JP2003135442A - X-ray ct system and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT system capable of changing photographing time of scout scanning, an exposure or the resolution of a scout image corresponding to a purpose of photographing, and its control method. SOLUTION: In a fluoroscopic image data gathering process of performing scout scanning, a prescribed data gathering mode (high speed mode/high definition mode) is judged (step S4). Corresponding to the judged data gathering mode, the opening width of an aperture and the carrying speed of a table for mounting a testee body are set (steps S5 and 6/steps S7 and 8) and the fluoroscopic image data are gathered (step S9).

Description

Detailed Description of the Invention

[0001]

The present invention relates to an X-ray CT (Computerized Tom) for obtaining an X-ray tomographic image of a subject by X-ray irradiation.
and a control method thereof.

[0002]

2. Description of the Related Art An X-ray CT system scans a patient (subject) lying on a table with X-rays from a plurality of view directions, and obtains the X-rays from each view direction transmitted through the subject. By performing image reconstruction processing based on the projection data, a tomographic image of the diagnosis site is provided.

Specifically, the X-ray CT system is an X-ray detector having, for example, an X-ray tube that emits fan beam X-rays and a large number (for example, 1,000) of detection channels arranged in the fan spreading direction. (Provided so as to face the X-ray tube with the subject placed on the table sandwiched therebetween), and the X-ray tube and the X-ray detector integrally rotate around the subject. During this rotational movement, the fan beam X is emitted from the X-ray tube.
X-rays that have passed through the subject are exposed to X-rays at predetermined angles.
The projection data is collected, that is, scanned by the detection by the line detector.

By the way, before actually performing the scan,
A scan condition such as what area of the subject is to be scanned with what slice thickness and a condition of the image reconstruction process are planned according to a diagnosis site and a diagnosis purpose. Such a plan is called a scan plan.
The X-ray CT system generally provides a graphical user interface environment for making a scan plan from the scan plan screen displayed on the monitor of the operation console.

In order to make a scan plan, first, a scout scan is performed. The scout scan is to obtain a single fluoroscopic image from projection data obtained by continuously irradiating X-rays while gradually transporting a table on which a subject is placed while fixing the X-ray tube at a fixed angle. It is a thing. When the scout scan ends, this perspective image (called a scout image) is displayed in a predetermined area of the scan planning screen. The operator can proceed with the scan plan while looking at this scout image.

[0006]

By the way, in the recent X-ray CT system, a thinner slice is obtained by irradiating only a part of the detector for detecting X-rays in the table carrying direction (z-axis direction) with X-rays. It is possible to generate a tomographic image having a thickness (for example, 1 mm or less). This improves the resolution of the scout image in the z-axis direction, which is particularly advantageous when it is desired to obtain high-definition image quality. On the other hand, when the size of the detector irradiated with X-rays decreases, the number of incident X-ray photons decreases, and the S / N deteriorates. Therefore, it is necessary to secure the S / N by slowing the table transport speed and lengthening the X-ray irradiation time.

On the other hand, there are cases where it is rather desired to shorten the photographing time even if the resolution is sacrificed.

However, in the conventional X-ray CT system, the imaging time of the scout scan depends on the purpose of imaging,
It was not possible to change the exposure dose or the resolution of the scout image.

The present invention has been made in view of the above problems, and an X-ray CT system and its control method capable of changing the imaging time, the exposure dose, or the resolution of a scout scan according to the purpose of imaging. The purpose is to provide.

[0010]

In order to solve this problem, for example, an X-ray CT system of the present invention has the following configuration. That is, an X-ray CT system including an X-ray generation source and an X-ray detection unit having a plurality of detector rows arranged in a transportation direction of a table for transporting an object, the X-ray CT system comprising: Of apertures for limiting the X-ray irradiation range, aperture adjusting means for adjusting the width of the slits in the carrying direction, speed adjusting means for adjusting the carrying speed of the table, and the X-rays. And a perspective image data collecting means for collecting the perspective image data by transporting the table while fixing the position of the source.
The fluoroscopic image data collecting unit collects the fluoroscopic image data by setting the width of the slit and the transport speed of the table according to the judging unit that judges a predetermined data collecting mode and the judged data collecting mode. And a control means for performing the above.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an X-ray C in an embodiment.
It is a block configuration diagram of a T system. As shown in the figure, the present system performs gantry device 100 for irradiating a subject with X-rays and detecting X-rays transmitted through the subject, and various operation settings for the gantry device 100. Operation console 20 for reconstructing and outputting (displaying) an X-ray tomographic image based on the output data
It is composed of 0s.

