JP4655062B2 - Irradiation device for particle beam therapy system - Google Patents

Description

  The present invention relates to an irradiation apparatus for a particle beam therapy system using a particle beam of proton, carbon, helium or the like.

  Currently, proton therapy systems are used as a means of cancer treatment. In proton therapy, it is required to make the dose distribution of the affected area (target area) of a patient uniform. However, the proton beam intensity generated by the proton therapy system is not constant in time. In the scatterer irradiation method in which the proton beam is expanded using a scatterer and irradiated to the affected area, the entire affected area is irradiated at a time. Therefore, the dose distribution in the affected area is less likely to be nonuniform due to changes in the proton beam intensity. However, it is necessary to prepare a jig corresponding to the energy of the proton beam and the shape of the affected part.

  On the other hand, there is a scanning irradiation method that scans a proton beam and irradiates the affected area without irradiating the entire affected area at once (Non-Patent Document 1). In this irradiation method, the preparation of the jig corresponding to the shape of the affected area is reduced, but there is a problem that the dose distribution of the affected area cannot be made uniform because it is easily affected by the temporal non-uniformity of the proton beam.

  As a method for solving this, there is known a method in which a scanning path is scanned a plurality of times (multi-painting) with one spill of a proton beam (one beam extraction time). In this case, the period for scanning one scanning path is a part of one spill (one for the number of scanning times). That is, one scanning path is scanned at a short time interval. In such a short time interval, the proton beam intensity can be regarded as constant, so that the dose distribution on one scanning path can be regarded as uniform. Since this scanning is repeated, the total dose distribution can be regarded as uniform.

  FIG. 2 shows an outline of this conventional irradiation method. Assume that the scanning path (ab) on the affected area is scanned as shown in FIG. As shown in FIG. 2B, when the scan path is scanned m times with one spill, the scan path is scanned in a time of (1 / m) of one spill. During this time, the beam current can be regarded as constant, and the dose distribution in this scanning path can be regarded as uniform.

W. T. Chu, B. A. Ludewigt and T. R. Renner, Rev. Sci. Instrum. 64, 2055-2122, 1993.

  In the conventional irradiation method of FIG. 2, it is necessary to scan the proton beam in one scanning path in a short time and repeat this. For this reason, there exists a subject that the power supply capacity of the scanning electromagnet which scans a proton beam becomes large.

  An object of the present invention is to provide an irradiation apparatus of a particle beam therapy system capable of uniformly irradiating an affected area with a dose without increasing the power supply capacity of a scanning electromagnet that scans a particle beam such as a proton beam.

  According to the present invention, when a proton beam is reciprocally scanned with respect to a target region (affected area) with one spill of a proton beam (one beam extraction time), a constant interval is set according to the number of spills irradiated with the proton beam. In this order, the irradiation start position of each spill is shifted in order.

  Further, in the present invention, when the proton beam is reciprocally scanned with respect to the target area with one spill, the order is randomly selected from a plurality of positions determined at regular intervals according to the number of spills to irradiate the proton beam. Irradiate by shifting the irradiation start position of each spill in the selected order.

  Further, according to the present invention, when a proton beam is scanned in one pass on a target area with one spill, the one-pass scanning end position is determined from a plurality of positions determined at regular intervals according to the number of spills to irradiate the proton beam. The next position is selected, and the selected position is irradiated as the irradiation start position of each spill.

  Further, according to the present invention, when a proton beam is scanned with one pass on a target area with one spill, a position is randomly selected from a plurality of positions determined at regular intervals according to the number of spills to irradiate the proton beam. The selected position is irradiated as the irradiation start position of each spill.

  Further, the present invention scans the proton beam halfway along the scanning path with one spill, and continues scanning the proton beam from the middle of the scanning path with the next spill. The scanning of the proton beam for each scanning line is repeatedly performed for the number of times obtained by dividing the least common multiple of the number of scanning lines and the number of scanning lines scanned by one spill by the number of divided scanning lines.

