A beam transport system for transporting energy-varying, accelerated charged particles from the accelerator exit to the target.

Abstract

The present invention relates to a charged particle beam therapy system comprising: a patient unit (10); an accelerator unit (20) configured to accelerate charged particles; and a beam transport system (30) configured to guide a particle beam having an energy (Ej) between 40 and 450 MeV / u along a corresponding beam trajectory (40e) centered on a central trajectory (40m) to a target (11) located within the patient unit (10), wherein the beam transport system (30) comprises: a bending unit (33) having a gap (33g) between the poles (33p) of a fixed magnetic field dipole, the bending unit being configured to receive and bend the central trajectory (40m) in a bending plane (Y, Z). The beam transport system (30) further comprises an upstream stairer (35u) located upstream of the bending unit (33) and configured to deflect the beam trajectory (40e) from the central trajectory (40m) in a bending plane (Y, Z). The magnitude of the uniform magnetic field (B35) in the upstream stearer (35u) can be controlled to change the entry position (Yij) and entry angle (θ33i) of the beam trajectory at the bending unit entrance (33i) according to the beam energy (Ej) of the particle beam.

Description

Technical Field

[0001] The present invention relates to a charged particle beam therapy system comprising a beam transport system for transporting a beam of charged particles from the exit of an accelerator to a target, the beam transport system being capable of rapidly adapting to transport them to the target when the energy of the charged particles changes. The present invention comprises a bending unit having a fixed magnetic field dipole for bending the beam, and a steerer arranged upstream of the bending unit for guiding the beam to a specific position and an entry angle at the entrance of the bending unit according to the energy of the beam, whereby the beam is transported to the target regardless of the energy of the beam. The size of the beam transport unit can be reduced, and rapid adaptation to beams of varying energies facilitates the implementation of high-speed therapies such as FLASH.

Background Art

[0002] Hadron therapy such as proton beam therapy is an advantageous radiation therapy for specific tumors in that it deposits a dose accurately in tumor cells to kill them. The TCP / NTCP ratio, which is the ratio of the tumor control probability (TCP) to the normal tissue complication probability (NTCP), is an index indicating the ratio of the killing rate of tumor cells to the damage rate to normal cells. A high TCP / NTCP ratio is desirable. Hadron therapy has a higher TCP / NTCP ratio than other radiation therapy techniques such as X-rays. Charged particles such as protons or carbon are accelerated in an accelerator and extracted therefrom. The accelerator can be a cyclotron, a synchrotron, a synchrocyclotron, a LINAC, or the like. The beam of charged particles is transported and guided through a beam transport system from the accelerator to the tumor target of a patient introduced into the patient unit. A gantry is a beam transport unit designed to rotate around a patient to control and change the irradiation angle to the target. In a stationary beam transport unit, it is also possible to control and change the rotation angle by moving the patient / target. There is also a description of a stationary gantry. For example, U.S. Patent Application Publication No. 2021187328 describes a stationary gantry equipped with a toroidal magnet.

[0003] Recent research suggests that a technique commonly known as FLASH, which involves depositing doses at ultra-high deposition rates exceeding 1 Gy / s, or even 40 Gy / s, may further improve the TCP / NTCP ratio in some tissues. When the same dose is administered at an ultra-high deposition rate, it appears to have less impact on normal cells than when administered at a lower rate, while tumor cell killing rates seem less affected by the deposition rate. Due to the limitations of existing accelerators, FLASH can be advantageously applied using pencil beam scanning (PBS), a technique that sequentially deposits doses at ultra-high rates according to a specific order of sub-volumes that make up the overall volume of the tumor target. The deposited doses may differ for each sub-volume, and the beam movement from one sub-volume to the next in a specific order must be rapid to maintain the FLASH effect.

[0004] The energy E of a charged particle at the accelerator exit is proportional to the square of its velocity v (i.e., E∝v 2 The velocity v of charged particles, and consequently their energy E, can be controlled and varied in various ways depending on the type of accelerator used. Some accelerators can extract particle beams of different energies. For example, the synchrotron and synchrocyclotron described in European Patent No. 3876679, or the cyclotron with a specific stripper assembly described in European Patent No. 3503693. On the other hand, in other accelerators, such as cyclotrons that do not have a specific stripper assembly of the type described in European Patent No. 3503693, the output energy of the particle beam is fixed and cannot be changed. To change the energy of the particle beam reaching the target, the beam transport system may be equipped with a damping system comprising a bending unit and one or more material blocks that interact with the beam to adjust its energy before reaching the target. The damping system may require a series of focusing elements to compensate for disturbances in the lateral beam characteristics as it passes through the material blocks, and a concrete shielding structure to hold emitted secondary particles such as neutrons.

[0005] The beam transport system allows for precise changes in the beam angle upon reaching the target, as well as precise control of beam spot size and position during spot scanning. Existing gantry bending units often feature variable magnetic field electromagnets, which can also control the direction of the particle beam according to its energy by changing its magnetic field amplitude. However, variable magnetic field electromagnets are complex, quite large, and heavy, and their adaptation to fluctuations in the energy of charged particle beams is relatively slow, thus extending treatment time. This extended treatment time is uncomfortable for patients and makes them unsuitable for treating migratory tumors or performing FLASH treatments.

[0006] U.S. Patent No. 7,582,886 describes a gantry with a bending unit comprising a series of blocks consisting of three fixed-field dipoles arranged in series to alternately focus and defocus a particle beam, thereby forming a fixed-field alternating gradient (FFAG). Despite having only fixed-field electromagnets, which are simpler and more compact than variable-field electromagnets, the gantry described in U.S. Patent No. 7,582,886 is still very large with a bending radius exceeding 3 m (see Figure 3 in U.S. Patent No. 7,582,886), and both the weight and cost of the gantry are increased due to the composition of numerous fixed-field dipoles arranged in parallel.

