JP2015226672A - Particle beam treatment system and apparatus, and control method for particle beam treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle beam treatment system that can suppress variation in an irradiation beam position at low cost.SOLUTION: A particle beam treatment system comprises: an accelerator 10 for accelerating and extracting a charged particle beam; and a beam transport system 20 that comprises 6 or more four-pole electromagnets and transports the charged particle beam extracted from the accelerator to an irradiation target. The particle beam treatment system also comprises a controller 25 for controlling, for the charged particle beam in the beam transport system 20, magnetization amounts of the four-pole electromagnets in the beam transport system 20 so that two types of dispersion defined with respect to a direction perpendicular to a traveling direction of the charged particle beam is approximately 0 at a position of the irradiation target.

Description

  The present invention relates to a particle beam therapy system and apparatus, and a method for controlling a particle beam therapy system.

  As a background art of this technical field, there is WO2013 / 069379 A1 (Patent Document 1). This publication states that “the particle beam therapy system of the present invention is a particle beam therapy comprising an accelerator system for accelerating a charged particle beam and a beam transport system for transporting a charged particle beam emitted from the accelerator system to an irradiation position. In the system, the beam transport system includes at least one steering electromagnet and at least one beam position monitor corresponding to the steering electromagnet, and the beam position monitor corrects a periodically changing beam position in the steering electromagnet. ”(Paragraph 0008).

WO2013 / 069379 A1

  Patent Document 1 describes a method for suppressing fluctuations in irradiation beam position in a particle beam therapy system. In the particle beam therapy system described in Patent Document 1, periodic fluctuations in the irradiation beam position are measured by a beam position monitor installed in the beam transport system, and an excitation current of a steering electromagnet installed in the beam transport system is measured. By changing the irradiation beam position periodically so as to correct the fluctuation of the irradiation beam position, the fluctuation of the irradiation beam position is suppressed. However, the particle beam therapy system described in Patent Document 1 needs to use an expensive power source (hereinafter referred to as a pattern power source) having a function of periodically changing an output current as a power source of a steering electromagnet in a beam transport system. Therefore, there is a problem that the cost of the particle beam therapy system increases.

  Therefore, in view of the above points, the present invention provides a particle beam therapy system and apparatus, and a method for controlling the particle beam therapy system, which can reduce the irradiation beam position variation at low cost.

According to the first solution of the present invention,
A particle beam therapy system,
An accelerator that accelerates and extracts charged particle beams;
A beam transport system having a plurality of quadrupole electromagnets for adjusting the shape of the charged particle beam, and transporting the charged particle beam extracted from the accelerator to an irradiation target;
With respect to the charged particle beam in the beam transport system, perpendicular to the traveling direction of the charged particle beam, along the radial direction of the deflecting electromagnet of the accelerator or the plane direction including the orbiting beam or central orbit of the accelerator The plurality of first dispersions defined in the first direction, which is the first direction, derived from the accelerator, become zero or substantially zero at the position of the irradiation target. A control device for controlling the amount of excitation of each of the quadrupole electromagnets;
There is provided a particle beam therapy system comprising:

According to the second solution of the present invention,
A particle beam therapy device,
A beam transport system having a plurality of quadrupole electromagnets for adjusting the shape of the charged particle beam extracted from the accelerator, and transporting the charged particle beam extracted from the accelerator to an irradiation target;
With respect to the charged particle beam in the beam transport system, perpendicular to the traveling direction of the charged particle beam, along the radial direction of the deflecting electromagnet of the accelerator or the plane direction including the orbiting beam or central orbit of the accelerator The plurality of first dispersions defined in the first direction, which is the first direction, derived from the accelerator, become zero or substantially zero at the position of the irradiation target. A control device for controlling the amount of excitation of each of the quadrupole electromagnets;
There is provided a particle beam therapy system characterized by comprising:

According to the third solution of the present invention,
A method for controlling a particle beam therapy system, comprising:
The charged particle beam is accelerated and extracted by the accelerator,
By transporting the charged particle beam taken out from the accelerator to the irradiation target by a beam transport system having a plurality of quadrupole electromagnets for adjusting the shape of the charged particle beam,
The control device includes the radial direction of the deflecting electromagnet of the accelerator or the orbiting beam or center trajectory of the accelerator perpendicular to the traveling direction of the charged particle beam with respect to the charged particle beam in the beam transport system. In the beam transport system, two kinds of first dispersions derived from the accelerator, which are defined with respect to a first direction that is a direction along a plane direction, are 0 or substantially 0 at the position of the irradiation target. Controlling the amount of excitation of each of the plurality of quadrupole electromagnets,
A method for controlling a particle beam therapy system is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the particle beam treatment system which can suppress the fluctuation | variation of irradiation beam position at low cost can be provided.

Example of configuration diagram of particle beam therapy system according to Embodiment 1 The flowchart figure which shows the procedure which calculates the amount of quadrupole electromagnetism in Embodiment 1. Example of configuration diagram of particle beam therapy system according to Embodiment 1 Example of configuration diagram of particle beam therapy system according to embodiment 2 Example of configuration diagram of particle beam therapy system according to embodiment 2 The flowchart figure which shows the procedure which calculates the amount of quadrupole electromagnet excitation in Embodiment 2. Example of configuration diagram of particle beam therapy system according to Embodiment 3 The flowchart figure which shows the procedure which calculates the amount of quadrupole electromagnet excitation in Embodiment 3.

Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
In the present embodiment, an example of a particle beam therapy system capable of suppressing the variation of the irradiation beam position at low cost will be described.

FIG. 1 is an example of a particle beam therapy system according to this embodiment.

In the particle beam therapy system according to the present embodiment, a charged particle beam (hereinafter referred to as a beam) incident on the synchrotron 10 from the injector 1 is accelerated to a predetermined energy by the synchrotron 10 and is taken out. Irradiation target) 41 is irradiated.

  As the injector 1, for example, a linear accelerator (linac) that accelerates a beam generated by an ion source (not shown) to energy suitable for incidence on the synchrotron 10 (hereinafter referred to as incident energy) is used. The charged particle beam taken out from the injector 1 is incident on the synchrotron 10 via the low energy beam transport system 2 and the incident inflector 14.

  The synchrotron 10 includes an incident inflector 14, a deflection electromagnet 11, a quadrupole electromagnet 12, a high frequency acceleration cavity 13, and a takeout deflector 15.

  The deflection electromagnet 11 deflects a beam that circulates in the synchrotron 10 (hereinafter referred to as a circular beam trajectory) to form a predetermined circular trajectory (hereinafter referred to as a circular beam trajectory). The direction along the traveling direction of the circular beam is the traveling direction (the direction in which the beam travels is positive), the direction perpendicular to the traveling direction and along the radial direction of the deflection electromagnet 11 is the horizontal direction (the direction outside the synchrotron is positive), and travels A direction perpendicular to both the direction and the horizontal direction is referred to as a vertical direction (the front side in the drawing is positive). Here, deflecting the beam in the horizontal direction represents changing the traveling direction of the beam in a plane including the traveling direction and the horizontal direction, and deflecting the beam in the vertical direction refers to a plane including the traveling direction and the vertical direction. The direction in which the beam travels is changed. Further, the orbit beam trajectory on the design of the synchrotron 10 is called a central trajectory. The orbiting beam particles vibrate horizontally and vertically around the central trajectory, and this vibration is called betatron vibration. The frequency of betatron vibration per synchrotron is called tune. The quadrupole electromagnet 12 applies a converging or diverging force to the orbiting beam to keep the orbiting beam tuned to a stable value. The high-frequency acceleration cavity 13 applies a high-frequency voltage (hereinafter referred to as acceleration voltage) in the traveling direction to the circular beam to capture the circular beam in a predetermined phase in the traveling direction, and the excitation amount of the deflection electromagnet 11 and the frequency of the acceleration voltage ( Hereinafter, the orbiting beam is accelerated to a predetermined energy by gradually increasing the acceleration frequency). While the circular beam is accelerated, the excitation amount of the quadrupole electromagnet 12 is increased in proportion to the momentum of the circular beam, and the circular beam trajectory and the circular beam tune are kept constant. The take-out deflector 15 deflects the circular beam after completion of acceleration in the horizontal direction and takes it out of the synchrotron 15.

  A beam extracted from the synchrotron 15 (hereinafter referred to as an extracted beam) is irradiated to the affected area 41 after passing through the high energy beam transport system 20 and the irradiation field forming device 30. The coordinate system in the high energy beam transport system 20 and the irradiation field forming apparatus 30 is in accordance with the coordinate system of the synchrotron.

