DE102022115598A1 - Proton therapy system for treating a patient using proton radiation - Google Patents

Abstract

The invention relates to a proton therapy system (1) for treating a patient (2) using proton radiation (3), comprising a particle accelerator (4) for generating a proton beam, a movable patient table (5) for supporting and positioning a patient (2), and several Beam guiding device having electromagnets (6) for focusing and/or defocusing and/or deflecting the proton beam (3) and a gantry (7) which can be rotated about a horizontal axis of rotation (R) for directing the proton beam (3) onto a target volume within one on the patient table (5) stored patient (2), the proton beam (3) having a maximum energy of less than 180 MeV. This makes it possible to increase the accessibility of these systems and thus the accessibility of proton therapy due to reduced costs and a smaller space requirement than with conventional proton therapy systems.

Description

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 supporting and positioning a patient, a beam guidance device having a plurality of electromagnets for focusing and / or defocusing and / or deflecting the proton beam and a a horizontal axis of rotation rotatable gantry for directing the proton beam to a target volume within a patient positioned on the patient table.

The treatment of patients using proton radiation is a modern, precise form of radiation therapy for the treatment of cancer that is recognized by health insurance companies. Proton therapy is considered particularly gentle and effective due to its physical properties. Protons are accelerated in an accelerator and directed as a proton beam onto a patient or a target volume. When they enter the body, the protons are slowed down. For protons, the energy loss increases continuously with path length up to the so-called Bragg peak and falls to approximately zero. This results in the depth dose curve characteristic of protons with the Bragg peak at the end, in which the dose is delivered to the irradiated tissue in a particularly concentrated and localized manner. This effect is exploited in proton therapy for localized irradiation of tumors and enables optimal protection of the surrounding tissue, as the energy of the protons and the associated dose can be introduced very precisely into the target volume. Overall, the chances of recovery can be improved and side effects reduced.

However, conventional proton therapy systems are associated with very high investment costs, often in the three-digit million range. These high costs arise, firstly, from the costs of the components and the effort required for their integration and commissioning. Secondly, the high demands on radiation protection associated with the use of protons accelerated to appropriate energies lead to cost-intensive structural measures. In addition, the space required for the accelerator and beam guidance technology is very high. Facilities with several treatment rooms and gantries have a floor area of several thousand square meters and extend over several floors. These factors, i.e. the high costs and the considerable space requirement, are reasons for the only moderate accessibility to the treatment methods that are available with modern proton therapy systems. For example, only five proton or ion therapy systems, but more than 200 conventional radiation therapy systems, are operated in Germany.

If the term “conventional radiation therapy system” is used here, this means a conventional X-ray and/or electron beam-based radiation therapy system for therapy with photon or X-ray radiation and/or electron radiation.

The proton therapy systems known from the prior art do not yet make it possible to increase the attractiveness of proton therapy systems and thus increase the spread or accessibility of this treatment method.

Proceeding from this, the object of the invention is to provide a proton therapy system for proton therapy, which increases the accessibility of these systems and thus the accessibility of proton therapy due to reduced costs and a smaller space requirement than conventional proton therapy systems.

This task is solved by the subject matter of patent claim 1. Preferred further training can be found in the subclaims.

According to the invention, a proton therapy system for treating a patient using proton radiation is therefore provided, which has a particle accelerator for generating a proton beam, a movable patient table for supporting and positioning a patient, a beam guidance device having a plurality of electromagnets for focusing and / or defocusing and / or deflecting the proton beam and a comprises a gantry rotatable about a horizontal axis of rotation for directing the proton beam to a target volume within a patient stored on the patient table, the proton beam having a maximum energy of less than 180 MeV.

When we talk about “maximum energy” in this case, this means the maximum energy for which the system and its components are suitable and which can be generated in the particle accelerator. The proton beam preferably has a maximum energy between 130 MeV and 160 MeV, most preferably between 130 MeV and 150 MeV.

The maximum energy is therefore so low that it is only suitable for treatments in which a range of the proton beam in water of a maximum of 21.7 cm is sufficient to reach the target to capture volume. A target volume can be detected when a predetermined radiation dose, for example 50 Gy, detects or can detect a predetermined volume fraction of the target volume, for example 95% of the target volume. The respective values or proportions are specified in guidelines and depend on the respective therapy goal.

