JP2001061978A - Particle beam irradiation method and its device and particle beam treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the uniformity for the radiation does of depth of body direction that is added together all over the irradiation area. SOLUTION: A particle beam treatment device has a mechanism, which changes the energy of particle beam into multiple, and a ridge filter 11, which is for extending the Bragg peak at the dose distribution of particle beam that is formed in the depth direction in the body against each energy. For the particle beam treatment device, the shape function of each rod, which consists the ridge filter 11, has an inflection point from the minimum of thickness position to the maximum position and has the small ridge filter 11 that has the distance that is from the maximum position to the inflection point is smaller that the distance that is from the minimum position of the thickness to the inflection point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for three-dimensionally irradiating a particle beam emitted from a particle accelerator.
The present invention relates to a particle beam therapy system using a three-dimensional irradiation device.

[0002]

2. Description of the Related Art In recent years, particle beam therapy using protons and heavy particles has attracted attention as a method for treating cancer, which accounts for about one third of the causes of death in Japan. In this treatment method, by irradiating a cancer cell with a proton beam or a heavy particle beam emitted from an accelerator, it is possible to kill only the cancer cells without substantially affecting normal cells.

[0003] Particle beam therapy methods currently used include:
This is a method called a two-dimensional wobble method or a double scatterer method. In these two-dimensional irradiation methods, the irradiation area can be limited by using a collimator in the direction perpendicular to the beam axis, but the irradiation area cannot be accurately limited in the beam axis direction according to the affected part. There is a problem.

Therefore, as a more advanced treatment method of particle beam therapy, a method of aiming cancer cells with higher accuracy by irradiating an affected part in the body three-dimensionally has been proposed. A typical one of the three-dimensional irradiation methods is a treatment method in which a treatment site is virtually cut into three-dimensional lattice points and irradiation is performed, and is called a three-dimensional spot scanning method.

[0005] By performing a three-dimensional irradiation method such as the three-dimensional spot scanning method, it is possible to accurately adjust the beam axis direction to the affected part, and it is possible to adjust the normal affected part as compared with the conventional two-dimensional irradiation method. Exposure to radiation can be suppressed.

Here, a three-dimensional irradiation apparatus for performing cancer treatment by the three-dimensional spot scanning method will be described with reference to the drawings.

FIG. 14 is a schematic configuration diagram of a three-dimensional irradiation apparatus for three-dimensional spot scanning arranged in a treatment room. In the figure, 1 is a treatment bed, and 2 is a three-dimensional irradiation device. The three-dimensional irradiation device 2 includes a scanning magnet 3
a, 3b, a dose monitor 4, a position monitor 5, a ridge filter 6, and a range shifter 7.

Next, the function of each device of the three-dimensional irradiation apparatus shown in FIG. 14 will be described.

The scanning magnets 3a and 3b scan the spot beam incident on the magnets at a point (X, Y) on a plane perpendicular to the beam axis in the affected part of the body.

The range shifter 7 controls the position (Z) in the beam axis direction in the affected part of the body. This range shifter 7 is composed of an acrylic plate having a plurality of thicknesses.
By combining these acrylic plates, the beam energy passing through the range shifter 7, that is, the in-vivo range can be changed stepwise. Control of the in-vivo range in the range shifter 7 is generally switched at regular intervals.

The dose distribution of the monoenergetic particle beam in the body depth direction has a very sharp peak (hereinafter referred to as Bragg peak) distribution near the body range as shown in FIG. Thus, the in-vivo range of the monoenergetic particle beam is expanded so as to correspond to the interval of the in-vivo range switched by the range shifter 7.

Here, a ridge filter 6 for three-dimensional irradiation
Is formed in a shape in which a plurality of bar pieces made of aluminum are arranged as shown in FIG. Each bar has an isosceles triangular shape, and the thickness in the beam axis direction changes at a constant rate in the vertical direction of the beam.
In practice, the bar piece is formed into an isosceles triangular shape by processing it into a fine step shape for ease of machining.

FIG. 17 shows a dose distribution per slice in which the Bragg peak is expanded by the ridge filter 6.

The dose monitor 4 is for measuring the dose to be irradiated into the body, and the position monitor 5 is for checking whether the beam position scanned by the scanning magnets 3a and 3b is at the correct position. belongs to.

Using these irradiation devices, three-dimensional irradiation is performed by the following method.

First, the affected part is virtually divided into a plurality of slices with respect to the beam axis, and the incident energy of the particle beam and the acrylic plate thickness in the range shifter 6 are selected according to the position of the deepest slice.

Next, the incident energy of the particle beam according to the shape of the affected part in the deepest slice and the number n and the position (Xi, Yi) [i = 1 to n] of irradiating the spot beam according to the shape of the affected part in the range shifter 6 are shown below. The positions (Xi, Yi) are selected by the scanning magnets 3a, 3b.
Is irradiated.

In the scanning magnets 3a and 3b, the energy distribution of the monoenergetic particle beam is expanded by the ridge filter 6 so that the in-vivo range distribution corresponds to the slice width. The irradiation dose at the position (Xi, Yi) on this slice is monitored by the dose monitor 4, and when the irradiation of the predetermined dose is detected, the beam is stopped, and the scanning magnets 3a and 3b irradiate the next position ( Xi + 1, Yi + 1). When irradiation of all points in this slice is completed, the acrylic thickness in the range shifter 7 is changed, and irradiation of the next slice is performed. By repeating this sequentially for each slice, irradiation is performed three-dimensionally.

By irradiating the affected part in the body three-dimensionally as described above, it becomes possible to perform the irradiation in conformity with the affected part with higher accuracy as compared with the conventional two-dimensional irradiation method. .

However, the three-dimensional irradiation method such as the three-dimensional spot scanning method has the following problems.

In the ridge filter 6 as shown in FIG. 16, the expansion of the Bragg peak is weighted with a constant value in the depth direction of the body, and as shown in FIG. Has a constant dose. However, when these are added over all slices, the irradiation dose distribution becomes jagged as shown in FIG. This is because the dose on the shallow side of the body is gentle with respect to the Bragg peak, and is affected by slice irradiation on the deeper side.

