JP5784808B2 - Particle beam therapy system - Google Patents

Description

  The present invention relates to a treatment planning apparatus used in a medical device (hereinafter referred to as “particle beam treatment device”) that performs treatment by irradiating an affected area such as cancer with a charged particle beam typified by a heavy particle beam such as carbon or a proton beam. .

  In medical devices that use X-rays and other radiations that were developed prior to particle beam therapy devices, the affected area can be uniformly irradiated at high doses by irradiating radiation with adjusted intensity from multiple directions. Treatments have been proposed to reduce exposure to surrounding tissue. Here, irradiating the affected area from multiple directions is called multi-port irradiation.

  Several methods have been proposed for multi-port irradiation. IMRT (Intensity-Modulated Radiotherapy) (Non-Patent Document 1, Non-Patent Document 2) and ELEKTA are used to perform step and shoot with a focus on Siemens. Examples include IMAT (Intensity-Modulated Arc Therapy) (Non-patent Document 3).

  Patented radiation irradiation device that has multiple compensators that change the spatial pattern of the X-ray intensity distribution for each irradiation direction to give a high absorbed dose only to the affected area, and that automatically changes the compensator for each irradiation direction and performs multi-port irradiation It is proposed in Document 1.

Japanese Patent Laying-Open No. 2005-37214 (FIGS. 17 to 21) Chui CS, SpirouSV.Inverse planning algorithms for external beam radiation therapy. Med Dosim 2001; 26 (2): 189-197 Keller-ReichenbecherMA, Bortfeld T, Levegrun S, et al. Intensity modulation with the "step and shoot" technique using a commercial MLC: a planning study.Multileafcollimator. Int J Radiat Oncol Biol Phys 1999; 45 (5): 1315-1324 . Yu CX. Intensity-modulated arc therapy with dynamic multileaf collimation: an alternative to tomotherapy.Phys Med Biol. 1995; 40 (9): 1435-1449. Urgent statement on intensity modulated radiation therapy. JASTRO NEWSLETTER 2002; 63 (3): 4-7.

  In radiotherapy equipment such as X-rays, IMRT has been used for many clinical applications in the head and neck region, prostate, etc., and has achieved excellent results, but problems such as over-irradiation have also been pointed out. According to Non-Patent Document 4, depending on the treatment plan contents, IMRT may cause an adverse event in normal tissue due to over-irradiation, regardless of whether or not it increases with a single line amount or total dose consciously, On the contrary, it warns that it becomes conservative and there is a risk of insufficient therapeutic effect due to underdose irradiation.

  One of the causes of this over-irradiation is thought to be due to insufficient degree of freedom of irradiation. The final irradiation field of IMRT by the radiotherapy apparatus such as X-ray shown in Non-Patent Document 1 to Non-Patent Document 4 is (1) irradiation energy, (2) irradiation angle, (3) multi-leaf collimator (hereinafter “ This is realized by superimposing a plurality of irradiations with the irradiation field limitation in the horizontal direction by (MLC)) and the like and (4) irradiation dose (weight) as parameters. There is no irradiation field limiter in the depth direction here.

  A bolus used in a particle beam therapy system is an example of a depth field limiter. The change shape of the affected part in the depth direction is called a distal shape. The bolus is an energy modulator that is processed according to this distal shape, and is made by processing polyethylene or wax for each patient. An irradiation apparatus equipped with a bolus is shown in FIG. 21 of Patent Document 1, for example, and can match the shape of the irradiation field to the distal shape of the affected area.

  However, one bolus cannot be directly applied to multi-port irradiation in the particle beam therapy system. First, in the case of IMRT, a bolus must be prepared for each of a plurality of irradiation directions. Although the radiation irradiation apparatus of Patent Document 1 can automatically move a compensator corresponding to a bolus, there is a problem that labor and cost of bolus processing are high. In addition, in the case of IMAT, it is more difficult, and the shape of the bolus must be changed dynamically according to the irradiation angle that changes every moment. Currently, this dynamic shape change cannot be realized with a bolus.

  Therefore, if the technique of IMRT in a radiotherapy apparatus such as X-ray is applied to a particle beam therapy apparatus having a conventional wobbler system as it is, there is a problem that a plurality of boluses must be used. Since the irradiation field in the depth direction is not limited without using a bolus, that is, the degree of irradiation freedom cannot be increased, the over-irradiation problem cannot be solved without using a bolus.

  The present invention aims to solve these problems. That is, the object is to solve the IMRT over-irradiation problem in the particle beam therapy system. More specifically, the IMRT over-irradiation problem in the particle beam therapy system is solved by increasing the degree of freedom of irradiation in the depth direction without using a bolus.

  The particle beam irradiation apparatus in the particle beam therapy system according to the present invention includes a scanning irradiation system that scans a charged particle beam accelerated by an accelerator, and a columnar irradiation wild field that generates a columnar irradiation field by expanding the Bragg peak of the charged particle beam. And a generating device. The columnar irradiation field generating device includes a first range shifter that reduces the energy of the charged particle beam that passes through the thickness in the direction in which the charged particle beam passes, and the downstream side of the first range shifter. The first ridge filter having a thickness distribution in which the energy lost depending on the position through which the charged particle beam passes, and the thickness of the charged particle beam in the direction in which the charged particle beam passes, A first range ridge filter that is disposed downstream of the second range shifter and has a thickness distribution in which the energy lost depending on the position through which the charged particle beam passes is different. A second ridge filter having a height different from that of the first range shifter of the charged particle beam and the first ridge filter. An upstream deflection electromagnet pair that moves the passing position in the second range shifter and the second ridge filter of the charged particle beam, and the beam axis of the charged particle beam trajectory incident on the column irradiation field generator A pair of downstream deflection electromagnets returning to the direction, so that the charged particle beam passes through a predetermined thickness distribution of the first range shifter and a predetermined thickness distribution of the first ridge filter, or the charged particle beam is transferred to the second range shifter. And a change control device for controlling the upstream deflection electromagnet pair and the downstream deflection electromagnet pair so as to pass through the predetermined thickness and the predetermined thickness distribution of the second ridge filter. In the treatment planning apparatus for creating a treatment plan for the particle beam treatment apparatus, the columnar irradiation field is the width of the SOBP in which the height of the columnar irradiation field is the width in the irradiation direction of the charged particle beam, and the columnar irradiation field The length of the cross section perpendicular to the height direction axis of the irradiation field is the beam size that is the width in the X direction and the Y direction of the charged particle beam, and the height of the columnar irradiation field is longer than the beam size. The beam size is a single size selected in one treatment irradiation, and a columnar irradiation field having one SOBP width according to the distal shape of the irradiation target irradiated with the charged particle beam. And an irradiation field arrangement section for arranging and arranging an inner column irradiation field which is a columnar irradiation field having a different SOBP width from the outer column irradiation field inside the irradiation target, Arrangement Optimum adjustment of the arrangement of the outer columnar irradiation field and the inner columnar irradiation field so that the irradiation dose to the irradiation target falls within a predetermined range, with the state where the outer columnar irradiation field and the inner columnar irradiation field are spread by the initial stage And a calculation calculation unit.

