WO2015071430A1

WO2015071430A1 - Particle therapy system

Info

Publication number: WO2015071430A1
Application number: PCT/EP2014/074649
Authority: WO
Inventors: Lars Kruse
Original assignee: Danfysik A/S
Priority date: 2013-11-14
Filing date: 2014-11-14
Publication date: 2015-05-21
Also published as: WO2015070865A1; EP3068489A1

Abstract

The present invention relates to a particle therapy system for cancer therapy with a rotatable gantry. The present invention further relates to use of a particle therapy system for particle therapy according to a treatment plan. Still further the present invention relates to use of a particle therapy system wherein the particle therapy system is placed in a single room, and a method of operating a particle therapy system.

Description

PARTICLE THERAPY SYSTEM

FIELD OF THE INVENTION

The present invention relates to a particle therapy system, use of a particle therapy system and a configuration and layout of a particle therapy system.

BACKGROUND OF THE INVENTION

In treatment of cancer, particle therapy is one of modern cancer therapies that use beams of protons or heavier ions. Treatment of cancer by irradiation of tumours with ions shows benefits over irradiation with photons because favourable energy deposition of the ions in the Bragg peak. One example of particle therapy is proton therapy techniques which are based on the use of proton beams, therapeutic beams of relatively low current (of the order of some nano-amperes, nA) are used, with energies in the range of 60 to 250 MeV.

In other settings using different ion species, therapeutic beams with lower currents and higher energies are required compared to the ones for the protons. For example, in the case of carbon ions i₂C⁶⁺, the required energies are between 1.500 and 5.000 MeV (i.e. 120 and 450 MeV/u) and currents of a fraction of nano-ampere.

Some particle therapy systems are described in e.g. US 8,153,990 or US 8,405,056.

These systems are relatively large and space consuming spanning several rooms in e.g. a hospital. These facilities require a large area in a dedicated building for radiation therapy.

JP patent application 2001/346893 discloses a radio-therapeutic apparatus which achieves a smaller volume. The apparatus is equipped with a gantry installed rotatably about a rotating shaft, a synchrotron is provided with a particle generator and a particle

accumulation ring carried on the gantry. An irradiation field is formed by the rotary gantry so as to guide a corpuscular beam to an irradiation field along the irradiation axis crossing the rotating shaft.

JP patent application H05 188200 discloses another attempt to miniaturize a synchrotron i.e. rotatable gantry is set up centred around the position of a patient to be irradiated, and a driving part for driving the gantry is set up in the lower part of the gantry. An emitting part for emitting a charged particle on the patent is set up in the synchrotron. The synchrotron can be miniaturized and the space for setting up the synchrotron can be made small, because the synchrotron and the gantry are set up in one part.

Hence, an improved, and in particular more compact, particle treatment system would be more cost efficient and advantageous.

OBJECT AND SUMMARY OF THE INVENTION

One object of the present invention is to provide a compact and versatile particle therapy system . It is a further object of the present invention to provide an alternative to the prior art.

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a particle therapy system - preferably for cancer therapy though other diseases could be treated - of a patient comprising an synchrotron based accelerator mounted on a rotatable gantry, the synchrotron based accelerator configured for receiving a low energy pre-accelerated beam from an injector and accelerate the low energy pre-accelerated beam to an accelerated beam, the synchrotron based accelerator comprising a synchrotron that energizes the beam to a desired energy level, wherein the desired energy level is defined within a target energy level interval and may be changed during use of the system, and a beam transport line directing the accelerated beam in a desired direction inside the gantry the beam transport line being wrapped around the gantry in a helical and/or axial geometry, the beam transport line further being arranged for directing said accelerated beam to a beam position outside of a plane of the synchrotron .

