n rows (n is an integer of 2 or more, where n = 3) of multi-channel detectors 31 to 33. Hold. The multi-channel detectors 31 to 33 are arranged so as to face the X-ray source 2 with the imaging area E interposed therebetween. The X-ray source 2 irradiates a cone beam X-ray from a focus F. Each of the multi-channel type detector arrays 31 to 33 includes a plurality of X-ray detecting elements 6 arranged along the rotation trajectory of the X-ray source 2. Each X-ray detection element 6 independently detects the transmitted X-ray that has passed through the subject. Multi-channel detector 31
3-3 are arranged in parallel at a predetermined pitch P2 along the subject axis perpendicular to the plane of rotation of the X-ray source 2. Each X-ray detection element 6
Respectively independently convert the X-rays that have passed through the subject into electric signals (detection signals) according to their intensities. There are cases where the detection signals of the individual X-ray detection elements 6 correspond to one channel, and cases where the addition of the detection signals of a prescribed number of adjacent X-ray detection elements 6 corresponds to one channel. In the following, for convenience of description, the former will be described, but the latter possibility is not denied.

As a modification, the rotary mount 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 orbits of the X-ray source 2 which are opposed to each other with the center of rotation interposed therebetween. Here, the former case in which the X-ray source 2 and the multi-channel type detectors 31 to 33 rotate together will be described.

The gantry driving mechanism 7 drives and rotates the rotary gantry 1. Further, the gantry driving mechanism 7 slides the rotary gantry 1 along the body axis of the subject. The bed 8 supports a top plate having a flat rectangular shape on which a subject is mounted so as to be slidable along its long axis. Along with the slide of the top plate, the subject is inserted into the imaging region E or pulled out from the imaging region E along the body axis thereof. The long side of the top of the bed is the rotation axis of the rotary base 1 (the axis passing through the rotation center C and perpendicular to the paper surface).
It will be installed in parallel with.

The X-ray control unit 9 is the high voltage generation unit 1
The control signal is output to 0. The high voltage (tube voltage) at the level indicated by this control signal is transmitted from the high voltage generation unit 10 to the X-ray source 2
Is applied to The X-ray source 2 emits X-rays having an intensity corresponding to the tube voltage.

The gantry / bed control unit 11 outputs control signals to the gantry drive mechanism 7 and the bed 8, respectively. The gantry drive mechanism 7 continuously drives the rotary gantry 1 to rotate at an angular velocity instructed 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 instructed by a control signal supplied from the gantry / bed control unit 11. The bed 8 continuously slides the tabletop at a speed instructed by a control signal input from the gantry / bed control unit 11. At least one of the rotary base 1 and the top plate is slid. As a result, the relative position between the rotary mount 1 and the subject continuously changes along the body axis of the subject. Note that, here, it is assumed that this relative position change is performed by stopping the sliding 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 detections 31 to 33 according to a predetermined sequence. As a result, the helical scan is executed. The gantry / bed control unit 11 controlled by the system control unit 12 continuously rotates the rotary gantry 1. The bed 8 controlled by the system control unit 12 continuously slides on the tabletop at least while the rotary gantry 1 is rotating. While the rotary gantry 1 is rotating, the X-ray control unit 9 controlled by the system control unit 12 controls the X-ray source 2 to emit X-rays continuously or intermittently.
A tube voltage is continuously or intermittently supplied to the radiation source 2. The multi-channel type detectors 31 to 33 controlled by the system control unit 12 determine the X-rays that have passed through the subject while the rotary mount 1 is rotating and the X-rays are being emitted from the X-ray source 2. 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 absorptances of various tissues existing on the path. The multi-channel detectors 31 to 33 convert the attenuated X-rays into electric signals having a level according to the intensity thereof. Therefore, the detection signals detected by the multi-channel type detectors 31 to 33 include the integral information of the X-ray absorption rates of the plurality of types of tissues existing on the path. This detection signal is digitally converted by the data acquisition unit 14 and is called projection data in the subsequent processing.

During the execution of the helical scan, the gantry / bed control unit 11 supplies the rotation angle of the rotary gantry 1 and the coordinates of the top (hereinafter referred to as the top position or simply the position) to the system control unit 12 at any time. . Therefore, 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 rotary gantry 1 from the counted number. Similarly, the bed 8 is also provided with a rotary encoder that outputs a pulse signal at a predetermined angle via a rack and pinion mechanism. The gantry / bed control unit 11 counts this pulse signal and measures the position of the tabletop from this count.

The system control unit 12 determines the timing at which the multi-channel detectors 31 to 33 detect the X-rays transmitted through the subject, that is, the rotation angle of the rotary mount 1 at the time when each detection signal is detected, and the ceiling. The position of the board (top coordinate),
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 31 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 is created in accordance with the output from the system control unit 12 like the one write address signal, but only the rotation angle of the rotary gantry 1 when the detection signal is detected is shifted by 180 °. Created by changing the rotation angle. That is, one detection signal is stored in two addresses. Considering the detection signal stored at one address as original data, the detection signal stored at the other address is treated as the opposite data of the original data.

