JP4161468B2 - X-ray CT system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cone beam type X-ray CT apparatus that irradiates a subject such as a patient or an object with an X-ray that is spread outward in a cone shape.
[0002]
[Prior art]
Conventionally, when capturing a tomographic image of a subject, the imaging range and the position of the tomographic image to be imaged based on the fluoroscopic image of the subject captured in advance according to the imaging target, for example, 10 mm Create a so-called scan plan that sets the imaging pitch of tomographic images such as intervals, and based on the scan plan, determine the relative position between the subject and the device to match the imaging start position, and then operate the device I am letting.
[0003]
[Problems to be solved by the invention]
However, in the conventional case, although the scan plan is based on the fluoroscopic image of the subject, the actual imaging start position is determined based on the subject at that time, not the fluoroscopic image, when determining the actual imaging start position. I have to. Therefore, if there is an error in the position of the subject relative to the apparatus, there is a problem that a desired tomographic image cannot be obtained due to a shift in the imaging range.
[0004]
Also, for example, when the subject is a patient, when the imaging range is wide in the width direction of the body, such as the entire stomach or the entire abdomen, the imaging range is in the width direction of the body, such as the esophagus or spinal cord However, there are various imaging objects such as when the imaging range is narrow in both the body width direction and body axis direction, such as the liver.
[0005]
Therefore, in the X-ray CT apparatus, the X-ray source is provided with a diaphragm or the like so that the size of the field of X-rays irradiated on the subject can be changed.
However, in the conventional case, such a field of view of X-rays is uniquely determined according to an imaging target at the time of scan planning, and particularly when the size of the field of view is small, an object to be captured at the time of actual imaging. There is a problem that an error is easily generated in the relative position between the X-ray field and the X-ray field, and a desired tomographic image cannot be obtained.
[0006]
The present invention has been made in view of such circumstances, and based on the perspective image of the subject at the time of actual imaging, the imaging range for the subject and the position of the tomographic image to be reconstructed are determined. It is an object to be able to appropriately set and to obtain a desired tomographic image appropriately.
[0007]
[Means for Solving the Problems]
In order to achieve the above-described object, the X-ray CT apparatus of the present invention has an X-ray source that irradiates a subject with X-rays in a cone shape that spreads outward, and a field of X-rays that irradiates the subject. Irradiating field changing means for changing the size of the light source, a surface detector for incident cone-shaped X-rays that have passed through the subject, and a rotating means for rotating the X-ray source relative to the subject. And a moving means for moving the X-ray source and the surface detector relative to the subject in the direction of the rotation axis of the X-ray source, and collecting projection data of X-rays detected by the surface detector A data collection unit that performs reconstruction of a fluoroscopic image and a tomographic image based on projection data collected by the data collection unit, and a perspective image or a tomographic image reconstructed by the reconstruction processing unit. Display means for selecting and displaying at least one, and viewing X-rays irradiated on the subject X-ray visual field display means for overlapping the fluoroscopic image, imaging range setting means for setting the imaging range for the subject based on the fluoroscopic image displayed by the display means, and the display means Reconstructed image position setting means for setting a position of a tomographic image to be reconstructed based on a fluoroscopic image, and a tomographic image corresponding to the position based on the position of the tomographic image set by the reconstructed image position setting means And a set tomographic image extraction unit that is reconstructed by the reconstruction processing unit and displayed on the display unit.
[0008]
[Action]
The operation of the present invention is as follows.
According to the configuration of the X-ray CT apparatus of the present invention, at the time of actual imaging, first, X-rays are irradiated to the subject, and the X-ray projection data is detected by the surface detector to obtain the data collection unit. And the perspective image is reconstructed by the reconstruction processing unit based on the collected projection data. The reconstructed fluoroscopic image is displayed on the display means, and the X-ray visual field display means displays the X-ray field of view overlapping the fluoroscopic image, while visually confirming the displayed fluoroscopic image, The imaging range for the projectile and the position of the tomographic image to be reconstructed can be set, and the tomographic image at the set position can be displayed on the display means by the set tomographic image extracting means.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 is an overall schematic cross-sectional view of an X-ray CT apparatus according to the present invention. In this figure, reference numeral 1 denotes a bed capable of moving up and down on which a patient H as a subject is placed, and an elevator 2 such as a motor. (See FIG. 2) A top plate 5 on which a patient H is mounted is provided on a bed base 3 that can be moved up and down by means of a movable motor 4 that can move forward and backward as moving means. It is configured. The moving means may be configured using an air cylinder or the like.
