JP2007215808A - Medical tomographic imaging equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a conventional X-ray CT apparatus has no mechanism for detecting the mounting/non-mounting of an extension top board, the movable range of the top board is set as a prerequisite for mounting the extension top board as standard and, if the extension top board is unmounted, the movable range (namely, an image-pickup range) of the top board often cannot be secured sufficiently. <P>SOLUTION: This medical tomographic imaging equipment is provided with a means for optically detecting the mounting/non-mounting of the extension top board 3 and a means for automatically changing the movable range of the top board 2 corresponding to the detected information. Even if the extension top board 3 is unmounted, this constitution can sufficiently secure the movable range (namely, the image-pickup range) of the top board 2. The detecting means is not an electrical one, so that an X-ray transmission part has no wiring of metal components to provide a tomographic image with a little artifact. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a medical tomographic imaging apparatus such as an X-ray CT apparatus or an MRI apparatus, and more particularly, to a bed top plate that moves a subject to a gantry unit.

  An X-ray CT apparatus is taken as an example of a medical tomographic imaging apparatus and will be described below. The X-ray CT apparatus emits X-rays from the X-ray tube while the X-ray tube and the X-ray detector rotate in the circumferential direction around the body axis of the subject placed on the top plate, An X-ray dose transmitted through the subject is detected by a plurality of detectors arranged in a circular arrangement facing each other, and the signal is computer processed to form an image. The rotation speed is 1 second or less in a full scan (360 degrees) of a high-class machine class. During this scan, for example, in the case of an abdominal slice, the subject is irradiated with an X-ray dose of 120 kV and about 200 mAs as an X-ray condition.

  The X-ray beam is narrowed in a fan shape by a collimator at the exit of the X-ray tube, partially hits the subject and scattered, and the transmitted X-rays enter a plurality of detectors and are processed as image information. High-speed continuous shooting in spiral scan mode (which moves the top plate into the gantry at a constant speed and continuously rotates the X-ray tube and detector, also called the helical scan mode) captures the movement of the top plate. Since a wide range can be photographed in a short time because it is performed inside, it is popular as the mainstream of CT. The output signal from the detector is stored in the memory via the data collection unit, and data processing is performed by the host CPU, the image reconstruction device, the scan control unit, etc., which are the core of the system control, and the image is reconstructed. Displayed on the monitor.

  Recently, it has become possible to increase the image reconstruction processing speed more than 10 times faster than the conventional method, and CT fluoroscopy has a function capable of displaying an image like a moving image at a speed of several frames per second in parallel during scanning. Has been put into practical use and can be continuously observed in real time like conventional X-ray fluoroscopy. In order to obtain a tomographic image by slicing the diagnosis area of the subject as described above, the subject placed on the top is raised to the height of the rotation axis in the gantry and diagnosed to the slice position at the center of rotation. The part (imaging part) must be moved. Then, at the time of high-speed continuous imaging in the spiral scan mode, the subject placed on the top plate is moved at a predetermined speed to image a wide range in a short time.

  When aligning the imaging region of the subject, first, align with the first projector in front of the gantry, then move the top plate by a predetermined distance, and use the second projector to locate the imaging target region. Confirmation is in progress. When the gantry is tilted, the first projector and the second projector are configured to tilt similarly. (For example, see Patent Document 1)

In such an X-ray CT apparatus, there are a case where the subject is photographed by attaching the extended top plate to the top plate, and a case where the subject is photographed without attaching the extended top plate. In these two cases, it is necessary to change the setting of the movable range of the top plate movement in accordance with the length of the extension top plate to be mounted. However, when the presence or absence of the extension top plate is detected by an electrical sensor such as a microswitch, the top plate includes a metal part, and an artifact (false image) occurs in the tomographic image. Therefore, the conventional X-ray CT apparatus does not have a mechanism for detecting whether or not the extension top plate is mounted, and the setting of the movable range of the top plate is based on the case where the extension top plate is mounted.
JP 7-124148 A

  In the above X-ray CT apparatus, it is necessary to manually operate the setting of the movable range of the top plate movement in accordance with whether or not the extension top plate is attached. Forgetting the operation occurs, and the extension top plate is not attached. In this case, the movable range of the top board (that is, the imaging range) may not be secured sufficiently.

  In order to solve the above-described problems, the present invention provides a medical tomographic imaging apparatus for capturing a tomographic image by moving a subject placed on a top plate that moves horizontally above a bed into a gantry. There are provided means for optically detecting whether or not the extension top plate is attached to the head and means for automatically switching the movable range of the top plate in accordance with the detected information. Therefore, even when the extended top plate is not attached, it is possible to sufficiently secure the movable range (that is, the imaging range) of the top plate.

  According to the present invention, the presence or absence of an extension top plate is detected optically rather than electrically, and it is not necessary to dispose metal parts on the top plate, so that a tomographic image with less artifacts can be obtained. The movable range of the top plate (that is, the photographing range) is always automatically set to an optimum value in accordance with whether or not the extension top plate is attached, and there is an effect that the efficiency of diagnosis is improved.