The detection signals detected by the detectors of the multi-channel type detectors 31 to 33 are data collection units 14 respectively.
After being amplified and digitally converted by, the data is sent to the storage unit 15 independently. Data collection unit 14
The detection signal digitally converted in step S6 will be referred to as projection data hereinafter. The projection data of each detector of the multi-channel detectors 31 to 33 is stored in two addresses according to 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 rows of the multi-channel detector. The first memory 16 has projection data (original data) of the multi-channel detector 31 in the first row.
Are stored according to one address signal. First
′ The memory 17 has a multi-channel detector 31 in the first row.
Projection data is stored as counter data in accordance with the other address signal. The projection data (original data) of the multi-channel type detector 32 in the second row is stored in the second memory 18 according to one address signal. The projection data of the multi-channel type detector 32 in the second row is stored in the second 'memory 19 as the opposite data according to the address signal of the other side. In the third memory 20,
The projection data (original data) of the multi-channel detector 3 3 in the third column is stored according to one address signal. The projection data of the multi-channel detector 3 3 in the third column is stored in the 3'memory 21 as the opposite data according to the other address signal.

In this embodiment, it is not necessary to adopt the counter beam interpolation method. In this case, in order to obtain the same effect as in the case where the above-mentioned counter beam interpolation method is adopted, the number of rows (2 × n) that is twice the number n of rows of the X-ray detector described above is required.

The system control unit 12 is connected to a cross-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 regarding projection data to be read from the storage unit 15, based on the cross section 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. By this read address signal, projection data required for distance interpolation is selectively read from the storage unit 15.

Specifically, two sets of projection data are selected for each of the rotation angles of 0 ° to 360 ° (the two corresponding projection data having the same rotation angle are treated as one set). It For example, the rotary mount 1
If the detection operation of the detectors 31 to 33 is repeated every 2 ° of rotation of 0 °, 0 °, 2 °, 4 ° ... 354
For each rotation angle of °, 356 °, 358 °,
Two detection signals are selected. Two pieces of projection data, which correspond to each other and have the same rotation angle, constitute one set
A region on the opposite side of the position of the first projection data corresponding to the position closest to the position of the cross section set in 2 and 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 other words, the projection data corresponding to the position closest to the cross-sectional position is read in each of the two regions across the cross-sectional position set by the cross-section setting unit 22.

As a result, the projection data selectively read out from the storage unit 15 is centered on the position of the cross section set by the cross section setting section 22 and within each range of a predetermined pitch of the detectors 31 to 33. It corresponds 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 projection data corresponding to the same rotation angle according to the distance from the cross-section position set by the cross-section setting unit 22, and calculates weighted average data. . This weighted average data is obtained by the section setting unit 22.
It is handled as projection data at the cross-sectional position set in. This distance interpolation processing is repeated for all rotation angles, and all-angle weighted average data corresponding to each rotation angle from 0 ° to 360 ° is obtained.

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

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

In the first embodiment, projection data is collected by helical scanning. Further, in the present embodiment, projection data of all angles on the cross section are prepared by the counter beam interpolation processing method. Since the helical scan and the counter 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 continuously rotates the rotary gantry 1. The bed 8 controlled by the system control unit 12 continuously slides on the tabletop at least while the rotary gantry 1 is rotating.
While the rotary base 1 is rotating, the system control unit 1
The X-ray control unit 9 controlled by 2 controls the X-ray source 2 from the X-ray source 2.
A tube voltage is continuously or intermittently supplied to the X-ray source 2 in order to continuously or intermittently irradiate the line. Multi-channel detector 3 controlled by system control unit 12
1 to 33, the rotary base 1 rotates and the X-ray source 2 moves to X.
The X-rays that have passed through the subject are repeatedly detected at a predetermined cycle while the radiation is being emitted.

The X-rays emitted from the X-ray source 2 are attenuated by the tissues on the path, and the multi-channel type detectors 31 to 33.
Is detected by each of the detection elements 6. While the helical scan is being executed, the system control unit 12 causes the memory controller 31 to detect the timing at which 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 rotary base 1, the position of the top plate (top plate 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
When the detection signal of a certain channel of 1 is detected, the rotation angle θa of the gantry 1 and the position Pa of the top when the detection signal is detected are stored in the memory controller 31 together with the channel number and the detector number. Supplied. The memory controller 31 separately supplies two kinds of write address signals corresponding to the rotation angle θa, the position Pa of the top plate, the channel number, and the detector number to the first memory 17 and the first ′ memory 18, respectively. . One write address signal is created according to the rotation angle θa, the position Pa of the top plate, the channel number, and the detector number. The other write address signal is a rotation angle (θa + 180 °) obtained by shifting the rotation angle θa by 180 °, the position Pa of the top plate,
It is created according to the channel number and the detector number. That is, the two same projection data are stored as addresses, one of which is the original data and the other of which is the opposite data, only at corresponding different rotation angles. Detection signals detected at other timings are similarly stored. Detection signals detected on other channels are also stored in the same manner. The detection signals detected by the other multi-channel type detectors 32 and 33 are similarly stored.

