JP2014028310A - Particle beam irradiation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an irradiation target with a dose distribution with higher accuracy at a higher speed in a particle beam irradiation system.SOLUTION: A particle beam irradiation system comprises: scanning deflection electromagnets that deflect a particle beam and perform scanning; and an energy width expansion apparatus that expands an energy width of the particle beam by causing the particle beam to pass therethrough and forms an SOBP in a depth direction serving as an irradiation direction of the particle beam of an irradiation target without changing energy of the particle beam generated by a particle beam generation section. The energy width expansion apparatus is configured so as to form the SOBP in the depth direction along whole irradiation area in the depth direction of the irradiation target without changing parameters. The energy width expansion apparatus is further configured so as to control the scanning deflection electromagnets such that an irradiation spot formed by the particle beam on the irradiation target is moved in a stepwise manner along whole irradiation area in a lateral direction of the irradiation target.

Description

  The present invention relates to a particle beam irradiation system that applies a particle beam such as irradiating a particle beam to treat cancer.

  One of the applications of radiation is cancer treatment, and recently, particle beam therapy for irradiating a cancer cell with a heavy particle beam such as a proton beam or a carbon beam has attracted attention. First, the characteristics of particle beam irradiation for irradiating a particle beam to kill cancer cells will be described. When various types of radiation beams are irradiated on a human body, the dose distribution in the body of the radiation beams changes as shown in FIG. As shown in FIG. 15, among various types of radiation, photon rays such as X-rays and gamma rays have a maximum relative dose near the surface of the body, the depth from the surface of the body increases, and the relative dose is descend. On the other hand, particle beams such as proton beams and carbon beams are deep portions from the surface of the body, and the relative dose reaches a peak value at a position where the particles stop, that is, immediately before the range of the particle beam. This peak value is called a Bragg peak BP.

  In the particle beam cancer treatment method, the Bragg peak BP is irradiated to a tumor formed in a human organ to treat the cancer. In addition to cancer, it can also be used to treat deep parts of the body. A treated site including a tumor is generally called an irradiation target. The position of the black peak BP is determined by the energy of the irradiated particle beam. The higher the energy of the particle beam, the deeper the Bragg peak BP. In the particle beam therapy, it is necessary to make the particle beam have a uniform dose distribution over the entire irradiation target. In order to give this Bragg peak BP to the entire irradiation target, “expansion of irradiation volume” of the particle beam is performed. .

  This “expansion of irradiation volume” is carried out in three directions of X axis, Y axis and Z axis which are orthogonal to each other. When the irradiation direction of the particle beam is the Z-axis direction, “expansion of irradiation volume” is to first expand the irradiation region in the X / Y-axis direction, and in the lateral direction orthogonal to the depth direction. This is called irradiation field expansion because the irradiation area is expanded. The second “expansion of irradiation volume” is performed in the Z-axis direction and is called irradiation volume expansion in the depth direction.

  In the irradiation volume expansion in the depth direction, since the width of the Bragg peak BP in the particle beam irradiation direction is narrower than the expansion in the depth direction of the irradiation target, the Bragg peak BP in the particle beam irradiation direction is reduced in depth. It is done to enlarge in the direction of. On the other hand, expansion of the irradiation field in the horizontal direction is generally such that the distribution size of the particle beam accelerated by the accelerator is smaller than the size of the irradiation target in the direction orthogonal to the irradiation direction. Is performed in order to enlarge in a direction orthogonal to Various methods have been proposed so far for the methods of expanding the irradiation field in the depth direction and expanding the irradiation field in the lateral direction. Recently, there is a scanning irradiation method (Scanning Irradiation).

  In the scanning irradiation method, as a lateral irradiation field expansion method, the particle beam is scanned in the XY plane direction using a deflecting electromagnet provided upstream of the particle beam irradiation unit of the particle beam irradiation apparatus, and the irradiation position of the particle beam A method of obtaining a wide irradiation field by moving the beam with time is used. In this method, a uniform dose distribution can be obtained by appropriately overlapping adjacent irradiation spots of a pencil beam having a small diameter. As a pencil beam scanning method, there are a raster method in which scanning is performed continuously with respect to time, a spot method in which scanning is performed stepwise with respect to time, and a method in which the raster method and the spot method are combined.