Hereinafter, the beam irradiation method of the present invention and the effect of making the dose distribution uniform will be described with reference to FIG. The beam current waveform is simplified and shown as a straight line. In FIG. 1 (b), the irradiation time t ₁ of the proton _{beam, t 2, t 3, ...} t i, is ... t _m, the beam current _{I 1, I 2, I 3} , corresponding to ... I _i, ... I _m To do. Beam irradiation makes one reciprocation of the scanning path with one spill. In this case, the irradiation position on the scanning path _{y 1, y 2, y 3} , ... y k, ... y 2 is the beam current _{I 1, I 2, I 3} , corresponding to ... I _m. Assuming that the scanning length of the scanning path (y _{1 to} y _k ) is L, the number of scans is m, and the distance between the irradiation position y _i and y _{i + 1} (i = 1 to (k−1)) is Δ, 2L = The relationship of mΔ is established.

Table 1 shows the relationship between the irradiation position and the beam current when the irradiation start position for each scanning is shifted by Δ = 2 L / m on the scanning path. In the first scan, irradiation is started from the irradiation position y ₁ . At this time, the irradiation positions _{y 1, y 2, y 3} , ... , the beam current _{I 1, I 2, I 3} , ... is irradiated, is folded back at the irradiation position _{y k, y k-1,} y k- _2, through ..., beam current I _m is irradiated to the irradiation position y _2. In the second scan, the irradiation start position is y _2. At this time, the beam current I ₁ is irradiated to the irradiation position y _2, it is folded back at the irradiation position y _k, the beam current I _m is irradiated to the irradiation position y _1. Thus, the irradiation start position _{y 1, y 2, y 3} , y 4, ... and shifting gradually, I turned back at _{y k, y 2, y 1} , y 2, y 3, assumed to return to ... .

As shown in Table 1, the total beam current at each irradiation position is ΣI _i (i = 1 to m). Since the irradiation reciprocates along the scanning path, the sum of the beam currents at irradiation positions other than i = 1, k is 2ΣI _i . That is, the value of the beam current on the scanning path in FIG. Since the dose at each irradiation position is proportional to the beam current, the dose distribution in the affected area is uniform for an arbitrary beam waveform. Thus, by irradiating the beam irradiation start position with a certain interval, the dose distribution in the affected area can be made uniform.

  In the case of one reciprocation of the scanning path by one spill, as a method of irradiating with the irradiation start position shifted, there is a method of randomly determining the irradiation start position on one scanning path in addition to shifting the irradiation start position as described above. Also in this method, after the irradiation start position is determined at random, the irradiation start positions are uniformly arranged on the scanning path, so that the dose distribution in the affected area becomes uniform.

  The above irradiation is a case where the scanning path is reciprocated once by one spill, but there are cases where the scanning path is scanned only in one direction (one pass) by one spill. In this case, a position next to the one-pass end position is selected from a plurality of irradiation positions determined at regular intervals according to the number of spills to be irradiated, and this is irradiated as the irradiation start position of each spill. In some cases, the irradiation start position is selected at random and the irradiation is performed.

  In addition, the above irradiation is a case where the scanning path is scanned one reciprocation or one pass with one spill, but scanning is performed halfway along the scanning path with one spill, and irradiation is continued from the middle with the next spill. There is also. In this case, using the number of scanning lines dividing the scanning path in the irradiation field and the least common multiple of the number of scanning lines scanned by one spill, the least common multiple is calculated as the number of scanning lines dividing the scanning path in the irradiation field. Each scan line is scanned (repainted) by the number of times divided by. That is, assuming that the number of scanning lines dividing the scanning path is k, the number of scanning lines that can be scanned in one spill is h, and the least common multiple is n, the number of repaints of each scanning line is n / k, and the number of spills is n / H. The length of the scanning line is L / k. At this time, if the least common multiple of k and h is increased, the uniformity of the dose distribution becomes better.

  ADVANTAGE OF THE INVENTION According to this invention, a dose can be uniformly irradiated to an affected part, without enlarging the power supply capacity | capacitance of the scanning electromagnet which scans particle beams, such as a proton beam.

  Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are schematic explanatory views showing an embodiment of a proton beam irradiation method of a proton beam treatment system according to the present invention. FIG. 1A is a diagram showing a scanning path of a proton beam, and FIG. 1B is a time change of proton beam current. FIG. In (a), 1 is an irradiation field, 2 is a scanning path, and 3 is an irradiation start position. In (b), the proton beam current waveform is simplified and shown as a straight line.

