JP2003175029A - X-ray ct system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform scanogram imaging over a wide range at an optimal timing in a short time. <P>SOLUTION: An X-ray detection element stream in an X-ray detector 12 required for preparing scanogram images for a plurality of predetermined slice widths is selected and by using projection data from the selected X-ray detection element stream, the scanogram image is prepared. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus, and more particularly to imaging a scano image for positioning an imaging site and setting imaging conditions prior to imaging a tomographic image.

[0002]

2. Description of the Related Art Generally, when a subject is imaged by an X-ray CT apparatus, first, a scanogram which is an X-ray fluoroscopic image of a region within a predetermined range of the subject is obtained, and then this scanogram is used as a basis. Then, the slice position is positioned and the imaging conditions are set, and X-ray scanning is performed at this position to obtain a tomographic image. In order to obtain a scanogram, for example, as disclosed in Japanese Utility Model Laid-Open No. 61-82605, the X-ray tube and the X-ray detector are fixed without rotation, and the top plate on which the subject is placed is fixed to the subject. Irradiate X-rays while moving in the body axis direction.
A scanogram is created based on the projection data thus obtained.

When performing a scan for obtaining a tomographic image, the slice position is determined for this scanogram.
Then, the top plate on which the subject is placed is temporarily returned to the original position, and then the top plate is moved again to dispose the X-ray tube at the slice position determined for the subject, and the X-ray is taken at each position. X-ray irradiation is performed while rotating the tube around the subject. A tomographic image of the subject at each slice position is obtained based on the projection data obtained thereby. The X-ray CT apparatus at the time when the above invention was applied (November 2, 1984) was a single slice CT apparatus. This single slice CT
The apparatus includes an X-ray tube that irradiates a fan-shaped X-ray beam (fan beam) and an X-ray detector in which fan-shaped or linear M-channel (for example, 1000 channels) X-ray detection elements are arranged in a line. Have. This apparatus rotates an X-ray tube and an X-ray detector around a subject, and collects M data (for example, 1000 data) in one rotation (one scan).

Thereafter, a helical scan method is adopted in which the top plate is moved in the body axis direction (slice thickness direction) of the subject while continuously rotating the X-ray tube and the X-ray detector to collect tomographic data of the subject. An X-ray CT apparatus to be used has been proposed, and in recent years, a multi-slice CT apparatus has been put into practical use. The multi-slice CT apparatus is a two-dimensional array in which an X-ray tube that irradiates a conical X-ray beam (cone beam) and a plurality of M-channel X-ray detection elements are arranged in the body axis direction (M channel × N column). With X-ray detector, X-ray tube, source and X-ray
The line detector is rotated around the subject and one revolution collects M × N data. In capturing a scano image by a multi-slice CT apparatus, for example, Japanese Patent Laid-Open No. 11-7622
As shown in 3, the data output from the X-ray detection element of the X-ray detector is bundled in the column direction, and a scano image for one slice at the center position of the X-ray detector is generated based on the bundled data. ing.

[0005]

However, in the scanning of a scano image by a single-slice CT apparatus, only one slice's worth of data can be obtained in one scan, so the scanoscopic image in a wide range should be captured. Takes a long time (for example, about 10 seconds). Therefore,
There is a problem that it takes time to prepare a scan plan, which not only imposes a burden on the subject (patient) but also lowers the patient loop. In addition, since the subject is moved and imaged for each one-slice scan, the adjacent slices may overlap each scan, and the subject may be exposed to extra X-rays. Furthermore, the time for irradiating X-rays becomes long, which leads to shortening the life of the X-ray tube. On the other hand, multi-slice C
Even when scanning a scano image with the T-apparatus, since only one slice of scanodata was obtained in one scan, as with the single-slice CT machine, it takes time to scan a necessary range of scano-images. The X-ray irradiation time was getting longer. In order to solve such a problem, an object of the present invention is to make effective use of X-rays emitted from an X-ray tube so that a wide range scanogram can be captured in a short time.

[0006]

In order to solve the above-mentioned problems, the present invention detects an X-ray tube capable of irradiating an X-ray and an X-ray irradiated from the X-ray tube and transmitted through a subject. A plurality of X-ray detection elements, which are necessary to generate scanograms for a plurality of predetermined slice widths and X-ray detectors arranged in the channel direction and the body axis direction of the subject, respectively, A selection unit for selecting an X-ray detection element array in the body axis direction; and a scano image generation unit for generating a scano image using the data for the X-ray detection element array selected by the selection unit. It is a feature.

[0007]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings. In these figures, the same parts are designated by the same reference numerals. FIG. 1 is a schematic view showing a schematic configuration of an X-ray CT apparatus according to the present invention, and FIG. 2 is a block diagram showing a schematic configuration of the X-ray CT apparatus. This X-ray CT apparatus includes a gantry 1, a bed 2 arranged in front of the gantry 1, a gantry 1 and a bed 2.
And an operation console 3 for controlling each unit constituting the X-ray CT apparatus. On the upper surface of the bed 2,
The subject can be placed and the body axis direction (slice thickness direction)
A movable top plate 5 is provided, and the top plate 5 on which the subject is placed slides in the opening 4 of the gantry 1. The height of the bed 2 is adjusted and the top is moved (moving position and moving speed).
Can be controlled by operating the console 3. Console 3
An input device 6 and a monitor 7 including a keyboard, a pointing device such as a mouse, a trackball, and a joystick are arranged on the upper side, and a control unit 20 described later is provided in the console.