  In this example, the high energy beam transport system 20 is provided with one deflection electromagnet 21, six quadrupole electromagnets 22 a to 22 f, and a steering electromagnet 24. The deflecting electromagnet 21 deflects the extracted beam in a horizontal direction toward a treatment room (not shown) where the patient 40 is located, and the quadrupole electromagnets 22a to 22f apply a converging or diverging force to the extracted beam to move the affected part 41 in the traveling direction. The horizontal and vertical shape of the beam at a position (hereinafter referred to as an irradiation point) is adjusted. The quadrupole electromagnets 22 a to 22 f are connected to individual quadrupole electromagnet power supplies 23 a to 23 f, respectively, and the quadrupole electromagnet power supplies 23 a to 23 f are connected to the control device 25. Excitation currents of the quadrupole electromagnets 22a to 22f output from the quadrupole electromagnet power supplies 23a to 23f are individually controlled by the control device 25. Since the intensity of the quadrupole magnetic field generated by the quadrupole electromagnets 22a to 22f (hereinafter referred to as the excitation amount of the quadrupole electromagnets 22a to 22f) is proportional to the excitation current of the quadrupole electromagnets 22a to 22f, the excitation current of the quadrupole electromagnets 22a to 22f is Controlling is equivalent to controlling the excitation amount of the quadrupole electromagnets 22a to 22f. In addition, the number of the quadrupole electromagnets 22a to 22f and the quadrupole electromagnet power supplies 23a to 23f is not limited to six, but can be any more or less. The steering electromagnet 24 deflects the beam in the high energy beam transport system 20 horizontally and vertically, and adjusts the trajectory of the beam in the high energy beam transport system 20 and at the irradiation point. Although two steering electromagnets 24 are shown in FIG. 1, the number of steering electromagnets may be three or more. The number of steering electromagnets that deflect the beam in the horizontal direction and the number of steering electromagnets that deflect the beam in the vertical direction. May not be the same. Moreover, it is good also as a structure which does not install a steering electromagnet in the high energy beam transport system 20. FIG.

  The irradiation field forming device 30 shapes the beam from the high energy beam transport system 20 and forms an irradiation dose distribution (hereinafter referred to as an irradiation field) that matches the shape of the affected part 41. When the irradiation field forming device 30 forms the irradiation field, for example, a double scatterer method in which the beam is diffused by the scatterer and then shaped according to the shape of the affected area 41 using a collimator or the like, or the beam is scanned by an electromagnet Therefore, a scanning irradiation method of scanning in accordance with the shape of the affected part 41 is used.

  The measurement unit 50 measures horizontal dispersions ηfx0 and ηBx0 and their gradients ηfx0 ′ and ηBx0 ′ at the synchrotron 10 exit point, and Twiss parameters βx0, αx0, βy0, and αy0 at the synchrotron 10 exit point, and the control device 25 Output the measured value to. In addition, the measurement part 50 can be provided in an appropriate measurement position in addition to the illustrated position.

  After the extraction of the circular beam is completed, the synchrotron 10 changes the excitation amount of the deflection electromagnet 11, the excitation amount of the quadrupole electromagnet 12, and the acceleration frequency to the values at the time of beam incidence on the synchrotron 10, and the next beam incidence is performed. Prepare.

  The particle beam therapy system of the present embodiment repeats the beam acceleration, extraction, and irradiation described above until the beam irradiation previously determined by a treatment planning apparatus (not shown) is completed.

  In the present embodiment, a method for suppressing fluctuations in the irradiation beam position will be described. The irradiation beam position refers to the horizontal and vertical beam positions at the irradiation point. The fluctuation of the irradiation beam position represents a temporal change in the difference between the target irradiation beam position and the actual irradiation beam position. The range of variation in irradiation beam position allowed in the particle beam therapy system is determined by the accuracy required for the dose distribution and the method of forming the irradiation field. When the irradiation field is formed by the scanning irradiation method, the range of fluctuation of the irradiation beam position is preferably within ± 1 mm in both the horizontal and vertical directions. In the particle beam therapy system of the present embodiment, since the power source to which the steering electromagnet in the high energy beam transport system is connected is not the pattern power source, the control of the excitation amount of the steering electromagnet can sufficiently change the irradiation beam position. The case where it cannot be suppressed to is assumed.

  As a factor of fluctuation of the irradiation beam position in the particle beam therapy system of the present embodiment, there are fluctuations in the position and momentum of the extraction beam from the synchrotron 10. The deviation of the position of the extraction beam and the deviation of the momentum of the extraction beam are in a proportional relationship, and the proportionality coefficient is called a dispersion function or dispersion and is represented by the letter η. The horizontal dispersion ηx0 of the extracted beam at the exit point of the synchrotron 10 is expressed by the following equation 1 using the horizontal beam position shift Δx0 of the extracted beam at the same point and the momentum shift Δp / p normalized by the design value of the momentum. It is represented by In Equation 1, the subscript x represents a value in the horizontal direction, and the subscript 0 represents a value at the exit point of the synchrotron 10. Further, the change rate of the dispersion in the traveling direction, that is, the change amount or the change rate of the dispersion while the beam travels a unit length in the traveling direction is called a dispersion gradient, and is represented by the letter η ′. The vertical dispersion ηy0 of the extracted beam at the synchrotron 10 exit point is expressed by Equation 2 using the vertical beam position shift Δy0 at the synchrotron 10 exit point, similarly to the horizontal dispersion. The subscript y represents a value in the vertical direction. The components of the synchrotron 10 including the take-out deflector 15 are symmetrical in the vertical direction with respect to a plane including the central orbit (hereinafter referred to as a horizontal plane), and therefore the vertical disperse of the take-out beam at the exit point of the synchrotron 10 John ηy0 and its gradient ηy0 ′ are both 0.

  The dispersions ηx1, ηy1 and the gradients ηx1 ′, ηy1 ′ at the irradiation point are the dispersions ηx0, ηy0 and the gradients ηx0′ηy0 ′ at the synchrotron 10 exit point and the transport matrix Ax from the synchrotron 10 exit point to the irradiation point. , Ay is obtained by Equation 3. The subscript 1 represents a value at the irradiation point. The horizontal transport matrix Ax is a 3 × 3 matrix taking the form of Equation 4, and the value of each element in the matrix is determined from the device arrangement in the high energy beam transport system 20 and the excitation amount of the quadrupole electromagnets 22a to 22f. Desired. The vertical transport matrix Ay takes the form of Equation 5 because the deflecting electromagnet 21 in the high energy beam transport system 20 does not deflect the beam in the vertical direction.

以上より、照射地点におけるディスパージョンηｘ１、ηｙ１とその勾配ηｘ１’、ηｙ１’は、数式６により与えられる。

From the above, the dispersions ηx1 and ηy1 and the gradients ηx1 ′ and ηy1 ′ at the irradiation point are given by Expression 6.

  In the particle beam therapy system of this embodiment, in order to suppress fluctuations in the irradiation beam position, the following two types of dispersion are defined for the extracted beam from the synchrotron 10.

  The first dispersion is a dispersion (hereinafter referred to as an acceleration frequency derived) defined for a deviation in the position and momentum of the extracted beam from the synchrotron 10 caused by a deviation from the design value of the acceleration frequency of the synchrotron 10. Called dispersion). The dispersion derived from the acceleration frequency is represented by symbols ηfx and ηfy. The subscript f represents a value when there is a shift in the acceleration frequency. In addition, the gradient of the dispersion derived from the acceleration frequency is represented by symbols ηfx ′ and ηfy ′. The dispersions ηfx0, ηfy0 and their gradients ηfx0 ′, ηfy0 ′ derived from the acceleration frequency at the exit point of the synchrotron 10 are, for example, in the high energy beam transport system 20 while changing the acceleration frequency of the high-frequency acceleration cavity 13 of the synchrotron 10, for example. Can be obtained by measuring the beam position by the measurement unit 50. For the measurement of the beam position in the high energy beam transport system 20, for example, a beam profile monitor that measures the distribution of beam particles in the horizontal and vertical directions can be used as the measurement unit 50. In addition, the position of the measurement part 50 can be provided in a suitable position other than illustration. Further, the dispersions ηfx0 and ηfy0 derived from the acceleration frequency and the gradients ηfx0 ′ and ηfy0 ′ may be obtained by calculation from the calculation result of the extracted beam trajectory. Since the dispersion derived from the acceleration frequency follows conversion by the transport matrix, the dispersions ηfx1 and ηfy1 and the gradients ηfx1 ′ and ηfy1 ′ derived from the acceleration frequency at the irradiation point are expressed by Expression 7.

