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Recent advances for ion beam therapy accelerators using synchrotrons
Nuclear Instruments and Methods in Physics Research B 269 (2011) 2879–2881
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Recent advances for ion beam therapy accelerators using synchrotrons U. Weinrich ⇑ GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany
a r t i c l e
i n f o
Article history: Available online 22 April 2011 Keywords: Ion beam therapy Synchrotron Gantry Cancer treatment Slow extraction Scanning
a b s t r a c t Ion beam therapy has evolved a lot during the last years. After more than a decade of successful clinical studies and first treatment in hospital environment, the carbon beam treatment, which always relies on a synchrotron as main accelerator, has clearly shown its own potential. The clinical success of carbon beam treatment is indicated by the growing number of new fully clinical based facilities. There is a lot of improvement potential for these facilities in order to increase their treatment quality, functionality and capacity as well as the cost effectiveness of the patient treatment. This article focuses on the currently ongoing investigations to fully explore this potential. It can be concluded that synchrotron based ion beam facilities are improving into many directions. This will further improve their impact on the cancer treatment and consequently their benefit to the whole society. Ó 2011 Elsevier B.V. All rights reserved.
1. State of the art of synchrotron-based ion beam therapy accelerators Ion beam therapy (IBT) has evolved a lot during the last years [1]. Ion beam therapy covers in principle ions from protons to neon. However, only a few of these ions have been introduced to the clinical praxis for cancer treatment [2]. Proton therapy is now a routine operation in several clinical centers spread around the world. The accelerators for proton therapy are based on cyclotrons or synchrotrons. More recently, carbon beams for cancer therapy evolved towards fully clinical praxis. A list of those centers where patients have been already treated is given in Table 1. To achieve the treatment of up to 30 cm in the tissue the carbon ions have to reach energies of 430 MeV/u. At this energy level so far only synchrotron-based accelerators have been used. The first fully clinical based facility able to perform carbon and proton treatment came into operation in Hyogo in April 2001 [3]. The most recent facilities, which started patient treatment, are HIT in Heidelberg (November 2009) and GHMC in Gunma (March 2010) [4,5]. Both facilities consist of compact fully clinic-based units. Therefore, the overall situation can be summarized as follows: synchrotron-based therapy accelerators for ion beam cancer treatment in fully clinical environment are now operational at several centers in Japan and Germany. The HIT facility can deliver both carbon and proton beams and uses a pencil beam 3D raster scanning functionality. It can be classified as the state of the art of ion beam therapy. The main physical and technical characteristics of the HIT facility are listed in Table 2.
⇑ Tel.: +49 6159 71 3858; fax: +49 6159 71 2935. E-mail address: [email protected] 0168-583X/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2011.04.045
2. Projects on the way The very promising potential of ion beam therapy using carbon beams along with the presently proven capability to build these facilities in hospital environment leads to a growing interest of the worldwide community of radiologists. This is also reflected by the fact that today several units are in production or construction. A list of the projects where at least the production has started is given in Table 3. As it is normal for new projects, they include some additional features compared to ones already in operation. But also those in operation have not yet explored their full potential. The main directions of further developments go towards the extension of treatment quality, the functionality and capacity as well as the making the facilities more cost effective.
3. Envisaged improvements of treatment quality and functionality Several developments take place to further improve dose conformity and the reduction of normal tissue damage. These mainly include the acceleration of different types of ions, the increased geometrical flexibility and the considerations of the organ movements. Two ion sources enabling rapid change between carbon and protons are the basic set-up of the recent ion beam therapy facilities. However, today there is also a strong demand to explore the potential of the helium beam treatment since it offers longitudinal properties close to protons but with significantly reduced lateral scattering in tissue [4]. As a side remark, it should be noted that ideas to use positron-emitter beams like 11C and 13O also exist [7].
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U. Weinrich / Nuclear Instruments and Methods in Physics Research B 269 (2011) 2879–2881 Table 1 Facilities with carbon beam patient treatment. Facility
Patient treatment
HIMAC, Chiba GSI, Darmstadt HIBMC, Hyogo HIRFL, Lanzhou HIT, Heidelberg GHMC, Gunma
Since 06/1994 12/1997 until 07/2008 Since 04/2001 Since 11/2006 (100 MeV/u) Since 11/2009 Since 03/2010
Table 2 Main characteristics of HIT facility.