Here, an example of irradiation by the three-dimensional spot scanning method has been described. However, such a problem is caused by a method of performing three-dimensional irradiation using a ridge filter, for example, a three-dimensional wobble method or a three-dimensional double scatterer method. A similar problem arises also in the above.

[0023]

As described above, in the conventional three-dimensional irradiation method using the ridge filter, uniformity of the irradiation dose distribution in the body depth direction added over the entire irradiation area cannot be obtained. There was a problem.

The present invention has been made in view of the above circumstances, and has a particle beam irradiation method capable of improving the uniformity with respect to the irradiation dose in the body depth direction added over the entire irradiation area. And an irradiation device for the same.

[0025]

According to the present invention, in order to achieve the above object, a particle beam irradiation method and apparatus and an irradiation therapy apparatus are constituted by the following means.

According to a first aspect of the present invention, a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is enlarged, and after one irradiation is performed for a predetermined time, the energy of the particle beam is reduced. In the particle beam irradiation method in which the irradiation is performed in the depth direction of the body by switching and sequentially switching the Bragg peak, the Bragg peak is weighted asymmetrically in the depth direction, and the irradiation is performed by enlarging the Bragg peak.

According to a second aspect of the present invention, a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is enlarged, and after irradiating for a certain time, a scanning magnet is scanned to set an irradiation position. In the three-dimensional irradiation particle beam irradiation method of performing irradiation by switching the energy of the particle beam after repeating this plural times and sequentially switching the energy, the Bragg peak is weighted asymmetrically in the depth direction. The irradiation is performed by enlarging the Bragg peak.

According to a third aspect of the present invention, a particle beam is expanded by a wobble magnet, and at the same time, a Bragg peak in a dose distribution of the particle beam formed in a depth direction in the body is expanded to make one irradiation constant. In the three-dimensional irradiation particle beam irradiation method in which the energy of the particle beam is switched after performing time and the irradiation is sequentially repeated, the Bragg peak is expanded asymmetrically in the depth direction by weighting the Bragg peak asymmetrically. Irradiation.

According to a fourth aspect of the present invention, a particle beam is expanded by a scatterer, and at the same time, a Bragg peak in a dose distribution of the particle beam formed in a depth direction in the body is expanded to make one irradiation constant. In the three-dimensional irradiation particle beam irradiation method in which the energy of the particle beam is switched after performing time and the irradiation is sequentially repeated, the Bragg peak is expanded asymmetrically in the depth direction by weighting the Bragg peak asymmetrically. Irradiation.

According to a fifth aspect of the present invention, a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is expanded, and after one irradiation is performed for a predetermined time, the energy of the particle beam is reduced. Switching, in the particle beam irradiation method of irradiating in the body depth direction by sequentially switching the Bragg peak, the expansion of the Bragg peak is the depth of the Bragg peak in the particle beam transport device from the particle beam accelerator to the particle beam irradiation device The weighting is performed asymmetrically in the direction.

According to a sixth aspect of the present invention, a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is enlarged, and after irradiating for a certain time, a scanning magnet is scanned to determine an irradiation position. In the three-dimensional irradiation particle beam irradiation method in which the energy of the particle beam is switched after repeating this plural times, and the energy is sequentially switched, the Bragg peak is expanded from the particle accelerator to the particle beam. In the particle beam transport device up to the irradiation device, the Bragg peak is weighted asymmetrically in the depth direction.

According to a seventh aspect of the present invention, in the particle beam irradiation method according to any one of the first to sixth aspects of the present invention, the weighted body position is Zm, When the shallow side is Zf and the deep side is Ze among body positions that are half of the maximum value of | Ze−Z
m | <| Zf-Zm |

According to an eighth aspect of the present invention, there is provided a mechanism for switching the energy of a particle beam to a plurality of particles, and expanding a Bragg peak in a dose distribution of the particle beam formed in a depth direction in the body for each energy. The ridge filter is provided with a plurality of bar pieces arranged side by side, and the shape function of each bar piece has an inflection point from the minimum thickness position to the maximum thickness position. Have
In addition, the distance from the minimum thickness position to the inflection point is smaller than the distance from the maximum thickness position to the inflection point.

According to a ninth aspect of the present invention, there is provided a scanning magnet for scanning a particle beam, a mechanism for switching a plurality of energy of the particle beam, and formed in the depth direction in the body for each energy. In a three-dimensional irradiation particle beam irradiation apparatus having a ridge filter for enlarging a Bragg peak in a particle beam dose distribution, the ridge filter includes a plurality of bar pieces arranged side by side, and a shape of each bar piece. The function has an inflection point from the minimum thickness position to the maximum thickness position, and the distance from the minimum thickness position to the inflection point is smaller than the distance from the maximum thickness position to the inflection point It is constituted in.

According to a tenth aspect of the present invention, there is provided a scatterer for expanding a particle beam two-dimensionally, a mechanism for switching a plurality of energies of the particle beam, and a depth direction in the body for each energy. A ridge filter for enlarging the Bragg peak in the dose distribution of the particle beam formed in the particle beam irradiation apparatus for three-dimensional irradiation, wherein the ridge filter includes a plurality of bar pieces arranged side by side; The shape function of the bar has an inflection point from the minimum thickness position to the maximum thickness position, and the distance from the minimum thickness position to the inflection point is greater than the distance from the maximum thickness position to the inflection point. Is also reduced.

According to an eleventh aspect of the present invention, in the particle beam irradiation apparatus according to any one of the eighth to tenth aspects, a range shifter is provided as a mechanism for switching the energy of the particle beam to a plurality. Used.

According to a twelfth aspect of the present invention, there is provided an accelerator for accelerating a particle beam, a particle beam irradiation device for irradiating a particle beam, and a device for transporting a particle beam from the accelerator to the particle beam irradiation device. In a particle beam therapy device equipped with a particle beam transport device, the accelerator, the particle beam irradiation device, and the particle beam transport device are provided with a mechanism for switching the energy of the particle beam to a plurality of particles. A ridge filter for expanding a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is disposed in the particle beam transport device.