  As the irradiation volume expansion method in the depth direction, a method of controlling the energy of the particle beam itself irradiated from the particle beam irradiation apparatus is used. In this method, the energy of the particle beam is controlled by changing the acceleration energy of the accelerator that accelerates the particle beam, or by inserting an instrument called a range shifter across the particle beam, Change the energy of the particle beam. There is also a method of using these accelerators in combination with a range shifter.

  In this irradiation volume expansion method in the depth direction, the particle beam is changed to the particle beam energy after irradiating one irradiation layer of the irradiation target volume with the Bragg peak BP as a beam having a predetermined intensity of energy. The Bragg peak BP is irradiated to the irradiation layer next to the irradiation target volume. By repeating such operations a plurality of times and irradiating a plurality of irradiation layers with a Bragg peak BP of a particle beam, an expanded Bragg peak SOBP (Spread-out Bragg Peak) having a desired width in the beam irradiation direction is obtained. Can do. (For example, Patent Document 1)

  A particle beam irradiation method combining the above-described lateral irradiation field expansion method and depth direction irradiation volume expansion method is a method generally called scanning irradiation method.

  In addition, in order to compensate for the deviation of irradiation due to the movement of the affected part due to the patient's breathing, a method has been proposed in which each irradiation layer is divided in time and irradiated multiple times at the same spot position (for example, a patent) Reference 2 FIG. 11). Further, Patent Document 2 proposes a technique for controlling the irradiation dose in synchronization with the respiration phase in consideration of the movement of the affected part due to respiration.

JP 2006-87649 A International Publication WO 2006/082651 (Fig. 11)

In the conventional scanning irradiation method described above, since it is necessary to change the particle beam energy a plurality of times for irradiation, it takes time to change the energy, and it is difficult to shorten the irradiation time.
An object of the present invention is to solve such a problem and to provide a higher-speed and more accurate dose distribution in a particle beam irradiation system based on a scanning irradiation method.

  The particle beam irradiation system according to the present invention generates a beam at the particle beam generation unit by expanding the energy width of the particle beam after passing through the scanning deflection electromagnet for deflecting and scanning the particle beam and passing the particle beam. And an energy width expanding device for forming SOBP in the depth direction that is the irradiation direction of the target particle beam without changing the energy of the particle beam, and the energy width expanding device changes the parameter The SOBP is formed in the depth direction over the entire irradiation region in the depth direction of the irradiation target, and the irradiation spot formed by the particle beam on the irradiation target is set as the irradiation region in the lateral direction of the irradiation target. The scanning deflecting electromagnet is controlled so as to be moved stepwise throughout.

  In scanning irradiation that irradiates the irradiation target by moving the irradiation spot formed by the particle beam in the lateral direction, irradiation is performed over the entire irradiation region in the depth direction of the irradiation target without changing the energy, so in a short time It is possible to provide a particle beam irradiation system that can complete irradiation and can provide a highly accurate dose distribution according to an irradiation target.

It is a figure explaining the irradiation area | region of the particle beam irradiation system by Embodiment 1 of this invention. It is a bird's-eye view which shows schematic structure of the whole particle beam irradiation system by Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the particle beam irradiation system by Embodiment 1 of this invention. It is a diagram which shows the example of SOBP expanded by the particle beam irradiation system by Embodiment 1 of this invention. It is a flowchart at the time of particle beam irradiation of the particle beam irradiation system by Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the particle beam irradiation system by Embodiment 2 of this invention. It is a block diagram which shows the structural example of the displacement phase detection part of the particle beam irradiation system by Embodiment 2 of this invention. It is a diagram explaining operation | movement of the particle beam irradiation system by Embodiment 2 of this invention. It is a block diagram which shows schematic structure of the particle beam irradiation system by Embodiment 3 of this invention. It is a 1st diagram explaining the example of SOBP expanded by the particle beam irradiation system by Embodiment 3 of this invention. It is a 2nd diagram explaining the example of SOBP expanded by the particle beam irradiation system by Embodiment 3 of this invention. It is a figure explaining the irradiation area | region of the particle beam irradiation system by Embodiment 3 of this invention. It is a block diagram which shows schematic structure of the particle beam irradiation system by Embodiment 4 of this invention. It is a diagram explaining operation | movement of the particle beam irradiation system by Embodiment 5 of this invention. It is a figure which shows dose distribution in the body of the radiation at the time of irradiating a human body with various radiation.

