Proton therapy facility for treating a patient using proton radiation

Abstract

Proton therapy system (1) for treating a patient (2) by means of proton radiation (3), comprising a particle accelerator (4) for generating a proton beam, a movable patient table (5) for holding and positioning a patient (2), a beam guidance device comprising several electromagnets (6) for focusing and / or defocusing and / or deflecting the proton beam (3), and a gantry (7) rotatable about a horizontal axis of rotation (R) for directing the proton beam (3) onto a target volume within a patient (2) held on the patient table (5), wherein the proton beam (3) has a maximum energy of less than 180 MeV, and the beam guidance device comprising a first scanner magnet (8A) and a second scanner magnet (8B) arranged in the direction of the proton beam behind the first scanner magnet (8A) for deflecting the proton beam (3), as well as a Proton beam direction between the scanner magnets (8A,8B) has a deflection magnet (9) arranged, wherein the deflection magnet (9) is configured to focus the proton beam (3) at the magnet input (9.1) in the plane of the beam deflection by the first scanner magnet (8A).

Description

[0001] The invention relates to a proton therapy system for treating a patient using proton radiation, comprising a particle accelerator for generating a proton beam, a movable patient table for holding and positioning a patient, a beam guidance device having several electromagnets for focusing and / or defocusing and / or deflecting the proton beam, and a gantry rotatable about a horizontal axis of rotation for directing the proton beam onto a target volume within a patient held on the patient table.

[0002] Proton beam therapy is a modern, precise form of radiation therapy for treating cancer, recognized by health insurance companies. Due to its physical properties, proton therapy is considered particularly gentle and effective. In this procedure, protons are accelerated in an accelerator and directed as a proton beam at the patient or a target volume. As they penetrate the body, the protons decelerate. The energy loss of protons increases continuously with path length until reaching the so-called Bragg peak, at which point it drops to approximately zero. This results in the characteristic depth-dose curve for protons, with the Bragg peak at its end, where the dose is delivered to the irradiated tissue in a highly concentrated and localized manner.This effect is used in proton therapy for the localized irradiation of tumors, allowing for optimal protection of surrounding tissue, as the energy of the protons and the corresponding dose can be delivered very precisely to the target volume. Overall, this can improve the chances of a cure and reduce side effects.

[0003] Conventional proton therapy facilities, however, are associated with very high investment costs, often in the hundreds of millions. These high costs result firstly from the cost of the components and the effort required for their integration and commissioning. Secondly, the stringent radiation protection requirements associated with the use of protons accelerated to corresponding energies lead to costly construction measures. Additionally, the space required for the accelerator and beam delivery technology is very large. Facilities with multiple treatment rooms and gantries have a footprint of several thousand square meters and extend over several floors. These factors—the high costs and the considerable space requirements—are the reasons for the limited accessibility of the treatment methods available with modern proton therapy facilities. For example, only five proton or...Ion therapy facilities, but more than 200 conventional radiotherapy facilities are operated in Germany.

[0004] When the term "conventional radiotherapy facility" is used, it refers to a conventional X-ray and / or electron beam-based radiotherapy facility for therapy with photon or X-ray radiation and / or electron radiation.

[0005] The proton therapy systems known from the state of the art do not yet allow for increasing the attractiveness of proton therapy systems and thus increasing the spread or accessibility of this treatment method.

[0006] Based on this, the object of the invention is to provide a proton therapy system for proton therapy which, due to reduced costs and lower space requirements than conventional proton therapy systems, increases the accessibility of these systems and thus the accessibility of proton therapy.

[0007] This problem is solved by the subject matter of claim 1. Preferred embodiments are found in the dependent claims.

[0008] According to the invention, a proton therapy system for treating a patient using proton radiation is provided, comprising a particle accelerator for generating a proton beam, a movable patient table for holding and positioning a patient, a beam guidance device having several electromagnets for focusing and / or defocusing and / or deflecting the proton beam, and a gantry rotatable about a horizontal axis of rotation for directing the proton beam onto a target volume within a patient held on the patient table, wherein the proton beam has a maximum energy of less than 180 MeV.

[0009] When the term "maximum energy" is used here, it refers to the maximum energy for which the system and its components are suitable and which can be generated in the particle accelerator. Preferably, the proton beam has a maximum energy between 130 MeV and 160 MeV, and most preferably between 130 MeV and 150 MeV.