In the above X-ray CT apparatus, as shown in FIG. 2, the gantry 1 has an X-ray tube 11 and an X-ray detector 1 in it.
2 are supported by the rotating unit 13 so as to face each other with the subject P mounted on the top plate 5 interposed therebetween, and are continuously rotatable around the subject P. The drive of the rotation unit 13 is controlled by the rotation drive unit 14, and the rotation drive unit 14 is controlled.
Is based on the drive control signal from the control unit 20.
3 drive is controlled. The X-ray tube 11 is connected to a high voltage generator 16 via a slip ring, and the high voltage generator 16 supplies a tube current and a tube voltage at a predetermined timing based on an X-ray control signal from the control unit 20. Is supplied to the X-ray tube 11. Thus, a conical X-ray beam (cone beam) is generated from the focus of the X-ray tube 11.

Further, a diaphragm (collimator) is provided near the X-ray irradiation port in the gantry 1, and the X-ray beam from the X-ray tube 11 is shaped into a predetermined size to form a pyramidal X-ray beam. Is irradiated to the subject P as. The degree of this aperture can be controlled by the control unit 20. Then, the subject P
The X-rays that have passed through are detected by the X-ray detector 12. The X-ray detector 12 is a data acquisition system (hereinafter referred to as DAS) via a slip ring.
It is connected to 17. The DAS 17 is composed of an integrator that temporally integrates the output from each X-ray detection element, an A / D converter that converts the output of the integrator into a digital signal, and the like, and is supplied at a timing related to the generation of X-rays. Based on the data collection control signal from the control unit 20
Data is collected from each X-ray detection element.

A bed controller 15 is connected to the bed 2. The couch controller 15 can control the height of the couch 2 and the movement of the couchtop 5 based on a couch control signal from the controller 20, and, for example, intermittently moves the couchtop 5 to a desired slice position by a predetermined amount. It can be moved manually or continuously over a predetermined scan range.
Further, the bed control unit 15 is provided with a slide sensor that detects a movement amount (sliding amount) or a movement position (sliding position) of the tabletop 5, and the bed control unit 15 controls the slide value from the control unit 20. It has a function of controlling the movement of the tabletop 5 based on the (target value) and the current slide position detected by the slide sensor.

FIG. 3 is a diagram showing a schematic configuration of the X-ray detector 12. This X-ray detector 12 has one channel (c
h) Multiple segments per segment (40 se in this embodiment)
Two-dimensional detection in which g) are arranged in an array for a plurality of channels (1000 ch in this embodiment) along the channel direction (ch direction), the X-ray detection element rows arranged along the slice thickness direction (body axis direction). It is configured as a container. That is, the X-ray detector 12 of this embodiment shown in FIG.
This is a two-dimensional detector in which X-ray detection elements are arranged in a matrix of 00 ch × 40 columns. Also, X in the slice thickness direction
The pitch of the line detection elements is, for example, 1 mm, and the elements at the center to the elements at the ends are arranged at a uniform pitch (that is, the pitch of the X-ray detection element rows 12-1 to 12-40 is 1).
mm).

Next, the control section 20 provided in the console 3 will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the control unit 20. The control unit 20 controls X
It has a central function of controlling each part of the line CT apparatus and has a CPU 21 as a host controller. The CPU 21 has a built-in clock circuit 22, manages the operation and time of each unit using a clock from the clock circuit 22, and supplies this clock as a common clock to each unit in the control unit. CPU2
A control bus 23 and a data bus 24 are connected to the control bus 23.
5, a disk interface 26, a reconstruction unit 27, a scanogram image generation unit 28, and a display memory 29 are connected. Further, the data bus 24 has a preprocessing unit 25, a disk interface 26, a reconstruction unit 27, a scanogram image generation unit 28, a display memory 29, and a readable / writable DR.
A memory 30 such as AM is connected. A magnetic disk device 31 as a mass storage device is connected to the disk interface 26.

Further, a slice width (X-ray detecting element array) for scanning a scano image is set in advance, and when the scanographing mode is set, an X-ray for detecting data of the set slice width is set. The detector array is selected, and the DAS for collecting data is determined according to the selection so that only the data from the selected X-ray detector array is collected. A plurality of slice widths for scanography may be set in advance (for example, 4 rows), or a plurality of slice widths (for example, 4 rows, 8 rows, 16 rows) may be set in advance. The operator may be allowed to make a selection when instructing the scano photographing. As an external configuration of the control unit 20, the control bus 23 includes the input device 6, the rotation driving unit 14, the bed control unit 15, the high voltage generation device 16, and the above-described input device 6.
The DAS 17 is connected. Further, the DAS 17 is connected to the preprocessing unit 25, and the monitor 7 is connected to the display memory 29.

The operation of the X-ray CT apparatus configured as described above will be further described with reference to FIGS. 5 and 6. FIG. 5 is a diagram showing a situation of scano photographing in the first embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the movement of the tabletop and the X-ray irradiation timing during scanographing. First, the operator designates the scano photographing mode with the input device 6. Then, the CP that received the designation
U21 sends a control signal to the rotation drive unit 14 according to a preset condition, and the rotation drive unit 14 operates the X-ray tube 11 and the X-ray detector 12 based on the control signal, for example, as shown in FIG. Then, it is arranged at a position horizontal to the top plate 5. Further, with respect to the high voltage generator 16, the values of the tube voltage and the tube current suitable for the scanography are set.
Further, when the operator gives an instruction to move the tabletop 5 with the input device 6, the CPU 21 sends a control signal to the bed control unit 15 in response to the instruction, and the bed control unit 15 receives the control signal based on the control signal. The top plate 5 on which the sample P is placed is slid to the start position of scano imaging. Further, an X-ray detection element array corresponding to a preset slice width is selected, and D corresponding to the selected X-ray detection element array is selected via the control unit 20.
The drive of the DAS is controlled so that only the AS collects data.

