JP2004208952A - X-ray ct system and image processing method in the ct system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT system that can make a scanning program without reperforming any scout scanning even when a change occurs in the height of a table after performing scout scanning. <P>SOLUTION: This X-ray CT system generates an X-ray image of a subject placed on the table by irradiating the subject with X-rays generated from an X-ray tube. This CT system is provided with a reading means which reads the information on the height of the table and a displaying means which displays the generated X-ray image on prescribed coordinates based on the information on the height of the table. The displaying means moves the displayed X-ray image relatively to the coordinates based on the fluctuation of the height of the table (steps S603-S605) when the height of the table fluctuates from the value at the time of generating the X-ray image after the X-ray image is generated (steps S601 and S602). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray CT (Computerized Tomography) apparatus that generates an X-ray image of a subject obtained by X-ray irradiation.
[0002]
[Prior art]
An X-ray CT apparatus scans a patient (subject) by irradiating the patient with X-rays from a plurality of directions, and performs image reconstruction processing based on projection data obtained from X-rays from each direction transmitted through the patient. , To provide an X-ray tomographic image of the examination site. Prior to such a scan or the like, the operator needs to make a plan for scan conditions and image reconstruction processing in accordance with an inspection part and an inspection purpose. Such a plan is generally called a scan plan, and the X-ray CT apparatus provides a user interface for the scan plan on an operation console.
[0003]
Then, usually, a scout scan is performed in advance in preparing a scan plan. A scout scan is a table on which a subject is placed while the subject is laid on the table and the X-ray tube is fixed at a predetermined position (that is, the gantry is not rotated and fixed at a fixed projection angle). Is obtained from projection data (perspective image data) obtained by continuously irradiating X-rays while gradually transporting the subject.
[0004]
The scout image obtained by the scout scan is displayed on the scan plan screen, and the operator can make a scan plan with reference to the scout image. To 3). Specifically, the operator sets the scan start position and the scan end position so that the part to be inspected enters the scan range while viewing the scout image. Further, a gantry tilt angle with respect to a part to be inspected is determined based on the scout image (generally, a gantry in an X-ray CT apparatus has a gantry tilt (tilt) mechanism for adjusting a scan slice angle with respect to a subject). The gantry tilt angle must be set when planning a scan.)
[0005]
[Patent Document 1]
JP 07-227391 A [Patent Document 2]
JP 2001-212137 A [Patent Document 3]
Japanese Patent Application Laid-Open No. 2002-177261
[Problems to be solved by the invention]
However, there is a limit to the gantry tilt angle. This is because, when tilting the gantry rotating section, if the gantry tilt angle is too large, the table and a patient placed on the table will interfere with the gantry rotating section. The limit of the gantry tilt angle varies depending on the height of the table, and generally, the limits of the gantry tilt angle (FWD limit and BWD limit) according to the table height are displayed on the scan plan screen (“ The "FWD limit" indicates the limit of the gantry tilt angle in the forward direction of the gantry rotating unit, and the "BWD limit" indicates the limit of the backward tilt angle of the gantry rotating unit.
[0007]
For this reason, when it is not possible to scan at a desired slice angle with the table height at the time of the scout scan, the operator changes the table height in order to increase the limit of the gantry tilt angle.
[0008]
However, if the table height is changed after the scout image is collected, there is a problem that a scout scan needs to be performed again in order to obtain a scout image in the changed state.
[0009]
This is because if a scan plan is made based on the scout image before changing the table height, various inconveniences occur due to a difference between the position of the subject on the image and the actual position of the subject. is there. For example, when performing a helical scan at a predetermined gantry tilt angle, if the scan start position and the scan end position are set based on the scout image before changing the table height, the actual scan start position on the subject is set. In addition, a deviation from the scan end position occurs, and a scanned image in a desired inspection range cannot be obtained.
[0010]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and enables a scan plan to be made without re-executing a scout scan even when a change in table height occurs after a scout scan is performed. An object is to provide a line CT apparatus.