  The second dispersion is a dispersion (hereinafter referred to as a deflection magnetic field) defined for a deviation in the position and momentum of the extracted beam from the synchrotron 10 caused by a deviation from the design value of the excitation amount of the deflection electromagnet 11. Called dispersion). The dispersion derived from the deflection magnetic field is represented by symbols ηBx and ηBy. The subscript B represents a value when there is a deviation in the excitation amount of the deflection electromagnet 11. Further, the gradient of the dispersion derived from the deflection magnetic field is represented by symbols ηBx ′ and ηBy ′. The horizontal dispersion ηBx0 derived from the deflection magnetic field at the synchrotron 10 exit point and the gradient ηBx0 ′ thereof are generally different from the dispersion ηfx0 derived from the acceleration frequency at the synchrotron 10 exit point and the gradient ηfx0 ′. The vertical dispersion ηBy0 and the gradient ηBy0 ′ derived from the deflection magnetic field at the exit point of the synchrotron 10 are 0 as in the case of the acceleration frequency. The dispersion ηBy0 and the gradient ηBy0 ′ derived from the deflection magnetic field at the exit point of the synchrotron 10 are measured by the measuring unit 50 while the beam position in the high energy beam transport system 20 is changed by changing the excitation amount of the deflection magnet 11 of the synchrotron 10, for example. It can be obtained by measuring. Further, the dispersion ηBy0 derived from the deflection magnetic field at the exit point of the synchrotron 10 and its gradient ηBy0 ′ may be obtained by calculation from the calculation result of the extracted beam trajectory. Similarly to the dispersion derived from the acceleration frequency and the gradient thereof, the dispersions ηBx1 and ηBy1 derived from the deflection magnetic field at the irradiation point and the gradients ηBx1 ′ and ηBy1 ′ are expressed by Expression 8.

  In the particle beam therapy system of the present embodiment, the control device 25 uses the excitation amount of the quadrupole electromagnets 22a to 22f installed in the high energy beam transport system 20 as a horizontal dispersion ηfx1 derived from the acceleration frequency at the irradiation point and the horizontal derived from the deflection magnetic field. Control is performed so that the dispersion ηBx1 is both zero. Specifically, the excitation amounts of the quadrupole electromagnets 22a to 22f are controlled so that each component of the horizontal transport matrix from the exit point of the synchrotron 10 to the irradiation point satisfies the relationship of Equation 9. Since there are two types of constraints on the dispersion shown in Equation 9, in order for the horizontal transport matrix Ax to satisfy Equation 9, at least two of the quadrupole electromagnets 22a to 22f in the high energy beam transport system 20 are required. It is necessary to control the excitation amount independently.

  Further, in the particle beam therapy system, it is necessary to control the horizontal size sx1 and the change rate sx1 'of the beam at the irradiation point, and the vertical size sy1 and the change rate sy1' to appropriate values. The beam size represents the width of a region where beam particles exist in a plane perpendicular to the traveling direction. The rate of change of the beam size represents the degree of change of the beam size with respect to the change of the position in the traveling direction. Since there are two types of constraint conditions related to the beam size in the horizontal direction (sx1, sx1 ′) and two types in the vertical direction (sy1, sy1 ′), the beam sizes sx1, sy1 and the rate of change sx1 at the irradiation point. In order to control ', sy1' to an appropriate value, it is necessary to independently control the excitation amounts of at least four of the quadrupole electromagnets 22a to 22f in the high energy beam transport system 20.

  The control device 25 has appropriate values for the beam sizes sx1 and sy1 and the rates of change sx1 ′ and sy1 ′ at the irradiation point, and the horizontal dispersion ηfx1 derived from the acceleration frequency and the horizontal dispersion ηBx1 derived from the deflection magnetic field at the irradiation point. The excitation amounts of the quadrupole electromagnets 22a to 22f in the high energy beam transport system 20 are controlled so that both are zero. Since the control device 25 independently controls the excitation amounts of the six quadrupole electromagnets 22a to 22f, the quadrupole electromagnets 22a to 22f are set so that the horizontal transport matrix Ax simultaneously satisfies the constraint condition regarding the dispersion and the constraint condition regarding the beam size. The amount of excitation can be set.

  The amount of excitation of the quadrupole electromagnets 22a to 22f, in which the horizontal transport matrix Ax simultaneously satisfies the constraints regarding the dispersion and the beam size, is determined from the synchrotron 10 model created from the equipment arrangement of the high energy beam transport system. The control device 25 obtains by calculation from the Twiss parameter of the extracted beam, the horizontal dispersion ηfx0 derived from the acceleration frequency and its gradient ηfx0 ′, and the horizontal dispersion ηBx0 derived from the deflection magnetic field and the gradient ηBx0 ′.

  The Twiss parameter is a parameter used to express the distribution of beam particles in the phase space, and the horizontal Twiss parameters βx and αx are mathematical expressions using the horizontal beam size sx and the horizontal emittance εx. Represented by 10. In Expression 10, s represents a position in the traveling direction. Similarly, the Twiss parameters βy and αy in the vertical direction are expressed by Equation 11 using the vertical beam size sy and the vertical emittance εy. The Twiss parameters βx1, αx1, βy1, and αy1 at the irradiation point are mathematical expressions using the Twis parameters βx0, αx0, βy0, αy0 at the synchrotron 10 exit point and the components of the transport matrix Ax and Ay from the synchrotron 10 exit to the irradiation point. 12. In order to control the beam size sx1, sy1 and the rate of change sx1 ′, sy1 ′ at the irradiation point to appropriate values, high energy beam transport is performed so that the Twiss parameters βx1, αx1, βy1, αy1 at the irradiation point become predetermined values. The amount of excitation of the quadrupole electromagnets 22a to 22f in the system 20 may be controlled.

  A method in which the control device 25 obtains excitation currents of the quadrupole electromagnets 22a to 22f such that the horizontal dispersions ηfx1 and ηBx1 at the irradiation point are both 0 and the Twis parameters βx1, αx1, βy1, and αy1 at the irradiation point are predetermined values. An example will be described with reference to FIG.

  FIG. 2 is a flowchart showing a procedure in which the control device 25 obtains the excitation amounts of the quadrupole electromagnets 22a to 22f by an iterative method. First, the control device 25 reads the horizontal dispersions ηfx0 and ηBx0 and the gradients ηfx0 ′ and ηBx0 ′ at the synchrotron 10 exit point by the measuring unit 50 (S101), and then the Twiss parameter βx0 at the synchrotron 10 exit point. , Αx0, βy0, αy0 are read (S103). The control device 25 sets initial values (for example, design values of the excitation amounts of the quadrupole electromagnets 22a to 22f) to the excitation amounts K1 to K6 for calculation of the quadrupole electromagnets 22a to 22f (S105), and calculates the quadrupole electromagnets 22a to 22f. As shown in Equation 4 and Equation 5, the transport matrices Ax and Ay from the synchrotron 10 exit point to the irradiation point are calculated (S107). The control device 25 calculates the horizontal dispersions ηfx1 and ηBx1 at the irradiation point from the horizontal dispersions ηfx0 and ηBx0 and the gradients ηfx0 ′ and ηBx0 ′ and the transport matrices Ax and Ay at the exit point of the synchrotron 10 according to Equations 7 and 8. Further, the Twiss parameters βx1, αx1, βy1, and αy1 at the irradiation point are calculated from the Twiss parameters βx0, αx0, βy0, αy0 and the transport matrices Ax, Ay at the exit point of the synchrotron 10 according to Equation 12 (S107). When the target value of the Twiss parameter at the irradiation point is βx1T, αx1T, βy1T, αy1T, the objective function F in the iterative calculation is defined by Equation 13, for example.

  The objective function F shown in Expression 13 is a function that becomes 0 when the horizontal dispersions ηfx1 and ηBx1 at the irradiation point are both 0 and the Twis parameters βx1, αx1, βy1, and αy1 at the irradiation point coincide with the target values. The control device 25 calculates the objective function F from the calculation results of the horizontal dispersions ηfx1, ηBx1 and the Twiss parameters βx1, αx1, βy1, and αy1 at the irradiation point (S109), and whether or not the objective function F is equal to or less than a preset threshold value. Is determined (S111). When the objective function is larger than the threshold value, that is, when the determination result is No, the control device changes the amount of quadrupole electromagnet excitation for calculation (S113), and again from the calculation of the transport matrices Ax and Ay to the determination of the objective function F. Processing (S107 to S111) is performed. When the objective function F is equal to or less than the threshold value in step S111, that is, the determination result is Yes, the control device 25 sets the current calculation quadrupole electromagnet excitation amount as the calculation result of the quadrupole electromagnets 22a to 22f, and the quadrupole electromagnets 22a to 22f. Calculation of the excitation amount of 22f is completed (S115). The control device 25 controls the excitation amounts of the quadrupole electromagnets 22a to 22f so as to coincide with the calculated excitation amounts of the quadrupole electromagnets 22a to 22f. Note that the control device 25 may store the value of the calculation result in an appropriate memory, and the memory may use the value for read control.

