JP2003088517A - X-ray ct system, and operation console and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT system capable of providing an X-ray tomographic image of further high quality while ensuring the real time property in reconfiguration processing and display processing of the X-ray tomographic image, and operation console and control method therefor. SOLUTION: The rotating speed of a gantry rotation part 3 is set (S1), processing content related to the reconfiguration of the X-ray tomographic image are determined (S2), and the reconfiguration processing and display of the X-ray tomographic image including the processing of the determined contents are performed on the basis of projection data collected by scanning at the set rotating speed.

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 (Computeriz) for reconstructing an X-ray tomographic image of a subject by X-ray irradiation.
ed Tomography) system and its operation console and its control method.

[0002]

2. Description of the Related Art The main purpose of an X-ray CT system is to collect projection data obtained from X-rays transmitted through a subject and provide an X-ray tomographic image reconstructed from the projection data. Specifically, first, the subject is laid on a table device and transported toward the cavity of the gantry device. Then, the gantry rotating part (in which the X-ray tube and the X-ray detector are integrally attached) of the gantry device is rotationally driven to irradiate the subject with X-rays from different angles, and at each angle. The X-ray transmitted through the subject is detected. Then, the operation console receives the detected data (projection data), reconstructs the X-ray tomographic image by arithmetic operation, and displays it on the monitor.
The above-described series of steps for detecting X-rays is generally called a scan.

The X-ray CT system is generally constructed so that the rotational speeds of a plurality of gantry rotating parts (hereinafter, also referred to as "scan speeds") can be set according to the purpose of inspection. Further, during execution of the scan, X-ray tomographic images of a predetermined number of frames per one rotation of the gantry rotating part are displayed on the monitor in real time. That is, the operation console is designed to ensure real-time reconstruction and display of X-ray tomographic images even at the highest scanning speed.

[0004]

While securing such real-time processing is required, it is also required to improve the image quality of the displayed X-ray tomographic image. But,
Under restricted hardware conditions, there is generally a trade-off relationship between speeding up image processing and improving image quality, and it is not easy to achieve both at the same time.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an X-ray tomographic image of higher image quality while ensuring real-time processing of X-ray tomographic image reconstruction processing and display processing. It is an object of the present invention to provide an X-ray CT system, an operation console and a control method for the same.

[0006]

In order to achieve the above object, for example, an X-ray CT system of the present invention has the following configuration. That is, the X-ray generation source includes a gantry rotating unit configured to rotate around the subject, performs a scan for collecting projection data of the subject, and outputs an X-ray tomographic image based on the collected projection data. A setting means for setting a value based on the time at which an X-ray tomographic image should be displayed after starting scanning, and reconstructing the X-ray tomographic image according to the set value. Determination means for determining the processing content related to the above, and image reconstruction / display means for performing image reconstruction and display including processing of the content determined by the determination means based on the collected projection data. It is characterized by

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of the X-ray CT system according to the embodiment. In this system, the gantry device 100 for irradiating the subject with X-rays and detecting the X-rays transmitted through the subject, and various operation settings for the gantry device 100 are output from the gantry device 100. The operation console 200 reconstructs and displays an X-ray tomographic image based on the data.

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

Reference numeral 2 is an interface for communicating with the operation console 200, and 3 is a subject (patient) laid on the table 11 (in the direction perpendicular to the drawing, hereinafter referred to as z axis, generally referred to as the patient's body). It is a gantry rotating part (hereinafter, simply referred to as “gantry”) having a cavity for matching the axis. 4 is an X-ray tube which is an X-ray source,
The drive is controlled by the X-ray tube controller 5.

6 is an aperture having an opening for limiting the X-ray irradiation range, 7 is an aperture motor for adjusting the aperture width of the aperture 6, and 8 is an aperture motor 7.
It is an aperture motor driver that controls the drive of the.

Reference numeral 9 is a rotary motor for rotating the gantry 3, and 10 is a rotary motor driver for driving the rotary motor 9. Reference numeral 11 is a table on which a subject is placed, 12 is a table motor for transporting the table 11 in the z-axis direction, and 13 is a table motor driver for controlling the drive of the table motor 12.

Reference numeral 14 is an X-ray detector for detecting X-rays from the X-ray tube 4 that has passed through the aperture 6 and the cavity of the gantry 3. The X-ray detection unit 14 uses the aperture 6
Has a plurality of (for example, 1,000) detection channels over a length depending on the X-ray irradiation range defined by
An X-ray beam is normally directly incident on the detection channel located at the end of the detection channel without passing through the subject, and is used as a reference channel. 15
Collects the projection data obtained from the X-ray detection unit 14,
It is a data collection unit for converting into digital data.