[0007] In Tesse et al., 13th Int. Particle Acc. Conf., IPAC2022, Bangkok, (2022) 2941-2944, they presented a chromatic aberration-free gantry with a smaller FFAG bending unit with a theoretical bending radius of 2.1 meters. However, this paper only shows results from the early stages of development, and the described gantry is not yet technically operational and still maintains relatively large dimensions.

[0008] U.S. Patent Application Publication No. 2021 / 0187328 describes a stationary gantry equipped with a toroidal magnet formed from a plurality of discrete planar coils spaced apart from each other, extending radially from a principal axis, and configured to generate a periodically symmetric magnetic field around the principal axis. This stationary gantry with the toroidal magnet is configured to receive a charged particle beam at different radial positions depending on the momentum-to-charge ratio of the beam, and to focus the beam to substantially the same point. The stationary gantry of U.S. Patent Application Publication No. 2021 / 0187328 is proposed as a solution for miniaturizing a rotating gantry, which is defined in this document as an "extremely large structure with high mechanical rigidity."

[0009] There remains a demand for smaller beam transport systems that can rapidly adapt to particle beam energy fluctuations and ensure that the particle beam reaches its target independently of its energy. Beam transport systems that are better suited for rapid treatment for patient comfort and enable the treatment of moving tumors and FLASH treatments are also desired. [Overview of the project]

[0010] The present invention is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims. In particular, the present invention relates to a charged particle beam therapy system, • A patient unit that supports the patient in a designated position, An accelerator unit configured to accelerate charged particles and deliver a particle beam of accelerated charged particles with an energy of 40-450 MeV / u (MeV per nucleon) from an exit, wherein the particles are preferably selected from hadrons, more preferably from protons, carbon ions, helium ions, and oxygen ions. The system comprises a beam transport system configured to guide a particle beam, whose energy varies between 40 and 450 MeV / u, along a corresponding beam trajectory centered on a central orbit originating from the exit of the accelerator unit, to a target located within the patient unit, and the beam transport system is configured The bending unit comprises a gap between the poles of a fixed magnetic field dipole, and the bending unit is configured to accept a central orbit and bend the central orbit between the inlet and outlet of the bending unit, in the bending plane (Y,Z), at an angle of 20 to 270°, preferably 40 to 140°, in the bending plane, where the central orbit is contained within the bending plane (Y,Z) and Y⊥Z. Regarding charged particle beam therapy systems.

[0011] The beam transport system further includes an upstream staircase located upstream of the bending unit, configured to deflect the beam trajectory at an angle of -15 to +15° from the central trajectory within the bending plane (Y,Z). The upstream staircase is configured to provide a deflection function, which is achieved by generating a uniform magnetic field (B35) within the upstream staircase, the magnitude of which can be controlled to change the entry position and entry angle of the beam trajectory at the bending unit inlet (33i) depending on the beam energy of the particle beam.

[0012] The charged particle beam therapy system preferably includes a processor configured to control the amplitude of the uniform magnetic field of an upstream stairer according to the beam energy, thereby controlling the position and entry angle of the beam trajectory at the bending unit inlet, and thereby causing the beam trajectory to travel along a curved trajectory with a bending radius corresponding to the beam energy, passing through a convergence position downstream of the bending unit outlet. The angle of the beam trajectory at the convergence position depends on the beam energy. The angle of the beam trajectory relative to the central trajectory at the convergence position (330) preferably does not depend on the beam energy of the particle beam, but it does not necessarily not. If the beam angle at the convergence position changes with the beam energy, the beam transport system may include a downstream stairer located at the convergence position and configured to deviate the beam trajectory to a common beam trajectory, independent of the beam energy.

[0013] In a preferred embodiment of the present invention, the bending unit may comprise one or more bending subunits arranged along a beam trajectory. Each bending subunit comprises a gap extending along a curved shape from the subunit inlet to the subunit outlet on the bending plane (Y,Z), the gap separating first and second magnet coils symmetrically positioned on either side of the bending plane. In one embodiment, the first and second magnet coils may surround first and second magnet poles, each made of a ferromagnetic material. In an alternative embodiment, the first and second magnet coils are made of a superconducting material. In either embodiment, the first and second magnet coils are configured to receive a fixed current, thus forming a fixed magnetic field dipole.

[0014] The gap preferably has the following shape: In a plane parallel to the bending plane (Y,Z), the gap defines a bend centered on the central orbit, enclosed between a near wall with a small radius of curvature and a far wall with a large radius of curvature, where the distance separating the near and far walls is greater on the inlet side of the bending unit of the gap than on the outlet side. The width of the gap, measured parallel to the X-axis perpendicular to the bending plane (i.e., X⊥Y⊥Z), is greater on the near wall side than on the far wall side. Therefore, the magnetic field within the gap (33g) of each bending subunit shows its highest value in the region adjacent to the far wall and its lowest value in the region adjacent to the near wall. This produces a focusing effect on the particle beam. The maximum value of the magnetic field in the gap of each bending subunit is between 1.5T and 2.6T, preferably between 1.9T and 2.4T, when the first and second magnet coils surround the first and second magnet poles made of ferromagnetic material. In the case of a superconducting coil, the maximum value of the magnetic field can be between 2.5T and 9T, preferably between 3.5T and 6T.

[0015] In a preferred embodiment, the subunit inlet (33i) and / or subunit outlet (33o) of at least one bending subunit of the bending unit can be non-perpendicular to the central trajectory. This allows for greater control over the length of the beam trajectory along the gap, and consequently, the trajectory angle at the convergence position.