The radiotherapy system is therefore only suitable for irradiation in which the advantages of proton irradiation compared to X-ray or electron irradiation are particularly evident. This advantage lies in the so-called dose conformity, which is determined by the rapid distal fall and the lateral fall of the dose distribution in the tissue. This allows the radiation dose to be concentrated particularly well on the tumor. At higher proton beam energies, particularly greater than 180 MeV, both the distal and lateral drops increase significantly, significantly reducing this advantage. With reduced proton beam energy, the range in water and thus the achievable penetration depth is significantly smaller, so that deeper target volumes cannot be reached. For applications in which the available maximum proton energy is not sufficient to irradiate the entire target volume, a combination of treatments using proton radiation with photon or electron radiation or an exclusive alternative treatment using photon or electron radiation is required to achieve the therapy goals.

It is therefore a crucial point of the invention that the maximum proton beam energy is less than 180 MeV and that the reduced energy allows the production of significantly more compact and cost-effective proton therapy systems compared to existing systems. A low maximum proton beam energy means that both the particle accelerator and the electromagnets and gantries can be manufactured smaller and more cost-effectively. In addition, with reduced energy, the radiation losses in a cyclotron/degrader-based system and thus the emission of unwanted secondary radiation are significantly reduced. As a result, the rooms to accommodate the system require significantly less shielding and construction costs are further reduced.

A further aspect of the invention is that with the reduced maximum proton beam energy in the entire energy range at the irradiation point, particularly in cyclotron-based proton therapy systems, significantly higher beam intensities and thus shorter irradiation durations are made possible. This also has the advantageous effect of eliminating the need for an energy filter. An energy filter reduces the distal drop in dose distribution, which is a significant advantage of proton irradiation over conventional irradiation. At low beam energies, the distal drop is already so small that it does not need to be further reduced by an energy filter. In this way, the proton therapy system can be made smaller and more cost-effective.

According to a preferred development of the invention, the beam guidance device has a first scanner magnet and a second scanner magnet arranged behind the first scanner magnet in the proton beam direction for deflecting the proton beam and a deflection magnet arranged between the scanner magnets in the proton beam direction, the deflection magnet for this purpose is designed to focus the proton beam at the magnet input in the plane of beam deflection by the first scanner magnet. The last deflection magnet in the proton beam direction therefore focuses the proton beam at the magnet input after the proton beam has been deflected by the first scanner magnet. At the magnetic output of the deflection magnet, the proton beam can preferably be additionally focused or defocused, depending on the best 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 or defocusing edge fields. This allows the deflection of the proton beam by the scanner magnet in the deflection magnet and thus the volume of the deflection magnet to be limited. The last deflection magnet on the gantry in the proton beam direction remains inexpensive, although a scanner magnet is placed in front of it in the proton beam direction.

According to a preferred development of the invention, the beam guidance device is designed to deflect the proton beam for an irradiation field with a first maximum side length a and a second maximum side length b, the side lengths a and b each being either 20 cm, 15 cm, 10 cm or 5 cm be. Preferably, the side lengths a and b each have a length of less than 20 cm, preferably less than 15 cm, particularly preferably less than 10 cm and most preferably less than 5 cm. In this way, the maximum irradiation field of 30 cm × 40 cm that 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 to an irradiation field of 10 cm × 5 cm. In order to be able to cover larger areas, it is in particular intended that several Irradiation fields are strung together (field patching) and automatically emitted one after the other (automatic sequencing). Since the proton beam does not have to be deflected as far to reach the reduced irradiation field, smaller scanner magnets and power supplies with lower power can be used, thus saving further costs. The reduced deflection angles also make it possible to scan through the last deflection magnet of the gantry without having to make this magnet much larger and more expensive. This allows the gantry radius and thus the size of the gantry to be reduced.

According to a preferred development of the invention, the patient table has a movement device that supports the patient table and is infinitely movable and a control unit that controls the movement device, the movement device being designed to move the patient table along three translation axes and to rotate it about three rotation axes. The control unit enables automated control of the movement device so that the patient table can be moved to a predetermined position without manual intervention or operation. In this way, a particularly flexible 6-axis movement of the patient table can take place along three translation axes and around three rotation axes.

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

According to a preferred development of the invention, the control device is designed to move the patient table with changed gantry rotation angles with a constant distance between the second scanner magnet and the irradiation center (source-axis-distance, SAD). The treatment plans are traditionally created for constant SADs. This ensures compatibility of the scaled-down proton therapy system with conventional radiation plans and also enables the use of gantry-based imaging devices.

