JP2006167346A - X-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus for taking a scanogram obtained by irradiating only a range irreducibly minimum for scanning plan with X-rays by realizing a photographic planning of different scanograms utilizing a scanogram photographed already. <P>SOLUTION: The X-ray CT apparatus provided with an X-ray generation source, an X-ray detection part arranged opposing this, a rotary disk which can be rotated with the X-ray generation source and the X-ray detection part arranged around a subject, an image processor for processing X-ray transmission data detected by the X-ray detection part, and a table which mounts the subject and sends the subject to a middle part between the X-ray generation source and the X-ray detection part is provided with a first fluoroscopic image acquirement instruction means which sends the table with the rotary disk fixed to a first rotation angle and instructs acquirement of a first fluoroscopic image along the direction of the body axis of the patient; and a second fluoroscopic image acquirement instruction means which sends the table with the rotary disk fixed to a second rotation angle and instructs a range of acquirement of a second fluoroscopic image along the direction of the body axis of the subject on the first fluoroscopic image. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for planning irradiation of X-rays according to fluoroscopic image data to be acquired based on past fluoroscopic image data in an X-ray CT apparatus that obtains a diagnostic image of a subject by irradiating X-rays.

In the X-ray CT apparatus, when an X-ray image is detected by irradiating an X-ray from around the subject and detecting the X-ray image transmitted through the subject (hereinafter referred to as a scan), the internal position of the subject is determined in advance. Generally, a fluoroscopic image whose shape can be confirmed is photographed, and the photographing range of the scan is determined while viewing the fluoroscopic image. Such a fluoroscopic image is commonly called a scanogram image.
Also, determining the scanning imaging range while viewing this scanogram image is called a scan plan.

The scanogram image is a fluoroscopic image obtained by fixing the position of the X-ray generation source and moving the subject transport table while irradiating X-rays by a distance in the necessary body axis direction.
Therefore, if a scanogram image is taken at the top of the X-ray generation source, a transmission image that extends in the table moving direction (Z-axis direction) of the subject is obtained.

One scanogram image is an image viewed from one direction of the subject. When more accurate positioning is desired, the position of the X-ray generation source is changed to obtain a fluoroscopic image from another angle.
A scan plan is made based on the plurality of scanogram images.
Specifically, as described in Patent Document 1, the X-ray generation source is fixed in the vertical direction of the subject (the position of the X-ray generation source is 0 ° or 180 ° when the 12 o'clock position is 0 °). And the scanogram obtained by fixing the X-ray source in the left-right direction of the subject (the X-ray source is 90 ° or 270 °), respectively, Position the direction.
Japanese Patent Laid-Open No. 11-104121

A scanogram image is not an image that can be directly used for diagnosis of a subject.
For this reason, it is desirable if it can be omitted from the viewpoint of exposure to X-rays.
However, on the other hand, scanogram imaging for more accurately determining the scan position is indirectly important in obtaining a diagnostic image of the subject reliably.
Therefore, as a compromise between these, an object was to obtain a method capable of more accurate scanning positioning with less exposure.

  That is, the present invention makes it possible to plan imaging of different scanogram images using already captured scanogram images, and to obtain a fluoroscopic image (scanogram image) irradiated with X-rays only in the minimum necessary range for scanning planning. An object is to provide an X-ray CT apparatus that can be obtained.

  In order to achieve the above object, an X-ray CT apparatus of the present invention includes an X-ray generation source, an X-ray detection unit disposed opposite to the X-ray generation source, the X-ray generation source and the X-ray around a subject. A rotating disk that can be rotated by arranging a line detector, an image processing device that images X-ray transmission data detected by the X-ray detector, an X-ray generation source and the X A table for sending the subject to the middle of the line detection unit, and sending the table while instructing the acquisition of the first fluoroscopic image along the body axis direction of the subject while the rotary disk is fixed at the first rotation angle The first fluoroscopic image acquisition instruction means, and a range in which the second fluoroscopic image is acquired along the body axis direction of the subject by sending out the table while being fixed at the second rotation angle. And second perspective image acquisition instructing means for instructing on the image.

Further, a range in which the second fluoroscopic image is acquired is narrower than a range in which the first fluoroscopic image is acquired.
Further, the X-ray generation source is provided with X-ray shielding means for blocking irradiation of X-rays in the direction of the X-ray detection unit, and the range obtained from the first perspective image and the second perspective X-rays are shielded by the X-ray shielding means in ranges where images are acquired in different ranges.
In addition, a data table that allows a range for acquiring the second fluoroscopic image to be set relative to the range for acquiring the first fluoroscopic image is read, and fluoroscopic image shooting is controlled by reading the data table. The control means is provided.

