Head of first patient
Head of first patient

The GSI facility will be used for a pilot project to treat several hundred patients over a five-year period. A typical course of treatment involves around 20 half-hour sessions on 20 consecutive days. For the irradiation the patient is immobilized on a treatment couch. Treatment currently focuses on head and neck tumours where adequate immobilization can be achieved.

Why carbon?

Carbon was chosen by GSI following a study of the biological efficiency of all ions from protons to uranium. The radiation damage it causes is repairable to a large extent in the entrance channel of the beam, and becomes irreparable only at the end of the beam's range ­ in the tumour itself.
  The crucial difference arises from the damage caused to cell DNA. Cancer cells and healthy cells alike die when their DNA sustains irreparable damage. In general, this means both DNA strands being broken since single strand breaks can frequently be repaired by the cell. GSI's studies showed that lighter particles such as protons, whilst depositing their energy in the Bragg peak, cause far fewer double-strand breaks than heavier ones like carbon. Moreover, the boundary between single and double-strand damage is particularly sharp with carbon which, coupled with GSI's beam delivery system, allows extremely precise targeting of the tumour ­ a factor which has been incorporated into GSI's treatment planning system.
  Another advantage is that carbon ions do not scatter as much as lighter particles. This allows higher degrees of conformity to be achieved. Heavier ions, such as neon, were discounted because they tend to fragment. Carbon does fragment to some extent, but the fragmentation products include positron-emitting carbon 10 and 11. Positron Emission Tomography, PET, then allows the radiotherapist to observe "live" the position of the beam in the patient with a resolution of 2.5 millimetres. The GSI facility is the first to use PET to give on-line control of a carbon beam during irradiation. This is essential for irradiation of tumours close to critical structures like the brain stem or spinal chord. The Rossendorf Research Centre in Dresden provided GSI's PET cameras.
  Carbon ions open up the possibility of treating a range of hitherto difficult tumours, and complement established proton therapy techniques. Protons, however, will remain important at many treatment centres for many kinds of cancer as well as for treatment of benign tumours.

The patient's head is held steady to within one millimetre using a mask, and the complete set up is checked by X-ray before each treatment session.

Patient comfort and safety have been given high priority. Whilst on the treatment couch, the patient can signal any discomfort to the radiotherapist. Even in the case of complete power failure to the magnets steering the beam, the patient will not be harmed since the undeviated beam trajectory passes high over the patient's head.

With its new concept in particle therapy the GSI facility joins a growing number of proton and ion therapy centres around the world. There are treatment centres in Canada, France, Germany, Japan, Russia, South Africa, Sweden, Switzerland, the United Kingdom, and the United States. So far, some 25 000 patients have benefited from proton or ion treatment and proton therapy machines are available "off the shelf". The proton-ion medical machine study, PIMMS, at CERN has optimized a design for a dedicated proton and ion therapy synchrotron. From a therapy point of view the PIMMS design improves on existing machines by providing much more stable beam extraction. The PIMMS study has been supported by the Italian TERA foundation and Austria's MED-Austron as well as GSI and CERN. Particle physicist Ugo Amaldi is behind the study and is a leading figure in efforts to coordinate research in the field on a European scale.

The GSI inauguration was attended by then Federal Minister for Education, Science, Research and Technology, Jürgen Rüttgers, and was opened by GSI Scientific Director Hans-J Specht. GSI's Gerhard Kraft presented the technical aspect of the project whilst Jürgen Debus of Heidelberg University's Radiological Clinic and the German Cancer Research Institute, DKFZ, described the medical aspects.

GSI inauguration
GSI inauguration

In parallel with the inauguration, a detailed proposal for a clinical facility to be installed at Heidelberg University was presented. It is based on knowledge and experience gained during the pilot phase, and also details gantries which will allow treatment planning to be optimized. Funding is expected to come partly from the German government, partly in the form of subsidies from industry which stands to gain a march in this emerging technology, and partly in the form of bank loans. The proposed cost of DM 40 000 for a course of treatment, to be agreed with German health insurers, includes an element to cover loan repayments.

Today, over 40% of patients developing cancer can be cured, but nevertheless in 20% of cases neither surgery nor conventional radiotherapy can be used successfully, even in cases where patients are initially diagnosed with one solid tumour only. With this new project GSI joins a growing world community of proton and ion-therapy centres offering new hope for these patients.