JPH10211292A - Charged particle irradiator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress semi-shadowed and improve accuracy of the shape of a target by installing a scatterer in an average value position of the distances from an irradiation position to the deflection focuses of respective deflection magnets. SOLUTION: A scatterer 3 is disposed in an average distance position of the distance of the deflection focus 8 of a first deflection magnet and the distance of the deflection focus 7 of a second deflection magnet 2, namely, the central position 10 between both focuses 8, 7. Such disposition of the scatterer 3 can suppress both of the semi-shadowed blur caused by the first deflection magnet 1 and the semi-shadowed blur caused by the second deflection magnet 2 so as to minimize the semi-shadowed blur of the irradiation point 5. On the contrary, when the scatterer 3 is disposed in the upper stream of the first deflection magnet 1, the semi-shadowed blur caused by the first deflection magnet can be suppressed, however, the distance between the deflection focus 8 of the second deflection magnet 2 and the scatterer 3 is enlarged so that the semi- shadowed blur caused by the second deflection magnet 2 is enlarged. The disposition of the scatterer in the center of the focuses of both deflection magnets 1, 2 can suppress the semi-shadowed blur, as being shown in this case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle irradiation apparatus for irradiating charged particles to respective irradiation targets for the treatment of cancer, sterilization of food, improvement of plant varieties, non-destructive inspection of mechanical structures, and the like. Things.

[0002]

2. Description of the Related Art When a high-energy charged particle beam generated by an accelerator or the like is used for treating cancer or the like, the charged particle beam is expanded to obtain a wide irradiation area, and the dose distribution is expanded to be uniform. The charged particle beam is formed into a shape of a target diseased part by a collimator, and the target part is irradiated. For example, in order to treat cancer with protons, heavy particles, and the like, in the case of protons, it is necessary to expand a beam having an energy of at most about 230 MeV to a diameter of about 20 cm. Then, the charged particle beam is shaped into a target shape by a collimator and irradiated to the affected part.

[0003] As a conventional technique for expanding a charged particle beam,
Japanese Unexamined Utility Model Publication No. 1-58200 discloses a charged particle beam passing through a scatterer, using a wobbler method of scanning a charged particle beam with two deflecting magnets, placing a scatterer upstream or downstream of the two deflecting magnets. It is described to enlarge.

[0004]

The source of the charged particle beam irradiated to the affected part, that is, the light source of the expanded charged particle beam is not a point light source but has a finite spread. For this reason, penumbra occurs at the periphery of the charged particle beam cut into the target shape by the collimator. Therefore, in order to form an extremely precise irradiation area, this penumbra must be minimized.

[0005] In the above-mentioned prior art, penumbra occurs in the scanning direction of the deflecting magnet located far from the scatterer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a charged particle irradiation apparatus capable of irradiating a charged particle beam having a precise target shape while suppressing penumbra.

[0007]

A feature of the present invention to achieve the above object is that the scatterer is provided at a position at an average distance from the irradiation position to the deflection focal point of each deflection magnet. According to this, the difference in distance between the deflecting focal point of each deflecting magnet and the scatterer is smaller than in the case where scatterers are installed upstream or downstream of a series of deflecting magnets, and the half caused by a magnet far from the scatterer is reduced. Since the shadow blur can be suppressed, the half shadow blur at the irradiation position can be extremely suppressed as a whole, and a more precise charged particle beam having a target shape can be irradiated.

[0008] Another feature of the present invention is that the scatterer is provided between two deflection magnets.
The distance between the two deflecting magnets and the scatterer is shortened, and penumbra caused by the respective deflecting magnets can be suppressed as compared with the case where the deflecting magnets are installed upstream or downstream of the two deflecting magnets. It can irradiate charged particle beams with various target shapes. In particular, the scatterer should be installed at an average distance between the distance from the irradiation position to the deflection focal point of one of the two deflection magnets and the distance from the irradiation position to the deflection focal point of the other deflection magnet. Thereby, the penumbra caused by both the bending magnets can be extremely suppressed, and a more precise charged particle beam having a target shape can be irradiated.

Another feature of the invention is that the at least one deflection magnet scans the scattered charged particle beam and comprises another scatterer that is scattered and re-scatters the scanned charged particle beam. It is in. According to this feature, penumbra caused by the two deflection magnets can be suppressed, a charged particle beam having a precise target shape can be irradiated, and the dose distribution can be adjusted with another scatterer.

Another feature of the present invention is that the motion detector detects the movement of the target, and the control device controls supply and stop of the charged particle beam to the charged particle irradiation device based on the detected movement of the target. It is in. According to this feature, even when the target moves, penumbra blur caused by the two deflection magnets can be suppressed, and a charged particle beam having a precise target shape can be irradiated according to the movement of the target.