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 the helical scan. The solid line shows the changes in the collection position and the rotation angle of the plurality of pieces of opposing data, and the thin line shows the change. In FIG. 4, P1 indicates the distance (top feeding pitch) that the top moves during one rotation of the rotary base 1, and P2 indicates the distance between the width centers of adjacent detectors, that is, the detector pitch, P
Reference numeral 3 indicates a data pitch according to the counter beam interpolation method. As shown in FIG. 4, the opposite data sequence of a certain detector is
It is an important requirement of the invention, that of the projection data necessary to reconstruct a tomographic image, that a helical scan be performed so that it lies between the two original data trajectories of the other two detectors. 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. In order to realize this, it is necessary to execute the helical scan under the following conditions. This condition is slightly different when the number of rows n of the multi-channel detector row 4 is odd and even.

When the number n of the multi-channel detector rows 4 is an odd number, the system control unit 12 controls the gantry / bed control unit 11 so as to satisfy the following expression (1). P1 = n × P2 (1) That is, the distance P1 that the top plate moves while the rotary gantry 1 makes one revolution, in other words, the rotary gantry 1 and the subject relatively change while the rotary gantry 1 makes one revolution. The distance P1 to be reached is the detector 3
The system control unit 12 relatively determines the rotational angular velocity of the rotary gantry 1 and the movement of the tabletop so as to match the entire width (n × P2) of 1 to 3 3.

When the number n of the multi-channel detector rows 4 is an even number, the system control unit 12 controls the gantry / bed control unit 11 so as to satisfy the following expression (2). P1 = (n−1) × P2 (2) That is, the distance P1 that the top plate moves while the rotary gantry 1 makes one rotation, in other words, the rotary gantry 1 and the subject are separated while the rotary gantry 1 makes one rotation. The distance P1 which changes relatively is the detector 3
Distance obtained by subtracting the parallel pitch P2 from the total width of 1 to 33 ((n
−1) × P2) so that the rotational angular velocity of the rotary gantry 1 and the movement of the top plate are relatively controlled by the system control unit 1.
Determined by 2. In this case, the trajectory of the nth detector in the last row coincides with the trajectory of the first detector in the front row, and the existence of the nth detector is meaningless. Therefore, ideally, the number of rows n of the multi-channel detector row 4 is n.
Is an odd number from the viewpoint of cost performance, but does not mean that even if the number n of the multi-channel detector rows 4 is an even number, it is less effective than when it is an odd number.

The memory controller 31 creates two write address signals for the projection data of one channel 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.
Although it is created according to the output from, 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, the rotation angle of the first memory 16, the top position in this case, the channel number, and the detection signal stored at the address of the column number, for example. The same thing is the first as the opposite data.
It is stored in the memory 17 at the rotation angle, the top plate position in this case, the channel number, and the address of the column number.

After the helical scan is completed, or during the execution of the helical scan, the cross section setting section 22 is used to
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 and the facing data to be read from the storage unit 15, based on the position of the cross section set by the cross section setting unit 22.

Based on the data of this position range, the detector 31 is centered on the position of the cross section set by the cross section setting unit 22.
A range of parallel pitches P2 of ~ 3 3 is specified. FIG. 5 is a diagram corresponding to FIG. 4, in which the distributions of projection data and counter data read from the storage unit 15 are indicated by thick lines. 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 cross section set by the cross section setting section 22.
All projection data and counter data within the distance range of 2 are read from the storage unit 15. As mentioned above, so that the counter beam train of one detector lies between the distributions of the two original data of the other two detectors,
Since the helical scan is being executed, the projection data and the counter data that are read out are the results that are read out according to the following rules.

That is, two sets of projection data (including opposing data) are selected for each of the rotation angles of 0 ° to 360 °. For example, assuming that the detection operations of the detectors 31 to 33 are repeated every time the rotary base 1 rotates by 2 °, 0 °, 2 °, 4 °, ... 354 °,
Two sets of projection data (including opposing data) are selected for each rotation angle of 356 ° and 358 °. Moreover,
The two projection data corresponding to the same rotation angle are the first projection data corresponding to the position closest to the position of the cross section set by the cross section setting unit 22, and the cross section setting for the position of the first projection data. The second projection data corresponds to the position closest to the position of the cross section set by the cross section setting unit 22 in the region on the opposite side of the position of the cross section set by the section 22.

