Secondary neutron doses in a compact proton therapy system.

Proton therapy offers several advantages compared with classical radiotherapy owing to a better dose conformity to the tumour volume. However, proton interactions with beam transport elements and the human tissues lead to the production of secondary neutrons, resulting in an extra whole-body dose with some carcinogenic potential. In this study, the secondary neutron doses generated with an active beam scanning system and with two compact proton therapy systems recently appeared on the market are compared.

Overview of the IBA accelerator-based BNCT system.

During the last few years, IBA started the development of an accelerator-based BNCT system. The accelerator is a Dynamitron built by RDI in USA and will produce a 20 mA proton beam at 2.8 MeV. Neutrons will be produced by the (7)Li(p,n)(7)Be nuclear reaction using a thin lithium target. The neutron energy spectrum will be tailored using a beam shaping assembly. This overview presents the current status of the system: after a description of every component, some design issues, solutions and experimental tests will be discussed.

Radiotherapy systems using proton and carbon beams.

Radiotherapy using proton beams (proton therapy) is rapidly taking an important role among the techniques used in cancer therapy. At the end of 2007, 65.000 patients had been treated for cancer by proton beams in one of the 34 proton therapy facilities operating in the world. When compared to the now classical IMRT, and for a similar dose to the tumor, proton therapy provides a lower integral dose to the healthy organs surrounding the tumor. It is generally accepted that any reduction of the dose to healthy organs reduces the probability of radiation induced complications and of secondary malignancies. Proton therapy equipment can be obtained today from well established medical equipment companies such as Varian, Hitachi or Mitsubishi. But it is a Belgian company, Ion Beam Applications of Louvain-la-Neuve that is the undisputed leader in this market, with more than 55% of the world installed base. In addition to the now classical proton therapy equipments, using synchrotrons or cyclotrons as accelerators, new solutions have been proposed, claiming to be more compact and less expensive. A small startup company from Boston (Still Rivers) is proposing a very high magnetic field, gantry mounted superconducting synchrocyclotron. The us Company Tomotherapy is working to develop a new accelerator concept invented at Lawrence Livermore National Laboratory: the Dielectric Wall Accelerator. Besides proton beam therapy, which is progressively becoming an accepted part of radiation therapy, interest is growing for another form of radiotherapy using ions heavier than protons. Carbon ions have, even to a higher degree, the ballistic selectivity of protons. In addition, carbon ions stopping in the body exhibit a very high Linear Energy Transfer (LET). From this high LET results a very high Relative Biological Efficiency (RBE). This high RBE allows carbon ions to treat efficiently tumors who are radio-resistant and which are difficult to treat with photons or protons. The largest experience in carbon beam therapy comes from Japan, from the National Institute for Radiation Science (NIRS) in Chiba, where more than 4000 patients have been treated with carbon beams. In Europe, carbon beam therapy has been tested on a limited number of patients in GSI, a national laboratory for heavy ion research in Darmstadt. A clinical carbon therapy center has been developed by GSI and the prototype is located at the German National Cancer Research Center (DKFZ) in Heidelberg. This center (HICAT) is close to being completed, and should treat patients in 2009. Another national carbon therapy facility is under construction in Pavia (Italy), and is build by a group of Italian physics laboratories. Siemens has obtained the intellectual rights of the GSI design in Heidelberg, and has sold two other carbon therapy systems in Germany, one in Marburg and one in Kiel. All existing systems for carbon therapy use cyclotrons as accelerators. IBA has introduced the innovative concept of using a superconducting cyclotron for the acceleration of carbon ions for radiotherapy. The superconducting cyclotron technology should allow a reduction of the size and cost of carbon therapy facilities.

Some factors influencing the cost of a hospital based proton therapy centre.

The nowadays availability of state-of-the-art proton therapy equipment from commercial companies, on a contract basis, makes it easier to precisely account for equipment prices as well as to better evaluate the consequences of the equipment characteristics on operating costs and possible patient throughput. This paper presents some data which can be used for the evaluation of these items.

The proton therapy system for MGH's NPTC: equipment description and progress report.

At the beginning of 1994, the Massachusetts General Hospital (MGH) of the Harvard Medical School in Boston (MA, USA) a pioneer in proton therapy since 1959, selected a team led by Ion Beam Applications SA (IBA) to supply the proton therapy equipment of its new Northeast Proton Therapy Centre (NPTC). The IBA integrated system includes a compact 235 MeV isochronous cyclotron, a short energy selection system transforming the fixed energy beam extracted from the cyclotron into a variable energy beam, one or more isocentric gantries fitted with a nozzle, a system consisting of one or more horizontal beam lines, a global control system including an accelerator control unit and several independent but networked therapy control stations, a global safety management system, and a robotic patient positioning system. The present paper presents the equipment being built for the NPTC.