JP3364501B2 - Charged particle therapy device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment apparatus using charged particles, and more particularly to a charged particle treatment apparatus for controlling a magnetic field. 2. Description of the Related Art As radiation of a radiotherapy apparatus, there is an example using charged particles in addition to an example using X-rays and γ-rays. For X-rays and γ-rays, a collimator using a material such as lead is used for controlling the flux. The beam flux control includes control of the traveling direction of the dose in addition to the control of the dose. On the other hand, such a collimator cannot be used for charged particles, and an opening for emitting accelerated charged particles is provided, and a lesion is formed from the opening in the traveling direction of the charged particles to irradiate the charged particles. [0003] In the treatment with charged particles, it is not easy to accurately irradiate a lesion, and sometimes irradiation is performed to normal tissues other than the lesion. In order to perform accurate irradiation, the patient itself may be moved together with positioning, such as moving a bed on which the patient is mounted, thereby imposing a burden on the patient. [0004] It is an object of the present invention to provide a charged particle therapy apparatus that enables control of the flux of charged particles. SUMMARY OF THE INVENTION The present invention is directed to an irradiation head mounted on a rotating gantry and irradiating a charged part of a patient placed on a treatment table with charged particles as the gantry rotates, and the irradiation head. Control means for controlling the irradiation of the charged particles to the lesion from the magnetic field applying means for forming a trajectory of the charged particles, and the control means is determined so that the lesion becomes an irradiation field of the charged particles. A memory for storing a magnetic flux pattern determined by a treatment table position and a gantry rotation angle;
Means for reading a magnetic flux determined by the treatment table position and the gantry rotation angle from the memory when the gantry is rotated,
The read magnetic flux is input to the magnetic field applying means,
There is disclosed a charged particle treatment apparatus including magnetic field control means for controlling a trajectory of charged particles to be determined by the magnetic flux. According to the present invention, the trajectory of a charged particle passing through a patient is forcibly controlled by a magnetic field, thereby concentrating on a lesion. Irradiation becomes possible. Further according to the present invention, according to each irradiation site to the lesion, the magnetic field in the middle of the trajectory in the patient will be changed according to a predetermined magnetic flux pattern,
The treatment for various treatment sites can be achieved by the shape of the magnetic flux pattern. FIG. 1 is a diagram showing an embodiment of the present invention. In the present embodiment, stereotactic treatment using charged particles is realized by a treatment gantry 1, a treatment table 2, an irradiation head 3 attached to the tip of the gantry 1, and a magnetic field generator 6. Treatment table 2
A patient 4 is mounted thereon, and the charged particles 7 from the irradiation head 3 can be irradiated to the lesion 5. A magnetic field generator 6 is fixedly attached to the treatment table 2.
The treatment table 2 is rotated around the vertical axis 9 at a rotation pitch of about 20 °, and stands still at each position of 0 °, 20 °, 40 °,.... The gantry 1 rotates around a horizontal axis 8 while the couch 2 is stationary. The rotation includes 360 ° rotation (one rotation), 180 ° rotation (half rotation), and the like, and the charged particles 7 are irradiated to the lesion 5 during this rotation. The charged particles 7
It is obtained from the accelerator. Note that the rotation of the gantry 1 is performed in consideration of the presence of the magnetic field generator 7, and when the magnetic field generator 7 is at a position where it hinders the progress of the charged particles, the charged particles are not emitted. It is desirable to do. The magnetic field generator 6 is provided at a position sandwiching the lesion 5 from the horizontal direction, and controls the trajectory so that the trajectory of the charged particles 7 is directed to the lesion 5. Here, the trajectory control will be described. If a magnetic field is applied from the magnetic field generator 6 to the charged particle 7 in a direction perpendicular to the charged particle 7, the trajectory of the charged particle 7 is controlled by Lorentz force. The Lorentz force F at this time is as follows: F = q (V × B) q is the charge of the charged particles, V is the velocity vector, and B is the magnetic flux density due to the magnetic field. Here, if the energy of the charged particles is constant, the product of the magnitude of the magnetic flux density B and the radius of gyration r of the trajectory of the charged particles around the line of magnetic force is constant. At this time, the radius of gyration r is as follows: F = q (V × B) = mV ² / r, and r = mV / (qB). Here, m is the mass of the charged particles. Therefore, the velocity V and the magnetic field B are selected so that the charged particles 7 are focused on the lesion 5. by this,
Focusing of the charged particles on the lesion 5 becomes possible. Charged particles include electron beams and nuclei. For the exposed lesions, various charged particles can be used. However, treating a lesion inside the head that is not exposed requires energy to reach the lesion inside the head. FIG.
