TWI622418B - Particle beam therapy apparatus - Google Patents

Abstract

The quadrupole electromagnets 2g, 2h, and 2i are used to reduce the beam diameter of the charged particle beam by a predetermined beam diameter reduction factor c to be smaller than the target beam diameter, and then use the scanning electromagnets 7a, 7b on the downstream side. The provided scatterer 8 expands the beam diameter of the charged particle beam, which has been reduced to be smaller than the beam diameter of the target, to the beam diameter of the target, thereby simply stabilizing the beam diameter.

Description

Particle Ray Therapy Device

The present invention relates to a particle beam treatment apparatus for performing cancer treatment by irradiating particle beams with scanning irradiation.

In the conventional particle beam therapy apparatus, as long as the influence of scattering from the medium is small from the emission point to the irradiation point (isocenter) of the accelerator, the beam optics are biased toward the electromagnet, quadrupole electromagnet, and drift space. The beam radius r can be expressed as follows.

r = √ (ε.β)

Here, ε is the beam emissivity and β is the beta accelerator function. The beam from the accelerator does not change with time. As long as the parameters of the electromagnet of the beam delivery system are constant in the xy direction (the direction orthogonal to the direction of travel of the beam), the radius of the isocenter will not change with time. Change for certain. With the beam radius r in the isocenter, control the optical parameters (quadrupole electromagnet current) of the beam delivery system, and set β.

However, when the beam is taken out, if the energy is changed over time in accordance with the emission control, the beam center position changes, for example, the quadrupole component biased to the electromagnet changes, and the beam radius r is expressed as follows.

r (t) = √ (ε.β (t))

Here, the beta accelerator function β (t) that changes with time t is set to β (t) = β ₀ (1 + k (t)), β (0) = β ₀ , and time t = 0 When the beam radius r (0) is set to r (0) = r ₀ = √ (ε.β ₀ ), r (t) becomes as follows.

r (t) = √ (ε.β (t)) = √ (ε.β ₀ (1 + k (t))) = r ₀ √ (1 + k (t))

As a result, since the beam radius r changes with time, there is a problem that the irradiation dose at the isocenter cannot obtain the planned value. Therefore, for example, Patent Document 1 discloses a method of controlling a current with a quadrupole electromagnet to stabilize a beam diameter.

[Prior technical literature] [Patent Literature]

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-503067 (para. 0046, FIG. 2)

However, when the current is controlled by a quadrupole electromagnet, in order to stabilize the beam diameter from the beam diameter variation data, a computer (model data creation computer system) for calculating how to change the quadrupole electromagnet current is required; A device that sequentially sets its data in a four-pole electromagnet (mode data setting control device); and a fast power supply device (mode power supply) that immediately responds to setting changes, so there is a problem that the device becomes complicated.

The present invention was developed by the inventor to solve the above-mentioned problems, and an object of the present invention is to obtain a particle beam therapy device capable of accurately obtaining an irradiation dose with a simple device even with a four-pole electromagnet to control a current.

The particle beam treatment device of the present invention includes: an electromagnet that reduces the charged particle beam; a scanning electromagnet that scans the aforementioned charged particle beam in a direction orthogonal to the beam axis; and a scatterer, The charged particle beam scanned by the scanning electromagnet is reduced to a beam diameter smaller than a target beam diameter by a predetermined reduction factor by the electromagnet, and then expanded to the target beam diameter.

According to the present invention, after the beam diameter of the charged particle beam is reduced to a small size, the scatterer is used to expand the beam diameter to the target, so that the beam diameter can be easily stabilized.

1‧‧‧ front stage accelerator

2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i, 2j, 2k, 2l‧‧‧ quadrupole electromagnet

3‧‧‧ incident device

4, 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i

5‧‧‧ shooting device

7a, 7b‧‧‧‧scanning electromagnet

8‧‧‧ scatterer

10‧‧‧ Irradiation point

11, 12‧‧‧vacuum catheter

13‧‧‧Irradiation device

14, 15‧‧‧Beam diameter changes

20‧‧‧ Circular Accelerator

30, 31‧‧‧ Conveying System

40, 41, 42 ‧ ‧ ‧ irradiation systems

100, 101, 102‧‧‧ Particle Beam Therapy Device

D1, D2, D3‧‧‧‧charged particle beam

FIG. 1 is a schematic diagram showing a schematic configuration of a particle beam treatment apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram for explaining a change in a beam diameter of a charged particle beam in a conventional particle beam therapy apparatus.