The gantry apparatus 100 has the following configuration including the main controller 1 that controls the entire apparatus.

2a and 2b are interfaces for communicating with the operation console 200, and 3 is a table 11.
The subject (patient) laid on top is in the direction perpendicular to the drawing (hereinafter referred to as the z-axis, which generally corresponds to the direction of the patient's body axis).
A gantry having a cavity for transporting to the inside of the gantry, and inside thereof, an X-ray tube 4 (driving is controlled by an X-ray tube controller 5) as an X-ray generation source, and an X-ray irradiation range is limited. Aperture 6 having an opening for
Aperture control motor 7 for adjusting the aperture width in the z-axis direction of the
(Drive is controlled by the aperture control motor driver 8)
Is provided.

Further, the gantry 3 is provided with an X-ray detector 14 for detecting X-rays from the X-ray tube 4 that has passed through the aperture 6 and the cavity, and projection data obtained from the X-ray detector 14. A data collecting unit 15 for collecting is also provided. The X-ray tube 4, the aperture 6, and the X-ray detection unit 14 are provided at positions facing each other with the cavity portion sandwiched therebetween, that is, with the subject being sandwiched therebetween, and around the cavity portion with the relationship maintained. Is designed to rotate. This rotation is performed by the rotary motor 9 driven by the drive signal from the rotary motor driver 10.

The table 11 on which the subject is placed is configured to be transported in the z-axis direction, and the transport speed thereof can be controlled. The table motor driver 13 drives the table 11.
The table motor 12 driven by the drive signal from

The main controller 1 analyzes various commands received via the interface 2a, and based on that, analyzes the X-ray tube controller 5, aperture control motor driver 8, rotary motor driver 10, table motor driver 13, and Various control signals are output to the data collection unit 15.

The data collected by the data collector 15 is
It is sent to the operation console 200 via the interface 2b.

On the other hand, the operation console 200 is a so-called workstation, and as shown in the figure, a CPU 51 that controls the entire apparatus, a ROM 52 that stores a boot program, and a RAM 5 that functions as a main storage device.
3 and the following configurations are provided.

The HDD 54 is a hard disk device, and in addition to the OS, provides various instructions to the gantry device 100 and reconstructs an X-ray tomographic image based on the data received from the gantry device 100. Contains configuration programs. Further, the VRAM 55 is a memory for expanding the image data to be displayed, and by expanding the image data or the like here, it can be displayed on the CRT 56. Reference numerals 57 and 58 are a keyboard and a mouse for making various settings. Also, 59
And 60 are interfaces for communicating with the gantry device 100, and are connected to the interfaces 2a and 2b of the gantry device 100, respectively.

The configuration of the X-ray CT system in the embodiment is generally as described above. Next, the structure and operation of the X-ray tube 4, the aperture 6 and the X-ray detector 14 will be described with reference to FIGS. 2 and 3. This will be described in more detail.

FIG. 2 is a schematic view of the essential parts of the X-ray tube 4, aperture 6 and X-ray detector 14. These constituent elements are supported by a predetermined base portion of the gantry 3 and maintain the positional relationship shown in the drawing.

In the figure, the X-ray tube 4 is a housing 41.
Further, it has a structure in which a cathode sleeve 42 containing a focusing electrode and a filament and a rotating target 43 are incorporated, and an X-ray is emitted from a focus f. The X-rays emitted from the X-ray tube 4 are slits 6 formed by the apertures 6.
By passing a, a fan beam having a predetermined X-ray irradiation angle (fan angle) is formed. The X-ray detection unit 14 described above forms a single row of detectors with a number (for example, 1,000) of detection channels extending over a length depending on the fan angle, and the detectors are arranged in the z-axis direction (in the transport direction of the table 11). 2) are arranged, for example. Reference symbols A and B indicate detector arrays. The width of each of the detector rows A and B in the z-axis direction is d (for example, d = 1 mm). This realizes so-called multi-slice X-ray CT.

In the X-ray CT system having the above-mentioned structure, the projection data is collected as follows.