The invention corresponding to claim 13 is the invention of claim 12
In the particle beam therapy apparatus according to the present invention, the ridge filter has a plurality of rods arranged side by side, and the shape function of each rod has an inflection point from a position having a minimum thickness to a position having a maximum thickness, In addition, the distance from the minimum thickness position to the inflection point is smaller than the distance from the maximum thickness position to the inflection point.

According to a fourteenth aspect of the present invention, there is provided an accelerator for accelerating a particle beam, a particle beam irradiation device for irradiating a particle beam, and a device for transporting a particle beam from the accelerator to the particle beam irradiation device. In a particle beam therapy device equipped with a particle beam transport device, the accelerator, the particle beam irradiation device, and the particle beam transport device are provided with a mechanism for switching the energy of the particle beam to a plurality of particles. An energy distribution expansion plate having an uneven thickness for expanding a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is disposed in the particle beam transport device.

The invention corresponding to claim 15 is claim 14.
In the particle beam therapy apparatus according to the invention, the energy distribution enlarging plate is disposed in the particle beam transport apparatus.
Between the two deflection magnets.

The invention corresponding to claim 16 is claim 15.
In the particle beam therapy system according to the invention, the thickness of the energy distribution expanding plate is defined as a direction in which the beam is deflected by the deflecting magnet disposed on the accelerator side, and the thickness of the beam is larger than the thickness of the beam central axis. Also thicken.

Therefore, according to the invention as described above, the expanded Bragg peak in each slice becomes a distribution having a gentle shape, and the total irradiation dose obtained by adding these distributions is one in the depth direction. A highly uniform distribution can be obtained.

Further, in the weighting of the Bragg peak in the depth direction given by the ridge filter, the weighting on the side deeper in the body than the Bragg peak can make the expansion smaller than on the side shallower in the body. Therefore, the total irradiation dose obtained by adding the slices can have a high uniformity in the depth direction and a sharp irradiation dose distribution at the deepest part of the irradiation region.

[0044]

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

FIG. 1 shows a first embodiment of a three-dimensional spot scanning method according to the present invention.
In the schematic configuration diagram of the three-dimensional irradiation apparatus, the same components as those in FIG. 14 shown in the conventional example are denoted by the same reference numerals.

In FIG. 1, reference numeral 1 denotes a treatment bet;
0 is a three-dimensional irradiation device. This three-dimensional irradiation device 10
Is composed of scanning magnets 3a and 3b, a dose monitor 4, a position monitor 5, a ridge filter 11, and a range shifter 7.

Next, the function of each device of the three-dimensional irradiation apparatus shown in FIG. 1 will be described.

The scanning magnets 3a and 3b scan the spot beam B incident on the magnets at a point (X, Y) on a plane perpendicular to the beam axis in the affected part of the body.
The scanning magnet 3a scans the beam in the X direction, and the scanning magnet 3b scans the beam in the Y direction.

The range shifter 7 controls the position (Z) in the beam axis direction in the affected part of the body. The range shifter 7 is composed of an acrylic plate having a plurality of thicknesses. By combining these acrylic plates, the beam energy passing through the range shifter 7, that is, the in-vivo range can be changed stepwise.

The ridge filter 11 expands the in-vivo range of the monoenergetic particle beam so as to correspond to the interval of the in-vivo range switched by the range shifter 7.

FIG. 2 shows a ridge filter 11 for three-dimensional irradiation.
FIG. The ridge filter shown in the figure is configured by arranging a plurality of bar pieces made of aluminum. Here, the following coordinate system will be used to represent the shape of the ridge filter.

In the figure, a coordinate system is used in which the X-axis is the direction in which the bar pieces are arranged and the Z-axis is the thickness direction of the bar pieces, the position where the thickness of the bar pieces becomes the first is Xs, and the thickness becomes the maximum. Let the position be Xl.

In the example shown in the figure, the thickness is zero (Z = 0).
X = Xs. Here, the thickness function Z (X) expressed as a function of the position X is expressed as Xl from the position Xs.
Have an inflection point Xp. Further, the positions Xs, X
1 and the inflection point Xp have a relationship of | Xp−Xs | <| X1−Xp |. Here, the inflection point is a thickness function Z (X)
This is a position defined by d ² Z / dX ² = 0 with respect to the differential expression by X.

Using these irradiation devices, three-dimensional irradiation is performed by the following method.

First, the affected part is virtually divided into a plurality of slices with respect to the beam axis, and the incident energy of the particle beam and the thickness of the acrylic plate in the range shifter 7 are selected according to the position of the deepest slice.

Next, according to the shape of the affected part in the deepest slice, the point n and the position (Xi, Y
i) [i = 1 to n] is selected and the scanning magnets 3a,
3b irradiates these positions (Xi, Yi).
At the time of passing through the scanning magnets 3a and 3b, the energy distribution of the particle beam B having a single energy is expanded by the ridge filter 11 so that the in-vivo range distribution corresponds to the slice width. The position on this slice (X
The irradiation dose of i, Yi) is monitored by the dose monitor 4,
When the irradiation of the predetermined dose is detected, the beam is stopped, and the irradiation position is changed to the next position (Xi + 1, Yi + 1) on the same slice by the scanning magnets 3a and 3b. When irradiation of all points in this slice is completed, the acrylic thickness in the range shifter 7 is changed, and irradiation of the next slice is performed. By repeating this sequentially for each slice, 3
Irradiation is performed dimensionally.

FIG. 3 shows the ridge filter 11 of the present embodiment.
Is a weighting function of the Bragg peak when the Bragg peak is expanded by using, and a depth distribution of the dose in which the Bragg peak is expanded for one slice. At this time, the weighting on the shallow side and the weighting on the deep side have an asymmetric distribution with respect to the position Zm at which the weight becomes maximum (or the average position thereof when there are a plurality of positions at which the weight becomes maximum). In the case of FIG. 3, when the shallow side is Zf and the deep side is Ze among the in-vivo positions where the maximum value of the weight is half, | Ze−Zm | <| Zf−Zm |

Here, the dose distribution per slice in which the Bragg peak is enlarged has a smooth shape as shown in FIG. 3 and a sharper shape on the deeper side than on the shallower side than the Bragg peak.

FIG. 4 shows the dose distribution in the depth direction of the total dose obtained by adding the dose distribution obtained by enlarging the Bragg peak per slice shown in FIG.