  The treatment planning apparatus according to the present invention lays out a columnar irradiation field in which the Bragg peak of the charged particle beam is enlarged according to the distal shape of the irradiation target, so that the irradiation dose to the irradiation target falls within a predetermined range. Since the arrangement of the irradiation field is adjusted, the IMRT over-irradiation problem in the particle beam therapy system can be solved by increasing the degree of freedom of irradiation in the depth direction without using a bolus.

It is a block diagram which shows the particle beam irradiation apparatus by Embodiment 1 of this invention. It is a block diagram which shows the energy change apparatus of FIG. It is a block diagram which shows the depth direction irradiation field expansion apparatus of FIG. It is a flowchart which shows the preparation method of the treatment plan in the treatment plan apparatus of this invention. It is a figure explaining step ST1 of FIG. It is a schematic diagram which calculates | requires the initial state in the optimal calculation of the treatment plan of this invention. It is a block diagram which shows the energy change apparatus by Embodiment 2 of this invention. It is a block diagram which shows the depth direction irradiation field expansion apparatus by Embodiment 3 of this invention. It is a block diagram which shows the columnar irradiation field production | generation apparatus by Embodiment 4 of this invention. It is a block diagram which shows the particle beam therapy apparatus by Embodiment 5 of this invention.

Embodiment 1 FIG.
Consider IMRT with columnar scanning irradiation, which is a feature of the present invention. The general idea of spot scanning is to irradiate an affected area with a spot in a three-dimensional manner as if it were pointed. Spot scanning is an irradiation method with such a high degree of freedom, but on the other hand, it takes a long time to irradiate the entire affected area. Since IMRT is multi-port irradiation, it takes more time. Therefore, a Bragg peak BP is expanded in the depth direction from the spot to generate a columnar irradiation field.

  FIG. 1 is a block diagram showing a particle beam irradiation apparatus according to Embodiment 1 of the present invention. The particle beam irradiation device 58 expands the Bragg peak BP in the depth direction, generates a columnar irradiation field 4, and charges in the X and Y directions that are perpendicular to the charged particle beam 1. X-direction scanning electromagnet 10 and Y-direction scanning electromagnet 11 that scan the particle beam 1, position monitors 12 a and 12 b, dose monitor 13, scanning electromagnet power supply 32, and irradiation control that controls the irradiation system of the particle beam irradiation device 58. Device 33. The X-direction scanning electromagnet 10, the Y-direction scanning electromagnet 11, and the scanning electromagnet power supply 32 are a scanning irradiation system 34 that scans the charged particle beam 1. The traveling direction of the charged particle beam 1 is the Z direction. The columnar irradiation field generating device 4 reduces the energy of the charged particle beam from the near side toward the traveling direction of the charged particle beam and changes it to a desired energy, and the depth direction of the Bragg peak BP in the affected area 40 to be irradiated ( An energy changing device 2 that adjusts the position (range) in the Z direction) and a depth direction irradiation field expanding device 3 that changes the energy width of the charged particle beam 1 and expands the Bragg peak BP in the depth direction. Have. The Bragg peak BP in which the width of the affected part 40 in the depth direction, that is, the width in the irradiation direction is expanded is called an expanded Bragg peak SOBP (Spread-Out Bragg Peak). Here, the width in the irradiation direction of the enlarged Bragg peak SOBP is referred to as the SOBP width.

  The X direction scanning electromagnet 10 is a scanning electromagnet that scans the charged particle beam 1 in the X direction, and the Y direction scanning electromagnet 11 is a scanning electromagnet that scans the charged particle beam 1 in the Y direction. The position monitors 12a and 12b detect passing positions through which the charged particle beam 1 scanned by the X-direction scanning electromagnet 10 and the Y-direction scanning electromagnet 11 passes. The dose monitor 13 detects the dose of the charged particle beam 1. The irradiation control device 33 controls the columnar irradiation field and its irradiation position in the affected part 40 based on the treatment plan data created by the treatment planning device (not shown), and when the dose measured by the dose monitor 13 reaches the target dose. Stop the charged particle beam. The scanning electromagnet power supply 32 changes the set currents of the X-direction scanning electromagnet 10 and the Y-direction scanning electromagnet 11 based on control inputs (commands) to the X-direction scanning electromagnet 10 and the Y-direction scanning electromagnet 11 output from the irradiation control device 33. Let

  FIG. 2 is a block diagram showing the energy changing device. FIG. 3 is a block diagram showing a depth direction irradiation field enlarging apparatus. The energy changing device 2 includes a range shifter 9 whose thickness changes stepwise in the width direction (X direction), a deflection electromagnet 5 constituting an upstream deflection electromagnet pair that moves a position where the charged particle beam 1 passes through the range shifter 9, 6. First deflection electromagnet power source 20 for exciting the upstream deflection electromagnet pair, deflection electromagnets 7, 8 constituting the downstream deflection electromagnet pair for returning the charged particle beam 1 having passed through the range shifter 9 to the original trajectory, downstream Based on the energy command value input from the second deflection magnet power source 21 and the irradiation control device 33 for exciting the deflection magnet pair, the moving amount of the charged particle beam trajectory by the upstream deflection magnet pair is calculated, and the excitation current value is calculated. A change control device 22 for transmitting to the first bending electromagnet power source 20 is provided. The change control device 22 also controls the second bending electromagnet power source 21.

