Medical applications
To be clinically effective, energies of several ion cyclotron for cancer therapy. This fixed hundred MeV are required for proton therapy. energy isochronous cyclotron's magnet system Pioneering projects had to work with complex, is optimized for high magnetic field but is still inadequate equipment originally intended for small enough to be installed in a hospital; it nuclear physics research, but recently a can deliver beams of up to 1.5 microamps for number of specialist organizations and treating certain categories of tumours. commercial companies have been working on dedicated systems for proton therapy. (From IBA, Louvain-la-Neuve, Belgium) This is an artist's view of a 235 MeV negative
As with other therapy methods, the accelerator is only one component, and it is important that manufacturers are able to offer integrated medical service systems
From Rudi Riesler, University of Washington, Seattle, USA
Proton therapy
deal radiotherapy deposits a large amount of energy in the tumour volume, and none in the surrounding healthy tissues. Proton therapy comes closer to this goal because of a greater concentration of dose, well defined proton ranges and points of energy release which are precisely known - the Bragg peak1. In the past, the development of deliver beams of up to 1.5 microamps, cyclotron, the beamline and the clinical proton therapy has been but with a hardware limitation to restrict gantry optics; hampered by complexity, size, and the maximum possible dose; - a safety management system, cost. To be clinically effective, ener - variable energy beam (235 to independent of the control system, gies of several hundred MeV are 70 MeV ) with energy spread and using hardwired interlocks and required; these were previously emittance verification; independent programmable logic unavailable for hospital installations, - a beam transport and switching controllers; and pioneering institutions had to system to connect the exit of the - a robotic patient positioning work with complex, inadequate energy selection system to the system, with monitoring equipment equipment originally intended for entrances of a number of gantries completely surrounding the patient. nuclear physics research. and fixed beamlines. Along the A few companies have proposed Recently a number of specialist beam transport system, the beam other systems, which may differ in organizations and commercial compa characteristics are monitored with concept designs for the gantries, nies have been working on dedicated non-interceptive multiwire ionization nozzles, patient positioners or safety systems for proton therapy. One, IBA chambers for automatic tuning; and control systems. The proton of Belgium, has equipment for in- - gantries fitted with nozzles and therapy system at the Loma Linda house hospital operation which beamline elements for beam control; University Medical Centre, California, encompasses a complete therapy both beam scattering and beam is based on a proton synchrotron and centre, delivered as a turnkey pack wobbling techniques are available for was built by the Fermi National age and incorporating a compact, shaping the beam; Accelerator Laboratory, the Loma automated, higher energy cyclotron - a control system including an Linda University, the Lawrence with isocentric gantries. Their system "accelerator control unit" with inde Berkeley Laboratory and Science will be installed at Massachusetts pendent and networked "therapy Applications International Corpora General Hospital, Boston. control stations". Through this net tion (SAIC) of San Diego. The proton therapy system com work, each of the therapy control prises: systems can also take over the From Y. Jongen, IBA S.A., Louvain, - a 235 MeV isochronous cyclotron to computer-based unit controlling the Belgium
10 CERN Courier, July/August 1995 Industrial applications
As well as providing proton beams In manufacturing industry, beams tion is often used in industry to for cancer treatment, accelerators from particle accelerators can be improve the quality of manufactured have also been used with particles used for a variety of purposes: goods or to reduce production cost. with higher linear energy transfer - to improve the quality or finish of a Products range from computer disks, (LET). Pioneer work with pions has product, as in the sterilization of shrink packaging, tyres, cables, and been carried out at the accelerators medical equipment; plastics to hot water pipes. Some at TRIUMF (Vancouver), the Swiss - to alter the material composition, products, such as medical goods, Paul Scherrer Institute and at Los as in ion implantation; cosmetics and certain foodstuffs, are Alamos. Therapy using ion beams is - to manufacture components, as in sterilized in this way. considered promising. The first silicon wafer production; In electron beam irradiation, elec clinical trials were at Berkeley, and - to provide information about trons penetrate materials creating an active programme has started at manufacturing processes, such as showers of low energy electrons. the GSI heavy ion Laboratory, wear studies of materials. After many collisions these electrons Darmstadt, using ions up to 300 MeV These industrial applications fre have the correct energy to create per nucleon. quently require small but well engi chemically active sites. They may Confidence in ion therapy is so high neered accelerator systems giving either break molecular bonds or that a $326 million dedicated syn reliable performance. activate a site which promotes a new chrotron facility - HIMAC, the Heavy chemical linkage. Ion Medical Accelerator in Chiba - This industrial irradiation can be has recently been completed near exploited in three ways: breaking Tokyo. Ions from helium to argon can Industrial irradiation down a biological molecule usually be accelerated up to 800 MeV per renders it useless and kills the nucleon for difficult cancers, such as roduction lines for rubber gloves organism; breaking an organic those in the head or neck, and P would not appear to have much molecule can change its toxicity or preliminary work with carbon ions in common with particle physics function; and crosslinking a polymer has shrunk tumours. laboratories, but they both use can strengthen it. High capital and operating costs will accelerators. Electron beam irradia In addition to traditional gamma inevitably restrict the availability of this therapy. Interest in proton therapy is particu larly high in the treatment of ocular melanoma where there is no alterna tive treatment, and success rates of up to 90% have been reported.
In this schematic of an industrial irradiation plant, a conveyor mechanism moves large containers through the radiation from an electron beam accelerator, The container contents are processed or sterilized. (Photos AEC Accelerators, Kanata, Canada)
CERN Courier, July/August 1995 11