The projection data and the opposing data thus selectively read from the storage unit 15 are sent to the interpolation processing unit 23. The interpolation processing unit 23 performs distance interpolation (weighted average) on the two projection data and the counter data corresponding to the same rotation angle according to the distance from the position of the cross section set by the cross section setting unit 22, and the weighted average. Data, that is, an estimated value of 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 processing shown in FIG.
It is a figure which extracts and shows only the thick line part. As shown in FIG. 6, for example, regarding the rotation angle θα, from the two projection data D1 and D2 of the rotation angle θα, the projection data D3 on Z0 of the rotation angle θα is calculated by the equation (3). . Incidentally, 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.

D3 = (a × D1 + b × D2) / 2 (3) This distance interpolation processing is repeated for each rotation angle and corresponds to each rotation angle from 0 ° to 360 °. The weighted average data for all angles are calculated.

The all-angle weighted average data from the interpolation processing unit 23 is sent to the reconstruction processing unit 24.
The 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 of all angles. This tomographic image is supplied to the output unit 25 and is displayed or stored.

As described above, according to the first embodiment, the spread (effective slice thickness) relating to the position of the projection data necessary for reconstructing the tomographic image is determined by the conventional one having one X-ray detection line, or the X-ray detection line having one line. It is possible to improve the spatial resolution in the body axis direction by making it significantly narrower than the case where there are a plurality of line detection rows and the movement speed of the top plate with respect to the rotational angular velocity of the rotary gantry is not controlled as described above. it can. Conventionally, this spread is
Distance P1 x 2 of the top that moves during one rotation of the rotary mount
The spread is P1 even in the conventional case where the opposed beam interpolation method is adopted. On the other hand, that of the present invention is P2, that is, the detector pitch, and P2 is P1 / n (n
Is the number of columns). (Second Embodiment) A second embodiment will be described below with reference to the drawings. FIG. 7 is a block diagram of the second embodiment. In FIG. 7, the same parts as those in FIG. In this embodiment, data of an effective slice thickness equal to or less than that in the first embodiment is realized from only original data (without using opposite data), and the occurrence of image noise due to the use of opposite data is eliminated. To do.

The rotary mount 1 comprises an X-ray source 2 and n-row (here, n = 10) multi-channel detectors 31 and 32.
The multi-channel detector array 4 consisting of 3n is arranged so as to face each other across the shooting area, and is held rotatably with respect to the center of the shooting area while maintaining this facing relationship. The X-ray source 2 emits cone-beam X-rays from the focal point. .. 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 surface 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 of them is provided with a plurality of detection elements arranged side by side at an equidistant relationship from the focal point of the X-ray source 2 within the plane of rotation of the X-ray source 2. The detection elements are independent of each other
The wire is converted into an electric signal according to its strength. For example, 1
One detection element or a predetermined number of adjacent detection elements corresponds to one channel. It should be noted that a so-called fourth generation structure in which only the X-ray source 2 is held on the rotary mount 1 and the multi-channel detector array 4 for one round is fixed at a position for receiving the X-rays from the X-ray source 2 Good.

The gantry driving mechanism 7 drives and rotates the rotary gantry 1. The bed 8 supports a top plate 29 on which a subject is mounted so as to be slidable along its longitudinal direction. The bed driving mechanism 26 drives and slides the top plate 29, and moves the subject in and out of the imaging region along the body axis direction (same as the longitudinal direction of the top plate 29). As a result, the positions of the imaging region and the subject are relatively changed. 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 opposite directions, so that the imaging region and the subject are separated from each other. A mechanism that changes the relative positional relationship may be adopted.

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

The gantry / bed control unit 11 sends control signals to the gantry drive mechanism 7 and the bed drive mechanism 26, respectively.
The gantry driving mechanism 7 rotates the rotary gantry at a constant speed at an angular velocity designated by a control signal supplied from the gantry / bed control unit 11. The bed driving mechanism 26 slides the table 29 of the bed 8 at a constant speed at a speed designated by a control signal supplied from the gantry / bed control unit 11. Here, the distance that the top plate 29 slides during one rotation of the rotary mount 1, that is, the X-ray source 2, is defined as the top plate feed pitch d.
Define 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 to execute a helical scan. The gantry / bed control unit 11 controlled by the system control unit 12 continuously rotates the rotary gantry 1 at a constant angular velocity and, at the same time, slides the table 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 continuously or intermittently generates X-rays from the X-ray source 2. Each detection element of the multi-channel detector array 4 controlled by the system control unit 12 converts the X-rays transmitted through the subject into an electric signal of a level corresponding to the intensity thereof at a predetermined cycle (for example, the X-ray source 2 is 2 °). 1 time to rotate
Data collection unit 1
4 is output. The data acquisition unit 14 controlled by the system control unit 12 sequentially converts the electric signal converted in each channel of the multi-channel detector array 4 into digital data.

