JP2004344540A - X-ray diagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide precise CT values without being effected by fluctuation in irradiation X-ray intensity in X-ray diagnostic equipment imaging a CT image using a conical X-ray beam. <P>SOLUTION: This X-ray diagnostic equipment is formed by mounting an X-ray tube 21, an X-ray diaphragm device 22 and a transmissive dosimeter 23 on one end of a C-type arm 25 and an FPD (Flat Panel Detector) 24 on the other end respectively, rotates the C-type arm 25 along its arc to rotate the X-ray tube 21 and the FPD 24 or others around a subject 10, allows a data collection device 35 to collect data obtained from the FPD 24 in respective angles during the rotation, allows the data collection device 35 to collect data of the irradiation X-ray intensity obtained by the transmissive dosimeter 23, allows an image reconfiguration device 34 to reconfigure the CT image with the precise CT values from these data, and displays the CT image on an image monitor device 31. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a medical X-ray diagnostic apparatus, and more particularly to an X-ray diagnostic apparatus having a CT image capturing function using a cone-shaped X-ray beam.
[0002]
[Prior art]
An X-ray fluoroscope as a medical X-ray diagnostic apparatus that irradiates a subject (subject) with an X-ray beam in a cone shape and receives an X-ray beam transmitted through the subject with a planar X-ray detector And X-ray angiography devices are known. On the other hand, the X-ray CT apparatus irradiates the subject with an X-ray beam that spreads in a fan shape in a plane, and receives the X-ray beam irradiated on the subject with a linear X-ray detector.
[0003]
In an X-ray fluoroscope or X-ray angiography system using a cone-shaped X-ray beam, an X-ray irradiator and a detector are attached to a C-arm and rotated to collect data from each direction and reconstruct an image. Conventionally, processing is performed to obtain a CT image.
[0004]
[Problems to be solved by the invention]
However, when a CT image is taken with a conventional X-ray diagnostic apparatus using a cone-shaped X-ray beam, accurate data cannot be collected due to the influence of X-ray fluctuations during scanning (rotation), and a reconstructed image is There was a problem that it would be incorrect.
[0005]
This is because it was difficult to attach a correction detector for detecting and correcting X-ray fluctuations. That is, in the case of an X-ray CT apparatus, the X-ray beam emitted from the X-ray tube is narrowed down in a plane so as to spread in a fan shape. A detector can be provided. However, when irradiating a cone-shaped X-ray beam, the X-ray beam from the X-ray tube is irradiated as it is without being narrowed down. Therefore, it is not possible to use an X-ray beam that is narrowed down and blocked. is there.
[0006]
In view of the above, the present invention captures X-ray fluctuations using a correction detector even when the X-ray beam is not focused, thereby correcting the fluctuations, obtaining accurate data, and obtaining an accurate X-ray CT image. It is an object of the present invention to provide an X-ray diagnostic apparatus improved as described above.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the X-ray diagnostic apparatus according to the present invention, an X-ray irradiator that irradiates a cone-shaped X-ray beam to a subject, and an X-ray irradiator that irradiates the subject from the X-ray irradiator. Transmission dosimeter mounted to transmit a cone-shaped X-ray beam, a planar X-ray detector for receiving a cone-shaped X-ray beam transmitted through a subject, these X-ray irradiators, and transmission-type dosimeters And a rotation device for integrally rotating the X-ray detector around the subject by at least 180 °, a data collection device for collecting data from the X-ray detector and the transmission dosimeter for each angle of this rotation, It is characterized by comprising an image reconstruction processing device for performing image reconstruction processing from collected data, and an image display device for displaying a reconstructed image.
