JP2008023015A - Radiation positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of clearly projecting a mark by which the range and position of a lesion on a subject can be visually recognized on a body surface. <P>SOLUTION: The radiation positioning device is provided with a radiation source for radiating radiation to the subject, an image intensifier for forming images inside the subject from the radiation transmitted through the subject, a wire collimator provided with a plurality of wires and interposed between the radiation source and the image intensifier for projecting the line shadows of the wires to the images inside the subject, and a laser marker means for changing an irradiation direction on the basis of the position relation of the radiation source and the respective wires and radiating a laser beam imitating the shape of the wire collimator. By the laser beam by the laser marker, the shape of the wire collimator is projected to the surface of the subject mounted on a bed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an X-ray positioning apparatus that simulates and determines the radiation exposure direction and irradiation field prior to radiotherapy, and more particularly to a technique for marking the position and range of an affected area on the body surface of a subject.

  Conventionally, radiation treatment aimed at the treatment has been widely performed by exposing radiation to an affected area such as cancer or tumor, thereby destroying tissue cells of the affected area or preventing division. In this radiotherapy, it is important to accurately expose the affected area with radiation in order to minimize damage to normal tissues around the affected area and to effectively expose the affected area to radiation.

  Therefore, prior to radiation therapy, the radiation exposure direction and field are determined by simulation. An X-ray positioning device is used for this simulation and determination. The X-ray positioning apparatus includes an X-ray source that irradiates X-rays and an image intensifier that forms a visible light image in the subject from the X-rays transmitted through the subject. The visible light image is a perspective image in which a structure in a range through which X-rays are transmitted is projected. This X-ray positioning apparatus emits radiation that is weaker than that of a radiotherapy apparatus, observes the inside of a subject based on a fluoroscopic image, identifies an affected area, and determines the radiation exposure direction and irradiation field. The determined exposure direction and irradiation field are used for controlling the radiotherapy apparatus.

  Further, the X-ray positioning device includes a wire collimator so as to be interposed between the X-ray source and the subject. The wire collimator is arranged in a cross-beam shape, and the opening degree is adjusted so as to surround the affected area. The line shadow of the wire collimator is projected onto the fluoroscopic image in the subject by X-rays. The approximate position and range of the affected area can be visually recognized on the fluoroscopic image by the projected line collimator.

  Further, a light source for irradiating visible light imitating the X-ray source is disposed on the X-ray source side of the wire collimator. The visible light emitted from this light source imitates the radiation direction of the radiation emitted from the radiation source. By irradiating visible light from the light source, the line shadow of the wire collimator is projected onto the body surface of the subject. The approximate position and range of the affected part can be visually recognized on the body surface of the subject by the line shadow of the wire collimator on the body surface (see, for example, “Patent Document 1”).

JP 07-116153 A

  Usually, the wire shadow of the wire collimator formed on the body surface by being illuminated with a light source is marked by being traced with a magic or the like by a doctor or an engineer. However, the line shadow has a certain width due to blurring of its outline due to diffraction or scattering of visible light that illuminates the wire collimator, or external light. For this reason, the doctor or engineer may be at a loss as to where to actually trace the wide line shadow.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for clearly projecting on the body surface a mark that can visually recognize the range and position of the affected area on the subject. is there.

  An invention according to claim 1 for solving the above-mentioned problems includes: an X-ray source that emits X-rays to a subject; and an image intensifier that forms an in-subject image from the X-rays transmitted through the subject. A wire collimator that has a plurality of wires and that projects between the X-ray source and the image intensifier to project a shadow of the wire on the in-vivo image; the X-ray source; A laser marker unit that changes the irradiation direction based on the positional relationship with the wire and irradiates a laser beam imitating the shape of the wire collimator, and the subject placed on the bed by the laser beam from the laser marker unit The shape of the wire collimator is projected on the surface.