[0016] The upstream stearer (35u) may be a dipole configured to provide only deviation functionality, or to provide deviation functionality and 1D scanning functionality, the 1D scanning functionality being configured to scan the beam trajectory in one direction across the beam trajectory to enable scanning of a target. Alternatively, the upstream dipole may be an octupole configured to provide deviation functionality and one or both of the following functions: • Focusing function configured to reduce the size of the particle beam cross-section in one or two directions across the beam trajectory, and / or • 1D or 2D scanning capabilities configured to scan the beam trajectory in one or two directions across the beam trajectory, enabling target scanning.

[0017] The beam transport system may include one or more focusing elements for focusing an accelerating beam along a central orbit in a cross-sectional plane (X, Y) perpendicular to the central orbit, and preferably a scanner for deflecting the beam trajectory at an angle of -15° to +15° in a direction perpendicular to the central orbit, the scanner being configured to control the beam trajectory for scanning over a target.

[0018] The beam transport system of the present invention relates to a gantry configured to rotate a bending plane (Y,Z) around a rotation axis that passes through the target. In the latter case, the irradiation angle to the target can be changed by moving the patient unit. [Brief explanation of the drawing]

[0019] To fully understand the nature of this invention, refer to the following detailed description, which should be read in conjunction with the accompanying drawings.

[0020] [Figure 1a] Figure 1a shows an embodiment of the charged particle beam therapy system according to the present invention. [Figure 1b] Figure 1b shows an embodiment of the charged particle beam therapy system according to the present invention. [Figure 1c]FIG. 1c shows an embodiment of a charged particle beam therapy system according to the present invention. [Figure 2] FIG. 2 shows the lateral deviation of the beam trajectory perpendicular to the central trajectory in the bending plane (Y, Z) with respect to the central trajectory as a function of the position along the central trajectory for two beam energies. [Figure 3a] FIG. 3a shows a perspective view of half of a part of the bending unit according to the present invention. [Figure 3b] FIG. 3b shows a side view of a part of the bending unit according to the present invention in the plane (Y, Z). [Figure 3c] FIG. 3c shows a front view of a part of the bending unit according to the present invention in the plane (X, Y). [Figure 3d] FIG. 3d shows the beam trajectories of beams of different energies controlled by a steerers positioned upstream of the bending unit. [Figure 4a] FIG. 4a shows an embodiment of a quadrupole used as a focusing unit. [Figure 4b] FIG. 4b shows an embodiment of a quadrupole used as a focusing unit. [Figure 5a] FIG. 5a shows an embodiment of an octupole used as a focusing unit or as a multifunctional upstream or downstream steerer. [Figure 5b] FIG. 5b shows an embodiment of an octupole used as a focusing unit or as a multifunctional upstream or downstream steerer. [Figure 6a] FIG. 6a shows a front view of a dipole used as an upstream steerer. [Figure 6b] FIG. 6b shows a side view of a dipole used as an upstream steerer. DETAILED DESCRIPTION OF THE INVENTION ​​​​

[0022] The patient unit (10) is configured to support the patient in a predetermined position. The target (11) is located within the patient unit (10) and contains the patient's tumor cells to be irradiated. The patient may or may not be in a supine position, and the patient unit (10) may be fixed or movable.

[0023] The accelerator unit (20) is configured to accelerate charged particles and emit a particle beam of accelerated charged particles with an energy of 40-450 MeV / u (MeV per nucleon) from the outlet (20o). The charged particles are hadrons, preferably protons, carbon ions, helium ions, or oxygen ions. The accelerator unit (20) may be a type that changes the energy of the output particle beam, such as a synchrotron or LINAC, or a type that outputs a particle beam with a fixed energy. In the latter case, the beam transport system (30) must be equipped with a decay unit, which will be described later.

[0024] The beam transport system (30) is configured to guide a particle beam with an energy (Ej, j=1-3) varying between 40 and 450 MeV / u along a corresponding beam trajectory (40e) centered on a central orbit (40m) originating from the exit (20o) of the accelerator unit (20) to a target (11) located within the patient unit (10). The bending unit (33) has a gap (33g) between the poles (33p) of a fixed magnetic field dipole extending from the beam bending unit inlet (33i) to the bending unit exit (33o). Therefore, the magnetic field (B33) within the gap (33g) is not changed to correct the bending radius of the beam trajectory (40e) in accordance with the beam energy (Ej). This bending unit is configured to receive and bend a central orbit (40m) within the bending plane (Y,Z) at an angle of 20° to 270°, preferably 40° to 140°, between the bending unit inlet (33i) and the bending unit outlet (33o), where the central orbit (40m) is contained within the bending plane (Y,Z) and Y⊥Z. The beam trajectory of a particle beam of full energy suitable for a charged particle beam therapy system is contained within the bending plane (Y,Z) and surrounded within the shape of the gap (33g).

[0025] The essence of the present invention is to include an upstream staircase (35u) positioned upstream of the bending unit (33) within the first bending module, where upstream and downstream are defined with respect to the direction of beam propagation. The upstream staircase (35u) is configured to deflect the beam trajectory (40e) from the central trajectory (40m) by an angle between -15° and +15° in the bending plane (Y,Z). The magnitude of the uniform magnetic field (B35) of the upstream staircase (35u) can be varied depending on the beam energy (Ej, j=1~3) to change the position and entry angle of the beam trajectory at the bending unit inlet (33i).

[0026] The upstream stairwell (35u) is configured to provide a deviation function. This deviation function is achieved by generating a uniform magnetic field (B35) within the target region. The amplitude of the uniform magnetic field (B35) of the upstream stairwell (35u) in accordance with the beam energy (Ej) is preferably controlled by a processor (not shown). By controlling the entry position (Yij) and entry angle (θ33i) of the beam trajectory at the bending unit inlet (33i), it is possible to drive the beam trajectory (40e) along a curved trajectory with a radius of curvature dependent on the beam energy (Ej) and pass it through the convergence position (330) downstream of the bending unit outlet (33o). The angle between the beam trajectory (40e) and the central trajectory (40m) at the convergence position (330) is preferably independent of the beam energy (Ej) of the particle beam. However, as shown in Figure 3d, if the angle of the beam trajectory (40e) at the convergence position (330) depends on the beam energy (Ej), the beam transport system (40) may include a downstream stairer (35d) positioned at the convergence position (330) and configured to deviate the beam trajectory to a common beam trajectory that does not depend on the beam energy (Ej).