beam position and energy. The beam energy variation can be done by moving additional material in and out the beam path [9]. Another way is to move the HEBT beam laterally in a closed beam bump in order to pass different material thickness [10]. To achieve the goal without using passive elements, it was proposed to actively vary the synchrotron energy within a synchrotron cycle [11]. It is also envisaged to use the remaining particles of a synchrotron cycle for the other isoenergetic slices by changing the extraction energy in steps downwards [12]. 4. Envisaged improvements of treatment capacity
Parameter
Description
Ion type Ion beam range in tissue Treatment field size Treatment principle Beam sizes in isocenter Beam spill structure Accelerator up time Accelerator reliability
Carbon, proton 30 cm 20 20 cm 3D pencil beam raster scanning Four steps Constant over 5 s 335 days per year 98%
Table 3 Carbon beam facility projects. Facility
Status
HITEL, Lanzhou RKA, Marburg CNAO, Pavia NROCK, Kiel HIMAC extension, Chiba SPHITH, Shanghai MedAustron, Wiener Neustadt
Treatment room commissioning HEBT commissioning Synchrotron commissioning LINAC commissioning Under construction Under production Under production
It also turns that typical ECR ion sources require significant maintenance. In order to assure the availability of protons and carbon ions at any time of operation, at least one additional ion source is required. As a consequence, the standard equipment now evolves towards three ion sources [4,6]. Carbon beam treatment has been so far applied by fixed horizontal or vertical beam lines. Several projects are on the way to further increase the geometrical flexibility of the beam entrance into the patient. One way is to provide a semi-vertical beam line, i.e. beam coming down towards the patient with a 45° angle [6]. Considering the geometrical flexibility one has always to keep in mind that patient tables can be rotated around the vertical axis. With a fixed horizontal beam one can therefore enter the patient from any lateral direction. Treatment planning using a semi-vertical beam line also profits to a large extent from the table rotation capability. This is of course not true for a pure vertical beam line which main purpose is to provide a beam perpendicular to horizontal beam. There is also always the possibility to rotate the patient table around its other axes by a few degrees. The most powerful solution is, however, to use a gantry which is able to transport the beam from all directions to the patient. The first carbon beam gantry is actually under final commissioning at HIT [4,8]. The second gantry is under construction within the frame of a new treatment research facility project at HIMAC [7]. The very precise ion beams also require a precise definition and stable location of the target volume. Due to organ motions (e.g. the breathing) this is not always the case. The first improvement step in this direction is to monitor the breathing of the patient and to use gating techniques to apply the beam only when the organ motion is minimal [7]. The next step is to follow with beam the movement, i.e. adjusting in a synchronous manner the
The investment and operation costs for ion beam treatment facilities are significant. In order to be competitive as full medical devices, the number of patients, that can be treated per facility, should be increased. The patients that can be treated per year depend on the number of fractions per patient, the number of treatment rooms, the number of treatments per room and time and the uptime of the facility. Investigations take place to treat patients for some indications with a drastically reduced number of fractions [7]. This immediately increases the demand for more total beam intensity in order to keep the treatment time in reasonable values. Maximum beam intensity optimization for this and other cases take place by improved synchrotron resonance corrections [7], improved ion sources [4], better RFQ structures [4,13] and multi RF harmonics operation of the synchrotron [7]. The actual standard number for treatment rooms is actually three to four. So far only HIMAC will surpass this number with its new treatment research facility. On the other hand, the further increase of the number of treatments per room and time is a subject for all facilities. The accelerator optimization possibilities serving this goal are manifold. One way is to introduce active field regulation for the synchrotron dipole magnets [4]. This avoids the needs for chimneys and shortens the time for field stabilization on the extraction flat top. In total the time of a synchrotron cycle can be significantly reduced. One isoenergetic slice should be treated with only one synchrotron cycle. In order to achieve this for laterally separated target volumes gating of the beam during scanner movement has to be included in the treatment. Another approach is to better use the beam charge accelerated in the synchrotron. Active feedback on the knock-out exciter can be used to create strong and well controlled intensity differences within one spill [7]. With this technique isoenergetic slices with different dose requirements for the raster points can be radiated faster. Carbon beam therapy facilities yield the potential to generate proton with extended ranges – up to 800 MeV [14]. Even if this may not be necessary for clinical use it might enlarge the potential use of the facility for experimental purposes. Another way to speed up treatment is the reduction of the number of raster point per isoenergetic slice when medically useful. This is for example the case when a uniform dose should be applied in the center of the target volume where large beam sizes can be afforded while at the boarder small beam sizes are requested for steep dose fall off. A treatment like this requires flexible beam sizes within one isoenergetic slice. In order to gain time a quadrupole adjustment within the spill and the use of gating need to be used. 5. Envisaged improvements of cost effectiveness Several improvements are on the way in order to minimize cost of investment and operation. First of all there is the cost reduction
U. Weinrich / Nuclear Instruments and Methods in Physics Research B 269 (2011) 2879–2881
due to industrial series production. Siemens Healthcare is in charge for three facilities (Marburg, Kiel and Shanghai) which are with the exception of specific customer requirements for treatment rooms designed, produced and constructed after the same manner [6]. This leads to reduced effort for development, construction and documentation and has the potential of sharing spare parts. Also production and commission efforts and times will decrease with time now. Carbon gantry size and weight can be reduced by relaxing on some of the requirements like field size or rotation angles [7]. There are improvements envisaged of building a more compact low energy beam line [4]. The recent facilities are already constructed in a compact design in order to keep building and infrastructure costs low. With growing experience on assembly and radiation protections requirements for sure the total amount of concrete can be further reduced.