After preparation for scanography, the input device 6
When an instruction to start the scano shooting is issued from the CPU, the CPU 21 sends a control signal to each unit according to the instruction, and the scano shooting is executed. First, a dose of X-rays for scanography is applied to the subject P from the X-ray tube 11, the X-rays transmitted through the subject P are detected by the X-ray detector 12, and the X-rays are transmitted according to the transmitted X-ray dose. It is converted into an electrical signal and output. This output is collected by the DAS 17 as X-ray transmission data. The data collected by the DAS 17 is pre-processed (water correction, etc.) by the pre-processing unit 25, and then is temporarily stored in the memory 30 via the data data bus 24 together with the position information of the scano imaging on the subject P as projection data. It is stored, further read as scano data from the memory 30, and sent to the scano image generation unit 12 to generate scano image data.

Here, the X-ray detector 12 has an X-axis in the body axis direction.
Since 40 line detection element rows are arranged, 40 slices of data can be detected by the X-ray detector 12, but in the present embodiment, 40 slices of data are used to generate 4 lines.
Scano image data for 0 slices is generated. That is, the data detected at the position 12-1 in FIG. 3 is used as the scano data for generating the scano image at that position. Similarly, data detected at the positions 12-2 to 12-40 are used as scano data for generating scano images at the positions 12-2 to 12-40, respectively, to create scano image data.

Thus, as shown in FIG. 5, the first scanograph is performed to obtain the data of the range of S1 (40 slices) on the rotation center axis RC of the X-ray tube 11 and the X-ray detector 12. After that, the next scano imaging is performed by moving the tabletop 5 by the column width K of the X-ray detector 12 (that is, the width of the X-ray detection elements for 40 columns arranged in the slice thickness direction). It Then, the data in the next S2 range (40 slices) is obtained. Similarly, data up to the range Sn is obtained.
The beam width (each Si) in the body axis direction when the X-rays pass through the rotation center axis RC of the X-ray tube 11 and the X-ray detector 12.
Corresponds to the slice thickness in the scanogram. That is, the scano data for the slice thickness Si can be obtained by one scan imaging.

In this case, since the object P is sequentially moved by the column width of the X-ray detector 12 for each X-ray irradiation, the obtained data (between Sn-1 and Sn) is As shown in Fig. 5, there is a part that the X-ray beam does not cover, and there is no data in this part. Therefore, when creating a scano image, use a method such as interpolation of the preceding and following data. Supplement the data. In this way, the scanogram of the desired range is created. The data of the generated scano image is once stored in the display memory 29 and then displayed on the monitor 7 as a scano image. The data of this scano image is read out from the display memory 29 separately, and the
The data is stored in the magnetic disk device 31 via 6, and data can be read out as necessary to display a scanogram on the monitor 7.

Here, the relationship between the position information of the top plate 5 and the trigger signal for X-ray irradiation from the X-ray tube 11 is as shown in FIG. In (a), the horizontal axis represents time, and the vertical axis represents the movement amount of the top 5 (that is, the irradiation position of the X-ray on the subject P). Further, (b) shows the generation timing of the trigger signal when irradiating the X-ray. As is clear from this figure, the couch driving unit 15 first moves the table 5 so that the subject P is located at a predetermined start position T1 for scanography. Then, the CPU 21 applies the first trigger signal t1 to the high-voltage generator 16 to irradiate the X-ray from the X-ray tube 11, and performs the first scano imaging. The pulse width Δt of the trigger signal is, for example, about 0.1 second.
When the irradiation of X-rays is stopped, the bed driving unit 15 slides the tabletop 5 in the slice thickness direction. When the amount of movement reaches the column width of the X-ray detector 12, the CPU 21 applies the trigger signal t2 to the high voltage generator 16 at the position T2 to perform the second scano imaging. After that, in the same way,
X-rays are emitted intermittently to perform scanographing in a desired range.

As described above, by controlling the irradiation timing of X-rays based on the moving amount of the tabletop, it is possible to irradiate X-rays at an optimum timing without waste. Therefore, it is possible to effectively use X-rays and realize scan imaging while suppressing excessive exposure to the subject. In this case, it is not always necessary to irradiate X-rays with the top 5 stopped, and the top 5
While continuously sliding the tabletop 5, the top plate 5 is the X-ray detector 1.
A trigger signal may be generated and X-rays may be emitted each time the column width of 2 is moved. Further, X-rays may be continuously emitted during scanography.

A scan plan is prepared based on the scanogram thus obtained. Based on the scan plan, the operator inputs the scan conditions from the input device 6 and instructs the scan, and the CPU 21 sends a control signal based on the scan conditions to each part of the X-ray CT apparatus. The couch controller 15 moves the top 5 on which the subject P is placed in accordance with the scan start position based on the scan plan. Then, the rotation drive unit 14 drives the rotation unit 13 at a predetermined speed (for example, 0.5 second / revolution or 1 second / revolution) to move the X-ray tube 11 and the X-ray detector 12 to the subject P. While continuously rotating around, the high voltage generator operates from the X-ray tube 11 to the X-axis.
The X-ray transmission data of multiple directions are collected by irradiating the X-ray. X
Since the line detector 12 is a two-dimensional detector, data for a plurality of slices can be collected by one rotation, but the slice position can be changed by moving the top plate 5 and / or the gantry 1 during continuous rotation. You can also take a picture.

The collected data is subjected to pre-processing such as calibration in a pre-processing unit 25, and is then transmitted as projection data (raw data) via a data bus 24 together with position information indicating the position of the view of the subject P. The data is temporarily stored in the memory 30 and then sent to the reconstruction unit 27 to reconstruct tomographic image data. Here, the view means a set of projection data at a certain angle with respect to the subject P. The data of the reconstructed tomographic image is once stored in the display memory 29 and then displayed as a tomographic image on the monitor 7. This tomographic image data is separately read from the display memory 29 and stored in the magnetic disk device 31 via the disk interface 26 so that the data can be read as necessary to display the tomographic image on the monitor 7. There is.