As can be seen from the figure, in the irradiation area, a uniform dose distribution in the depth direction with high uniformity and a sharpness at the deepest part of the irradiation area can be obtained.

Therefore, by using the three-dimensional irradiation apparatus having the above-described configuration, the irradiation accuracy is improved for the affected part and the deepest part of the affected part is well cut, so that the irradiation of the normal tissue with less exposure is performed. It can be performed.

FIG. 5 shows a third embodiment of a three-dimensional spot scanning method according to the present invention, which is arranged in a treatment room.
In the schematic configuration diagram of the three-dimensional irradiation apparatus, the same components as those in FIG. 14 shown in the conventional example are denoted by the same reference numerals.

In FIG. 5, reference numeral 1 denotes a treatment bet;
Reference numeral 2 denotes a three-dimensional irradiation device. This three-dimensional irradiation device 12
Is composed of a scatterer 13, wobble magnets 14a and 14b, a dose monitor 4, a position monitor 5, a ridge filter 11, a range shifter 7, and a multi-leaf collimator 15.

Next, the function of each device of the three-dimensional irradiation apparatus shown in FIG. 5 will be described.

The scatterer 13 functions to expand the beam width of the incident spot beam B by a scattering phenomenon inside the scatterer.

The wobbler magnets 14a and 14b are scatterers 1
The wobble magnet 14a scans the beam in the X direction by scanning the beam expanded in step 3 at a point (X, Y) on a plane perpendicular to the beam axis in the affected part of the body.
4b scans in the Y direction. This X-direction wobble magnet 14a
The current value flowing through these and the Y-direction wobbler magnet 14b fluctuates according to a sine function at the same frequency, but the phases of the currents of the X-direction wobbler magnet and the Y-direction wobbler magnet are maintained at 90 degrees.

For example, if these frequencies are both 31 Hz
Since the phase of the current is shifted by 90 degrees, the beam emitted from the wobble magnet is a beam that rotates circularly at 31 Hz. For example, over a period of one second, the integrated beam shape becomes a disk-like shape with respect to the center of the beam axis.

Here, the beam expanded by the scatterer 13 is scanned by the wobbler magnets 14a and 14b.
Even if the spot beam scanned in 4b is enlarged by the scatterer 13, a beam having the same shape can be obtained.

The range shifter 7 is composed of an acrylic plate having a plurality of thicknesses. By combining these acrylic plates, the beam energy passing through the range shifter can be reduced.
That is, the in-vivo range can be changed stepwise.

The multi-leaf collimator 15 is composed of a plurality of iron plates. The iron plates are inserted from both sides with respect to the beam axis, and depending on the position, the beam expanded in a disk shape is limited to an arbitrary shape. Things. Multileaf collimator 1
The multi-leaf collimator 15 is deformed so that the beam shape passing through 5 matches the shape of the affected part of the patient. The deformation of the multi-leaf collimator 15 is performed for each acrylic plate thickness of the range shifter 7, that is, for each in-vivo range, and the irradiation area is adjusted to the shape of the affected part.

The shape of the ridge filter for three-dimensional irradiation used in the second embodiment is the same as that of the first embodiment as shown in FIG.

Using these irradiation devices, three-dimensional irradiation is performed by the following method.

First, the affected part is virtually divided into a plurality of slices with respect to the beam axis, and the incident energy of the particle beam and the acrylic plate thickness in the range shifter 7 are selected according to the position of the deepest slice.

Next, the multi-leaf collimator 15 is deformed according to the shape of the affected part in the deepest slice. The spot beam is expanded into a circular shape by the scatterer 13 and the wobble magnets 14a and 14b, but is further transformed by the multi-leaf collimator 15 into a beam conforming to the shape of the affected part in this slice, and irradiated to the affected part.

In the wobbler magnets 14a and 14b, the energy distribution of the particle beam having a single energy is expanded by the ridge filter 11 so that the in-vivo range distribution corresponds to the slice width.

The irradiation dose to the body is monitored by the dose monitor 4, and when the irradiation of the predetermined dose is detected, the beam is stopped, the acrylic thickness in the range shifter 7 is changed, and the next slice irradiation is performed. Irradiation is performed three-dimensionally while repeating this process.

The dose distribution in the depth direction obtained by the three-dimensional irradiation apparatus shown in the second embodiment is similar to that shown in the first embodiment. That is,
The depth distribution of the dose in which the Bragg peak is expanded with respect to one slice is smooth as shown in FIG. 3, and has a sharper shape on the deeper side than on the shallower side than the Bragg peak. The dose distribution in the depth direction with respect to the total dose obtained by adding these to all slices has a high uniformity in the irradiation area and a sharp distribution at the deepest part of the irradiation area.

Therefore, by using the three-dimensional irradiation apparatus having the above-described configuration, the affected part can be accurately cut and the deepest part of the affected part can be cut easily. Can be.

FIG. 6 shows a third embodiment of a three-dimensional spot scanning method according to the present invention.
In the schematic configuration diagram of the three-dimensional irradiation apparatus, the same components as those in FIG. 14 shown in the conventional example are denoted by the same reference numerals.

In FIG. 6, reference numeral 1 denotes a treatment bet;
Reference numeral 6 denotes a three-dimensional irradiation device. This three-dimensional irradiation device 16
Comprises a double scatterer 17, a dose monitor 4, a position monitor 5, a ridge filter 11, a range shifter 7, and a multi-leaf collimator 15.

Next, the function of each device of the three-dimensional irradiation apparatus shown in FIG. 6 will be described.

The double scatterer 17 functions to expand the beam width of the spot beam B incident on the scatterer by a scattering phenomenon inside the scatterer. Here, the scatterers are arranged in a double manner, and the beam diameter can be further enlarged as compared with the case of a single scatterer, so that the same action as the wobbler magnet in the second embodiment can be performed.

The range shifter 7 is composed of a plurality of acrylic plates. By combining these acrylic plates, the beam energy passing through the range shifter 7, that is, the in-vivo range is changed stepwise.

The multi-leaf collimator 15 is composed of a plurality of iron plates. The iron plates are inserted from both sides with respect to the beam axis, and depending on the position, the beam expanded in a disk shape is limited to an arbitrary shape. Is what you do.