On the other hand, the operation console 200 is a so-called work station, and as shown in the figure, has a CPU 51 for controlling the entire apparatus, a ROM 52 storing a boot program and the like, and the following components.

Reference numeral 53 is a RAM which functions as a main storage device. A buffer area 53a for temporarily storing projection data transferred from the gantry device 100 is secured in the RAM 53, as shown in the figure.

The HDD 54 is a hard disk device, and in addition to the OS, it gives various instructions to the gantry device 100, and a diagnostic program for reconstructing an X-ray tomographic image based on the data received from the gantry device 100. Is stored. The HDD 54 also stores a table (details will be described later) describing a combination of processes additionally applied for each scan speed. 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. 57
Reference numerals 58 and 58 are a keyboard and a mouse for making various settings. Reference numeral 59 is an interface for communicating with the gantry device 100.

The configuration of the X-ray CT system in this embodiment is generally as described above. In the X-ray CT system having such a configuration, projection data is collected (scanned) as follows.

First, the operator (engineer or doctor) operates the operation console 200 to set various scan conditions (scan plan) and then gives a scan start instruction. The diagnostic program running on the operation console 200 uses the gantry device 100 (main controller 1) according to the set scan conditions.
Issue various control commands to. Gantry device 1
The main controller 1 of 00 will give a control signal to the X-ray tube controller 5, the aperture motor driver 8, the rotary motor driver 10, and the table motor driver 13 in accordance with this control instruction command.
As a result, the X generated in the X-ray tube 4 and transmitted through the subject
It becomes possible to detect the line by the X-ray detection unit 14 and obtain the projection data from the data collection unit 15.

Specifically, the gantry 3 is rotated once while the table 11 is stopped being conveyed, and during that time, the X-ray beam from the X-ray tube 4 is emitted from a plurality of 360-degree (for example, 1,000) view directions. Irradiation (projection of X-rays) on the subject and detection of the transmitted X-rays by the X-ray detector 14 are repeated. Each of the detected transmitted X-rays is converted into a digital value by the data collection unit 15 and transferred to the operation console 200 via the main controller 1. This series of operations is called one scan as one 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, but the table 1 is rotated according to the rotation of the gantry 3.
1 while continuously moving (X-ray tube 4 and X-ray detector 1
4 and 4 will spiral around the subject.)
A helical scan method, which collects projection data, may be used.

The diagnostic program operating on the side of the operation console 200 performs a process of reconstructing an X-ray tomographic image by a known process based on the transferred projection data,
The results will be sequentially displayed on the CRT 56.

The X-ray CT in the above embodiment
The system sets the gantry 3 to one of a plurality of rotation speeds (scan speeds), for example, 0.7 [sec / rot.] And 1.0 [sec / ro.
It can be rotated by either t.] or 1.5 [sec / rot.]. The unit "sec / rot." Represents the time required for one rotation of the gantry 3. Then, the operator can select the scan speed in accordance with the inspection purpose or the like when planning the scan.

Now, in the X-ray CT system in the embodiment, during the execution of the scan, the X-ray tomographic image of a predetermined number of frames, for example, 6 frames, is C every time the gantry 3 makes one rotation.
The images are sequentially displayed on the RT 56 in real time. In order to realize this, the X-ray tomographic image displayed on the CRT 56 is set to be updated and displayed on the latest reconstructed X-ray tomographic image every time the gantry 3 rotates 1/6. . It will be understood that this update time interval is the display time allowed for one frame (one) of the X-ray tomographic image. Then, the update time interval is set according to the scan speed. So the scan speed is
It can be used as an index value corresponding to the display time allowed per frame (one image) of the X-ray tomographic image.

In the following, the number of frames displayed per one rotation of the gantry 3 is referred to as "frame rate".
It is expressed in the unit of "frame / rot.".

In order to reconstruct an X-ray tomographic image, projection data for one rotation of the gantry is not necessarily required. For example, an X-ray tomographic image can be obtained with projection data for one-half rotation of the gantry. It is known that it can be reconfigured. Therefore, in the embodiment, 1 / th of the gantry 3
By performing image reconstruction processing with projection data for two rotations, 6
Realize the frame rate of [frame / rot.].

