JP3508375B2 - X-ray CT system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus, and more particularly to a continuous rotation type X-ray CT apparatus for collecting data in a spiral. 2. Description of the Related Art A continuous rotation type X-ray CT apparatus continuously rotates an irradiation direction of an X-ray beam around a subject. Put the X-ray tube and X-ray detector in the gantry,
In an X-ray CT apparatus of a type in which the X-ray beam irradiation direction is rotated about the subject by rotating them integrally to collect projection data in each angular direction, an electrical connection during rotation by a slip ring or the like is provided. By securing X
The X-ray detector and the X-ray detector can be continuously rotated in one direction. When the subject is inserted and moved in the plane where the X-ray beam is continuously rotating, the subject is scanned spirally by the X-ray beam, and the X-ray beam is scanned by the spirally scanned X-ray beam. Line absorption data can be collected. When scanning the lungs of a subject,
In the meantime, it is necessary to have the subject hold his / her breath so as not to move. If the scanning range (moving range) is wide, it takes a long time to scan the entire range, so that the time to stop breathing is also long. Therefore, if the respiratory arrest period is too long, instead of imaging with a single spiral scan, scan the imaged site in several places so that the respiratory arrest period does not become longer in each case. I have to. Alternatively, in consideration of the maximum time during which the breathing can be stopped, the moving speed of the table on which the subject is placed may be increased so that the scan is completed in the entire range within that time. [0004] However, if the respiratory arrest period is too long, the burden on the subject increases, which is a problem. In addition, when scanning is performed by dividing the image into several regions, it is necessary to make various settings after the operator has to determine how to divide the image, so that the operation is complicated and complicated. . Furthermore, if the moving speed of the table on which the subject is placed is increased, the quality of the data deteriorates. SUMMARY OF THE INVENTION In view of the above, the present invention provides a continuous rotation type X-ray CT apparatus in which a scan range can be appropriately divided by a simple and easy operation when a wide range is spirally scanned. The purpose is to do. In order to achieve the above object, in an X-ray CT apparatus according to the present invention, a means for irradiating an object with an X-ray beam, and an irradiation direction of the X-ray beam Means for continuously rotating the subject around the subject,
Means for relatively moving the subject in a direction substantially perpendicular to the plane of rotation of the X-ray beam, and the subject being spirally transmitted by moving the subject relative to the rotating X-ray beam Means for collecting X-ray data, means for setting a range of a moving direction in which the data is collected, and calculating a data collection time from the set moving range and the moving speed, wherein the calculation time is longer than a predetermined time. Control means for automatically dividing the set movement range, sequentially moving the subject for each of the divided movement ranges, and separately performing spiral X-ray transmission data collection for each of the movement ranges. And image reconstruction means for reconstructing an image of the entire set movement range from the collected spiral X-ray transmission data. [0007] When a range (a range in the moving direction of the subject) for collecting data of the X-rays transmitted through the subject spirally is set, the time required for data collection is calculated from the set moving range and the moving speed. . When this time is longer than a predetermined time set as a time that does not hinder breathing, the moving range is automatically divided. Then, the subject is sequentially moved for each of the divided moving ranges, and spiral X-ray transmission data is separately collected for each of the moving ranges. Therefore, in each of the divided movement ranges, the time required for data collection is shorter than the above-mentioned predetermined time, and it is not necessary to hold the breath for a long time. Since the control of the division and the data collection after the division is automatically performed, it is not necessary to perform a troublesome operation, and the operation is facilitated. Since the moving speed is not increased, the quality of collected data does not deteriorate. Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of an X-ray CT apparatus according to the present invention.
In this figure, an X-ray tube 12 and an X-ray detector 13 are arranged opposite to each other on a gantry 11, and the X-ray tube 12 and the X-ray detector 13 are rotated by a rotating device 14 in a plane perpendicular to the plane of the drawing. Have been to be. The table 2 of the bed 21 is placed in a space between the X-ray tube 12 and the X-ray detector 13.
The subject 20 laid on the side 2 is inserted. Table 2
2 is a driving device (not shown) provided in the bed 21
Can be moved linearly. Assuming that the horizontal direction of the paper is Z, the vertical direction is Y, and the direction perpendicular to the paper is X, the X-ray tube 12 and the X-ray detector 1
3 rotates in the XY plane, and the subject 20 is inserted in the Z direction perpendicular to the XY plane as indicated by an arrow. When viewed from the subject 20, the Y direction is the front-back direction, the X direction is the left-right direction, and the Z direction is the body axis direction. That is, the X-ray is rotationally scanned in the XY plane perpendicular to the body axis, and the X-ray detector 13 outputs the X-ray.
Projection data in each angular direction regarding X-ray absorption in a plane through which the line passes is obtained as detection data. This detection data is sent to the memory 31 via the data collection device 15. The angle signal from the rotating device 14 and the position signal of the table 22 (that is, the subject 20) from the bed 21 are also sent to the memory 31, and the above detection data is stored together with the angle signal and the position signal. You. The CPU 32 fetches 360 ° (or 180 °) projection data for a certain position from the memory 31 and sends it to the image reconstructing device 35 to perform a back projection process or the like in accordance with the angle, thereby obtaining the data. A tomographic image in the position plane is reconstructed. If data is sequentially read from the memory 31 for each position and image reconstruction is performed, a large number of tomographic images in the moving range of the table 22 (the subject 20) can be obtained. The image data of these reconstructed images is sent to the image display circuit 36 via the CPU 32, and is displayed on the display device 37. The CPU 32 includes a mouse controller 38
