JP4672099B2 - X-ray diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an X-ray diagnostic apparatus that can image a subject from any direction, up, down, left, and right, and can rotate around the subject to collect data necessary for three-dimensional image reconstruction. About.
[0002]
[Prior art]
In many X-ray diagnostic apparatuses, an X-ray tube and an X-ray detector are mounted on a support that can be angled in a wide range so that the subject can be imaged from any direction in the vertical and horizontal directions. This support has, for example, a C-shape, U-shape, or Ω-shape, and is called a C-arm, U-arm, or Ω-arm because of its shape.
[0003]
By the way, the visual field as a system is determined by the size of the detection surface of the X-ray detector, specifically, the diameter of the entrance window of the image intensifier. Of course, it is preferable to have a large field of view that can accommodate the entire target region. However, if the field of view is to be increased, the X-ray detector is also increased in size accordingly, so that the movement of the support is extremely restricted. Considering these two surfaces, for example, in a detector for abdominal examination, the field of view is 14 [inch] (≈355.6 [mm]), and at most 16 [inch] (≈406.4 [mm]) ). In recent years, an ultra-large image intensifier of 22 [inch] (≈558.8 [mm]) has appeared, but the movement of the supporter is very limited, and the supporter is also It is very large in size.
[0004]
[Problems to be solved by the invention]
As described above, since the field of view cannot be so large, various restrictions may be imposed depending on the shooting mode. Three prominent examples are described below.
(1) Three-dimensional image reconstruction In recent years, X-ray diagnostic apparatuses perform three-dimensional image reconstruction like an X-ray computer tomography apparatus based on image data collected from various angles using a high-speed rotation mechanism. It has come to be. By the way, in order to perform three-dimensional image reconstruction, it is required to collect data of at least 180 degrees plus α (α: divergence angle of X-ray beam) over a half circumference of the subject (projection theorem).
[0005]
However, the mainstream 14 [inch] or 16 [inch] image intensifier is too short for the width of the subject. That is, the entire image does not fit in the field of view (frame) in the width direction of the subject. Therefore, at present, the three-dimensional image reconstruction is performed only on the blood vessel region based on the DSA (Digital Subtraction Angiography) image data obtained by subtracting the images before and after the injection of the contrast agent. However, in order to perform surgical treatment in particular, it is necessary to have a relationship with bones and other organs even in the treatment of the vascular system. From such a background, it is strongly desired to enlarge the detection surface while satisfying the condition that the movement of the supporter is not restricted and does not get in the way during normal photographing.
[0006]
(2) Lower limb angiography examination In the part from the abdomen to the lower limb, most major blood vessels extend substantially parallel to the body axis direction. For this reason, the larger the visual field in the body axis direction, the more effective for lower limb angiography examination. However, the larger the field of view, the more restricted the movement of the support as described above.
[0007]
(3) Similar to stepping imaging, blood vessels extend substantially parallel to the body axis direction in the portion from the abdomen to the lower limbs. Therefore, in contrast imaging, in principle, a single contrast agent injection can be provided. However, since the field of view is only 16 [inch] at the maximum as described above, in order to photograph a wide range from the abdomen to the lower limbs, the stepping photographing, that is, the cycle of sliding the bed at a fixed interval, stopping, and photographing is repeated. Shooting. However, so-called motion artifacts (blurring) occur due to body movements of the subject accompanying rapid and intermittent movement of the bed slide. In order to suppress this body movement, it is only necessary to firmly fix the subject on the bed, but as a result, the subject is not unpleasantly felt.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide an X-ray diagnostic apparatus capable of enlarging the visual field without excessively restricting the movement of the support.
[0009]
[Means for Solving the Problems]
The present invention is directed to an X-ray tube, a planar X-ray detector having a rectangular detection surface having a long side and a short side , and the X-ray tube and the X-ray detector facing each other with a subject interposed therebetween. An arm that supports the arm, a holding device that rotatably holds the arm with respect to at least two axes, and a rotation mechanism that rotatably supports the X-ray detector around a rotation axis substantially perpendicular to the detection surface; And a controller that controls the rotation mechanism so that either the long side or the short side of the X-ray detector is substantially parallel to the body axis of the subject.