[0011]
In the figure, reference numeral 6 denotes a gantry. The gantry 6 is formed with an insertion hole 7 through which the top plate 5 on which the patient H is mounted is inserted and removed, and the X-ray source 8 and the surface so as to surround the insertion hole 7. A detector 9 is provided.
[0012]
The gantry 6 is provided with an annular gantry 11 rotatably via a ball bearing 10, and this gantry 11 and a rotary motor 12 as a rotating means are interlocked and connected via a belt 13. An X-ray source 8 and a surface detector 9 are provided so as to rotate integrally in opposition to each other around the axis P, and the surface detector 9 further includes X-rays detected by the surface detector 9. A data collection unit (DAS) 14 for collecting the projection data is attached.
[0013]
FIG. 2 is a block diagram showing a schematic configuration of the X-ray CT apparatus according to the present invention. The X-ray source 8 emits X-rays from an X-ray tube 15 and X-rays emitted from the X-ray tube 15. The collimator 16 narrows the field of view, and is configured to irradiate the quadrangular surface detector 9 with an outwardly expanding cone-shaped (conical) X-ray.
[0014]
Two sets of optical sensors 19 including a projector 17 and a light receiver 18 are provided on the top of the gantry 6 so that the position of the X-ray tube 15 can be detected. The moving motor 4 is provided with a rotary encoder 20 that detects the amount of rotation of the motor 4 so that the amount of movement of the top 5 can be detected.
[0015]
As shown in FIG. 2, the data collection unit 14 is connected to a reconstruction processing unit 21 for reconstructing a fluoroscopic image and a tomographic image based on the projection data collected there. An image display device 22 as a means is connected and configured to display a fluoroscopic image and a tomographic image reconstructed by the reconstruction processing unit 21.
[0016]
The collimator 16 is provided with a diaphragm motor 23 as an irradiation field changing means for changing the size of the field of X-rays irradiated from the X-ray tube 15 to the patient H. The size of the imaging target, the size of the patient H, and the like The size of the X-ray field of view can be changed according to the above. The irradiation field changing means may be constituted by an assembly of elements that switch from a non-transmissive state to a transmissive state by applying a voltage.
[0017]
The lifting device 2, the moving motor 4, the rotation motor 12, the data collection unit 14, the X-ray tube 15, the reconstruction processing unit 21 and the diaphragm motor 23 are connected to the control device 24, and the operation unit 25 is connected to the control device 24. Has been. Although not shown, the optical sensor 19 and the rotary encoder 20 are also connected to the control device 24.
[0018]
The operation unit 25 includes an aperture dial 26 that adjusts the aperture by driving the aperture motor 23, an imaging range setting unit 27 and a reconstructed image position setting unit 28 each including a setting key and an end key. It has been.
[0019]
Further, an X-ray field display means 29 is connected to the control device 24, and the X-ray field display means 29 and the image display device 22 are connected. The field of view of X-rays irradiated to the patient H overlapping with the image can be displayed.
[0020]
Then, the imaging start position and the imaging end position can be set by the imaging range setting means 27 while moving the visual field with respect to the displayed fluoroscopic image and visually confirming the position of the visual field based on the fluoroscopic image. It has become. Similarly, the position of the tomographic image to be reconstructed can be set by the reconstructed image position setting means 28 while visually confirming the position of the visual field based on the fluoroscopic image.
[0021]
Further, a set tomographic image extraction unit 30 is connected to the control device 24, and the set tomographic image extraction unit 30 and the reconstruction processing unit 21 are connected to the tomographic image position set by the reconstruction image position setting unit 28. Based on this, the tomographic image corresponding to the position is reconstructed by the reconstruction processing unit 21 and can be displayed on the image display device 22.
[0022]
Next, a procedure for capturing a tomographic image with the above configuration will be described.
(1) The X-ray tube 15 is fixed in the uppermost position, and the size of the X-ray field of view by the collimator 16 is maximized by the diaphragm dial 26. In the case where the patient H is small or the like, as long as a visual field over the entire width of the chest and abdomen can be secured, the patient H may be appropriately reduced.
[0023]
(2) The lifting device 2 is driven in a state where the patient H is placed, and the bed base 3 is raised to a position lower than the rotational axis P, and then the moving motor 4 is driven to move the top plate 5 to the gantry 6. The X-ray tube 15 irradiates the X-ray tube 15 with an X-ray tube 15 as the irradiation start position, and the surface detector 9 detects the X-ray. The detected X-ray projection data is collected by the data collection unit 14, and a perspective image is reconstructed by the reconstruction processing unit 21 based on the collected projection data, and the perspective image HZ is converted into the perspective image HZ of FIG. As shown in the front view of the image display example of FIG. Here, the reason why the bed base 3 is raised only to a position lower than the rotational axis P is to bring the top 5 close to the surface detector 9 as much as possible so that the irradiation range of the X-ray source 8 to the patient H becomes wide. It is to do.