First, with the subject positioned in the cavity of the gantry 3, the position in the z-axis direction is fixed and the subject is irradiated with the X-ray beam from the X-ray tube 4 (projection of X-rays). The transmitted X-ray is detected by the X-ray detection unit 14. And this transmission X
The X-ray detection is performed for 360 degrees while rotating the X-ray tube 4 and the X-ray detection unit 14 around the subject (that is, while changing the projection angle). The detected transmission X-rays are converted into digital values by the data collection unit 15 and transferred to the operation console 200 via the interface 2b as projection data. A series of these steps is called one scan as a unit. Then, the scan position is sequentially moved in the z-axis direction by a predetermined amount, and the next scan is performed. Such a scanning method is called an axial scanning method,
While moving the scan position by moving the table 11 at a predetermined speed in synchronization with the change in the projection angle (the X-ray tube 4 and the X-ray detection unit 14 spirally orbit around the subject. ) A helical scan method of collecting projection data may be used.

The operation console 200 reconstructs an X-ray tomographic image by known processing based on the transferred projection data, and sequentially outputs the obtained X-ray tomographic image to the CRT 56.

Further, as described above, the X-ray detector 14 in the embodiment is provided with the two detector rows A and B arranged in the z-axis direction to realize the two-row multi-slice X-ray CT. That is, it is possible to collect projection data for two slices in one scan. Of course, for example, it is also possible to combine projection data for each detector to provide an X-ray tomographic image with a slice thickness corresponding to the detector widths of two rows. Further, the width of the slit 6a of the aperture 6 in the z-axis direction is controlled so that the X-rays are irradiated only to a part in the z-axis direction of each of the two rows of detectors A and B, and the X-thickness of a thinner slice thickness is controlled. It is also possible to generate a line tomographic image.

The aperture 6 can be changed by mechanically operating the width of the slit 6a in the z-axis direction (hereinafter simply referred to as the opening width). The control mechanism of the opening width of the aperture 6 will be specifically described below.

FIG. 3 is a diagram showing an example of a mechanism for controlling the opening width of the aperture 6 in the embodiment.

The aperture 6 is made of a member made of an X-ray shielding material such as lead, and as shown in the drawing, an X-ray in the z-axis direction of the X-ray emitted from the X-ray tube 4 is placed on the aperture base plate 61 having an opening. Shielding plates 62 and 63 for limiting the irradiation range are provided, and the shielding plates 62 and 63 are rotatably connected at their ends by link members 65a and 65b to form a parallel link mechanism. This allows the shields 62, 63 to remain parallel to each other. The gap between the two shield plates 62 and 63 forms the slit 6a. In addition, the link member 65
A rotating shaft is provided at the central position of each of a and 65b, and the rotating shaft on the side of the link member 65a has the opening width control motor 7.
Fixed to the output shaft of.

With this structure, the opening width control motor 7 is driven to rotate the rotating shaft, whereby the shield plates 62 and 63 are rotated.
Can gradually control the opening width of the slit 6c by gradually expanding or narrowing the interval while keeping the parallel.

However, the control mechanism described here is an example, and the present invention is not limited to this. Any other structure may be used.

By the way, in the X-ray CT system of the embodiment, it is possible to perform a scout scan for making a scan plan. The scout scan is, as described above, with the X-ray tube 4 fixed at a constant angle,
One fluoroscopic image is obtained from projection data obtained by continuously irradiating X-rays while gradually transporting the table 11 on which the subject is placed. After the scout scan, CRT
This perspective image (scout image) is displayed in a predetermined area of the scan planning screen displayed at 56. The operator can proceed with the scan plan while looking at this scout image.

Conventionally, the scout scan condition is fixed regardless of the purpose of photographing, but in the embodiment, the opening width of the aperture 6 and the conveying speed of the table 11 are controlled according to the purpose of photographing. .

FIG. 4 is a flow chart showing the processing contents of the scout scan in the embodiment. The processes of steps S1 to S3 of this flowchart described below are realized by an image generation program stored in the HDD 54 of the operation console 200, loaded into the RAM 53 after power-on, and executed by the CPU 51. The processing of steps S4 to S9 indicates the control processing performed in the gantry device 100. When the image generation program is started in the operation console 200, a scout scan planning screen as shown in FIG. 5, for example, is first displayed on the CRT 56, and the operator operates the keyboard 57 or the mouse 5 on the planning screen.
Make a plan using 8. In the planning screen shown in FIG. 5, the start position and the end position of the scout scan and the data collection mode described later can be set.

In step S1, a start position and an end position of scout scan with respect to a predetermined reference position are set.