[0010]
(2) The present invention is characterized in that, in the apparatus of (1), the ratio of the long side to the short side of the detection surface of the planar X-ray detector is 1.3 or more.
[0011]
(3) In the apparatus of (1), the present invention is characterized in that the ratio of the long side to the short side of the detection surface of the planar X-ray detector is 1.5 or more.
[0012]
(4) The present invention is characterized in that, in the apparatus of (1), image data corresponding to an arbitrary part in the detection surface of the planar X-ray detector can be generated.
[0013]
(5) The present invention is characterized in that, in the apparatus of (4), the X-ray aperture changes according to the position and range of a part where the image data is generated.
[0014]
(6) In the apparatus of (1), the present invention is characterized in that the planar X-ray detector is slidably supported in a direction parallel to the long side of the detection surface.
[0015]
(7) The present invention is characterized in that, in the apparatus of (1), the planar X-ray detector is rotatably supported at a position shifted from the center of the detection surface.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail according to preferred embodiments with reference to the drawings.
FIG. 1 shows the configuration of the X-ray diagnostic apparatus according to this embodiment, and FIG. 2 shows the appearance of the gantry portion of FIG. The gantry portion 1 has an X-ray tube 3 and a planar X-ray detector 5. The planar X-ray detector 5 has a plurality of X-ray detection elements. As an X-ray detection element, for example, an X-ray consisting of a semiconductor layer, a voltage application electrode formed on the surface of the semiconductor layer, and a signal electrode formed on the back surface of the semiconductor layer is directly converted into an electric signal. A possible semiconductor cell is employed. As a detection principle, when X-rays are incident on the semiconductor layer, electron-hole pairs generated by the ionization action are attracted to the reverse-biased electrodes, respectively, and thereby a signal current corresponding to the intensity of the incident X-rays is generated. It occurs. Other structures such as a combination of a scintillator and a photodiode may be adopted as the X-ray detection element.
[0017]
As shown in FIGS. 3 and 4, the plurality of X-ray detection elements constituting the flat X-ray detector 5 are arrayed in a matrix so that the detection surfaces 63 are substantially rectangular. For example, the detection surface 63 has a short side of 16 inches (about 406.4 mm) and a long side of 25 inches (about 635 mm). Of course, the size of the detection surface 63 is not limited to 16 × 25 inches, but the length of the short side is not less than 350 mm and not more than 450 mm, the length of the long side is not less than 550 mm and not more than 700 mm, and the length of the short side is A rectangular shape having a long side ratio of 1.3 or more, more preferably 1.5 or more is preferable.
[0018]
The X-ray tube 3 is supported by one end of the C arm 51. An X-ray diaphragm device 9 is disposed in the X-ray emission window of the X-ray tube 3 in order to limit the X-ray irradiation field on the subject. At the other end of the C-arm 51, the flat X-ray detector 5 is opposed to the subject placed on the bed 11 with the rod-shaped rotation mechanism 13 and the slide mechanism 15 therebetween. Supported. The planar X-ray detector 5 can rotate about a rotation axis substantially orthogonal to the detection surface as indicated by an arrow D by the rotation mechanism 13. Further, the flat X-ray detector 5 can slide in the direction of the long side of the detection surface as indicated by an arrow C by the slide mechanism 15.
[0019]
The rod 52 of the rotation mechanism 13 is divided into a rod upper portion 53 and a rod lower portion 55, and the rod lower portion 55 is rotatable with respect to the rod upper portion 53 by the internal structure shown in FIG. That is, the rod upper portion 53 and the rod lower portion 55 are connected with the bearing 65 interposed therebetween, and the rotation of the stepping motor 67 fixed to the rod upper portion 53 is transmitted to the rod lower portion 55 via the drive gear 69, thereby the rod The lower part 55 rotates. An electromagnetic clutch 71 is provided between the stepping motor 67 and the drive gear 69. When the clutch release button 59 shown in FIG. 3 is pressed by the operator, the electromagnetic clutch 71 is released. As a result, the rotation of the detector 5 becomes free, and the operator can manually rotate the detector 5 while holding the handle 57.