In presently preferred embodiments, the particle therapy system uses a proton or a charged particle beam such as carbon, which is accelerated by an accelerator. The particle therapy system includes an accelerator, a beam transport system and an irradiation device. The accelerator such as a synchrotron is adapted to accelerate a beam emitted by an ion source to a level close to the speed of light. The beam transport system is adapted to transport the beam extracted from the accelerator. The irradiation device is adapted to irradiate an affected area of a patient, i.e. the beam position for therapy of said patient, with the beam in accordance with the location and shape of the affected area or volume. The proposed particle therapy system, simply said, comprises a synchrotron based accelerator that is axially mounted on a rotatable gantry. The accelerator is composed of, at least, an injector, that provides a low energy pre-accelerated beam to be injected into a synchrotron. A synchrotron that accelerates the beam to a requested (not fixed) energy is also included, and further; a beam transport line formed so as to direct the beam to the patient.

The system renders all the benefits of a synchrotron beam available in a configuration that allows irradiation of a tumor from many directions in a single, compact system. Still further the system may be built at a reduced cost when compared to the prior art particle therapy apparatus.

One benefit of a beam from a synchrotron over other accelerator types are at least that the beam is accelerated to a desired energy level and delivered to the patient, or a treatment volume in the patient, without the use of degraders, as are known from e.g. fixed energy cyclotrons. This again has the positive effect that a pencil beam with a small spot sizes at the patient can be achieved without collimators and that the beam can be actively scanned over a tumor, in contrast to passive scanning, where the beam is sent through a system of scattering material, collimators and compensators, and thus preserve the high beam quality in terms of small and well defined spot size and low energy spread.

The invention is particularly, but not exclusively, advantageous for obtaining a compact, versatile particle therapy system which allows an entire, or at least the main part of, particle therapy system to be located in a single room, preferably of a size within 7 meters x 9 meters in floor area and 7 meters in height, thereby representing a significant reduction in the required space for particle therapy compared to present state of the art solutions. The present invention enables the possibility to minimize the diameter of the synchrotron, e.g. below 5 meters, limited only by the magnetic rigidity of the main bending magnets in the synchrotron and not by the need for space for other equipment, such as beam line or the patient, therefore reducing the overall footprint in the hospital environment where the relative cost of space is normally high.

The invention is particularly, but not exclusively, advantageous for obtaining a significant reduction in undesirable radiation to the patient from the synchrotron. In preferred embodiments of the present invention, the synchrotron encircles the gantry and the patient is positioned, at least partly, during therapy within the gantry, but inevitably, the synchrotron will produce a significant level of background radiation, especially of neutrons, even inside the synchrotron. Notice from a theoretical point of view one would expect that a synchrotron only emits electromagnetic radiation tangentially outwards from the corners of synchrotron, but in practise there will also be some radiation within the synchrotron, particularly in the plane of the synchrotron. This background radiation is, however, avoided, reduced and/or mitigated by the present invention.

It is to be understood that the beam transport line being wrapped around the gantry (i.e. mounted or positioned on the gantry) in a helical geometry will typically be helically around an axis parallel to the rotational axis of the gantry. Similarly, the beam transport line wrapped in an axial geometry on the gantry will be mounted on the gantry in a direction substantially parallel to the rotational axis of the gantry.

It is to be understood that the beam transport line being arranged for directing said accelerated beam to a beam position outside of the plane of the synchrotron-based accelerator is thereby offset - along a rotational axis of the rotatable gantry-to reduce the diameter of the synchrotron to a minimum (4-5m) in order to minimize the footprint of the machine and to avoid undesirable radiation from the synchrotron.