  The charged particle beam 1 is incident on the upstream deflection electromagnet pairs 5 and 6 on the beam axis 14 (Z axis). The trajectory of the charged particle beam 1 is moved in the horizontal direction (X direction) in FIG. The deflection electromagnet 5 is a deflection electromagnet for changing the orbit, and the deflection electromagnet 6 is a deflection electromagnet for orbital parallelism. The trajectory changing deflection electromagnet 5 deflects the trajectory of the incident charged particle beam 1 so as to be inclined by a predetermined angle θ with respect to the Z axis. The trajectory parallel deflecting electromagnet 6 deflects the trajectory tilted with respect to the Z axis by the trajectory changing deflecting electromagnet 5 into a trajectory parallel to the Z axis. On the downstream side of the range shifter 9, the charged particle beam 1 is returned onto the beam axis 14 (Z axis) by the orbit changing deflection electromagnet 7 and the orbital parallel deflection electromagnet 8. The deflecting electromagnet 7 for changing the trajectory deflects the trajectory of the charged particle beam 1 so as to be inclined by (360 degrees−predetermined angle θ) with respect to the Z axis. The orbit parallel deflecting electromagnet 8 deflects the orbit inclined with respect to the Z axis by the orbit changing deflecting electromagnet 7 to the orbit on the Z axis.

  The operation of the energy changing device 2 will be described. The charged particle beam 1 introduced into the energy changing device 2 travels on a trajectory parallel to the Z axis that is separated from the Z axis by a predetermined distance in the X direction by the upstream deflection magnet pairs 5 and 6. Then, when the charged particle beam 1 passes through the range shifter 9 having a predetermined thickness, the energy is reduced by an amount proportional to the thickness to obtain a desired energy. The charged particle beam 1 thus changed to the desired energy is returned to the extension line of the original trajectory when it is incident on the energy changing device 2 by the downstream deflection electromagnet pairs 7 and 8. The energy changing device 2 has an advantage that the driving sound for driving the range shifter is not generated when changing to energy and changing the range. The trajectory of the charged particle beam 1 deflected by the downstream deflection electromagnet pairs 7 and 8 is not limited to returning on the beam axis 14, but when returning to the beam axis 14 parallel to the beam axis 14, the beam axis Even if it is not parallel to 14, it may return to the beam axis 14.

  FIG. 3 is a block diagram showing a depth direction irradiation field enlarging apparatus. The depth direction irradiation field expanding device 3 is composed of approximately triangular prisms having different heights in the width direction (X direction), that is, a ridge filter 19 and a ridge filter 19 configured to have a plurality of peaks having different thickness distributions. The deflection electromagnets 15 and 16 constituting the upstream deflection electromagnet pair moving the position where the charged particle beam 1 passes, the first deflection electromagnet power source 23 for exciting the upstream deflection electromagnet pair, and the charged particles that have passed through the ridge filter 19 The deflection electromagnets 17 and 18 constituting the downstream deflection electromagnet pair for returning the beam 1 to the original trajectory, the second deflection electromagnet power supply 24 for exciting the downstream deflection electromagnet pair, and the SOBP command value input from the irradiation controller 33 And a change control device 25 for calculating the moving amount of the charged particle beam trajectory by the upstream deflection electromagnet pair and transmitting the excitation current value to the first deflection electromagnet power source 23. That. The change control device 25 also controls the second bending electromagnet power supply 24.

  The charged particle beam 1 is incident on the upstream deflection electromagnet pairs 15 and 16 on the beam axis 14 (Z axis). The trajectory of the charged particle beam 1 is moved in the horizontal direction (X direction) in FIG. The deflection electromagnet 15 is a deflection electromagnet for changing the orbit, and the deflection electromagnet 16 is a deflection electromagnet for orbital parallelism. The trajectory changing deflection electromagnet 15 deflects the trajectory of the incident charged particle beam 1 so as to be inclined by a predetermined angle θ with respect to the Z axis. The orbit parallel deflecting electromagnet 16 deflects the orbit inclined with respect to the Z axis by the orbit changing deflecting electromagnet 15 into an orbit parallel to the Z axis. On the downstream side of the ridge filter 19, the charged particle beam 1 is returned to the beam axis 14 (Z axis) by the orbit changing deflection electromagnet 17 and the orbit parallel deflection electromagnet 18. The deflecting electromagnet 17 for changing the trajectory deflects the trajectory of the charged particle beam 1 so as to be inclined by (360 degrees−predetermined angle θ) with respect to the Z axis. The orbit parallel deflecting electromagnet 18 deflects the orbit inclined with respect to the Z axis by the orbit changing deflecting electromagnet 17 to the orbit on the Z axis.

  Operation | movement of the depth direction irradiation field expansion apparatus 3 is demonstrated. The charged particle beam 1 introduced into the depth direction irradiation field expanding device 3 travels on a trajectory parallel to the Z axis, which is separated from the Z axis by a predetermined distance in the X direction by the upstream deflection electromagnet pairs 15 and 16. Then, when the charged particle beam 1 passes through the portion of the ridge filter 19 having a predetermined thickness distribution, the energy is reduced by an amount proportional to the thickness, and as a result, various kinds of energy whose intensity changes are mixed. Become a particle beam. The width of the SOBP can be changed according to the height of the ridge of the ridge filter 19 through which the charged particle beam 1 passes. The charged particle beam 1 thus changed to the desired SOBP width is returned to the extension of the original trajectory when it is incident on the depth direction irradiation field expanding device 3 by the downstream deflection magnet pairs 17 and 18. It is. The depth direction irradiation field expanding device 3 has an advantage that the driving sound for driving the ridge filter is not generated when the width of the SOBP is changed. It should be noted that the trajectory of the charged particle beam 1 deflected by the downstream deflection electromagnet pairs 17 and 18 is not limited to returning on the beam axis 14, but when returning to the beam axis 14 parallel to the beam axis 14, the beam axis Even if it is not parallel to 14, it may return to the beam axis 14.

  By mounting the particle beam irradiation device 58 on the rotating gantry, the irradiation system of the particle beam irradiation device 58 can freely rotate around the patient table, and the affected part 40 can be irradiated from multiple directions. The rotating gantry rotates the irradiation system of the particle beam irradiation device 58 and rotates the irradiation direction. That is, this allows multi-gate irradiation. Further, by using the ridge filter 19 in the particle beam irradiation device 58 so as to expand the irradiation field in the Z direction larger than the XY direction, a columnar dose distribution with respect to the affected area 40 (see FIG. 5). A beam can be irradiated.