[0027] As shown in Figures 1a-1c, the beam transport system (40) may include one or more focusing elements (31) and staircases (35) upstream and downstream of the bending unit (33) to compensate for degradation of beam characteristics. However, the upstream staircase (35u) is located upstream of the bending unit inlet (33i). The beam transport system (40) may also include a scanner configured to control the beam trajectory to scan over the target (11), particularly in PBS therapy. The upstream staircase (35u) must perform the primary function of deviating the beam trajectory in accordance with the beam energy (Ej) and arriving at the bending unit inlet (33i) at an entry position (Yij) and entry angle (θ33i) corresponding to the beam energy (Ej). In certain embodiments, the upstream staircase (35u) may perform additional functions such as focusing and scanning the particle beam. This has the advantage of reducing the overall size, weight, and cost of the beam transport unit (30) because the upstream staircase (35u) can replace the focusing elements and scanners that would otherwise be required.

[0028] Bending unit (33) The bending unit (33) according to the present invention does not include any fluctuating magnetic field electromagnets. It comprises only a fixed magnetic field dipole having a dipole magnetic field component. The fixed magnetic field dipole may be a permanent magnet or an electromagnet whose magnetic field cannot be changed (supplying a fixed current to the coil), as shown in Figures 3a to 3d. Compared to fluctuating magnetic field electromagnets, fixed magnetic field electromagnets are substantially smaller, simpler in structure, and less expensive. It is also possible to achieve higher values ​​for the magnetic field (B33) in the gap (33g). Not changing the magnetic field in the bending unit (33) also has the advantage of allowing the optical system to adapt to fluctuations in beam energy (Ej) more quickly than in the case of fluctuating magnetic field electromagnets.

[0029] In a preferred embodiment of the present invention, the bending unit (33) comprises one or more bending subunits (33n) arranged along the beam trajectory. Figures 1a and 1b show this type of bending unit formed by two bending subunits (33n), and Figure 1c shows a bending unit formed by a single element (or a single bending subunit (33n)). Dividing the bending unit (33) into two (or more) bending subunits (33n) may offer the advantage of inserting a safety feature between the two (or more) bending subunits (33n) configured to shut off the particle beam if the beam trajectory falls outside the safety boundary. This may also facilitate access to the elements of the bending unit during repair and maintenance. Finally, if the particles deviate excessively in the lateral X and Y directions, a focusing element (31) may be inserted between the two (or more) bending subunits (33n), although this is not required. A scanner may also be positioned between the two bending subunits (33n). On the other hand, as shown in Figure 1c, the bending unit (33) formed from a single element is more compact, reducing the overall size of the charged particle beam therapy system.

[0030] As shown in Figures 3a to 3d, each bending (sub)unit (33, 33n) has a gap (33g) that extends along a curved shape on the bending plane (Y, Z) from the (sub)unit inlet (33i, 33ni) to the (sub)unit outlet (33o, 33no). The subunit inlet (33ni) of the bending subunit (33n) located at the uppermost position of the bending unit (33) forms the bending unit inlet (33i), and the subunit outlet (33no) of the bending subunit (33n) located at the lowermost position of the bending unit (33) forms the bending unit outlet (33o). Therefore, the positions of the upstream staircase (35u) and the optionally selected downstream staircase (35d) are defined with respect to the bending unit inlet (33i) and outlet (33o) defined above for a bending unit composed of one or more bending subunits (33n). The number of bending subunits (33n) that form the bending unit (33) is preferably one or two.

[0031] The gap (33g) separates the first and second magnet coils (33c) positioned symmetrically on both sides of the bending plane. In a preferred embodiment, the first and second magnet coils (33c) each surround first and second magnetic poles (33p) made of ferromagnetic material. The maximum value of the magnetic field (B33) in the bending plane and the gap (33g) of the downstream fixed magnetic field dipole (33n) can exceed 1.8 T and is preferably lower than 2.4 T.

[0032] In an alternative embodiment, the first and second magnet coils (33c) are made of superconducting material. In any embodiment, the current applied to the magnet coils is constant (and independent of the beam energy (Ej)).

[0033] The main function of the bending unit is to bend the particle trajectory (40e). To achieve this main function, in a plane parallel to the bending plane (Y, Z) as shown in FIG. 3b, the gap (33g) defines a bend surrounded between a near wall (R1) with a small radius of curvature and a far wall (R2) (R1 < R2) with a large radius of curvature, centered on the central orbit (40m). The distances (hi, ho) separating the near wall and the far wall can be made larger at the entrance (33i) of the bending unit of the gap (33g) than at the exit (33o), thereby allowing a wider range of entry positions (Yij) of the particle beam.

[0034] In a preferred embodiment, the bending unit also has a second function: as the particle beam moves along the curved gap (33g), the shape of the curved gap helps to focus the particle beam. In this embodiment shown in Figure 3c, the width (w1, w2) of the gap (33g) is greater on the near wall side than on the far wall side (w1>w2) when measured along a cross-section (X,Y) perpendicular to the central trajectory (40m). As shown in the insert in Figure 3c, the magnetic field (B33) within the gap (33g) of each bending subunit (33n) is highest in the region adjacent to the far wall and lowest in the region adjacent to the near wall. This magnetic field gradient has the effect of focusing the particle beam in the direction perpendicular to the central trajectory (40m) and in the bending plane as the particle beam moves along the gap (33g). The shape of this gap (33g) may cause a defocus effect on the particle beam in the direction perpendicular to the bending plane (Y,Z), but it is still a preferred embodiment because it reduces the deviation between the extreme energies in the bending plane (Y,Z).