According to a preferred development of the invention, the gantry comprises a dynamic support device which allows unintentional movement of the gantry in addition to the rotation about the axis of rotation, and the beam guidance device has at least one correction magnet for correcting the deflection of the proton beam and compensating for the movements of the gantry. “Support device” is understood to mean the gantry construction 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. If we are talking about a “dynamic support device” here, we mean the opposite of a rigid support device. Normally, the gantry designs of a proton therapy system are deliberately designed to be rigid in order to minimize the effects of bending on the beam delivery. This requires cost-intensive steel structures weighing tons. If dynamic support devices are used instead, the gravitational loads will cause the gantry to move unintentionally. “Accidental movement” is understood to mean a reproducible movement of the support device or a reproducible bending of the gantry construction that is not intended but whose existence is known. The effect of the unintentional movement of the support device on the proton beam is compensated for using a suitable model by actively tracking the magnetic beam guidance. The deflection of the proton beam is therefore adapted to the movement of the support device and corrected greedy. The correction is carried out electromagnetically by means of the correction magnet(s). In this way, the rigid support device, which otherwise weighs tons and is expensive, can be manufactured with less weight and with less cost, and the required positioning accuracy can still be guaranteed with little technical effort.

According to a preferred development of the invention, the proton therapy system is designed to make the patient available for a spatially adjacent conventional radiation therapy system by moving the patient table and/or the movement device. If the term “spatially adjacent” is used here, this means an arrangement of the radiotherapy systems next to each other in the same room. In particular, the gantry is installed spatially adjacent to a conventional linear accelerator, with both systems sharing a common patient table for positioning the patient. It is preferably provided that only one of the two systems has an imaging system for verifying the patient position, which can be used for both systems.

According to a preferred development of the invention, the gantry has a fastening device for fastening a linear accelerator included in the conventional radiation therapy system. For this purpose, the gantry in particular has an additional arm on which a linear accelerator for conventional radiation therapy can be installed. In this way, the proton therapy system and the conventional radiation therapy system are connected to each other, ensuring cross-therapy treatment with the same patient positioning.

In addition to being designed as a one-room system, the proton therapy system according to the invention is also suitable for several 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 into the different treatment rooms via the beam guidance device.

According to the invention, the use of a proton therapy system described above for treating a patient using proton therapy is also provided as a supplement to treatment of the patient using conventional radiation therapy. In this way, the disadvantages already explained in the reduced maximum proton energy of a smaller and more cost-effective proton therapy system can be compensated for by the supplementary treatment using conventional radiation therapy as part of a joint treatment. In addition, this avoids the common problem with conventional proton therapy systems that, unlike conventional radiotherapy systems, the number of patients referred is too small for economical operation of conventional proton therapy systems. However, economical operation is guaranteed if the proton therapy system is combined with the conventional radiation therapy system.

The invention is explained in further detail below using a preferred exemplary embodiment with reference to the drawings.

• 1 schematisch eine Protonentherapieanlage gemäß einem bevorzugten Ausführungsbeispiel der Erfindung in einer perspektivischen Ansicht,
• 2 schematisch eine Protonentherapieanlage gemäß einem weiteren bevorzugten Ausführungsbeispiel der Erfindung in einer perspektivischen Ansicht.

Show in the drawings

• 1 schematically a proton therapy system according to a preferred embodiment of the invention in a perspective view,
• 2 schematically a proton therapy system according to a further preferred embodiment of the invention in a perspective view.

Out of 1 A proton therapy system 1 according to a preferred embodiment of the invention can be seen schematically in a perspective view. The proton therapy system 1 includes a particle accelerator 4, in which there is a proton source that emits protons and which accelerates the protons. The resulting proton beam 3 is guided by the particle accelerator 4 via a beam guidance device and guided 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 proton beam direction is the last deflection magnet 9. The maximum energy is reduced to the desired energy using the energy reduction system 18. The energy reduction system 18, the so-called degrader, is brought into the beam path so that the protons pass through a brake plate or brake wedges, for example made of carbon, and are braked to the desired energy. The beam guidance device also includes two scanner magnets 8A, 8B, which deflect the proton beam in two mutually perpendicular directions. 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 in the proton beam direction is arranged between the scanner magnets 8A, 8B. The proton beam 3 is therefore first deflected in the Y direction by means of the first scanner magnet 8A, then at the magnet input 9.1 of the last deflection magnet 9 is focused, deflected and finally aligned at the magnet output 9.2 in the Y direction to the point to be irradiated. The proton beam 3 is then 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 therefore remains cost-effective overall.