[0010] The maximum energy is therefore so low that it is only suitable for treatments where a proton beam range of no more than 21.7 cm in water is sufficient to target the volume. A target volume is considered targetable if a predetermined radiation dose, for example, 50 Gy, targets a predetermined volume fraction of the target volume, for example, 95% of the target volume. The specific values ​​or fractions are defined in guidelines and depend on the specific therapeutic goal.

[0011] Therefore, this radiotherapy system is only suitable for treatments where the advantages of proton beam therapy over X-ray or electron beam therapy are particularly pronounced. This advantage lies in the so-called dose conformity, which is determined by the rapid distal and lateral falloff of the dose distribution in the tissue. This allows the radiation dose to be concentrated very effectively on the tumor. At higher proton beam energies, especially above 180 MeV, both the distal and lateral falloff increase significantly, thus considerably reducing this advantage. With reduced proton beam energy, the range in water, and therefore the achievable penetration depth, is significantly smaller, meaning that deeper target volumes cannot be reached.For applications where the available maximum proton energy is insufficient to irradiate the entire target volume, a combination of proton radiation treatments with photon or electron radiation, or an exclusively alternative treatment using photon or electron radiation, is particularly necessary to achieve the therapeutic goals.

[0012] A key aspect of the invention is that the maximum proton beam energy is less than 180 MeV, and that this reduced energy allows for the construction of significantly more compact and cost-effective proton therapy systems compared to existing systems. A lower maximum proton beam energy means that the particle accelerator, as well as the electromagnets and gantries, can be manufactured smaller and more cost-effectively overall. Furthermore, with reduced energy, radiation losses in a cyclotron / degrader-based system, and thus the emission of unwanted secondary radiation, are significantly reduced. This means that the facilities housing the system require considerably less shielding, further reducing construction costs.

[0013] Another aspect of the invention is that the reduced maximum proton beam energy across the entire energy range at the irradiation point enables significantly higher beam intensities and thus shorter irradiation times, particularly in cyclotron-based proton therapy systems. Furthermore, this has the advantageous effect of eliminating the need for an energy filter. An energy filter reduces the distal falloff of the dose distribution, which is a significant advantage of proton irradiation over conventional radiation therapy. At low beam energies, the distal falloff is already so minimal that it does not require further reduction by an energy filter. This allows the proton therapy system to be designed to be smaller and more cost-effective.

[0014] According to a preferred embodiment of the invention, the beam guidance device comprises a first scanner magnet and a second scanner magnet arranged downstream of the first scanner magnet in the proton beam direction for deflecting the proton beam, as well as a deflection magnet arranged between the scanner magnets in the proton beam direction. The deflection magnet is configured to focus the proton beam at the magnet input in the plane of beam deflection by the first scanner magnet. The deflection magnet, located last in the proton beam direction, thus focuses the proton beam at the magnet input after the proton beam has been deflected by the first scanner magnet. At the magnet output of the deflection magnet, the proton beam can preferably be further focused or defocused, depending on the optimal beam-optical solution, before the proton beam is deflected by the last scanner magnet in the proton beam direction to scan the target volume.This is made possible in particular by the use of focusing and defocusing edge fields. This allows the deflection of the proton beam by the scanner magnet within the deflection magnet, and thus the volume of the deflection magnet, to be limited. The last deflection magnet on the gantry in the direction of the proton beam remains cost-effective, even though a scanner magnet is positioned in front of it in the direction of the proton beam.

[0015] According to a preferred embodiment of the invention, the beam guidance device is configured to deflect the proton beam for an irradiation field with a first maximum side length a and a second maximum side length b, wherein the side lengths a and b are each either 20 cm, 15 cm, 10 cm, or 5 cm. Preferably, the side lengths a and b are each less than 20 cm, more preferably less than 15 cm, more preferably less than 10 cm, and most preferably less than 5 cm. In this way, the maximum irradiation field of 30 cm × 40 cm, which is common in many conventional systems today, is significantly reduced, for example, to an irradiation field of 20 cm × 10 cm, 10 cm × 10 cm, or 10 cm × 5 cm. In order to be able to cover larger areas, it is particularly provided that several irradiation fields are arranged in a row.The proton beams are emitted sequentially (automatic sequencing) using field patching. Because the proton beam requires a shorter deflection to reach the smaller irradiation field, smaller scanner magnets and lower-powered power supplies can be used, resulting in further cost savings. The reduced deflection angles also allow scanning through the last deflection magnet of the gantry without requiring a significantly larger and more expensive magnet. This allows for a reduction in the gantry radius and, consequently, its overall size.