[0020]
The rotation angle of the detector 5 is detected by a rotary encoder 73 fixed to the rod upper portion 53 via a driven gear 75 that rotates according to the rotation of the rod lower portion 55. Further, power and signals are transferred between the rod upper portion 53 and the rod lower portion 55 by a slip ring 77, whereby the detector 5 can be rotated by 140 degrees or more.
[0021]
As shown in FIG. 6, the rotation of the rod lower portion 55 relative to the rod upper portion 53 may be realized by a direct drive motor 81 having a large torque.
[0022]
The C arm 51 is held by the arm holding device 7 so as to be rotatable about three orthogonal axes. In FIG. 2, the overhead traveling type arm holding device 7 is shown, but it may be a floor-standing type. A traveling base 46 is provided on the traveling rails 43 and 45 of two orthogonal systems attached to the ceiling surface, and a suspension arm 47 is suspended from the traveling base 46 in a rotatable state as indicated by an arrow E. . By this rotation, the C-arm 51 can turn greatly. An arm holder 49 is connected to the suspension arm 47 in a rotatable state as indicated by an arrow A. By this rotation, the C arm 51 can be rotated and tilted with respect to the top / foot (CRA / CAU) of the subject. Further, the arm holder 49 holds the C-arm 51 in a state where it can travel along its curved shape as indicated by an arrow B. By this traveling, the C-arm 51 can rotate and tilt with respect to the left and right (RAO / LAO) of the subject. The C arm 51 can be held in an arbitrary posture by the rotation of these three rotation shafts. The posture of the C arm 51 can be detected by detecting the angles of the three rotation axes with the position sensor 17.
[0023]
The X-ray tube 3, the flat-type X-ray detector 5, the arm holding device 7, the X-ray diaphragm device 9, the bed 11, the rotation mechanism 13, the slide mechanism 15, and the position sensor 17 include the control units 103, 105, 107, 109, 111, 113, 115, and 117 are respectively driven and controlled. These control units 103, 105, 107, 109, 111, 113, 115, and 117 are connected to the system control unit 19 and the auto positioning control unit 39. In addition to the automatic positioning control unit 39, the system control unit 19 is connected to a display device 35, an operation console 37, and a position memory 41. Input, auto-positioning and image display functions are realized.
[0024]
The auto-positioning function means that the flat X-ray detector 5 is automatically rotated and slid according to the posture of the C-arm 51, and is arranged at an optimal position to avoid interference with the subject or the like. It is a convenient function for. The auto-positioning function is set so that the operator does not use the entire detection surface of the flat X-ray detector 5 and collects image data using a partial area within the detection surface. The flat X-ray detector 5 is automatically slid so that X-rays are perpendicularly incident on the center of the region (imaging range), and at the same time, in order to avoid unnecessary exposure, X-rays only in the imaging range. A function of realizing a control operation of adjusting the opening of the X-ray diaphragm device 9 so as to irradiate is also included. Data necessary for this automatic positioning is preset in the position memory 41.
[0025]
Furthermore, an image memory 21 is connected to the system control unit 19 in order to receive and hold original image data captured by the planar X-ray detector 5 via the imaging control unit 105. In order to perform various image processing on the original image data held in the image memory 21, an affine transformation unit 23, an edge enhancement unit 25, a gradation transformation unit 27, a subtraction unit 29, and a subject A reconstruction processing unit 31 for reconstructing three-dimensional image data based on a set of two-dimensional image data picked up from multiple directions around the three-dimensional image, and a three-dimensional image for performing three-dimensional image processing on the three-dimensional image data A processing unit 33 is provided under the system control unit 19.
[0026]
The operation of the X-ray diagnostic apparatus according to the present embodiment configured as described above will be described. First, the rotation operation of the flat X-ray detector 5 will be described.