The means for optically detecting the presence or absence of the extension top plate is composed of a plastic optical cable in order to suppress the occurrence of artifacts in the tomographic image as much as possible. An optical cable is installed so that the light emitted from the light source is incident on the receiver when the extended top is attached, and the light emitted from the light source is not incident on the receiver when the extended top is not attached. Detect the presence or absence of the extended top.
The light source and the light receiving unit made of metal parts are arranged separately from the top plate and the gantry in order to reduce artifacts in the tomographic image.
In order to prevent damage to the optical cable that moves as the top plate moves, an optical cable processing unit and a cable storage unit are provided.

  The light emitted from the light source and the light that can be detected by the light receiver are near-infrared light that does not normally exist in the room where the medical tomographic imaging apparatus is installed. , Unaffected by light present in the room.

  Examples of the present invention will be described below. FIG. 1 is a diagram schematically showing the configuration of the present invention, in which (a) is a top view and (b) is a side view thereof. In FIG. 1, reference numeral 1 denotes a bed of an X-ray CT apparatus, and reference numeral 2 denotes a top plate which is disposed on the bed 1 and on which a subject is placed, and can move on the bed 1. Reference numeral 3 denotes an extended top plate that is inserted into the top plate 2 when the top plate 2 needs to be extended, and the mounting position is accurately determined by a positioning pin. An optical cable 4 is made of plastic, and light from a light source is introduced from one end thereof, and a part of the light cable is attached inside the top plate 2. An optical cable 5 is made of plastic. Light emitted from one end of the optical cable is detected by a light receiver, and a part of the optical cable is attached to the top plate 2. Reference numeral 6 denotes an optical cable, which is made of plastic and is provided inside the extended top 3. Reference numeral 7 denotes an optical cable processing unit that always pulls the optical cable 4 and the optical cable 5 with a constant tension, eliminates slack that occurs when the top plate 2 moves, protects the optical cable from damage, and functions so as not to hinder the operation of the operator. A cable storage unit 8 stores the optical cable 4 and the optical cable 5 that come in and out of the optical cable processing unit 7 as the top plate 2 moves. The cable storage unit 8 is a box having a space inside, and the optical cable 4 and the optical cable 5 are suspended and stored in the box under its own weight. Reference numeral 9 denotes an extension top plate attachment / detachment detection unit, which has a function of detecting attachment / detachment of the extension top plate 3. The end face of the optical cable 4 and the one end face of the optical cable 6 on the insertion and facing surfaces of the top plate 2 and the extended top plate 3 are both polished and coaxially facing each other (when the extension top plate 3 is attached), and the end surface of the optical cable 5 and the optical cable The other end face of 6 is ground together and coaxially opposed and close (when the extension top plate 3 is attached).

  FIG. 2 is a diagram showing a configuration for detecting attachment / detachment (presence / absence of attachment) of the extension top 3. In FIG. 2, the extended top plate attachment / detachment detection unit 9 includes a light source 91, a light introduction unit 92, a light collection unit 93, a light receiver 94, an output circuit 95, and the like. The light source 91 is composed of a light emitting diode or the like, and the light introducing unit 92 is composed of a lens or the like, and condenses the light emitted from the light source 91 and efficiently introduces it to one end of the optical cable 4. When the extension top plate 3 is mounted, the distance d between the end face of the optical cable 6 and the end faces of the optical cable 4 and the optical cable 5 becomes zero, and the light introduced into the optical cable 4 passes through the optical cable 6 although some loss occurs. However, when the extended top 3 is not attached, the light introduced into the optical cable 4 is not transmitted after the optical cable 6. The condensing unit 93 is composed of a lens or the like, condenses light emitted from one end of the optical cable 5 at an angle determined by its numerical aperture, and introduces the light into a light receiver 94 composed of a photodiode or the like. The output circuit 95 includes an amplifier circuit that amplifies the electric signal from the light receiver 94 and a comparison circuit that compares the amplified signal with a predetermined reference value. The output signal corresponds to whether or not the extension top plate is attached. Has two levels.

  FIG. 3 is a diagram showing a block configuration of the X-ray CT apparatus. In FIG. 3, the gantry / bed control device 10 receives an output signal of the extension top plate attachment / detachment detection unit 9 indicating whether or not the extension top plate 3 is attached, and transmits it to the host CPU 11, and the extension stored in the storage device 12 in advance. Of the movable range of the top plate 2 determined according to whether or not the top plate 3 is attached, the corresponding movable range is received from the host CPU 11, and the bed 1 is placed on the bed 1 so that the top plate 2 moves within the movable range. A movement control signal for the plate 2 is transmitted. The bed 1 moves the top plate 2 according to the movement control signal of the top plate 2. The gantry 20 is provided with an X-ray tube 21 and a plurality of detectors 22 arranged opposite to the X-ray tube 21, and a subject placed on the top 2 or the top 2 and the extended top 3 is placed in the gantry 20. The X-ray tube 21 and the detector 22 are rotated around the body axis of the subject at the diagnosis site (imaging site), and the X-ray tube 21 emits X-rays while rotating in the circumferential direction. A tomographic image is formed by detecting the X-ray dose that has passed through the detector 22 and processing the signal with a computer.