  In the present embodiment, the control device 25 calculates the excitation amounts of the quadrupole electromagnets 22a to 22f that satisfy the constraint conditions. However, the controller of the particle beam therapy system separately calculates the excitation amounts of the quadrupole electromagnets 22a to 22f, and the quadrupole electromagnet 22a. The calculation result of the ˜22f excitation amount may be input to the control device 25. In this case, the control device 25 controls the excitation amounts of the quadrupole electromagnets 22a to 22f so as to match the input excitation amounts of the quadrupole electromagnets 22a to 22f. In the particle beam therapy system of the present embodiment, the control device 25 controls the excitation amount of the quadrupole electromagnets 22a to 22f so that the horizontal transport matrix satisfies Equation 9, so that the horizontal dispersion ηfx1 derived from the acceleration frequency at the irradiation point And the horizontal dispersion ηBx1 derived from the deflection magnetic field are both zero. The vertical dispersions ηfy1 and ηBy1 at the irradiation point are 0 regardless of the excitation amounts of the quadrupole electromagnets 22a to 22f as shown in Equations 7 and 8.

  When the acceleration frequency of the synchrotron 10 varies during beam irradiation in the particle beam therapy system of the present embodiment, the horizontal position and momentum of the extracted beam vary, but the horizontal and vertical dispersions ηfx1, derived from the acceleration frequency at the irradiation point, Since ηfy1 is 0, the irradiation beam position is kept constant regardless of the shift of the acceleration frequency. Similarly, even when the excitation amount of the deflecting electromagnet 11 of the synchrotron 10 fluctuates during beam irradiation, the horizontal and vertical dispersions ηBx1 and ηBy1 derived from the deflection magnetic field at the irradiation beam position are 0, so that the irradiation beam position is The deflection electromagnet 11 is kept constant regardless of the deviation of the excitation amount.

  As described above, in the particle beam therapy system according to the present embodiment, two types are applied at the irradiation point with respect to the horizontal dispersion derived from the acceleration frequency and the horizontal dispersion derived from the deflection magnetic field defined for the extracted beam from the synchrotron 10. Since the control device 25 controls the amount of excitation of the quadrupole electromagnets 22a to 22f in the high energy beam transport system 20 so that both of the dispersions of the power distribution are zero, the power source of the steering electromagnet 24 in the high energy beam transport system 20 is expensive. It is possible to suppress fluctuations in the irradiation beam position without using a pattern power source.

  The particle beam therapy system according to the present embodiment has a configuration in which six quadrupole electromagnets 22a to 22f are installed in the high energy beam transport system 20, but there are six quadrupole electromagnets installed in the high energy beam transport system 20. It doesn't matter if more. When more than six quadrupole electromagnets are installed in the high energy beam transport system 20, the high energy beam transport system 20 passes through the high energy beam transport system 20 in addition to satisfying the restrictions imposed by the dispersion and the beam size. The horizontal and vertical sizes of the beam to be controlled can be controlled to be equal to or less than the inner diameter of a vacuum duct (not shown) constituting the high energy beam transport system 20 to suppress beam loss in the high energy beam transport system 20. Further, some or all of the quadrupole electromagnets 22 a to 22 f may be installed on the upstream side (side closer to the synchrotron 10) than the deflection electromagnet 21.

  In the particle beam therapy system according to the present embodiment, the high energy beam transport system 20 includes one deflecting electromagnet 21, but the high energy beam transport system 20 may include two or more deflecting electromagnets. Further, the high energy beam transport system 20 may be configured not to include one deflection electromagnet. In this embodiment, fluctuations in the irradiation beam position can be suppressed regardless of the number of deflection electromagnets in the high energy beam transport system 20.

  In the particle beam therapy system of the present embodiment, the horizontal dispersion ηfx1 derived from the acceleration frequency at the irradiation point and the horizontal dispersion ηBx1 derived from the deflection magnetic field are corrected to 0, but the corrected dispersion at the irradiation point is exactly 0. It doesn't have to be. Specifically, if the absolute value of the horizontal dispersion ηfx1 derived from the acceleration frequency at the irradiation point and the absolute value of the horizontal dispersion ηBx1 derived from the deflection magnetic field are sufficiently small, the effect of the present embodiment that suppresses the variation of the irradiation beam position. Can be obtained.

  The absolute value of the horizontal dispersion ηfx1 derived from the acceleration frequency at the irradiation point is sufficiently small (substantially 0) that the product of the horizontal dispersion ηfx1 derived from the acceleration frequency at the irradiation point and the momentum deviation derived from the acceleration frequency is a particle beam treatment. It means that it is within the limit of fluctuation range of irradiation beam position required by the system. For example, if the momentum deviation derived from the acceleration frequency is ± 0.1% over the entire width and the variation width of the irradiation beam position is within ± 1 mm, the absolute value of the horizontal dispersion ηfx1 derived from the acceleration frequency is sufficiently small. Ηfx1 is from −1 m to 1 m. Similarly, the absolute value of the horizontal dispersion ηBx1 derived from the deflection magnetic field at the irradiation point is sufficiently small that the product of the horizontal dispersion ηBx1 derived from the deflection magnetic field at the irradiation point and the momentum deviation derived from the deflection magnetic field is the particle beam therapy system. This means that it is within the limit of the fluctuation range of the irradiation beam position to be obtained.

  In the particle beam therapy system according to the present embodiment, the horizontal dispersion gradient ηfx1 ′ derived from the acceleration frequency at the irradiation point and the horizontal dispersion gradient ηBx1 ′ derived from the deflection magnetic field do not become zero, but the dispersion gradient is at the irradiation beam position. Since there is no influence, the fact that the horizontal dispersion gradients ηfx1 ′ and ηBx1 ′ are not 0 is not a problem in suppressing fluctuation of the irradiation beam position.

  In the particle beam therapy system of the present embodiment, the beam is accelerated to the energy suitable for irradiation by the synchrotron 10, but as shown in FIG. 3, the beam may be accelerated to the energy suitable for irradiation by the cyclotron. . The particle beam therapy system shown in FIG. 3 has the same configuration as the particle beam therapy system shown in FIG. 1 except that the beam is accelerated to an energy suitable for irradiation by a cyclotron 70 instead of the injector 1 and the synchrotron 10. Different. In the particle beam therapy system using the cyclotron 70, for example, a first dispersion is defined for a beam position and momentum shift caused by a magnetic field shift generated between magnetic poles constituting the cyclotron 70, and the cyclotron 70 is configured. By defining the second dispersion against the deviation of the beam position and the momentum caused by the deviation of the frequency of the high frequency voltage applied to the dee electrode, the fluctuation of the irradiation beam position is suppressed in the same manner as when using the synchrotron 10. it can.

(Embodiment 2)
In the present embodiment, an example of a particle beam therapy system that can suppress fluctuations in irradiation beam position even when the beam is deflected in the vertical direction in a low-cost and high-energy beam transport system will be described.

FIG. 4 is an example of a particle beam therapy system according to the present embodiment.
The particle beam therapy system of the present embodiment has the same configuration as that of the particle beam therapy system of the first embodiment, but the configuration of the high energy beam transport system 20 and the direction of irradiating the affected part 41 with the beam are different. FIG. 4 is a schematic view of the particle beam therapy system according to the present embodiment as viewed from the vertical positive direction of the synchrotron 10. FIG. 5 is a schematic view of the particle beam therapy system according to the present embodiment as viewed from the horizontal positive direction in the straight line portion where the take-out deflector 15 of the synchrotron 10 is installed.

  In this example, the high energy beam transport system 20 is provided with a deflection electromagnet 21, three deflection electromagnets 51a to 51c, seven quadrupole electromagnets 52a to 52g, and a steering electromagnet 24. As in the first embodiment, the deflecting electromagnet 21 deflects the extracted beam from the synchrotron 10 toward the treatment room in the horizontal direction. The deflection electromagnets 51a to 51c deflect the beam a plurality of times in the vertical direction, and enable the irradiation of the affected part 41 from the vertical direction. The quadrupole electromagnets 52a to 52g adjust the shape of the beam at the irradiation point as in the first embodiment. The quadrupole electromagnets 52 a to 52 g are connected to individual quadrupole electromagnet power supplies 53 a to 53 g, respectively, and the quadrupole electromagnet power supplies 53 a to 53 g are connected to the control device 25. Excitation currents of the quadrupole electromagnets 52a to 52g output from the quadrupole electromagnet power supplies 53a to 53g are individually controlled by the control device 25. As in the first embodiment, the steering electromagnet 24 adjusts the beam trajectory in the high energy beam transport system 20 and at the irradiation point.

