JP3275948B2 - X-ray CT system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus used in the field of medicine and the like, and more particularly to an X-ray CT apparatus having a function of making an imaging plan and performing imaging as planned.
Related to the device.

[0002]

2. Description of the Related Art An X-ray CT apparatus collects data on the amount of attenuation of X-rays in a substance, which is a subject, from a plurality of angles, and performs image reconstruction processing on the data using a computer. This is to obtain a distribution image of the X-ray absorption coefficient. An X-ray CT apparatus having a function of making an imaging plan and performing imaging according to the plan usually captures a CR image (an X-ray transmission image viewed from one direction), and performs multiple slices on the CR image. When the position and the size and center of the image reconstruction area in each of them are set, the imaging (data collection) and image reconstruction in each slice are automatically performed as set.

[0003]

However, the conventional X-ray CT apparatus has a problem that it is difficult to properly set an imaging plan. That is, conventionally, a CR image is displayed, and the slice position and the size and center of the reconstruction area are set on the display image. However, since the CR image does not include information in the depth direction, The position in the depth direction cannot be appropriately set, and the target portion to be observed may be shifted or protruded from the reconstruction area in some cases.

In view of the above, it is an object of the present invention to provide an X-ray CT apparatus improved so that an appropriate imaging plan can be easily set.

[0005]

In order to achieve the above object, in an X-ray CT apparatus according to the present invention, an X-ray irradiating means for irradiating an X-ray toward an examination space, and an X-ray irradiating means for inspecting the X-ray irradiating means. Scanning means for rotating around a space to irradiate from various directions; X-ray detecting means arranged opposite to the X-ray irradiating means across an examination space; Moving means for changing the relative positional relationship between the X-ray irradiating means and the scanning means while controlling the moving means and controlling the scanning means while maintaining the positional relationship between the subject and the examination space in a predetermined relationship. A CT imaging unit for acquiring data in various directions, a CT image reconstruction unit for obtaining a distribution image of an X-ray absorption coefficient in a slice of a subject by performing image reconstruction processing on the data, and a scanning unit for controlling the scanning unit X-ray irradiation direction CR imaging means for controlling the moving means while fixed and moving the subject linearly relative to the examination space to capture a CR image; display means for displaying the CR image; and displaying the CR image on the displayed CR image. Setting means for setting a plurality of slice positions and the size and center position of the reconstructed area at each of them, and CT imaging at at least one slice position as set for at least one slice by controlling the moving means Is performed, data is collected, the data is subjected to image reconstruction processing, a CT image is obtained, and this is displayed on the display means to enable position setting on the CT image, and the position on the CT image is set. After correcting the center position based on the settings, CT imaging is performed on the other slices at the slice positions as set, data is collected, the data is subjected to image reconstruction processing, and each slice is processed. And control means so as to obtain a CT image at the position is provided.

[0006] A plurality of slice positions on the CR image and the size and center position of the reconstruction area at each of the slice positions are set. Then, based on this, CT imaging is performed on the at least one slice at the set slice position and data is collected. This data is subjected to image reconstruction processing to obtain a CT image, and this CT image is displayed. Therefore, if the position is set on the displayed CT image, the position of the CR image in the depth direction has been set, and the center position can be corrected. For other slices, CT imaging is performed at the slice position as set and data is collected, but since image reconstruction of each slice is performed based on the corrected center position,
The target portion to be observed does not protrude or shift from the image reconstruction area. Thus, appropriate settings can be easily made.

[0007]

Next, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, an X-ray tube 12 and an X-ray detector 13 are arranged on a gantry 11 so as to face each other. The X-ray tube 12 and the X-ray detector 13
Is a test space, and the subject 20 is arranged in the test space. A data collection device 14 is connected to the X-ray detector 13 and collects data on attenuation of X-rays transmitted through the subject 20. X-ray tube 1
The X-ray detector 2 and the X-ray detector 13 are rotated by a rotating device (not shown) in the gantry 11 in a plane perpendicular to the paper surface. That is, it rotates around the examination space in which the subject 20 is arranged (around the body axis of the subject 20). Subject 2
0 is laid on the table 22 of the bed 21. The table 22 is moved linearly by a driving device (not shown) provided in the bed 21.