According to the present embodiment, scanograph data for a plurality of slices can be collected by one scanographing operation, so that a scanograph image in a desired range can be obtained with a smaller number of imaging times than in the past. Therefore, the scano imaging can be completed in a short time, and the burden on the subject at the time of imaging can be reduced. In addition, an X-ray detection element array necessary for generating scano images for a plurality of set slice widths is selected, scanographing is performed,
Since the scano image is generated using the data for the selected X-ray detection element array, the resolution is better than that of the conventional scano image.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram for explaining scano imaging in the second embodiment of the present invention. The configuration of the X-ray CT apparatus according to this embodiment is the same as that of the first embodiment. The difference between the present embodiment and the first embodiment is that the slide pitch of the tabletop to be moved for each scano imaging is slightly smaller, but a method such as interpolation is not necessary to make up for the lack of data when creating a scano image. That's what it means.
That is, as shown in FIG. 7, the X-ray tube 11 and the X-ray detector 1
At the rotation center axis RC of 2, the X-ray beam is in contact with the slice thickness direction (body axis direction) so that the X-ray beam is in contact with the slice thickness direction (body axis direction), and only the X-ray beam width L on the RC is obtained for each scanograph. The top plate 5 is slid to perform scano photographing.

Also in this embodiment, the relationship between the position information of the top plate 5 and the trigger signal for the X-ray irradiation from the X-ray tube 11 is as shown in FIG. That is, first, after performing the first scanography at the predetermined start position T1, the top plate 5
Slide in the slice thickness direction. Then, when the amount of movement reaches the X-ray beam width L on RC, a trigger signal is given to the high voltage generator 16 to perform the second scan imaging. Thereafter, in the same manner, X-rays are intermittently emitted to scan and photograph a desired range. At this time, it is desirable to set the moving speed of the top 5 to an optimum speed according to the pulse width of the X-rays to be emitted (that is, the pulse width Δt of the trigger signal). This is because the subject P (that is, the top plate 5) moves by 10% or more of the width of one row of the X-ray detection element rows in the slice thickness direction in the X-ray detector 12 during X-ray irradiation. As a result, the scano images overlap with each other, and the X-rays to be emitted are wasted accordingly.

Therefore, letting Δr be the slice width on RC and Δt be the pulse width of the irradiated X-rays, V that satisfies V ≦ (0.1 × Δr) / Δt (1) If set as the optimum moving speed of the plate 5, the overlap of scano images will be reduced. Moreover,
Since correction such as interpolation is not necessary when reconstructing the scanogram,
A more accurate and accurate scanogram can be obtained in a relatively short time. In addition, a row of XZ sensor elements necessary for generating scano images for a plurality of set slice widths is selected, scanographing is performed, and the selected X-rays are scanned.
Since the scano image is generated using the data of the line detection element array, the resolution is better than that of the conventional scano image.

Now, in the first and second embodiments,
The scanogram is generated based on the output data of all the X-ray detection element arrays in the X-ray detector 12 in the body axis direction (that is, all the X-ray detection elements in the X-ray detector 12). It is desirable that the DAS 17 that collects the output data is composed of the same number of active elements such as integrators and A / D converters corresponding to the X-ray detection elements in both the channel direction and the slice direction. However, there is a limit to the number of DASs 17 that can be installed due to restrictions on the mounting space on the gantry 1 and cost performance, and if the same number of active elements as the number of X-ray detection elements are arranged in the channel direction, slice Only about 10 rows of active elements can be arranged in the thickness direction. That is, it is only possible to install ten DASs 17 for the X-ray detector 12. Therefore, the X-ray detector 12 and the DAS 17 are
By connecting via a multiplexer composed of switching elements and the like, even with a small number of DASs 17, output data from all X-ray detection elements composed in a two-dimensional array can be collected.

FIG. 8 is a diagram showing the structure of a multiplexer for connecting the X-ray detector and the DAS. For example, as shown in FIG. 8, when the X-ray detector 12 is a two-dimensional array detector in which 40 X-ray detection element rows are arranged in the slice thickness direction, ten DASs 17 are installed. If so, ten multiplexers 40 will be prepared. Then, assuming that one multiplexer 40 is assigned to each of the four rows of X-ray detection elements in the slice thickness direction of the X-ray detector 12, the first multiplexer 40-1 is set to X.
The first row (12-1) to the fourth row (12-
It is located between the X-ray detection element up to 4) and the first DAS 17-1. Also, the second multiplexer 40-2
Of the X-ray detector 12 from the fifth row (12-5) to the eighth row (12-8) of the X-ray detector 12 and the second DAS 17-.
Located between 2 and. In a similar manner, the tenth multiplexer 40-10 is connected to the X-ray detection elements in the 37th column (12-37) to the 40th column (12-40) of the X-ray detector 12 and the tenth DAS 17-10. Located between and.

Then, each of the multiplexers 40-1 to 40
By operating -10 in synchronism, the signals from the X-ray detection elements in each of the four columns of the X-ray detector 12, which are shared by the -10, are sequentially switched and read, and the corresponding DASs are read.
17-1 to 17-10. That is, first, the first column (12-1) and the fifth column (12- of the X-ray detector 12
5), 9th row (12-9), 13th row (12-13),
17th row (12-17), 21st row (12-21), 2
5th row (12-25), 29th row (12-29), 33
X in rows (12-33) and 37 (12-37)
The signal of the line detection element is supplied to each DAS 17-1 to 17-10. Next, the second column of the X-ray detector 12 (12-
2), 6th row (12-6) ... 38th row (12-3)
The signal of the X-ray detection element of 8) is the DAS 17-1 to 17
-10, and the third row (12-3), the seventh row (12-7) ... 39th row (1
The signal of the X-ray detection element in 2-39) is transmitted to each DAS 17-1.
~ 17-10, and finally 4 of the X-ray detector 12
The signals of the X-ray detection elements in the columns (12-4), 8 (12-8), ...
-1 to 17-10. The X-ray detector 12
The X-ray detection element of (1) stores electric charges and the like until a signal is read.