In the irradiation field 1, the proton beam is scanned along the scanning path 2. The scanning of the proton beam that makes one round trip along the scanning path 2 is repeated m times. In FIG. 1 (b), the irradiation time t ₁ of the proton beam, t _2, t _3, is ... t _m, the beam current _{I 1, I 2, I 3} , corresponding to ... I _m. On the scanning path 2, the irradiation start position 3 when repeating the scanning, at equal intervals delta, y _1, y _2, y _3, placing the ... y _k. Assuming that the scanning length of the scanning path (y _{1 to} y _k ) is L, the number of scans is m, and the distance between the irradiation position y _i and y _{i + 1} (i = 1 to (k−1)) is Δ, 2L = The relationship of mΔ is established. On the scanning path, the irradiation start position for each scanning is shifted by Δ = 2 L / m.

Since irradiation is reciprocated once the scan path 2 in 1 spill, in the first scan, the irradiation position _{y 1, y 2, y 3} , ... y k, ... to y _2, the beam current I _1, I _2, I ₃ ,... _Im is irradiated. The irradiation start position is shifted from y ₁ , y ₂ , y ₃ , y ₄ ,..., Folded at y _k , and returned to y ₂ , y ₁ , y ₂ , y ₃ ,. By repeating this m times, as shown in Table 1, the dose distribution in the affected area can be made uniform with respect to an arbitrary beam waveform.

  FIG. 3 shows a schematic configuration diagram of a proton beam scanning electromagnet system in the proton beam irradiation apparatus of the proton beam therapy system according to the present invention. In FIG. 3, 4 is a scanning electromagnet that scans the proton beam, 5 is a scanning electromagnet power source, 6 is a control system for the scanning electromagnet power source 5, and 7 is a dose distribution monitor. The control system 6 calculates and obtains a current waveform of the scanning electromagnet 4 in which the scanning path of the proton beam is the scanning path 2 in FIG. 1, and supplies a control signal for supplying the obtained current waveform to the scanning electromagnet 4. Send to 5. The scanning electromagnet power source 5 generates a current waveform of the scanning electromagnet 4 according to the control signal received from the control system 6 and supplies the current waveform to the scanning electromagnet 4. The scanning electromagnet 4 generates a magnetic field according to the current waveform supplied from the scanning electromagnet power source 5 and moves the proton beam onto the scanning path 2 in FIG. During the proton beam irradiation, the uniformity of the dose distribution is confirmed by the dose distribution monitor 7 installed in the irradiation field.

  In this embodiment, since only one reciprocation is made on the scanning path with one spill, the proton beam is scanned (moved) within the time of one spill as compared with the conventional method (scanning the scanning path a plurality of times with one spill). The distance becomes shorter. For this reason, the temporal change rate of the magnetic field for scanning the proton beam is reduced, and the power supply capacity of the scanning electromagnet power supply can be reduced. Moreover, the dose distribution in the affected area becomes uniform.

  As described above, according to the present embodiment, it is possible to uniformly irradiate the affected area of the patient without increasing the power supply capacity of the scanning electromagnet (the deflecting electromagnet for deflecting) that scans the proton beam.

Next, another embodiment of the present invention will be described. In this embodiment, the irradiation start position in FIG. 1A is not regularly shifted from y ₁ , y ₂ , y ₃ ,... Y _k , but irradiation is performed from among a plurality of irradiation positions y _{1 to} y _k. A starting position is selected at random, and irradiation is performed once in and out of the scanning path using this as the irradiation start position, and this is repeated. Thus, even when the irradiation start position is set at random and the proton beam is irradiated, the beam current I _i is uniformly irradiated to each irradiation position after m times. Therefore, the dose distribution of the affected part can be made uniform with respect to an arbitrary beam waveform. Furthermore, according to the present embodiment, the control of the scanning electromagnet power source that scans the proton beam becomes easier.

  Next, another embodiment of the present invention will be described with reference to FIG. 4A and 4B are schematic explanatory views showing another embodiment of the proton beam irradiation method according to the present invention, wherein FIG. 4A is a view showing a scanning path of the proton beam, and FIG. 4B is a view showing a time change of the proton beam current. is there.

As in FIG. 4 (a), the irradiation start position 3 when repeating the scanning of the proton beam, on the scanning path 2, at regular intervals, y _1, y _2, y _3, placing the ... y k _{+ 1} . In the irradiation field 1, the proton beam is scanned along the scanning path 2. The scanning path is scanned by one pass with one spill, and the next irradiation position after the end of the one-pass irradiation is set as the next irradiation start position. Repeat this k times. When the distance from y ₁ to y _{k + 1} is L, the interval is Δ = L / k.