  According to the present invention, an X-ray image can be obtained by making it possible to plan different scanogram images using a scanogram image that has already been shot, and to irradiate X-rays only in the minimum range necessary for scan planning. A line CT device can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing an embodiment of an X-ray CT apparatus according to the present invention.
As shown in the figure, the X-ray CT apparatus described in the present embodiment is used to set various conditions for imaging a subject or to instruct to reconstruct an image based on acquired data. Designated by the console 100 and the gantry device 200 for irradiating the subject with X-rays according to the imaging conditions inputted from the console 100 and detecting the X-rays transmitted through the subject and collecting data. And a table 300 that conveys a subject for imaging a range.

  The console 100 includes a graphical user interface for setting shooting conditions and image observation, a computer including CPU1, RAM2, and HD3 for operating an application for controlling the gantry 200 and the table 300, and a gantry 200. An image processing unit 4 that reconstructs an image based on data transmitted from the computer, a CRT 5 for displaying the reconstructed image, and a keyboard 6 and a mouse that serve as input devices for setting various conditions and observing the image. 7

The gantry 200 is connected to the console 100 via the I / F 8a.
The gantry 200 includes a main controller 9 that controls various control mechanisms of the gantry 200 and the table 300, an X-ray generation source 10, an X-ray controller 11 that controls the X-ray generation source 10, and a shield for blocking X-rays. An X-ray shielding mechanism unit 12, an X-ray shielding controller 13 for controlling the X-ray shielding mechanism unit 12, and an X-ray detection unit 14 for detecting X-rays irradiated from the X-ray generation source 11 and transmitted through the subject, The data acquisition unit 15 converts the X-rays detected by the X-ray detection unit 14 into data.

Among these, the data collection unit is connected to the console 100 via the I / F 8b, and the collected data is transmitted to the console 100. The X-ray generation source 11 and the X-ray detection unit 14 are mounted on a rotating disk and can be imaged while rotating around the subject.
The table 300 includes a top plate 16 for carrying the subject and a table controller 17 that controls the movement of the top plate 16 in response to a command from the main controller 9.

Next, the operation flow in the present invention will be described with reference to FIG.
Here, FIG. 2 shows an example in which scanogram A and scanogram B are photographed for scan planning before scanning.
It is also possible to take a scanogram C, scanogram D, etc. as necessary. In each scanogram plan, it is possible to use a scanogram taken before that.

In FIG. 2, in step S401, first, a tube voltage, a tube current, an imaging range, a fluoroscopic image angle (X-ray generation source position), and the like are set in order to obtain an initial scanogram image.
Here, as the first scanogram image, scanogram A imaging conditions (tube voltage, tube current, imaging range, fluoroscopic image angle (X-ray generation source position), etc.) are set.
In step S402, the scanogram is photographed according to the photographing conditions.
In step S403, the scanogram A image is displayed on the CRT 5 that is the image display device shown in FIG.

Next, on the basis of the scanogram image displayed above, the position and range to be obtained as the perspective images at different angles are designated, and photographing is started.
That is, in step S404, a range in which a fluoroscopic image is desired to be acquired by scanogram B while viewing this scanogram A image, that is, a range in which X-rays are irradiated to the subject is set.
For example, assuming that the X-ray generation source is at 12 o'clock (this position is referred to as PA), a scanogram A image is acquired at this position.
Then, based on the scanogram A image, it is conceivable that the X-ray generation source is at the 3 o'clock position (this position is referred to as LAT), and the scanogram B image is acquired at this position.

In the case of a subject whose side width is larger than the front due to obesity, for example, confirm not only the PA but also the LAT, the field of view and the region of interest (hereinafter abbreviated as ROI) at the time of tomography This is because it is necessary to decide.
This is because if the field of view and the region of interest at the time of tomographic imaging are not taken into consideration, the necessary area cannot be captured and the image is captured again, or the image quality cannot be optimized and the problem of re-imaging arises.
In addition, when ROI is in the vicinity of bone, it is necessary to select a process that corrects beam hardening. However, it is difficult to make a decision with a scanogram only for PA, and some information on LAT is desired.