  In the present embodiment, a method for suppressing fluctuations in the irradiation beam position will be described. In the present embodiment, since the beam is deflected in the vertical direction in the high energy beam transport system 20, the vertical dispersion at the irradiation point is not always zero. The horizontal dispersion derived from the acceleration frequency at the exit point of the synchrotron 10 is ηfx0, the gradient is ηfx0 ', the horizontal dispersion derived from the deflection magnetic field is ηBx0, and the gradient is ηBx0'. The vertical dispersions ηfy0 and ηBy0 and the gradients ηfy0 'and ηBy0' at the exit point of the synchrotron 10 are 0 as in the first embodiment. Since the high energy beam transport system 20 of the present embodiment also deflects the beam in the vertical direction, transport matrices Ax and Ay from the synchrotron 10 exit point to the irradiation point are expressed in the form of Equation 14. Since the beam is deflected in the vertical direction, the first row and third column component a13 and the second row and third column component a23 of the transport matrix Ay in the vertical direction are not 0 as in the first embodiment. The dispersions ηfx1, ηfy1, ηBx1, and ηBy1 at the irradiation point are the same as in the first embodiment, the dispersions ηfx0, ηfy0, ηBx0, ηBy0 and their gradients ηfx0 ′, ηfy0 ′, ηBx0 ′, and ηBy0 ′ at the exit point of the synchrotron 10 Since it is given by the product of the matrices Ax and Ay, the dispersions ηfx1, ηfy1, ηBx1, and ηBy1 at the irradiation point are expressed by Equation 15.

  In the particle beam therapy system of this embodiment, the control device 25 deflects the excitation amounts of the quadrupole electromagnets 52a to 52g installed in the high energy beam transport system 20 with horizontal and vertical dispersions ηfx1, ηfy1 derived from the acceleration frequency at the irradiation point. Control is performed so that the horizontal and vertical dispersions ηBx1 and ηBy1 derived from the magnetic field are all zero. Specifically, the excitation amounts of the quadrupole electromagnets 52a to 52h are controlled so that the horizontal and vertical transport matrices Ax and Ay from the exit point of the synchrotron 10 to the irradiation point satisfy the relationship of Expression 16. Since there are three types of constraints regarding the dispersion shown in Equation 16, in order for the horizontal and vertical transport matrices Ax and Ay to satisfy Equation 16, among the quadrupole electromagnets 52a to 52g in the high energy beam transport system 20 It is necessary to control at least three excitation amounts independently.

  As in the first embodiment, in this embodiment, in order to control the beam sizes sx1 and sy1 and the rate of change sx1 ′ and sy1 ′ at the irradiation point to appropriate values, at least four of the four-pole electromagnets 52a to 52g are excited. The amount needs to be controlled independently. In order to control the beam sizes sx1 and sy1 and their change rates sx1 ′ and sy1 ′ at the irradiation point to appropriate values, the Twiss parameters βx1, αx1, βy1, and αy1 at the irradiation point are set to predetermined values as in the first embodiment. Just control. In the control device 25, the Twiss parameters βx1, αx1, βy1, and αy1 at the irradiation point become predetermined values, and the horizontal and vertical dispersions ηfx1 and ηfy1 derived from the acceleration frequency at the irradiation point and the horizontal and vertical dispersions ηBx1 derived from the deflection magnetic field. , .Eta.By1 is controlled so that the excitation amounts of the quadrupole electromagnets 52a to 52g in the high energy beam transport system 20 are all zero. Since the control device 25 independently controls the excitation amounts of the seven quadrupole electromagnets 52a to 52g, the quadrupole electromagnets 52a to 52g are configured so that the transport matrices Ax and Ay simultaneously satisfy the constraint condition regarding the dispersion and the constraint condition regarding the beam size. The amount of excitation can be controlled.

  The amount of excitation of the quadrupole electromagnets 52a to 52g so that the transport matrices Ax and Ay simultaneously satisfy the constraint condition regarding the dispersion and the constraint condition regarding the beam size is the Twiss parameter βx0 of the extracted beam from the synchrotron 10 as in the first embodiment. The control device 25 obtains by calculation from αx0, βy0, αy0, the horizontal dispersion ηfx0 derived from the acceleration frequency and its gradient ηfx0 ′, and the horizontal dispersion ηBx0 derived from the deflection magnetic field and the gradient ηBx0 ′. Also, the Twist parameters βx0, αx0, βy0, αy0, the horizontal dispersion ηfx0 derived from the acceleration frequency and the gradient ηfx0 ′ thereof, which are necessary for calculating the excitation amounts of the quadrupole electromagnets 52a to 52g, The horizontal dispersion ηBx0 and the gradient ηBx0 ′ derived from the deflection magnetic field can be measured or calculated in the same manner as in the first embodiment.

  FIG. 6 shows quadrupole electromagnets 52a to 52g in which the horizontal and vertical dispersions ηfx1, ηfy1, ηBx1, and ηBy1 at the irradiation point are all 0, and the Twiss parameters βx1, αx1, βy1, and αy1 at the irradiation point are predetermined values. The flowchart about the procedure in which the control apparatus 25 calculates | requires the exciting current of this by an iterative method is shown. The procedure by which the control device 25 calculates the excitation amounts of the quadrupole electromagnets 52a to 52g is the same as that in the first embodiment, but the dispersion reading (S201) and the Twiss parameter reading (S203) (corresponding to S101 and S103 in the first embodiment). After that, in this embodiment, since the four quadrupole electromagnets installed in the high energy beam transport system 20 are independently controlled, the amount of excitation for calculation of the quadrupole electromagnets 52a to 52g is equivalent to seven from K1 to K7. (See S205, S213, and S215). In the present embodiment, since the vertical dispersions ηfx1 and ηBy1 at the irradiation point vary depending on the amount of excitation of the quadrupole electromagnets 52a to 52g, the objective function F of the repeated calculation needs to be in the form of, for example, Equation 17 (S207, S209). , S211). Since the vertical dispersion ηBy1 derived from the deflection magnetic field at the irradiation point coincides with the dispersion ηfy1 derived from the acceleration frequency at the irradiation point as shown in Formula 15, in Formula 17, one of the vertical dispersions ηfy1 and ηBy1 at the irradiation point is calculated. Only ηfy1 is used in the calculation of the objective function F (note that ηBy1 may be used instead of ηfy1).

  When the acceleration frequency of the synchrotron 10 varies during beam irradiation in the particle beam therapy system of the present embodiment, the horizontal position and momentum of the extracted beam vary, but the horizontal and vertical dispersions ηfx1, derived from the acceleration frequency at the irradiation point, Since ηfy1 is 0, the irradiation beam position is kept constant regardless of the shift of the acceleration frequency. Similarly, even when the excitation amount of the deflecting electromagnet 11 of the synchrotron 10 fluctuates during beam irradiation, the horizontal and vertical dispersions ηBx1 and ηBy1 derived from the deflection magnetic field at the irradiation beam position are 0, so that the irradiation beam position is The deflection electromagnet 11 is kept constant regardless of the deviation of the excitation amount.

  As described above, in the particle beam therapy system of the present embodiment, irradiation is performed on the horizontal and vertical dispersions derived from the acceleration frequency defined for the extracted beam from the synchrotron 10 and the horizontal and vertical dispersions derived from the deflection magnetic field. Since the controller 25 controls the amount of excitation of the quadrupole electromagnets 52a to 52g in the high energy beam transport system 20 so that the values of these dispersions are all zero at the point, the steering electromagnet 24 in the high energy beam transport system 20 is controlled. The fluctuation of the irradiation beam position can be suppressed without using an expensive pattern power source for the power source.

  The particle beam therapy system according to the present embodiment is configured such that seven quadrupole electromagnets 52a to 52g are installed in the high energy beam transport system 20, but seven quadrupole electromagnets are installed in the high energy beam transport system 20. It doesn't matter if more. When more than seven quadrupole electromagnets are installed in the high energy beam transport system 20, the beam loss in the high energy beam transport system 20 can be suppressed as in the first embodiment. Further, the quadrupole electromagnets 52 a to 52 g may be installed in any straight part in the high energy beam transport system 20.