[0011]
[Means for Solving the Problems]
An X-ray CT apparatus according to the present invention for solving such a problem has the following configuration.
That is,
An X-ray CT apparatus configured to irradiate an X-ray generated from an X-ray tube to a subject placed on a table to generate an X-ray image of the subject,
Reading means for reading information about the height of the table,
Display means for displaying the generated X-ray image on predetermined coordinates based on information on the height of the table,
The display means,
When the predetermined table height at the time of generation of the X-ray image fluctuates after the generation of the X-ray image, the displayed X-ray image is converted to the predetermined X-ray image based on the fluctuation amount of the table height. Is moved relatively to the coordinates of.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be noted that the same reference numerals indicate the same or corresponding parts throughout the drawings.
[0013]
<Overall system configuration>
FIG. 1 is a system configuration diagram of an X-ray CT apparatus according to an embodiment of the present invention.
In an X-ray CT apparatus, an X-ray source that generates X-rays rotates around a subject (patient), and X-rays at different irradiation angles transmitted through the patient are detected by an X-ray detector. The image (X-ray tomographic image) of the tomographic plane (the plane at the slice position, that is, the slice plane) of the X-ray irradiation site is obtained (reconstructed) by computer processing on the operation console.
[0014]
As shown in FIG. 1, the X-ray CT apparatus includes a gantry 120 for irradiating a subject (patient) with X-rays and detecting X-rays transmitted through the placed subject, and instructs the gantry 120. The operation console 100 for transmitting signals and performing various settings, reconstructing an X-ray tomographic image or generating a transmission image based on the projection data output from the gantry 120, and displaying the operation console 100, and mounting the subject. And a transfer device 140 for transferring the inside of the gantry.
[0015]
The gantry 120 has the following configuration including a main controller 122 that controls the entire system.
[0016]
Reference numeral 121 denotes an interface for performing communication with the operation console 100, 132 denotes a gantry rotating unit, and includes therein an X-ray tube 124 for generating X-rays (controlled by an X-ray tube controller 123), an X-ray The collimator 127 for defining the irradiation range of the collimator 127, the adjustment of the slit width for defining the X-ray irradiation range of the collimator 127, and the Z-axis direction of the collimator 127 (the direction perpendicular to the drawing, that is, A collimator motor 126 is provided for adjusting the position (in the direction in which the paper is conveyed toward). The driving of the collimator motor 126 is controlled by a collimator controller 125.
[0017]
The gantry rotating unit 132 includes an X-ray detection unit 131 that detects X-rays transmitted through the subject, and a data collection unit 130 that collects projection data obtained by the X-ray detection unit 131.
[0018]
The X-ray tube 124, the collimator 127, and the X-ray detection unit 131 are provided at positions facing each other with the hollow portion 133 interposed therebetween. It works. This rotation is performed by a rotation motor 129 whose rotation speed is controlled at a predetermined control cycle by a drive signal from a rotation motor controller 128.
[0019]
Further, the gantry 120 has a structure (not shown) for tilting the gantry rotating unit 132.
[0020]
Further, the transport device 140 has a top plate 142 on which the subject is actually placed, a table 143 including the top plate 142 and a table holding the top plate, and a base 144 supporting the table 143. The top board 142 is driven in the Z-axis direction by the top board motor 141 (that is, the top board conveyance direction = Z-axis direction), and the driving of the top board motor 141 is determined based on a drive signal from the top board motor controller 134. The transport speed is controlled in the control cycle. The table 143 can be raised and lowered by a table lifting motor 145 and operates based on a drive signal from a table lifting motor controller 136, while a table height sensor (for example, an encoder) built in the table lifting motor. Thereby, the height position of the table 143 is detected.
[0021]
The main controller 122 analyzes various instruction signals received via the I / F 121, and based on the analysis, based on the X-ray tube controller 123, the collimator controller 125, the rotary motor controller 128, the top motor controller 134, and the table lift Various control signals are output to the motor controller and the data collection unit 130 (further, a tilt command of the gantry rotation unit 132 is also sent from the main controller 122). The main controller 122 also performs a process of transmitting the projection data collected by the data collection unit 130 to the operation console 100 via the I / F 121.