Next, in step S2, a data acquisition mode (hereinafter referred to as a photographing mode) is set. The shooting modes include a high-speed mode for performing a scout scan at high speed and a high-definition mode for obtaining a higher-definition scout image.

Then, in step S3, it is determined whether or not a scout scan start instruction has been given, based on whether or not the start button on the planning screen is clicked using the mouse 58. When there is an instruction to start a scout scan,
Go to step S4.

In step S4, it is determined whether the set photographing mode is the high speed mode. If it is not the high speed mode, that is, if it is the high definition mode, step S5.
Then, the aperture width of the aperture 6 is set so that the X-ray irradiation width of each of the detector rows A and B is, for example, d / 2 (d is the width of each of the detector rows A and B in the z-axis direction as described above). To a width w1 such that
The transport speed of the table 11 is set to the speed s1 corresponding to w1.

On the other hand, if the set photographing mode is the high speed mode in step S4, the process proceeds to step S7.
The aperture width of the aperture 6 is set to X of each of the detector rows A and B.
Width w2 such that the line irradiation width is d, that is, 2 of W1
Set to double width. In step S8, the table 1
The transport speed of 1 is a speed s2 corresponding to w2, that is, s1
Set to twice the speed.

Then, in step S9, a scout scan is executed. Specifically, the aperture 6 is set to a width according to the set imaging mode, and the X-ray is conveyed while the table 11 is conveyed at a speed according to the set imaging mode while the X-ray tube 4 is fixed at a constant angle. Is continuously irradiated, and the X-ray detection unit 14 detects X-rays.

When the scout scan is performed in the high speed mode, the aperture width of the aperture 6 and the transport speed of the table 11 are set to twice as high as those in the high definition mode, so that the photographing time is shortened. You can In other words, the dose can be reduced by that much.
This is effective when performing a scout scan over a long imaging range in the z-axis direction.

On the other hand, when the scout scan is performed in the high-definition mode, the transport speed of the table 11 is half that in the high speed mode, so that the photographing time is longer than in the high speed mode, while the z of the scout image is taken. Since the resolution in the axial direction can be doubled, it is advantageous when it is necessary to position the scan position with high accuracy.

As described above, the operator can select the photographing mode depending on which of the resolution and the exposure dose is important.

In the above embodiment, the start position and the end position of the scout scan are set and the photographing mode is explicitly set on the scout scan planning screen shown in FIG. Besides this, for example,
Instead of setting the start position and end position of the scout scan itself, set a predetermined imaging part (head, lungs, etc.) of the subject, and set the imaging mode automatically according to the result. May be. For example, when the head is set as the imaging region, a high-definition scout image is required to perform highly accurate scan position positioning. Therefore, in this case, the high definition mode is set. On the other hand, for example, when the lung part is set as the imaging region, it is not necessary to position the scan position with higher accuracy than the head, but rather the imaging range is z.
Since the exposure dose may be a problem due to the long axial length, the high speed mode is set in this case.

[0045]

As described above, according to the present invention,
It is possible to provide an X-ray CT system and its control method capable of changing the imaging time of scout scan, exposure dose, or resolution according to the purpose of imaging.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an X-ray CT system according to an embodiment.

FIG. 2 is a schematic diagram showing an X-ray tube, an aperture, a table, and an X-ray detection unit in the embodiment.

FIG. 3 is a diagram showing an example of a control mechanism of an aperture opening width in the embodiment.

FIG. 4 is a flowchart showing the processing contents of scout scan in the embodiment.

FIG. 5 is a diagram showing a display example of a scout scan planning screen in the embodiment.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Horiuchi             127, 4-7 Asahigaoka, Hino City, Tokyo             GE Yokogawa Medical System Co., Ltd.             Within F term (reference) 4C093 AA21 BA17 CA02 CA18 CA34                       EA14 EB18 FA16 FA36 FA56

Claims (12)