The shape of the ridge filter for three-dimensional irradiation used in the third embodiment is the same as that of the first embodiment as shown in FIG.

Using these irradiation devices, three-dimensional irradiation is performed by the following method.

First, the affected part is virtually divided into a plurality of slices with respect to the beam axis, and the incident energy of the particle beam and the acrylic plate thickness in the range shifter 7 are selected according to the position of the deepest slice.

Next, the multi-leaf collimator 15 is deformed according to the shape of the affected part in the deepest slice. Double scatterer 17
, The spot beam is expanded into a circular shape, and the multi-leaf collimator 15 transforms the spot beam into a beam that matches the shape of the affected part in this slice, and irradiates the affected part with the beam. The particle beam having a single energy in the double scatterer 17 has its energy distribution expanded by the ridge filter 11 so that the in-vivo range distribution corresponds to the slice width.

The irradiation dose to the body is monitored by the dose monitor 4, and when the irradiation of the predetermined dose is detected, the beam is stopped, the acrylic thickness in the range shifter 7 is changed, and the next slice irradiation is performed. By repeating this sequentially, irradiation is performed three-dimensionally.

The dose distribution obtained in the three-dimensional irradiation apparatus shown in the third embodiment is similar to that shown in the first embodiment. That is,
The depth distribution of the dose in which the Bragg peak is expanded with respect to one slice is smooth as shown in FIG. 3, and has a sharper shape on the deeper side than on the shallower side than the Bragg peak. The dose distribution in the depth direction with respect to the total dose obtained by adding these to all the slices has high uniformity in the irradiation region and has a sharp distribution at the deepest part of the irradiation region.

Therefore, by using the three-dimensional irradiation apparatus having the above-described structure, the affected part can be precisely cut and the deepest part of the affected part can be cut easily. Can be.

In the above-described first to third embodiments, an example using a ridge filter having a shape as shown in FIG. 2 has been described. However, a ridge filter having a shape as shown in FIG. May be used.

In FIG. 7, the position X at which the thickness is minimized
d from s to position Xr²Z / dX ²= 0, ie slope
Is constant. In this case, the slope is constant
The center position of the range is considered as Xp. Figure 7 Ridge Fill
When the weighting function is used, the weighting function
Where the maximum is
Weighting is zero on the deeper side and shallower on the
Then it is slowly decreasing. In other words, half the maximum value of the weight
Of the body positions that are divided, the shallow side is Zf and the deep side is Ze
| Ze-Zm | <| Zf-Zm | is satisfied. Even in such a case,
Depth for the total dose obtained by adding
The directional dose distribution is highly uniform in the irradiation area, and
A sharp distribution at the deepest part of the irradiation area is obtained.

In the first to third embodiments described above, the inflection point for the shape of the ridge filter is set to d ² Z for the differential function of the thickness function Z (X) by X. / DX ² = 0. However, in reality, the bar piece is processed and manufactured in a fine step shape because of the ease of machining, and the above definition may not be possible.

Therefore, in such a case, the thickness function Z
Instead of (X), the center of the step processed in steps is
i, zi), and Δz (i) = [z (i) −z (i−
1)], Δx (i) = [x (i) −x (i−1)]. Then, [Δz (i + 1) / Δx (i + 1) −Δz
(I) / Δx (i)] / position x at which Δx (i) becomes zero
i is defined as an inflection point Xp. If there are two or more positions that become zero, the average position of these positions is defined as an inflection point Xp. When there is no zero position, [Δz (i + 1) /
Δx (i + 1) −Δz (i) / Δx (i)] / Δx
The position xi where the sign changes when (i) is sequentially calculated for i is defined as an inflection point Xp.

The shape of the ridge filter can take any shape other than the shapes shown in FIGS. 2 and 7, as long as the shape corresponds to the shape defined above.

Further, the first to third embodiments described above.
In the embodiment, the spot scanning method,
Although the three-dimensional irradiation method by the Wobble method and the double scattering method has been described, other methods can be similarly implemented as long as the method is a three-dimensional irradiation method.

FIG. 9 shows a third embodiment for a three-dimensional spot scanning method according to a fourth embodiment of the present invention.
It is a schematic configuration diagram of a particle beam therapy device using a three-dimensional irradiation device,
1 are given the same reference numerals.

In FIG. 9, reference numeral 20 denotes a treatment room, 21 denotes a particle beam transport device for transporting a beam from a particle beam acceleration ring (not shown) to the treatment room 20, and 1 denotes a treatment disposed in the treatment room 20. The bed 22 is a three-dimensional irradiation device.

Here, the particle beam transport device 21 is, for example, 2
Two deflection magnets 23, 24, two triple focusing magnets 25, 2
6. In addition, the three-dimensional irradiation device 22
It comprises scanning magnets 3a and 3b, a dose monitor 4, a position monitor 5, and a range shifter 7.

In the fourth embodiment, the ridge filter 11 having the shape shown in FIG. 2 is disposed between the deflecting magnet 24 and the triple focusing magnet 26 of the particle beam transport device 21.

In the present embodiment, each device of the three-dimensional irradiation apparatus and its function are the same as those in the first embodiment, and therefore the description thereof will be omitted.

In this embodiment, the ridge filter 11 is arranged in the particle beam transport device 21. The advantages at this time are as follows.

The ridge filter 11 has a spot beam B
The thickness of the particle beam passing through the aluminum, which is the ridge filter material, varies depending on the location where the particle beam passes through the ridge filter, and acts to broaden the energy distribution of the passing beam.

When the ridge filter is very close to the affected part,
The energy of the beam applied to the diseased part is directly projected on the diseased part in the shape of the ridge filter, and the diseased part becomes a stripe-shaped internal range distribution. For example, the stripe pattern of the beam leaking from the gap between the rod pieces of the ridge filter is directly reflected on the affected part.

This is because if the ridge filter and the affected part are separated from each other by a certain distance, the image obtained by the ridge filter is spatially uniformed, and the problem disappears. However, if the distance is too large, the affected part is affected by the scattering of the ridge filter. The diameter of the beam irradiated to the beam is enlarged, and the cut of the irradiation dose in the direction perpendicular to the beam axis deteriorates.