In FIG. 4B, the irradiation times t ₁ , t ₂ , t ₃ ,... T _k of the proton beam current correspond to the beam currents I ₁ , I ₂ , I _{3 ,.} Since the irradiation is performed with one spill and the scanning path is one-pass scanning, in the first scanning, the irradiation positions y ₁ , y ₂ , y ₃ ,... Y _k are changed to the beam currents I ₁ , I ₂ , I _{3 ,.} Correspond. Since the end position of the first one-pass irradiation is y _{k + 1} , the second irradiation start position is y _k , and y _k−1 , y _k−2 and the scanning path are scanned opposite to the first time, Turn back at y ₁ and end at y ₂ . Third scans the irradiation start position is shifted in the y _3.

  By repeating this k times, the dose distribution in the affected area can be made uniform with respect to an arbitrary beam waveform as in Table 1. According to the present embodiment, the one-pass scanning of the scanning path with one spill makes the distance for moving the proton beam within one spill time shorter, so that the power supply capacity of the scanning electromagnet power source for scanning the proton beam is further increased. Can be small.

Next, another embodiment of the present invention will be described. In this embodiment, in FIG. 4A, the irradiation start position 3 when the scanning of the proton beam is repeated is arranged on the scanning path 2 at equal intervals y ₁ , y ₂ , y ₃ ,... Y _k , y. Arrange with _{k + 1} . In the irradiation field 1, the proton beam is scanned along the scanning path 2. The scanning path is scanned by one pass with one spill, and this is repeated k times. When the distance from y ₁ to y _{k + 1} is L, the interval is Δ = L / k.

In FIG. 4B, the irradiation times t ₁ , t ₂ , t ₃ ,... T _k of the proton beam current correspond to the beam currents I ₁ , I ₂ , I _{3 ,.} Irradiation is performed by one-pass scanning of the scanning path with one spill, and the irradiation start position is not regularly shifted to y ₁ , y ₂ , y ₃ ,..., But from the irradiation positions y _{1 to} y _k. Is selected at random, and the scanning path is used as a one-pass scan with this as the irradiation start position, and this is repeated.

Even when irradiation is performed with the irradiation start position set at random in this way, the beam current I _i is uniformly irradiated to each irradiation position after k times. Therefore, the dose distribution of the affected part can be made uniform with respect to an arbitrary beam waveform. According to the present embodiment, the one-pass scanning of the scanning path with one spill makes the distance for moving the proton beam within one spill time shorter, so that the power supply capacity of the scanning electromagnet power source for scanning the proton beam is further increased. Can be small.

  Next, another embodiment of the present invention will be described with reference to FIG. 5A and 5B are schematic explanatory views showing another embodiment of the proton beam irradiation method according to the present invention, wherein FIG. 5A is a view showing a scanning path of the proton beam, and FIG. 5B is a view showing a time change of the proton beam current. is there.

  In FIG. 5A, 1 is an irradiation field, 2 is a scanning path, 3 is an irradiation start position, and 8 is a scanning line. In the proton beam irradiation of the above-described embodiment, the scanning path is reciprocated or scanned in one pass with one spill, but in this embodiment, the proton beam is scanned halfway along the scanning path with one spill, and the scanning is continued with the next spill ( Continue irradiation. This scanning method (irradiation method) includes a case where scanning is performed halfway along the scanning path with one spill when the scanning path is reciprocated a plurality of times.

As shown in FIG. 5 (a), the scanning lines _{8, L 1, L 2,} L 3, ... to L _k and labeling. If the number of scanning lines 8 in the scanning path is k, the number of scanning lines that can be scanned in one spill is h, and the least common multiple of k and h is n, the number of repaints of each scanning line is n / k, the number of spills (the number of scans) ) Is n / h. When the distance from y ₁ to y _{k + 1} is L, the length of each scanning line is L / k.

  In this embodiment, the proton beam is scanned halfway along the scanning path with one spill, and scanning is continued with the next spill. That is, the irradiation start position of the next spill is not shifted from the end position of one spill. For this reason, it is possible that the irradiation start position of each spill becomes the same position on the scanning path several times during the irradiation of the proton beam. If this happens, the uniformity of the dose distribution may be impaired. In order to avoid this, a combination of k and h that increases the least common multiple of k and h may be employed. By doing so, the uniformity of the dose distribution can be improved. Further, if k and h are selected so that the number of spills n / h becomes the same value as the number of scans m in the above-described embodiment, the uniformity of the dose distribution becomes comparable to that in the above-described embodiment.