Then, by the first X-ray irradiation, 40
When the projection data for the slices is obtained, the subject P moves to the next 40
Moved to a position to obtain projection data for slices,
During this time, a scanogram of this portion is generated and displayed on the monitor 7. Further, a scan image for 40 slices is sequentially generated by the X-ray irradiation from the second time onward, and every time a scan image is generated, a scan image whose range has been expanded is sequentially displayed on the monitor 7. In recent helical CT devices, it is possible to display a tomographic image in real time following a helical scan operation. This is because the projection data required to reconstruct one tomographic image is This is because the calculation processing speed is increased so that one tomographic image can be reconstructed in a time shorter than the acquisition time. Therefore, by applying this technique, it is easy to display the scanogram in real time.

Thus, the X-ray detector 12 and the DAS 17 are
And a DAS 17 having a small number
However, since output data from all X-ray detection elements configured in a two-dimensional array can be collected, the number of data collection devices can be reduced, the mounting space can be reduced, and the cost performance can be improved. Can be achieved.

Next, a third embodiment of the present invention will be described with reference to FIG. The configuration of the X-ray CT apparatus is
This is similar to the above embodiment. FIG. 9 is a diagram for explaining scano imaging in the third embodiment of the present invention.
In the first and second embodiments, the output data from all the X-ray detection elements configured in a two-dimensional array is collected to create a scanogram. However, the closer to the end of the X-ray beam emitted from the X-ray tube 11 in the slice thickness direction (body axis direction), the larger the angle at which the X-ray penetrates the subject P (that is, Since the X-rays detected at the end of the X-ray detector in the slice thickness direction are transmitted at a large angle with respect to the subject P), the transmitted X-rays are X-rays.
When a scanograph is created by using the output data based on the detection detected by the line detector 12, distortion occurs in that part, and the position in the scanograph and the actual object P
There will be a gap between the position and.

Therefore, in this embodiment, only the X-rays emitted from the X-ray tube 11 are transmitted almost perpendicularly to the subject P (that is, the X-rays transmitted almost perpendicularly to the RC line). (Only lines) are detected and a scanogram is created from the data. That is, the X-ray detector 1
Among the X-ray detection element rows in the slice thickness direction (body axis direction) in 2, the scanno image is created using the data detected by a plurality of rows (for example, four rows) of X-ray detection elements near the center. To In FIG. 9, the X-ray detection elements for four rows sandwiching the center of the X-ray detector 12 in the slice thickness direction (body axis direction) are indicated by diagonal lines. The scanographing procedure in this case is the same as that in the first embodiment. First, after the first scanograph is performed at a position of the subject P to obtain scanodata in the range of S1 (for 4 slices) on the rotation center axis RC of the X-ray tube 11 and the X-ray detector 12, The next scano imaging is performed by moving the top plate 5 by the column width K of the X-ray detector 12. Then, the scan data of the next range S2 is obtained. Similarly, scano data up to the range Sn is obtained.

Also in this case, as in the first embodiment, the object P is sequentially moved by the column width of the X-ray detector 12, so that the obtained data (between Sn-1 and Sn) can be obtained. Is X
Since there is a portion not covered by the line beam and there is no data in this portion, when creating the scanogram, the data is supplemented by a method such as interpolation using the preceding and following data. In this way, the scanogram of the desired range is created. The flow of generating a scano image based on the data obtained in this way is also the same as in the first embodiment.
Further, the relationship between the position information of the top plate 5 and the trigger signal of the X-ray irradiation from the X-ray tube 11 is as shown in FIG.
It is also possible to intermittently irradiate X-rays every time the top plate 5 is moved by the row width K of 2 and perform scano imaging in a desired range.
It is also possible to irradiate X-rays by generating a trigger signal every time the tabletop 5 moves by the width of the row of the X-ray detectors 12 while continuously sliding the tabletop 5.

In the case of the present embodiment, only a part of the X-ray detection element array in the slice thickness direction is used for collecting scano data, so that it is performed once compared with the first and second embodiments. Since the range of the scano image that can be created by X-ray irradiation is narrow, the time for scanographing becomes longer accordingly. However, since the scanogram is created using only the detection data based on the X-rays in which the X-ray beam is transmitted almost perpendicularly to the subject P, it is possible to create a highly accurate scanogram with little distortion in a short time. X that is necessary for generating scano images for a plurality of set slice widths.
Since a line detection element array is selected, scan imaging is performed, and a scano image is generated using the data for the selected X-ray detection element array, the resolution is better than that of the conventional scan image. .

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a diagram for explaining scano imaging in the fourth embodiment of the present invention.
The configuration of the X-ray CT apparatus according to this embodiment is the same as that of the third embodiment. Similar to the difference between the first embodiment and the second embodiment, the difference between the present embodiment and the third embodiment is that the slide pitch of the top plate to be moved for each scano photographing in the present embodiment is different from the third embodiment. However, it is not necessary to use a method such as interpolation to make up for the lack of data when creating a scanogram.

For example, as shown in FIG. 10, an X-ray tube 11
And the rotation center axis RC of the X-ray detector 12
X-rays that have passed through the X-ray detector 12 have X-ray beam widths L that are detected by the X-ray detector 12 in four rows (hatched portions) sandwiching the center in the slice thickness direction (body axis direction) and contact each other for each scanograph. In this manner, the top plate 5 is slid by the width L of the X-ray beam on the rotation stop axis RC to perform scanographing. Also in the present embodiment, the relationship between the position information of the table 5 and the trigger signal of the X-ray irradiation from the X-ray tube 11 is similar to that in FIG. 6, and is intermittently every time the table 5 is moved by the width L. It is also possible to irradiate X-rays to perform scanographing in a desired range, or to generate X-rays by generating a trigger signal each time the tabletop 5 moves by the width L while continuously sliding the tabletop 5. You may do it.

