JP3627422B2 - X-ray CT system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray CT apparatus, and more particularly to a continuous rotation X-ray CT apparatus capable of collecting data in a spiral shape.
[0002]
[Prior art]
The continuous rotation type X-ray CT system rotates the X-ray tube and X-ray detector housed in the gantry continuously in one direction by ensuring electrical connection during rotation by means of a slip ring or the like. The X-ray beam irradiation direction can be continuously rotated around the subject. Therefore, in this X-ray CT apparatus, if the X-ray tube and the X-ray detector are rotated by one rotation and the X-ray beam is scanned in plane rotation with respect to a specific slice surface, data acquisition is performed. An X-ray tube and an X-ray detector are continuously rotated in one direction, and the subject is inserted into a plane in which the X-ray beam is continuously rotated. When moved, the subject is scanned spirally with the X-ray beam, and X-ray absorption data by the X-ray beam scanned spirally can be collected. A tomographic image at a cross section at any position can be reconstructed continuously.
[0003]
When imaging a subject into which a contrast medium has been injected using such a continuous rotation X-ray CT apparatus, the following procedure is usually taken. First, before injecting contrast medium, plane rotation scans are sequentially performed on different slice planes to obtain tomographic images, which are sequentially displayed, and when it is confirmed that the desired part can be covered, the contrast medium is injected, and the same A spiral scan is performed in the area, or a plane rotation scan is performed on the same plurality of slice planes as before injection.
[0004]
As described above, when the same region is repeatedly imaged before and after the injection of the contrast medium, it is conventionally necessary to set the condition again so that the condition is the same as the first condition at the time of the second imaging. There is.
[0005]
[Problems to be solved by the invention]
However, it is troublesome and time-consuming if the conditions for the second imaging are set again as in the prior art. In addition, it is time consuming to perform plane rotation scanning on the same plurality of slice planes as in the first imaging. In the first imaging, it is meaningful to perform a plane rotation scan for each slice plane in that a necessary imaging range is searched without subjecting the subject (patient) to unnecessary X-ray exposure. Such a meaning cannot be found by imaging.
[0006]
In view of the above, the present invention is an X-ray CT apparatus that is improved so that the second and subsequent imaging can be performed by continuous helical rotation scanning without taking time and effort when imaging the same region repeatedly. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the X-ray CT apparatus according to the present invention, the means for irradiating the subject with the X-ray beam and the irradiation direction of the X-ray beam are continuously rotated around the subject. Means, means for relatively moving the subject in a direction substantially perpendicular to the plane of rotation of the X-ray beam, means for collecting data by detecting the X-ray beam transmitted through the subject, and a plurality of subjects Characterized in that it comprises means for storing plane rotation scan conditions performed on different slice planes, and means for converting the plane rotation scan conditions into conditions for continuous helical rotation scans.
[0008]
When the plane rotation scan is performed on each of a plurality of different slice planes of the subject in the first imaging, the imaging conditions are stored, and the conditions are converted into the imaging conditions of the continuous spiral rotation scan. Therefore, the same region as the first imaging can be scanned in a continuous spiral rotation immediately without the trouble of setting the conditions again. Since the second and subsequent imaging can be performed by continuous spiral rotation scanning in this way, the imaging time can be shortened.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a continuous rotation type X-ray CT apparatus according to the present invention. In this figure, an X-ray tube 12 and an X-ray detector 13 are opposed to a gantry 11. The X-ray tube 12 and the X-ray detector 13 are rotated by a rotating device 14 in a plane perpendicular to the paper surface. A subject 20 lying on the table 22 of the bed 21 is inserted into a space between the X-ray tube 12 and the X-ray detector 13. The table 22 is moved linearly by a driving device (not shown) provided in the bed 21.
[0010]
The gantry 11 is controlled by a gantry controller 33 connected to the CPU 32, and X-ray exposure from the X-ray tube 12 and rotation of the rotating device 14 are controlled. The bed 21 is controlled by a bed controller 34, and the movement of the table 22 is controlled under the control of the CPU 32.
[0011]
The X-ray tube 12 and the X-ray detector 13 rotate in the XY plane, where Z is the left-right direction of the paper, Y is the vertical direction, and X is the direction perpendicular to the paper. During continuous spiral scanning, the subject 20 is continuously moved as indicated by arrows in the Z direction perpendicular to the XY plane while the X-ray tube 12 and the X-ray detector 13 are rotating. When viewed from the subject 20, the Y direction is the front-rear direction, the X direction is the left-right direction, and the Z direction is the body axis direction. In other words, the X-ray beam is rotationally scanned in the XY plane perpendicular to the body axis, and each angle direction related to X-ray absorption in the plane through which the X-ray beam passes from the X-ray detector 13. Projection data is obtained as detection data.
[0012]
This detected data is sent to the memory 31 via the data collecting device 15. The memory 31 also receives an angle signal from the rotating device 14 and a position signal of the table 22 (that is, the subject 20) from the bed 21, and the detection data is stored together with the angle signal and the position signal. The
[0013]
When the CPU 32 retrieves 360 ° (or 180 °) projection data for a certain position from the memory 31 and sends it to the image reconstruction device 35, the image reconstruction device 34 performs back projection processing or the like according to each angle. By doing so, the tomographic image in the plane of the position is reconstructed. The image data of the reconstructed image is sent to the image display circuit 36 via the CPU 32 and displayed on the display device 37.
[0014]
A mouse 39 is connected to the CPU 32 via a mouse controller 38 and a keyboard 42 is connected via a keyboard controller 41, so that setting of imaging conditions and the like are performed. The CPU 32 is connected to a condition memory 43 that stores imaging conditions, and a condition converter 44 that converts imaging conditions for plane rotation scanning into imaging conditions for continuous spiral rotation scanning.