FIG. 3 is a diagram for explaining a control state of a beam diameter of a charged particle beam in the particle beam therapy apparatus according to Embodiment 1 of the present invention.

Fig. 4 is a graph showing the dose distribution when uniform irradiation is performed.

Fig. 5 is a graph showing a dose distribution when uneven irradiation is performed.

Fig. 6 is a graph showing the relationship between the beam diameter and the reduction coefficient of the beam diameter.

Fig. 7 is a diagram showing an example of a change in beam diameter in the particle beam therapeutic apparatus according to the first embodiment of the present invention.

Fig. 8 is a schematic diagram showing a schematic configuration of a particle beam therapeutic apparatus according to a second embodiment of the present invention.

Fig. 9 is a schematic diagram showing a schematic configuration of a particle beam therapeutic apparatus according to a third embodiment of the present invention.

Fig. 10 is a diagram for explaining the operation of biasing the electromagnet in the particle beam therapeutic apparatus according to the third embodiment of the present invention.

Embodiment 1.

FIG. 1 is a schematic diagram showing the configuration of a particle beam therapeutic apparatus 100 according to Embodiment 1 of the present invention. As shown in FIG. 1, the particle beam treatment apparatus 100 includes a circular accelerator 20 (hereinafter referred to as an accelerator) which is a synchrotron as a supply source of a charged particle beam, and an irradiation device 13 provided in each treatment room. An irradiation system 40; and a transport system 30 that connects the accelerator 20 to each treatment room and transports the charged particle beam from the accelerator 20 to the irradiation device 13 of each treatment room. And, the embodiment of the present invention The characteristic configuration of the particle beam therapy apparatus 100 in the state 1 is that in the irradiation system 40 provided with the irradiation apparatus 13 installed in each treatment room, the charged particles from the transport system 30 are charged with a quadrupole electromagnet 2g, 2h, and 2i. After the beam is reduced and scanned by the scanning electromagnets 7a and 7b in a direction orthogonal to the beam axis, the scattering amount is adjusted by the scatterer 8 to expand to the target beam diameter, so that the stabilized beam is emitted. The beam is guided to the irradiation point 10.

The accelerator 20 is provided with: a vacuum duct 11 which becomes an orbiting path of a charged particle beam; an incident device 3 for injecting charged particles supplied from the accelerator 1 at the front stage into the vacuum duct 11; and for biasing the orbit of the charged particles, The deflection electromagnets 4a, 4b, 4c, 4d, 4e, 4f are formed by the charged particle beams that cause the charged particles to spiral along the spiral orbit in the vacuum duct 11; and the charged particles that are accelerated in the accelerator 20 The beam is taken out of the accelerator 20 and emitted to the exit device 5 and the like of the conveying system 30. In addition, the deflection electromagnet 4 is a device (not shown) for controlling the various parts, such as a deflection electromagnet control device that controls the exciting current of the deflection electromagnet 4, and other components such as the control of the deflection electromagnet control device to control the accelerator. 20 overall accelerator control device. However, in the technical thinking of the present invention, since it is not limited to the controller of the accelerator 20 itself, it is not limited to the above configuration, as long as it can stably emit the charged particle beam to the transport system 30, of course, various deformations are also allowed . In addition, although the front-stage accelerator 1 is described as a single device in the figure for simplicity, it actually has an ion source (ion beam generating device) that generates charged particles (ions) such as protons and carbon (heavy particles). And a linear accelerator system for initial acceleration of the generated charged particles. And accelerate from the front The charged particles incident on the accelerator 20 by the accelerator 1 are accelerated to about 70 to 80% of the speed of light by being accelerated by a high-frequency electric field and turned by a magnet.