It is to be understood that a gantry is an entity capable of supporting the synchrotron based accelerator and other components, and large enough to have a patient (or at least a part of a patient to be treated) positioned inside it as it will be understood by a person skilled in radiation therapy. Typically, the gantry will have a cylindrical-like structure for easy rotation. Thus, the gantry may both be capable of supporting the synchrotron based accelerator and has an internal volume large enough to have a patient, or at least a part of a patient to be treated, positioned inside the internal volume during use of the system for particle therapy. The diameter of the gantry in a cylinder-like structure may be in the range of approximately 4-6 meters, preferably around 5 meters representing a significant reduction in the required space for particle therapy compared to present state of the art solutions, such as JP patent application H05 188200, which would normally require about the double diameter of the gantry. It is to be understood by a person skilled in the art that a synchrotron is generally accepted as a type of cyclic particle accelerator, developed from the cyclotron, in which the guiding magnetic field (bending the particles into a closed path) is time-dependent, and being synchronized to a particle beam of increasing kinetic energy. The synchrotron is an accelerator concept enabling the construction of large-scale facilities, since bending, beam focusing and acceleration can be separated into different components. In the context of the present invention, a distinction will be made between the synchrotron based accelerator and the synchrotron, specifically in that the synchrotron based accelerator comprises the synchrotron as a sub-component.

In some embodiments, the particle therapy system may have an injector mounted on the gantry i.e. it may be rotated with the gantry for compact design, or alternatively remote from the gantry i.e. not on the gantry. Also, the synchrotron based accelerator may be mounted on the gantry to form a continuous ring (typically around the gantry's rotational axis) and having an outlet to the beam transport line delivering the radiation beam to the patient.

In preferred embodiments, the system may comprise a protective wall positioned between a plane of the synchrotron and the beam position for therapy of said patient, the plane having a certain extension in the axial direction of the gantry. In case of a non-standard geometry of the closed loop of the synchrotron, it may be possible to define a plurality of planes and it will be understood that they may be characterized by, at least, an average plane.

A second aspect of the present invention relates to use of a particle therapy system. The particle therapy system may include any or all features mentioned in relation to the first aspect of the present invention. The particle therapy system is further operated in accordance with a treatment plan. The treatment plan may be established using a treatment planning system which receives the relevant inputs e.g. regarding tumour position, tumour size and shape. The treatment plan includes at least dose rates and dose timings as well as target positions.

A third aspect relates to a method of operating a particle therapy system according to the present invention, in accordance with a treatment plan for directing particles to a tumour location in a patient. The first, second and third aspects of the present invention may each be combined with any of the other aspects and include any features mentioned in relation to any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The particle therapy system, and its use, according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figures 1-4 are schematic illustrations of a particle therapy system, Figure 1 being a perspective drawing and Figures 2-4 are schematic side-view drawings Figures 3 and 4 also show elements inside the gantry.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1 schematically illustrates a perspective view of a particle therapy system 10 for cancer therapy. The particle therapy system 10 comprises a rotatable gantry 12. On the rotatable gantry 10, an synchrotron-based accelerator 14 is mounted. The synchrotron based accelerator 14 is configured for receiving a low energy pre-accelerated beam from an injector 15 and accelerates the low energy pre-accelerated beam to an accelerated beam. The synchrotron based accelerator 14 comprises a synchrotron 14' that energizes the beam to a desired energy level, wherein the desired energy level is defined within a target energy level interval and may be changed during use of the system. This energy level may be set via an input device such as a keyboard or dial. The synchrotron based accelerator 14 thus also comprises the injector 15, and other components (not shown) needed for its operation and which will not be explained in details here since the skilled person will understand how a synchrotron based accelerator works. Further, a scheme may be defined including timing and positioning of the beam direction. The scheme may be defined by using a therapy planning system. The particle therapy system 10 may then be operated according to the scheme. The particle therapy system 10 further comprises a beam transport line 16 directing the accelerated beam R in a desired direction inside the gantry. The beam transport line 16 is particularly wrapped around the gantry 20 in a helical and/or axial geometry, the beam transport line further being arranged for directing said accelerated beam R to a beam position RP outside of the plane 14P of the

synchrotron 14', cf. Figures 1-3.