Therefore, the arrangement position of the ridge filter needs to be optimized, but the arrangement position is often limited by interference with other irradiation equipment, for example, a range shifter.

However, when the ridge filter 11 is arranged in the particle beam transport device 21 as shown in FIG. 9, the distance between the ridge filter and the affected part can be kept sufficiently large, and the beam scattered by the ridge filter can be maintained. Is converged by the converging magnet, so that it is possible to suppress an increase in the width of the beam irradiated to the affected part.

Further, in the present embodiment, the bar piece constituting the ridge filter 11 has an inflection point Xp between the positions Xs and Xl, and furthermore, between the positions Xs and Xl and the inflection point Xp, | Xp-Xs | <| X1-Xp |.

Accordingly, the distribution in the depth direction of the dose in which the Bragg peak is expanded for one slice is smooth as shown in FIG. 3, and the shape shallower on the side shallower than the Bragg peak. The dose distribution in the depth direction with respect to the total dose obtained by adding these to all slices has high uniformity in the irradiation area and has a sharp distribution at the deepest part of the irradiation area.

Therefore, according to the particle beam therapy system using the three-dimensional irradiation apparatus configured as described above, the uniformity is high, the dose in the direction perpendicular to the beam axis is improved, and Irradiation with less exposure can be performed on normal tissue because irradiation with good cutting at the deepest portion becomes possible.

In the fourth embodiment, the example in which the ridge filter 11 is disposed between the deflecting magnet 23 and the triple focusing magnet 25 of the particle beam transport device 21 has been described. Can be arranged at an arbitrary position as long as it is closer to the accelerator than the focusing magnet closest to the treatment room.

FIG. 10 is a schematic configuration diagram of a particle beam therapy apparatus using a three-dimensional irradiation apparatus for a three-dimensional spot scanning method, which is arranged in a treatment room and shows a fifth embodiment of the present invention. The same devices as those shown in FIG. 9 are denoted by the same reference numerals.

In FIG. 10, reference numeral 20 denotes a treatment room, 27 denotes a particle beam transport device for transporting a beam from a particle beam acceleration ring (not shown) to the treatment room 20, and 1 denotes a treatment arranged in the treatment room 20. The bed 22 is a three-dimensional irradiation device.

The particle beam transport device 27 comprises, for example, two deflecting magnets 23, 24 and two triple focusing magnets 25, 26. The three-dimensional irradiation device 22 includes scanning magnets 3a and 3b, a dose monitor 4, a position monitor 5, and a range shifter 7.

In this embodiment, the three-dimensional irradiation device 2
2 and the respective devices of the particle beam transport device and their functions are the same as in the first embodiment and the fourth embodiment, and therefore description thereof is omitted.

In this embodiment, the particle beam transport device 27
The energy distribution expanding plate 28 made of a non-parallel plate made of aluminum is disposed between the deflecting magnet 24 and the triple focusing magnet 26.

FIG. 11 is a diagram showing the shape of the energy distribution enlarging plate 28. As shown in FIG. In FIG. 11, a indicates that the cross section of the plate has, for example, an isosceles triangular shape, and that the particle beam that has passed through the energy distribution expanding plate changes its energy loss depending on the position where it passes through the energy distribution expanding plate 28. it can.

Immediately after the energy distribution expansion plate 28, the particle energy differs depending on the position on the beam cross section.
The particle energy is uniformed in the beam cross-section, allowing an energy distribution to occur, similar to a ridge filter.

FIG. 1 showing the shape of the energy distribution expanding plate 28.
1b has an inwardly curved shape as compared to a. At this time, the number of particles passing through the region having a small plate thickness is larger than the number of particles passing through the region having a large plate thickness. The weight can be made equal to the expanded one.

In this embodiment, since the energy distribution expanding plate 28 has a simple shape as compared with the ridge filter, it is possible to perform the same function as the ridge filter at a lower cost than the ridge filter. become. Further, since the energy distribution expanding plate 28 is disposed closer to the accelerator than the triple focusing magnet 26, the energy distribution expanding plate 2
The particle beam scattered by 8 is a triple focusing magnet 26
Therefore, it is possible to suppress an increase in the diameter of the beam irradiated to the affected part.

By adjusting the shape of the energy distribution enlarging plate 28, the dose distribution in which the Bragg peak is expanded in one slice in the depth direction is smooth and deeper than the side shallower than the Bragg peak. The sides can have a sharp shape. The dose distribution in the depth direction with respect to the total dose obtained by adding this to all slices has a high uniformity in the irradiation area and a sharp distribution at the deepest part of the irradiation area.

Therefore, according to the particle beam therapy system using the three-dimensional irradiation apparatus configured as described above, it is possible to perform irradiation with good cutting at the deepest part of the affected part, and to perform irradiation with less exposure to normal tissues. It can be carried out.

In the fifth embodiment, the energy distribution enlarging plate 28 is connected to the deflecting magnets 24 and 3 of the particle beam transport device 27.
Although an example in which the magnet is arranged between the continuous focusing magnet 26 and the focusing magnet 26 has been described, it can be arranged at an arbitrary position as long as it is closer to the accelerator than the focusing magnet closest to the treatment room in the particle beam transport device 27. .

FIG. 12 is a schematic configuration diagram of a particle beam therapy apparatus using a three-dimensional irradiation apparatus for a three-dimensional spot scanning method disposed in a treatment room according to a sixth embodiment of the present invention. The same devices as those in FIG. 9 are denoted by the same reference numerals.

In FIG. 12, reference numeral 20 denotes a treatment room; 29, a particle beam transporting device for transporting a beam from a particle beam acceleration ring (not shown) to the treatment room 20; 1, a treatment bed disposed in the treatment room; Reference numeral 22 denotes a three-dimensional irradiation device.

Here, the particle beam transport device 29 is, for example, 2
Two deflection magnets 23, 24, two triple focusing magnets 25, 2
6. In addition, the three-dimensional irradiation device 22
It comprises a scanning magnet 3, a dose monitor 4, a position monitor 5, and a range shifter 7.

In this embodiment, the three-dimensional irradiation device 2
2 and the respective devices of the particle beam transport device and their functions are the same as in the first embodiment and the fourth embodiment, and therefore description thereof is omitted.

