The Accelerator Group at the Physics Division has recently developed a conceptual design for an Advanced Compact Carbon Ion Linac (ACCIL) capable of producing the full energy 450 MeV/u carbon beam required for cancer therapy in under 50 meters . While only synchrotrons are being used in existing carbon ion beam facilities, a linac operated in pulsed mode offers more flexibility in pulse structure, fast pulse-to-pulse energy and intensity modulation as well as fast beam switching between ion species. This much desired flexibility in beam tuning enables the fast and efficient beam scanning to allow 3D dose painting, as well as real-time image-guided range verification and targeting of moving tumors.
Depending on the tumor shape, size, and location, the required dose could be effectively delivered through a straight beamline or through a rotating gantry, with the possibility of beam scanning in both cases. Existing facilities usually have few treatment rooms with simple beamlines and one room equipped with a gantry system. A room-temperature proton gantry is reasonably sized, but carbon beams require a gigantic gantry due to their larger magnetic rigidity (e.g. the 600-ton gantry recently built at the Heidelberg HIT facility). In collaboration with the Advanced Magnet Laboratory (AML), we have recently developed a concept for a compact superconducting carbon ion gantry that has the same size but which weighs less than the smallest present-day proton gantry .
X-ray radiography and cone-beam CT imaging are routinely used to verify that the patient’s internal anatomy is positioned correctly relative to the treatment beam. A major limitation, however, is the poor soft tissue visualization which leads to difficulties tracking the target and organs-at-risk motions. MRI imaging, positron emission tomography, and ultrasound are potential non-invasive methods that could be combined real-time with a beam delivery system. Developments to combine real-time image guidance with ion beam delivery systems are essential to take full advantage of the physical and radiobiological benefits of ion beam therapy.
Hadron or ion beam therapy research at Argonne is aligned along the three major axis listed below with ongoing or planned projects.
Development of high gradient structures for ACCIL
The realization of ACCIL requires S-band room-temperature structures capable of 50 MV/m accelerating fields. Two funded projects are underway:
- Development of a negative harmonic traveling-wave cavity for β ~ 0.3, a DOE/HEP SBIR project lead by Radiabeam in collaboration with Argonne .
- Development of an annular-coupled standing-wave structure for β ~ 0.4, an ANL/LDRD project.
R&D for compact SC carbon beam gantries
A compact combined function scanner magnet is an essential piece for the realization of a compact ion beam gantry. A DOE Accelerator Stewardship project is underway to develop such a magnet. This project is lead by Argonne in collaboration with AML and other. The success of this project will enable even more compact proton beam gantries small enough to fit in existing proton therapy rooms not originally designed to host a gantry.
R&D to combine real-time imaging with ion beam delivery systems
With Argonne’s expertise in accelerators and beam delivery systems and UChicago’s Department of Cellular and Radiation Oncology experience with radiotherapy and MRI imaging, we propose to develop an innovative and economical concept for MRI-guided ion beam therapy. Once proven, such a system can be developed and used in existing proton and ion therapy facilities, potentially enhancing the outcome of particle beam therapy.
Although a new activity at Argonne, hadron therapy research is now well established along the first two major axis and we are working to establish the third one in the near future. The ultimate goal of these activities is to build a prototype ion therapy linac based on the ACCIL design and establish an ion beam therapy research center in the Chicago area.
In addition to these developments towards an advanced ion therapy research facility in the future, we started an experimental research program at the ATLAS facility here at Argonne aimed at both imaging and cellular radiobiology using the low-energy ion beams available at ATLAS.
Thermoacoustic imaging for pulsed ion beams
As ions loose a significant part of their energy before they stop (Bragg peak), a pressure wave is generated and can be detected if the ion beam is pulsed at a certain rate. This allows to measure the ion beam range to the mm level. This thermosacoustic imaging method relies on the detection of ultrasound waves generated by the beam using existing medical ultrasound systems. To quantify the robustness of thermoacoustic range verification to acoustic inhomogeneity in different media, two experiments were performed at ATLAS, one with protons and one with helium ions. The experiment were successful and proved that thermoacoustic range verification is robust to acoustic inhomogeneity . A future experiment with carbon ion beam is planned in the near future. This work is led by S. Patch of the University of Wisconsin at Milwaukee (UWM) in collaboration with ANL’s Physics Division.
Cellular radiobiology studies
By using the capability of ATLAS to deliver low energy light ions from protons to neon many fundamental issues related to the radiation cellular biology of ion beam therapy can be investigated. Among these are: the response of a variety of human cells to various doses of light ions covering a large range of dE/dx or LET, the so-called “bystander effect” whereby unirradiated cells in the vicinity of irradiated cells respond to the radiation, and detailed studies of the relative biological effectiveness (RBE) of light ions when the spread out Bragg peak is comprised of a range of dE/dx. The first run with the goal of exploring the response of several types of human cells to the Bragg peak of protons, lithium beams, and carbon beams took place in May 2018. Beyond this first exploratory run further research is planned in the future building on these results. This work is led by T. Paunesko and G. Woloschak of the Radiation Oncology group at the Feinberg School of Medicine at Northwestern University in collaboration with ANL’s Physics Division.
- P. Ostroumov et al, “Compact Carbon Ion Linac”, Proceedings of NAPAC-2016 Conference, Chicago, IL, October 10-14, 2016.
- S. Ishmael et al, “Actively-Shielded, Bent Gantry System for Ion Beam Therapy Based on Round YBCO Wire”, Presentation at the Applied Superconductivity Conference ASC-2016, Denver, Co, USA.
- S. Kutsaev et al, “High-Gradient Low-β Accelerating Structure Using the First Negative Harmonic of the Fundamental Mode”, Physical Review Accelerators and Beams 20 (2017) 120401.
- S. Patch et al, “Thermoacoustic Range Verification in the presence of Acoustic Heterogeneity and Soundspeed Errors - Robustness Relative to Ultrasound Image of Underlying Anatomy”, Accepted for publication in Medical Physics.