(First mode)
As described above, when the clutch release button 59 provided on the handle 57 of the flat X-ray detector 5 is pressed, the electromagnetic clutch 71 is released and the detector 5 enters a rotation-free state. As a result, the operator can rotate the detector 5 at an arbitrary angle by holding the handle 57. When the direct drive motor 81 shown in FIG. 6 is employed, when the button 59 is pressed, the direct drive motor 81 enters a non-excited state, and the detector 5 enters a rotation-free state as in the case of releasing the clutch.
[0027]
(Second mode)
The detector 5 can also be rotated remotely by an operation console 37 disposed in an operation room adjacent to the imaging room in which the gantry part 1 is installed.
[0028]
(Third mode)
The third mode is a rotation and slide operation of the detector 5 by the auto positioning function. For example, when the operator inputs the examination site as the abdomen, the detector 5 rotates as necessary, and the long side of the detector 5 is set to a position parallel to the body axis of the subject. Thereby, in a leg imaging examination, a wide visual field can be secured for blood vessels extending in the body axis direction. However, in this position, the detector 5 may limit the tilt of the C-arm 51 toward the top or foot of the subject. Such a problem is alleviated by tilting the detector 5 obliquely with respect to the X-ray tube 3. In this case, since the X-ray tube 3 and the flat X-ray detector 5 do not face each other, the display image is distorted, which can be reduced by the oblique processing of the affine transformation unit 23. At this time, the X-ray diaphragm device is adapted in accordance with the orientation of the planar X-ray detector 5 with respect to the X-ray tube 3 so that the X-ray is irradiated only to the range of the detection surface of the planar X-ray detector 5. Nine apertures are automatically adjusted.
[0029]
Also, for example, when the operator inputs a part other than the abdomen as the examination part, the inclination angle (rotation angle) θ for RAO / LAO (patient right / left) and the inclination rotation angle for CRA / CAU (top / foot). Based on φ, the position of the detector 5 changes. For example, when the C-arm 51 is not excessively inclined at a rotation angle of 35 ° or less with respect to the CRA / CAU direction, the detector 5 rotates so that the long side of the detector 5 is substantially parallel to the body axis. Is done. However, when the C-arm 51 is inclined so much that it exceeds 35 ° with respect to the CRA / CAU direction, the short side of the detector 5 is substantially parallel to the body axis so that the detector 5 does not interfere with the subject. Is rotated 90 ° so that
[0030]
Further, in this apparatus, it is possible to collect image data using a part of the detection surface as shown by a dotted line in FIG. 4 without using the entire detection surface of the detector 5. In this case, since the X-rays from the X-ray tube 3 are incident obliquely with respect to the center of the part, the image is distorted. In order to solve this, as shown in FIG. 7, when only a part of the detection surface is designated for collecting image data, the X-ray from the X-ray tube 3 is perpendicular to the center of the part. The detector 5 is slid so as to be incident on. Instead of this slide, as shown in FIGS. 8 (a) and 8 (b), the rod 52 is attached at a position shifted from the center of the detector 5, and the same effect can be obtained by rotating it 90 °. It may be.
[0031]
Further, when the C-arm 51 is inclined in both directions of RAO / LAO and CRA / CAU, the detector is based on the angle formed by the straight line connecting the center of the detector 5 and the isocenter and the top plate surface of the bed 11. Rotate 5 For example, when the angle exceeds 35 °, the short side of the planar X-ray detector 5 is parallel to the plane passing through the isocenter and the center of the detector 5 and perpendicular to the bed 11. The long side is set to be perpendicular to the plane. When the orientation (for example, the top) of the patient in an arbitrary direction (for example, the top of the head) differs due to this rotation, the patient may be rotated by image processing so as to be directed to the specified direction.
[0032]
In this embodiment, the reconstruction processing unit 31 represents a three-dimensional structure inside the human body based on multi-directional image data repeatedly collected over 180 ° + α (α is a view angle) around the subject. Data can be reconstructed. Here, in order to reconstruct the three-dimensional image data inside the human body by the projection theorem, it is necessary that the entire width of the subject is always within the detection surface of the detector 5 during rotation. For this reason, at the time of three-dimensional image reconstruction, the detector 5 is set so that the short side is substantially parallel to the rotation axis of the C arm 51 when the detector 5 rotates around the subject. . As a result, a wide field of view is secured in the width direction of the subject, and the entire lateral width of the subject always fits on the detection surface of the detector 5 during rotation.