  In the particle beam therapy system according to the present embodiment, as in the first embodiment, two or more deflecting electromagnets for deflecting the beam included in the high energy beam transport system 20 in the horizontal direction may be used, and the high energy beam transport system 20 generates the beam. It is good also as a structure which does not have one deflection | deviation electromagnet which deflects in a horizontal direction. Similarly, in the present embodiment, any number of deflecting electromagnets for deflecting the beam provided in the high energy beam transport system in the vertical direction may be used as long as the number is one or more.

  In the particle beam therapy system of this embodiment, the horizontal and vertical dispersions ηfx1 and ηfy1 derived from the acceleration frequency at the irradiation point and the horizontal and vertical dispersions ηBx1 and ηBy1 derived from the deflection magnetic field are accurately corrected to 0, as in the first embodiment. It doesn't have to be.

(Embodiment 3)
In the present embodiment, an example of a particle beam treatment system that can suppress fluctuations in the irradiation beam position even when the high-energy beam transport system includes a rotating gantry will be described.

FIG. 7 is an example of a particle beam therapy system according to the present embodiment.

The particle beam therapy system according to the present embodiment has the same configuration as that of the particle beam therapy system according to the first embodiment, but differs from the particle beam therapy system according to the first embodiment in that the high energy beam transport system 20 includes a rotating gantry 60. ing.

  The high energy beam transport system 20 includes a deflection electromagnet 21, six quadrupole electromagnets 62 a to 62 f, a steering electromagnet 24, and a rotating gantry 60 that can rotate around the patient 40 around the rotating shaft 64. The rotating gantry 60 includes a plurality of deflection electromagnets and a plurality of quadrupole electromagnets. In the high energy beam transport system 20, a starting point of a portion that can rotate around the rotation shaft 64 is defined as an inlet of the rotating gantry 60 (hereinafter referred to as a rotating gantry inlet 65). The deflection electromagnet 21, the quadrupole electromagnets 62 a to 62 f, and the steering electromagnet 24 are installed between the synchrotron 10 outlet and the rotating gantry inlet 65 of the high energy beam transport system 20. As in the first embodiment, the deflecting electromagnet 21 deflects the extracted beam from the synchrotron 10 toward the treatment room in the horizontal direction. The quadrupole electromagnets 62a to 62h adjust the shape of the beam at the rotary gantry entrance 65 by applying a converging or diverging force to the beam. The quadrupole electromagnets 62 a to 62 f are connected to individual quadrupole electromagnet power supplies 63 a to 63 f, respectively, and the quadrupole electromagnet power supplies 63 a to 63 f are connected to the control device 25. Excitation currents of the quadrupole electromagnets 62a to 62f output from the quadrupole electromagnet power supplies 63a to 63f are individually controlled by the control device 25. As in the first embodiment, the steering electromagnet 24 adjusts the beam trajectory in the high energy beam transport system 20 and at the irradiation point. The rotating gantry 60 changes the angle formed by the irradiation nozzle and the treatment room vertical direction (hereinafter referred to as the gantry rotation angle) by rotating around the rotating shaft 64, and beams from a plurality of different directions with respect to the affected part 41. Irradiation is possible. The quadrupole electromagnet in the rotating gantry 60 adjusts the shape of the beam at the irradiation point as in the first embodiment.

  In the present embodiment, a method for suppressing fluctuations in the irradiation beam position will be described. First, in this embodiment, since the coordinate system in the rotating gantry 60 rotates in accordance with the rotation of the rotating gantry 60, the coordinate system is switched with the rotating gantry inlet 65 as a boundary. Since two types of coordinate systems overlap at the rotating gantry entrance 65, for parameters such as dispersion, the value in the non-rotating coordinate system is referred to as the “value on the rotating gantry inlet 65 fixed side”, and the value in the rotating coordinate system is “ This value will be referred to as “value on the rotating gantry inlet 65 rotation side”. It is assumed that a horizontal transport matrix Hx from the exit point of the synchrotron 10 to the rotary gantry inlet 65 is expressed in the form of Equation 18. At this time, the horizontal dispersion ηfx2 and gradient ηfx2 ′ derived from the acceleration frequency on the fixed side of the rotating gantry inlet 65 and the horizontal dispersion ηBx2 derived from the deflection magnetic field and the gradient ηBx2 ′ are expressed by Equation 20 as in the first embodiment. The The subscript 2 of the dispersion represents a value on the fixed side of the rotating gantry inlet 65. In the present embodiment, since the deflector 15 for taking out the synchrotron 10 and the deflecting electromagnet 21 in the high energy beam transport system 20 change the beam in the horizontal direction, the vertical dispersions ηfy2, ηBy2 on the fixed side of the rotary gantry inlet 65 are used. And their gradients ηfy2 ′ and ηBy2 ′ are 0 as in the first embodiment. The vertical transport matrix Hx from the synchrotron 10 exit point to the rotating gantry entrance 65 is expressed in the form of Equation 19 as in the first embodiment.

  In the particle beam therapy system of the present embodiment, the control device 25 uses the excitation amount of the quadrupole electromagnets 62a to 62f installed in the high energy beam transport system 20 as the gradient ηfx2 ′ of the horizontal dispersion derived from the acceleration frequency on the rotating gantry entrance fixed side. And the gradient ηBx2 ′ of the horizontal dispersion derived from the deflection magnetic field are controlled to be zero. Specifically, the amount of excitation of the quadrupole electromagnets 62a to 62f is controlled so that each component of the horizontal transport matrix Hx from the exit point of the synchrotron 10 to the rotary gantry inlet 65 satisfies the relationship of Equation 21. Since there are two types of constraints regarding the dispersion shown in Equation 21, in order for the horizontal transport matrix Hx to satisfy Equation 14, at least two of the quadrupole electromagnets 62a to 62f in the high energy beam transport system 20 are required. It is necessary to control the excitation amount independently.

  Furthermore, in the particle beam therapy system of this embodiment, in order to control the beam sizes sx1 and sy1 at the irradiation point and the change rates sx1 ′ and sy1 ′ to appropriate values, the beam size sx2 on the fixed side of the rotating gantry entrance 65 is used. , Sy2 and their change rates sx2 ′, sy2 ′ need to be controlled to appropriate values. For this purpose, the Twiss parameters βx2, αx2, βy2, and αy2 on the rotating gantry inlet 65 fixed side may be set to predetermined values determined from the design of the rotating gantry. In order to control the Twist parameters βx2, αx2, βy2, and αy2 on the fixed side of the rotating gantry inlet 65 to predetermined values, as in the first embodiment, at least four of the quadrupole electromagnets 62a to 62f are independently controlled. There is a need to. In the control device 25, the Twiss parameters βx2, αx2, βy2, and αy2 on the fixed side of the rotating gantry inlet 65 become predetermined values, and the gradient ηfx2 ′ of the horizontal dispersion derived from the acceleration frequency on the fixed side of the rotating gantry inlet 65 and the deflection magnetic field The excitation amounts of the quadrupole electromagnets 62a to 62f in the high-energy beam transport system 20 are controlled so that the horizontal dispersion gradient ηBx2 ′ of both becomes zero. Since the control device 25 independently controls the excitation amounts of the six quadrupole electromagnets 62a to 62f, the excitation of the quadrupole electromagnets 62a to 62f is performed so that the transport matrices Ax and Ay simultaneously satisfy the constraint condition regarding the dispersion and the constraint condition regarding the beam size. The amount can be controlled.

  Excitation amounts of the quadrupole electromagnets 62a to 62f that simultaneously satisfy the constraint condition regarding the dispersion and the constraint condition regarding the beam size are the Twist parameters βx0 of the extracted beam from the synchrotron 10 as in the first embodiment. The control device 25 obtains by calculation from αx0, βy0, αy0, the horizontal dispersion ηfx0 derived from the acceleration frequency and its gradient ηfx0 ′, and the horizontal dispersion ηBx0 derived from the deflection magnetic field and the gradient ηBx0 ′. Also, the Twist parameters βx0, αx0, βy0, αy0, the horizontal dispersion ηfx0 derived from the acceleration frequency and the gradient ηfx0 ′ thereof, which are necessary for calculating the excitation amounts of the quadrupole electromagnets 52a to 52h, The horizontal dispersion ηBx0 and the gradient ηBx0 ′ derived from the deflection magnetic field can be measured or calculated in the same manner as in the first embodiment.