The particle therapy system 10 makes all the benefits of a synchrotron beam available in a configuration that allows irradiation of a tumor from many directions in a compact system. The rotating beam delivery system is capable of delivering beam to the target from multiple irradiation directions. The target, i.e. the tumor, is generally positioned at a fixed position and in order to refrain from harming the surrounding tissue there is a need for irradiating the target from several directions. The fixed position of the tumor is aimed to be at the crossing of the rotation axis of the gantry and the central treatment beam axis. This crossing point is called iso-center and gantries of this type capable of delivering beams from various directions to the iso-center are called iso-centric gantries. Further, this is a need to protect the surrounding, healthy tissue by minimizing the radiation to these parts and therefore it is a requirement that the tumor may be irradiated from different directions at certain times, this information is saved in the aforementioned scheme or treatment plan . The gantry 12 is rotatable 360 degrees and is stoppable at any angular position .

As the system includes a rotatable gantry 12 the beam may be directed to a patient P fixated on a robotic table 22 so as to position the tumor at the above-mentioned fixed position . The robotic table 22 may be used for changing the patient position relative to the iso-center in all 3 dimensions in the gantry opening 20.

The benefits of a beam from a synchrotron over other accelerator types are that the beam is accelerated to a desired energy and delivered to the patient without the use of degraders, as are known from e.g . cyclotrons. This again has the positive effect that a pencil beam with small spot sizes at the patient can be achieved and that the beam can be actively scanned over a tumor (in contrast to passive scanning, where the beam is sent through a system of scattering material, collimators and compensators) and preserve the high beam quality in terms of small and well defined spot size and low energy spread . The energy level is chosen so as to obtain sufficient penetration depth in the tissue. The particle beam energies required to have sufficient penetration depth in the patient depend on the type of particles used .

The system illustrated in Figure 1 is intended to deliver a proton beam to a beam position RP for therapy of said patient P. The injector could be an ECR ion source and an RFQ with output energy of 2-3 MeV providing a proton beam of up to 20 mA. The length of such an injector could be as small as a few meters.

From the injector, the beam is injected into the synchrotron using single or multi turn injection, resulting in a coasting beam with lOE+ 10 - lOE+ 11 particles. The synchrotron accelerates the beam to the final energy in the range of 80 MeV - 250 MeV. A synchrotron dedicated to protons of energy up to 250 MeV (Bp = 2.42 Tm) could with normal conducting magnet technology be realized with a machine diameter of about 5 m .

From the synchrotron, the beam will be extracted slowly over seconds and guided to the patient. Such a system 10 could be fitted into a single room .

As illustrated in Figure 1 the synchrotron based accelerator 14 may be mounted on the gantry to form a continuous ring having an outlet to the beam transport line. In other embodiments the synchrotron based accelerator may be wrapped around the gantry in a helical geometry.

In addition the injection line and/or the extraction lines may be wrapped around gantry. The injection to and/or extraction from the synchrotron may be perpendicular to, angled, or parallel to the plane 14P of the synchrotron 14'.

The gantry beam delivery system comprises devices for shaping the beam to match the target, such as pencil beam or passive scattering . For establishing so-called pencil beam scanning capabilities of the particle therapy system, the extraction beam line may comprise scanning magnets, which in combination with the synchrotron's energy variation capability, allows the target volume to be scanned and treated by an intensity modulated pencil beam . For a pencil beam proton scanning system the beam emittance can e.g . be limited to 7.5 Pi mm mrad in both X and Y. For practical beam tuning purposes, just in front, downstream, of the divergence limiting or emittance limiting slits, a beam profile monitor can be installed, not illustrated in Figure 1. Instead of using a pair of slits in X and Y as means for reducing the d ivergence of the beam, other means could be used . For example one can use apertures or collimators with various diameters which may be positioned in the beam line.

The particle therapy system 10 is operated in accordance with a treatment plan for directing particle to a tumour location in a patient P. This treatment plan may be established by a treatment planning system where information such as tumor type and/or size is used to determine beam strength and d irection relative to the patient, this may be translated into angular information positioning the output of the particle therapy system . Depth conformity in the target volume is obtained by adequate control of the beam energy. In this way, a particle radiation dose can be delivered to the entire 3D target volume by e.g . raster scanning technique.