Specifically, first, the main controller 1 of the gantry apparatus 100 that executes a scan acquires projection data for each 1/6 rotation of the gantry 3 from the data collection unit 15 and sequentially transfers it to the operation console 200. To do. The projection data transferred to the operation console 200 is stored in the buffer 5
3a is stored. In the buffer 53, the gantry device 1
The latest projection data for 1/2 rotation (= 3/6 rotation) of the gantry 3 transferred from 00 is always stored. Therefore, every time 1/6 rotation projection data of the gantry 3 is transferred from the gantry device 100, the oldest 1/6 rotation projection data in the buffer area is discarded and transferred. The projection data for the rotation is newly stored. CP
The U51 performs image reconstruction processing based on the projection data stored here, and performs display processing on the CRT 56.

In order to secure the real-time property, it is necessary to complete the image reconstruction processing and display processing by the time the projection data for the next 1/6 rotation is transferred. Since the maximum scanning speed in the embodiment is 0.7 [sec / rot.] As described above, one frame (1
The time required for image reconstruction processing and display processing per (sheet) is 0.7 / 6≈0.117 [sec]. Therefore, the image reconstruction process and the display process are designed to fit within this time constraint.

By the way, as described above, it is desired to improve the image quality of the displayed X-ray tomographic image while ensuring the above real-time display. However, under limited hardware conditions, there is generally a trade-off relationship between speeding up image processing and improving image quality, and it is not easy to achieve both at the same time.

Therefore, the present inventor, as described above,
Since the image reconstruction processing and display processing per frame are designed based on the maximum scanning speed, we paid attention to the fact that there is a margin in processing time when the scanning speed is slowed down.

For example, when a scan is performed at a scan speed of 1.0 [sec / rot.], The time required for image reconstruction processing and display processing per frame is 1.0 / 6≈.
Where it is 0.167 [sec], it is actually 0.7 [sec /
Since it is processed in 0.1167 [sec] when the scanning speed is rot.], a margin time of 0.117-0.167 = 0.05 [sec] is created.

The present invention is characterized in that a predetermined process for improving the image quality is applied in this margin time.

Next, the processing in the X-ray CT system according to the embodiment will be described with reference to the flowchart of FIG.
The program corresponding to this flowchart is stored in the hard disk 54 of the operation console 200, loaded into the RAM 53 after power-on, and executed by the CPU 51.

First, a scan plan is prepared on the operation console 200 (step S1). Generally, various scanning conditions are set through a GUI (a user interface that allows a setting screen to be displayed on the CRT 56 and to be input using the keyboard 57 or the mouse 58) provided by a diagnostic program. But
Since the scan plan itself is a known one, its details are omitted. The scan conditions in the embodiment include, for example, slice thickness, tube current supplied to the X-ray tube 4,
The specification of the scan speed shall be included. The set scan conditions are stored in the RAM 53.

When the scan plan in step S1 is completed,
Next, the content of the process relating to image reconstruction corresponding to the set scan speed is determined as an index value corresponding to the display time allowed for each X-ray tomographic image (step S2).

For example, a table having a structure as shown in FIG. 3 is created in the HDD 54, and the type of processing relating to image reconstruction corresponding to the set scan speed is determined by referring to this table. In the figure, ◯ indicates that the process is executed, and x indicates that the process is not executed. Then, at each scan speed, a combination of processes marked with a circle is executed.

For example, when the scan speed is set to 0.7 [sec / rot.], There are no processes marked with ◯ and all marked with ×, so none of the processes listed in this table are executed. . Scan speed is 1.0 [sec / ro
When set to [t.], reference correction with ○ (correction that normalizes each channel output with the output value of the reference channel) and beam hardening (Beam Hardning)
Correction is performed, and other processes marked with “X” are not performed. When the scan speed is set to 1.5 [sec / rot.], All the processes described in the table (reference correction, radiation hardening correction, scattered X-ray correction, and streak artifact removal correction) are performed. I will decide.

That is, in this embodiment, the number of combinations of processes related to image reconstruction increases as the scanning speed decreases.

Further, with reference to the table shown in FIG. 3, the matrix size for image reconstruction is determined.
For example, as shown in the figure, when the scan speed is set to 0.7 [sec / rot.], It is 256 x 256 pixels and the scan speed is 1.0.
320 x 320 pixels when set to [sec / rot.] and 5 when scan speed is set to 1.5 [sec / rot.]
Image reconstruction processing will be performed with 12 × 512 pixels. The resolution is increased as the matrix size is increased, and the image quality of the reconstructed image is expected to be improved, while the calculation amount of the image reconstruction process is also increased.