At this time, it is desirable to set the moving speed of the top plate 5 to an optimum speed according to the beam width of the X-rays to be irradiated. That is, if V that satisfies the relational expression (1) above is set as the optimum moving speed of the tabletop 5, the overlap of scano images will be reduced. Therefore, useless X-ray irradiation can be suppressed. Furthermore, since a scano image can be created using only the detection data based on the X-rays in which the X-ray beam is transmitted almost perpendicularly to the subject P, the scanograph data in the desired range can be collected without excess or deficiency. No correction such as interpolation is required during reconstruction. Therefore, it is possible to create a highly accurate scanogram with little distortion in a relatively short time. Further, in the present embodiment, since the scanogram is generated by using the data of the X-ray detection element array necessary for generating the scanogram of the set plural slice widths, the conventional scanogram is used. The resolution is better than.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 11 is a diagram for explaining scano imaging in the fifth embodiment of the present invention. In each of the above embodiments, the control of the X-ray beam width in the body axis direction is not particularly considered. In particular, in the third and fourth embodiments, at the time of scanographing, the data detected by the X-ray detectors on the outer side of the four rows sandwiching the center of the X-ray detector 12 in the body axis direction is used to generate a scano image. Is not used,
That amount of X-rays is unnecessary for scanography.

In view of this, in the present embodiment, during scanography, the gantry 1 is used according to the number of X-ray detection elements in the body axis direction of the X-ray detector 12 that collects data for generating a scanogram.
The inner diaphragm (collimator) is controlled to narrow the beam width of the X-ray beam in the body axis direction, so that X-rays transmitted through the subject P are hardly detected except for the X-ray detection element for collecting the scano data. To For example, the operator inputs the input device 6
When the scanograph mode is designated by, the CPU 21 selects the number of X-ray detection elements in the slice thickness direction of the X-ray detector 12 that collects scano data during scanographing according to a preset slice width (for example, As shown in FIG. 11, four rows (shaded area) sandwiching the center of the X-ray detector). The CPU determines the aperture amount according to the selected number of rows, operates the aperture based on the determined aperture amount, and the beam width in the slice thickness direction of the X-ray beam emitted from the irradiation opening of the gantry 1. Squeeze. The aperture amount may be set such that the X-ray beam width on the rotation center axis RC substantially matches the preset slice width, for example.

Alternatively, the number of X-ray detecting elements in the slice thickness direction (body axis direction) of the X-ray detector 12 that collects the scano data at the time of scan imaging is 4 with the center of the X-ray detector sandwiched.
A row (hatched portion) may be selected in advance, and when the operator designates the scano imaging mode, the CPU determines the slice width according to the number of elements, so that, for example, the slice width is on the rotation center axis RC. The aperture may be operated so that the X-ray beam widths substantially match, and the beam width in the slice thickness direction of the X-ray beam emitted from the irradiation port of the gantry 1 may be reduced.

After the control of the aperture is completed, scano photographing is started. The scanographing procedure is the same as in the third embodiment. That is, first, the first scanograph is performed at a certain position of the subject P, and the scanograph data in the range of S1 (for 4 slices) on the rotation center axis RC of the X-ray tube 11 and the X-ray detector 12 is obtained. After that, the next scanograph is the X-ray detector 1.
This is executed by moving the top plate 5 by the column width K of 2. Then, the scan data of the next range S2 is obtained. Similarly, scano data up to the range Sn is obtained. In this case, since the X-ray beam does not reach between the obtained scano data S1 to Sn and there is no scano data, during that period, processing such as interpolation is performed using the scano data obtained before and after. By filling in the data. In this way, by reconstructing the obtained scanogram data, a scanogram of a desired range is generated.

In the present embodiment as well, the relationship between the position information of the top plate 5 and the trigger signal for X-ray irradiation from the X-ray tube 11 is the same as in FIG. 6, and the column width K of the X-ray detectors 12 is the same. It is also possible to intermittently irradiate X-rays every time the top plate 5 is moved to perform scanographing in a desired range, or the top plate 5 is continuously slid while the top plate 5 is being moved by the X-ray detector 12. A trigger signal may be generated each time the column width is moved to irradiate X-rays. In addition, X-rays may be continuously emitted while continuously moving the top plate or the gantry to perform scanographing. From the beginning, the irradiation range of X-rays is narrowed down to the necessary minimum, so scanning can be performed in a short time while effectively using X-rays (that is, while suppressing excessive exposure of the X-rays to the subject). It can be performed.

Conventionally, the aperture control of the beam width in the slice thickness direction of the X-ray beam has not been considered,
According to the present embodiment, the beam width of the X-ray beam in the slice thickness direction is controlled according to the number of X-ray detection elements in the slice thickness direction of the X-ray detector 12 that collects the scano data. Can be effectively used, and a scanogram can be obtained without giving an excessive exposure to the subject. Further, since the scano image is created by using only the detection data based on the X-rays in which the X-ray beam is transmitted almost perpendicularly to the subject P as the scano data, a highly accurate scano image with little distortion can be obtained in a short time. Can be created with. In addition, an X-ray detection element array necessary for generating scano images for a plurality of set slice widths is selected, scanography is performed, and the data for the selected X-ray detection element array is used. Since a scano image is generated by using the scano image, the resolution is better than that of the conventional scan image.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
2 will be described. FIG. 12 is a diagram for explaining scano imaging in the sixth embodiment of the present invention. In the fifth embodiment described above, data is filled in a portion where data is insufficient by processing such as interpolation, but in the present embodiment, movement of the tabletop 5 is controlled so that the data is not insufficient. Take a scano shoot.