[0015]
For example, when obtaining a CT image when a contrast medium is injected into the subject 20, first, before injecting the contrast medium, the table 22 is moved stepwise to be stationary, and the X-ray tube 12 is stationary at that time. And the X-ray detector 13 are rotated once, and a plane rotation scan is sequentially performed for each of the plurality of slice planes 23 as shown in FIG. At that time, by operating the mouse 39 and the keyboard 42 in advance, imaging conditions such as tube voltage, tube current, slice thickness, imaging position (position of each slice plane 23) are set for imaging before contrast medium injection. The
[0016]
When data is collected for each of the plurality of slice planes 23, the data is sequentially sent to the image reconstruction device 35, and the tomographic images for each slice plane 23 are sequentially reconstructed, and are displayed via the image display circuit 36. 37. In the display device 37, the tomographic images of the slice planes 23 that are successively scanned by plane rotation are displayed one after another. When the operator observes this image and determines that the image of the desired part has been obtained. Then, the imaging before the injection of the contrast agent is terminated. At this time, the imaging conditions such as the tube voltage, the tube current, and the slice thickness set as described above are stored in the condition memory 43.
[0017]
When the imaging before the injection of the contrast medium is thus completed, an operation window 51 as shown in FIG. 2 appears on the screen of the display device 37 (a program for automatically displaying such a display when imaging is completed is CPU 32. Built in). In accordance with the message “Do you want to rescan?”, One of the “Yes” and “No” buttons 52 and 53 is pressed (the cursor is clicked on these buttons 52 and 53 with the mouse 39). When the button 53 is pressed, the process is terminated, and when the button 52 is pressed, the window 51 is switched to the display as shown in FIG.
[0018]
When the “previous condition” button 54 is pressed in the operation window 51 of FIG. 3, the condition stored in the condition memory 43 is read, and imaging is performed under exactly the same conditions as the previous time. That is, plane rotation scanning is performed on the same plurality of slice planes 23 as before, and tomographic images are reconstructed. On the other hand, when the “Condition conversion” button 55 is pressed, the imaging condition of the plane rotation scan read from the condition memory 43 is converted into the imaging condition of the continuous spiral rotation scan by the condition conversion device 44 and is sent to the CPU 32. returned. Based on this, the CPU 32 controls the continuous helical rotation scan to be performed. In this case, the X-ray tube 12 and the X-ray detector 13 are continuously rotated by the rotating device 14, and X-rays are continuously emitted from the X-ray tube 12, and the table 22 is moved during the exposure. The subject 20 is moved within a predetermined range, and data by continuous spiral rotation scanning is collected. Therefore, the operator confirms the injection of the contrast medium into the subject 20 and then presses any one of these buttons 54 and 55 at an appropriate timing.
[0019]
Here, the condition conversion will be described. For example, in imaging before contrast medium injection, if the slice thickness of each slice plane 23 is 10 mm and the plane rotation scan is performed on 10 slice planes 23 at a pitch of 10 mm, continuous spiral is performed. The range 24 of the rotational scan is calculated as 90 mm and converted. In addition, in continuous spiral rotation scanning, since the X-ray tube 12 is exposed to a continuous load, the load on the X-ray tube 12 increases. It is desirable to display it so that the operator can confirm it). In this case, since the continuous helical rotation scan is performed in the range 24 of 90 mm, it is completed in a short time of about 10 seconds, and there is no difficulty in holding the breath of the subject 20 and a good quality image can be obtained. .
[0020]
In the above description, the condition memory 43 and the condition conversion device 44 have been described as being configured as dedicated hardware separate from the CPU 32. However, these use memory in the CPU 32 or software processing in the CPU 32. It can also be realized. Although the buttons 52 to 55 are displayed in the operation window 51 appearing on the screen of the display device 37, this type of button is not provided in such a display screen but actually provided on the operation panel. The switch can also be configured to be operated by hardware. In addition, the specific configuration and the like can be variously changed without departing from the gist of the present invention.
[0021]
【The invention's effect】
As described above, according to the continuous rotation type X-ray CT apparatus of the present invention, when the same region of the subject is repeatedly imaged, such as before and after the injection of the contrast agent, the second time without taking time and effort. Subsequent imaging can be performed quickly by continuous spiral scanning. For this reason, the operator is released from troublesome condition setting operations for the second and subsequent imaging, and the imaging can be completed in a short time by continuous helical rotation scanning. The burden can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a diagram showing an operation window appearing on a display screen.
FIG. 3 is a diagram showing an operation window that appears on the display screen in the next stage.
[Explanation of symbols]
11 Gantry 12 X-ray tube 13 X-ray detector 14 Rotating device 15 Data collection device 20 Subject 21 Bed 22 Table 23 Slice surface 24 Continuous spiral rotation scan range 31 Memory 32 CPU
33 Gantry controller 34 Bed controller 35 Image reconstruction device 36 Image display circuit 37 Display device 38 Mouse controller 39 Mouse 41 Keyboard controller 42 Keyboard 43 Condition memory 44 Condition conversion device 51 Operation window

Claims (1)

Means for irradiating the subject with an X-ray beam; means for continuously rotating the irradiation direction of the X-ray beam around the subject; and a direction substantially perpendicular to the plane of rotation of the X-ray beam. Means for relatively moving the specimen, means for collecting data by detecting an X-ray beam transmitted through the specimen, and means for storing the conditions of plane rotation scanning performed respectively on a plurality of different slice planes of the specimen And an X-ray CT apparatus comprising: means for converting the plane rotation scan condition into a continuous spiral rotation scan condition.

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