The charged particle beam accelerated by the accelerator 20 is emitted to a so-called HEBT (High Energy Beam Transport) transport system 30. The conveying system 30 includes a vacuum duct 12 serving as a conveying path of the charged particle beam, four-pole electromagnets 2c, 2d, 2e, and 2f for converging the charged particle beam, and a deflection electromagnet 4g for deflecting the beam to a predetermined angle. . The charged particle beam, which is given sufficient energy by the accelerator 20 and travels in the conveying path made by the vacuum duct 12, is converged by the quadrupole electromagnets 2c, 2d, 2e, 2f, and at the same time is biased toward the electromagnet 4g changes the orbit as needed, leading to the irradiation device installed in the designated treatment room.

The irradiation system 40 includes an irradiation device 13, which is a charged particle beam supplied from the delivery system 30, forms an irradiation area according to the size and depth of an affected part of a patient belonging to the irradiation target, and irradiates the affected part. First of all, in the irradiation device 13, the charged particle beam from the conveying system 30 is converged and reduced by the quadrupole electromagnets 2g, 2h, and 2i. However, if used directly, the beam radius r will be at the irradiation point 10 with time t Make a difference.

Fig. 2 is a graph showing the change in the beam radius of the charged particle beam at the irradiation point 10 in a particle beam therapy apparatus that uses only conventional quadrupole electromagnets 2g, 2h, and 2i to control the beam diameter. As shown in FIG. 2, at the irradiation point 10, although the beam radius of the charged particle beam is r ₁₁ at time t ₁ , it changes to r ₁₃ at time t ₃ . That is, it can be seen that the beam radius of the charged particle beam varies from r _b to the maximum diameter r _b + Δr _b , and the beam diameter changes with time.

FIG. 3 shows a control state of the beam radius of the charged particle beam at the irradiation point 10 in the particle beam therapy apparatus 100 according to the first embodiment of the present invention. Figure 3 (a) shows the beam radius adjusted by the quadrupole electromagnet 2g, 2h, 2i before the charged particle beam passes through the scatterer 8, and Figure 3 (b) shows the quadrupole electromagnet 2g Changes in the radius of the charged particle beam after passing through the scatterer 8 after being adjusted at 2h, 2h, and 2i.

First, as shown in FIG. 3 (a), the beam diameter of the charged particle beam is reduced by the quadrupole electromagnets 2g, 2h, and 2i according to the beam diameter reduction factor c to be smaller than the target beam diameter. At this time, the irradiation point 10, the charged particle beam at the beam radius Although the times t ₁ r _21, but is changed to the time t ₃ r _23. That is, the beam radius of the charged particle beam varies from cr _b to the maximum radius c (r _b + cΔr _b ).

In addition, in a particle radiation therapy device, for example, when implementing uniform irradiation, "Guidelines for the Physical and Technical QA System of a Radiation Therapy Device (Particle Ray QA2015)" (http://www.jastro.or.jp/news/ detail.php? eid = 00371) discloses the specification that the flatness of the dose distribution in the target at the end of irradiation is ± 3%. From the point of view of the effect of the variation of the beam diameter, if the Gaussian beam is irradiated with σ = 3mm distribution, △ x, △ y = 3mm interval, and each point is the same amount, it will become uniform as shown in Figure 4. . Fig. 4 (a) shows the dose distribution (area Sa) when irradiation is performed under the above-mentioned conditions, and Fig. 4 (b) shows the outline of the dose on the BB line in Fig. 4 (a).

However, when only the spot beam in the center is reduced to σ = 2.76 mm, the center is raised, and uniform irradiation cannot be performed as shown in FIG. 5. Figure 5 (a) shows the dose distribution (area Sb) when only the central spot beam is set to σ = 2.76mm, and Figure 5 (b) shows the outline of the dose on the CC line in Figure 5 (a) . As can be seen from the figure, since the dose increase amount is 3%, it is necessary to suppress the variation of the beam diameter within about 8% (σ = 3mm ± 0.24mm).

Figure 6 shows the value of the maximum beam diameter when the beam diameter reduction factor is changed. The beam diameter reduction coefficient c represents the ratio of the beam diameter at the irradiation point when the beam diameter before reduction is set to 1. Set r _b = 3mm and △ r _b = 0.6mm. The vertical axis is the maximum beam diameter at the irradiation point when the scatterer is inserted. As shown in Figure 6, in order to meet the above specifications, the reduction factor must be limited to c = 0.6 or less.