During the helical scan, the gantry / bed control unit 11 controls the rotation angle of the rotary gantry 1 and the top plate 2.
The coordinates of 9 (top position) are the system control unit 12
Will be taken in at any time. For this purpose, the rotary gantry drive mechanism 7
Is provided with a rotary encoder (not shown) that generates a pulse signal for each predetermined angle, and the gantry / bed control unit 11 counts the pulse signal to measure the rotation angle. Similarly, the tabletop 29 is provided with a rotary encoder (not shown) via a rack and pinion mechanism, and generates a pulse signal every time the tabletop 29 slides a predetermined distance, and the gantry / bed control unit 11 outputs the pulse signal. The signal is counted and the position of the top board is measured.

The system control unit 12 controls the rotation angle of the rotary mount 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 detection data, and the multi-channel type X. Line detectors 31 to 3
n A unique detector number for each memory controller 1
Output to 3. The memory controller 13 includes a rotation angle from the system control unit 12, a position of the top board 29,
A write address signal is created according to the channel number and the detector number and is 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 in 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 cross section setting section 22 for designating 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 of the reconstructed cross-section position set by the cross-section setting unit 22 to the memory controller 13 together with the data read command. According to this information, the memory controller 13 creates a read address signal and supplies it to the storage unit 15. By this read address signal, the data necessary for the reconstruction of the tomographic image regarding the reconstruction cross-section position is selectively read from the storage unit 15. Specifically, two pieces of 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 the two data is 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 reconstructed with respect to the Z-axis. It is data corresponding to the Z position closest to the reconstructed cross section position in the region on the minus side of the composed cross section position.

This is a condition when only so-called interpolation interpolation (interpolation in which the Z position of the interpolation data is sandwiched between the Z positions of two original data) is used. As a modified example, the extrapolation interpolation is performed. When (interpolation in which the Z position of the interpolated data is not sandwiched between the Z positions of the two original data) is also used with the interpolation interpolation, simply the two data with the same rotation angle are reconstructed regardless of the region. Two pieces of data are provided in the order closest to the cross-sectional position.

The data read from the storage unit 15 two by two 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) according to the distance from the reconstruction cross-section position,
Is added. As a result, weighted average data (interpolation data) of the rotation angle related to the reconstructed cross-section position is created. The creation of this interpolation data is executed for every rotation angle, and finally the weighted average data for all rotation angles is obtained.

Based on the weighted average data for all of these angles, the reconstruction processing unit 24 reconstructs a two-dimensional distribution (tomographic image) of CT values for the reconstruction 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 assuming that the number of columns of the multi-channel type detectors 31 to 3n is 10, that is, n = 10. 8 and 9 show the rotary mount 1.
Is represented by the trajectory of the projection data collected by each of the multi-channel type detectors 31 to 310, that is, the Z position of the top plate 29 and the rotation angle of the rotary mount 1 when each data is collected. 8 shows a trajectory, and the setting mode of the top 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. It should be noted that the distance (detector pitch) on the Z axis between the width centers of adjacent multi-channel detectors is p, and the rotary mount 1 (X-ray source 2)
Let d be the moving distance (top feed pitch) of the top 29 that moves during one rotation of. FIG. 8 shows the case where d = 4.5 × p.

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

In any setting mode, the rotary base 1 is set to 1
Each time it rotates, the Z position of the data shifts by p / 2 in the setting mode of FIG. 8 and the Z position of the data shifts by p / 3 in the setting mode of FIG. The table feed pitch d is set so that the data loci of the multi-channel detectors 31 to 310 do not overlap. This makes it possible to increase the density of original data (actually collected actual data that is not the opposite data) that is the source of the weighted average data of the reconstruction cross-section positions. Therefore, the image noise is reduced by creating the weighted average data only from the original data without using the opposing data, and further, the pitch P of the original data is narrowed to reduce the effective slice thickness, and the spatial resolution in the body axis direction is reduced. It is possible to obtain a high image.

In the case of FIG. 8, 10 columns (n = 10) of multi-channel type detectors 31 to 310 are installed and the detector pitch p is set.
The top plate 29 is slid at a top plate feed pitch of 4.5 times (d = 4.5 × p). As a result, the data pitch P
Can be p / 2. Further, 10 rows (n = 10) of multi-channel type detectors 31 to 310 are installed, and the top plate feed pitch is 10/3 times the detector pitch p (d = (10/3) × p).
The top plate 29 is slid by. As a result, 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, the simple interpolation method is adopted here instead of the opposed beam interpolation method. Consider a case in which weighted average data corresponding to a rotation angle of, for example, 90 ° is obtained for the reconstructed cross-section position set by the operator via the cross-section setting unit 22. The two projection data which are the basis of the weighted average data regarding the rotation angle of 90 ° are the data a (2 of the multi-channel detector 37 in the 7th column) closest to the reconstruction cross-section position in the area A on the left side of the reconstruction cross-section position. The data of the rotation angle 90 ° obtained at the rotation) and the data b (the third rotation of the multi-channel detector 3 3 in the third row) closest to the reconstruction cross-sectional position in the area B on the right side of the reconstruction cross-section. The obtained rotation angle is 90 °). From these data a and b, the weighted average data x at the rotation angle of 90 ° at the reconstruction cross-section position is obtained by distance interpolation. By performing this process individually for all the rotation angles at the reconstruction cross-section position, data of all angles (interpolation data or weighted average data) necessary for the reconstruction process at the reconstruction cross-section position can be obtained. Become. That is, the original data exists in the portion shown by the thick line in FIG. 10, that is, before and after the reconstruction cross-section position as the center, and in the range of p / 2 each, in other words, p around the reconstruction cross-section position. The range can be limited (narrowed). Similarly, in the case of FIG. 9, the original data is centered on the reconstruction cross-section position and before and after it, in the range of p / 3, in other words, on the reconstruction cross-section position (2/3).
It can be limited (narrowed) to the range of xp.