  Next, a method for performing IMRT by columnar scanning irradiation will be described. FIG. 4 is a flowchart showing a method for creating a treatment plan in the treatment planning apparatus of the present invention, FIG. 5 is a diagram for explaining step ST1 in FIG. 4, and FIG. 6 is a schematic diagram for obtaining an initial state in the optimum calculation of the treatment plan. FIG. 5 and 6 show an example in which irradiation is performed at four gates (at intervals of 90 degrees). The treatment planning apparatus arranges a columnar irradiation field in accordance with the distal shape of the affected part (irradiation target) 40 to which the charged particle beam 1 is irradiated, and lays a columnar irradiation field inside the affected part (irradiation target) 40. The irradiation field arrangement part to be arranged and the state in which the columnar irradiation field is spread by the irradiation field arrangement part as an initial state, the columnar irradiation field is set so that the irradiation dose to the affected part (irradiation target) 40 falls within a predetermined range. An optimization calculation unit for adjusting the arrangement is provided.

  First, as shown in FIG. 5, columnar irradiation fields 44a, 44b, 44c, and 44d, which are columnar irradiation fields, are spread in accordance with the distal shape of the affected area 40 (step ST1). This is performed for all gates (irradiation direction). At this time, the columnar irradiation fields may overlap. The overlapping part will be explained later. FIG. 5A shows an example in which the columnar irradiation field 44a is spread according to the distal shape of the affected part 40 in the irradiation from the irradiation direction 43a, and FIG. 5B shows the columnar irradiation when the irradiation direction is the irradiation direction 43b. 5C shows a columnar irradiation field 44c when the irradiation direction is the irradiation direction 43c, and FIG. 5D shows a columnar irradiation field 44d when the irradiation direction is the irradiation direction 43d. FIG. 6A shows an example of the arrangement of the irradiation field when completed in all gates (irradiation direction).

  When all the gates (irradiation directions) are completed, it is determined whether there is a remaining irradiation target region (step ST2). If there is no remaining irradiation target area, the process proceeds to step ST5. If there is a remaining irradiation target area, a second round of laying operation is performed on the remaining irradiation target area so as to match the distal shape of the remaining irradiation target (step ST3). As shown in FIG. 6B, when the irradiation direction is the irradiation direction 43c, the columnar irradiation field 45c is spread. At this time, the columnar irradiation field in the second round may be changed in width between the columnar irradiation field in the first round and the SOBP. An example of the arrangement of the irradiation field when completed at all gates (irradiation direction) is as shown in FIG. In FIG. 6C, the columnar irradiation field 45a is the case where the irradiation direction is the irradiation direction 43a, the columnar irradiation field 45b is the case where the irradiation direction is the irradiation direction 43b, and the columnar irradiation field 45d is the irradiation direction 43d. This is the case.

  When all the gates (irradiation direction) in the second round are completed, it is determined whether there is a remaining irradiation target region (step ST4). If there is a remaining region to be irradiated, the process proceeds to step ST3 and is repeated so that the columnar irradiation field covers the entire affected area. If there is no remaining irradiation target area, the process proceeds to step ST5.

  In step ST5, optimization calculation is performed using an irradiation plan in which columnar irradiation fields are spread as initial values. When the optimization calculation is completed, evaluation is performed using an evaluation function (step ST6). It is determined whether the value of the evaluation function is clinically acceptable. If it is determined that the evaluation function is not acceptable, the process returns to step ST5 and optimization calculation is performed. If the value of the evaluation function is within a clinically acceptable range, the process ends.

  In the optimization of the treatment plan shown in steps ST5 and ST6, in order to prevent overdose (excess dose), the arrangement of columnar irradiation fields is adjusted so that the irradiation dose to the affected area 40 falls within a predetermined range. Since the portion where the columnar irradiation field overlaps becomes overdose (dose excess), the optimization work eliminates or reduces the portion where the columnar irradiation field overlaps. Change the placement of.

  The operations in steps ST1 to ST4 are first performed in the irradiation field arrangement unit of the treatment planning apparatus. Next, the treatment planning apparatus will be described. Regarding the treatment planning device, the operation manual of the radiation treatment planning device for medical safety (Kozo Kumagai, Japan Radiological Engineers Association Publishing) is detailed. Although the treatment planning apparatus has a wide range of roles, it can be said that it is a treatment simulator in simple terms. One of the roles of the treatment planning apparatus is optimization calculation. The optimization of the treatment plan shown in steps ST5 and ST6 is performed by the optimization calculation unit of the treatment plan apparatus. The optimization calculation is used to search for the optimum beam intensity in inverse treatment planning (inverse planning) in IMRT.

  According to the operation manual, the following has been tried for the optimization calculation so far. The filter backprojection method used in the initial IMRT optimization calculation, pseudo-annealing classified into probabilistic methods, genetic algorithm, random search technology, and determinism currently implemented in many treatment planning devices It is a gradient method classified as a general method.

  The gradient method is fast in calculation, but has the property that it cannot escape when captured by a local minimum (minimum). However, the gradient method is currently employed in many treatment planning devices that implement clinical IMRT treatment planning.

  In order to prevent the gradient method from being caught by another local minimum value different from the optimum to be obtained, it is also effective to use it in combination with other genetic algorithms and random search techniques. In addition, it has been empirically known that the initial value of optimization calculation (the value initially given as a solution candidate) should be close to the optimum solution to be obtained.

  Therefore, in the present invention, the irradiation plan created in steps ST1 to ST4 is used as an initial value for optimization calculation. Compared to the conventional IMRT, the irradiation plan in steps ST1 to ST4 is sufficiently close to the optimal irradiation because the degree of freedom of irradiation in the depth direction is high so as to match the distal shape of the affected area.

ここでＤ_ｍｉｎ、Ｄ_ｍａｘは指定した線量制限である。ｕはＤ_ｍｉｎに対する重み係数であり、ｗはＤ_ｍａｘに対する重み係数である。ｂ（数式（１）では矢印付きで示したが、矢印なしで示す。以後、数式（１）関連の説明において同じ。）はビームレットの強度の関数であり、ｄ_ｉ（ｂ）はビームレットの強度の関数ｂとしたボクセルｉの線量である。［ｘ］_＋はｘ＞０ではｘ、それ以外では０となる。Ｎはボクセルの最大数である。 The optimization calculation always calculates a solution that minimizes a certain evaluation function. In the case of the treatment planning apparatus, as shown in the operation manual, the evaluation function that is a reference for physical optimization is shown as follows.