6. Conclusions Synchrotron-based ion beam therapy centers represent the state of the art of radiation cancer treatment. The further increasing treatment functionalities of more ion species, improved geometrical flexibility and treatment of moving organs will open the door for the cure of more cancer indications. The developments to reduce the necessary beam time per patient treatment will improve the facility capacities if they are supported by either improved patient workflow or an increased number of treatment rooms. Industry entered the field of carbon beam treatment and develops the current clinical prototype facilities to a full medical product which can be accessed by many clinics.
2881
Better cancer treatment, more patient capacity, less costs. The world of synchrotron-based ion beam treatment facilities is clearly an expanding one to the benefit of the whole society. References [1] W.T. Chu, Relativistic ion beams for treating human cancer, Proceedings of the IPAC’10, Kyoto, Japan, 2010,. [2] A. Kitagawa, T. Fujita, M. Muramatsu, S. Biri, A.G. Drentje, Rev. Sci. Instrum. 81 (2010) 02B909. [3] [4] A. Peters, R. Cee, E. Feldmeier, M. Galonska, Th. Haberer, K. Höppner, M.B. Ripert, S. Scheloske, C.Schömers, T. Winkelmann, Operational status and further enhancements of the HIT accelerator facility, Proceedings of the IPAC’10, Kyoto, Japan, 2010, . [5] . [7] K. Noda et al., New treatment research facility project at HIMAC, Proceedings of the IPAC’10, Kyoto, Japan, 2010, . [8] U. Weinrich, C. Kleffner, Proceedings of the EPAC08, Genoa, Italy 2008, . [9] S.O. Grözinger, Volume conformal irradiation of moving target volumes with scanned ion beams, . [13] B. Schlitt et al., Linac commissioning at the Italian hadrontherapy centre CNAO, Proceedings of the IPAC’10, Kyoto, Japan 2010, . [14] M. Benedikt, J. Gutleber, M. Palm, W. Pirkl, U. Dorda, A. Fabich, Overview of the MedAustron design and technology choices, Proceedings of the IPAC’10, Kyoto, Japan 2010, .
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Recent advances for ion beam therapy accelerators using synchrotrons U. Weinrich ⇑ GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany
a r t i c l e
i n f o
Article history: Available online 22 April 2011 Keywords: Ion beam therapy Synchrotron Gantry Cancer treatment Slow extraction Scanning
a b s t r a c t Ion beam therapy has evolved a lot during the last years. After more than a decade of successful clinical studies and first treatment in hospital environment, the carbon beam treatment, which always relies on a synchrotron as main accelerator, has clearly shown its own potential. The clinical success of carbon beam treatment is indicated by the growing number of new fully clinical based facilities. There is a lot of improvement potential for these facilities in order to increase their treatment quality, functionality and capacity as well as the cost effectiveness of the patient treatment. This article focuses on the currently ongoing investigations to fully explore this potential. It can be concluded that synchrotron based ion beam facilities are improving into many directions. This will further improve their impact on the cancer treatment and consequently their benefit to the whole society. Ó 2011 Elsevier B.V. All rights reserved.