[0024]
(3) Next, the moving motor 4 is driven in reverse to return the top plate 5 to the X-ray irradiation start location, and the lifting device 2 is driven so that the body axis of the patient H becomes the location corresponding to the rotational axis P. In other words, the top plate 5 is raised so as to be at the same position as when the tomographic image is captured, and in that state, the X-ray field display means 29 displays the X-ray field S overlapping the fluoroscopic image HZ. Further, while confirming the relative position with the fluoroscopic image HZ, the size of the field of view S is set and adjusted by the diaphragm dial 26 so as to match the imaging target (see FIG. 3B).
[0025]
(4) After that, while confirming the relative position with the fluoroscopic image HZ, the visual field S is moved, stopped at the position where imaging is to be started, the setting key is operated, and the visual field S is further moved to perform imaging. Is stopped at the position where the user wants to end, the end key is operated, the imaging range setting means 27 sets the imaging start position L1 and the imaging end position L2, and the positions L1 and L2 are displayed on the image display device 22. [See (b) of FIG. 3].
[0026]
(5) Next, the images are switched, the reconstruction area A determined based on the imaging start position L1 and the imaging end position L2 is displayed on the image display device 22, and the reconstruction area A is visually confirmed. The tomographic image to be reconstructed by the reconstructed image position setting means 28 is operated by operating the setting key and operating the end key in a state where the center of the circular field of view S is located at the imaging start position of the region where the tomographic image is to be imaged. And the position D is displayed on the image display device 22 [see FIG. 3 (c)]. Here, only the imaging start location of the area where the tomographic image is to be captured is set because the imaging pitch of the tomographic image is preset according to the imaging target by the scan plan, and the end position of the tomographic image to be reconstructed by itself Because it is decided.
[0027]
(6) After the above setting, the top plate 5 is moved in the horizontal direction by the moving motor 4 so that the positions of the patient H and the X-ray source 8 become the imaging start location.
[0028]
(7) After that, the moving motor 4 and the rotary motor 12 are driven and the X-ray source 8 emits X-rays, so-called spiral scanning is performed, and the tomographic image at the set position is reconstructed by itself and displayed as an image. It is displayed on the device 22. Here, when the size of the visual field S in the body axis direction of the patient H is larger than the imaging range to cover the entire imaging range, only the rotary motor 12 is driven with the moving motor 4 stopped. What is necessary is just to perform what is called single scanning which irradiates X-rays from the X-ray source 8.
[0029]
With the above configuration, the fluoroscopic image HZ and the visual field S of the patient H at the time of imaging are displayed on the image display device 22 in an overlapping manner, and the imaging range and the position of the tomographic image to be reconstructed are confirmed while confirming the relative position. Since it can be set, the setting operation can be performed easily and appropriately.
[0030]
FIG. 4 is a block diagram of the main part showing an application example. The size of the field of view S set by the diaphragm dial 26 and the imaging range set by the imaging range setting unit 27 are input to the scan state selection unit 31. It is like that.
[0031]
In the scan state selection means 31, based on the relationship between the size of the field of view S and the imaging range, based on whether the size of the field of view S covers the entire imaging range, only the rotary motor 12 is operated with the moving motor 4 stopped. A state in which so-called single scanning is performed while driving and irradiating X-rays from the X-ray source 8 or so-called spiral scanning in which the moving motor 4 and the rotary motor 12 are driven and X-rays are irradiated from the X-ray source 8 is performed. It is configured to automatically determine and select a state to be performed, and input a command signal corresponding to the selected state to the control device 24 to control driving of the moving motor 4 and the rotary motor 12.
[0032]
That is, as shown in the diagram for explaining the scan state selection in FIG. 5, when the imaging range R is wide and the size of the field of view S in the body axis direction of the patient H is large [see (a) of FIG. 5], and When the imaging range R is narrow and the size of the visual field S in the body axis direction of the patient H is small [see (b) in FIG. 5], the size of the visual field S in the body axis direction of the patient H is the imaging range R. If the field of view S is larger than the entire imaging range R, the single scan is automatically selected.