Another feature of the present invention is that the bolus adjusts the range of the charged particle beam to the lower shape of the target, the range adjuster changes the energy of the charged particle beam to adjust the range, and the multi-leaf collimator adjusts the range. It is to variably shape a charged particle beam. According to this feature, even when the target is a complex three-dimensional object, penumbra is extremely small,
It is possible to irradiate the entire target with a charged particle beam having a precise shape corresponding to a change in the shape of the target.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows a charged particle irradiation apparatus according to a first embodiment of the present invention. The charged particle irradiation apparatus according to the present embodiment includes a first deflecting magnet 1, which deflects a charged particle beam transported from a beam transport system (not shown) in a direction X perpendicular to the traveling direction S, in the traveling directions S and X directions. It comprises a second deflecting magnet that deflects in the vertical direction Y, a scatterer 3 disposed between the first deflecting magnet and the second deflecting magnet, and a collimator 4 that shapes the charged particle beam into a target shape. The scatterer 3 is provided at a central position 10 between the deflection focal point 8 of the first deflection magnet 1 and the deflection focal point 7 of the second deflection magnet 2.

The charged particle beam is deflected by the first deflection magnet 1 in the X direction. The charged particle beam that has passed through the first deflecting magnet 1 is expanded by the scatterer 3. The expanded charged particle beam is deflected by the second deflection magnet 2 in the Y direction. Since the first deflecting magnet 1 and the second deflecting magnet 2 generate alternating magnetic fields whose phases are shifted from each other by 90 degrees, the expanded charged particle beam 9
Is the irradiation position 5 (the traveling direction S near the center of the target 6)
(Set in advance on a plane perpendicular to the plane) so as to draw a circle, and a uniform dose distribution can be formed at the irradiation position 5. The charged particle beam shaped into the shape of the target 6 by the collimator 4 is checked against the target 6.

When viewed from the irradiation position 5, the source of the charged particle beam is not a point but a finite size, so that the irradiation edge is irradiated outside the target shape formed by the collimator 4. This is penumbra.

In an irradiation apparatus using a deflecting magnet and a scatterer,
As the distance between the position of the scatterer and the deflecting focal point of the deflecting magnet is smaller, there is a property that the penumbra caused by the deflecting magnet is smaller.

The charged particle beam travels through the deflecting magnet in a circular motion, exits from the exit of the deflecting magnet at an angle θ with respect to the axis of the irradiation device, and moves linearly toward the target. This straight line is extended, and a point at which the axis of the irradiation device in the deflection magnet intersects is defined as a deflection focal point. Assuming that the distance from the exit of the deflection magnet to the deflection focal point is f, the radius of curvature of the deflection magnet is ρ, and the length of the deflection magnet is 1, the following equation is given.

[0017]

(Equation 1)

When the deflection amount of the deflection magnet is small, the deflection focal point is substantially at the center of the deflection magnet.

FIG. 2, FIG. 3, and FIG. 4 show the results of numerical analysis performed by changing the positional relationship between the first deflecting magnet, the second deflecting magnet, and the scatterer. For comparison, a case where the distance from the irradiation position 5 to the uppermost stream of the irradiation device is 3 m is taken as an example. Here, the range of penumbra is 80% of the peak dose.
Is defined as the distance decreasing from 20% to 20%.

As in the present embodiment, the central position 10 between the deflection focal point 7 of the first deflection magnet 1 and the deflection focal point 8 of the second deflection magnet 2
When the scatterer 3 is disposed at both sides, as shown in FIG. 2, both the penumbra blur caused by the first deflecting magnet 1 and the penumbra blur caused by the second deflecting magnet 2 can be suppressed, and the irradiation position can be reduced. 5 can be minimized.

When the scatterer 3 is arranged upstream of the first deflecting magnet 1, as shown in FIG. 3, penumbra 41 caused by the first deflecting magnet 1 is suppressed, Since the distance between the deflecting focal point 8 and the scatterer 3 increases, the penumbra 42 caused by the second deflecting magnet 2 increases.

When the scatterer 3 is arranged downstream of the second deflecting magnet 2, as shown in FIG. Since the distance between the deflecting focal point 7 and the scatterer 3 increases, the penumbra 41 caused by the first deflecting magnet 1 increases.

Therefore, according to the charged particle irradiation apparatus of the present embodiment, it is possible to irradiate a charged particle beam having a precise target shape while suppressing penumbra blur extremely small.

In this embodiment, an electromagnet is used to deflect the charged particle beam. However, a rotating magnetic field may be generated by rotating a permanent magnet.

When the deflecting focus of the deflecting magnet is not at the center of the deflecting magnet but is deviated upward and downward, or when there are three or more deflecting magnets, each of the deflecting magnets from the irradiation position to the deflecting focus of each deflecting magnet is different. By disposing the scatterer at the average position of the distance, penumbra blur caused by each magnet can be suppressed.