When this is generalized, it can be expressed as follows. Top plate feed pitch d is d = p × (L + 1 / m), where p: detector pitch n: number of rows of multi-channel X-ray detectors m: natural number L: satisfies an integer less than (n / m) Under the condition that the table top feed pitch d is arbitrarily adjusted via the mode setting device, the data pitch P
Can be P = p / m. Here, when the opposite beam interpolation is not used and only the interpolation interpolation of the simple interpolation method is used, the projection data necessary for reconstruction should be limited to the range (effective slice thickness) of (2 × p) / m. You can In the case of FIG. 8, the effective slice thickness is p, and in the case of FIG. 9, the effective slice thickness is (2 /
3) xp. When the weighted average data is obtained from this projection data, the original projection data is all the original data actually collected and is not the opposite data. The noise is excellent, and the image quality equivalent to simple interpolation can be obtained. The pitch of projection data is p / m
And 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, of course, the opposed beam interpolation method may be applied. For example, FIG. 11 shows a data locus when the counter beam interpolation method is applied under the conditions of FIG. In this case, the data pitch is p / 2m. Image noise increases as compared with the simple interpolation method because one of the projection data for obtaining the weighted average data is the opposite beam, but the effective slice thickness is further reduced by the reduction of the data pitch.

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

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications. For example, in the above-described embodiment, since the tabletop feed speed is slowed down, an artifact may occur when the scan time is long and an image of a fast-moving part is taken, or when the subject's respiration or the like causes severe movement. there were. In order to avoid this problem, it is important to properly avoid this problem by being able to select a mode in which the tabletop can be slid at high speed without being limited by the conditions of the tabletop feed pitch described above. Is.

[0073]

According to the invention of claim 1, the X-ray source for irradiating X-rays and the subject to be irradiated with the X-rays are relatively rotated, and the X-ray source and the subject are rotated. By moving the subject relatively along the body axis direction, a spiral scan is performed on the subject, and X-rays passing through the subject are detected by an X-ray detector array. In an X-ray computed tomography apparatus capable of reconstructing a tomographic image at a desired reconstruction cross-sectional position in the body axis direction, n columns (n is an integer of 2 or more) are arranged in parallel along the body axis direction of the subject. Then, the X-ray transmission of the subject during the spiral scan is performed.
X-ray detector array for collecting transmission data by X-ray,
Opposed data generation means for generating, for each X-ray detector row, opposed data having an opposite rotational phase with respect to data of an arbitrary rotational phase detected by the line detector row, and at the reconstructed cross-section position. The first data corresponding to the nearest collection position and the first collection position corresponding to the collection position closest to the reconstruction cross-section position in the region on the opposite side of the collection position of the first data with respect to the reconstruction cross-section position. Data extraction means for selectively extracting a set of two data from the transmission data and the opposing data at a predetermined angle, and interpolation based on the first and second data extracted by the data extraction means. Interpolation calculation means for obtaining projection data at the reconstructed cross-section position by performing computation, and reconstructing a tomographic image at the reconstructed cross-section position based on the projection data obtained by the interpolation calculation 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 cross section and the opposite side of the acquisition position of the first data across the reconstruction cross section. A set consisting of the second data corresponding to the collection position closest to the reconstruction cross section in the area is selected from a plurality of transmission data and counter data for each predetermined angle, and subjected to reconstruction processing after interpolation calculation. Sent. 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 invention, the X-ray source for irradiating the X-ray and the subject irradiated with the X-ray are relatively rotated,
In addition, the X-ray source and the subject are relatively moved along the body axis direction of the subject, thereby performing a spiral scan on the subject, and X passing through the subject.
In an X-ray computed tomography apparatus capable of reconstructing a tomographic image at a desired reconstruction cross-sectional position in the body axis direction by detecting X-rays with an X-ray detector array, in the body axis direction of the subject. A plurality of rows are arranged in parallel along the X-ray detector row for collecting transmission data by the transmission X-rays of the subject at the time of the spiral scan, and a first collection row corresponding to a collection position closest to the reconstruction cross-section position. A set of data and a second data corresponding to a collection position closest to the reconstruction cross-section position in a region opposite to the collection position of the first data across the reconstruction cross-section position is set forth above. Data extraction means for selectively extracting from each transmission data obtained by the X-ray detector array, and the first data extracted by the data extraction means.
And an interpolation calculation means for obtaining projection data at the reconstructed cross-section position by performing an interpolation calculation based on the second data, and a slice at the reconstructed cross-section position based on the projection data obtained by the interpolation calculation means. Reconstructing means for reconstructing an image.