Here, D _min and D _max are specified dose limits. u is a weighting factor for _Dmin , and w is a weighting factor for _Dmax . b (shown with an arrow in Formula (1), but without an arrow. Hereinafter, the same applies to the description related to Formula (1)) is a function of the intensity of the beamlet, and d _i (b) is a beamlet. Is the dose of voxel i as a function of intensity b. [X] ₊ is x when x> 0, and 0 otherwise. N is the maximum number of voxels.

  As described above, since the optimization calculation is performed in the treatment planning apparatus, for example, even if the columnar irradiation fields overlap and become overdose (excess dose) in the initial value, adjustment is made in the obtained treatment plan.

  With the configuration as described above, according to the treatment planning apparatus of the first embodiment, it is possible to increase the degree of freedom in irradiation in the depth direction without using a bolus, and the IMRT over-irradiation problem in the particle beam therapy apparatus Can be solved.

  The effect of irradiating a beam with a columnar dose distribution will be described. In the first place, in the conventional particle beam therapy system premised on irradiation from one direction, the dose distribution in the irradiation system is formed by the following method. The wobbler method will be described as an example. In the XY direction, the irradiation field is uniformly enlarged by a wobbler electromagnet and a scatterer, and limited by MLC based on the XY plane cross-sectional shape (or the shape projected on the XY plane, etc.) of the affected area. . In the Z direction, the irradiation field is uniformly enlarged by a ridge filter, and the bolus is limited so as to match the distal shape (deepest layer shape) of the affected area.

  As mentioned above, multiple portals must be used for multi-port irradiation in a particle beam therapy system, which requires labor and cost for bolus processing, and the shape of the bolus cannot be changed dynamically. There wasn't. If the irradiation field can be limited to match the distal shape (deepest layer shape) of the affected area like a bolus without using a bolus in multi-port irradiation in a particle beam therapy system, the effort and cost of bolus processing This problem can be solved and application to IMAT becomes possible, and the IMRT over-irradiation problem, that is, unnecessary irradiation to normal tissues can be significantly reduced. Thus, the inventors have come up with an invention for irradiating a beam with a columnar dose distribution. One of the greatest effects of irradiating a beam with a columnar dose distribution in the present invention is that the irradiation field can be limited to match the distal shape (deepest layer shape) of the affected area 40 without using a bolus. In other words, unnecessary irradiation to normal tissues can be significantly reduced.

  Another greatest effect of irradiating a beam with a columnar dose distribution in the present invention is that an irradiation field can be formed without intensity modulation used in a radiotherapy apparatus such as an X-ray. Here, the principle of intensity modulation is simply to irradiate an irradiation field with a weak dose distribution from multiple directions, and as a radiation field where a place where more doses finally overlap with each other by applying superposition will exert a therapeutic effect It is to obtain a dose distribution.

  In the present invention, the irradiation field can be formed by combining columnar doses as shown in FIG. Although supplemented here, in the present invention, irradiation may be performed with overlapping irradiation fields. Underdose and overdose are not allowed for each part of the affected area, but there are a range of clinically acceptable doses. An irradiation plan is made by the treatment planning apparatus so that the final dose distribution is acceptable for each part of the affected area. Unlike conventional X-ray and other radiotherapy devices, it is not necessary to modulate the intensity of the final irradiation field so that it matches the distal shape of the affected area. That is, the problem that the time required for the conventional treatment plan is long can be solved. Further, irradiating a beam with a columnar dose distribution has an advantage that the irradiation time is shorter than that of irradiating in a spot shape.

  The particle beam therapy system using the therapy planning apparatus according to the first embodiment has several merits that allow multi-port irradiation, but there are mainly the following two points. One is that when the same affected area is irradiated, the multi-portion irradiation has a larger body surface area through which the particle beam passes, so that damage to the body surface, which is a normal tissue, can be reduced. The other is that it is possible to avoid irradiating a dangerous part (spinal cord, eyeball, etc.) that should not be irradiated.

  As described above, according to the treatment planning apparatus of the first embodiment, the scanning irradiation system 34 that scans the charged particle beam 1 accelerated by the accelerator, the Bragg peak of the charged particle beam 1 is expanded, and the columnar irradiation field is formed. A treatment planning apparatus for creating a treatment plan for a particle beam therapy system including a columnar irradiation field generation apparatus 4 to be generated, and a columnar irradiation field according to a distal shape of an irradiation target 40 irradiated with a charged particle beam 1 44 and an irradiation field arrangement part that lays and arranges a columnar irradiation field 45 inside the irradiation object 40, and a state where the columnar irradiation fields 44 and 45 are laid by the irradiation field arrangement part as an initial state, And an optimization calculation unit that adjusts the arrangement of the columnar irradiation fields 44 and 45 so that the irradiation dose to the irradiation target 40 falls within a predetermined range. The columnar irradiation field can be laid out according to the distal shape of the irradiation target, and the arrangement of the columnar irradiation field can be adjusted so that the irradiation dose to the irradiation target falls within the predetermined range. The degree of freedom of irradiation can be increased, and the IMRT over-irradiation problem in the particle beam therapy system can be solved.

Embodiment 2. FIG.
FIG. 7 is a block diagram showing an energy changing device according to the second embodiment of the present invention. The energy changing device 2a according to the first embodiment uses a plurality of absorbers 26a, 26b, 26c, and 26d to reduce the energy of the charged particle beam 1 to change it to a desired energy, and the affected part 40 that is an irradiation target. Is different in that the position (range) of the Bragg peak BP in the depth direction (Z direction) is adjusted.

  The energy changing device 2b includes a plurality of absorbers 26a, 26b, 26c, and 26d that are driven by the driving devices 27a, 27b, 27c, and 27d. The absorbers 26a, 26b, 26c, and 26d are absorbers having different thicknesses. The total thickness of the absorber can be changed by the combination of the absorbers 26a, 26b, 26c, and 26d. The change control device 22 controls the drive devices 27a, 27b, 27c, and 27d so that the charged particle beam 1 passes through or does not pass through the absorbers 26a, 26b, 26c, and 26d corresponding to the drive devices. To. The charged particle beam 1 is reduced in energy by a proportion proportional to the total thickness of the absorber passing therethrough to become a desired energy.

