JP2000023971A - X-ray ct scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce burden of an operator by automation for setting a scan condition by providing a control means performing controls to determine an X-ray exposure condition according to a photographing location based on a set photographing location and X-ray data and to execute a CT photographing on the X-ray exposure condition according to the determined photographing location. SOLUTION: When a scan image on a display part 10 is observed and a slice location is set via a keyboard, the setting information is stored in a slice location storage means 9c. In a scan condition determination means 9d, an optimum tube current value for each slice in a slice image photographing to be subsequently executed is determined based on scan image projection data and the determination information is transmitted to a scan control means 9e. Then, the execution of the slice image photographing is controlled by a scan control means 9e. Namely, an X-ray tube and an X-ray detector are revolved with a body shaft of a testee body as a center for every slice location, X-ray is exposed from the X-ray tube for every fine revolution and the collection of X-ray projection data is performed by a data collecting part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an X-ray CT scanner capable of scanning a subject with a scanogram and CT.

[0002]

2. Description of the Related Art Conventionally, in an X-ray CT scanner,
2. Description of the Related Art Obtaining tomographic images (slice images) of a plurality of slice planes that are continuous in the body axis direction of a subject and are parallel to each other is performed. In such an X-ray CT scanner, a scano image of a subject is taken in advance in order to determine a slice position. That is, the X-ray tube and the X-ray detector in the X-ray CT scanner are fixed at a fixed position, and the couchtop on which the subject is placed is moved between the X-ray tube and the X-ray detector. Then, X-rays are emitted toward the subject in synchronization with the movement of the couch top, and a scano image 14 substantially similar to a general X-ray fluoroscopic image is obtained, for example, as shown in FIG. A scano image 1 is displayed on the CRT display of the X-ray CT scanner.
4 and a plurality of lines 15 indicating positions at which slice images can be taken (slice positions) are displayed in a superimposed manner.
When the number associated with the corresponding line 15 on the T display is input to the X-ray CT scanner via the keyboard, the couch top moves so that the slice image capturing region of the subject is located immediately below the X-ray tube. Then, a slice image is taken by rotational scanning of the X-ray tube (this is called "auto index scan").

In such an X-ray CT scanner, an X-ray tube current (hereinafter, referred to as a “tube current”) at the time of capturing a slice image is operated by a switch or the like provided on an operation panel.
) Can be set. This is to secure the optimum X-ray dose for the imaging site by adjusting the tube current value. In addition, some X-ray CT scanners can change (shift) their positions on a line connecting the X-ray tube and the center of the X-ray detector, and this shift position also depends on the size of the subject. It can be set in advance depending on the situation.

[0004]

However, in the conventional X-ray CT scanner, so-called scan condition settings such as the tube current value setting and the shift position setting are performed based on the operator's experience. For an operator who is not abundant, setting of scan conditions is performed by trial and error, and it is difficult to set optimum conditions. Further, it is not always easy for an experienced operator to set the optimum scan conditions for each slice, and the operator has a heavy burden when setting the scan conditions.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an X-ray CT scanner which reduces the burden on the operator by automating the setting of scanning conditions.

[0006]

In order to achieve the above object, the present invention provides an X-ray CT scanner for performing a CT scan after performing a scano image scan, and setting means for setting the scan position for the CT scan. Collection means for collecting X-ray data obtained by the scano imaging, based on the imaging position and the X-ray data set by the setting means,
An irradiation condition determining unit for determining an X-ray irradiation condition corresponding to the imaging position; and a control for executing the CT imaging under the X-ray irradiation condition corresponding to the imaging position determined by the irradiation condition determining unit. And control means for performing the control.

According to the present invention, a CT scan is performed after a scano image of a subject is shot. The X-ray irradiation condition corresponding to the imaging position is determined based on the information of the set imaging position and the X-ray data obtained by the scano imaging. Based on this determination, the control unit executes CT imaging under X-ray irradiation conditions corresponding to the imaging position.

[0008] As described above, the X-ray exposure conditions are automatically set, and the optimum X-ray irradiation condition is set regardless of the operator's experience.
Since the line exposure conditions can be set, the burden on the operator can be greatly reduced.