  FIG. 8 shows quadrupoles such that the horizontal dispersion gradient ηfx2′ηBx2 ′ on the rotating gantry inlet fixed side 65 becomes 0, and the Twiss parameters βx2, αx2, βy2, and αy2 on the rotating gantry inlet fixed side 65 have predetermined values. The flowchart figure about the procedure in which the control apparatus 25 calculates | requires the exciting current of the electromagnets 62a-62f by an iterative method is shown. The procedure by which the control device 25 calculates the excitation amounts of the quadrupole electromagnets 62a to 62f is the same as that in the first embodiment, but after steps S301 to S307 (corresponding to steps S101 to S107 in the first embodiment), the rotation is performed in this embodiment. In order to correct the horizontal dispersion gradients ηfx2 ′ and ηBx2 ′ on the fixed side of the gantry inlet 65 to 0, the objective function F of the iterative calculation needs to be in the form of, for example, Equation 22 (S309). Βx2T, αx2T, βy2T, and αy2T in Equation 22 are target values of the Twiss parameters βx2, αx2, βy2, and αy2 on the rotating gantry inlet 65 fixed side, respectively.

  The rotating gantry 65 of this embodiment is similar to the rotating gantry in a general particle beam therapy system. When the dispersion and its gradient are both 0 on the rotating gantry inlet 65 rotation side, both the dispersion and the gradient at the irradiation point are also present. The amount of excitation of the quadrupole electromagnet in the rotating gantry 60 is controlled to be zero. In other words, the rotating gantry 60 does not generate a new dispersion in the beam transport from the rotating side of the rotating gantry entrance 65 to the irradiation point. In the rotating gantry 60 of the present embodiment, the beam size at the irradiation point is smaller than the beam size at the rotating gantry inlet 65 rotation side, that is, the beam is converged from the rotating gantry inlet 65 rotation side toward the irradiation point. In addition, the excitation amount of the quadrupole electromagnet in the rotating gantry 65 is controlled. Thus, the horizontal transport matrix Gx and the vertical transport matrix Gy of the rotating gantry 65 can be approximated in the form of Equation 23. The reason why the 1-row and 1-column components of the transport matrices Gx and Gy can be approximated to 0 is that the rotating gantry 65 converges the beam toward the irradiation point, and the 1-row and 3-column components and 2 rows and 3 of the transport matrices Gx and Gy. The row component is 0 because the rotating gantry 65 does not generate a new dispersion. Further, the horizontal dispersion ηx1 and the vertical dispersion ηy1 at the irradiation point are approximated by Equation 24 using the horizontal dispersion gradient ηx3 ′ and the vertical dispersion gradient ηy3 ′ on the rotation side of the rotary gantry entrance 65. The subscript 3 of the dispersion represents a value on the rotation gantry inlet 65 rotation side. As shown in Equation 24, the horizontal and vertical dispersions ηx1 and ηy1 at the irradiation point are proportional to the horizontal and vertical dispersion gradients ηx3 ′ and ηy3 ′ on the rotation side of the rotating gantry inlet 65, and the horizontal and vertical dispersions ηx3 and ηy3 Does not depend on

  In this embodiment, the horizontal and vertical dispersions ηx3 and ηy3 on the rotating gantry inlet 65 rotation side are linear combinations of the horizontal and vertical dispersions ηx2 and ηy2 on the rotating gantry inlet 65 fixed side, The vertical dispersion gradients ηx3 ′ and ηy3 ′ are linear combinations of the horizontal and vertical dispersion gradients ηx2 ′ and ηy2 ′ on the fixed side of the rotary gantry inlet 65. Accordingly, when the horizontal and vertical dispersion gradients ηx2 ′ and ηy2 ′ on the fixed side of the rotating gantry 65 are both zero, the horizontal and vertical dispersion gradients ηx3 ′ and ηy3 ′ on the rotating gantry 65 rotating side are both zero. . In this embodiment, the horizontal and vertical dispersion gradients ηfx2 ′ and ηfy2 ′ derived from the acceleration frequency on the rotating gantry fixed side and the horizontal and vertical dispersion gradients ηBx2 ′ and ηBy2 ′ derived from the deflection magnetic field are all 0, so that the rotation is performed. The horizontal and vertical dispersion gradients ηfx3 ′ and ηfy3 ′ derived from the acceleration frequency on the gantry rotation side and the horizontal and vertical dispersion gradients ηBx3 ′ and ηBy3 ′ derived from the deflection magnetic field are all zero. Therefore, from Equation 25, in this embodiment, the horizontal and vertical dispersions ηfx1 and ηfy1 derived from the acceleration frequency at the irradiation point and the horizontal and vertical dispersions ηBx1 and ηBy1 derived from the deflection magnetic field are all zero.

  When the acceleration frequency of the synchrotron 10 varies during beam irradiation in the particle beam therapy system of the present embodiment, the horizontal position and momentum of the extracted beam vary, but the horizontal and vertical dispersions ηfx1, derived from the acceleration frequency at the irradiation point, Since ηfy1 is 0, the irradiation beam position is kept constant regardless of the shift of the acceleration frequency. Similarly, even when the excitation amount of the deflecting electromagnet 11 of the synchrotron 10 fluctuates during beam irradiation, the horizontal and vertical dispersions ηBx1 and ηBy1 derived from the deflection magnetic field at the irradiation beam position are 0, so that the irradiation beam position is The deflection electromagnet 11 is kept constant regardless of the deviation of the excitation amount.

  As described above, in the particle beam therapy system of this embodiment, the rotating gantry entrance 65 is fixed to the horizontal dispersion derived from the acceleration frequency and the horizontal dispersion derived from the deflection magnetic field defined for the extraction beam from the synchrotron 10. Since the control device 25 controls the amount of excitation of the quadrupole electromagnets 62a to 62f in the high energy beam transport system 20 so that the gradients of these dispersions on the side become zero, the steering electromagnet 24 in the high energy beam transport system 20 The fluctuation of the irradiation beam position can be suppressed without using an expensive pattern power source for the power source.

  The particle beam therapy system according to the present embodiment has a configuration in which six quadrupole electromagnets 62a to 62f are installed between the outlet of the synchrotron 10 and the rotary gantry inlet 65. However, there are six quadrupole electromagnets installed in this section. It can be more than the table. When more than six quadrupole electromagnets are installed between the outlet of the synchrotron 10 and the rotary gantry inlet 65, the beam loss in the high energy beam transport system 20 can be suppressed as in the first embodiment. is there. Further, the quadrupole electromagnets 62a to 62f may be installed in any straight line portion from the outlet of the synchrotron 10 to the rotating gantry inlet 65.

  In the particle beam therapy system according to the present embodiment, as in the first embodiment, two or more deflecting electromagnets for deflecting the beam included in the high energy beam transport system 20 in the horizontal direction may be used, and the high energy beam transport system 20 generates the beam. It is good also as a structure which does not have one deflection | deviation electromagnet which deflects in a horizontal direction. Similarly, any number of deflection electromagnets and quadrupole electromagnets may be included in the rotating gantry 60.

  In the particle beam therapy system of this embodiment, the gradient of the horizontal dispersion derived from the acceleration frequency and the gradient of the horizontal dispersion derived from the deflection magnetic field on the fixed side of the rotating gantry inlet 65 are exactly zero for the same reason as in the first embodiment. It does not need to be corrected.

  In the particle beam therapy system of the present embodiment, the extraction deflector 15 may deflect the beam in the vertical direction. Further, a configuration may be provided that includes a deflecting electromagnet that deflects the beam in the vertical direction between the outlet of the synchrotron 10 and the rotary gantry inlet 65. When the beam is deflected in the vertical direction by the rotating gantry inlet 65, the fluctuation of the irradiation beam position is suppressed by installing eight or more quadrupole electromagnets between the outlet of the synchrotron 10 and the rotating gantry inlet 65. Is possible. Specifically, the horizontal and vertical dispersion gradients ηfx2 ′ and ηfy2 ′ derived from the acceleration frequency on the fixed side of the rotating gantry inlet 65 and the horizontal and vertical dispersion gradients ηBx2 ′ and ηBy2 ′ derived from the deflection magnetic field are all zero. By controlling the amount of excitation of the quadrupole electromagnet in the high energy beam transport meter 25 by the control device 25, the fluctuation of the irradiation beam position is suppressed.

(Appendix)
In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  A particle beam therapy system and apparatus, and a particle beam therapy system control method according to the present invention include a particle beam therapy program for causing a computer to execute each procedure, a computer-readable recording medium recording the particle beam therapy program, and a particle beam. It can be provided by a program product including a treatment program and loadable into the internal memory of the computer, a computer such as a server including the program, and the like.