[0022]
The operation console 100 is a so-called workstation, as shown in the figure, including a CPU 105 that controls the entire apparatus, a ROM 106 that stores a boot program and the like, a RAM 107 that functions as a main storage device (memory), and the following components. Is provided.
[0023]
The HDD 108 is a hard disk device in which an OS and a diagnostic program for controlling the entire X-ray CT device are stored. Note that a control program for realizing the image processing method according to the present invention on the operation console 100 is also stored in the HDD 108. Then, the CPU 105 reads and executes the control program, whereby the image processing method according to the present invention is achieved. In this case, the program code itself read from the HDD 108 implements the image processing method, and the HDD 108 storing the program code constitutes the present invention.
[0024]
Return to FIG. The VRAM 101 is a memory for developing image data (256 × 256 pixels) to be displayed. By expanding the image data and the like in this memory, the CRT 102 can display an X-ray tomographic image and a scout image. Reference numerals 103 and 104 denote a keyboard and a mouse for performing various settings. An interface 109 communicates with the gantry 120.
[0025]
<Overall processing flow in X-ray CT apparatus>
The configuration of the X-ray CT apparatus in the embodiment is generally as described above, but the outline of the entire processing in the X-ray CT apparatus having such a configuration is as shown in the flowchart of FIG. The flowchart is divided into a process (a) performed by the operation console 100 and a process (b) performed by the gantry device 120.
[0026]
First, the subject is laid on the table 143 to perform positioning for imaging (step S201). As soon as the alignment is completed, a scout scan is performed. Scout scan means that the top plate 142 on which the subject is placed is gradually moved while the X-ray tube 124 is fixed at a predetermined position (that is, the gantry rotation unit 132 is not rotated and the projection angle is fixed at a fixed projection angle). A single fluoroscopic image of a subject (a scout image) is obtained from projection data (fluoroscopic image data) obtained by continuously irradiating X-rays while being conveyed.
[0027]
In performing the scout scan, first, a scout scan is planned on the operation console 100 side, and thereafter, an execution command is issued to the gantry device 120 (step S210). The scout scan condition setting and execution command are performed, for example, via a setting screen 300 (displayed on the CRT 102 of the operation console 100) as shown in FIG.
[0028]
As shown in the figure, in the scout scan setting column, a start position and an end position of the scout scan with respect to a predetermined reference position, a tube voltage and a tube current applied to the X-ray tube 124, and a projection angle can be set. In order to obtain the above-described subject fluoroscopic image, after inputting the projection angle “0” in the scout scan setting field, the user presses the start button 302 for executing the scout scan to execute the scout scan.
[0029]
Upon receiving the scout scan execution command, the gantry 120 performs the scout scan in accordance with the above-described settings (step S202). The fluoroscopic image data by the scout scan is transferred to the operation console 100 side. The operation console 100 generates a scout image based on the received fluoroscopic image data (step S211), and displays the scout image on a scan plan screen (step S212. Details will be described later).
[0030]
When the scout image is displayed, the flow advances to step S213 to make a scan plan. The scan plan is performed on a scan plan screen displayed on the CRT 102 (step S213). A detailed description of the scan plan will be described later.
[0031]
After the scan plan is completed, collection (scanning) of projection data is started according to a scan execution instruction (step S214) by the operator (step S204). Scanning is performed as follows. First, the position in the z-axis direction is fixed, and an X-ray beam from the X-ray tube 124 is irradiated onto the subject (X-ray projection), and the transmitted X-ray is detected by the X-ray detection unit 131. The detection of the transmitted X-rays is performed in a plurality of (for example, 1000) view directions while rotating the X-ray tube 124 and the X-ray detector 131 around the subject (that is, changing the projection angle). Perform 360 degrees. This is called one scan as one unit. Each of the detected transmitted X-rays is converted into a digital value by the data collection unit 130 and transferred to the operation console 100 via the main controller 122 as projection data. Then, the scan position is sequentially moved in the z-axis direction by a predetermined amount, and the next scan is performed. Such a scan method is called an axial scan method, and moves the scan position in synchronization with a change in the projection angle (the X-ray tube 124 and the X-ray detection unit 131 circulate in a spiral around the subject). A helical scan method for collecting projection data may be used.