[0008]
Since the cone-shaped X-ray emitted from the X-ray irradiator toward the subject is transmitted through the transmission dosimeter and directed toward the subject, the X-ray irradiated onto the subject by the transmission dosimeter is used. The dose of the line is measured. Then, the irradiation dose is measured for each rotation angle and collected as data, so that even if the irradiation dose fluctuates, it can be corrected. As a result, the CT value of the reconstructed image can be made accurate. The dosimeter for measuring the irradiation dose is of a transmission type, and measures the dose of X-rays actually applied to the subject. Therefore, it is not necessary to provide a detector for correction so as to detect X-rays that are not irradiated on the subject, which is stopped down by the stop device, and even when irradiating a cone-shaped X-ray beam with almost no stop, It is possible to measure the dose of X-rays radiated to the subject and correct the fluctuation.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a subject 10 is lying on a bed of a bed, and an X-ray tube 21 and an FPD 24 are arranged to face each other so as to sandwich the subject 10 therebetween. Here, the FPD is a flat panel detector, that is, a flat panel X-ray detector, and is a two-dimensional X-ray detector made of a semiconductor that directly converts incident X-rays into an electric signal. Note that a combination of an X-ray image intensifier and a CCD camera can be used instead of the FPD. An X-ray aperture device 22 is attached to the X-ray tube 21 so that a cone-shaped X-ray beam having a predetermined spread can be emitted to the subject 10. Further, a transmission type dosimeter 23 is attached, and the subject 10 is irradiated with a cone-shaped X-ray beam through the transmission type dosimeter 23.
[0010]
The X-ray tube 10, the X-ray aperture device 22, and the transmission dosimeter 23 are held at one end of a C-arm 25, and the FPD 24 is held at the other end. The C-arm 25 is held by a holding device 26, which is attached to a stand 27. The holding device 26 allows the C-arm 25 to rotate relative to the stand 27 by at least 180 ° in the direction of the arc of the C-arm 25, as shown by the arrow, or to rotate the arc about the horizontal axis in the radial direction. It can be moved and rotated in any direction, such as front-back and up-down linear movement. A power supply for supplying high-voltage power to the X-ray tube 21 is provided in the stand 27.
[0011]
In this example, an image reconstructing device 34, a data collecting device 35, a control device 36, and the like are housed in a cabinet 32, and an operation panel provided with switches for setting X-ray conditions and the like is provided on a side surface thereof. 33 are attached. Further, an image monitor device 31 is placed on the cabinet 32. The cabinet 32 and the stand 27 are connected by a cable, and a command is given to the holding device 26 to drive the C-arm 25 to rotate the C-arm 25 at least 180 ° along the arc. Thereby, the X-ray tube 21, the FPD 24 and the like are rotated around the subject 10. During this rotation, a cone-shaped X-ray beam is irradiated from the X-ray tube 21 through the X-ray aperture device 22 and the transmission type dosimeter 23 toward the subject 10, and the X-ray beam transmitted through the subject 10 is transmitted to the FPD 24. Incident on.
[0012]
Thus, data is obtained from the transmission dosimeter 23 and the FPD 24 for each rotation angle, and these data are collected by the data collection device 35 for each rotation angle. The collected data is subjected to image reconstruction processing by the image reconstruction device 34, and the reconstructed CT image is displayed on the image monitor device 31.
[0013]
The transmission dosimeter 23 is configured, for example, as shown in FIG. A transparent conductive film is formed on one surface of each of the two transparent synthetic resin plates 41 by etching or the like, and is held by the holding plates 44, 44 and the like so that the conductive films face each other. A high voltage is applied to both the conductive films, and one transparent conductive film is used as the transparent collector electrode 42 and the other transparent conductive film is used as the transparent high-voltage electrode 43 to form an ionization chamber X-ray detector. When the X-ray beam passes through the two transparent synthetic resin plates 41, for example, from above to below in the figure (or in the opposite direction), the X-ray intensity is detected by the principle of the ionization chamber X-ray detector. be able to.
[0014]
Here, the CT image is an image in which each pixel value is represented by a CT value, and the CT value is defined by the following equation (1).
CT value = 1000 (μ-μw) / μw (1)
μ is the linear absorption coefficient of each voxel in the image, and μw is the linear absorption coefficient of water.