In this embodiment, the energy distribution expanding plate 30 made of a non-parallel plate made of aluminum is arranged between the two deflection magnets 23 and 24 of the particle beam transport device 29.

FIG. 13 is a diagram showing the shape of the energy distribution enlarging plate 30. As shown in FIG. In each of the shapes of the energy distribution expanding plate 30 shown in FIG. 13, the plate thickness on the side defined as the direction in which the beam is deflected in the deflecting magnet 23 disposed on the accelerator side is larger than the plate thickness on the beam central axis. Has become.

The energy distribution expanding plate 30 shown in FIG.
Has the following functions.

The particle beam incident on the deflecting magnet 23 is displaced by the small energy spread of the beam itself.
When the light is emitted from the light source, a position spread is formed in the deflection direction.
That is, particles having a large energy (momentum) pass through a more inner trajectory in the deflecting magnet 23, and conversely, particles having a smaller energy (momentum) pass through a more inner trajectory in the deflecting magnet 23. At this time, particles having lower energy reach the side defined as the direction in which the beam is deflected in the deflecting magnet 23 disposed on the accelerator side. The particles having low energy pass through the region of the energy distribution expanding plate 30 shown in FIG. 13 where the plate thickness is large, so that a large amount of energy is lost and the energy is further reduced.

By using the energy distribution expanding plate shown in FIG. 13, the number of particles passing through the thin plate region becomes larger than the number of particles passing through the thick plate region.
That is, it is possible to select particles in the beam separated by energy and to attenuate the energy, and to more effectively generate a beam having a necessary energy distribution.

In this embodiment, since the energy distribution expanding plate 30 has a simple shape as compared with the ridge filter, it is possible to perform the same function as the ridge filter at a lower cost than the ridge filter. become. Therefore, at lower cost, the depth distribution of the expanded dose of the Bragg peak per slice is smooth,
In addition, a shape that is deeper than a side that is shallower than the Bragg peak can have a sharper shape. The dose distribution in the depth direction with respect to the total dose obtained by adding these to all slices has a high uniformity in the irradiation area and a sharp distribution at the deepest part of the irradiation area.

Therefore, according to the particle beam therapy system using the three-dimensional irradiation device configured as described above, low cost,
Irradiation with a sharp dose in the direction perpendicular to the beam axis can be performed, and normal tissue can be irradiated with less exposure.

In the above-described fourth to sixth embodiments, the three-dimensional irradiation method using the spot scanning method has been described. However, other three-dimensional irradiation methods such as a three-dimensional waggle method and a three-dimensional double scatterer method can be used. The same applies to the two-dimensional irradiation method as described above.

[0137]

As described above, according to the present invention, the distribution in the depth direction of the dose in which the Bragg peak is expanded for one slice is smooth, and the deeper side is cut off as compared with the shallower side than the Bragg peak. The dose distribution in the depth direction with respect to the total dose obtained by adding these to all slices has a high uniformity in the irradiation area and a sharp distribution at the deepest part of the irradiation area. Therefore, it is possible to provide a particle beam irradiation method, a device thereof, and a particle beam treatment device capable of performing irradiation with less exposure to normal tissue because the cutting of the deepest part of the affected part is improved with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a three-dimensional irradiation apparatus for a three-dimensional spot scanning method according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a shape of a ridge filter for three-dimensional irradiation in the embodiment.

FIG. 3 is a diagram illustrating a dose distribution in a depth direction and a weighting function in one slice irradiation according to the embodiment.

FIG. 4 is a diagram showing a dose distribution in a depth direction added to all thrust irradiation in the embodiment. ,

FIG. 5 is a schematic configuration diagram of a three-dimensional irradiation apparatus for a three-dimensional wobble method according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a three-dimensional irradiation apparatus for a three-dimensional double scatterer method showing a third embodiment of the present invention.

FIG. 7 is a diagram showing a shape of another ridge filter of the present invention.

FIG. 8 is a diagram showing a weighting function by the ridge filter of FIG. 7;

FIG. 9 is a schematic configuration diagram of a three-dimensional irradiation apparatus for a three-dimensional spot scanning method according to a fourth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a three-dimensional irradiation apparatus for a spot scanning method according to a fifth embodiment of the present invention.

FIG. 11 is a diagram showing a shape of the energy distribution expanding plate in the embodiment.

FIG. 12 is a schematic configuration diagram of a three-dimensional irradiation apparatus for a spot scanning method according to a sixth embodiment of the present invention.

FIG. 13 is a diagram showing a shape of an energy distribution expanding plate in the embodiment.

FIG. 14 shows a conventional three-dimensional irradiation apparatus for three-dimensional spot scanning.

FIG. 15 is a diagram showing a dose distribution in a depth direction of a single energy particle beam in a body.

FIG. 16 is a diagram showing a shape of a ridge filter for three-dimensional irradiation in a conventional example.

FIG. 17 is a diagram showing a dose distribution in a depth direction and a weighting function in one-slice irradiation in a conventional example.

FIG. 18 is a diagram illustrating a dose distribution in the depth direction added to irradiation of all slices in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Treatment bed 2,10,16,22 ... Three-dimensional irradiation device 3a, 3b ... Scanning magnet 4 ... Dose monitor 5 ... Position monitor 6,11 ... Ridge filter 7 ... Range filter 13 ... Scatterer 14 Wobble magnet 15 Multi-leaf collimator 17 Double scatterer 20 Treatment room 21, 27, 29 Particle beam transport device 23, 24 Deflection magnet 25, 26 Three sets Focusing magnets 28, 30 ... Enlarged energy distribution plate

Claims (16)