1. State of the art of synchrotron-based ion beam therapy accelerators Ion beam therapy (IBT) has evolved a lot during the last years [1]. Ion beam therapy covers in principle ions from protons to neon. However, only a few of these ions have been introduced to the clinical praxis for cancer treatment [2]. Proton therapy is now a routine operation in several clinical centers spread around the world. The accelerators for proton therapy are based on cyclotrons or synchrotrons. More recently, carbon beams for cancer therapy evolved towards fully clinical praxis. A list of those centers where patients have been already treated is given in Table 1. To achieve the treatment of up to 30 cm in the tissue the carbon ions have to reach energies of 430 MeV/u. At this energy level so far only synchrotron-based accelerators have been used. The first fully clinical based facility able to perform carbon and proton treatment came into operation in Hyogo in April 2001 [3]. The most recent facilities, which started patient treatment, are HIT in Heidelberg (November 2009) and GHMC in Gunma (March 2010) [4,5]. Both facilities consist of compact fully clinic-based units. Therefore, the overall situation can be summarized as follows: synchrotron-based therapy accelerators for ion beam cancer treatment in fully clinical environment are now operational at several centers in Japan and Germany. The HIT facility can deliver both carbon and proton beams and uses a pencil beam 3D raster scanning functionality. It can be classified as the state of the art of ion beam therapy. The main physical and technical characteristics of the HIT facility are listed in Table 2.
⇑ Tel.: +49 6159 71 3858; fax: +49 6159 71 2935. E-mail address: [email protected] 0168-583X/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2011.04.045
2. Projects on the way The very promising potential of ion beam therapy using carbon beams along with the presently proven capability to build these facilities in hospital environment leads to a growing interest of the worldwide community of radiologists. This is also reflected by the fact that today several units are in production or construction. A list of the projects where at least the production has started is given in Table 3. As it is normal for new projects, they include some additional features compared to ones already in operation. But also those in operation have not yet explored their full potential. The main directions of further developments go towards the extension of treatment quality, the functionality and capacity as well as the making the facilities more cost effective.
3. Envisaged improvements of treatment quality and functionality Several developments take place to further improve dose conformity and the reduction of normal tissue damage. These mainly include the acceleration of different types of ions, the increased geometrical flexibility and the considerations of the organ movements. Two ion sources enabling rapid change between carbon and protons are the basic set-up of the recent ion beam therapy facilities. However, today there is also a strong demand to explore the potential of the helium beam treatment since it offers longitudinal properties close to protons but with significantly reduced lateral scattering in tissue [4]. As a side remark, it should be noted that ideas to use positron-emitter beams like 11C and 13O also exist [7].
2880
U. Weinrich / Nuclear Instruments and Methods in Physics Research B 269 (2011) 2879–2881 Table 1 Facilities with carbon beam patient treatment. Facility
Patient treatment
HIMAC, Chiba GSI, Darmstadt HIBMC, Hyogo HIRFL, Lanzhou HIT, Heidelberg GHMC, Gunma
Since 06/1994 12/1997 until 07/2008 Since 04/2001 Since 11/2006 (100 MeV/u) Since 11/2009 Since 03/2010
Table 2 Main characteristics of HIT facility.
beam position and energy. The beam energy variation can be done by moving additional material in and out the beam path [9]. Another way is to move the HEBT beam laterally in a closed beam bump in order to pass different material thickness [10]. To achieve the goal without using passive elements, it was proposed to actively vary the synchrotron energy within a synchrotron cycle [11]. It is also envisaged to use the remaining particles of a synchrotron cycle for the other isoenergetic slices by changing the extraction energy in steps downwards [12]. 4. Envisaged improvements of treatment capacity
Parameter
Description
Ion type Ion beam range in tissue Treatment field size Treatment principle Beam sizes in isocenter Beam spill structure Accelerator up time Accelerator reliability
Carbon, proton 30 cm 20 20 cm 3D pencil beam raster scanning Four steps Constant over 5 s 335 days per year 98%
Table 3 Carbon beam facility projects. Facility
Status
HITEL, Lanzhou RKA, Marburg CNAO, Pavia NROCK, Kiel HIMAC extension, Chiba SPHITH, Shanghai MedAustron, Wiener Neustadt
Treatment room commissioning HEBT commissioning Synchrotron commissioning LINAC commissioning Under construction Under production Under production
It also turns that typical ECR ion sources require significant maintenance. In order to assure the availability of protons and carbon ions at any time of operation, at least one additional ion source is required. As a consequence, the standard equipment now evolves towards three ion sources [4,6]. Carbon beam treatment has been so far applied by fixed horizontal or vertical beam lines. Several projects are on the way to further increase the geometrical flexibility of the beam entrance into the patient. One way is to provide a semi-vertical beam line, i.e. beam coming down towards the patient with a 45° angle [6]. Considering the geometrical flexibility one has always to keep in mind that patient tables can be rotated around the vertical axis. With a fixed horizontal beam one can therefore enter the patient from any lateral direction. Treatment planning using a semi-vertical beam line also profits to a large extent from the table rotation capability. This is of course not true