Further, since CT imaging in which the X-ray irradiation conditions are changed according to the imaging position can be performed, for example, the X-ray dose is increased for a thick portion (imaging position) while it is increased for a thin portion. Can reduce the X-ray dose and acquire a CT image. As a result, a high-quality image can be obtained, and unnecessary exposure to the subject can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an X-ray tube, 2
Reference numeral 4 denotes a couch top on which the subject 3 is placed, and 4 denotes an X-ray detector for detecting transmitted X-rays. The X-ray tube 1 and the X-ray detector 4 are mounted on a gantry (not shown) so as to face each other with the couch top 2 therebetween, and are supported rotatably about the body axis of the subject 3. Reference numeral 5 denotes a data collection unit which collects output data of the X-ray detector 4 which detects the amount of transmitted X-ray transmitted through the subject 3 by X-ray irradiation, converts the output data into digital values, and outputs the digital values. It is.

Reference numeral 6 denotes an X-ray tube control unit which supplies a high voltage to the X-ray tube 1 and controls X-rays at a timing controlled by a system control unit 8 described below in accordance with a command from a central control unit 9 described later. The X-ray tube 1 is operated, and a signal indicating that X-rays are emitted by the operation of the X-ray tube 1 is returned to the system control unit 8. Reference numeral 7 denotes a mechanism control unit which drives a gantry (not shown) and horizontally moves the couch top 2 while the gantry is stopped, and particularly counts the amount of movement of the couch top 2 from its initial position and counts it. It is configured to output a value. The system control unit 8 is configured to control the operation timing of each unit of the X-ray CT scanner. The central control unit 9 is configured to include at least the following units.

That is, as shown in FIG. 2, an X-ray obtained by exposing an X-ray while rotating an X-ray tube 1 around a subject 2 is obtained.
Slice image reconstructing means 9a for reconstructing a slice image based on the line projection data by, for example, a composition method or the like.
While the X-ray tube 1 and the X-ray detector 4 disposed opposite to the X-ray tube 1 are fixed to a gantry (not shown), the bed top 2 is moved in the body axis direction of the subject 3 (a direction orthogonal to the paper surface). ,
A scano image forming means 9b for forming a scano image based on transmission data of X-rays emitted in synchronization with this movement, a slice position storage means 9c for storing slice position information set on the scano image, Scan condition deciding means 9d for deciding scan conditions in slice image photographing based on scano image photographing data, and scan control means 9e for controlling execution of slice image photographing based on the determined output.
The central control unit 9 includes: a slice image created by the slice image reconstruction unit 9a; and an image processing unit 9f that performs appropriate image processing by taking in the slice image.

In FIG. 1, reference numeral 10 denotes a display unit having a CRT display for displaying images, and 11 denotes an input unit having a keyboard and a tracker ball. Here, as the above-mentioned scan condition setting, there is a tube current value setting for securing an optimum X-ray dose for each slice. The amount of X-ray attenuation in the subject 3 in the X-ray irradiation direction (that is, the scanning image capturing direction) can be grasped from the scanning image capturing data. Further, the amount of X-ray attenuation in the subject 3 in the fan direction (the direction of the arrow 12) can be estimated from the average value of the scano image photographing data for all channels of the X-ray detector. If the amount of X-ray attenuation in the subject 3 is known, the optimal X-ray dose is determined for each slice position in slice image photographing, and the tube current is determined from this.

Next, the operation of the above configuration will be described. First, the subject 3 on the couch is located in front of the imaging hole of the gantry (not shown).
(Normally, the head of the subject 3 is arranged with the head facing the imaging hole). Next, the couch top 2 on which the subject 3 is placed is sent out from the base of the couch. For example, when the couch top 2 is inserted by a predetermined length into the imaging hole, the arrangement control between the couch top 2 and the X-ray tube 1 at that time is set to an initial state, and the mechanism control 7 drives the couch top 2, for example. The number of pulse rotations of the pulse motor is counted, and the counted value is output to the scano image forming means 9b in the central control unit 9 via the system control unit 8.

On the other hand, the X-ray tube controller 6 controls the X-ray tube 1 so as to emit X-rays at predetermined slice intervals in synchronization with the movement of the couchtop 2 driven by the mechanism controller 7. At the same time as the operation, a signal indicating the X-ray exposure is output to the scano image forming means 9b in the central control unit 9 via the system control unit 8. X-rays emitted from the X-ray tube 1 and transmitted through the subject 3 are detected by the X-ray detector 4, and the X-ray projection data collected by the data collection unit 5 is scanned by a scano image forming unit in the central control unit 9. 9b. The scano image forming means 9b forms a scano image based on the X-ray projection data,
To send to. As a result, a scano image of the subject is obtained.