The gantry 11 is controlled by a gantry controller 15 connected to a CPU 31. The gantry 11 has a built-in high-voltage control device (not shown) for controlling a high voltage applied to the X-ray tube 12.
X-ray irradiation from the tube 12 is controlled. Further, the rotation of the rotating device is controlled, and the X-ray tube 12 and the X-ray detector 13 rotate. Further, the entire gantry 11 rotates in a vertical plane including the body axis of the subject 20 as shown by an arrow (tilts.
The tilt can be controlled by the gantry controller 15. The bed 21 is controlled by a bed controller 23,
The movement of the table 22 is controlled under the control of the CPU 31.

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. The subject 20 uses this XY
It will be moved in the Z direction perpendicular to the plane as indicated by the 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 beam is rotationally scanned in an XY plane perpendicular to the body axis. When the gantry 11 is tilted, the plane scanned by the X-ray beam rotates and tilts from the XY plane to the XY plane with the X axis as the rotation center axis.

Next, a further explanation will be given with reference to a flowchart shown in FIG. First, as shown in FIG.
CR imaging is performed. That is, the X-ray tube 12 and the X-ray detector 13 (data collection device 14) are rotated and stopped at a predetermined angle. For example, from the state shown in FIG.
Ray tube 12 and X-ray detector 13 (data collection device 14)
Is rotated by 90 ° so that the X-ray beam is emitted from the lateral direction (the body side direction) of the subject 20 and fixed at that angle. In this state, irradiation with an X-ray beam is performed, and the subject 20 is moved in the Z direction during the irradiation. The data obtained at this time is once stored in the memory 32 via the CPU 31, read out, and sent to the CR image reconstruction device 33.
The CR image reconstructing device 33 arranges the data for each movement position of the table 22 so that the X-ray irradiation direction (in this case, the body side direction) in the range irradiated with the X-ray beam by the movement of the subject 20 is obtained. A CR image, which is an X-ray transmission image as seen, is reconstructed.

The CR image is sent to a display device 37 via an image display circuit 36, and is displayed as shown in FIG. Here, a lumbar spine examination (myelography) is performed, and a CR image from the side of the lumbar region is obtained and displayed. Since each vertebral body of the lumbar spine is shown in this CR image, four slices are set for each vertebral body. The positions of the four slices are determined by setting the linear cursor 51 on the screen. The size D of the image reconstruction area (FOV) in each slice
And the center position (X, Y) of the area is indicated by each straight line cursor 5
The setting is made by placing a cursor 52 and a cursor 53 on 1.

For this cursor operation, a mouse 39 is connected to the CPU 31 via a mouse controller 38 and a keyboard 42 is connected to the CPU 31 via a keyboard controller 41. By operating the mouse 39 and the keyboard 42, the cursors 51 to 53 are set or moved.

Thus, the imaging plan has been set. In this case, since the CR image has only information on the YZ plane in this case, it is impossible to set the X-direction coordinate of the center position of the reconstruction area. Therefore, the position in this direction is set to a default value (for example, the X-ray tube 12 and the X-ray tube 12). The rotation center of the X-ray detector 13) is used instead of the final state. First, CT imaging is performed at the first (i = 1) slice position based on this imaging plan.
That is, the gantry 11 is tilted by the same angle as the inclination of the first (rightmost) linear cursor 51, and then the table 22 is moved so that the position where the X-ray beam passes coincides with the set Z-direction position. I do. In this state, the X-ray tube 12 and the X-ray detector 13 (data collection device 14) are rotated. When the X-ray tube 12 and the X-ray detector 13 (data collection device 14) rotate, the amount of X-ray attenuation in a plane through which the X-ray beam passes, that is, on the slice plane corresponding to the first linear cursor 51 The data for each angular direction is collected and stored in the memory 32.

The data is read from the memory 32 and sent to a CT image reconstruction device 34 to perform image reconstruction processing. The obtained CT image is sent to a display device 37 via an image display circuit 36. , Are displayed as shown in FIG. This CT image represents information on the XY plane, and it can be seen that the image of the vertebral body, which is the target portion to be observed, protrudes from the FOV in the X direction. Therefore, the center position of the FOV is shifted by ΔX in the X direction. The correction value ΔX is set by moving the cursor as described above. This correction value Δ
X corrects the center position of the FOV in each of the first to fourth (i = 1 to 4) slices.

As a result, the FOV is reset and determined. Based on this, CT imaging (scan for data acquisition) and CT image reconstruction are performed for each slice. For the first (i = 1) slice, since CT imaging has been completed and data has been collected as described above, only the CT image reconstruction processing is performed again, and the vertebral body, which is the target portion to be observed, is obtained. A CT image in which the image is located at the center of the FOV is obtained. From the other second (i =
With respect to the slices 2 to 4), CT images can be obtained from CT imaging in which the image of the vertebral body, which is the target portion, is located at the center of the FOV.