(Embodiment 2) FIG. 5 shows a charged particle irradiation apparatus used for cancer treatment according to a second embodiment of the present invention. In the present embodiment, the charged particle irradiation apparatus of the first embodiment, a respiration sensor 21 for detecting respiration of a patient, and a respiration pattern are obtained based on the detected respiration of the patient. Control device 2 to control supply and stop
2 is used.

When the patient breathes, the target 6, which is the affected part, moves in accordance with the breathing. The charged particle irradiation apparatus according to the present embodiment performs irradiation under the control of the control device 22 when the target 6 is at rest when the patient has finished inhaling or exhaling. Therefore, even when the target 6 moves in accordance with the breathing, the penumbra is suppressed to a very small value.
The target 6 can be irradiated with a charged particle beam having a precise target shape.

In this embodiment, the case where the charged particle beam is irradiated in synchronization with the patient's breathing has been described. However, it is possible to synchronize with the pulse other than the breathing. When the target moves, if the means for detecting the movement is used, ON / OFF of the irradiation can be controlled according to the movement.

(Embodiment 3) FIG. 6 shows a charged particle irradiation apparatus used for cancer treatment according to a third embodiment of the present invention. In the present embodiment, the charged particle irradiation apparatus of the first embodiment, a patient bolus 32 for adjusting the range of the charged particle beam 9 according to the lower shape of the target 6 which is an affected part, and the energy of the charged particle beam 9 And a range adjusting device 33 for changing the range. Further, instead of the collimator used in the first embodiment, a multi-leaf collimator 31 capable of changing a shape for cutting the charged particle beam 9 is used. Since the target 6, which is an affected part, is three-dimensional and has a different shape depending on the depth, when the charged particle beam 9 is scanned in the depth direction, the shape of the multi-leaf collimator 31 cutting off the charged particle beam 9 according to the change in shape. change. Therefore, the shape of the multi-leaf collimator 31 can be changed to the target 6 which is a complicated three-dimensional object, the penumbra can be kept extremely small, and the entire target 6 can be irradiated with the charged particle beam having the precise target shape.

In this embodiment, the range adjusting device 33 includes:
The energy and range of the charged particle beam 9 were changed by changing the superposed thickness of the two wedge-shaped charged particle beams 9 to change the energy and range. And the number of sheets may be changed.

(Embodiment 4) FIG. 7 shows a charged particle irradiation apparatus according to a first embodiment of the present invention. In the charged particle irradiation apparatus of the present embodiment, a scatterer 43 for further adjusting the dose distribution is arranged downstream of the second deflecting magnet of the charged particle irradiation apparatus of the first embodiment.

The charged particle beam is deflected by the first deflection magnet 1 in the X direction. The charged particle beam that has passed through the first deflecting magnet 1 is expanded by the scatterer 3. The expanded charged particle beam is deflected by the second deflection magnet 2 in the Y direction. Since the first deflecting magnet 1 and the second deflecting magnet 2 generate an alternating magnetic field having a phase shifted by 90 degrees from each other, the expanded charged particle beam 9 is scanned on the scatterer 43 so as to draw a circle, and the scatterer 43 is scanned. The transmitted charged particle beam 9 is further expanded. At the irradiation position 5, the charged particle beam 9 further expanded is scanned in a circular shape, and a uniform dose distribution can be formed. If the scatterer 43 is replaced with one having a different magnification, an arbitrary dose distribution can be obtained at the irradiation position 5.

The scatterer 43 further expands the charged particle beam expanded by the scatterer 3. Scatterer 4
3 is installed downstream of the second deflecting magnet, penumbra due to the scatterer 43 occurs, and the penumbra at the irradiation position 5 is smaller than in the case of the charged particle irradiation apparatus of the first embodiment. large. Therefore, if a scatterer 3 that forms a standard uniform dose distribution is used and the scatterer 43 is used for adjustment with a smaller magnification than the scatterer 3, the scatterer 43 and the two scatterers are used. Penguin blur caused by the deflection magnets 1 and 2 can be reduced.

Therefore, according to the charged particle irradiation apparatus of the present embodiment, it is possible to irradiate a charged particle beam having a precise target shape while suppressing penumbra and to adjust the dose distribution.

In this embodiment, the scatterer 43 is provided downstream of the second deflecting magnet, but may be provided upstream of the first deflecting magnet. However, also in this case, penumbra at the irradiation position 5 is larger than in the case of the charged particle irradiation apparatus of the first embodiment.

[0036]

According to the present invention, the scatterer is installed at the position of the average distance from the irradiation position to the deflection focal point of each deflecting magnet, so that the scatterer is installed upstream or downstream of a series of deflecting magnets. As a whole, penumbra at the irradiation position can be extremely suppressed, and the target can be irradiated with a charged particle beam having a more precise target shape.

