JPH06319813A - Rotational irradiation device for proton-beam treatment - Google Patents

Abstract

PURPOSE:To maintain the specified dose distribution of a radiation field and facilitate the adjustment of an irradiation system by arranging a thin scatterer in the beam inlet of the rational irradiation device of a proton-beam irradiation system. CONSTITUTION:This rational irradiation device is provided with the scatterer 1 disposed in the outlet of a beam transporting route 2 from an accelerator, a beam transporting system 10 for transporting the beam from the scatterer 1 and an irradiation field forming system 20 of the beam. This beam transporting system 10 is provided with bipolar deflection electromagnets 3, 4, 5 for refracting the beam and plural quadrupolar deflection electromagnets 6, 7, 8 for refracting the beam. The distributions in the phase spaces of horizontal and vertial directions are, thereupon, made almost the same after passage through the scatterer 1 if the transporting route for the beam on the upstream side of the scatterer 1 is adjusted to the same diameter in the horizontal and vertial directions just before the scatterer 1. As a result, the rotationally symmetrical beam is realized in the inlet of the rotational irradiation device and always the specified dose distribution is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proton beam irradiation system used for treating cancer and the like, and more specifically, for rotating a human body to irradiate a proton beam from an arbitrary direction. The present invention relates to a rotary irradiation device.

[0002]

2. Description of the Related Art Conventionally, a proton beam irradiation system for cancer treatment is
The world is still in the development stage, and various proposals have been made for the rotary irradiation device of the proton beam irradiation system, but few devices are actually operating.

FIG. 2 is a view schematically showing an example of a conventional proton irradiation system rotary irradiation apparatus. As shown in FIG. 2, the rotary irradiator is connected to a beam rotator 51 arranged in a proton beam (hereinafter referred to as beam) lead-out path from an accelerator (not shown).
Beam transport system 10 for transporting a beam from a beam, a scatterer 9 for enlarging an irradiation field by the beam from the beam transport system 10, and irradiation for shaping the scattered beam into an arbitrary shape according to the shape of the affected part And a field forming system 20. The beam transport system 10 includes two-pole deflection electromagnets 3, 4, and 5 that bend the beam, and a plurality of four-pole deflection electromagnets 6, 7, and 8 that linearly move the beam. The beam from the beam rotator 51 is transported by making the ends of these deflection magnets face each other. The beam from the irradiation field forming system 20 is applied to the affected area, which is the object of the beam. The rotary irradiation device is configured so as to rotate about the patient 30 as a whole.

By the way, usually, the distribution of the beam generated by the accelerator in the phase space is often not rotationally symmetric, and the distribution seen from the coordinate system fixed to the beam transport system 10 in the rotary irradiation device is rotated. It depends on the corner. This distribution is
Since the optical characteristics fixed to the beam transport system 10 are affected, when the patient 30 is finally irradiated, there is a difference in the dose distribution in the irradiation field depending on the rotation angle. In order to prevent this, a beam rotator 51 consisting of 6 to 7 rotatable quadrupole electromagnets is installed at the entrance of the rotary irradiation device. However, if the beam rotator 51 is installed, the shape becomes large, which is disadvantageous in terms of cost and space.

Therefore, in the facility currently in operation, as shown in FIG. 2, the influence is avoided by spreading the beam with the scatterer 9 for expanding the irradiation field, which is installed immediately before the patient 30. .

[0006]

However, in the conventional method using the scatterer 9, there is a possibility that the beam collides with the deflecting magnet and is lost in the beam transport system 10 depending on the rotation angle. If the beam utilization efficiency is improved by the development of heavy scatterers, it is considered that the dose distribution in the irradiation area will be affected.

As described above, in the rotary irradiation device of the proton beam irradiation system for cancer treatment, the distribution of the beam in the phase space changes due to the difference in the rotation angle, and this finally causes the dose distribution in the irradiation field. It appears as an error.