Embodiment 1 FIG.
2 is a bird's-eye view showing a schematic configuration of the whole particle beam irradiation system according to the first embodiment of the present invention, and FIG. 3 is a particle beam irradiation according to the first embodiment shown by adding a control device to the whole configuration of the bird's-eye view of FIG. 1 is a block diagram of a schematic configuration of a system. As shown in FIGS. 2 and 3, the particle beam irradiation system according to the first embodiment includes a particle beam generation unit 10, a particle beam transport unit 20, two particle beam irradiation units 30A and 30B, and the like. In FIG. 2, a system in which two green particle irradiation units are typically obtained is shown, but there may be more particle beam irradiation units or a single particle beam irradiation unit. In FIG. 3, only one particle beam irradiation unit is provided as the particle beam irradiation unit 30 for simplicity. For operational reasons such as radiation safety management, the particle beam generator 10 and the particle beam irradiation units 30A and 30B are installed in a shielded room. The particle beam transport unit 20 connects the particle beam generator 10 and the particle beam irradiation units 30A and 30B. The particle beam transport unit 20 includes particle beam transport paths 21 and 22 that transport the particle beam generated by the particle beam generation unit 10 to the particle beam irradiation units 30A and 30B, respectively. The particle beam transport unit 20 includes a deflecting electromagnet 50 for changing the direction of the particle beam, and is configured so that the particle beam passes through the vacuum duct. The particle beam irradiation units 30A and 30B are configured to irradiate the target site of the patient with the particle beam PB. Hereinafter, the particle beam irradiation units 30A and 30B will be described as the particle beam irradiation unit 30.

  The particle beam generator 10 includes an injector 11 and an accelerator 12. The injector 11 generates particles having a large mass such as a proton beam or a carbon beam. The accelerator 12 accelerates the particles generated by the injector 11 and emits the particle beam PB. The accelerator 12 is controlled by a signal from the accelerator controller 13 provided in the irradiation controller 80. The accelerator controller 13 supplies an energy control signal to the accelerator 12, sets acceleration energy, sets energy of the particle beam PB emitted from the accelerator 12, and controls time and intensity for emitting the particle beam PB. To do.

  The particle beam irradiation unit 30 constitutes a treatment room. The particle beam irradiation unit 30 includes an irradiation nozzle 40, a treatment table 32, and the like. The treatment table 32 is used to hold the patient in a supine or sitting position. The irradiation nozzle 40 irradiates the particle beam PB transported to the particle beam irradiation unit 30 toward the irradiation target of the patient on the treatment table 32.

  In FIG. 3, the specific structure of the irradiation nozzle 40 of the particle beam irradiation part 30 in Embodiment 1 is shown. The irradiation nozzle 40 shown in FIG. 3 includes a beam diameter changer 44 for changing the beam diameter of the particle beam PB. As the beam diameter changing device, for example, various devices such as a device using a quadrupole electromagnet, a device using a thin scatterer, and changing the beam diameter at the irradiation target by changing the thickness of the scatterer can be used. If there is no need to change or select the beam diameter, the beam diameter changer 44 may be omitted. The irradiation nozzle 40 scans together the scanning deflection electromagnets 41a and 41b (41a and 41b) that scan the particle beam PB after the beam diameter change in the horizontal direction, that is, the X and Y planes orthogonal to the irradiation direction of the particle beam PB. A scanning deflection electromagnet drive power source 45 for driving the scanning deflection electromagnet 41, a dose monitor 42 for monitoring the irradiation dose of the particle beam PB, and an energy width of the particle beam PB. A ridge filter 43 which is an energy width expanding device. In addition, for example, a beam position monitor is also provided, but it is omitted because it is not directly related to the present invention.

  The ridge filter 43 reduces the energy of the particle beam passing therethrough. However, since the thickness of the particle beam passing through the ridge filter 43 varies depending on the location, the particle beam after passing as a whole is the particle before passing through. The energy width is wider than the energy width of the line. Therefore, when the particle beam after passing through the ridge filter 43 is irradiated into the body, for example, the position of the Bragg peak BP, that is, the range of the particle beam is expanded. An example of an enlarged Bragg peak BP (SOBP) (Spread-out Bragg Peak) is shown in FIG. In FIG. 4, the SOBP is about 10 cm. If the ridge filter forming the SOBP in FIG. 4 is used, an irradiation target having a width of 10 cm in the depth direction can be irradiated.