  The laser marker means may include a laser marker that irradiates laser light, and a reflector that changes the direction of laser light irradiation by changing the orientation angle based on the positional relationship between the X-ray source and each wire. Good (corresponding to the invention of claim 2).

  The laser marker means may irradiate the laser beam so that the irradiation axis of the laser beam passes through the focal point of the X-ray (corresponding to the invention according to claim 3).

  The laser marker means changes a direction angle based on a positional relationship between the laser marker for irradiating a laser beam, a reflecting plate for changing the irradiation direction of the laser beam, the X-ray source and the wire collimator, and predetermined in a predetermined direction. And a reflector that changes the irradiation direction of the laser light by moving the distance (corresponding to the invention of claim 4).

  You may make it further provide the bed which interposes between the said X-ray source and the said wire collimator, and mounts a test object (equivalent to the invention of Claim 5).

  In the present invention, a laser marker for irradiating the body surface with a laser is provided, and by irradiating the laser in the direction of the wire collimator, a projected image when the line shadow of the wire collimator is projected on the body surface is marked. I made it. Therefore, a projected image is clearly depicted on the body surface, and marking can be performed easily and accurately by a doctor or an engineer. In addition, this further imparts reliability to the mark indicating the shape and position of the affected area.

  FIG. 1 is a schematic diagram illustrating a configuration example of an X-ray positioning apparatus according to the present embodiment. The X-ray positioning apparatus 1 determines the X-ray exposure direction and irradiation field by simulating prior to radiation therapy.

  This X-ray positioning apparatus 1 includes an X-ray source apparatus 2 that emits X-rays, an image intensifier 3 that is disposed to face the X-ray source apparatus 2, and a celestial object on which a subject P is placed. A plate 8 is provided.

  The X-ray positioning apparatus 1 has a structure in which the fixed base 4 is fixed to the apparatus installation surface, the rotary base 5 is supported by the fixed base 4 and arranged in a hollow space, and the arms 6 and 7 are installed on the rotary base 5. An X-ray source device 2 and an image intensifier 3 are arranged in this structure.

  The X-ray source device 2 is disposed at the distal end of the arm 6, and the image intensifier 3 is disposed at the distal end of the arm 7. The top plate 8 is disposed between the X-ray source device 2 and the image intensifier 3 and is movable in the body axis direction of the subject P.

  The rotating gantry 5 is supported on the fixed gantry 4 via a rotating shaft 10 and can rotate around the rotating shaft 10 (in the direction of arrow A in FIG. 1). The X-ray source device 2 and the image intensifier 3 are rotated around the axis of the rotation shaft 10 by the rotation of the rotating gantry 5 to enable X-ray irradiation at different angles.

  The arms 6 and 7 hold the position by gripping the rail installed along the rotary mount 5 at the root portion, and can slide along the rotary mount 5 (in the directions of arrows B and C in the figure). It has become. The radiation head 2 and the image intensifier 3 can approach or leave the subject P placed on the top 8 by sliding the arms 6 and 7.

  The arms 6 and 7 are provided with position detecting means such as a potentiometer, and specify the positions of the radiation head 2 and the image intensifier 3. By specifying the position of the X-ray source device 2, the X-ray source 21 described later and the focal position of the X-ray are specified. By specifying the position of the image intensifier 3, the position of the installation surface of the wire collimator 24 described later is specified.

  FIG. 2 is a diagram showing a basic structure of fluoroscopic image formation by the X-ray positioning apparatus 1. As shown in FIG. 2, the X-ray source device 2 includes an X-ray source 21, and a laser marker 22 and a mirror 23 are provided below the X-ray source 21. A wire collimator 24 is installed above the image intensifier 3 so as to be interposed between the image intensifier 3 and the top plate 8.

  The X-ray source 21 is composed of an electron accelerator, a counter-electron beam target, and the like, and generates X-rays by accelerating electrons with the electron accelerator and colliding with the counter-electron beam target.