According to the invention of claim 6, the same operation as that of the invention of claim 1 can be obtained, but so-called counter beam interpolation is not adopted. Therefore, in the invention of claim 6, the reliability of the tomographic image is improved in a range not as large as that of the invention of claim 1.

According to an eleventh aspect of the present invention, an X-ray source for irradiating X-rays and an object to be irradiated with the X-rays are relatively rotated, and the X-ray source and the object to be inspected. By relatively moving the specimen along the body axis direction, a spiral scan is performed on the subject, X-rays that pass through the subject are detected by an X-ray detector, and the detected data is used. In an 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.
Multi-channel X-ray detectors 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 each of the X-rays for spiral scanning.
Make sure that the traces of the data detected by the line detector do not overlap.
The X-ray source includes a control unit that controls a movement pitch at which the X-ray source and the subject relatively move while the X-ray source makes one rotation.

According to the eleventh aspect of the present invention, since the density of the detected data increases in the body axis direction, the image can be reconstructed from only the actually detected data. Therefore, while suppressing the increase of the effective slice thickness, the image noise is suppressed. It is possible to improve low contrast resolution by reducing

[Brief description of drawings]

FIG. 1 is a configuration diagram of an X-ray computer 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 the detection data and the oncoming data in X
The figure shown for every line detector.

FIG. 4 is a diagram showing a collection trajectory of all detection data and this opposite data.

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

FIG. 6 is a diagram for explaining a distance interpolation method.

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

FIG. 8 is a diagram showing a collection trajectory of detection data for three rotations under the 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 diagram showing detection data for three rotations and a collection trajectory of counter data under the first condition when the second embodiment is applied to the counter beam method.

[Explanation of symbols]

1 ... Rotating mount, 2 ... X-ray source, 31 to 3n ... Multi-channel type X-ray detector, 6 ... X
Line detection element, 7 ... Frame drive mechanism,
8 ... Bed, 9 ... Bed and bed control unit,
10 ... High-voltage generating unit, 11 ... X-ray control unit,
12 ... System control unit, 13 ...
Memory controller, 14 ... Data collection unit, 15 ... Storage unit,
16 to 21 ... Memory, 22 ... Section setting unit,
23 ... Interpolation processing unit, 24 ... Reconstruction processing unit, 25 ... Output unit.

Claims (18)