[0035] The maximum value of the magnetic field (B33) in the gap (33g) of each bending subunit (33n) is: When the first and second magnet coils (33c) surround the first and second magnet poles (33p) made of ferromagnetic material, the T is between 1.5T and 2.6T, preferably between 1.9T and 2.4T, or • If the first and second magnet coils (33c) are superconductors, the torque is between 2.5T and 9T, preferably between 3.5T and 6T.

[0036] Because the radius of the central orbit (40m) within the gap (33g) can be reduced to approximately 1000mm, the beam transport system (30) becomes very compact.

[0037] Upstream steerer (35u) As shown in Figure 3d, the primary function of the upstream stairwell is to drive the particle beam at a specific entry position (Yij, j=1~3) and entry angle (θ33i) at the bending unit inlet (33i) in accordance with the beam energy (Ej). This ensures that, under the influence of the fixed magnetic field dipole of the bending unit (33), the particle beam follows a curved trajectory to a convergence position (330) located downstream of the bending unit outlet (33o), independently of the beam energy (Ej). For the upstream stairwell (35u) to satisfy this primary function of the stairwell, only a deviation function is sufficient. This deviation function is obtained by generating a uniform magnetic field (B35) between the two poles of the dipole. The entry position (Yij) and entry angle (θ33i) of the beam trajectory at the bending unit inlet (33i) are controlled according to the particle beam energy (Ej) by changing the uniform magnetic field (B35) within the upstream stairwell (35u) generated by the fluctuating magnetic field electromagnet.

[0038] Preferably, the particle beam exits the bending unit exit (33o) at a fixed exit angle, independent of the particle beam energy (Ej), and passes the convergence position (330) along a fixed trajectory. However, as shown in Figure 3d, if this cannot be achieved, a downstream staircase (35d) can be provided at the convergence position (330) to realign the converging particle beam and form a fixed trajectory downstream of the downstream staircase (35d). It is important to be able to precisely control the trajectory of the particle beam downstream of the bending unit (33) because the target (11) is in close proximity and the particle beam must reach a selected point on the target (11) precisely.

[0039] The upstream stairwell (35u) is configured to deflect the beam trajectory (40e) from the central trajectory (40m) by an angle (θ35) in the bending plane (Y,Z) ranging from -15° to +15°. This is achieved by changing the magnitude of the uniform magnetic field (B35) of the upstream stairwell (35d) to control the entry position (Yij) and entry angle (θ33i) of the beam trajectory at the bending unit inlet (33i) according to the beam energy (Ej) of the particle beam (40e). When the bending unit inlet (33i) is parallel to the exit of the upstream stairwell (35u), θ33i = θ35. However, in the embodiment shown in Figure 3d, this is not achieved, and θ33i ≠ θ35.

[0040] As shown in Figure 3d, the deviation function of the upstream staircase (35u) is necessary to bend the beam trajectory and drive it to the bending unit inlet (33i) at the entry position (Yij) at an entry angle (θ33i) corresponding to the beam energy (Ej). This deviation function is achieved by forming a uniform magnetic field (B35) and controlling its intensity.

[0041] A uniform magnetic field can be generated by any multipole with a symmetry of 2, such as the dipole shown in Figures 6a and 6b, the quadrupole shown in Figures 4a and 4b, the hexapole (not shown), and the octapole shown in Figures 5a and 5b, provided that the current is properly driven within the corresponding coil (3c). The dipole shown in Figures 6a and 6b is preferred when the upstream stearer (35u) is used solely to provide deviation functionality. It should be noted that the dipole, in addition to deviation functionality, also guarantees scanning functionality in only one direction (here, within the bending plane (Y,Z) and perpendicular to the central orbit (40m) = 1D scanning functionality). In this case, there is no need to use quadrupoles or octapoles, as they are more complex, bulky, and expensive than dipoles.

[0042] If, in addition to the deviation function, the upstream stairer (35u) requires further functions such as a focusing function and / or a unidirectional or bidirectional scanning function (=1D or 2D scanning function) on a plane perpendicular to the central orbit (40m), an octupole can be used as the upstream stairer (35u). Referring to Figures 5a and 5b, which show two embodiments of the octupole, the deviation function, which deviates the particle beam in the Y-axis direction, can be achieved by passing current through at least a pair of opposing magnetic elements that form a dipole aligned on the X-axis. The scanning function can be obtained by controlling the current in the dipole aligned along the Y-axis. The focusing function can be obtained by conveniently passing current through the remaining four magnetic elements that form a quadrupole. Thus, it is necessarily possible to integrate multiple functions, including the deviation function, into a single upstream stairer (35u), which may be advantageous in terms of the size and weight of the beam transport system (30). As engineers are well aware, it should be noted that the function of quadrupoles and octupoles depends on the direction of current circulation in the corresponding coils (3c) of different magnetic elements.

[0043] In summary, in a preferred embodiment, the upstream staircase (35u) may be one of the following: • A dipole configured to provide only deviation functionality. A dipole configured to provide a deviation function and a 1D scanning function configured to scan the beam trajectory in one direction across the beam trajectory in order to scan a target (11), • In addition to the deviation function, o Focusing function configured to reduce the size of the particle beam cross-section in one or two directions across the beam trajectory, and / or o A 1D or 2D scanning function configured to scan the beam trajectory in one or two directions across the beam trajectory in order to enable scanning of the target (11), An octagonal element configured to provide...