  Next, the operation of the particle beam irradiation system of FIG. 3 will be described. First, in the treatment planning unit 60, the irradiation dose distribution for each patient is determined and the data is stored. The irradiation control calculation unit 70 determines the irradiation dose of each irradiation spot based on the irradiation dose distribution data, and outputs the data to the irradiation dose controller 14 of the irradiation control unit 80. Further, the irradiation control calculation unit 70 also determines the energy and spot size of the particle beam that the accelerator 12 should emit, and outputs the data to the accelerator controller 13 and the spot size controller 15. Thus, preparation before irradiation is completed.

Next, FIG. 1 shows an image of the irradiation area when the irradiation target is actually irradiated with the particle beam. 1A indicates each irradiation spot, and the numbers in the circles indicate the order in which the irradiation spots are scanned. FIG. 1B shows a cross section taken along the line AA of FIG. A flowchart at the time of irradiation is shown in FIG. First, the accelerator 12, the beam diameter changer 44, and the like are set through the irradiation control unit 80 so that the energy, spot size, and the like determined by the irradiation control calculation unit 70 in the preparation stage become determined values (ST1). Next, the beam scanning controller 16 controls the scanning deflection electromagnet drive power supply 45 to set the excitation current of the scanning deflection electromagnet 41 so that the position of the irradiation spot 1 is irradiated with the particle beam PB (ST2). After the setting of the excitation current is completed, the particle beam is emitted from the accelerator 12 (ST3), and irradiation is started. When irradiation is started, the dose irradiated by the dose monitor 42 is counted. The dose count value is sent to the irradiation dose controller 14. The irradiation dose controller 14 receives the necessary irradiation dose value at each irradiation spot from the irradiation control calculation unit 70, and when the dose count value reaches the necessary irradiation dose value for each irradiation spot, the irradiation control calculation unit 70 (ST4). When the dose at the irradiation spot expires, the irradiation control calculation unit 70 sends a command to the beam scanning controller 16 to move the particle beam to the next irradiation spot, and the excitation current of the scanning deflection electromagnet 41 is changed to the next. The exciting current corresponding to the irradiation spot is set (ST6). This operation is repeated until the irradiation of the final irradiation spot (irradiation spot n in FIG. 1) is completed (ST5).

  The region irradiated as described above is as shown in FIG. The irradiated region is the entire region formed by moving the irradiation spot stepwise by the scanning deflecting electromagnet 41 in the horizontal direction, that is, the XY direction, and the depth direction, that is, the Z direction is expanded by the ridge filter 43. It becomes a region corresponding to the enlarged Bragg peak due to the energy of the particle beam. According to a normal ridge filter, the energy width of the particle beam is the same in the entire XY region, and therefore, a region having a constant width in the Z direction is an irradiation region. Therefore, a columnar region is an irradiation region for each irradiation spot, and all irradiation regions by all the irradiation spots are also cylindrical regions having a constant depth direction. When the shape of the affected area is close to a cylindrical shape, the energy is changed by setting the energy of the particle beam emitted from the accelerator 12 and the ridge filter 43 so that the enlarged Bragg peak matches the depth of the affected area. Irradiation can be completed without any problems. In the conventional spot scanning irradiation, the energy of the particle beam to be irradiated is sequentially changed to form a plurality of layered irradiation regions in the depth direction so that the entire region is irradiated. In this method, it is necessary to sequentially change the energy, and it is necessary to change the parameter setting of the accelerator 12 or change the parameters of the range shifter to be inserted after emission from the accelerator 12. It was over. On the other hand, according to the present invention, it is not necessary to change the energy of the particle beam, and the entire region can be irradiated by one scanning in the XY direction, so that irradiation can be performed in a short time and the burden on the patient can be reduced. effective.