The patient 2 is positioned on a patient table 5, which can be continuously moved in all three spatial directions along three translation axes and rotated about three axes of rotation, i.e. about the longitudinal, transverse and sagittal axes of the patient 2, by means of the movement device 10 in the form of a robot arm. The gantry 7 can be rotated around the rotation axis R. Because the irradiation center 11 is not arranged on the rotation axis R, the gantry rotation occurs non-isocentrically. This means that during a gantry rotation, the patient table 5 or the irradiation center 11 is also rotated about the rotation axis R. The table moves about the axis of rotation R in such a way that the distance between the irradiation center 11 and the second scanner magnet 8B remains constant. The correction magnet 15 tracks the proton beam 3, so that unintentional but reproducible deformations or bends of the in 1 dynamic support device 14, not shown, can be compensated for.

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 radiation therapy system 13. The beam guidance device is attached to a dynamic support device 14. The support device 14 additionally has a fastening option 16 for the linear accelerator 17. In this way, a patient 2 can be treated using both proton radiation and photon or electron radiation in the same treatment session, without the patient 2 having to change the treatment room or be repositioned. In this way, a large proportion of tumors can be treated with significantly more advantageous proton therapy using the small and inexpensive proton therapy system 1. In cases in which the limits of the small proton therapy system 1 are reached and the tumor cannot be adequately treated with the small proton therapy system, photon or electron radiation can be used without sacrificing the quality of the treatment or failing to achieve therapeutic goals become.

Reference symbol list

1

Proton therapy system

2

patient

3

Proton beam

4

particle accelerator

5

Patient table

6

Electromagnet

7

Gantry

8A, 8B

Scanner magnet

9

last deflection magnet

9.1

Magnetic input

9.2

Magnetic output

10

Movement device

11

Radiation center

12

Control unit

13

conventional radiation therapy system

14

dynamic support device

15

Correction magnet

16

Fastening device

17

linear accelerator

18

Energy reduction system

R

Axis of rotation

Claims (10)

Proton therapy system (1) for treating a patient (2) using 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 having a plurality of electromagnets (6) for focusing and/or defocusing and/or deflecting the proton beam (3) and a gantry (7) which can be rotated about a horizontal axis of rotation (R) for directing the proton beam (3) onto a target volume within a patient (2) stored on the patient table (5), wherein the proton beam (3) has a maximum energy of less than 180 MeV. Proton therapy system (1). Claim 1 , wherein the beam guidance device has 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 arranged in the proton beam direction between the scanner magnets (8A, 8B). (9), wherein the deflection magnet (9) is designed 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). Proton therapy system (1). Claim 1 or 2 , wherein the beam guidance device is designed to deflect the proton beam (3) for an irradiation field with a first maximum side length a and a second maximum side length b, the side lengths a and b each being either 20 cm, 15 cm, 10 cm or 5 cm . Proton therapy system (1) according to one of the preceding claims, wherein the patient table (5) has a continuously movable movement device (10) which carries the patient table (5) and a control unit (12) which controls the movement device (10), the movement device (10) is designed to move the patient table (5) along three translation axes and rotate about three rotation axes. Proton therapy system (1). Claim 4 , wherein the control unit (12) is designed to move the patient table (5) relative to the gantry (7) in such a way that an irradiation center (11) defined in the patient (2) also rotates about the axis of rotation (R) of the gantry (7). is rotated. Proton therapy system (1). Claim 2 and 5 , wherein the control unit (12) is designed to move the patient table (5) with a constant distance between the second scanner magnet (8B) and the irradiation center (11). Proton therapy system (1) according to one of the preceding claims, wherein the gantry (7) comprises a dynamic support device (14) which allows unintentional movement in addition to the rotation about the axis of rotation (R) by deforming the gantry (7), 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). Proton therapy system (1) according to one of the preceding claims, wherein the proton therapy system (1) is designed to make the patient (2) available for a spatially adjacent conventional radiation therapy system (13) by moving the patient table (5) and/or the movement device (10). . 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) included in the conventional proton therapy system (13). Use of a proton therapy system (1) according to one of the preceding claims for treating a patient (2) using proton therapy as a supplement to treatment of the patient using conventional radiation therapy.

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