First, when the operator designates the scano imaging mode by the input device 6, the CPU 21 collects the scano data during the scano imaging in accordance with the preset slice width, as in the fifth embodiment. Select the number of X-ray detection elements in the slice thickness direction of the vessel 12 (for example,
As shown in FIG. 12, four rows (shaded area) sandwiching the center of the X-ray detector). The CPU determines the aperture amount according to the selected number of rows, operates the aperture based on the determined aperture amount, and the beam width in the slice thickness direction of the X-ray beam emitted from the irradiation opening of the gantry 1. Squeeze. The aperture amount is, for example,
It suffices that the X-ray beam width on the rotation center axis RC substantially coincides with the preset slice width.

After the control of the aperture is completed, scano photographing is started. The scanography procedure is the same as that in the fourth embodiment. That is, in the rotation center axis RC of the X-ray tube 11 and the X-ray detector 12, the X-rays transmitted through the subject P have four rows in the X-ray detector 12 that sandwich the center in the slice thickness direction (body axis direction) ( The top plate 5 is slid by the X-ray beam width L on the RC so that the X-ray beam width L corresponding to the X-ray beam width L detected by the hatched portion) is in contact with each other for the scano-imaging. In this way, projection data in a desired range is collected, and the collected projection data is reconstructed to generate a scanogram.

In the present embodiment as well, the relationship between the position information of the top plate 5 and the trigger signal for X-ray irradiation from the X-ray tube 11 is the same as in FIG. It is also possible to irradiate X-rays intermittently every time the top plate 5 is moved by 4 slices) to perform scanographing in a desired range, or while the top plate 5 is continuously slid, the top plate 5 is moved to X-ray. Every time the line detector 12 moves by the width L, a trigger signal is generated to generate X.
You may make it irradiate a line. In addition, X-rays may be continuously emitted while continuously moving the top plate or the gantry to perform scanographing. From the beginning, the irradiation range of X-rays is narrowed down to the necessary minimum, so scanning can be performed in a short time while effectively using X-rays (that is, while suppressing excessive exposure of the X-rays to the subject). It can be performed.

Further, it is desirable to set the moving speed of the tabletop 5 to an optimum speed according to the pulse width of the X-rays to be irradiated. In other words, if V that satisfies the relational expression (1) above is set as the optimum moving speed of the tabletop 5, the overlap of scanograms will be small and small. Therefore, useless X-ray irradiation can be suppressed. Furthermore, since a scanogram can be created by using only the detection data based on the X-rays in which the X-ray beam is transmitted almost perpendicularly to the subject P as data, the projection data in the desired range can be collected without excess or deficiency. No correction such as interpolation is required for image reconstruction. Therefore, it is possible to create a highly accurate scanogram with little distortion in a relatively short time. Also,
In the present embodiment, an X-ray detection element array necessary for generating scanograms for a plurality of set slice widths is selected, scanographing is performed, and the selected X-ray detection element array is scanned. Since the scano image is generated using the data, it is possible to create a scano image having a higher resolution than the conventional one.

In each of the above-described embodiments, the X-ray detecting element array necessary for generating the scanograms for the plurality of set slice widths is selected, the scanograph is performed, and the selected X-rays are selected. Since the scanograph image is generated using the data for the detection element array, the scan speed and resolution of the scanograph image are far superior to the conventional ones.
Is not as good as it used to be. In order to improve the S / N, it is sufficient to increase the dose of X-rays to be irradiated, but increasing the dose of X-rays increases the amount of exposure of the subject, which is not preferable. Therefore, instead of increasing the X-ray dose, for example, the S / N can be improved by the following procedure.

That is, X-rays are irradiated from the X-ray tube every time the top plate or the gantry (X-ray tube and X-ray detector) is moved by one row or a plurality of rows in the slice thickness direction, Data at the same position in the slice thickness direction (that is, data overlapping at the same position in the slice thickness direction) collected at different times is subjected to arithmetic mean processing, and the data is used as scano data at that position.

By generating a scano image on the basis of the scano data thus obtained, the scan image S
/ N can be improved. The means for moving the gantry can be realized, for example, by providing casters or the like below the gantry. Then, when the detecting means detects the amount of movement by the caster and the detecting means detects that the gantry has moved by a predetermined amount of movement, it sends a signal to the high voltage generator 16 and receives the signal. , X-ray irradiation from the X-ray tube may be executed. In addition, in FIG. 5, FIG. 7, FIG. 9, FIG. 10, FIG. 11 and FIG. 12, for convenience, the X-ray tube 11 and the X-ray detector 12 are moved with respect to the subject P that is stopped. , But this is relative and of course the X-ray tube 1 is at rest
It is the same even if the top plate 5 is moved with respect to 1 and the X-ray detector 12.

The present invention is not limited to the above embodiment and can be implemented in various forms. For example, FIG. 3 shows the X-ray detector 12 having a uniform pitch in which 40 rows of X-ray detection elements are arranged at a pitch of 1 mm in the slice thickness direction, but the pitch in the slice thickness direction is not necessarily uniform. It doesn't have to be. For example, a nonuniform pitch X-ray detector has been developed, which is configured by arranging a total of 40 X-ray detection elements in a central portion of 16 rows with a 0.5 mm pitch and 12 rows with a 1 mm pitch on both sides thereof. In the present invention, such an X-ray detector can also be used.
Of course, the X-ray detection element array is not limited to 40 arrays, and the pitch is not limited to 0.5 mm or 1 mm. Here, the value of the pitch of the X-ray detection element is a value of a sensitive area for X-rays at the rotation centers of the X-ray tube 11 and the X-ray detector 12, and the actual size of the X-ray detector 12 is not.