Next, the gantry apparatus 100 is instructed to perform scanning under the scanning conditions planned in step S1 by using a predetermined input from the mouse 57 or the keyboard 58 as a trigger (step S3). Gantry device 1
At 00, the scan is performed in response to this instruction.
At this time, of course, the gantry 3 rotates at the set scan speed. Then, the projection data transferred from the gantry device 100 every 1/6 rotation of the gantry 3 is received (step S4), and the contents of the buffer 53a are updated with the received data (step S5).

After that, the CPU 5 of the operation console 200
1 executes the image reconstruction process including the process of the contents determined in step S2 (step S6). Further, after being converted into a CT value that fits within a predetermined contrast scale (step S7), it is displayed on the CRT 56 as an X-ray tomographic image (step S8).

In step S9, it is determined whether or not there is data transferred from the gantry device 100, and if there is data, the process returns to step S4 and repeats. This process ends as soon as there is no transfer data.

According to the above-described embodiment, a predetermined process for improving the image quality is additionally applied according to the margin time required for the image reconstruction process and the display process caused by the scanning speed. It has become possible to improve the image quality without impairing the real-time display of the line tomographic image.

In the above-described embodiment, under the premise that real-time display update speed of the X-ray tomographic image is ensured when scanning is continuously performed, for example, image reconstruction is performed according to the scan speed. The example of determining the content of the process related to is shown.

However, according to the present invention, for example, the scanning is not performed continuously but only once, and after a predetermined time has elapsed (for example, 2 seconds) from the start of the scanning.
It can also be applied to the case of displaying an X-ray tomographic image on the display. That is, in consideration of each scan, the X-ray CT system that realizes the present invention directly or indirectly sets the time at which the X-ray tomographic image should be displayed after starting the scan, and (Or a value based on the time), the processing content related to the image reconstruction is determined.

Further, most of the control of the X-ray system in the embodiment is performed by the operation console 200.
The configuration itself of the operation console 200 is a general-purpose information processing device (workstation, personal computer, etc.)
It is also possible to install the software that realizes the functions of the above-described embodiments in the same device and realize the software therewith.

That is, an object of the present invention is to supply a storage medium recording the program code of the above software to an apparatus, and a computer (or CPU or MPU) of the apparatus reads and executes the program code stored in the storage medium. Needless to say, this can also be achieved by doing.
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment,
The storage medium storing the program code constitutes the present invention.

When the present invention is applied to the above storage medium, the storage medium stores the program code for realizing the processing according to the flowchart shown in FIG. 2 described above.

As a storage medium for storing such a program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, C
D-ROM, magnetic tape, non-volatile memory card, R
OM or the like can be used. Further, it may be downloaded via a medium such as a network (for example, the Internet).

[0046]

As described above, according to the present invention,
It is possible to provide an X-ray CT system, an operation console and a control method for the X-ray CT system, which can provide a higher-quality X-ray tomographic image while ensuring real-time reconstruction and display processing of the X-ray tomographic image. .

[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 flowchart showing a process in the embodiment.

FIG. 3 is a diagram showing an example of a table describing a combination of processes additionally applied for each scan speed in the embodiment.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akira Hagiwara             127, 4-7 Asahigaoka, Hino City, Tokyo             GE Yokogawa Medical System Co., Ltd.             Within F term (reference) 4C093 AA22 BA03 CA29 FA12 FA42                       FE30

Claims (20)