[0044] The uniform magnetic field (B35) required to provide deviation functionality can be varied between ±2T, preferably ±1T, depending on the length of the upstream stairwell (35u) measured along the central trajectory (40m), to deviate high-energy particle beams, such as particle beam 40e(E3) with energy E3 shown in Figure 3d, and low-energy particle beams, such as particle beam 40e(E1) with energy E1, by an angle of ±15°. A uniform magnetic field of 0T will not deviate the beam trajectory. It can preferably be applied when the particle beam has a central energy (Em) and follows a central trajectory, as shown in Figure 3d with a particle beam of energy E2=Em. Naturally, 1D or 2D scanning functionality is not possible with a uniform magnetic field of 0T.

[0045] The first bending module is formed by the upstream staircase (35u) and the bending unit (33). The gist of the present invention is a first bending module that combines a bending unit (33) having one or more fixed magnetic field dipoles (33n) with an upstream deflector (35u) arranged upstream of the bending unit (33) as described above. According to the treatment plan, the particle beam is transported along the beam transport system (30) and reaches the upstream deflector (35u) at a given energy (Ej). It is desirable for the particle beam to reach the upstream deflector (35u) at the same entry point and in the same direction regardless of the beam energy (Ej), but this is not essential, and the particle beam can reach the upstream deflector (35u) at different entry points and / or in different directions depending on the beam energy (Ej). Fig. 3d shows a specific embodiment in which three particle beams with energies E1, E2, E3 (E1 < E2 < E3) reach the upstream deflector (35u) at the same entry point but in different directions depending on the beam energy (Ej). Regardless of the entry point and direction of the particle beam in the upstream deflector (35u), it is essential to control the uniform magnetic field (B35) in the upstream deflector (35u), thereby deviating the beam trajectory according to their energies (Ej) so that the particle beam reaches the bending unit inlet (33i) at a specific entry angle (θ33i) at a specific entry position (Yij), whereby the particle beam follows the corresponding bending trajectory within the bending unit (33), and the particle beam can converge at a convergence position (330) located downstream of the bending unit outlet (33o). The control of the uniform magnetic field (B35) in the upstream deflector is preferably performed by a processor.

[0046] The radius of curvature (r) of the bending trajectory in each bending sub-unit (33n) increases with energy (Ej) (velocity (v)) and is inversely proportional to the magnetic field (B) within the gap (33g). Therefore, the radius of curvature of a particle beam with low energy (E1) is smaller than that of a particle beam with high energy (E3), with E1 < E3. Thus, the gap (33g) of each bending sub-unit (33n) must be carefully designed to accommodate the beam trajectories of particle beams with energies (Ej) ranging from the maximum value to the minimum value, which define the energy tolerance of the beam transport unit (30). Thus, as shown in Fig. 3d, the upstream steerers are configured to deflect the beam trajectory of a particle beam with low energy (E1) such that the beam trajectory reaches the bending unit entrance (33i) at an entry position (Yi1) close to the near wall (R1) with a small radius of curvature. Conversely, the upstream steerers are configured to deflect the beam trajectory of a particle beam with higher energy (E3) such that the beam trajectory reaches the bending unit entrance (33i) at an entry position (Yi3) close to the far wall (R3) with a large radius of curvature. The length (hi) of the gap (33g) at the bending unit entrance (33i) measured along the Y-axis must be long enough to accommodate the entry positions (Yij) of the beam trajectories of all energies within the energy tolerance of the beam transport unit (30).

[0047] The exit position and exit angle of the beam trajectory (40e) relative to the central trajectory (40m) naturally depend on the radius of curvature of the beam trajectory within the bending subunit (33n), but also on the length of the beam trajectory within the gap (33g). The length of the beam trajectory within the gap (33g) depends, in particular, on the entry angle (θ33i), and the entry angle (θ33i) itself depends, in particular, on the orientation of the bending unit entrance (33i). Depending on the beam energy (Ej), the bending unit entrance (33i) can be non-perpendicular to the central trajectory (40m) to give further design freedom for controlling the distance of the section of the beam trajectory (40e) contained within the gap (33g) (i.e., between the bending unit entrance (33i) and the bending unit exit (33o)). In the bending plane (Y,Z), the bending unit entrance (33i) can be non-linear, for example, curved or segmented. In the embodiment shown in Figure 3d, this distance is extended for high-energy (E3) particle beams and shortened for low-energy (E1) particle beams, which in turn affects the entry angle (θ33i) and beam trajectory length within the gap. Similarly, the beam trajectory length within the gap (33g) can be modified by controlling the shape of the bending (sub)unit exit (33o, 33no), so that the particle beam exits the bending (sub)unit at an angle not perpendicular to the bending (sub)unit exit (33o, 33no).

[0048] When changing the energy (Ej) of the particle beam transported within the beam transport system (30), the magnetic field (B33) of the bending unit (33) can be kept fixed, and the uniform magnetic field (B35) is controlled by changing only the current supplied to the upstream stearer (35u). This uniform magnetic field (B35) is the point through which the particle beam must reach the bending unit inlet (33i) at a desired position (Yij) in the correct orientation (entry angle (θ33i)) in order to follow a desired bending trajectory through the bending unit, and before leaving the bending unit (33) to converge toward the convergence position (330). This allows the beam transport system (30) to adapt to the beam energy (Ej) substantially more rapidly than conventional variable magnetic field bending units.

[0049] A combination of an upstream stairer (35u) and a fixed magnetic field bending unit (FFAG type) is also possible, but it is preferable to use the aforementioned bending unit (33). In fact, the present invention does not require an alternating gradient because the beam trajectory corresponding to the beam energy (Ej) is controlled by the upstream stairer. One of the advantages of the FFAG is that the particle beam is always maintained in a focused state as it sequentially passes through the three-block module of [focus-diffuse-focus] dipole. The focusing function can also be achieved, on the one hand, by controlling the profile of the magnetic field (B33) in the gap (33g) as described above, for example, by the design of the gap (33g), and / or by a quadrupole positioned upstream of the bending unit (33), and / or by the upstream stairer (35u) when an octupole is used. The aforementioned bending unit (33) is preferred because it is more compact than the FFAG.