Embodiment 2. FIG.
FIG. 6 is a block diagram of a schematic configuration of the entire particle beam irradiation system according to the second embodiment of the present invention. 6, the same reference numerals as those in FIG. 3 denote the same or corresponding parts. In the second embodiment, as shown in FIG. 6, a displacement phase detector 90 is provided, and a displacement signal of the position of the affected part detected by the displacement phase detector 90 is output to the irradiation control calculator 70. is there. The displacement phase detector 90 measures the respiration of the patient or the position of the irradiation target, and determines the position of the affected area based on the respiration measurement or the position detection of the irradiation target. The irradiation control calculation unit 70 controls the irradiation control unit 80 so as to perform particle beam irradiation in synchronization with the determined phase of the moving period of the affected part. Since the position of the irradiation target changes due to patient breathing or the like, the irradiation position of the particle beam changes, and the irradiation accuracy decreases. Since the change in the position of the irradiation target is small during exhalation or the like, irradiation with high accuracy can be performed by performing irradiation during this period. In the second embodiment, irradiation is performed over the entire XY irradiation region with one expiration. This enables irradiation with very high accuracy.

  FIG. 7 is a block diagram showing details of an example of the displacement phase detector 90. The respiration measuring unit 91 measures respiration of the patient 100 and outputs a respiration signal BS, and can use a conventional particle beam irradiation system or an X-ray CT. A light emitting diode (LED) is attached to the respiration measuring unit 91 on the abdomen or chest of the patient 100, and the respiration is measured by the displacement of the light emitting position of the light emitting diode, and the body displacement is measured by a laser beam using a reflection device. A method of attaching a telescopic resistor to the patient's abdomen and measuring a change in its electrical characteristics, a method of directly measuring the breathing of the patient 100, and the like.

  The irradiation target position detection unit 93 detects the position of the irradiation target in the patient 100 and outputs a respiratory signal BS. As the irradiation target position detection unit 93, X-ray sources 931 and 932 and X-ray image acquisition devices 941 and 942 corresponding thereto are used. The X-ray sources 931 and 932 emit X-rays toward the irradiation target in the patient 100, and the X-ray image acquisition devices 941 and 942 acquire X-ray images from the X-ray sources 931 and 932, The position of the irradiation target is detected. As the X-ray image acquisition apparatuses 941 and 942, for example, an X-ray television apparatus using an image intensifier or a method of measuring a scintillator plate with a CCD camera is used. There is a method of embedding a small piece of metal such as gold in advance as a marker at an important point corresponding to the irradiation target. By using this marker, the position of the irradiation target can be easily specified.

  Both the respiration measuring unit 91 and the irradiation target position detecting unit 93 detect the displacement of the irradiation target accompanying respiration and generate a respiration signal BS. Both of these respiration signals BS are input to the affected part position determination unit 95. The affected part position determination unit 95 determines the respiratory displacement in real time from the input respiratory signal BS based on the expiration / inspiration correlation stored in the memory, and outputs the status signal SS to the irradiation control calculation unit 70. To do.

  An outline of the operation of the displacement phase detector 90 is shown in the diagram of FIG. The diagram in FIG. 8A shows, for example, the respiratory displacement of the irradiation target, and the diagram in FIG. 8B shows a status signal as a result of determination based on this displacement. The horizontal broken line in the diagram of FIG. 8A indicates a predetermined threshold value. When the displacement is equal to or smaller than the predetermined threshold value, the affected area position determination unit 95 can irradiate a status signal as shown in FIG. A signal indicating the state is output. The irradiation control calculation unit 70 controls irradiation based on the status signal as follows.

  First, prior to irradiation, organ movement due to the patient's respiratory motion or the like is measured by the displacement phase detection unit 90 to obtain phase data of the movement period of the affected part. That is, the status signal data output from the displacement phase detector 90 is registered in the irradiation control calculator 70. The irradiation control calculation unit 70 evaluates the time length of the status signal in the movement of the affected part (hereinafter referred to as one gate length) by, for example, a plurality of registered one gate lengths, and all the irradiation spots of the affected part within one gate length. Irradiation parameters such as irradiation dose rate (intensity) at each irradiation spot are determined by calculation. The irradiation dose rate is obtained by dividing the irradiation dose at each irradiation spot by the irradiation allowable time at each spot. The irradiation allowable time is obtained by the product of the irradiation time in one gate length and the irradiation ratio for each spot in the entire irradiation. Irradiation is performed after the irradiation parameters are determined, and irradiation is performed using the determined irradiation parameters while the status signal SS is output (between one gate). FIG. 8C shows an image of actually irradiating each irradiation spot by enlarging one gate length. As shown in FIG. 8C, the irradiation spots 1 to n are all irradiated within one gate length. For example, assuming that the number of irradiation spots is 500 and the gate length is 1 second, the total irradiation time is 1 gate length or less, for example, 0.5 seconds, and the irradiation time of one irradiation spot is about 1 ms. Determine the parameters.

