JPH0114782B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for positioning an irradiation target region and a radiation irradiation barrel in a radiation apparatus such as a dental X-ray imaging apparatus or a therapeutic radiation irradiation apparatus.

Among the above-mentioned dental X-ray imaging devices, those that perform X-ray imaging of two or three specific teeth instead of performing panoramic X-ray imaging of the entire jaw set a film inside the oral cavity. This is then irradiated with X-rays from the outside to take an image and use it for diagnosis. Conventionally, the positioning of the film and the X-ray irradiation tube relied on the operator's visual inspection and intuition, which could result in misalignment. Not only does the film easily come off from the X-ray irradiation field, exposing unnecessary areas to X-rays, but the target tooth is not captured on the film, resulting in a so-called cone cut, which requires re-imaging, further increasing the amount of radiation the human body is exposed to. On the other hand, in order to suppress this cone cut, the irradiation field of X-rays must be expanded, which causes the problem of unnecessary radiation exposure to the periphery of the target area.

In addition, when performing treatment by irradiating radiation to a specific part of a patient's body, since that part is inside the body and cannot be seen directly from the outside, the target part is determined by computer image processing and radiation is applied to that part. Although the operation is complicated, it is difficult to position the target area and the radiation tube, and there is a lack of reproducibility.

The present invention has been devised to eliminate such inconveniences, and enables easy and accurate positioning of irradiation target areas that cannot be easily seen from the outside, such as oral teeth and internal body parts. The purpose is to provide a method.

That is, the present invention provides a radiation apparatus in which a magnetic field is formed by providing a magnetic source on the side of the target area to be irradiated with radiation, and a magnetic field is provided in the radiation irradiation tube within the same plane perpendicular to the irradiation radiation axis and equidistant from each other. Either magnetic detection sensors are mounted at a plurality of positions so that the magnetic sensitive axes of these sensors are mutually symmetrical with respect to the irradiation radiation axis, or one magnetic detection sensor is sequentially moved over the plurality of positions. The radiation irradiation cylinder is positioned with respect to the irradiation target site by matching outputs of magnetic detection sensors sensitive to magnetic fields at each of the positions.

With this configuration, the positional relationship between the irradiation target area and the radiation irradiation tube is automatically determined from the correspondence between the magnetic field and the magnetic detection sensor group, and it is possible to accurately irradiate the target irradiation area. can.

For example, in the above-mentioned dental imaging, the film and the X-ray irradiation barrel can be positioned without relying on the operator's visual inspection or intuition, and the film can be placed within the X-ray irradiation field to image the target tooth without causing cone cuts. This not only reduces radiation exposure to the human body by eliminating the need for re-imaging based on cone cuts, but also allows the film to be placed within the X-ray irradiation field, making this irradiation field narrower than before and reducing the X-ray dose accordingly. This makes it possible to further reduce the amount of radiation that the human body is exposed to.

Also, when administering radiation therapy to a specific part of the human body, you can mark the point on the human body surface that corresponds to the irradiation target part, and attach the magnetic source on top of this marking. Using the generated magnetic field, the radiation irradiation tube can be correctly directed to the irradiation target site. Therefore, as long as the magnetic source is attached to the marking, it can be easily directed to the irradiation target site at any time, improving operability and providing reproducible radiation therapy.

The present invention is made using the principles shown in FIGS. 1 and 2. That is, a magnetic source M made of a magnet or an electromagnet is placed at a certain point on the coordinates, and this magnetic source M forms a symmetrical magnetic field around its central axis m. Corresponding to this, a movable object A is provided,
If this movable object A has four magnetic detection sensors S... disposed at equal intervals in the circumferential direction around its central axis a, and the distance r from the central axis a of each magnetic detection sensor S... is made to be the same, , these sensors S...
When the magnetic source M is moved two-dimensionally or three-dimensionally to a position where the magnetic detection outputs of the movable object A and the magnetic source M exhibit the same value, the central axis of the movable object A and the magnetic source M at the point where the magnetic detection outputs of the movable object A and the magnetic source M exhibit the same value a and m are positioned coaxially. In other words, in the coaxial state, the distance from the magnetic source M to each magnetic detection sensor S is the same, and each sensor is placed in an area with the same magnetic field strength of the symmetrical magnetic field formed by the magnetic source M, resulting in the sensor output naturally match.

As the magnetic detection sensor, a magnetic modulation type sensor, a Hall element, a magnetoresistive element, a SQUID, etc. can be considered. Further, although the number of sensors is four in the above example, it may be two or more, and the number is selected according to the preferred usage pattern.

FIG. 3 shows a dental X-ray photographing method according to an embodiment of the present invention, in which a magnet M is attached to a film F by an appropriate means.
is attached, and this film F is positioned inside the irradiation target tooth 1. At this time, when performing the bisection imaging method, the magnet M is placed on the back side of the film F at an angle α such that it is perpendicular to the center line a of the incident X-rays.
At the same time, the center of the magnet m should be aligned with the center of the film. On the other hand, a total of four magnetic detection sensors FG ₁ to _{FG 4} are attached to the outer periphery of the tip of the X-ray irradiation tube 2 at equal intervals in the circumferential direction. This sensor is a flux gate type, with the primary winding connected to the core eye shown in Figure 4.
The secondary winding is wound evenly in A and B, and connected in reverse to form the output. The core has high permeability,
A material with square hysteresis characteristics is used.