[0016] According to a preferred embodiment of the invention, the patient table comprises a continuously movable motion device supporting the patient table and a control unit controlling the motion device. The motion device is configured to move the patient table along three translational axes and to rotate it about three rotational axes. The control unit enables automated control of the motion device, allowing the patient table to be moved to a predetermined position without manual intervention or operation. In this way, a particularly flexible 6-axis movement of the patient table along three translational and three rotational axes can be achieved.

[0017] According to a preferred embodiment of the invention, the control device is designed to move the patient table relative to the gantry such that a defined irradiation center within the patient is also rotated around the gantry's axis of rotation. Conventional gantries are rotated isocentrically in both conventional radiotherapy and proton therapy. This means that the irradiation center (isocenter) is located on the gantry's axis of rotation. Small isocentric gantries have the disadvantage that the distance between the gantry or radiation head and the irradiation center also becomes small. This leads, firstly, to a reduction in the clearance in front of the patient and, secondly, to a deterioration of the ratio of the surface dose to the dose in the tumor tissue.These disadvantages are avoided, in particular, by positioning the treatment center further away from the last scanner magnet and not on the axis of rotation. To maintain the distance to the last scanner magnet at different gantry rotation angles, the patient table, or the patient and the treatment center, must also be moved around the axis of rotation when the gantry rotates. The gantry rotation is therefore non-isocentric. The table position relative to the gantry rotation is preferably calculated automatically using an algorithm and controlled by the control unit, so that treatment plans that call for isocentric gantry rotation can also be implemented with the smaller proton therapy system with non-isocentric gantry rotation.The automated tracking of the patient table also enables gantry-based imaging systems, which can thus be firmly aligned with the moving radiation treatment center.

[0018] According to a preferred embodiment of the invention, the control device is designed to move the patient table while maintaining a constant distance between the second scanner magnet and the irradiation center (source-axis distance, SAD) even with changing gantry rotation angles. The irradiation plans are conventionally created for constant SADs. This ensures the compatibility of the miniaturized proton therapy system with conventional irradiation plans and also enables the use of gantry-based imaging devices.

[0019] According to a preferred embodiment of the invention, the gantry comprises a dynamic support device that allows an additional, unintentional movement of the gantry beyond its rotation about the axis of rotation, and the beam guidance device includes at least one corrective magnet for correcting the deflection of the proton beam and compensating for the movements of the gantry. The term "support device" refers to the gantry structure to which parts of the beam guidance device are attached and via which both the gantry itself and the beam guidance device can be rotated about the axis of rotation. When a "dynamic support device" is mentioned here, it is the opposite of a rigid support device. Normally, the gantry structures of a proton therapy system are deliberately designed to be rigid in order to minimize the effects of bending on the beam guidance.This requires steel structures weighing many tons and incurring significant costs. If dynamic support devices are used instead, gravitational loads lead to unintended movement of the gantry. "Unintended movement" is defined as a reproducible movement of the support device or a reproducible bending of the gantry structure that is unintentional but whose existence is known. The effect of this unintended movement of the support device on the proton beam is compensated for by actively tracking the magnetic beam guidance using a suitable model. The deflection of the proton beam is thus adjusted and corrected to match the movement of the support device. This correction is achieved electromagnetically using the correction magnet(s).In this way, the otherwise multi-ton and costly rigid support device can be manufactured with less weight and at lower cost, and the required positional accuracy can still be guaranteed with minimal technical effort.

[0020] According to a preferred embodiment of the invention, the proton therapy system is designed to position the patient for a spatially adjacent conventional radiotherapy system by moving the patient table and / or the movement device. When "spatially adjacent" is mentioned here, it means that the radiotherapy systems are arranged side by side in the same room. The gantry is installed, in particular, spatially adjacent to a conventional linear accelerator, with both systems sharing a common patient table for patient positioning. Preferably, only one of the two systems has an imaging system for verifying the patient's position, which can be used for both systems.