  The image intensifier 3 includes an optical system that converts transmitted radiation into visible light. The radiation generated by the X-ray source 21 reaches the image intensifier 3 through the subject P. The image intensifier 3 converts the radiation transmitted through the subject P into a visible light image and forms a fluoroscopic image in the subject. A CCD image sensor is arranged below the image intensifier 3, and a fluoroscopic image that can be displayed on a monitor or the like by photoelectrically converting a visible light image is created.

  FIG. 3 is a perspective view showing the structure of the wire collimator 24. The wire collimator 24 makes the approximate position and range of the affected part visible on the fluoroscopic image. The wire collimator 24 includes wires 25X1, 25X2, 25Y1, and 25Y2 (hereinafter referred to simply as “wire 25” when a specific wire is not specified and simply referred to as “wire 25”) arranged in a cross pattern. Yes. The wire collimator 24 adjusts the opening degree so as to surround the affected area, and the line shadow of the wire 25 surrounding the affected area is projected on the fluoroscopic image, so that the approximate position and range of the affected area can be visually confirmed on the fluoroscopic image. .

  The wire collimator 24 has a drive mechanism including a belt 26, a pulley 27, and a drive motor 28 for adjusting the opening degree. The belt 26 is extended in a rectangular shape or a square shape so as to surround the wire collimator 24 in the form of a cross girder, and two belts are arranged side by side. The pulleys 27 are respectively arranged at both ends of the total of eight belts 26, and each belt 26 is wound around an endless track. A total of four drive motors 28 are arranged corresponding to the wires 25.

  Each wire 25 is laid on a belt 26 extending on two sides orthogonal to the arrangement direction. Two wires 25X1 and 25X2 or wires 25Y1 and 25Y2 having the same arrangement direction are laid on different belts 26, respectively.

  Each drive motor 28 rotates each pulley 27 to carry the corresponding wire 25 in parallel. Each drive motor 28 rotates each pulley 27 around which two belts 26 laying corresponding wires 25 are rotated by the same angle. The wire 25 is conveyed in parallel along the belt 26 by the rotation of the pulley 27. The four drive motors can be driven independently, and each wire 25 is independently conveyed in parallel.

  A gear is press-fitted and fixed to the shaft of the drive motor 28, and a potentiometer 29 is installed through the gear. The potentiometer 29 has a variable resistance inside. The variable resistor cumulatively varies the resistance value according to the rotation direction and the rotation amount of the drive motor 28. With this resistance value, the distance of each wire 25 from the X-ray axis can be detected. An encoder may be used as a means for detecting the distance of each wire 25 from the X-ray axis. The encoder includes a relative position encoder and an absolute position encoder. The encoder has an optical sensor inside, and generates a pulse signal according to the rotation angle. The distance is detected by this pulse.

  The laser marker 22 irradiates a laser and draws a projected image of the wire 25 assembled in a cross pattern on the body surface. The mirror 23 reflects the laser toward the body surface by changing the orientation angle so that the laser irradiated by the laser marker 22 indicates the shape and position of the projected image.

  FIG. 4A is a perspective view showing the positional relationship between the laser marker 22 and the mirror 23. FIG. 4B is an enlarged view of the vicinity of the mirror 23.

  As shown in FIG. 4, four laser markers 22 are arranged in the X-ray source device 2. Each laser marker 22 irradiates laser light that diffuses linearly. The laser marker 22 corresponds to each wire 25 and extends in parallel with the corresponding wire 25.

  Four mirrors 23 are arranged in the X-ray source device 2 corresponding to each laser marker 22. The arrangement position is in the laser beam irradiation direction of the corresponding laser marker 22. This mirror 23 reflects the laser light irradiated by the laser marker 22 and reflects it in the direction of each wire 25. The mirror 23 is connected to the position adjustment mechanism 23a. The position adjustment mechanism 23 a changes the orientation angle and the movement position of the mirror 23. The position adjusting mechanism 23a includes a drive motor and a potentiometer, changes the orientation angle of the mirror 23 to a predetermined angle, moves the mirror 23 toward the corresponding laser marker 22, and moves the mirror 23 to the focal point of the radiation and the wire 25. Stop on the connecting segment.