In addition, if you want to take a tomographic image of a minute part where sufficient image quality could not be obtained with the previous scanogram, obtain the scanogram again with the same X-ray source angle as the previous one only to determine the position of the tomographic image. Sometimes used. As can be seen from these examples, there is a need to rescan scanograms from the same X-ray source angle or from different angles.
Thus, in step S404, the imaging position of the scanogram B to be added to the minimum necessary is determined.

Next, in step S405, the scanning conditions (tube voltage, tube current, imaging range, fluoroscopic image angle (X-ray generation source position), etc.) of the scanogram B are set in accordance with the purpose of acquiring the scanogram B.
In step S406, the scanogram B is photographed.
During imaging, the subject transport table continues to move at a predetermined speed.
Here, the X-ray irradiation range to the subject set in step S404 is transmitted to the main controller 9 through the I / F 8a of FIG.

The main controller 9 in FIG. 1 transmits a command to the X-ray shielding controller 13, and the X-ray shielding controller 13 controls the X-ray shielding mechanism unit 12 in FIG. 1, and then a scanogram image B is obtained in step S406.
Data obtained from the detection unit is captured by the data collection unit, and a scanogram image is created by the image calculation unit. Here, the X-ray shielded part does not display the noise information as it is, but the data below a certain output is processed and saved as a scanogram image by filling it with a fixed value below the minimum CT value. Display on the display. If necessary, a scanogram from a different angle can be planned and photographed. Scan planning is performed based on the plurality of scanogram images obtained here.

While scanning scanogram B, the X-ray source continues to emit X-rays.
For this reason, X-rays are prevented from being irradiated to the subject in parts that are not necessary as fluoroscopic images. That is, the X-ray shielding mechanism is operated so as to shield X-rays from unnecessary parts.

In step S407, this scanogram B image is displayed on the CRT 5 of FIG. 1 in the same manner as the scanogram A image.
In step S408, referring to the scanogram A image and scanogram B image displayed on the CRT 5 in FIG. 1, a scan plan such as setting of ROI is performed.
In step S409, scan conditions are set.
In step S410, a scan is executed.
In step S411, the scanned image is displayed on CRT 5 in FIG.

  Next, the scanogram B image planning method using the scanogram A image in step S404 and the scan planning method using the scanogram A image and B image in step S408 will be described with reference to FIG.

In FIG. 3, reference numerals 501, 503, and 505 indicate scanogram A images. Reference numerals 502, 504, and 506 denote scanogram B images. Reference numeral 507 indicates a range in which X-rays are irradiated on the scanogram A image in order to obtain a scanogram B image. Reference numeral 508 indicates a scan plan line on the scanograms A and B. Reference numerals 501 to 508 are displayed on the CRT 5 in FIG.
In FIG. 3, a screen 501 is a state where the scanogram A image of step S403 is displayed on the CRT 5 of FIG. At this stage, the scanogram B image is not displayed on the screen 502.

In step S404, a scanogram B is planned using this scanogram A image, as shown at 503 in FIG.
Although the scanogram image is not displayed on the screen 504, the X-ray irradiation range of the scanogram B is determined on the scanogram A image on the screen 503.
In step S408, a scan plan is performed using the scanogram A image on the screen 505 and the scanogram B image on the screen 506.

Here, scroll bars are provided on the screens 501 and 502.
This is for scrolling a scanogram image when a plurality of scanograms are photographed so that the plurality of scanogram images can be used for scanogram planning and scan planning.

As described above, in Example 1, the scanning plan of the scanogram image is described from the viewpoint of minimizing the exposure.
Furthermore, in actual clinical practice, it is also important to save as much work as possible.
One solution is protocolization.

FIG. 4 shows a scanogram protocol created for the scanogram imaging of FIG.
This scanogram protocol, for example, automatically captures a predetermined scanogram B image after capturing a scanogram A image.

The protocol as shown in FIG. 4 is recorded as data in the HD3 or RAM 2 of FIG. When scanogram A is started, CPU1 automatically acquires scanogram B accordingly.
When it is necessary to regularly acquire scanogram B after scanogram A, it is possible to employ such a standard protocol processing, and it is possible to reduce the operation time.
As shown in FIG. 4, the protocol is specified by the position of the X-ray tube and the detector (PA, LAT), tube voltage (kV), tube current (mA), scanogram length (Length), and the like.

  An example in which the scanogram length (table feed amount) of scanogram B is automatically set to be the same length as scanogram A is shown. The parameter of the X-ray irradiation unit of the scanogram image is called Expose.