[0033]
At the time of this three-dimensional image reconstruction, imaging is repeated at intervals of, for example, 1 ° over a range of 180 ° + α while the C-arm 51 rotates at high speed. The multidirectional image data (projection data) is converted into a digital signal by the imaging control unit 105 and then stored in the image memory 21. Similarly, the image memory 21 stores in advance image data that has been captured with nothing being sandwiched between the X-ray tube 3 and the detector 5. When image data relating to the subject is accumulated in the image memory 21, subtraction processing is performed in the subtraction unit 29 with image data stored in advance. The difference data obtained by the subtraction is sent to the reconstruction processing unit 31 where the reconstructed reconstruction area is reconstructed. As an example of the reconstruction method, here, the filtered back projection method proposed by Feldkamp et al. Will explain, for example, an appropriate convolution filter such as Shepp & Logan or Ramachandran for multi-directional image data of 180 ° + α. multiply.
[0034]
Next, generally, reconstruction data is obtained by performing a back projection operation. Here, the reconstruction area is defined as a cylinder inscribed in the X-ray flux in all directions of the X-ray tube. The inside of the cylinder is discretized three-dimensionally with a length d at the center of the reconstruction area projected onto the width of one detection element of the detector, for example, and it is necessary to obtain a reconstruction image of discrete point data. However, although an example of the discrete interval is shown here, this may differ depending on the device or manufacturer, so basically, the discrete interval defined by the device may be used. The reconstructed three-dimensional image is displayed on the display device 35 after appropriate image processing such as volume rendering or surface rendering is performed by the three-dimensional image processing unit 33.
[0035]
Next, an operation at the time of stepping photographing effective for photographing a wide range from the abdomen to the lower limb will be described. In the stepping shooting, a cycle of shooting → slide of the bed 11 → stop is repeated. At this time, the detector 5 is set so that its long side is substantially parallel to the body axis.
[0036]
In stepping imaging, for example, the region from the stomach to the ankle is determined as an imaging region, and the number of steps and the imaging position are determined based on the length, the length of the long side of the detector 5, and the magnification of the X-ray optical system. At this time, since the number of steppings is inversely proportional to the length of the detector 5, the number of steppings can be reduced by using the long detector 5 as in the present embodiment. Next, fluoroscopy (imaging with a very small dose) is performed sequentially at the imaging position determined from the ankle direction to the stomach, and the imaging dose at that position is calculated based on the transmitted light at each position. Then, after injecting the contrast agent, the imaging is sequentially performed at the imaging positions determined from the stomach to the ankle in the reverse order of dose determination so as to track the flow.
[0037]
There is also a technique called stepping DSA. At this time, the dose is determined from the abdomen toward the ankle, and then imaging is sequentially performed at the imaging position determined from the ankle direction to the abdomen without injecting contrast medium (mask image imaging). Finally, after injecting the contrast agent, the imaging is sequentially performed at imaging positions determined from the stomach to the ankle so as to follow the flow. Then, by performing subtraction (DSA: Digital Subtraction Angiography) on the contrast image and the mask image taken at the same position, it is possible to obtain an image in which only the blood vessels are emphasized by eliminating the background of bones and soft tissues.
[0038]
As described above, according to this embodiment, the restriction on the movement of the C-arm is remarkably reduced. In addition, the field of view can be expanded.
[0039]
The present invention is not limited to the embodiments described above, and can be implemented with various modifications.