Depending on the dose of the particle beam that can be extracted from the accelerator 12 and the size of the irradiation target, for example, the size of the irradiation target is 5 cm × 5 cm × 5 cm, the irradiation dose is a biological dose of 5 GyE, and the spot size is φ2.5 mm. Then, it is practically possible to irradiate all irradiation spots with the necessary dose in 0.5 seconds with a total number of irradiation spots of about 500. At this time, the depth direction is set such that the parameter of the ridge filter 43 is set so that the SOBP has a width of 5 cm at a predetermined depth, so that the energy of the particle beam is not changed. Irradiation can also be realized. Therefore, since irradiation of all irradiation spots can be completed with one gate, it is possible to perform irradiation with minimal movement of the irradiation target during irradiation, and to realize irradiation with extremely high accuracy.

  In addition, although the example which can irradiate required irradiation dose to all irradiation area | regions within 1 gate was demonstrated above, the required irradiation dose does not necessarily need to be irradiated within 1 gate. For example, with the amount of particle beam that can be extracted from the accelerator with one acceleration, for example, in the above example, when it is not possible to irradiate the entire irradiation region with 5 GyE, the irradiation is performed by dividing the irradiation into multiple times. The region can be irradiated with 5 GyE. When the necessary irradiation dose is 5 GyE, when the irradiation control calculation unit 70 evaluates that 3 GyE can be irradiated to the entire irradiation region with the amount of particle beam that can be extracted from the accelerator by one acceleration, All the irradiation spots are irradiated with one gate by the particle beam by the first acceleration in the accelerator, and a dose of 3 GyE is given to the irradiation target. Next, all irradiation spots are again irradiated into one gate after the second acceleration by the particle beam generated by the second acceleration, and a dose of 2 GyE is given to the irradiation target. In this way, a total dose of 5 GyE can be given by irradiating all irradiation spots at each gate using the time of two gates. In this way, it is not always necessary to irradiate the entire dose within one gate, and irradiation may be performed in a plurality of gates. However, it is necessary to irradiate all irradiation spots in one gate and irradiate all irradiation spots in the next gate. Since all the irradiation spots are irradiated with one gate, it is possible to realize irradiation with high accuracy for each suction gate, and therefore, an irradiation dose with high accuracy can be obtained for the total.

Embodiment 3 FIG.
FIG. 9 is a block diagram showing a schematic configuration of a particle beam irradiation system according to Embodiment 3 of the present invention. 9, the same reference numerals as those in FIGS. 3 and 6 denote the same or corresponding parts. In the first embodiment and the second embodiment, a constant SOBP is formed in the depth direction by the ridge filter 43. Since the shape of the affected part is various, the application range is narrow only by forming a constant SOBP in the depth method. In the third embodiment, as shown in FIG. 9, a cone ridge filter 431 and a bolus 46 are used as the energy width expanding device. The cone ridge filter 431 is formed by arranging a number of very thin spindles in the XY plane perpendicular to the beam traveling direction so that the beam traveling direction (Z direction) is an axis. As conceptually shown in FIG. 9, for example, by changing the height of the weight-like body, the influence of the passing particle beam differs in the XY plane, and the irradiation target is irradiated with a particle beam having a different energy width depending on the position. can do.