The X-ray irradiation unit parameter Expose will be described in detail.
For example, in FIG. 4, the table 601 that is the contents of the parameter Expose of the X-ray irradiation unit sets X-ray irradiation OFF / ON for up to seven areas so that X-ray irradiation can be performed for three discontinuous areas. It is set.
That is, Area1 is an area that is 30% or more and less than 40% in the scanogram length from the start position of the scanogram. In the table 601, the X-ray irradiation of this area is designated as OFF. Area 2 is an area where the scanogram length is 40% or more and less than 50% from the start position of the scanogram, and X-ray irradiation is designated as ON. The table 601 includes a column 602 indicating the ID of the area, a column 603 indicating the position from the start position of the scanogram, and a column 604 indicating whether or not to perform X-ray irradiation.

The column 603 indicating the position from the start position of the scanogram can be specified by a ratio (%) from the scanogram start position so that it can be expressed without depending on the substantial length of the scanogram length. Yes.
By using such a scanogram protocol, by designating the area where X-ray irradiation is expected to be necessary in advance in the scanogram B image, the planning time for the scanogram B image of S404 in FIG. 2 can be shortened. Is possible.
If necessary, the X-ray irradiation area of the scanogram B image can be adjusted by the scanogram planning line on the scanogram A image.

Referring to FIG. 5, the range of scanogram B taken by the protocol of FIG. 4 is shown.
In FIG. 5, 701 indicates the scanogram start position, 702 indicates the scanogram end position, and 703 indicates the X-ray irradiation range of scanogram B. In the table 601 of FIG. 4, X-ray irradiation is ON in Area2, Area4, and Area6, and OFF in other Areas.

  In FIG. 5, it can be seen that X-ray irradiation is performed in Area 2 of 30% to 40% of the scanogram length, Area 4 of 50% to 60% of the scanogram length, and Area 6 of 70% to 80% of the scanogram length. . In this way, if the range in which X-ray irradiation is performed and the scanogram B is acquired is defined using the protocol, the scanogram B can be set easily and reliably.

1 is a configuration diagram of an X-ray CT apparatus according to Embodiment 1 of the present invention. The figure which shows the flow of operation by Example 1 of this invention. FIG. 5 is a diagram showing a scanogram plan and a scan plan using a scanogram image according to the first embodiment of the present invention. FIG. 6 is a diagram showing a scanogram protocol according to Embodiment 2 of the present invention. FIG. 6 is an image diagram showing a photographing area by a scanogram protocol according to the second embodiment of the present invention.

Explanation of symbols

  1 CPU, 2 RAM, 3 HD, 4 Image processor, 5 CRT, 6 Keyboard, 7 Mouse, 8a, 8b I / F, 9 Main controller, 10 X-ray source, 11 X-ray controller, 12 X-ray shielding mechanism Unit, 13 X-ray shielding controller, 14 X-ray detection unit, 15 data collection unit, 16 top panel, 17 table controller, 100 console, 200 gantry, 300 table

Claims (4)

An X-ray source;
An X-ray detection unit arranged opposite to this,
A turntable capable of rotating by arranging the X-ray generation source and the X-ray detection unit around a subject;
An image processing device for imaging X-ray transmission data detected by the X-ray detection unit;
A table on which the subject is mounted and the subject is sent out between the X-ray generation source and the X-ray detection unit;
In an X-ray CT apparatus equipped with
First fluoroscopic image acquisition instructing means for sending out the table and instructing acquisition of the first fluoroscopic image along the body axis direction of the subject while fixing the rotating disk at the first rotation angle;
The second fluoroscopic image acquisition instructing, on the first fluoroscopic image, a range in which the second fluoroscopic image is acquired along the body axis direction of the subject while the table is sent out while being fixed at the second rotation angle. And an X-ray CT apparatus.   The X-ray CT apparatus according to claim 1, wherein a range in which the second fluoroscopic image is acquired is narrower than a range in which the first fluoroscopic image is acquired. The X-ray generation source is equipped with X-ray shielding means for blocking irradiation of X-rays toward the X-ray detection unit,
3. The X-ray according to claim 2, wherein X-rays are shielded by the X-ray shielding means in a range where a range in which the first fluoroscopic image is acquired and a range in which the second fluoroscopic image is acquired are different. Line CT device. A data table that allows setting the range for acquiring the second perspective image relative to the range for acquiring the first perspective image;
The X-ray CT apparatus according to claim 1, further comprising a control unit that reads the data table and controls fluoroscopic imaging.

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