  The particle beam irradiation apparatus (see FIG. 1) having the energy changing device 2b according to the second embodiment can expand the Bragg peak BP in the depth direction and generate a columnar irradiation field, as in the first embodiment. it can. Since the energy changing device 2b according to the second embodiment does not need to deflect the charged particle beam 1, the deflecting electromagnets 5 to 8 are eliminated and the charged particle beam 1 is irradiated as compared with the energy changing device 2a according to the first embodiment. The length L1 of the device in the direction (Z direction) can be shortened. Since the length L1 of the device can be shortened, the energy changing device can be made compact. 2 is the length from the upstream end of the deflection electromagnet 5 to the downstream end of the deflection electromagnet 8. In FIG.

  The particle beam irradiation apparatus (see FIG. 1) having the energy changing device 2b according to the second embodiment can execute multi-port irradiation based on a treatment plan corresponding to the treatment plan created by the treatment planning apparatus shown in the first embodiment. Therefore, as in the first embodiment, the degree of freedom in irradiation in the depth direction can be increased without using a bolus, and the IMRT over-irradiation problem in the particle beam therapy system can be solved.

Embodiment 3 FIG.
FIG. 8 is a block diagram showing a depth direction irradiation field enlarging apparatus according to Embodiment 3 of the present invention. The depth direction irradiation field expanding device 3a of the first embodiment uses a plurality of ridge filters 28a, 28b, 28c, and 28d to change the energy of a charged particle beam into a state in which various types of energy are mixed, that is, a charged particle beam. The difference is that the width of energy 1 is changed and the Bragg peak BP is expanded in the depth direction.

  The depth direction irradiation field expansion device 3b includes a plurality of ridge filters 28a, 28b, 28c, and 28d driven by driving devices 29a, 29b, 29c, and 29d. The ridge filters 28a, 28b, 28c, and 28d are ridge filters having different thicknesses. The total thickness of the ridge filter can be changed by combining each of the ridge filters 28a, 28b, 28c, and 28d. The change control device 25 controls the drive devices 29a, 29b, 29c, and 29d so that the charged particle beam 1 passes through or does not pass through the ridge filters 28a, 28b, 28c, and 28d corresponding to the drive devices. To. The width of the energy of the charged particle beam 1 is increased by an amount proportional to the total thickness of the ridge filter that passes, and the desired SOBP width is obtained.

  The particle beam irradiation apparatus (see FIG. 1) having the depth direction irradiation field enlargement apparatus 3b of the third embodiment expands the Bragg peak BP in the depth direction in the same manner as in the first embodiment, thereby forming a columnar irradiation field. Can be generated. Since the depth direction irradiation field expanding device 3b according to the third embodiment does not need to deflect the charged particle beam 1, the deflecting electromagnets 15 to 18 are provided as compared with the depth direction irradiation field expanding device 3a according to the first embodiment. The length L2 of the apparatus in the irradiation direction (Z direction) of the charged particle beam 1 can be shortened. Since the length L2 of the device can be shortened, the depth direction irradiation field expanding device can be made compact. The length L2 of the device in FIG. 3 is the length from the upstream end of the deflection electromagnet 15 to the downstream end of the deflection electromagnet 18.

  The particle beam irradiation apparatus (see FIG. 1) having the depth direction irradiation field expanding apparatus 3b of the third embodiment is based on a treatment plan corresponding to the treatment plan created by the treatment planning apparatus shown in the first embodiment. Since irradiation can be executed, the degree of freedom in irradiation in the depth direction can be increased without using a bolus as in the first embodiment, and the IMRT over-irradiation problem in the particle beam therapy system can be solved.

Embodiment 4 FIG.
FIG. 9 is a block diagram showing a columnar irradiation field generating apparatus according to Embodiment 4 of the present invention. The columnar irradiation field generating device 4a of the first embodiment is different in that the energy changing device 2a and the depth direction irradiation field expanding device 3a are integrated.

  The columnar irradiation field generation device 4b includes two range shifters 9a and 9b, two ridge filters 19a and 19b, and upstream deflection that moves the position where the charged particle beam 1 passes through the range shifters 9a and 9b and the ridge filters 19a and 19b. The charged particle beam 1 that has passed through the deflection electromagnets 5 and 6 constituting the electromagnet pair, the first deflection electromagnet power source 20 that excites the upstream deflection electromagnet pair, the range shifters 9a and 9b, and the ridge filters 19a and 19b is put on the original trajectory. Based on the energy command value input from the deflection electromagnets 7 and 8 constituting the returning downstream deflection electromagnet pair, the second deflection electromagnet power source 21 for exciting the downstream deflection electromagnet pair, and the irradiation control device 33, the upstream deflection electromagnet pair. The change control device that calculates the amount of movement of the charged particle beam trajectory by means of and transmits the excitation current value to the first deflection electromagnet power source 20 Equipped with a 2. The change control device 22 also controls the second bending electromagnet power source 21. Since the operation of each device is the same as in the first embodiment, it will not be repeated.

  The range shifters 9a and 9b are of the same shape and material, and the ridge filters 19a and 19b are examples composed of roughly triangular prisms having different heights. Since the height of the approximate triangular prism of the ridge filter 19b is higher than the height of the approximate triangular prism of the ridge filter 19a, the width of the SOBP of the charged particle beam 1 is greater when passing through the ridge filter 19a than when passing through the ridge filter 19b. Can be wider.

  Since the columnar irradiation field generation device 4b according to the fourth embodiment changes the charged particle beam 1 to the desired energy with the widths of the two types of SOBP, the two types of the shot irradiation field can be set to the desired range. . For each of the range shifters 9a and 9b and the ridge filters 19a and 19b, there is no upstream deflection electromagnet pair and downstream deflection electromagnet pair, and only one set of upstream deflection electromagnet pair and downstream deflection electromagnet pair is provided. Therefore, the length of the apparatus in the irradiation direction (Z direction) of the charged particle beam 1 can be shortened as compared with the columnar irradiation field generation apparatus 4a of the first embodiment. Since the upstream deflecting electromagnet pair and the downstream deflecting electromagnet pair are used to change the energy to the desired energy with two types of SOBP width, the driving sound for driving the range shifter and the ridge filter is generated when the SOBP width and range are changed. There is a merit that does not occur. In order to make the widths of many kinds of SOBP more than two kinds uniform, the range shifter 9 and the ridge filter 19 corresponding to the number of kinds may be arranged.