  FIG. 5 is a flowchart showing a schematic operation for determining the exposure direction and irradiation field of the radiation positioning apparatus 1. The radiation positioning apparatus 1 rotates the rotating pedestal 5, moves the bed 8 in the body axis direction of the subject P, and moves the radiation head 2 and the image intensifier 3 closer to or away from the subject P, thereby isocentering. Is adjusted to the position of the affected part of the subject P (S01).

  Radiation is generated in the radiation source 21 (S02), and a fluoroscopic image is formed from the radiation transmitted through the subject P in the image intensifier 3 (S03). When the affected part is specified from the fluoroscopic image, the wire collimator 24 is moved so as to surround the affected part (S04), and the shadow of the wire 25 surrounding the affected part is projected on the fluoroscopic image (S05).

  Next, the detection result of the potentiometer 29 is analyzed, and the distance from the radiation axis of each wire 25 is calculated (S06). Further, the sliding amount of the radiation head 2 and the image intensifier 3 is analyzed, and the distance between the focal point of the radiation and the installation surface of the wire collimator 24 is calculated (S07). From the calculation results of S6 and S7, an angle α between the line segment connecting the focal point of the radiation and each wire 25 and the radiation axis is calculated (S08).

  Based on the calculated angle α, the orientation angle of the mirror 23 is changed so as to reflect the laser from the focal direction of the radiation to the direction of each wire 25 (S09), and the laser is irradiated from the laser marker 22 (S10).

  By this laser irradiation, a projected image when the wire 25 assembled in a cross pattern on the body surface of the subject P is projected onto the body surface is drawn by the laser. Thereafter, a doctor or an engineer traces a projected image drawn with a laser with a magic or the like, thereby determining the approximate position and range of the affected area on the body surface.

  A control mechanism for laser irradiation on the body surface of the subject P will be described in detail. As shown in FIG. 6, the radiation positioning apparatus 1 includes a control mechanism 11 that controls the laser irradiation direction.

  The control mechanism 11 stores a control program in an external storage unit including an arithmetic unit 12, a wire collimator control unit 13, and a laser control unit 14, which includes an arithmetic processing unit, a main storage unit, and an external storage unit. The control program is expanded in the main storage unit, and the arithmetic processing unit performs arithmetic processing and control processing according to the control program, and controls the radiation head 2, the image intensifier 3, the laser marker 22 and the mirror 23.

  The computing device 12 creates displacement instruction information for each wire collimator 24 and outputs it to the wire collimator control device 13 when the irradiation field is defined. At the time of marking, drive instruction information for the laser marker 22 and the mirror 23 is created and output to the laser controller 14.

  The displacement instruction information for the wire collimator 24 is information reflecting the displacement amount of each wire 25.

  The drive instruction information for the laser marker 22 and the mirror 23 is information reflecting the instruction to drive the laser marker 22 and the moving direction, moving amount, and direction angle of the mirror 23. Information about the mirror 23 is created by the positional relationship between the wire 25 and the radiation focus. The radiation focus is uniquely determined by the position of the radiation source 21.

  The positional relationship between the wire 25 and the radiation focus is represented by an angle α between a line segment connecting the radiation focus and the wire 25 and the radiation axis. This angle α is calculated from the distance between the radiation focus based on the sliding amount of the radiation head 2 and the image intensifier 3 and the installation surface of the wire collimator 24 and the distance between each wire 25 and the radiation axis.