[Claims] 1. An X-ray CT system, comprising: an X-ray generation source; and an X-ray detection unit having a plurality of detector rows arranged in a conveyance direction of a table for conveying an object. An aperture forming a slit for limiting an irradiation range of X-rays from a generation source, an aperture adjusting means for adjusting a width of the slit in the carrying direction, a speed adjusting means for adjusting a carrying speed of the table, And a perspective image data collecting unit that collects perspective image data by transporting the table while the position of the X-ray generation source is fixed, and the perspective image data collecting unit determines a predetermined data collection mode. Determination means, and control means for setting the width of the slit and the transport speed of the table according to the determined data collection mode to collect the fluoroscopic image data. X-ray CT system characterized and. 2. The data acquisition mode includes: a first mode in which the fluoroscopic image data is acquired at high speed; and a second mode in which the fluoroscopic image data is acquired with high precision. The X-ray CT system according to claim 1. 3. The control means, when the determined data acquisition mode is the first mode, irradiates the width of the slit with X-rays over the entire detector row of the plurality of rows. When the table is set to such a first width and the table conveyance speed is set to a speed according to the adjusted first width, and when the determined data collection mode is the second mode, , The width of the slit is X only for a predetermined part in the transport direction of each of the plurality of detector rows.
3. The X according to claim 2, wherein the second width is set such that a line is irradiated, and the transport speed of the table is set to a speed corresponding to the adjusted second width. X-ray CT system. 4. The X-ray CT system according to claim 1, further comprising mode setting means for setting the data acquisition mode. 5. The mode setting unit includes an imaging region setting unit that sets an imaging region of a subject, and sets a data acquisition mode based on the set imaging region. The described X-ray CT system. 6. An X-ray generation source, an X-ray detection unit having a plurality of rows of detectors arranged in a conveyance direction of a table for conveying an object, and an irradiation range of X-rays from the X-ray generation source. Method for controlling an X-ray CT system, comprising: an aperture that forms a slit for limiting the width of the slit; an aperture adjusting unit that adjusts the width of the slit in the carrying direction; and a speed adjusting unit that adjusts the carrying speed of the table. And a perspective image data collecting step of collecting perspective image data by transporting the table while the position of the X-ray generation source is fixed, and the perspective image data collecting step includes a predetermined data collection mode. And a control step of setting the width of the slit and the transport speed of the table according to the determined data collection mode to collect perspective image data. The method of X-ray CT system, characterized by. 7. The data acquisition mode includes a first mode in which the perspective image data is acquired at high speed, and a second mode in which the fluoroscopic image data is acquired with high precision. The X-ray CT system control method according to claim 6. 8. In the control step, when the determined data acquisition mode is the first mode, the width of the slit is irradiated with X-rays over the entire detector rows of the plurality of rows. When the table is set to such a first width and the table conveyance speed is set to a speed according to the adjusted first width, and when the determined data collection mode is the second mode, , The width of the slit is X only for a predetermined part in the transport direction of each of the plurality of detector rows.
8. The X according to claim 7, wherein the table is set to a second width such that a line is irradiated, and the transport speed of the table is set to a speed according to the adjusted second width. Method of controlling a line CT system. 9. The control method for an X-ray CT system according to claim 6, further comprising a mode setting step of setting the data acquisition mode. 10. The mode setting step includes an imaging region setting step of setting an imaging region of a subject, and a data acquisition mode is set based on the set imaging region. A method for controlling the X-ray CT system according to claim 1. 11. An X-ray generation source, an X-ray detection unit having a plurality of rows of detectors arranged in a transportation direction of a table for transporting an object, and an irradiation range of X-rays from the X-ray generation source. For controlling the X-ray CT system including an aperture for forming a slit for limiting the width of the slit, an aperture adjusting means for adjusting the width of the slit in the carrying direction, and a speed adjusting means for adjusting the carrying speed of the table. And a program code for a fluoroscopic image data collecting step of collecting the fluoroscopic image data by transporting the table while the position of the X-ray generation source is fixed. The program code is a program code of a judging step for judging a predetermined data collecting mode, and the width and the front of the slit depending on the judged data collecting mode. A program characterized by comprising: a program code of a control step of setting the transport speed of the table to perform the collection of fluoroscopic image data. 12. An X-ray generation source, an X-ray detection unit having a plurality of rows of detectors arranged in a transportation direction of a table for transporting an object, and an irradiation range of X-rays from the X-ray generation source. For controlling the X-ray CT system including an aperture for forming a slit for limiting the width of the slit, an aperture adjusting means for adjusting the width of the slit in the carrying direction, and a speed adjusting means for adjusting the carrying speed of the table. A storage medium storing a program for storing a program code of a perspective image data collecting step of collecting perspective image data by transporting the table while fixing the position of the X-ray generation source, The program code of the fluoroscopic image data collection process is based on the program code of the determination process for determining the predetermined data collection mode and the determined data collection mode. Storage medium comprising a program code of a control step of setting the conveying speed of the width and the table of the slit causes the collection of the perspective image data.