Since the present invention has the above configuration, when the extension top plate 3 is not attached, the light emitted from the light source 91 passes through the light introducing portion 92 and is introduced into one end of the optical cable 4 and emitted from the other end. However, since there is no end of the optical cable 6 in the vicinity, it is not transmitted to the optical cable 6, the optical cable 5, the condensing unit 93, and the light receiver 94, and the output signal of the output circuit 95 is at a level where the extension top plate 3 is not attached. . The gantry bed control device 10 receives an output signal indicating that the extension top plate 3 is not attached and transmits it to the host CPU 11, and when the extension top plate 3 stored in advance in the storage device 12 is not attached, an appropriate top plate 2. Is transmitted from the host CPU 11, and a movement control signal for the top plate 2 is transmitted to the bed 1 so that the top plate 2 moves within the movable range. The bed 1 moves the top plate 2 according to the movement control signal of the top plate 2.
When the extension top plate 3 is mounted, the light emitted from the light source 91 passes through the light introducing portion 92 and is introduced into one end of the optical cable 4 and emitted from the other end, and enters one end of the adjacent optical cable 6. , Is transmitted to one end of the optical cable 5 that is closer to the other end of the optical cable 6, is radiated from the other end of the optical cable 5, is collected by the light collecting unit 93, and the output signal of the output circuit 95 is extended to the sky. It becomes the level with mounting of the plate 3. The gantry / bed control device 10 receives an output signal indicating that the extension top 3 is attached and transmits it to the host CPU 11, and when the extension top 3 stored in the storage device 12 is attached in advance, the appropriate top 2 Is transmitted from the host CPU 11, and a movement control signal for the top plate 2 is transmitted to the bed 1 so that the top plate 2 moves within the movable range. The bed 1 moves the top plate 2 according to the movement control signal of the top plate 2.

In the embodiments shown in FIGS. 1, 2 and 3, the X-ray CT apparatus is described as an example. However, the present invention can also be applied to an MRI apparatus, and the apparatus is not limited to the illustrated examples.
Further, in the illustrated example, the extended top plate attachment / detachment detection unit 9 is disposed in the bed 1 (fixed portion), but the extended top plate attachment / detachment detection unit 9 is disposed in the top plate 2 (moving unit). As a result, the optical cable processing unit 7 and the cable storage unit 8 become unnecessary. In this case, the extended top plate attachment / detachment detection unit 9 made of a metallic member is always disposed away from the gantry 20 even when the top plate 2 moves in the maximum movement range, and an image with little artifact is obtained. It is done.
In the illustrated example, the presence or absence of the extension top plate 3 is detected based on whether three optical cables are used and three of them close the light transmission loop. However, the optical cable 4 and the optical cable 5 are connected to the extension top plate 3. When the light emitted from the optical cable 4 is reflected by the extended top plate 3 and enters the optical cable 5, the extended top plate 3 is installed, and the reflected light does not enter the optical cable 5. Can detect the presence or absence of wearing.
As described above, the optical cable can have various configurations, and the present invention includes these modifications.

  The present invention relates to a medical tomographic imaging apparatus such as an X-ray CT apparatus or an MRI apparatus, and more particularly, to a bed top plate that moves a subject to a gantry unit.

The figure which shows the structure of this invention roughly Configuration diagram for detecting the attachment / detachment of the extension top plate The figure which shows the block configuration of the X-ray CT apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bed 2 Top plate 3 Extension top plate 4 Optical cable 5 Optical cable 6 Optical cable 7 Optical cable processing part 8 Cable storage part 9 Extension top plate attachment / detachment detection part 10 Gantry bed control apparatus 11 Host CPU
DESCRIPTION OF SYMBOLS 12 Memory | storage device 20 Gantry 21 X-ray tube 22 Detector 91 Light source 92 Light introduction part 93 Condensing part 94 Light receiver 95 Output circuit

Claims (3)

  In a medical tomographic imaging apparatus for taking a tomographic image by moving a subject placed on a top plate that moves horizontally at the top of the bed into the gantry, whether or not the extension top plate is attached to the top plate is metal A medical tomographic imaging apparatus comprising: means for detecting with a system composed of non-members; and means for automatically switching the movable range of the top plate in response to the detected information.   2. The medical tomographic imaging apparatus according to claim 1, wherein the means for detecting in the system composed of a non-metallic member is an optically detecting means.   3. The medical tomographic imaging apparatus according to claim 2, wherein the optical detection means is constituted by an optical cable.

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