[Claims] 1. An X-ray source that irradiates X-rays and a subject to which the X-rays are irradiated are relatively rotated, and the X-ray source and the subject are in a body axis direction of the subject. By moving relative to the object, a helical scan is performed on the object, and the X-rays that pass through the object are detected by an X-ray detector to determine the desired direction in the body axis direction. In an X-ray computed tomography apparatus capable of reconstructing a tomographic image at a reconstruction cross-section position, n rows (n is an integer of 2 or more) are arranged in parallel along the body axis direction of the subject, and the helical scan is performed. A multi-channel type X-ray detector for collecting transmission data of the subject by transmission X-rays, and a counter having a rotation phase opposed to data of an arbitrary rotation phase detected by the X-ray detector. Data for each X
Opposing data generating means for generating each line detector, and a first corresponding to a collection position closest to the reconstruction cross-sectional position
And a second data corresponding to a collection position closest to the reconstruction cross-section position in a region opposite to the collection position of the first data with respect to the reconstruction cross-section position. Data extraction means for selectively extracting from the transmission data and the opposite data for each angle, and the reconstructed cross section by performing an interpolation operation based on the first and second data extracted by the data extraction means. X, comprising: interpolation calculation means for obtaining projection data at a position; and reconstruction means for reconstructing a tomographic image at the reconstruction cross-section position based on the projection data obtained by the interpolation calculation means. Line computer tomography equipment. 2. The X-ray computed tomography apparatus according to claim 1, wherein the number of rows n of the X-ray detector is set to an odd number. 3. The rotational phase is 1 by the spiral scan.
While the cycle changes, the relative positions of the X-ray source and the subject along the body axis direction may be displaced by a distance obtained by multiplying the parallel pitch of the X-ray detectors by the number of rows n. An X-ray computer tomography apparatus according to claim 2, characterized in that: 4. The X-ray computer tomography apparatus according to claim 1, wherein the number of columns n of the X-ray detector is set to an even number. 5. The rotational phase is 1 by the spiral scan.
During the periodic change, the relative positions of the X-ray source and the subject along the body axis direction are displaced by a distance obtained by multiplying the parallel pitch of the X-ray detectors by the number of rows n-1. The X-ray computer tomography apparatus according to claim 4, wherein 6. An X-ray source that irradiates X-rays and a subject to which the X-rays are irradiated are relatively rotated, and the X-ray source and the subject are in the body axis direction of the subject. By moving relative to the object, a helical scan is performed on the object, and the X-rays that pass through the object are detected by an X-ray detector to determine the desired direction in the body axis direction. In an X-ray computed tomography apparatus capable of reconstructing a tomographic image at a reconstruction cross-section position, a plurality of columns are arranged in parallel along the body axis direction of the subject, and the transmitted X-rays of the subject during the spiral scan. A multi-channel type X-ray detector for collecting transmission data by means of a first, which corresponds to a collecting position closest to the reconstructed sectional position
And a second data corresponding to a collection position closest to the reconstruction cross-section position in a region on the opposite side of the reconstruction cross-section position with respect to the collection position of the first data, Data extraction means for selectively extracting from the respective transmission data obtained by the X-ray detector, and interpolation processing based on the first and second data extracted by the data extraction means. It is characterized by further comprising: interpolation calculation means for obtaining projection data at the reconstruction cross-section position; and reconstruction means for reconstructing a tomographic image at the reconstruction cross-section position based on the projection data obtained by the interpolation calculation means. X-ray computer tomography device. 7. The X-ray computed tomography apparatus according to claim 6, wherein the number of columns of the X-ray detector is set to an odd number. 8. The rotational phase is 1 by the spiral scan.
While the cycle changes, the relative position of the X-ray source and the subject along the body axis direction is a distance obtained by multiplying the parallel pitch of the X-ray detectors by the number of rows of the X-ray detectors. 8. The X-ray computed tomography apparatus according to claim 7, wherein the X-ray computed tomography apparatus is displaced only by the distance. 9. The X-ray computed tomography apparatus according to claim 6, wherein the number of columns of the X-ray detector is set to an even number. 10. The relative position along the body axis direction between the X-ray source and the subject is parallel to the X-ray detector while the rotational phase changes by one cycle by the spiral scan. The X-ray computed tomography apparatus according to claim 9, wherein the pitch is displaced by a distance obtained by multiplying the number of columns of the X-ray detector by -1. 11. An X-ray source that irradiates X-rays and a subject to which the X-rays are irradiated are relatively rotated, and the X-ray source and the subject are in a body axis direction of the subject. By moving relative to the subject, a spiral scan is performed on the subject, X-rays transmitted through the subject are detected by an X-ray detector, and the detection data is used to detect the direction of the body axis. In an X-ray computed tomography apparatus for reconstructing a tomographic image at a desired reconstruction cross-section position, a multi-channel type in which n rows (n is an integer of 2 or more) are arranged in parallel along the body axis direction of the subject. An X-ray detector, a moving unit that relatively moves the positional relationship between the X-ray source and the subject in the body axis direction, and the trajectories of the data detected by the X-ray detectors during the spiral scan are overlapped. The X-ray source during one revolution so that An X-ray computer tomography apparatus comprising: a source and a control unit that controls a moving pitch at which the subject moves relatively. 12. The movement pitch d is d = p × (L + 1 / m), where p is a distance between width centers of adjacent X-ray detectors, n is the number of rows of the X-ray detectors, and m is a natural number. 12. The X-ray computed tomography apparatus according to claim 11, wherein the conditional expression of an integer less than (n / m) is satisfied. 13. In the conditional expression of the moving pitch d,
The X-ray computed tomography apparatus according to claim 12, wherein m = 2. 14. In the conditional expression of the moving pitch d,
The X-ray computed tomography apparatus according to claim 12, wherein L is a maximum value of an integer less than (n / m). 15. The X-ray computer tomography according to claim 11, further comprising an interpolating unit that interpolates data on a reconstructed cross-section position by using detection data detected by the X-ray detector. apparatus. 16. An interpolating means for interpolating data on a reconstructed cross-section position using detection data detected by the X-ray detector and counter data relating to the detection data. The X-ray computer tomography apparatus according to item 11. 17. The reconstructed cross section by distance interpolation from two data detected at positions closest to the reconstructed cross section position from both sides centering on the reconstructed cross section position in the body axis direction. The X-ray computed tomography apparatus according to claim 15 or 16, which interpolates data on a position. 18. The method according to claim 15, wherein the interpolation means interpolates data on the reconstruction cross-section position by distance interpolation from two pieces of data in order of being closer to the reconstruction cross-section position in the body axis direction. 16. The X-ray computer tomography apparatus according to 16.