It is a figure which shows the depth in a human body tissue in X-rays (200 kV), an electron beam (16.4 MeV), and a deuterium nucleus (190 MeV), and its deep dose. From this figure, it can be seen that an electron beam can be used in a shallow interior, but it is preferable to use deuterium nuclei in a deep interior. The type and energy of the charged particles are selected in consideration of the depth of the lesion and the purpose of treatment. FIG. 3 shows an apparatus for realizing stereotactic therapy as shown in FIG. 1. The difference is that the magnetic field generator 6 is attached to the gantry 1 and the charged particles 7 are independent of the rotational position of the treatment table 2. This is an embodiment in which a magnetic field is applied from a direction perpendicular to a predetermined angle. According to this embodiment, gantry 1
Can be rotated around the patient 4 by being integrated with the magnetic field generator 6, which has the effect that various angles of treatment can be taken.
In the embodiment of FIG. 1, depending on the external size of the magnetic field generator 6, the rotation of the gantry 1 may be hindered and the rotation angle may be controlled. However, in the present embodiment, this is not the case. The magnetic field generator 6 can be either a permanent magnet or an electromagnet. An example of an electromagnet is shown in FIG. FIG.
(A) is a so-called electromagnet in which the coils 10A and 10B are opposed to each other and the iron core 11 is used as a magnetic path. FIG. 4B shows a so-called cyclotron type electromagnet obtained by improving the wise type electromagnet.
0A and 10B are opposed to each other, and the iron core 11 is arranged around the core. For example, in order to confine a generally used 4 MeV electron beam in a lesion having a diameter of 3 cm, a magnetic field of 1.0 Tesla may be generated.
For 5 MeV electrons, a magnetic field of 1.2 Tesla may be generated. In the case of an electromagnet, a superconducting electromagnet may be used. The trajectory control of the charged particles by the magnetic field generator as shown in FIGS. 1 and 3 is performed by controlling the magnetic field. This magnetic field control is based on the position and size of the lesion, the state of the living tissue around the lesion (what and what size, etc.), the type and energy of the charged particles, the gantry angle (position), the treatment table Considering various parameters represented by position etc.,
It is performed so that charged particles are focused on the lesion. Such magnetic field control is to perform magnetic flux control, and the magnetic flux control is realized by controlling the current applied to the coil. In the following, since the magnetic field control is a spatial trajectory control of charged particles in a patient, it is referred to as a magnetic field control based on a spatial magnetic flux pattern. FIG. 5 is a diagram showing an example of magnetic field control.
According to the following contents. (A), control of the presence or absence of magnetic field application,
(B), control of the magnetic field polarity, (C), control of the magnitude of the magnetic field, and these controls (A) to (C) are performed in accordance with each predetermined trajectory of the charged particle in the patient space. This is performed with a simple magnetic flux pattern. However, the trajectory of the charged particle is the gantry 1
Is determined by the angle (position). FIG. 5 shows an example in which a lesion is located at the back of the eyeball of the head. I want to avoid irradiating charged particles to the eyeball and protect the eyeball. In order to treat a lesion located in the back of the eyeball, charged particles from the directions 101, 102, 107, and 108 may be irradiated as they are, so that control without applying a magnetic field is performed. If the charged particles from the directions 103 and 104 are irradiated without bending the trajectory as they are, they will pass through the eyeball part. To avoid this, the application of the magnetic field is controlled. The application direction (polarity) at this time is a direction from the back side of the paper to the front side. The trajectory of the charged particles from the directions 105 and 106 also needs to be bent. However, since it is necessary to bend the trajectory in the direction opposite to the directions in the directions 103 and 104, a magnetic field is applied in a direction (polarity) from the front side to the back side of the drawing. By adding the control (c), more accurate trajectory control can be achieved. In order to realize a charged particle trajectory as shown in FIG.