DESCRIPTION OF SYMBOLS 1 Injector 2 Low energy beam transport system 10 Synchrotron 11 Bending electromagnet 12 Quadrupole electromagnet 13 High frequency acceleration cavity 14 Incident inflector 15 Extraction deflector 20 High energy beam transport system 21 Bending electromagnet 22 Quadrupole electromagnet 23 Quadrupole electromagnet power supply 24 Steering Electromagnet 25 Control device 30 Irradiation field forming device 40 Patient 41 Affected part 50 Measuring part 51 Bending electromagnet 52 Quadrupole electromagnet 53 Quadrupole electromagnet power supply 60 Rotating gantry 62 Quadrupole electromagnet 63 Quadrupole electromagnet power supply 70 Cyclotron

Claims (15)

A particle beam therapy system,
An accelerator that accelerates and extracts charged particle beams;
A beam transport system having a plurality of quadrupole electromagnets for adjusting the shape of the charged particle beam, and transporting the charged particle beam extracted from the accelerator to an irradiation target;
With respect to the charged particle beam in the beam transport system, perpendicular to the traveling direction of the charged particle beam, along the radial direction of the deflecting electromagnet of the accelerator or the plane direction including the orbiting beam or central orbit of the accelerator The plurality of first dispersions defined in the first direction, which is the first direction, derived from the accelerator, become zero or substantially zero at the position of the irradiation target. A control device for controlling the amount of excitation of each of the quadrupole electromagnets;
A particle beam therapy system comprising:
The particle beam therapy system according to claim 1,
In the control device, the beam size at the irradiation target position and the rate of change thereof are predetermined values, and two kinds of first dispersions derived from the accelerator are zero or zero at the irradiation target position. A particle beam therapy system characterized in that the amount of excitation of each of the plurality of quadrupole electromagnets in the beam transport system is controlled to be substantially zero.
The particle beam therapy system according to claim 1,
The particle radiation therapy system characterized in that the two kinds of first dispersions are a dispersion derived from an acceleration frequency (ηfx1) and a dispersion derived from a deflection magnetic field (ηBx1).
The particle beam therapy system according to claim 3,
The control device is configured to determine an excitation amount of each of the plurality of quadrupole electromagnets from a model created from the equipment arrangement of the beam transport system, a Twiss parameter of a beam extracted from the accelerator, and the acceleration frequency in the first direction. A particle beam therapy system characterized by calculating from a dispersion (ηfx0) and its gradient (ηfx0 ′), a dispersion (ηBx0) derived from the deflection magnetic field in the first direction and its gradient (ηBx0 ′).
The particle beam therapy system according to claim 1,
The controller reads the two kinds of first direction dispersions (ηfx0, ηBx0) and their gradients (ηfx0 ′, ηBx0 ′) and Twiss parameters at the accelerator exit point,
The controller calculates a transport matrix (Ax, Ay) from the accelerator exit point to the irradiation target position using the preset design value of the excitation amount of each of the plurality of quadrupole electromagnets,
The control device includes the two kinds of first direction dispersions (ηfx0, ηBx0) and their gradients (ηfx0 ′, ηBx0 ′) and the transport matrix (Ax, Ay) of the beam transport system at the accelerator exit point. From the two types of first direction dispersions (ηfx1, ηBx1) at the position of the irradiation target, and the irradiation from the Twiss parameter at the accelerator exit point and the transport matrix (Ax, Ay) of the beam transport system Calculate the Twiss parameter at the location of interest;
The control device is set to 0 when the two types of dispersions in the first direction (ηfx1, ηBx1) at the irradiation target position are both 0 and the Twiss parameter at the irradiation target position matches a target value. In accordance with an objective function that is a function of the following, the value of the objective function is calculated from the two types of dispersions in the first direction (ηfx1, ηBx1) and the calculation result of the Twiss parameter at the position of the irradiation target,
The control device calculates an excitation amount of the plurality of quadrupole electromagnets so that a value of the objective function is equal to or less than a predetermined threshold;
The particle beam therapy system, wherein the control device controls each of the plurality of quadrupole electromagnets according to the calculated excitation amount.
The particle beam therapy system according to claim 1,
A measuring unit for measuring the two kinds of dispersions in the first direction (ηfx0, ηBx0), their gradients (ηfx0 ′, ηBx0 ′), and the Twiss parameter at the accelerator exit point, and supplying the measured parameters to the controller; A particle beam therapy system further comprising:
The particle beam therapy system according to claim 1,
The fact that the two types of first dispersions are substantially zero at the position of the irradiation target means that the product of the first dispersion and the momentum shift at the position of the irradiation target is a fluctuation of a predetermined irradiation beam position. A particle beam therapy system characterized by being within a width limit.
The particle beam therapy system according to claim 1,
The controller is
With respect to the charged particle beam in the beam transport system, the two types of first dispersions (ηfx1, ηBx1) derived from the accelerator, the traveling direction of the charged particle beam and the direction perpendicular to the first direction The plurality of second dispersions (ηfy1, ηBy1) derived from the accelerator defined in the second direction are set to 0 or substantially 0 at the irradiation target position. A particle beam therapy system for controlling the amount of excitation of each of the quadrupole electromagnets.
The particle beam therapy system according to claim 8, wherein
The beam transport system is
A deflection electromagnet that deflects the beam taken out from the accelerator toward the irradiation target in the first direction;
A plurality of deflection electromagnets for deflecting the beam a plurality of times in the second direction and irradiating the irradiation object with the beam from the second direction;
With
A particle beam therapy system characterized in that the irradiation target can be irradiated with the beam from the second direction.
The particle beam therapy system according to claim 1,
A rotating gantry capable of inputting the beam from the beam transport system and irradiating the irradiation target from a plurality of different directions;
Gradients (η′fx2, η′Bx2) in the traveling direction of the charged particle beam of the two types of first dispersions defined for the first direction at the entrance point of the rotating gantry are 0 or substantially 0 The particle beam therapy system, wherein the control device controls the amount of excitation of each of the plurality of quadrupole electromagnets.
The particle beam therapy system according to claim 1,
The accelerator is a synchrotron;
One of the two types of first dispersion is a change in beam position and a change in beam momentum caused by a change in acceleration frequency by a high-frequency acceleration cavity that accelerates the circulating beam of the synchrotron to a predetermined energy. A dispersion derived from the acceleration frequency defined for (ηfx1 or ηfy1),
Another one of the two types of the first dispersion is for the change of the beam position and the change of the beam momentum caused by the change of the deflection magnetic field by the plurality of deflection electromagnets forming the circular beam orbit of the synchrotron. A particle beam therapy system characterized by being a dispersion (ηBx1 or ηBy1) derived from a defined deflection magnetic field.
The particle beam therapy system according to claim 1, wherein
The accelerator is a cyclotron;
One of the two types of first dispersions is derived from the acceleration frequency defined for the change of the beam position and the change of the beam momentum caused by the change of the high frequency voltage applied to the Dee electrode constituting the cyclotron. Dispersion (ηfx1 or ηfy1),
Another one of the two types of first dispersion is derived from the deflection magnetic field defined for the change in beam position and the change in beam momentum caused by the change in magnetic field generated between the magnetic poles constituting the cyclotron. A particle beam therapy system characterized by having a dispersion (ηBx1 or ηBy1).
The dispersion of the extraction beam in the first direction at the exit point of the accelerator is a beam position deviation Δx0 of the extraction beam in the first direction at the same point and a momentum deviation Δp normalized by the design value of the momentum. A particle beam therapy system represented by Δx0 / (Δp / p) using / p.
A particle beam therapy device,
A beam transport system having a plurality of quadrupole electromagnets for adjusting the shape of the charged particle beam extracted from the accelerator, and transporting the charged particle beam extracted from the accelerator to an irradiation target;
With respect to the charged particle beam in the beam transport system, perpendicular to the traveling direction of the charged particle beam, along the radial direction of the deflecting electromagnet of the accelerator or the plane direction including the orbiting beam or central orbit of the accelerator The plurality of first dispersions defined in the first direction, which is the first direction, derived from the accelerator, become zero or substantially zero at the position of the irradiation target. A control device for controlling the amount of excitation of each of the quadrupole electromagnets;
A particle beam therapy system comprising:
A method for controlling a particle beam therapy system, comprising:
The charged particle beam is accelerated and extracted by the accelerator,
By transporting the charged particle beam taken out from the accelerator to the irradiation target by a beam transport system having a plurality of quadrupole electromagnets for adjusting the shape of the charged particle beam,
The control device includes the radial direction of the deflecting electromagnet of the accelerator or the orbiting beam or center trajectory of the accelerator perpendicular to the traveling direction of the charged particle beam with respect to the charged particle beam in the beam transport system. In the beam transport system, two kinds of first dispersions derived from the accelerator, which are defined with respect to a first direction that is a direction along a plane direction, are 0 or substantially 0 at the position of the irradiation target. Controlling the amount of excitation of each of the plurality of quadrupole electromagnets,
A method for controlling a particle beam therapy system.

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