Generally the treatment plan may include a desired beam energy, position and dose to treat the target volume in the patient P.

Fig ures 2-4 are schematic side views of the particle therapy system 10 similar to Figure 1. In particular it is seen that the beam transport line 16 is substantially parallel to the rotational axis 20A of the gantry 20 i .e. the beam transport line is wrapped on the gantry i.e. mounted on the gantry 20 and arranged in an axial geometry relative to the gantry, i.e. when describing the gantry in cylindrical coordinates.

Figure 2 shows that the robotic table 22 may be used to position the patient along the z- axis and/or the y-axis as well as the x-axis i.e. a full three-dimensional control . The patient P is mainly positioned inside the gantry 20, in particular with the part of the body to be treated, even though other body parts may extend outside of the gantry (as schematically indicated in Figure 2) .

Figure 3 is similar to Figure 2 but further schematically shows that the beam transport line 16 is further arranged for directing said accelerated beam R to a beam position RP outside of the plane 14P of the synchrotron 14' within the gantry 20. Notice that in the practise the position RP is typically only a few millimetre wide, but the position is only schematically shown to indicated its position, preferably on the rotational axis 20A of the gantry i.e. the iso-center, but not necessarily because the full three dimensional control of the table 22 enables a number of particle therapy configurations. Preferably, the distance to D along the axial axis of the gantry is sufficiently large so as to avoid undesirable collateral radiation damage from the synchrotron based accelerator 14, the distance D being approximately at least 1 meter, preferably at least 2 meters, more preferably at least 3 meters. By off-setting the radiation beam R from the plane 14P, i.e. along an axial coordinate of cylinder-like structure of the gantry 20, the invention provides significantly improved particle therapy as compared to previous particle therapy systems.

Figure 4 shows an advantageous embodiment wherein the system comprises a protective wall 40 positioned between the plane 14P of the synchrotron-based accelerator and the beam position RP for therapy of said patient P. The wall may be supported by the gantry (not shown) . Various designs, shapes and materials (e.g . a lead-based material) may be applied for reducing undesirable radiation from the synchrotron based accelerator 14 to the patient P, as it will be recognised by the person skilled in radiation therapy once the teaching and general principle of the present invention is acknowledged .

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Below are listed some embodiments of the present invention : EMBODIMENTS :

1 A particle therapy system for cancer therapy comprising :

a synchrotron based accelerator mounted on a rotatable gantry, the synchrotron based accelerator configured for receiving a low energy pre-accelerated beam from an injector, and accelerate the low energy pre-accelerated beam to an accelerated beam, the synchrotron based accelerator comprising a synchrotron that energizes the beam to a desired energy level, wherein the desired energy level is defined within a target energy level interval and may be changed during use of the system, and

a beam transport line directing the accelerated beam in a desired direction inside the gantry.

2. The particle therapy system according to embodiment 1, wherein the injector is mounted on the gantry or alternatively remote from the gantry.

3. The particle therapy system according to embodiment 1, wherein the synchrotron based accelerator is mounted on the gantry to form a continuous ring having an outlet to the beam transport line.

4. The particle therapy system according to embodiment 1, wherein the beam transport line is wrapped around the gantry in a helical and/or axial geometry.

5. The particle therapy system according to any one of embodiments 1-4, wherein the injection and extraction to the synchrotron is perpendicular to or angled to the plane of the synchrotron.

6. The particle therapy system according to any one of embodiments 1-5, wherein the extraction beam line comprises scanning magnets, which in combination with the synchrotrons energy variation capability, allows the target volume to be scanned and treated by an intensity modulated pencil beam.

7. The particle therapy system according to any one of embodiments 1-6, wherein the system comprises an ECR ion source and an RFQ with output energy of 2-3 MeV providing a proton beam of up to 20 mA. 8. The particle therapy system according to any one of embodiments 1-7, wherein synchrotron using single- or multi turn injection, resulting in a coasting beam with lOE+ 10 - lOE+ 11 particles.