[0021] According to a preferred embodiment of the invention, the gantry has a mounting device for attaching a linear accelerator included in the conventional radiotherapy system. For this purpose, the gantry particularly has an additional arm on which a linear accelerator for conventional radiotherapy can be installed. In this way, the proton therapy system and the conventional radiotherapy system are connected, thus ensuring cross-therapy treatment with the same patient positioning.

[0022] The proton therapy system according to the invention is suitable not only for use as a single-room system but also for multiple treatment rooms with a single particle accelerator and one gantry and one patient table per treatment room. The proton beam is then deflected from the particle accelerator to the different treatment rooms via the beam guidance device.

[0023] The invention also provides for the use of a proton therapy system described above for treating a patient with proton therapy as a complement to conventional radiotherapy. In this way, the disadvantages already discussed, namely the reduced maximum proton energy of a smaller and more cost-effective proton therapy system, can be compensated for by the complementary treatment with conventional radiotherapy within a combined treatment approach. Furthermore, this avoids the common problem with conventional proton therapy systems, namely that, unlike conventional radiotherapy systems, the number of referred patients is too low for the system to operate economically. Economical operation is, however, ensured when the proton therapy system is combined with the conventional radiotherapy system.

[0024] The invention will now be explained in more detail with reference to the drawings and a preferred embodiment.

[0025] The drawings show Fig. 1 Schematic representation of a proton therapy system according to a preferred embodiment of the invention in a perspective view, Fig. 2 schematically a proton therapy system according to a further preferred embodiment of the invention in a perspective view.

[0026] Out of Fig. Figure 1 schematically shows a proton therapy system 1 according to a preferred embodiment of the invention in a perspective view. The proton therapy system 1 comprises a particle accelerator 4, in which a proton-emitting proton source is located and which accelerates the protons. The resulting proton beam 3 is guided by the particle accelerator 4 via a beam guidance device and directed to the irradiation site by means of several electromagnets 6 in the form of so-called dipole or quadrupole magnets. The last electromagnet in the direction of the proton beam is the last deflection magnet 9. The maximum energy is reduced to the desired energy by means of an energy reduction system 18. The energy reduction system 18, the so-called degrader, is placed in the beam path so that the protons pass through a braking plate or braking wedges, for example made of carbon, and are decelerated to the desired energy.The beam guidance system also includes two scanner magnets 8A and 8B, which deflect the proton beam in two directions perpendicular to each other. The first scanner magnet 8A deflects the proton beam 3 in the Y direction, and the second scanner magnet 8B deflects the proton beam 3 in the X direction. The last deflection magnet 9, located in the direction of the proton beam, is positioned between the scanner magnets 8A and 8B. The proton beam 3 is therefore first deflected in the Y direction by the first scanner magnet 8A, then focused and deflected at the magnet input 9.1 of the last deflection magnet 9, and finally aligned at the magnet output 9.2 in the Y direction onto the point to be irradiated. Subsequently, the proton beam 3 is deflected in the X direction by the second scanner magnet 8B.In this way, the last deflection magnet 9 can have a small volume, even though the proton beam 3 has already been deflected by the scanner magnet 8A, and thus remains cost-effective overall.

[0027] Patient 2 is positioned on a patient table 5, which can be continuously moved in all three spatial directions along three translational axes and rotated about three rotational axes—the longitudinal, transverse, and sagittal axes of patient 2—by means of the motion device 10, which is a robotic arm. The gantry 7 is rotatable about the rotational axis R. Because the radiation treatment center 11 is not located on the rotational axis R, the gantry rotation is non-isocentric. This means that during gantry rotation, the patient table 5, or rather the radiation treatment center 11, also rotates about the rotational axis R. The table movement about the rotational axis R is such that the distance between the radiation treatment center 11 and the second scanner magnet 8B remains constant. The correction magnet 15 guides the proton beam 3, preventing unintended but reproducible deformations or bending of the Fig. 1 dynamic support device 14 not shown can be compensated.