  The particle beam irradiation apparatus (see FIG. 1) having the columnar irradiation field generation apparatus 4b according to the fourth embodiment performs multiple portal irradiation based on the treatment plan corresponding to the treatment plan created by the treatment planning apparatus shown in the first embodiment. Since it can be executed, the degree of freedom in irradiation in the depth direction can be increased without using a bolus as in the first embodiment, and the IMRT over-irradiation problem in the particle beam therapy system can be solved.

Embodiment 5 FIG.
The fifth embodiment of the present invention is a particle beam therapy system provided with the particle beam irradiation apparatus described in the first to fourth embodiments. FIG. 10 is a schematic configuration diagram of a particle beam therapy system according to Embodiment 5 of the present invention. The particle beam therapy apparatus 51 includes an ion beam generator 52, an ion beam transport system 59, and particle beam irradiation apparatuses 58a and 58b. The ion beam generator 52 includes an ion source (not shown), a pre-accelerator 53, and a synchrotron 54. The particle beam irradiation device 58b is installed in a rotating gantry (not shown). The particle beam irradiation device 58a is installed in a treatment room having no rotating gantry. The role of the ion beam transport system 59 is in communication between the synchrotron 54 and the particle beam irradiation devices 58a and 58b. A part of the ion beam transport system 59 is installed in a rotating gantry (not shown), and the part has a plurality of deflection electromagnets 55a, 55b, and 55c.

  A charged particle beam, which is a particle beam such as a proton beam generated by an ion source, is accelerated by the pre-stage accelerator 53 and is incident on the synchrotron 54. The charged particle beam is accelerated to a predetermined energy. The charged particle beam emitted from the synchrotron 54 is transported to the particle beam irradiation devices 58a and 58b through the ion beam transport system 59. The particle beam irradiation devices 58a and 58b irradiate the affected part (not shown) of the patient with a charged particle beam.

  The particle beam therapy system 51 according to the fifth embodiment receives a charged particle beam from a patient based on a treatment plan created by the particle beam irradiation apparatus described in the first to fourth embodiments and the treatment plan apparatus described in the first embodiment. Therefore, the IMRT over-irradiation problem in the particle beam therapy system can be solved by increasing the degree of freedom of irradiation in the depth direction without using a bolus.

  The particle beam therapy system 51 according to the fifth embodiment irradiates the beam with a columnar dose distribution, and therefore has an advantage that the irradiation time is shorter than that in the point irradiation. In addition, since multiportal irradiation is possible, when the same affected area is irradiated, damage to the body surface, which is a normal tissue, can be reduced, and irradiation to a dangerous site (spinal cord, eyeball, etc.) that should not be irradiated can be avoided.

  Furthermore, the particle beam therapy system 51 of the fifth embodiment has an advantage that multi-port irradiation can be performed remotely. Remote multi-port irradiation means that a technician or the like does not need to enter a treatment room and operate a rotating gantry, and remotely irradiates a particle beam by changing the irradiation direction to an affected area in multiple directions from outside the treatment room. As described above, the particle beam therapy system according to the present invention is a simple irradiation system that does not require an MLC or a bolus, so that a bolus replacement operation and an MLC shape confirmation operation are not required. As a result, remote multi-port irradiation can be performed, and the effect that treatment time is significantly shortened can be obtained.

  The columnar irradiation field generating device 4 can also use the energy changing device 2b shown in the second embodiment and the depth direction irradiation field expanding device 3b shown in the third embodiment.

  The treatment planning apparatus according to the present invention can be suitably applied to a particle beam treatment apparatus used for medical purposes. The particle beam therapy system according to the present invention can be suitably used in medicine. In particular, it can solve the problem of IMRT that causes excessive irradiation and contributes to the development of the medical industry.

DESCRIPTION OF SYMBOLS 1 Charged particle beam 2 Energy change apparatus 2a Energy change apparatus 2b Energy change apparatus 3 Depth direction irradiation field expansion apparatus 3a Depth direction irradiation field expansion apparatus 3b Depth direction irradiation field expansion apparatus 4 Columnar irradiation field production | generation apparatus 4a Columnar irradiation wild Generating device 4b Column irradiation field generating device 5 Bending electromagnet 6 Bending electromagnet 7 Bending electromagnet 8 Bending electromagnet 9 Range shifter 9a Range shifter 9b Range shifter 14 Beam shaft 15 Bending magnet 16 Bending electromagnet 17 Bending magnet 18 Bending electromagnet 19 Ridge filter 19a Ridge filter 19b Ridge filter 19b 22 Change Control Device 25 Change Control Device 26a Absorber 26b Absorber 26c Absorber 26d Absorber 27a Drive Device 27b Drive Device 27c Drive Device 27d Drive Device 28a Ridge Filter 28b Ridge Filter 28c Ridge Filter 28d Ridge filter 29a Driving device 29b Driving device 29c Driving device 29d Driving device 34 Scanning irradiation system 40 Affected part 44a Columnar irradiation field 44b Columnar irradiation field 44c Columnar irradiation field 44d Columnar irradiation field 45a Columnar irradiation field 45b Columnar irradiation field 45c Columnar irradiation field 45c 45d Columnar irradiation field 52 Ion beam generator 54 Synchrotron 58 Particle beam irradiation device 58a Particle beam irradiation device 58b Particle beam irradiation device

Claims (3)