9. The particle therapy system according to any one of embodiments 1-8, wherein the system is fitted into a single room.

10. The particle therapy system according to any one of embodiments 1-9, wherein the gantry is an isocentrical gantry-like structure.

11. The particle therapy system according to any one of embodiments 1-10, wherein the gantry is rotatable 360 degrees, and is stoppable at any angular position.

12. Use of a particle therapy system according to embodiment 1 in a system for particle therapy according to a treatment plan.

13. Use of the particle therapy system according to embodiment 12, wherein the particle therapy system is placed in a single room.

14. A method of operating a particle therapy system according to embodiment 1, in accordance with a treatment plan for directing particle to a tumour location in a patient.

15. The method according to embodiment 14, wherein the treatment plan includes a desired beam energy, position and dose to treat the target volume.

Claims

1 A particle therapy system for cancer therapy of a patient (P), comprising : a synchrotron based accelerator (14) mounted on a rotatable gantry (12), the synchrotron based accelerator configured for receiving a low energy pre-accelerated beam from an injector (15), and accelerate the low energy pre-accelerated beam to an accelerated beam, the synchrotron based accelerator comprising a synchrotron (14') that energizes the beam to a desired energy level, wherein the desired energy level is defined within a target energy level interval and may be changed during use of the system, and a beam transport line (16) directing the accelerated beam (R) in a desired direction inside the gantry, the beam transport line being wrapped around the gantry in a helical and/or axial geometry, the beam transport line further being arranged for directing said accelerated beam to a beam position (RP) outside of a plane (14P) of the synchrotron.

2. The particle therapy system according to claim 1, wherein the injector (15) is mounted on the gantry, or alternatively remote from the gantry (12).

3. The particle therapy system according to claim 1, wherein the synchrotron based accelerator (14) is mounted on the gantry (12) to form a continuous ring having an outlet to the beam transport line (16).

4. The particle therapy system according to claim 1, wherein the system comprises a protective wall (40) positioned between the plane (14P) of the synchrotron and the beam position (RP) for therapy of said patient (P).

5. The particle therapy system according to claim 1, wherein the gantry (20) is capable of supporting the synchrotron based accelerator and has an internal volume (22) large enough to have a patient (P), or at least a part of a patient, positioned inside the internal volume during use of the system.

6. The particle therapy system according to any one of claims 1-5, wherein the injection to and/or extraction from the synchrotron is perpendicular to, or angled to, or parallel to the plane (14P) of the synchrotron.

7. The particle therapy system according to any one of claims 1-6, wherein the extraction beam line comprises scanning magnets, which in combination with the synchrotron's energy variation capability, allow a target volume to be scanned and treated by an intensity modulated pencil beam.

8. The particle therapy system according to any one of claims 1-7, wherein the system comprises an ECR ion source and a RFQ with output energy of 2-3 MeV providing a proton beam of up to 20 mA.

9. The particle therapy system according to any one of claims 1-8, wherein synchrotron uses single or multi turn injection, resulting in a coasting beam with lOE+10 - lOE+11 particles.

10. The particle therapy system according to any one of claims 1-9, wherein the system is fitted into a single room.

11. The particle therapy system according to any one of claims 1-10, wherein the gantry is an isocentrical gantry-like structure.

12. The particle therapy system according to any one of claims 1-11, wherein the gantry is rotatable 360 degrees, and is stoppable at any angular position.

13. Use of a particle therapy system according to claim 1 in a system for particle therapy according to a treatment plan.

14. Use of the particle therapy system according to claim 13, wherein the particle therapy system is placed in a single room.

15. A method of operating a particle therapy system according to claim 1, in accordance with a treatment plan for directing particle to a tumour location in a patient.

16. The method according to claim 15, wherein the treatment plan includes a desired beam energy, position and dose to treat the target volume.