It is sufficient to prepare a memory table that stores the control contents (actually, those that give a spatial speed pattern). It is an example of application to the device of FIG. In the memory table,
The gantry angle indicates the entry trajectory of the charged particles, and the treatment table position indicates each stationary position. In the figure, the gantry sample pitch angle is α ゜, and the rotation pitch angle of the treatment table is θ ゜. Further, the data has a 2-bit configuration, and 00: no magnetic field is applied 01: magnetic field is applied 10: the polarity of the magnetic field is positive 11 and the polarity of the magnetic field is negative. Therefore, for example, (2θ, 3
In α), the data is “10”, which indicates that the polarity of the magnetic field is applied to the positive electrode. Here, the positive electrode and the negative electrode mean that the polarities are opposite to each other. Having prepared such a memory table,
If the corresponding data is read out from the gantry angle and the treatment table position and the magnetic flux control by the magnetic field generator 6 is realized, the charged particle is irradiated to the lesion. It should be noted that the present invention can be applied to FIG. 3 and the data of the magnitude control of the magnetic field shown in FIG. FIG. 5 shows the magnetic field control for each orbit (a) to (d).
Although the example is performed according to (c), it is more preferable to perform the magnetic field control in the path of each orbit. That is, in the example of FIG. 5, for example, a magnetic field having a certain polarity and a certain magnitude is applied in the direction 104, but various changing magnetic fields are applied along the traveling path in the direction 104 instead of the fixed magnitude. To do. As a result, various trajectory controls can be performed for the lesion. This can be realized by providing a three-dimensional memory table instead of a two-dimensional memory table in the memory table of FIG. An embodiment from this viewpoint will be described with reference to FIGS. FIG. 7 is a diagram showing an example of control using a spatial magnetic field pattern (magnetic flux pattern) in a case where there is an important organ in the deep part and a lesion exists in the procedure of this important organ. A magnetic field as shown in the figure is given with the center point of the important organ as the origin. That is, the contour lines of the magnetic flux density in the x direction and the y direction are given in a substantially fan shape, and the magnetic flux density at each contour line is B ₁ in the section of the distance a from the origin and the distance a
The section from to the distance b is made smaller as the distance increases. Here, the distance a is a distance larger than the width of the important organ from the origin. The distance b is
It is the position corresponding to the patient's skin. Further, the distance c is a set distance for preventing charged particles from entering the important organ, and the charged particles are prevented from advancing near this distance c.
For this blocking, over a large magnetic flux density B ₁ in 0 to A, and so rapidly rotating (spiral rotational movement of the inward) at and a distance c. The affected part is preferably located slightly outside the distance c. According to the application of the magnetic field shown in FIG. 7, the charged particles enter the affected area through a trajectory according to the magnitude of the magnetic field determined by the contour lines. Then, due to the existence of the magnetic flux density B ₁ and the gradient magnetic field up to the distance c, the charged particles are stopped from traveling near the distance c, and do not enter the important organ. In order to realize the embodiment of FIG. 7, a table may be prepared from the same viewpoint as that of FIG. 6, and the table may be read from the position of the treatment table and the angle of the gantry to control the current of the electromagnet. However, unlike FIG. 6, it is necessary to control the magnitude of the current, and it is necessary to convert this into data. Further, although the control is realized by controlling the magnetic field, the control of the energy of the charged particles may be added. FIG. 8 shows an example in which the magnetic field distribution is set so that the magnetic field has a maximum value at the center of the lesion. The lesion center as the origin, the magnetic flux density B ₂ in the origin as the maximum, is set so that the magnetic flux density is lowered as it is away from the lesion. When the magnetic field is set in this manner, the charged particles converge while spirally moving toward the center of the lesion as shown by the dotted line. FIG. 9 shows an example in which the irradiation direction of the charged particles and the direction of the magnetic flux density are slightly shifted from the vertical direction by an angle δ. By doing so, the motion of the charged particles becomes not only in a single plane but also in a three-dimensional manner, and irradiation can be performed over a wide area of the lesion. FIG. 10 is an embodiment diagram in which a magnetic field is applied in parallel to the direction of the charged particle beam. By applying a magnetic field in parallel so as to surround the charged particle beam, scattered radiation that spreads to the surroundings can be confined by the magnetic field and damage to normal tissue can be reduced. In this case, the control in the depth direction is performed by the characteristics of the interaction of the charged particle beam with the substance. That is, according to FIG. 2, the charged particle beam is different from an electromagnetic wave such as an X-ray, and has a peak of the absorbed dose at a certain depth (this is due to energy) in the substance. The characteristic of becoming zero is known, and the energy of the charged particle beam is selected so that the lesion is located at the peak depth of the absorbed dose using this characteristic. A device for applying a magnetic field in parallel so as to surround the charged particle beam is a magnetic field generating device 6A attached to the irradiation head 3 and a magnetic field generating device 6B opposed to the magnetic field generating device 6 with a patient interposed therebetween. The magnetic field generator 6A
It is a hollow cylindrical electromagnet having a passage for charged particles 7 emitted from the irradiation head 3 inside. The magnetic field generator 6B also
It is a hollow cylindrical electromagnet. The charged particles 7 are confined by the devices 6A and 6B so as to face the lesion. FIG. 11 shows that a main magnetic field is applied in parallel with the charged particle beam, and the magnetic field generator 6A on the upstream side of the charged particle beam is further applied.