The operator observes the scano image on the display unit 10 and sets a slice position via a keyboard (not shown). The slice position setting information is stored in the slice position storage means 9c.

On the other hand, in the scan condition determining means 9d, based on the scanogram image projection data (X-ray projection data), each slice (slice position information is set first by an operator in slice image photographing executed later). Is determined, and the determined information is sent to the scan control means 9e. Then, the execution of the slice image photographing is controlled by the scan control means 9e.
That is, for each slice position, the X-ray tube 1 and the X-ray detector 4 rotate around the body axis of the subject 3, and X-rays are emitted from the X-ray tube 1 for each minute rotation, and the data The collection unit 5 collects X-ray projection data (projection data). Here, the tube current value for each slice is adjusted to an optimum value for each slice by the scan control means 9e via the X-ray tube control unit 6. The acquired X-ray projection data is taken into a slice image reconstruction means 9a, where a slice image is formed. The formed slice image is displayed on the display unit 10.
Is displayed with. If necessary, the image processing means 9f
, A cross-section conversion process and a three-dimensional image process are performed, and the processed image is displayed on the display unit 10.

As described above, in the present embodiment, the scan conditions in the slice image photographing, particularly, the tube current value are automatically set to the optimum values without the intervention of the operator.
Regardless of the operator's experience in setting scan conditions, the optimum scan conditions (tube current value in this case) can be set for each slice, so that the burden on the operator can be greatly reduced and good diagnostic interpretation is achieved. A good slice image can be obtained. Further, it is possible to shorten the photographing time by eliminating the trial and error setting of the scan conditions.

In an X-ray CT scanner having a shift function, automatic setting of the shift position of the X-ray tube 1 and the X-ray detector 4 is performed in addition to the automatic setting of the tube current value. Good. In this case, if the scanogram imaging is performed from the direction in which the maximum outer shape of the subject 3 is understood, for example, from the lateral direction of the subject 3, a scano image as indicated by 14 in FIG.
From this, the maximum outer shape of the subject (in this case, the thickness of the subject 3)
You can figure out. Specifically, the maximum outer shape can be obtained by examining the X-ray detector channel that takes a value equal to or greater than the threshold value using the X-ray detector output in the case of scanning the air as a threshold value (see FIG. 4). If the maximum outer shape of the subject 3 is known, the shift position of the X-ray tube 1 and X-ray detector 4 for each slice can be determined. This shift position is determined by the scan condition determining means 9d. When the shift position is determined, the scan control means 9e adjusts the shift position of the X-ray tube 1 and X-ray detector 4 to the optimum position for each slice via the mechanism control unit 7.

In an X-ray CT scanner having a shift function, it is desirable to automatically set the tube current value and the shift position of the X-ray tube 1 and X-ray detector 4 automatically. Even if only one of them is performed, the burden on the operator is reduced by that much.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
It goes without saying that various modifications can be made. In the above embodiment, the tube current value is given as the scan condition.
It is also conceivable that the scan condition includes a tube voltage value. Automatic setting of scan conditions including the tube voltage value is also possible.

[0022]

As described above in detail, according to the present invention, X
The burden on the operator involved in setting the line exposure conditions can be greatly reduced. In addition, a high-quality image can be obtained, and unnecessary exposure of the subject can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an X-ray CT scanner according to the present invention.

FIG. 2 is a detailed configuration block diagram of a central control unit in FIG. 1;

FIG. 3 is an explanatory diagram showing a relationship between a scano image and a slice position.

FIG. 4 is a characteristic diagram for explaining how to grasp the maximum outer shape of a subject.

[Explanation of symbols]

 Reference Signs List 1 X-ray tube 3 Subject 4 X-ray detector 9 Central control unit 9d Scan condition determination means 9e Scan control means

Claims (2)

[Claims] 1. An X-ray CT scanner for performing a CT scan after performing a scano image scan, a setting unit for setting a scan position for the CT scan, and an acquisition unit for collecting X-ray data obtained by the scano scan. Means; an exposure condition determining means for determining an X-ray emission condition corresponding to the imaging position based on the imaging position set by the setting means and the X-ray data; An X-ray CT scanner, comprising: a control unit that performs control to execute the CT imaging under X-ray irradiation conditions corresponding to the selected imaging position. 2. The apparatus according to claim 1, wherein the control unit changes the X-ray exposure condition for each of the imaging positions and executes the CT imaging based on an output of the exposure condition determining unit. Item 7. An X-ray CT scanner according to Item 1.