WO2015070865A1

WO2015070865A1 - Particle therapy system

Info

Publication number: WO2015070865A1
Application number: PCT/DK2013/050380
Authority: WO
Inventors: Lars Kruse
Original assignee: Danfysik A/S
Priority date: 2013-11-14
Filing date: 2013-11-14
Publication date: 2015-05-21
Also published as: EP3068489A1; WO2015071430A1

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. Figure

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) are used, with energies in the range 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.

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 for cancer therapy 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.

In a presently preferred embodiment 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 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. Also included is a synchrotron that accelerates the beam to a requested (not fixed) energy, 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.

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 relates 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 and 2 are schematic illustrations of a particle therapy system. DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1 schematically illustrates 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 accelerate the low energy pre-accelerated beam to an accelerated beam. The synchrotron based accelerator 14 comprises 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. This energy level may be set via an input device such as a keyboard or dial. 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 in a desired direction inside the gantry.

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 20 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 20 opening. 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. 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 and extraction to the synchrotron may be perpendicular to or angled to the plane of the synchrotron.

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 synchrotrons 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 for example 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 divergence 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. 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 direction 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.

Figure 2 is a schematic side view of the particle therapy system 10. Here it is seen 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.

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.

Claims

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 claim 1, wherein the injector is mounted on the gantry or alternatively remote from the gantry.

3. The particle therapy system according to claim 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 claim 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 claims 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 claims 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 claims 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 claims 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 claims 1-8, wherein the system is fitted into a single room.

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

11. The particle therapy system according to any one of claims 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 claim 1 in a system for particle therapy according to a treatment plan.

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

14. 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.

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