An ion beam generator for generating a charged particle beam and accelerating it to a predetermined energy by an accelerator, an ion beam transport system for transporting a charged particle beam accelerated by the ion beam generator, and transported by the ion beam transport system A particle beam treatment apparatus comprising: a particle beam irradiation apparatus that irradiates an irradiation target with the charged particle beam; and a rotating gantry that rotates an irradiation direction of the particle beam irradiation apparatus,
The particle beam irradiation apparatus includes an X-direction scanning magnet and a Y-direction scanning magnet that scan a charged particle beam accelerated by the accelerator in an X direction and a Y direction perpendicular to the irradiation direction, respectively, in the X direction and the Y direction. A scanning irradiation system for scanning, and a columnar irradiation field generating device for expanding a Bragg peak of the charged particle beam and generating a columnar irradiation field,
The columnar irradiation field generator is
A first range shifter that has a thickness in a direction in which the charged particle beam passes differs depending on a location, and that reduces energy of the charged particle beam that passes through the thickness;
A first ridge filter disposed on the downstream side of the first range shifter and having a thickness distribution with different energy loss depending on a position through which the charged particle beam passes;
A second range shifter that reduces the energy of the charged particle beam that passes through the thickness in the direction in which the charged particle beam passes;
A second ridge filter disposed downstream of the second range shifter, having a thickness distribution in which energy lost depending on a position through which the charged particle beam passes and having a height different from that of the first ridge filter; When,
An upstream deflection electromagnet pair that moves the passing position of the charged particle beam in the first range shifter and the first ridge filter or the passing position of the charged particle beam in the second range shifter and the second ridge filter. A pair of downstream deflecting electromagnets for returning the trajectory of the charged particle beam toward the beam axis incident on the columnar irradiation field generating device, the charged particle beam with the predetermined thickness of the first range shifter, and the first So as to pass through a predetermined thickness distribution of the ridge filter, or to pass the charged particle beam through a predetermined thickness of the second range shifter and a predetermined thickness distribution of the second ridge filter. A change control device for controlling the upstream deflection electromagnet pair and the downstream deflection electromagnet pair;
A treatment planning device for creating a treatment plan for the particle beam treatment device,
The columnar irradiation field is the width of the SOBP in which the height of the columnar irradiation field is the width in the irradiation direction of the charged particle beam, and the length of the cross section perpendicular to the axis in the height direction of the columnar irradiation field. Is a beam size that is the width of the charged particle beam in the X direction and the Y direction, and the height of the columnar irradiation field is an irradiation field longer than the beam size,
The beam size is a single size selected in a single treatment irradiation,
According to the distal shape of the irradiation target irradiated with the charged particle beam, the outer columnar irradiation field that is the columnar irradiation field having the width of one SOBP is arranged, and the outer columnar shape is disposed inside the irradiation target. An irradiation field arrangement section that lays out and arranges an inner columnar irradiation field that is the columnar irradiation field having a width of the SOBP different from the irradiation field;
The state where the outer columnar irradiation field and the inner columnar irradiation field are spread by the irradiation field arrangement unit is set as an initial state, and the outer columnar irradiation field and the inner side are set so that the irradiation dose to the irradiation target falls within a predetermined range. A particle beam therapy system comprising: an optimization calculation unit that adjusts an arrangement of columnar irradiation fields. An ion beam generator for generating a charged particle beam and accelerating it to a predetermined energy by an accelerator, an ion beam transport system for transporting a charged particle beam accelerated by the ion beam generator, and transported by the ion beam transport system A particle beam treatment apparatus comprising: a particle beam irradiation apparatus that irradiates an irradiation target with the charged particle beam; and a rotating gantry that rotates an irradiation direction of the particle beam irradiation apparatus,
The particle beam irradiation apparatus includes an X-direction scanning magnet and a Y-direction scanning magnet that scan a charged particle beam accelerated by the accelerator in an X direction and a Y direction perpendicular to the irradiation direction, respectively, in the X direction and the Y direction. A scanning irradiation system for scanning, and a columnar irradiation field generating device for expanding a Bragg peak of the charged particle beam and generating a columnar irradiation field,
The columnar irradiation field generator is
A first range shifter that has a thickness in a direction in which the charged particle beam passes differs depending on a location, and that reduces energy of the charged particle beam that passes through the thickness;
A first ridge filter disposed on the downstream side of the first range shifter and having a thickness distribution with different energy loss depending on a position through which the charged particle beam passes;
A second range shifter that reduces the energy of the charged particle beam that passes through the thickness in the direction in which the charged particle beam passes;
A second ridge filter disposed downstream of the second range shifter, having a thickness distribution in which energy lost depending on a position through which the charged particle beam passes and having a height different from that of the first ridge filter; When,
An upstream deflection electromagnet pair that moves the passing position of the charged particle beam in the first range shifter and the first ridge filter or the passing position of the charged particle beam in the second range shifter and the second ridge filter. A pair of downstream deflecting electromagnets for returning the trajectory of the charged particle beam toward the beam axis incident on the columnar irradiation field generating device, the charged particle beam with the predetermined thickness of the first range shifter, and the first So as to pass through a predetermined thickness distribution of the ridge filter, or to pass the charged particle beam through a predetermined thickness of the second range shifter and a predetermined thickness distribution of the second ridge filter. A change control device for controlling the upstream deflection electromagnet pair and the downstream deflection electromagnet pair;
A treatment planning device for creating a treatment plan for the particle beam treatment device,
The columnar irradiation field is the width of the SOBP in which the height of the columnar irradiation field is the width in the irradiation direction of the charged particle beam, and the length of the cross section perpendicular to the axis in the height direction of the columnar irradiation field. Is a beam size that is the width of the charged particle beam in the X direction and the Y direction, and the height of the columnar irradiation field is an irradiation field longer than the beam size,
The beam size is a single size selected in a single treatment irradiation,
According to the distal shape of the irradiation target irradiated with the charged particle beam, the outer columnar irradiation field that is the columnar irradiation field having the width of one SOBP is arranged, and the outer columnar shape is disposed inside the irradiation target. An irradiation field arrangement section that lays out and arranges an inner columnar irradiation field that is the columnar irradiation field having a width of the other SOBP smaller than the irradiation field;
The state where the outer columnar irradiation field and the inner columnar irradiation field are spread by the irradiation field arrangement unit is set as an initial state, and the outer columnar irradiation field and the inner side are set so that the irradiation dose to the irradiation target falls within a predetermined range. A particle beam therapy system comprising: an optimization calculation unit that adjusts an arrangement of columnar irradiation fields. The irradiation field arrangement unit arranges the outer columnar irradiation field in accordance with the distal shape of the irradiation target, and then performs the inner columnar irradiation in accordance with an inner shape in which the outer columnar irradiation field in the irradiation target is not disposed. The particle beam therapy apparatus according to claim 1, wherein a field is disposed.

Images