[0028] Fig.Figure 2 shows a proton therapy system 1 according to a further preferred embodiment of the invention in a perspective view. The proton therapy system 1 according to the invention is combined with a linear accelerator 17 of a conventional radiotherapy system 13. The beam delivery device is attached to a dynamic support device 14. The support device 14 additionally has a mounting option 16 for the linear accelerator 17. In this way, a patient 2 can be treated with both proton radiation and photon or electron radiation in the same treatment session without the patient 2 having to change treatment rooms or be repositioned. Thus, the significantly more advantageous proton therapy can be used for a large proportion of tumors with the small and cost-effective proton therapy system 1.In such cases, where the limits of the small proton therapy system 1 are reached and adequate treatment of the tumor is not possible with the small proton therapy system, photon or electron radiation can be used without any loss in the quality of treatment or failure to achieve therapeutic goals. Reference symbol list 1 proton therapy unit 2 patients 3 proton beam 4 particle accelerators 5 patient tables 6 Electromagnet 7 Gantry 8A, 8B Scanner magnet 9 last deflection magnet 9.1 Magnetic input 9.2 Magnetic output 10 Motion device 11 Radiation Center 12 Control unit 13 conventional radiotherapy facilities 14 dynamic support device 15 Correction magnet 16 Fastening device 17 linear accelerators 18 Energy Reduction System R axis of rotation

Claims

[1] Proton therapy facility (1) for treating a patient (2) by means of proton radiation (3), comprising a particle accelerator (4) for generating a proton beam, a movable patient table (5) for storing and positioning a patient (2), a beam guidance device comprising several electromagnets (6) for focusing and / or defocusing and / or deflecting the proton beam (3) and a gantry (7) rotatable about a horizontal axis of rotation (R) for directing the proton beam (3) onto a target volume within a patient (2) positioned on the patient table (5), wherein the proton beam (3) has a maximum energy of less than 180 MeV. [2] Proton therapy system (1) according to claim 1, wherein the beam guidance device comprises a first scanner magnet (8A) and a second scanner magnet (8B) arranged in the proton beam direction behind the first scanner magnet (8A) for deflecting the proton beam (3) and a deflection magnet (9) arranged in the proton beam direction between the scanner magnets (8A, 8B), wherein the deflection magnet (9) is configured to focus the proton beam (3) at the magnet input (9.1) in the plane of beam deflection by the first scanner magnet (8A). [3] Proton therapy system (1) according to claim 1 or 2, wherein the beam guidance device is configured to deflect the proton beam (3) for an irradiation field with a first maximum side length a and a second maximum side length b, wherein the side lengths a and b are each either 20 cm, 15 cm, 10 cm or 5 cm. [4] Proton therapy system (1) according to one of the preceding claims, wherein the patient table (5) has a motion device (10) supporting the patient table (5) and continuously movable, and a control unit (12) controlling the motion device (10), wherein the motion device (10) is designed to move the patient table (5) along three translation axes and to rotate it about three rotation axes. [5] Proton therapy system (1) according to claim 4, wherein the control unit (12) is configured to move the patient table (5) relative to the gantry (7) such that a radiation center (11) defined in the patient (2) is also rotated around the axis of rotation (R) of the gantry (7). [6] Proton therapy system (1) according to claims 2 and 5, wherein the control unit (12) is configured to move the patient table (5) at a constant distance between the second scanner magnet (8B) and the irradiation center (11). [7] Proton therapy system (1) according to any one of the preceding claims, wherein the gantry (7) comprises a dynamic support device (14) which allows an additional unintended movement by deformation of the gantry (7) beyond the rotation about the axis of rotation (R), and the beam guidance device has at least one correction magnet (15) for correcting the deflection of the proton beam (3) and compensating for the effects of the movement of the gantry (7) on the proton beam (3). [8] Proton therapy system (1) according to one of the preceding claims, wherein the proton therapy system (1) is configured to provide the patient (2) for a spatially adjacent conventional radiotherapy system (13) by moving the patient table (5) and / or the movement device (10). [9] Proton therapy system (1) according to one of the preceding claims, wherein the gantry (7) has a fastening device (16) for fastening a linear accelerator (17) comprised by the conventional proton therapy system (13). [10] Use of a proton therapy system (1) according to any of the preceding claims for treating a patient (2) by means of proton therapy as a supplement to treatment of the patient by means of conventional radiotherapy.

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