Italy's National Institute for Nuclear Physics (INFN), ACCEL Instruments GmbH and Ansaldo Superconduttori are to collaborate on a novel superconducting multiparticle cyclotron for hadron therapy. The machine will be based on a concept that has been developed at the INFN Laboratori Nazionali del Sud (LNS) in Catania.

Radiation therapy using hadrons - protons and ions - was proposed by Robert Wilson some 60 years ago, as these particles have a better dose-depth distribution in tissue compared with X-rays. This gives an improved conformity of delivered dose on a tumour, allowing the dose to the tumour to be increased, while reducing the risk to healthy tissue and nearby critical organs. However, the relative size and complexity of accelerators for protons and ions mean that most of the 40,000 patients treated with hadrons to date have been irradiated at large research institutions where appropriate particle beams are available. Only in the past decade have suitable accelerators and beam-delivery systems been developed, and the first few dedicated clinical-therapy facilities for protons have now been built. Many more are in the planning stage.

Ions such as carbon are interesting because different biological mechanisms are involved in their interactions, compared with protons, but therapy systems using ions are even bigger and more complex than those for protons only. Two such facilities are under construction in Europe, one by GSI for the university clinics in Heidelberg, and one at Italy's national hadron-therapy centre, the Centro Nazionale di Adroterapia Oncologica (CNAO) in Pavia, with major involvement from INFN and Ansaldo Superconduttori.

An ion-therapy system usually requires a synchrotron 16-25 m in diameter as its main accelerator, while most therapy systems based only on protons use compact cyclotrons - being a continuous source, the cyclotron is more suitable for beam scanning across a tumour. In this context, ACCEL has developed a novel superconducting proton cyclotron only 3  m in diameter, with superior beam-delivery characteristics. This forms the particle source for proton-therapy installations at the Paul Scherrer Institute (PSI) in Villigen, and for Europe's first clinical proton-therapy system at the Rinecker Proton Therapy Center (RPTC) in Munich, which ACCEL is currently commissioning.

To combine the advantages of a superconducting cyclotron with the goal of accelerating different species of ions in addition to protons, INFN has developed a concept for a multiparticle-therapy cyclotron. This is based on LNS Catania's extensive experience both with cyclotron technology and operation, and with its successful proton-therapy programme for eye tumours, in which 87 patients have been treated since 2002. Combining this experience with commercial and technical considerations of size and weight for transport, handling and operational environment has led to a machine concept for providing beams of 250 AMeV protons and light ions. Owing to their stronger interaction in human tissue, carbon ions will have limited penetration depth, but will still cover relevant treatment cases, as has been shown by ion-therapy studies in Japan.

The newly formed collaboration between INFN, ACCEL and Ansaldo Superconduttori is designing this multiparticle cyclotron as a solution for the worldwide clinical ion/proton-therapy market that is more cost effective, and less operator and maintenance intensive. While it will have somewhat reduced energies for heavier ions such as carbon, it will have superior beam characteristics compared with synchrotron-based installations.

The novel superconducting accelerator is a clear example of the benefits brought by advances over the past 30 years in the application of superconductivity to accelerators in particle and nuclear physics laboratories. This research is culminating now with the Large Hadron Collider under construction at CERN, where both ACCEL and Ansaldo Superconduttori are heavily involved in the construction of the main superconducting magnets.