  The wire collimator control device 13 controls the drive motor 28 provided in the wire collimator 24 according to the displacement instruction information output from the arithmetic device 12 to displace each wire 25. The laser control device 14 controls the drive motor that drives the mirror 23 to move the mirror 23 by a predetermined amount in a predetermined direction and rotate it by a predetermined angle, and to irradiate the laser marker 22 with laser. The movement direction, the movement amount, and the rotation angle are included in the drive instruction information created by the calculation device 12.

  FIG. 7 shows a process for calculating the positional relationship between each wire 25 and the radiation focus. First, when the radiation head 2 and the image intensifier 3 slide along with the arms 6 and 7, the potentiometer detects the positions of the irradiation head 2 and the image intensifier 3 (S21).

  From the positions of the radiation head 2 and the image intensifier 3 detected by the potentiometers of the radiation head 2 and the image intensifier 3, the position of the radiation focal point moving along with the position of the installation surface of the wire collimator 24 can be obtained. From this position information, distance information Hw between the radiation focus and the installation surface of the wire collimator 24 is obtained (S22).

  Next, the drive motor 28 is driven to displace the distance of each wire 25 from the radiation axis, and an electric signal indicating the cumulative rotation direction and rotation amount of the drive motor 28 is input from the potentiometer 29 (S23). The arithmetic unit 12 converts the input signal into distance information Dw from the radiation axis of each wire 25 (S24).

  Next, from the distance information Hw and the distance information Dw, an angle α formed by a line segment connecting the focal point of the radiation and each wire 25 and the radiation axis is calculated (S25).

  FIG. 8 is a conceptual diagram illustrating the movement direction and amount of the mirror 23 and the calculation of the orientation angle.

  The angle formed between the line connecting the X-ray focal point and the wire 25 and the radiation axis is α, and the orientation angle of the mirror 23 is β. The orientation angle β indicates the angle formed by the mirror 23 with respect to the installation surface direction of the wire collimator 24, and increases in proportion to the counterclockwise rotation of the mirror 23. In this case, the orientation angle β of the mirror 23 can also be obtained from the angle α and the laser irradiation inclination.

  For example, if the laser irradiation inclination is 180 °, the orientation angle β of the mirror 23 is β = (180−α) / 2. Accordingly, when the angle α formed increases by Δα, the mirror 23 is rotated by Δα / 2, whereby the laser beam is reflected toward the wire 25.

  If the X-ray focal point and the laser irradiation tube distance are X, the moving distance ε of the mirror 23 is ε = X tan α in the direction of the laser marker 22. Accordingly, when the angle α formed increases by Δα, the mirror 23 is moved by ε = X (tan (α + Δα) −tanα), and the reflected light reflected by the mirror 23 is similar to that irradiated from the focal point of the radiation. Become light.

  FIG. 9 is a flowchart showing the control operation of the mirror 23. First, when the radiation head 2, the image intensifier 3, and the wire 25 are displaced (S31), distance information Hw and distance information Dw are acquired (S32), and a line segment connecting the focal point of the radiation and each wire 25 is obtained. An angle α formed with the radiation axis is calculated (S33).

  When the formed angle α is calculated, the arithmetic unit 12 calculates the orientation angle β of each mirror 23 based on β = (180−α) / 2 (S34), and the moving distance of each mirror 23 based on ε = Xtanα. ε is calculated (S35).

  Next, drive instruction information including the orientation angle β and the movement distance ε is output to the laser control device 14 (S36). When the drive instruction information is input, the laser control device 14 drives the drive motor and moves each mirror 23 in the direction of the laser marker 22 by the moving distance ε while detecting the position of each mirror 23 with the potentiometer, thereby causing radiation. Is located at the intersection of the line segment connecting the focal point of each of the wires 25 and the irradiation direction of the laser beam irradiated by the laser marker 22 (S37).

  Further, when the drive instruction information is input, the laser control device 14 drives the drive motor, rotates each mirror 23 while detecting the orientation angle of each mirror 23 with a potentiometer, and sets each mirror 23 to the orientation angle β. Change (S38).