[0033]
As shown in FIG. 5C, the size of the visual field S is smaller than the imaging range R, the size of the visual field S in the body axis direction of the patient H is smaller than the imaging range R, and the size of the visual field S. When the camera cannot cover the entire imaging range R, the spiral scan is automatically selected. Other configurations are the same as those of the above-described embodiment, and illustration and description thereof are omitted.
[0034]
According to the configuration of this application example, since the selection operation of single scan or spiral scan can be automatically performed based on the relative relationship between the imaging range R and the size of the field of view S, the entire imaging range R can be appropriately imaged. Unnecessary X-ray irradiation can be eliminated, and the burden of exposure on the patient H can be reduced.
[0035]
In the above-described embodiment, X-rays are emitted from the X-ray source 8 in the form of an outwardly expanding cone. However, in the present invention, for example, the X-rays are outwardly expanded, for example, in the form of an outwardly expanding quadrangular pyramid. As long as it is configured to irradiate in a cone shape.
[0036]
The X-ray CT apparatus of the present invention is not limited to the X-ray source 8 and the surface detector 9 provided in the gantry 6 so as to rotate integrally as in the above-described embodiment. For example, the X-ray CT apparatus is larger than 180 °. An X-ray source 8 is provided on one end side of a C-shaped arm provided to be rotatable at an angle, and a surface detector 9 is provided on the other end side, or only the X-ray source 8 is provided to be rotatable. Various modifications can be made, such as a long width (for example, 50 cm or more) in the direction of the rotation axis and a ring-shaped fixed surface detector 9 provided over the entire circumference.
[0037]
The X-ray CT apparatus of the present invention is not limited to medical use for imaging the patient H, but can also be applied to nondestructive inspection applications such as imaging and flaw detection of an object. Collectively called a subject.
[0038]
Further, the X-ray CT apparatus of the present invention may be configured to rotate the subject with respect to the X-ray source 8 and the surface detector 9, and further, the X-ray source 8 and the surface detector 9. May be configured to move in the direction of the rotational axis with respect to the subject.
The rotation axis when the subject is rotated with respect to the X-ray source 8 and the surface detector 9 is also referred to as the rotation axis of the X-ray source.
[0039]
【The invention's effect】
As described above, according to the X-ray CT apparatus of the present invention, based on the fluoroscopic image of the subject at the time of actual imaging, the relative position with the field of view of the X-ray displayed overlapping there is visually confirmed. However, since the imaging range with respect to the subject and the position of the tomographic image to be reconstructed can be appropriately set, a desired tomographic image can be appropriately obtained regardless of the imaging target.
[Brief description of the drawings]
FIG. 1 is an overall schematic cross-sectional view of an X-ray CT apparatus according to the present invention.
FIG. 2 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to the present invention.
FIG. 3 is a front view of an image display example.
FIG. 4 is a block diagram of a main part showing an application example.
FIG. 5 is a diagram for explaining scan state selection;
[Explanation of symbols]
4 ... Moving motor (moving means)
8 ... X-ray source 9 ... Surface detector 12 ... Rotating motor (rotating means)
14 ... Data collection unit 21 ... Reconstruction processing unit 22 ... Image display device (display means)
23 ... Aperture motor (irradiation field changing means)
27 ... Imaging range setting means 28 ... Reconstructed image position setting means 29 ... X-ray field display means 30 ... Set tomographic image extraction means H ... Patient (subject)
HZ ... perspective image P ... rotation axis S ... field of view

Claims (1)

An X-ray source for irradiating the subject with X-rays in a cone shape, an irradiation field changing means for changing the size of the field of view of the X-rays radiated to the subject, and the outer extension through the subject A surface detector for incident cone-shaped X-rays, a rotating means for rotating the X-ray source relative to the subject, and the X-ray source and the surface detector relative to the subject. A moving means for moving the X-ray source in the direction of the axis of rotation, a data collection unit for collecting X-ray projection data detected by the surface detector, and fluoroscopy based on the projection data collected by the data collection unit A reconstruction processing unit for reconstructing an image and a tomographic image; display means for selecting and displaying at least one of a fluoroscopic image or a tomographic image reconstructed by the reconstruction processing unit; and X-rays applied to a subject X-ray field display means for displaying the field of view overlapping with the fluoroscopic image, and the display means An imaging range setting unit that sets an imaging range for the subject based on the displayed fluoroscopic image, and a reconstructed image position that sets a position of a tomographic image to be reconstructed based on the fluoroscopic image displayed on the display unit Based on the position of the tomographic image set by the setting means and the reconstructed image position setting means, the tomographic image corresponding to that position is reconstructed by the reconstruction processing unit and displayed on the display means An X-ray CT apparatus comprising an extraction unit.

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