  FIG. 10 shows an example of SOBP formed by the particle beam after passing through the cone ridge filter 431. The solid curve indicated by A in FIG. 10 is the SOBP formed by the particle beam after passing when the particle beam passes through the portion (for example, the central portion) where the high weight spindles are arranged. Therefore, the SOBP is wide. The broken line curve indicated by B is a particle after passing when the particle beam passes through a portion (for example, the central peripheral portion) where a weight-like body having a lower height than the portion indicated by the curve A is disposed. The SOBP is formed by lines and is narrower than A. The curve of the alternate long and short dash line indicated by C indicates that when the particle beam passes through a portion (for example, a peripheral portion) where a weight-like body having a lower height than the portion indicated by the curve B is disposed, The SOBP is formed by particle beams and is narrower than B. The width of the SOBP varies depending on the height of the spindles arranged in this way. However, as the SOBP width increases, the irradiation dose (number of irradiated particles) necessary to obtain an equivalent dose at the SOBP center increases. The exposure dose must be adjusted according to the arrangement of the cone ridge filter. As described above, the scanning irradiation method is an optimal irradiation method as a method of adjusting the irradiation dose in accordance with the arrangement of the cone ridge filter.

  The particle beam that has passed through the cone ridge filter 431 passes through the bolus 46. The bolus is a limiter formed of resin or the like, and limits the energy of the particle beam passing through the bolus so that the range of the particle beam is limited in accordance with the depth shape of the irradiation target. When the particle beam whose energy width is widened by the cone ridge filter 431 shown in FIG. 10 passes through the bolus 46, the particle beam forms SOBP in the depth direction as shown in FIG. That is, for example, the particle beam that has passed through the central portion shown by the curve A in FIG. 10 also passes through the central portion of the bolus 46, and the energy is not so limited, like the curve shown by the solid line A1 in FIG. A wide SOBP up to a depth of 300 mm is formed. Further, the energy of the particle beam passing through the central peripheral portion shown by the curve B in FIG. 10 is limited by the bolus 46 and limited to a depth of about 270 mm as shown by the broken line B1 in FIG. A slightly narrower SOBP is formed. Furthermore, the energy of the particle beam that has passed through the peripheral portion shown by the curve C in FIG. 10 is greatly limited by the bolus 46, and is limited to a depth of about 250 mm as shown by the broken line C1 in FIG. Formed narrow SOBP. As described above, by using the cone ridge filter 431 and the bolus 46 having a distribution in the XY plane, an irradiation region having a distribution in the depth direction of the irradiation target can be formed.

  FIG. 12 shows an image of an irradiation region formed when scanning irradiation is performed in which the XY plane is scanned and irradiated by the particle beam irradiation system of FIG. The circles in FIG. 12A indicate the respective irradiation spots, as in FIG. 1A, and the numbers in the circles indicate the order in which the irradiation spots are scanned. FIG. 12B shows a cross section taken along the line AA in FIG. As shown in FIG. 12B, the irradiation area in the depth direction at each irradiation spot changes depending on the position, and the cone ridge filter 431 that is an energy width expanding device and the bolus 46 that is an energy limiter are used. Thus, it can be seen that the irradiation region in the depth direction can be a region that matches the shape of the irradiation target.

  Also in the third embodiment, as described in the second embodiment, the moving period of the affected part is evaluated, and irradiation parameters are set so that all irradiation spots are irradiated within one gate. Can be executed. Therefore, irradiation in the depth direction of the irradiation target can be realized without changing the energy of the particle beam, and irradiation of all irradiation spots can be completed with one gate, so movement of the irradiation target during irradiation is minimized. Irradiation can be suppressed to a very low level, and extremely accurate irradiation can be realized.

Embodiment 4 FIG.
FIG. 13 is a block diagram of a schematic overall configuration of a particle beam irradiation system according to Embodiment 4 of the present invention. In FIG. 13, the same reference numerals as those in FIGS. 3, 6 and 9 denote the same or corresponding parts. Various configurations are possible for forming a predetermined irradiation region in the depth direction without changing the energy of the particle beam, that is, for forming the SOBP. In FIG. 13, an irradiation region in the depth direction is formed using a ridge filter 43 and a bolus 46. Furthermore, a collimator such as a multi-leaf collimator (MLC) or a patient collimator may be used in order to form an irradiation region that matches the shape of the irradiation target in the lateral direction.