Here, in order to prevent an error in the dose distribution in the irradiation field, heretofore, between the accelerator and the irradiation system, or
A method has been proposed in which an energy degrader placed in the irradiation system is installed at the beam entrance of a rotary irradiation device.

However, in this method, since the beam spread varies depending on the amount of energy attenuation, it is not easy to adjust the irradiation system.

Therefore, a technical object of the present invention is to provide a rotary irradiation apparatus in which the dose distribution in the irradiation field is constant and the beam irradiation system can be easily adjusted.

[0011]

The present invention is characterized in that a thin scatterer is installed at the beam entrance of the rotary irradiation device instead of the energy degrader.

Here, in the present invention, the thin scatterer is preferably a lead plate having a thickness of several mm, but any metal having a large atomic weight may be used, and the lead plate is not limited to this.

[0013]

The scatterer according to the present invention does not need to change the thickness depending on the irradiation conditions, and always acts to spread the beam under the same conditions.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing the structure of a rotary irradiation device according to an embodiment of the present invention. As shown in FIG. 1, the rotating irradiation apparatus includes a scatterer 1 provided at an exit of a beam transport path 2 from an accelerator, a beam transport system 10 for transporting a beam from the scatterer 1, and a beam transport system 10 from the beam transport system 10. A scatterer 9 for expanding a beam irradiation field and a beam irradiation field forming system 20 are provided. The beam transport system 10 is
Two-pole deflection electromagnets 3, 4 and 5 for refracting the beam and a plurality of four-pole deflection electromagnets 6, 7, 8 are provided. The scatterer 1 is a lead plate having a thickness of about several mm.

The point that the rotary irradiation apparatus according to the embodiment of the present invention is different from the conventional example is that the beam rotator 51 is not used, but at the entrance of the rotary apparatus, that is, at one end of the beam transport path 2.
This is in that another scatterer 1 is provided.

Table 1 below shows the calculation results of changes in the beam phase distribution due to the scatterer 1 when the thickness is 2 mm and 6 mm.

[0018]

[Table 1]

As shown in Table 1 above, the beam diameter is
Almost no change occurs after passing through the scatterer 1, but the tilt component is greatly affected. It can be seen that the beams having different horizontal and vertical inclinations before the scatterer 1 have almost the same inclination after passing through the scatterer.

Therefore, in FIG. 1, if the transport path of the beam on the upstream side of the scatterer 1 is adjusted so as to have the same diameter in the horizontal and vertical directions before the scatterer 1, the scatterer 1
After passing, the distribution in the horizontal and vertical phase spaces can be made almost the same. As described above, a rotationally symmetric beam is realized at the entrance of the rotary irradiation device. This beam is
Even if the downstream beam transport system 10 is rotated, it is not affected, and a constant dose distribution is always maintained. The normal transportation path 2 is composed of a duct in a vacuum state, the vacuum system is closed at the entrance of the rotary irradiation device, and then the beam transportation system 10 is in the atmosphere. Therefore, the scatterer 1 can also be used as the vacuum sealing window of the transportation path 2. Further, although the scatterer 9 is used in the embodiment of the present invention, the scatterer 9 and the beam transport system 10 can be enlarged during irradiation, and the scatterer 9 in front of the patient can be omitted. It is possible.

[0021]

As described above, according to the present invention, it is possible to provide a rotary irradiation apparatus in which the dose distribution in the irradiation field is constant and the irradiation system can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a rotary irradiation device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing an example of a conventional rotary irradiation device.

[Explanation of symbols]

 1,9 Scatterer 2 Beam transport path 10 Beam transport system 20 Irradiation field forming system 3,4,5 Five-pole deflection electromagnet 6,7,8 Four-pole deflection electromagnet 51 Beam rotator

Claims (1)

[Claims] 1. A rotary irradiation device for a proton beam irradiation system, wherein a thin scatterer is arranged at the entrance of the rotary irradiation device.