The beam diameter of the charged particle beam is reduced by the quadrupole electromagnet 2g, 2h, 2i according to a predetermined beam diameter reduction factor c to be smaller than the target beam diameter, as shown in FIG. 3 (b). The scatterer 8 used after the scanning electromagnets 7a and 7b reduces the beam diameter of the charged particle beam smaller than the beam diameter of the target to the beam diameter of the target.

The scattering radius r _s of the scatterer 8 can be obtained from the following formula.

r _s = L <θ> L is the distance from the irradiation point to the scatterer, and <θ> is the scattering angle of the scatterer. At this time, the beam radius at the irradiation point after penetrating the scatterer is from √ ((cr _b ) ² + r _s ² ) to the maximum radius √ ((cr _b + c △ r _b ) ² + r _s ² ).

That is, when the thickness of the scatterer or the distance from the scatterer to the irradiation point is adjusted so that the initial beam radius becomes √ ((cr _b ) ² + r _s ² ) = r _b , the The beam radius of the irradiation point changes from r _b to the maximum radius √ (r _b ² + c ² Δr _b (2r _b + Δr _b )).

FIG. 7 shows the variation in the beam diameter of a conventional particle beam therapy apparatus using only four-pole electromagnets 2g, 2h, and 2i to control the beam diameter, and the beam diameter of the particle beam therapy apparatus 100 according to the first embodiment of the present invention. Example of a change of 15. Compared with the conventional particle beam therapy apparatus, it can be seen that the particle beam therapy apparatus 100 according to the embodiment of the present invention has a smaller change in the beam diameter.

In this way, after a predetermined beam diameter reduction factor c is set initially, and after the beam diameter of the charged particle beam is reduced to a small value by the quadrupole electromagnets 2g, 2h, 2i, a beam diameter that can be expanded to the target is selected. By setting the scatterer 8 together, the beam diameter can be easily stabilized.

As described above, the particle beam therapeutic apparatus 100 according to the first embodiment of the present invention reduces the beam diameter of the charged particle beam by the quadrupole electromagnets 2g, 2h, and 2i according to a predetermined beam diameter reduction coefficient c to a target beam. When the diameter is smaller, the scatterer 8 provided on the downstream side of the scanning electromagnets 7a and 7b is used to expand the beam diameter of the charged particle beam which has been reduced to be smaller than the target beam diameter to the target beam diameter. Therefore, the beam diameter can be easily stabilized. Furthermore, by suppressing variations in the beam diameter, irradiation can be performed according to a plan.

Embodiment 2.

In the first embodiment, the scatterer 8 is provided on the downstream side of the scanning electromagnets 7a, 7b. However, in the second embodiment, the scatterer 8 is provided on the upstream side of the scanning electromagnet.

FIG. 8 is a schematic diagram showing the configuration of a particle beam treatment apparatus 101 according to Embodiment 2 of the present invention. As shown in FIG. 8, the particle beam treatment apparatus 101 includes a scatterer 8 on the upstream side of the scanning electromagnets 7 a and 7 b and between the quadrupole electromagnet 2 i and the scanning electromagnet 7 a. The other components of the particle beam treatment apparatus 101 are the same as those of the particle beam treatment apparatus 100 according to the first embodiment, and the corresponding parts are denoted by the same reference numerals and descriptions thereof are omitted.

When the scatterer 8 is provided on the upstream side of the scanning electromagnets 7a and 7b, since the distance to the irradiation point 10 can be extended, a thinner scatterer can be used, and energy loss can be reduced.

As described above, the particle beam treatment apparatus 101 according to the second embodiment of the present invention reduces the beam diameter of the charged particle beam by a quadrupole electromagnet 2g, 2h, 2i according to a predetermined beam diameter reduction coefficient c to a target beam. When the diameter is smaller, the scatterer 8 provided on the upstream side of the scanning electromagnets 7a and 7b is used to expand the beam diameter of the charged particle beam reduced to a target beam diameter to the target beam diameter. Therefore, not only can the beam diameter be simply stabilized, but a thinner scatterer can also be used, and the energy loss can be reduced. In addition, it is possible to irradiate according to a plan by suppressing variations in the beam diameter.