  In the conventional scanning irradiation method, the irradiation region in the depth direction is irradiated while changing the energy of the particle beam and forming a different irradiation region in the depth direction. On the other hand, in the present invention, using an energy width expansion device such as a ridge filter provided downstream of the scanning deflection electromagnet 41 or a bolus as an energy limiter, the entire irradiation target region in the depth direction is applied. The irradiation area is formed over the entire area. In this configuration, by forming the irradiation region in the horizontal direction by scanning irradiation for scanning the irradiation spot, for example, irradiation of the entire region of the irradiation target can be completed within one gate, thereby realizing highly accurate irradiation. be able to.

Embodiment 5 FIG.
FIG. 14 is a diagram for explaining the operation of the particle beam irradiation system according to the fifth embodiment of the present invention. FIGS. 14A, 14B, and 14C are similar to FIGS. 8A, 8B, and 8C. FIG. 14D shows the time change of the beam intensity emitted from the accelerator 12 corresponding to the enlarged time axis of FIG. 14C, and shows a state in which the particle beam is emitted from the accelerator. ing. For example, in the second embodiment, the entire irradiation region is irradiated with one gate, but the particle beam irradiation system according to the fifth embodiment synchronizes the timing of emitting the particle beam from the accelerator with the timing of irradiation. Is the operation.

  First, when the irradiation start time t0 in the gate comes, the remaining available time of the accelerator is calculated, and if the remaining available time does not satisfy the planned irradiation time in the gate, the emission is postponed. If the remaining available time satisfies the scheduled irradiation time in the gate, the emission is performed. By evaluating the moving period of the affected area and the operating period of the accelerator, it is possible to irradiate the entire irradiation region within the gate. Irradiating an irradiation region across a plurality of gates, in principle, generates a high-dose region and a low-dose region outside the planned dose distribution when there is a variation in position between moving periods of the affected area. Being able to irradiate the entire irradiation area within the gate leads to an improvement in the accuracy of the dose distribution.

10: Particle beam generator 11: Injector 12: Accelerator 13: Accelerator controller 14: Irradiation dose controller 15: Spot size controller 16: Beam scanning controller 20: Particle beam transport unit 30, 30A, 30B: Particle beam Irradiation unit 32: treatment table 40: irradiation nozzle 41, 41a, 41b: scanning deflection electromagnet 42: dose monitor 43: ridge filter (energy width expansion device)
431: Corn Ridge Filter (Energy Width Expansion Equipment)
44: Beam diameter changer 60: Treatment planning unit 70: Irradiation control calculation unit 80 Irradiation control unit 90: Displacement phase detection unit PB: Particle beam

Claims (4)

A particle beam generation unit equipped with an accelerator, an irradiation nozzle for irradiating the irradiation target with the particle beam generated by the particle beam generation unit, and an irradiation control unit for controlling the particle beam to be irradiated,
The irradiation nozzle deflects the particle beam in a two-dimensional direction orthogonal to the irradiation direction of the particle beam and scans the scanning deflection electromagnet, and passes the particle beam, thereby passing the particle beam after passing. The energy width for forming SOBP in the depth direction, which is the irradiation direction of the particle beam of the irradiation target, without changing the energy of the particle beam generated by the particle beam generation unit In a particle beam irradiation system equipped with an enlargement device,
The energy width expansion device is configured to form the SOBP in the depth direction over the entire irradiation region in the depth direction of the irradiation target without changing the parameters of the energy width expansion device. The control unit controls the scanning deflecting electromagnet so that the irradiation spot formed by the particle beam on the irradiation target is moved stepwise over the entire irradiation region in the lateral direction of the irradiation target. Particle beam irradiation system. A displacement phase detector for detecting the phase of displacement of the irradiation target,
The displacement phase detection unit outputs a gate signal that permits the irradiation target to irradiate the particle beam while the displacement of the irradiation target is in a predetermined phase, and the irradiation control unit outputs one of the gate signals. The scanning deflection electromagnet is controlled so that the irradiation spot is moved stepwise over the entire irradiation region in the lateral direction of the irradiation target while two gate signals are output. Item 4. The particle beam irradiation system according to Item 1.   3. The particle beam irradiation system according to claim 2, wherein the timing of starting the emission of the particle beam from the accelerator is synchronized with a determination result of whether or not the remaining available time of the accelerator is longer than the scheduled irradiation time in the gate.   3. The particle beam irradiation system according to claim 1, wherein the energy width expanding device is an element that expands an energy width so that the energy width has a distribution different in the lateral direction.

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