It should be noted that the first slice may be subjected to CT imaging similarly to the second and subsequent slices. In the above description, the correction value ΔX is set only in the X direction on the CT image, but the correction value in the Y direction can be set. Further, after explicitly setting the FOV on the CR image as described above, a CT image is obtained and displayed.
Instead of correcting the value set on the image,
It is also possible to simply set the slice position (straight line cursor 51) on the image, obtain a CT image by using default values for all FOVs, and display and correct the CT image.

The position correction is performed on the CT image of the first slice. However, the position correction is not limited to this, and may be performed on the CT image of an arbitrary slice or the CT images of all slices. Good. In the above description, a CR image from the lateral direction (X direction) of the subject 20 is obtained, an imaging plan is made on the CR image, and the position in the X direction is corrected on the CT image. After obtaining a CR image from (Y direction), an imaging plan is made using the CR image, and C
Needless to say, the Y-direction position may be corrected on the T image.

Further, correction of the position on the CT image (ΔX
Is manually performed by operating the mouse 39 or the like in the above description, but it can be automatically performed. In the automatic case, for example, a threshold value for a pixel value is determined, the center of gravity (or the center) of a region exceeding the threshold value is calculated to obtain the center of gravity of a vertebral body as a target part, and the position is determined as FO.
It can be configured to automatically set the center position of V.

In addition to the above, the present invention is not limited to an X-ray CT apparatus that employs a scanning method of scanning the X-ray beam by simultaneously rotating the X-ray tube 12 and the X-ray detector 13 as described above. The X-ray beam scanning method described above is also applicable. The change in the positional relationship between the X-ray beam (that is, the examination space from which the X-ray beam is emitted) and the subject 20 is changed by linearly moving the table 22 of the bed 21 and tilting the gantry 11. Since the positional relationship between them is relative, other configurations such as moving the gantry 11 instead of moving the table 22 are also conceivable.

[0020]

As described above, the X-ray C of the present invention
According to the T device, an appropriate imaging plan can be easily set. In particular, when the CT image reconstruction area in each slice is independently set on the CR image and a CT image in which the target part is enlarged is obtained, the target part is reconstructed on the CR image because the reconstruction area is small. Although they often protrude from the constituent area, they are effective in preventing such inconveniences, and are therefore effective for lumbar spine examination (myelography) and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an X-ray CT apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation.

FIG. 3 is a view showing a CR image.

FIG. 4 is a diagram showing a CT image.

[Explanation of symbols]

REFERENCE SIGNS LIST 11 gantry 12 X-ray tube 13 X-ray detector 14 Data collection device 15 Gantry controller 20 Subject 21 Bed 22 Table 23 Bed controller 31 CPU 32 Memory 33 CR image reconstruction device 34 CT image reconstruction device 36 Image display circuit 37 Display device 38 Mouse controller 39 Mouse 41 Keyboard controller 42 Keyboard 51 Cursor indicating slice position 52 Cursor indicating FOV size 53 Cursor indicating FOV center position

Claims (1)

(57) [Claims] An X-ray irradiating means for irradiating an X-ray toward an examination space; a scanning means for rotating the X-ray irradiating means around the examination space so as to irradiate the X-ray from various directions; X-ray detecting means arranged opposite to the X-ray irradiating means with a distance therebetween, moving means for changing the relative positional relationship between the subject and the examination space, and controlling the moving means to control the subject CT imaging means for controlling the scanning means and rotating the X-ray irradiating means to collect data in various directions while maintaining the positional relationship between the object and the examination space in a predetermined relation, and performing image reconstruction processing on the data. CT image reconstruction means for obtaining a distribution image of an X-ray absorption coefficient in a slice of a subject,
CR imaging means for controlling the scanning means and controlling the moving means while keeping the X-ray irradiation direction fixed to move the subject relatively linearly with respect to the examination space to capture a CR image; Display means for displaying the CR, and the displayed CR
Setting means for setting a plurality of slice positions on the image and the size and center position of the reconstruction area at each of the slice positions,
The moving means is controlled to perform CT imaging at at least one slice position for at least one slice to collect data.
An image is obtained and displayed on the display means to enable position setting on the CT image. In addition, the center position is corrected based on the position setting on the CT image, and other slices are set as set. An X-ray CT apparatus comprising: control means for performing CT imaging at a slice position to collect data and performing image reconstruction processing on the data to obtain a CT image at each slice position.