Then, from the state where the film F is positioned inside the patient's irradiation target tooth 1 as described above, the X-ray irradiation tube 2 is moved to detect each magnetic detection sensor FG ₁ to _{FG 4 .}
If the operation is performed so that all the output values of
When radiography is performed, the film F is completely contained within the X-ray irradiation field, and the irradiation target tooth 1 can be photographed without causing a cone cut.

FIG. 5 is a block diagram showing an example of input/output processing for the above-mentioned flux gate type magnetic detection sensors FG ₁ to FG ₄ , in which a square wave signal generated by the square wave generator 3 is applied to the current and voltage amplifier 4. via sensor
A frequency of 10 to 100 KHz is input to the primary side of FG ₁ to _{FG 4} , and the peak value of the secondary output of each sensor FG ₁ to _{FG 4} is taken by a peak hold circuit 5 and used as the information amount of the external magnetic field. Furthermore, FG ₁ and
Using FG ₃ , FG ₂ and FG ₄ as a pair, these output peak values are passed through comparison amplifier circuit 6 and then displayed on display 7.
Alternatively, the control circuit 8 moves the patient or the radiation irradiation tube 2 in the X-Y axis directions in a combined manner.

FIG. 6 shows an embodiment in which the present invention is applied to radiation therapy. When treating an irradiation target site P ₁ in a patient's body, the radiation central axis a passes through point P ₁ during the first irradiation treatment. With the radiation irradiation tube 2' properly set, a point _P2 on the human body surface through which the central axis a passes is determined, and a marking is applied to this point.
For subsequent irradiation, the magnet M attached to the stand 9 is fixed with tape or the like over the point _P2 each time. This table 9 is angled so that the extension of the central axis m of the magnet M passes through the irradiation target region _P1 , and this angle is determined from the positional relationship between _P1 and _P2 to shape the table 9. I'll keep it. In this way, by directing the radiation irradiation tube 2' to which the magnetic detection sensors FG ₁ to FG ₄ are attached, the central axis a of the radiation can be aligned with the irradiation target area due to the magnetic relationship between the magnet M and the sensors FG ₁ to FG ₄ .
The posture passing through P ₁ is easily reproduced, and the treatment can then be started by removing the mounted magnet M after the reproduction of this posture.

FIG. 7 is related to dental X-ray imaging, which is the same as _FIG . Attach the second magnet M ₂ to the
By pointing the image intensifier (fluorescence amplification tube) 11 equipped with Hall sensors H ₁ to _{H 4} outside the oral cavity and coaxially operating the magnets M ₁ and M ₂ and the image intensifier 11, tooth 1 and wire tube 10
Then, the magnet M1 is removed from the irradiation target tooth ₁ and X-ray photography is performed. In this case, the image intensifier 11 is first positioned with respect to the irradiation target tooth 1 using the correspondence between the magnet M ₁ and the Hall sensors H ₁ to H ₄ , and then the X
Insert wire tube 10, magnet M ₂ and Hall sensor H ₁
A suitable positioning order is to position the X-ray tube 10 in correspondence with _H4 .

In addition, in the explanation so far, a plurality of sensors S are fixedly provided, but by rotating a single sensor, for example, as shown in FIG. Alternatively, the output of the sensor may be extracted and compared.

The present invention has been described above, and has successfully achieved its intended purpose.

[Brief explanation of drawings]

1 and 2 are operation diagrams for explaining the principle of the present invention, FIG. 3 is a schematic diagram showing a dental X-ray photographing method as an embodiment of the present invention, and FIG. Fig. 5 is a block diagram showing an example of an input/output circuit for the sensor; Fig. 6 is a conceptual diagram showing the radiation irradiation method of the second embodiment; Fig. 7 The figure is a schematic diagram showing a dental X-ray photographing method according to a third embodiment. (Explanation of symbols), 1, P ₁ ... irradiation target area,
2, 2'... Radiation irradiation tube, FG ₁ ~ FG ₄ , H ₁ ~ _{H 4}
...Magnetic detection sensor, M...Magnet.

Claims (1)

[Claims] 1. In a radiation device, a magnetic field is formed by providing a magnetic source on the side of the target area to be irradiated with radiation, and the radiation irradiation tube has multiple positions equidistant from each other within the same plane perpendicular to the irradiation radiation axis. Each magnetic detection sensor is mounted such that the magnetic sensitive axes of these sensors are mutually symmetrical with respect to the irradiation radiation axis, or one magnetic detection sensor is provided so as to be sequentially moved over the plurality of positions,
A method of positioning in a radiation apparatus, characterized in that the radiation irradiation cylinder is positioned with respect to the irradiation target site by matching outputs of magnetic detection sensors sensitive to magnetic fields at each of the positions.