[0032]
Every time one scan is completed, the operation console 100 reconstructs an X-ray tomographic image based on the transferred projection data (step S215), and outputs and displays it on the CRT 102 (step S216).
[0033]
<Scout image display processing>
FIG. 4 is a flowchart showing a detailed flow of the scout image display processing in the operation console 100 shown in step S212.
[0034]
In step S401, the value of the table height sensor is read. In step S402, an FWD limit and a BWD limit are calculated based on the read sensor values. Note that a method of calculating the tilt range (FWD limit, BWD limit) of the gantry rotating unit 132 based on the height position of the table 143 is known, and thus the description is omitted here. In step S403, the display position of the scout image at the coordinates in the display area of the CRT 102 is calculated based on the sensor value.
[0035]
In step S404, the scout image is displayed at the display position at the calculated coordinates in the display area together with the FWD limit and the BWD limit.
[0036]
FIG. 7A is a diagram illustrating a state in which a scout image is displayed on a scan plan screen 700 displayed on the CRT 102. Referring to FIG. 7, reference numeral 701 denotes a display area for displaying a scout image obtained by the scout scan in step S211 described above.
[0037]
<Scan plan input processing>
FIG. 5 is a flowchart showing a detailed flow of the scan plan input process (step S213) in the operation console. Note that here, only the processing related to the input of the “gantry tilt angle” on the scan plan screen 700 will be described.
[0038]
In step S501, the presence or absence of a setting input of “gantry tilt angle” is confirmed.
When a set value is input to “Gantry tilt angle”, the process proceeds to step S502, and is compared with the FWD limit and the BWD limit calculated in step S502 in FIG.
[0039]
If the set “gantry tilt angle” is within the range of the FWD limit and the BWD limit, the process ends. On the other hand, if it is not within the range of the FWD limit or the BWD limit, the process advances to step S503 to calculate and display the table height required to realize the set “gantry tilt angle” (see FIG. 7A). .
[0040]
In step S503, the table height for realizing the desired gantry tilt angle is displayed, and the operator operates to change the table height based on the display. Therefore, in step S504, it is checked whether the table has been moved up and down. On the other hand, if the height of the table has been changed, the process proceeds to step S505, and a shift process of the scout image is performed.
[0041]
<Scout image shift processing>
FIG. 6 is a flowchart showing a detailed flow of the scout image shift processing in the operation console 100.
[0042]
In step S601, the current sensor value of the table height sensor is read, and the sensor value read in step S401 in FIG. 4 (that is, the sensor value of the table height sensor when the scout image is first displayed in step S212). ).
[0043]
In step S602, a fluctuation amount of the table height is calculated based on the read sensor values.
[0044]
In step S603, the image display range of the CRT 102 is read. In step S604, based on the calculated amount of change in table height and the read image display range, the coordinates of the coordinate axes in the scout image display area 701 of the CRT 102 are determined. The shift amount of the scout image is calculated. For example, if the fluctuation range of the table height is ± 100 mm with respect to the predetermined reference height and the image display range is ± 100 pixels, and if the table height fluctuates by 10 mm, the scout image is displayed in the scout image display area 701. Is shifted by 10 pixels with respect to the coordinate axis.
[0045]
In step S605, the image after the shift is displayed.
[0046]
FIG. 7B is a diagram illustrating a state in which the scout image after the scout image shift processing in step S505 is displayed on the scan plan screen 700 displayed on the CRT 102. Since the scout image displayed in the display area 701 has been shifted by the amount corresponding to the height change of the table, there is no problem even if a scan plan (702 to 704, etc.) is made based on the image, and thus the scout image is re-established. There is no need to perform a scan.