Further, in FIG. 8, the multiplexer 40
In the above description, the X-ray detection elements of the X-ray detector 12 are switched every four columns to supply a signal to the DAS 17. However, if the X-ray detection elements are bundled for each channel in the slice thickness direction in two rows (or more rows may be provided) and the signal is supplied to the DAS17, DAS1
The number of 7 can be halved. The technique for bundling the signals from the X-ray detection element array and supplying the signals to the DAS is described in detail, for example, in Japanese Patent Laid-Open No. 10-24031.

Further, in the above embodiment, an example in which the X-ray detecting elements for four columns from the center of the X-ray detector are used for collecting data for generating the scanogram, has been shown. If the detection elements are expanded to more than 4 rows, for example, 16 rows, and the data detected by the X-ray detection elements near the outside is subjected to fan beam reconstruction processing and a scano image is generated, the position near the outside is detected. The distortion of the scano image can be corrected, and a highly accurate scano image can be obtained in a wider range by one scan shooting, so that the shooting time can be shortened.

[0056]

As described in detail above, according to the present invention, a wide range of scan images can be obtained in a short time,
The burden on the subject can be reduced and patient throughput can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a schematic configuration of an X-ray CT apparatus according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of the X-ray CT apparatus shown in FIG.

FIG. 3 is a diagram showing a schematic configuration of the X-ray detector shown in FIG.

FIG. 4 is a block diagram showing a configuration of a control unit shown in FIG.

FIG. 5 is a diagram showing a situation of scano photography in the first embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the movement of the top plate and the X-ray irradiation timing during scanography.

FIG. 7 is a diagram showing a situation of scano photography in the second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a multiplexer that connects an X-ray detector and a DAS.

FIG. 9 is a diagram showing a situation of scano photographing in the third embodiment of the present invention.

FIG. 10 is a diagram showing a situation of scano photographing in the fourth embodiment of the present invention.

FIG. 11 is a diagram showing a situation of scano photographing in the fifth embodiment of the present invention.

FIG. 12 is a diagram showing a situation of scano photographing in the sixth embodiment of the present invention.

[Explanation of symbols]

1 stand 2 sleeper 3 console 4 openings 5 Top plate 6 input device 7 monitors 11 X-ray tube 12 X-ray detector 13 rotating part 14 Rotational drive 15 Sleeper control unit 16 High voltage generator 17 DAS 20 Control unit 21 CPU 22 clock circuits 23 Control Bus 24 data buses 25 Pretreatment section 26 disk interface 27 Reconstruction Department 28 Scano image generator 29 Display memory 30 memory 31 magnetic disk unit 12-1 to 12-40 X-ray detection element array P subject Rotation center axis of RC X-ray tube and X-ray detector L, S1 to Sn X-ray beam width in slice thickness direction

Claims (9)

[Claims] 1. An X-ray tube capable of irradiating X-rays, and a plurality of X-rays for detecting X-rays radiated from said X-ray tube and transmitted through a subject.
X-ray detectors in which the line detection elements are arranged in the channel direction and the body axis direction of the subject, respectively, and the body axis direction necessary for generating scanograms for a plurality of predetermined slice widths Of the X-ray detection element array, and a scano image generation section for generating a scano image using the data for the X-ray detection element array selected by the selection means. X-ray CT system. 2. A bed having a top plate on which the subject is placed, a moving means for moving the X-ray tube and the X-ray detector, and / or the top plate in the body axis direction. X-ray irradiation control means for controlling the irradiation timing of X-rays from the X-ray tube, wherein the X-ray irradiation control means is moved by the moving means, and the X-ray tube and X-ray detector, and / or The X-ray CT apparatus according to claim 1, wherein the irradiation timing of X-rays from the X-ray tube is controlled so that X-rays are irradiated every time the top plate moves by a plurality of slices. 3. The selection means selects a plurality of rows sandwiching the center of the X-ray detection element row among all the X-ray detection element rows in the X-ray detector. X-ray CT system. 4. The scano generation unit includes first data obtained by irradiating the first X-ray by the X-ray tube, second data obtained by irradiating the second X-ray, and the first data. The X-ray C according to claim 1, wherein a scanogram is generated using data obtained by interpolating between the first and second data.
T device. 5. A data collecting means for collecting an output from the X-ray detector is provided, and the data collecting means is provided for each of a plurality of X-ray detecting element rows in the body axis direction in the X-ray detector. It is connected through a multiplexer, and the output from each X-ray detection element is switched by switching the connection between the multiplexer and each X-ray detection element row, and output signals from all the X-ray detection element rows are collected. X according to claim 1.
X-ray CT equipment. 6. The moving means moves the X-ray tube and / or the X-ray detector and / or the top plate continuously or intermittently in the body axis direction. X-ray CT system. 7. The X-ray irradiation control means sets an X-ray irradiation timing of the X-ray tube so as to irradiate X-rays each time the X-ray detector is moved by the column width in the body axis direction. The X-ray CT apparatus according to claim 2, which is controlled. 8. A support means for supporting the X-ray tube and the X-ray detector so as to be rotatable around the subject,
The X-ray irradiation control means includes an X-ray beam and a second X-ray beam during the first X-ray irradiation on the rotation center axis of the X-ray tube and the X-ray detector.
X-ray beam at the time of X-ray irradiation, so that the X-ray beam touches each other.
The X-ray CT apparatus according to claim 2, wherein the X-ray irradiation timing of the X-ray tube is controlled. 9. X-ray diaphragm means for controlling the beam width of X-rays emitted from said X-ray tube in said body axis direction,
The line diaphragm means controls the beam width so that the beam width of the X-rays on the rotation center axis of the X-ray tube and the X-ray detector substantially matches a preset slice width. The X-ray CT apparatus according to claim 1 or 3.