And a keyboard 42 via a keyboard controller 41, respectively, to set a scan range (range in the Z direction) prior to the spiral scan. Alternatively, a scan range may be set by capturing a transmission image of the subject 20 in advance, displaying the transmission image on the screen of the display device 37, and moving a cursor on the image. The transmitted image is obtained by moving the table 22 while the X-ray tube 12 and the X-ray detector 13 are fixed without rotating.
The subject 20 passes through the fixed X-ray beam in the body axis direction, and at this time, data obtained by the X-ray detector 13 and the data collection device 15 is stored in the memory 31, and this data is stored for each position. Can be created by lining up. For example, a transmission image 52 viewed from the front of the subject 20 is displayed on the display screen 51 as shown in FIG. By moving the position of the line cursor 53 on this image by operating the mouse 39 or the like, the scan range in the body axis direction is set. When the scan range in the body axis direction is set in this way, the CPU 32 calculates the time required for scanning by dividing the set range (mm) by the moving speed (mm / sec) of the table 22. The moving speed of the table 22 is separately input from the keyboard 42 or the like. If the scan time is shorter than a predetermined time set in advance, the imaging scan is started as it is, and if the scan time is long, a warning window 54 as shown in FIG. The predetermined time is input by the operator in advance by determining how long the scan time will take to divide the scan range. Unless the operator changes this value, the predetermined time is used. Even when the power is turned off, it is held in the memory of the CPU 32 or the like.
This time is determined within a range that does not hinder the normal subject 20 from holding his / her breath, and can be set to, for example, 15 seconds. If it is calculated by the CPU 32 that the image pickup time takes 30 seconds in the scan range set here, it is longer than the above 15 seconds.
Displays a message as shown in FIG. If the operator wants a split scan, he presses the "Yes" button. Then, the CPU 32 automatically sets conditions so that the scan range is divided and scanning is performed for each of the scan ranges. As a method of dividing, for example, as shown in FIG. 4A, a method of dividing equally so that the time after division is within the above set time of 15 seconds or FIG.
As shown in (b), a method of dividing the set time into 15 seconds and setting the remaining time as an independent scan time can be considered. As described above, when the scan range is automatically divided and individual conditions are set, the CPU 32
Controls the rotation device 14 and the like in the gantry 11 via the gantry controller 33, and controls the movement of the table 22 of the bed 21 via the bed controller 34. Thus, the spiral scan is sequentially performed in each of the divided scan ranges. Since a predetermined time interval is automatically provided between the individual spiral scans, the subject 20 can take a breath in the meantime and prepare for breath holding at the next scan time, and the subject 2
No burden on 0. The above description has been made with reference to one example, and the present invention is not limited to this. For example, the display of the warning window 54 can be different. The above description is based on the X-ray tube 12 and the X-ray detector 1.
The present invention is applied to an X-ray CT apparatus of a type in which the X-ray tube 3 and the X-ray tube 3 are integrally rotated. Needless to say, the present invention can be applied to other types of X-ray CT apparatuses such as a line CT apparatus. As described above, the X-ray C of the present invention
According to the T device, when the range of data collection spirally is large and takes a long time, the range is automatically divided, and the time required for each of them is set to a short time that does not hinder breathing. In addition, the subject is not forced to hold his / her breath for a long time, and the burden on the subject can be reduced. In addition, this division is automatically performed, and various settings for scanning in each range after the division are also automatically performed. Therefore, it is not necessary to perform a troublesome operation, and the operation is facilitated. Further, since the moving speed of the subject is not increased, deterioration of the quality of the collected data can be prevented.

[Brief description of the drawings] FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing a display screen. FIG. 3 is a diagram showing a warning window at the time of division. FIG. 4 is a diagram showing a dividing method. [Explanation of symbols] 11 Gantry 12 X-ray tube 13 X-ray detector 14 Rotating device 15 Data collection device 20 subjects 21 beds 22 tables 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 51 Display screen 52 Transmission image 53 line cursor 54 Warning Window

Claims (1)

(57) Claims: means for irradiating an object with an X-ray beam, means for continuously rotating the irradiation direction of the X-ray beam around the object, Means for relatively moving the subject in a direction substantially perpendicular to the plane of rotation of the X-ray beam; and X for transmitting the subject spirally by moving the subject with respect to the rotating X-ray beam. Means for collecting line data, means for setting a range in the moving direction for collecting data, and calculating data collection time from the set moving range and the moving speed, when the calculation time is longer than a predetermined time. Control means for automatically dividing the set movement range, sequentially moving the subject for each of the divided movement ranges, and separately performing spiral X-ray transmission data collection for each movement range; Spiral X-ray transmission data collected X-ray CT apparatus characterized by comprising an image reconstructing unit for performing an image reconstruction of the entire set movement range of the from.