[0040]
【The invention's effect】
The X-ray detector of the present invention is planar and thinner than that using a conventional image intensifier. Moreover, the detection surface is substantially rectangular and can be further rotated. Thereby, the X-ray detector can be rotated as necessary to avoid interference with the support mechanism and the subject. Further, if the X-ray detector is rotated and the long side of the detection surface is set in a desired direction, a large field of view can be secured in that direction. Furthermore, if the long side of the detection surface is aligned with the width direction of the subject, the entire width of the subject can be accommodated in the field of view, so the application range of the three-dimensional image reconstruction is expanded without being restricted only by conventional blood vessels. be able to. In stepping imaging, the number of steps can be reduced by aligning the long side of the X-ray detector with the body axis direction of the subject.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an X-ray diagnostic apparatus according to an embodiment of the present invention.
FIG. 2 is an external view of a gantry portion of FIG.
3 is a perspective view of the planar X-ray detector in FIG. 1. FIG.
4 is a plan view of the planar X-ray detector of FIG. 1. FIG.
5 is an internal structural diagram of a connecting portion between the rod upper portion and the rod lower portion of FIG. 4;
6 is another internal structural diagram of a connecting portion between the rod upper portion and the rod lower portion of FIG. 4;
7 is a view showing an example of use of the slide mechanism of FIG.
FIG. 8 is a view showing an alternative example of the slide mechanism of FIG. 1;
[Explanation of symbols]
1 ... Gantry,
3 ... X-ray tube,
5 ... Planar X-ray detector,
7 ... Arm holding device,
9 ... X-ray diaphragm device,
11 ... Bed,
13 ... Rotation mechanism,
15 ... slide mechanism,
17 ... Position sensor,
19 ... System control unit,
21 ... Image memory,
23 ... Affine transformation unit,
25. Edge emphasis part,
27: gradation conversion unit,
29 ... Subtraction part,
31 ... Reconfiguration processing unit,
33 ... 3D image processing unit,
35 ... display device,
37 ... console,
39: Auto-positioning control unit,
41 ... Position memory,
43 ... ceiling rail,
45 ... ceiling rail,
47 ... Suspended arm,
49 ... C arm holder,
51 ... C-arm,
52 ... Rod,
53 ... the top of the rod,
55 ... Bottom of rod,
57 ... handle,
59 ... Clutch release button,
61 ... Frame,
63 ... detection surface,
65 ... bearings,
67 ... Stepping motor,
69 ... Drive gear,
71 ... Electromagnetic clutch,
73 ... Rotary encoder,
75 ... driven gear,
77 ... Slip ring,
79 ... Cable,
81: Direct drive motor,
103 ... X-ray control unit,
105 ... Imaging control unit,
107 ... arm holding device control unit,
109 ... Aperture control unit,
111 ... Sleeper control unit,
113 ... Rotation control unit,
115 ... slide control unit,
117: Sensor control unit;

Claims (7)

An X-ray tube;
A planar X-ray detector having a rectangular detection surface with a long side and a short side ;
An arm that supports the X-ray tube and the X-ray detector so as to face each other with a subject interposed therebetween;
A holding device that holds the arm rotatably about at least two axes;
A rotation mechanism that rotatably supports the X-ray detector around a rotation axis substantially perpendicular to the detection surface;
An X-ray diagnostic apparatus comprising: a control unit that controls the rotation mechanism so that either the long side or the short side of the X-ray detector is substantially parallel to the body axis of the subject. . The detection surface of the planar X-ray detector, X-rays diagnostic apparatus according to claim 1, wherein the ratio of long side against short side, characterized in that 1.3 or more. The detection surface of the planar X-ray detector, X-rays diagnostic apparatus according to claim 1, wherein the ratio of long side against short side, characterized in that not less than 1.5. X-ray diagnostic apparatus according to claim 1, characterized in that it is capable of generating image data corresponding to an arbitrary portion of the detection surface of the flat X-ray detector. The X-ray diagnosis apparatus according to claim 4, wherein an X-ray aperture changes according to a position and a range of a part where the image data is generated. The planar X-ray detector, X-rays diagnostic apparatus according to claim 1, characterized in that it is slidably supported parallel to the long sides orientation of the detected face. The planar X-ray detector, X-rays diagnostic apparatus according to claim 1, characterized in that it is rotatably supported at a position offset from the center of the detection surface.

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