Further, since the scatterer is provided between the two deflection magnets, penumbra caused by each of the deflection magnets is suppressed as compared with the case where the scatterer is installed upstream or downstream of the two deflection magnets. And can irradiate a charged particle beam with a precise target shape. In particular, the distance from the irradiation position to the deflection focal point of one of the two deflection magnets,
By installing the scatterer at the position of the average distance from the irradiation position to the deflection focal point of the other deflection magnet, penumbra caused by both deflection magnets can be extremely suppressed,
The target can be irradiated with a charged particle beam having a more precise target shape.

The at least one deflecting magnet scans the scattered charged particle beam, and is provided with another scatterer that scatters and scatters the scanned charged particle beam again. Can be suppressed, and a charged particle beam having a precise target shape can be irradiated, and the dose distribution can be adjusted by other scatterers.

Further, the motion detector detects the movement of the target, and the control device controls the supply and stop of the charged particle beam to the charged particle irradiation device based on the detected movement of the target, so that the target moves. Even in this case, penumbra caused by the two deflection magnets can be suppressed, and a charged particle beam having a precise target shape can be irradiated according to the movement of the target.

The bolus adjusts the range of the charged particle beam to the shape below the target, the range adjuster changes the energy of the charged particle beam to adjust the range, and the multi-leaf collimator variably changes the charged particle beam. By molding
Even when the target is a complicated three-dimensional object, penumbra can be kept extremely small, and the entire target can be irradiated with a charged particle beam having a precise shape corresponding to a change in the shape of the target.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a charged particle irradiation apparatus according to a first embodiment.

FIG. 2 is a diagram showing a result of calculating penumbra of an irradiation apparatus by the charged particle irradiation apparatus of the first embodiment.

FIG. 3 is a diagram illustrating a result of calculating penumbra when a scatterer is arranged upstream of a first deflection magnet and a second deflection magnet.

FIG. 4 is a diagram illustrating a result of calculating penumbra blur when a scatterer is arranged downstream of a first deflecting magnet and a second deflecting magnet.

FIG. 5 is a diagram illustrating a charged particle irradiation apparatus according to a second embodiment.

FIG. 6 is a diagram illustrating a charged particle irradiation apparatus according to a third embodiment.

FIG. 7 is a diagram illustrating a charged particle irradiation apparatus according to a fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... First deflection magnet, 2 ... Second deflection magnet, 3, 43 ... Scattering body, 4 ... Collimator, 5 ... Irradiation position, 6 ... Target,
7: deflection focus of the first deflection magnet, 8: deflection focus of the second deflection magnet, 9: charged particle beam, 10: center position, 21 ...
Respiratory sensor, 22: control device, 23: charged particle beam control signal, 31: multi-leaf collimator, 32: patient bolus, 33: range adjustment device, 41: penumbra caused by the first deflecting magnet, 42 ... Penguin blur caused by two bending magnets.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Suzuki 3-1-1, Sakaimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant

Claims (6)

[Claims] 1. A charged particle irradiation apparatus comprising: a plurality of deflection magnets for scanning a charged particle beam; a scatterer for scattering the charged particle beam; and a collimator for forming the scattered charged particle beam into a target shape. The charged particle irradiation apparatus, wherein the scatterer is provided at a position of an average distance from an irradiation position where the target is arranged to a deflection focal point of each of the deflection magnets. 2. A charged particle irradiation apparatus comprising: two deflecting magnets for scanning a charged particle beam; a scatterer for scattering the charged particle beam; and a collimator for forming the scattered charged particle beam into a target shape. The charged particle irradiation apparatus, wherein the scatterer is provided between the two deflection magnets. 3. The scatterer includes a distance from an irradiation position where the target is arranged to a deflection focal point of one of the two deflection magnets, and a deflection focal point of another deflection magnet from the irradiation position. The charged particle irradiation device according to claim 2, wherein the charged particle irradiation device is installed at an average distance from the distance to the charged particle irradiation device. 4. A charged particle irradiation apparatus comprising two deflection magnets for scanning a charged particle beam, a scatterer for scattering the charged particle beam, and a collimator for forming the scattered charged particle beam into a target shape. The at least one deflecting magnet scans the scattered charged particle beam and comprises another scatterer that is scattered and scatters the scanned charged particle beam again. Particle irradiation device. 5. A movement detector for detecting movement of the target, and a control device for controlling supply and stop of the charged particle beam to the charged particle irradiation device based on the detected movement of the target. The charged particle irradiation apparatus according to claim 1, wherein: 6. A collimator comprising: a bolus for adjusting a range of the charged particle beam to a shape below a target; and a range adjusting device for adjusting a range of the charged particle beam by changing energy of the charged particle beam. 2. The charged particle irradiation apparatus according to claim 1, wherein the device is a multi-leaf collimator that variably shapes the charged particle beam.