  When the movement of the mirror 23 and the angle change are completed, the laser control device 14 drives the laser marker 22 to irradiate the laser beam (S39).

  As a result, the laser light emitted from the laser marker 22 is reflected by the mirror 23, and the reflected light is directed from the focal point of the radiation to the direction of each wire 25 to form a projection image simulating the shape of the wire collimator 24 on the body surface. Draw. A doctor or engineer marks with this magic along the projected image.

  As described above, the radiation positioning apparatus 1 of the present embodiment includes the laser marker that irradiates the body surface with the laser, and irradiates the laser in the direction of each wire 25, so that the line shadow of the wire collimator 24 is formed on the body surface. The projected image is projected when is projected.

  Therefore, a projected image is clearly depicted on the body surface, and marking can be performed easily and accurately by a doctor or an engineer. In addition, this further imparts reliability to the mark indicating the shape and position of the affected area.

It is a schematic diagram which shows the structural example of the radiation positioning device which concerns on this embodiment. It is a figure which shows the basic structure on the radiation irradiation axis line of the radiation positioning device which concerns on this embodiment. It is a perspective view which shows the structure of the wire collimator with which the radiation positioning device which concerns on this embodiment is provided. It is a figure which shows the laser marker with which the radiation positioning device which concerns on this embodiment is provided in detail. It is a flowchart figure which shows schematic operation | movement which determines the irradiation direction and irradiation field of the radiation positioning device which concerns on this embodiment. It is a block diagram which shows the control mechanism of the radiation positioning device which concerns on this embodiment. It is a flowchart figure which shows the wire collimator position calculation process of the radiation positioning device which concerns on this embodiment. It is a conceptual diagram explaining calculation of the moving direction of a mirror, the amount of movement, and direction angle by the radiation positioning device concerning this embodiment. It is a flowchart figure which shows the control operation of the laser by the radiation positioning device which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation positioning apparatus 2 Irradiation head 21 Radiation source 22 Laser marker 23 Mirror 24 Wire collimator 25, 25X1, 25X2, 25Y1, 25Y2 Wire 26 Belt 27 Pulley 28 Drive motor 29 Potentiometer 3 Image intensifier 4 Fixed stand 5 Rotating stand 6 Arm 7 arm 8 bed 10 rotating shaft 11 control mechanism 12 arithmetic device 13 wire collimator control device 14 laser control device

Claims (5)

A radiation source that emits radiation to the subject;
An image intensifier that forms an in-subject image from radiation transmitted through the subject;
A wire collimator having a plurality of wires and projecting a shadow of the wire on the in-subject image interposed between the radiation source and the image intensifier;
Laser marker means for irradiating a laser beam imitating the shape of the wire collimator, changing the irradiation direction based on the positional relationship between the radiation source and each wire,
With
The shape of the wire collimator is projected on the surface of the subject placed on the bed by the laser light from the laser marker means,
A radiation positioning apparatus characterized by the above. The laser marker means includes
A laser marker for irradiating a laser beam;
Based on the positional relationship between the radiation source and each wire, a reflecting plate that changes the direction of the laser light by changing the orientation angle;
Including,
The radiation positioning apparatus according to claim 1. The laser marker means irradiates the laser beam so that the irradiation axis of the laser beam passes through the focal point of the radiation;
The radiation positioning apparatus according to claim 1. The laser marker means includes
A laser marker for irradiating a laser beam;
A reflector that changes the direction of laser light irradiation;
Based on the positional relationship between the radiation source and the wire collimator, the reflector changes the direction angle and moves a predetermined distance in a predetermined direction to change the irradiation direction of the laser light,
Including,
The radiation positioning apparatus according to claim 3. Further comprising a bed for placing a subject interposed between the radiation source and the wire collimator;
A radiation positioning apparatus characterized by the above.

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