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Recent applications of Synchrotrons in cancer therapy with Carbon Ions

2005; EDP Sciences; Volume: 36; Issue: 4 Linguagem: Inglês

10.1051/epn

1432-1092

U. Amaldi, Gerhard Kraft,

Particle accelerators and beam dynamics

A s shown in Table 1, accelerators originally designed for scien tific research have found a large number of industrial and medical applications.The main medical applications besides radioactive isotope pro duction with cyclotrons are the electron linacs of a few MeV for radiotherapy of deep seated tumours.Every year in the devel oped countries about 40,000 people out of 1 million inhabitants are diagnosed as having cancer.About 50% of these patients are treated with radiation, mainly high energy photons produced by electron linacs.In 90% of the cases the electron beam is convert ed to Bremsstrahlung photons.These photon beams (called "X-rays" by medical doctors) have replaced the low energy X-rays and the 60 Co gamma radiation because of a better depth-dose dis tribution (Fig. 1).Due to the fact that Compton-electrons go forward with a few centimetre range, the dose increases at the entrance (build-up effect) to a maximum value at 3-4 cm below the skin.This increase is followed by a shallow exponential decay for greater depth. ApplicationIn the most advanced treatments the X-ray dose is given from many (5-10) ports by rotating the electron linac around the patient and modulating the shape and intensity of each port sep arately using computer-controlled multileaf-collimators.With this Intensity M odulated Radio Therapy (IMRT) the most conformal X-ray treatment can be given at the expense of a greater integral dose, which is nevertheless distributed to the normal tissues around the target.