[Claims] 1. A method of enlarging a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body, switching the energy of the particle beam after performing one irradiation for a predetermined time, and sequentially switching the energy of the particle beam. A particle beam irradiation method for irradiating in a depth direction in a body, wherein the Bragg peak is weighted asymmetrically in a depth direction and the irradiation is performed by enlarging the Bragg peak. 2. A Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is expanded, irradiation is performed for a certain period of time, and a scanning magnet is scanned to change the irradiation position. After the repetition, the energy of the particle beam is switched, and irradiation is performed by sequentially switching the energy.
In a particle beam irradiation method of two-dimensional irradiation, the Bragg peak is weighted asymmetrically in a depth direction and the Bragg peak is expanded to perform irradiation. 3. A particle beam is expanded by a wobble magnet, a Bragg peak in a dose distribution of the particle beam formed in a depth direction in a body is expanded, and the particle beam is irradiated after one irradiation for a predetermined time. In the three-dimensional particle beam irradiation method of switching the beam energy and sequentially repeating the irradiation, the Bragg peak is weighted asymmetrically in a depth direction, and the Bragg peak is expanded to perform irradiation. Particle beam irradiation method. 4. A method for enlarging a particle beam by a scatterer, enlarging a Bragg peak in a dose distribution of the particle beam formed in a depth direction in the body, and performing one irradiation for a certain period of time. In the three-dimensional particle beam irradiation method of switching the beam energy and sequentially repeating the irradiation, the Bragg peak is weighted asymmetrically in a depth direction, and the Bragg peak is expanded to perform irradiation. Particle beam irradiation method. 5. Enlarging a Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body, switching the energy of the particle beam after performing one irradiation for a predetermined time, and sequentially switching the energy of the particle beam. In the particle beam irradiation method of irradiating in the depth direction in the body, the expansion of the Bragg peak weights the Bragg peak asymmetrically in the depth direction in the particle beam transport device from the particle beam accelerator to the particle beam irradiation device A particle beam irradiation method, which is performed. 6. A Bragg peak in a dose distribution of a particle beam formed in a depth direction in a body is enlarged, irradiation is performed for a predetermined time, and then a scanning magnet is scanned to change an irradiation position, and the irradiation is changed a plurality of times. After the repetition, the energy of the particle beam is switched, and irradiation is performed by sequentially switching the energy.
In the particle beam irradiation method of two-dimensional irradiation, the expansion of the Bragg peak is performed by asymmetrically weighting the Bragg peak in the depth direction in a particle beam transport device from a particle beam accelerator to a particle beam irradiation device, Particle beam irradiation method. 7. The particle beam irradiation method according to claim 1, wherein:
When the body position where the weight becomes maximum is Zm, the shallow side of the body position which is half the maximum value of the weight is Zf, and the deep side is Ze, it is expressed as | Ze−Zm | <| Zf−Zm | A particle beam irradiation method characterized by being weighted. 8. A mechanism for switching a plurality of energy of a particle beam, and a ridge filter for expanding a Bragg peak in a dose distribution of the particle beam formed in a depth direction in the body for each energy. In the particle beam irradiation apparatus, the ridge filter includes a plurality of bar pieces arranged side by side, and the shape function of each bar piece has an inflection point from a position having a minimum thickness to a position having a maximum thickness, and further has a The particle beam irradiation apparatus is configured such that the distance from the position of (1) to the inflection point is smaller than the distance from the position of the maximum thickness to the inflection point. 9. A scanning magnet for scanning a particle beam, a mechanism for switching the energy of the particle beam to a plurality,
A ridge filter for enlarging a Bragg peak in a dose distribution of a particle beam formed in a depth direction in the body with respect to each energy; Are arranged side by side, and the shape function of each bar has an inflection point from the minimum thickness position to the maximum position, and the distance from the minimum thickness position to the inflection point is the maximum thickness A particle beam irradiation apparatus characterized in that it is configured to be smaller than the distance from the position of (1) to the inflection point. 10. A scatterer for expanding a particle beam two-dimensionally, a mechanism for switching a plurality of energies of the particle beam, and a particle beam formed in a depth direction in the body for each energy. A particle beam irradiation apparatus for three-dimensional irradiation, comprising: a ridge filter for enlarging a Bragg peak in the dose distribution, wherein the ridge filter has a plurality of rods arranged side by side, and the shape function of each rod has a thickness function. It has an inflection point from the minimum position to the maximum position, and is configured so that the distance from the minimum thickness position to the inflection point is smaller than the distance from the maximum thickness position to the inflection point. A particle beam irradiation apparatus, characterized in that: 11. A particle beam irradiation apparatus according to claim 8, wherein a range shifter is used as a mechanism for switching the energy of the particle beam to a plurality of particles. Irradiation device. 12. An accelerator for accelerating a particle beam, a particle beam irradiation device for irradiating a particle beam, and a particle beam transport device for transporting a particle beam from the accelerator to the particle beam irradiation device. In the particle beam therapy device, a mechanism for switching the energy of the particle beam to a plurality is provided in any one of the accelerator, the particle beam irradiation device, and the particle beam transport device, and each energy is formed in a depth direction in a body. A particle beam therapy system, wherein a ridge filter for expanding a Bragg peak in a dose distribution of a particle beam to be performed is arranged in the particle beam transport device. 13. The particle therapy apparatus according to claim 12, wherein the ridge filter includes a plurality of rods arranged side by side.
In addition, the shape function of each bar has an inflection point from the minimum thickness position to the maximum position, and the distance from the minimum thickness position to the inflection point is from the maximum thickness position to the inflection point. A particle beam therapy system characterized by being configured to be smaller than a distance. 14. An accelerator for accelerating a particle beam, a particle beam irradiation device for irradiating a particle beam, and a particle beam transport device for transporting a particle beam from the accelerator to the particle beam irradiation device. In the particle beam therapy device, a mechanism for switching the energy of the particle beam to a plurality is provided in any one of the accelerator, the particle beam irradiation device, and the particle beam transport device, and each energy is formed in a depth direction in a body. A particle beam therapy system, wherein an energy distribution expansion plate having a non-uniform thickness for expanding a Bragg peak in a dose distribution of a particle beam to be performed is disposed in the particle beam transport device. 15. The particle beam therapy system according to claim 14, wherein the energy distribution expansion plate is disposed between two deflection magnets disposed in the particle beam transport device. Treatment device. 16. The particle beam therapy system according to claim 15, wherein the shape of the energy distribution expanding plate is such that a plate thickness on a side defined as a direction in which a beam is deflected by a deflecting magnet disposed on an accelerator side is a beam center. A particle beam therapy device characterized in that the thickness of the shaft is greater than the thickness of the shaft.