  According to the present embodiment, the proton beam is scanned halfway along the scanning path with one spill without shifting the irradiation start position of each spill, and the scanning (irradiation) is continued with the next spill. Control becomes easier.

  In the above embodiment, the proton beam irradiation method for one layer of the affected part has been described. However, when the affected part is divided into multiple layers in the depth direction, the irradiation described above is performed in the same manner as in the case of one layer. By repeating the method, a uniform dose distribution can be achieved.

  In the above-described embodiments, the irradiation method of the proton beam therapy system using the proton beam has been described. However, the irradiation method described above is also applied to the irradiation method of the particle beam therapy system using the particle beam of carbon, helium, or the like. The method is applicable.

  The present invention can be used for an irradiation apparatus of a particle beam therapy system using a particle beam of proton, carbon, helium or the like.

It is a schematic explanatory drawing which shows one Example of the proton beam irradiation method of the proton beam treatment system by this invention, (a) is a figure which shows the scanning path | route of a proton beam, (b) is a figure which shows the time change of a proton beam current. It is explanatory drawing of the conventional irradiation method, (a) is a figure which shows a scanning path | route, (b) is a figure which shows the time change of beam current. 1 is a schematic configuration diagram of a proton beam scanning electromagnet system according to the present invention. FIG. FIG. 5 is a schematic explanatory view showing another embodiment of the proton beam irradiation method according to the present invention, where (a) shows a scanning path of the proton beam, and (b) shows a time change of the proton beam current. FIG. 5 is a schematic explanatory view showing another embodiment of the proton beam irradiation method according to the present invention, where (a) shows a scanning path of the proton beam, and (b) shows a time change of the proton beam current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Irradiation field 2 Scanning path 3 Irradiation start position 4 Scanning electromagnet 5 Scanning electromagnet power supply 6 Control system 7 Dose distribution monitor 8 Scanning line

Claims (6)

  In an irradiation apparatus that scans a target region with a particle beam therapy system using a proton beam, the spill of the spill that irradiates the proton beam when scanning the proton beam once and again with respect to the target region with one spill of the proton beam An irradiation apparatus for a particle beam therapy system, wherein irradiation is performed by shifting the irradiation start position of each spill in order at regular intervals according to the number of times.   In an irradiation apparatus that scans a target region with a particle beam therapy system using a proton beam, the spill of the spill that irradiates the proton beam when scanning the proton beam once and again with respect to the target region with one spill of the proton beam An irradiation apparatus for a particle beam therapy system, wherein an irradiation order is randomly selected from a plurality of positions determined at regular intervals according to the number of times, and irradiation is performed by shifting the irradiation start position of each spill in the selected order.   In an irradiation apparatus that scans a target area with a particle beam therapy system using a proton beam, a spill that irradiates the proton beam when the target area is scanned with one pass by one spill of the proton beam. According to the number of times, a position next to the one-pass scanning end position is selected from a plurality of positions determined at regular intervals, and the selected position is irradiated as an irradiation start position of each spill. Irradiation device.   In an irradiation apparatus that scans a target area with a particle beam therapy system using a proton beam, a spill that irradiates the proton beam when the target area is scanned with one pass by one spill of the proton beam. An irradiation apparatus for a particle beam therapy system, wherein a position is randomly selected from a plurality of positions determined at regular intervals according to the number of times, and the selected position is irradiated as an irradiation start position of each spill.   In an irradiation apparatus that scans a target region with a particle beam therapy system using a proton beam, the proton beam is scanned to the middle of the scanning path with one spill of the proton beam, and the proton beam is scanned from the middle of the scanning path with the next spill. When the scanning is continued, the least common multiple of the number of scanning lines dividing the scanning path in the irradiation field and the number of scanning lines scanned by 1 spill is divided by the number of the divided scanning lines, An irradiation apparatus for a particle beam therapy system, wherein the irradiation of the proton beam with respect to each scanning line is repeatedly performed.   6. The irradiation apparatus for a particle beam therapy system according to claim 1, wherein another particle beam is used instead of the proton beam.

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