for a pure vertical beam line which main purpose is to provide a beam perpendicular to horizontal beam. There is also always the possibility to rotate the patient table around its other axes by a few degrees. The most powerful solution is, however, to use a gantry which is able to transport the beam from all directions to the patient. The first carbon beam gantry is actually under final commissioning at HIT [4,8]. The second gantry is under construction within the frame of a new treatment research facility project at HIMAC [7]. The very precise ion beams also require a precise definition and stable location of the target volume. Due to organ motions (e.g. the breathing) this is not always the case. The first improvement step in this direction is to monitor the breathing of the patient and to use gating techniques to apply the beam only when the organ motion is minimal [7]. The next step is to follow with beam the movement, i.e. adjusting in a synchronous manner the
The investment and operation costs for ion beam treatment facilities are significant. In order to be competitive as full medical devices, the number of patients, that can be treated per facility, should be increased. The patients that can be treated per year depend on the number of fractions per patient, the number of treatment rooms, the number of treatments per room and time and the uptime of the facility. Investigations take place to treat patients for some indications with a drastically reduced number of fractions [7]. This immediately increases the demand for more total beam intensity in order to keep the treatment time in reasonable values. Maximum beam intensity optimization for this and other cases take place by improved synchrotron resonance corrections [7], improved ion sources [4], better RFQ structures [4,13] and multi RF harmonics operation of the synchrotron [7]. The actual standard number for treatment rooms is actually three to four. So far only HIMAC will surpass this number with its new treatment research facility. On the other hand, the further increase of the number of treatments per room and time is a subject for all facilities. The accelerator optimization possibilities serving this goal are manifold. One way is to introduce active field regulation for the synchrotron dipole magnets [4]. This avoids the needs for chimneys and shortens the time for field stabilization on the extraction flat top. In total the time of a synchrotron cycle can be significantly reduced. One isoenergetic slice should be treated with only one synchrotron cycle. In order to achieve this for laterally separated target volumes gating of the beam during scanner movement has to be included in the treatment. Another approach is to better use the beam charge accelerated in the synchrotron. Active feedback on the knock-out exciter can be used to create strong and well controlled intensity differences within one spill [7]. With this technique isoenergetic slices with different dose requirements for the raster points can be radiated faster. Carbon beam therapy facilities yield the potential to generate proton with extended ranges – up to 800 MeV [14]. Even if this may not be necessary for clinical use it might enlarge the potential use of the facility for experimental purposes. Another way to speed up treatment is the reduction of the number of raster point per isoenergetic slice when medically useful. This is for example the case when a uniform dose should be applied in the center of the target volume where large beam sizes can be afforded while at the boarder small beam sizes are requested for steep dose fall off. A treatment like this requires flexible beam sizes within one isoenergetic slice. In order to gain time a quadrupole adjustment within the spill and the use of gating need to be used. 5. Envisaged improvements of cost effectiveness Several improvements are on the way in order to minimize cost of investment and operation. First of all there is the cost reduction
U. Weinrich / Nuclear Instruments and Methods in Physics Research B 269 (2011) 2879–2881
due to industrial series production. Siemens Healthcare is in charge for three facilities (Marburg, Kiel and Shanghai) which are with the exception of specific customer requirements for treatment rooms designed, produced and constructed after the same manner [6]. This leads to reduced effort for development, construction and documentation and has the potential of sharing spare parts. Also production and commission efforts and times will decrease with time now. Carbon gantry size and weight can be reduced by relaxing on some of the requirements like field size or rotation angles [7]. There are improvements envisaged of building a more compact low energy beam line [4]. The recent facilities are already constructed in a compact design in order to keep building and infrastructure costs low. With growing experience on assembly and radiation protections requirements for sure the total amount of concrete can be further reduced.
6. Conclusions Synchrotron-based ion beam therapy centers represent the state of the art of radiation cancer treatment. The further increasing treatment functionalities of more ion species, improved geometrical flexibility and treatment of moving organs will open the door for the cure of more cancer indications. The developments to reduce the necessary beam time per patient treatment will improve the facility capacities if they are supported by either improved patient workflow or an increased number of treatment rooms. Industry entered the field of carbon beam treatment and develops the current clinical prototype facilities to a full medical product which can be accessed by many clinics.
2881
Better cancer treatment, more patient capacity, less costs. The world of synchrotron-based ion beam treatment facilities is clearly an expanding one to the benefit of the whole society. References [1] W.T. Chu, Relativistic ion beams for treating human cancer, Proceedings of the IPAC’10, Kyoto, Japan, 2010,