[Claims] 1. An X-ray source comprising an gantry rotating unit configured to rotate around a subject, performing a scan for collecting projection data of the subject, and X-ray tomography based on the collected projection data. An X-ray CT system for outputting an image, comprising: setting means for setting a value based on a time at which an X-ray tomographic image should be displayed after starting scanning; and an X-ray tomographic image according to the set value. Determining means for determining the processing content related to the reconstruction of the image, and image reconstruction / display means for performing image reconstruction and display including the processing of the content determined by the determining means based on the collected projection data. An X-ray CT system comprising: 2. The X-ray CT system according to claim 1, wherein the value is a rotation speed of the gantry rotation unit. 3. The X-ray CT system according to claim 1, wherein the determining unit determines a matrix size of the image reconstruction processing according to the set value. 4. The X-ray CT system according to claim 3, wherein the determining unit determines a larger matrix size as the rotation speed of the gantry rotating unit as the value becomes slower. 5. The storage device further includes a storage unit that stores a table describing a correspondence relationship between the value and a combination of processes related to reconstruction of an X-ray tomographic image, and the determination unit refers to the table. 5. The X-ray CT system according to claim 1, wherein the processing content related to the reconstruction of the X-ray tomographic image according to the value is determined. 6. The combination of the processes related to the reconstruction of the X-ray tomographic image corresponding to each of the values in the table is the X-ray tomographic image with a predetermined number of frames per one rotation of the gantry rotating unit, 6. The X according to claim 5, which is a combination that can be displayed in real time.
X-ray CT system. 7. The processing related to the reconstruction of the X-ray tomographic image includes reference correction, radiation hardening correction, scattered X-ray correction,
And at least one of streak artifact removal correction.
X-ray CT system. 8. The number of processes included in the combination in the order of reference correction, radiation hardening correction, scattered X-ray correction, and streak artifact removal correction as the rotation speed of the gantry rotation unit as the value becomes slower. X-ray CT according to claim 7, characterized in that
system. 9. An X-ray tomographic section based on the collected projection data, wherein the X-ray source includes a gantry rotating unit configured to rotate around the object, performs a scan for collecting projection data of the object, A method of controlling an X-ray CT system for outputting an image, comprising: a setting step of setting a value based on a time at which an X-ray tomographic image should be displayed after a scan is started; and an X value according to the set value. A determination step of determining the processing content related to the reconstruction of the line tomographic image, and an image reconstruction / display operation that performs image reconstruction and display including processing of the content determined in the determination step based on the collected projection data. A method for controlling an X-ray CT system, comprising: 10. An X-ray generation source comprising a rotating unit configured to rotate around a subject, connected to a gantry device for performing a scan for collecting projection data of the subject, and to the gantry device for scanning. An operation console in an X-ray CT system, which transmits the relevant information and outputs an X-ray tomographic image based on the projection data transferred from the gantry apparatus, and displays the X-ray tomographic image after starting the scan. Setting means for setting a value based on the time to be performed, determining means for determining the processing content related to the reconstruction of the X-ray tomographic image according to the set value, and the projection transferred from the gantry apparatus An image reconstructing / displaying unit for performing image reconstructing and displaying including processing of the content determined by the determining unit based on the data; Console. 11. The operation console according to claim 10, wherein the value is a rotation speed of the rotating portion. 12. The operation console according to claim 10, wherein the determining unit determines the matrix size of the image reconstruction according to the set value. 13. The operation console according to claim 12, wherein the determining unit determines a larger matrix size as the rotation speed of the rotating unit as the value becomes slower. 14. The storage device further includes a storage unit that stores a table describing a correspondence relationship between the value and a combination of processes related to reconstruction of an X-ray tomographic image, and the determination unit refers to the table. 14. The operation console according to claim 10, wherein the processing content related to the reconstruction of the X-ray tomographic image is determined according to the value. 15. The combination of the processes related to the reconstruction of the X-ray tomographic image corresponding to each of the values in the table is performed in real time by a predetermined number of X-ray tomographic images per one rotation of the rotating unit. The operation console according to claim 14, which is a displayable combination. 16. The process related to the reconstruction of the X-ray tomographic image includes at least one of reference correction, radiation hardening correction, scattered X-ray correction, and streak artifact removal correction. The operation console according to claim 15. 17. A reference correction, a radiation hardening correction, as the rotation speed of the rotating portion as the value becomes slower,
The operation console according to claim 16, wherein the number of processes included in the combination increases in the order of the scattered X-ray correction and the streak artifact removal correction. 18. An X-ray source comprising a rotating unit configured to rotate around a subject, connected to a gantry device for performing a scan for collecting projection data of the subject, and the gantry device for scanning. A method for controlling an operation console in an X-ray CT system, which transmits the relevant information, and outputs an X-ray tomographic image based on the projection data transferred from the gantry apparatus, the method including: A setting step of setting a value based on the time at which the image should be displayed; a determining step of determining processing contents related to reconstruction of an X-ray tomographic image according to the set value; An image reconstruction / display step of performing image reconstruction and display including processing of the content determined by the determination means based on the received projection data. The method of operating console, characterized in that. 19. An X-ray generation source comprising a rotating unit configured to rotate around a subject, connected to a gantry device for performing a scan for collecting projection data of the subject, and to the gantry device for scanning. A program for controlling an operation console in an X-ray CT system, which transmits the information and outputs an X-ray tomographic image based on the projection data transferred from the gantry apparatus, which is a program for starting an X-ray after starting a scan. A setting step for setting a value based on the time at which the tomographic image should be displayed; a determining step for determining the processing content related to the reconstruction of the X-ray tomographic image according to the set value; and a transfer from the gantry apparatus. An image reconstruction / display step of performing image reconstruction and display including processing of the content determined by the determination means based on the projection data that has been obtained; , A program to execute. 20. A storage medium storing the program according to claim 19.