[0015]
If an X-ray beam is transmitted through an object having a linear absorption coefficient μ, the transmission length is L, the incident X-ray intensity is Io, and the transmitted X-ray intensity is I, the relationship between I and Io is as follows. 2) It is expressed by the equation.
I = Io exp (−μL) (2)
Therefore,
μ = ln (Io / I) / L (3)
It becomes.
[0016]
Assuming that Io does not fluctuate, by obtaining this in advance, an accurate μ can be obtained only by detecting I with the FPD 24. However, irradiation is performed from Io, that is, the X-ray tube 21 toward the subject 10. If the intensity of the X-rays fluctuates, the value of μ obtained by equation (3) will be inaccurate. Here, since this Io is detected by the transmission dosimeter 23, an accurate value of μ can be obtained by correcting the reference Io with the variation or using the detected Io, A CT image can be obtained.
[0017]
Since the transparent synthetic resin plates 41 and 41 and the transparent electrodes 42 and 43 are used in the transmission type dosimeter 23, light is transmitted therethrough. Therefore, a light source having a focal point is arranged at the same position as the X-ray focal point, and light from the light source is irradiated to the subject 10 through the X-ray aperture device 22 and the transmission dosimeter 23, and the light is emitted. May be configured to represent an X-ray irradiation field.
[0018]
In addition, specific configurations and the like can be variously changed without departing from the spirit of the present invention. For example, the X-ray irradiator that irradiates the subject 10 with an X-ray beam is not limited to the illustrated one, and an X-ray irradiator and a detector such as an FPD 24 that detects X-rays transmitted through the subject 10 may be used. The rotating device that rotates the subject 10 around the subject 10 is not limited to the one that rotates the C-shaped arm 25 as illustrated. An X-ray irradiator and a detector for detecting X-rays transmitted through the subject 10 may be attached to a circular rotating frame, and the rotating frame may be rotated to rotate these X-ray irradiators. Further, the transmission type dosimeter 23 is configured as shown in FIG. 2, but other configurations are also possible. For example, the transparent collector electrode 42 and the transparent high-voltage electrode 43 are provided on almost the entire surface of the transparent synthetic resin plates 41, 41 so that the whole of the transmitting cone-shaped X-ray beam is transmitted. Can be formed as having a relatively small area only near the center of the transmitting cone-shaped X-ray beam.
[0019]
【The invention's effect】
As described above, according to the X-ray diagnostic apparatus of the present invention, a subject is irradiated with a cone-shaped X-ray beam, and the X-ray beam transmitted through the subject is detected by a planar X-ray detector. When collecting CT data and reconstructing the data to obtain a CT image, the X-ray intensity of the irradiated X-ray intensity is irradiated by irradiating the subject with an X-ray beam after passing through a transmission dosimeter. An accurate CT value can be obtained by capturing the fluctuation.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a sectional view showing the transmission dosimeter of the embodiment in detail.
[Explanation of symbols]
10 Examinee 21 X-ray tube 22 X-ray aperture device 23 Transmission dosimeter 24 FPD
25 C-type arm 26 Holding device 27 Stand 31 Image monitor device 32 Cabinet 33 Operation panel 34 Image reconstruction device 35 Data collection device 36 Control device 41 Transparent synthetic resin plate 42 Transparent collector electrode 43 Transparent high voltage electrode 44 Holding plate

Claims (1)

An X-ray irradiator that irradiates a cone-shaped X-ray beam toward a subject; and a transmission dosimeter attached so that the cone-shaped X-ray beam that is radiated from the X-ray irradiator toward the subject is transmitted. A planar X-ray detector for receiving a cone-shaped X-ray beam transmitted through the subject, and the X-ray irradiator, transmission dosimeter and X-ray detector integrally rotated at least 180 ° around the subject A rotation device for performing the rotation, a data collection device for collecting data from the X-ray detector and the transmission dosimeter for each angle of the rotation, an image reconstruction processing device for performing an image reconstruction process from the collected data, An X-ray diagnostic apparatus, comprising: an image display device configured to display a configured image.

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