This is an embodiment in which the intensity of the magnetic field generator 6B on the downstream side is increased so that the charged particle beam is focused at the lesion within the patient's body using the principle of the magnetic bin. Conversely, by weakening the strength of the magnetic field generator 6B on the downstream side with respect to the magnetic field generator 6A on the upstream side of the charged particle beam, the charged particle beam can be expanded to irradiate a wide range of affected parts. Thus, the irradiation field can be electromagnetically changed by changing the intensity of the magnetic field. Here, the magnetic bin is as follows. As shown in FIG. 11, when the charged particles are advanced along the direction of the magnetic field lines, the particles become slower when approaching a place where the magnetic field is strong, and the velocity becomes zero when there is a relationship between the angle of the particles and the magnetic field lines. Turn over. The flipping of the particles can be considered as a kind of magnetic mirror, and is usually called a magnetic mirror. Therefore, the magnetic field generator 6
When a magnetic mirror is formed that bulges in the area of A and 6B and bulges around on the path connecting 6A and 6B (that is, a kind of beer barrel magnetic field), the particles are reflected by the surroundings while traveling along the magnetic field lines, Held inside. Such a phenomenon is called a magnetic bin ("Detailed Explanation Electromagnetics Exercise" Kyoritsu Shuppan. Kenichi Goto).
Published in 1970). The magnetic field formation as shown in FIGS. 5, 7, 8 and 9 is performed by only one set of the opposing magnetic field generators as shown in FIGS. 1 and 3, but two sets of the opposing magnetic field generators are arranged along the horizontal axis. This can be realized even if the magnetic field generators are provided at 180 ° intervals. Further, while FIGS. 5, 7, 8, and 9 use various gradient magnetic fields, a dedicated magnetic field generator for generating such a specific gradient magnetic field may be provided. Further, the present invention can be applied to a treatment apparatus that does not rotate the gantry or move the treatment table. According to the present invention, since the radiation can be controlled in the patient by the action of the magnetic field, the radiation can be safely administered to the lesion and a high therapeutic effect can be obtained. In particular, since the trajectory of the charged particle can be intensively controlled by positively controlling the trajectory of the charged particles by the magnetic field, the dose itself can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of a charged particle therapy apparatus according to the present invention. FIG. 2 is a comparison diagram of deep doses of charged particles and X-rays handled in the present invention. FIG. 3 is a diagram showing another embodiment of the charged particle therapy device of the present invention. FIG. 4 is a diagram showing an embodiment of a magnetic field generator according to the present invention. FIG. 5 is a diagram showing a charged particle control example of the present invention. FIG. 6 is a diagram showing a memory table storing control data for controlling charged particles according to the present invention. FIG. 7 is a diagram showing another control example of the charged particle of the present invention. FIG. 8 is a diagram showing another control example of the charged particle of the present invention. FIG. 9 is a diagram showing another control example of the charged particle of the present invention. FIG. 10 is a diagram showing another embodiment of the charged particle therapy apparatus of the present invention. FIG. 11 is a diagram illustrating another control example of the charged particle of the present invention. [Description of Signs] 1 therapeutic gantry 2 treatment table 3 irradiation head 4 patient 5 lesion part 6 magnetic field generator 7 charged particles

Claims (1)

(57) [Claims 1] An irradiation head attached to a rotating gantry and irradiating charged particles to a lesion of a patient placed on a treatment table with rotation of the gantry, and an irradiation head from the irradiation head. Control means for controlling the irradiation of charged particles to the lesion, the control means, a magnetic field applying means for forming a trajectory of the charged particles, and the lesion is determined to be an irradiation field of the charged particles,
A memory for storing a magnetic flux pattern determined by the treatment table position and the gantry rotation angle; a means for reading from the memory magnetic flux data determined by the treatment table position and the gantry rotation angle when the gantry is rotated; and the read magnetic flux data And a magnetic field control unit that controls the trajectory of the charged particle to be determined by the magnetic flux.