[0050] When the bending unit (33) is formed of multiple subunits (preferably two or fewer subunits (33n)), it is preferable that the subunits (33n) are directly adjacent to each other. In some cases, a focusing element (31) or a scanner can be inserted between two bending subunits.

[0051] Similarly, as shown in Figure 3d, it is preferable that the upstream staircase (35u) is directly adjacent to the bending unit (33). However, it is also possible to insert a focusing element (31) or scanner between the upstream staircase (35u) and the bending unit (33).

[0052] Focusing element(31) A focusing element (31) is necessary to ensure the integrity of the particle beam properties when the particle beam reaches the target (11). This is especially true when using an attenuation system (37), because the interaction between the particle beam and the material block impairs the integrity of the particle beam properties. The focusing element (31) is well known to the art, and its use and function in this invention are no different from those in the prior art.

[0053] As shown in Figures 4a and 4b and 5a and 5b, the focusing element can be a quadrupole or an octupole. The quadrupole or octupole coils can be arranged at equal intervals as shown in Figures 4a and 5a, or in pairs at equal intervals as shown in Figures 4b and 5b. The latter configuration increases the tolerance for the particle beam size (along the Y-axis in the figures). By appropriately flowing current through the various coils, the generated magnetic field focuses the beam in one or both directions perpendicular to the beam trajectory.

[0054] Beam transport system (30) The most commonly used beam transport system is a gantry configured to rotate around an axis passing through the target (11), as shown in Figures 1a and 1b. However, in some cases, the beam transport system may be stationary. Instead, the target can be moved to change the orientation of the particle beam relative to the target. The present invention applies to both gantry and stationary beam transport systems.

[0055] As shown in Figure 1a, the gantry can rotate with the accelerator (20). Therefore, the particle beam does not rotate relative to the accelerator (20), which has the advantage of significantly simplifying the gantry design because it eliminates the need for a "hinge" to rotate the gantry relative to the accelerator (20).

[0056] As shown in Figure 1b, the gantry can also rotate relative to the accelerator (20). In this case, a "hinge" is required to allow rotation of the gantry with particle beams of different beam energies (Ej). The "hinge" may be provided by a second bending module formed by an upstream stairer (35u) or a downstream stairer associated with the bending unit (33). Figure 1b shows an embodiment of the second bending module with an upstream stairer (35u). The principle of the second bending module is exactly the same as that of the first bending module described above, except that while the first bending module is positioned closer to the target (11), the second bending module is positioned closer to the accelerator (20).

[0057] As shown in Figure 1b, if the accelerator is configured to emit a particle beam of a fixed exit energy, the beam transport system (30) may include a damping system (37) to absorb a predetermined percentage of the exit energy and control the beam energy (Ej) that reaches the target. Damping systems are well known in the art and may require a series of focusing elements to compensate for disturbances in the lateral beam characteristics as it passes through a material block, as well as a concrete shielding structure to hold emitted secondary particles such as neutrons. For clarity, all these elements are shown in a single box labeled (37) in Figure 1b. In the case of an accelerator configured to extract particle beams of various energies, the damping system (37) is not required, and the size of the entire beam transport system can be reduced accordingly.

[0058] Focusing elements (31) for controlling the lateral characteristics of the beam along the beam transport system (30) can be placed both upstream and downstream of the first bending module. These are well known in the art and do not need to be described further herein.

[0059] Figure 2 shows the lateral deviations of the beam trajectories (40e) and (40m) in the bending plane (Y,Z) and perpendicular to the central trajectory (40m) for beam energies E1 = 70 MeV and E3 = 225 MeV, depending on their position along the central trajectory (40m). The lateral deviation of the beam trajectory (40e) is permissible between the accelerator exit (20o) and the target (11) (neither of which are shown), as long as all of them converge to the convergence position (330) and further converge to the desired spot within the target (11). From Figure 2, it can be seen that the beam trajectories (40e) of different energies (Ej) follow substantially different beam trajectories as long as they are transported within the beam transport system (30), but they must merge when reaching the target (11). [Explanation of Symbols]

[0060] 3c coil 3p magnet pole 10 patient units 11 Target 20 Charged particle accelerators Z0o accelerator exit 30 Beam Transport System 31 Focusing element 33 Bending Unit 33c Bent Magnet Coil 33i Bending Unit Inlet 33g gap 33n bending subunit 33ni Bending subunit inlet 33no Bending subunit outlet 33° Bending unit outlet 33p Magnetic poles of the bending unit 35 Steerer 35d Downstream Steering Wheel 35u Upstream Steering Wheel 37 Damping System Magnetic field in the gap of the B33 bending unit Magnetic field within the upstream stairwell of B35 Particle beam entry position at the entrance of the Yij bending unit (X,Y) Bending plane θ33i: Entry angle of the particle beam into the bending unit entrance relative to the central orbit. θ35: Exit angle of the particle beam from the upstream stairwell relative to the central orbit.