[0047]
Most of the control of the X-ray CT system in the embodiment was performed on the operation console 100. Since the configuration itself of the operation console 100 can be realized by a general-purpose information processing device (a workstation, a personal computer, or the like), it is also possible to install software in the device and realize the configuration.
[0048]
That is, an object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and a computer (or a CPU or a CPU) of the system or the apparatus. (MPU) reads out and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. This also includes a case where some or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
[0049]
When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.
[0050]
As a storage medium for storing such a program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM, or the like can be used. Further, it may be downloaded via a medium such as a network (for example, the Internet).
[0051]
As is apparent from the above description, according to the present embodiment, even if the table height changes after the scout scan is performed, the scout image is shifted by the change in the table height to restart the scout scan. A scan plan can be created without having to perform it.
[0052]
【The invention's effect】
As described above, according to the present invention, even when a change in table height occurs after a scout scan is performed, a scan plan can be made without performing the scout scan again.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an X-ray CT apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a flow of an overall process of the X-ray CT apparatus according to the embodiment of the present invention.
FIG. 3 is a diagram showing a scout scan setting screen in the X-ray CT apparatus according to the embodiment of the present invention.
FIG. 4 is a diagram showing a flow of a scout image display process in the X-ray CT apparatus according to the embodiment of the present invention.
FIG. 5 is a diagram showing a flow of a scan plan input process (limited to a gantry tilt angle) in the X-ray CT apparatus according to the embodiment of the present invention.
FIG. 6 is a diagram showing a flow of a scout image shift process in the X-ray CT apparatus according to the embodiment of the present invention.
FIG. 7A is a diagram showing a scan planning screen in the X-ray CT apparatus according to the embodiment of the present invention, showing a state where a scout image before a table elevating operation is displayed.
FIG. 7B is a diagram showing a scan planning screen in the X-ray CT apparatus according to the embodiment of the present invention, showing a state in which a scout image after the table elevating operation is displayed.

Claims (8)

An X-ray CT apparatus configured to irradiate an X-ray generated from an X-ray tube onto an object placed on a table to generate an X-ray image of the object,
Reading means for reading information about the height of the table,
Display means for displaying the generated X-ray image on predetermined coordinates based on information on the height of the table,
The display means,
When the predetermined table height at the time of generation of the X-ray image changes after the generation of the X-ray image, the displayed X-ray image is moved relative to the predetermined coordinates based on the variation of the table height. An X-ray CT apparatus characterized in that the X-ray CT apparatus is moved. The X-ray image is a fluoroscopic image generated by irradiating the subject placed and transported on the table with X-rays with the X-ray tube fixed at a predetermined position. The X-ray CT apparatus according to claim 1. Further comprising a detecting means for detecting the table height,
2. The X-ray CT apparatus according to claim 1, wherein the reading unit reads the table height detected by the detecting unit. An image processing method in an X-ray CT apparatus that generates an X-ray image related to a subject by irradiating the subject mounted on a table with X-rays generated from an X-ray tube,
A reading step of reading information on the height of the table,
A display step of displaying the generated X-ray image on predetermined coordinates based on information on the height of the table,
The display step includes:
When the predetermined table height at the time of generation of the X-ray image changes after the generation of the X-ray image, the displayed X-ray image is moved relative to the predetermined coordinates based on the variation of the table height. An image processing method in an X-ray CT apparatus, characterized in that the image processing method is performed. The X-ray image is a fluoroscopic image generated by irradiating the subject placed and transported on the table with X-rays with the X-ray tube fixed at a predetermined position. The image processing method in the X-ray CT apparatus according to claim 4. Further comprising a detection step of detecting the table height,
5. The image processing method according to claim 4, wherein the reading step reads the table height detected in the detecting step. A control program for causing a computer to implement the image processing method according to any one of claims 4 to 6. A storage medium storing a control program for causing a computer to realize the image processing method according to claim 4.

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