Embodiment 3.

In the first and second embodiments, the beam diameter of the charged particle beam is reduced by the quadrupole electromagnets 2g, 2h, and 2i and then expanded by the scatterer 8. However, in the third embodiment, It is shown that the beam diameter is reduced by biasing the electromagnet instead of the quadrupole electromagnet.

Fig. 9 is a schematic diagram showing the structure of a particle beam therapeutic apparatus 102 according to a third embodiment of the present invention. As shown in FIG. 9, in the particle beam therapy apparatus 102, in order to deflect a charged particle beam, a four-pole electromagnet 2j, 2k, 2l and a deflection electromagnet 4h, 4i are provided at the downstream end of the transport system 31. In the irradiation system 42, the charged particle beam that is deflected by the deflection electromagnet 4i and reduced to a diameter smaller than the target beam diameter at the same time is directly passed through the scanning electromagnets 7a and 7b, and the scattering is adjusted by the scatterer 8 The beam diameter is increased to the target beam diameter and guided to the irradiation point 10. The other components of the particle beam treatment apparatus 102 are the same as those of the particle beam treatment apparatus 100 according to the first embodiment, and the corresponding parts are denoted by the same reference numerals and descriptions thereof are omitted.

Next, the operation of the particle beam treatment apparatus 102 according to the third embodiment of the present invention will be described using drawings. FIG. 10 is an explanatory diagram for explaining the action of the biased electromagnet 4i to reduce the beam diameter of the charged particle beam to a small size in the particle beam therapy apparatus 102. Fig. 10 (b) is a plan view of the deflection electromagnet 4i, and Fig. 10 (a) is an arrow sectional view taken along the line AA of Fig. 10 (b).

As shown in FIG. 10 (b), the charged particle beams D1, D2, and D3 are biased toward the electromagnet 4i, and the diameter of the charged particle beam is reduced to a small value by the convergence effect. This system is shown in Figure 10 (a). In the magnet 4i, the density of the magnetic flux M is adjusted in a transverse direction perpendicular to the traveling direction of the charged particle beam, so that the charged particle beams D1, D2, and D3 passing through the electromagnet 4i are converged.

Thereby, since the charged particle beam can be reduced by biasing the electromagnet 4i, a quadrupole electromagnet is not required in the irradiation system 42, and the device can be simplified.

As described above, the particle beam therapeutic apparatus 102 according to the third embodiment of the present invention is configured to reduce the beam diameter of the charged particle beam to a smaller beam diameter than the target beam diameter by a predetermined beam diameter reduction factor c by using the deflection electromagnet 4i. The scatterer 8 provided on the upstream side of the scanning electromagnets 7a and 7b can expand the beam diameter of the charged particle beam which has been reduced to be smaller than the beam diameter of the target to the target beam diameter. The beam diameter can be simply stabilized, and the device can be further simplified. In addition, it is possible to irradiate according to a plan by suppressing variations in the beam diameter.

In addition, the present invention may be combined with various embodiments within the scope of the invention, or modified or omitted as appropriate.

Claims (4)

A particle ray therapy device includes: a four-pole electromagnet to reduce a charged particle beam; a scanning electromagnet to scan the aforementioned charged particle beam in a direction orthogonal to a beam axis; and a scatterer, The charged particle beam scanned by the scanning electromagnet is reduced to a beam diameter smaller than the isocenter target beam diameter by the predetermined reduction factor by the quadrupole electromagnet, and then expanded to the isocenter target beam. Beam diameter. The particle beam treatment device according to item 1 of the scope of patent application, wherein the scattering system is provided on the upstream side of the scanning electromagnet. The particle beam treatment device according to item 1 of the scope of the patent application, wherein the scattering system is provided on a downstream side of the scanning electromagnet. The particle beam treatment device according to any one of claims 1 to 3, wherein the aforementioned reduction factor is 0.6 or less.