Claims

1. A charged particle beam therapy system, - A patient unit (10) that supports the patient in a predetermined position, - An accelerator unit (20) configured to accelerate charged particles and deliver a particle beam of accelerated charged particles with an energy of 40-450 MeV / u (MeV per nucleon) from an outlet (20o), - A beam transport system (30) configured to guide a particle beam, whose energy (Ej, j=1-3) varies between 40 and 450 MeV / u, along a corresponding beam trajectory (40e) centered on a central trajectory (40m) originating from the exit (20o) of the accelerator unit (20), to a target (11) located within the patient unit (10), wherein the beam transport system (30) is configured to - A bending unit (33) having a gap (33g) between the poles (33p) of a fixed magnetic field dipole is provided, and the bending unit (33) is configured to receive the central orbit (40m) and bend the central orbit (40m) between the bending unit inlet (33i) and the bending unit outlet (33o) in a bending plane (Y, Z) at an angle of 20 to 270°, preferably 40 to 140°, in the bending plane, and the central orbit (40m) is contained within the bending plane (Y, Z), and Y⊥Z. In charged particle beam therapy systems, - The beam transport system (30) is a gantry configured to rotate the bending plane (Y, Z) around a rotation axis through which the target (11) passes. - The beam transport system (30) further comprises an upstream staircase (35u) positioned upstream of the bending unit (33), and is configured to deflect the beam trajectory (40e) at an angle (θ35) of -15 to +15° from the central trajectory (40m) within the bending plane (Y, Z), and - The upstream staircase (35u) is configured to provide a deflection function, which is obtained by generating a uniform magnetic field (B35) within the upstream staircase (35u), and the magnitude of the uniform magnetic field (B35) can be controlled to change the entry position (Yij, j=1 to 3) and entry angle (θ33i) of the beam trajectory at the bending unit inlet (33i) according to the beam energy (Ej, j=1 to 3) of the particle beam. A charged particle beam therapy system characterized by [feature].

2. A charged particle beam therapy system according to claim 1, comprising a processor configured to control the amplitude of the uniform magnetic field (B35) of the upstream stearer (35u) in accordance with the beam energy (Ej), and to control the position (Yij) and entry angle (θ33i) of the beam trajectory at the bending unit inlet (33i), thereby causing the beam trajectory (40e) to run along a curved trajectory with a bending radius corresponding to the beam energy (Ej) and pass through a convergence position (330) downstream of the bending unit outlet (33o), wherein the angle of the beam trajectory (40e) with respect to the central trajectory (40m) at the convergence position (330) preferably does not depend on the beam energy (Ej) of the particle beam.

3. A charged particle beam therapy system according to claim 2, wherein the angle of the beam trajectory (40e) at the convergence position (330) depends on the beam energy (Ej), and the beam transport system (30) comprises a downstream stairer (35d) positioned at the convergence position (330) and configured to deviate the beam trajectory to a common beam trajectory without depending on the beam energy (Ej).

4. A charged particle beam therapy system according to any one of claims 1 to 3, wherein the bending unit (33) comprises one or more bending subunits (33n) arranged along the beam trajectory, and each bending subunit (33n) comprises a gap (33g) that extends along a curved shape on the bending plane (Y, Z) from a subunit inlet (33i) to a subunit outlet (33no), and the gap (33g) separates first and second magnet coils (33c) positioned symmetrically on both sides of the bending plane. - The first and second magnet coils (33c) each surround the first and second magnet poles (33p) made of ferromagnetic material, or The first and second magnet coils (33c) are made of superconducting material. A charged particle beam therapy system characterized by the following features.

5. In the charged particle beam therapy system according to claim 4, the gap (33g) is as follows: - In a plane parallel to the bending plane (Y, Z), the gap (33g) defines a bend centered on the central track (40m) and enclosed between a near wall (33gc) with a small radius of curvature (R1) and a far wall with a large radius of curvature (R2) (R1 < R2), where the distance separating the near wall and the far wall (hi, ho) is greater on the inlet (33i) side of the bending unit of the gap (33g) than on the outlet (33o) side. - The width (w1, w2) of the gap (33g) measured parallel to the X-axis perpendicular to the bending plane (i.e., X⊥Y⊥Z) is greater on the near wall side than on the far wall side (w1 > w2). A charged particle beam therapy system characterized by being defined as follows.

6. A charged particle beam therapy system according to any one of claims 1 to 5, characterized in that the magnetic field (B33) in the gap (33g) of each bending subunit (33n) shows a maximum value in the region adjacent to the far wall and a minimum value in the region adjacent to the near wall.

7. In the charged particle beam therapy system according to claim 6, the maximum value of the magnetic field (B33) in the gap (33g) of each bending subunit (33n) is - When the first and second magnet coils (33c) surround the first and second magnet poles (33p) made of ferromagnetic material, the T is between 1.5T and 2.6T, preferably between 1.9T and 2.4T, or - When the first and second magnet coils (33c) are superconducting, the T is between 2.5T and 9T, preferably between 3.5T and 6T. A charged particle beam therapy system characterized by the following features.

8. A charged particle beam therapy system according to any one of claims 4 to 7, characterized in that the subunit inlet (33i) and / or subunit outlet (33o) of at least one bending subunit of the bending unit (33) are not perpendicular to the central trajectory (40m).

9. A charged particle beam therapy system according to any one of claims 1 to 8, characterized in that the particles are selected from hadrons, preferably from protons, carbon ions, helium ions, and oxygen ions.

10. In the charged particle beam therapy system according to any one of claims 1 to 9, the upstream stearer (35u) is as follows: - A dipole configured to provide only deviation functionality, or A dipole configured to provide a deviation function and a 1D scanning function configured to scan the beam trajectory in one direction across the beam trajectory to enable scanning of the target, ・It is an octupole, and has a deviant function, o A focusing function configured to reduce the size of the particle beam cross-section in one or two directions across the beam trajectory, and / or o A 1D or 2D scanning function configured to scan the beam trajectory in one or two directions across the beam trajectory in order to enable scanning of the target (11), A bajizi configured to provide, A charged particle beam therapy system characterized by being one of the following.

11. In the charged particle beam therapy system according to any one of claims 1 to 10, the beam transport system (30) is - One or more focusing elements (31) for focusing the accelerating beam along the central trajectory (40 m) and in a cross-sectional plane (X, Y) perpendicular to the central trajectory (40 m), Preferably, a scanner for deflecting the beam trajectory at an angle of -15° to +15° in a direction perpendicular to the central trajectory (40m), wherein the scanner is configured to control the beam trajectory in order to scan over the target (11). A charged particle beam therapy system characterized by comprising the following features.

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