Life and Work of Rolf Wideröe by © Pedro Waloschek, => Contents
Wideröe has clearly shown the advantages of using photons and electrons of higher energy for radiation-treatments. Betatrons were first used for this purpose after the Second World War. Due to their compactness, they could be mounted in a suspended position or even be mobile. They were built for energies of up to 45 MeV. Cobalt 60 bombs were also used for radiation therapy during that period. After 1970, compact and relatively economical linacs increasingly came into use. Their technology was very reliable and had its origins in particle physics laboratories. The most important developments were achieved in the Stanford Linear Accelerator Centre (SLAC) in the USA.
The physicist John Ford, an expert in this field and Vice President of `Varian Health Care Systems', reported in 1993 [Fo93] that approximately 3,500 linacs were being used for radiation therapy throughout the World, half of them in the USA. Usually these linacs reach an electron energy of about 20 MeV. Higher electron energies (30 to 45 MeV, as it was the case with betatrons) are rarely used today.
According to John Ford, more than half of all cancer patients (in the USA and Western Europe) are today treated with radiation therapy, used either as the main form of therapy or in conjunction with surgery and chemotherapy. The most important fact about this is that in about 50% of the cases which are pronounced healed, the cure can be entirely or partly attributed to radiation therapy.
Today, electron irradiation is used in 10 to 15% of all
therapy cases, the remainder use X-rays, whereby technical progress in
the equipment has improved the irradiation quality. The
linacs used for this are relatively small and reach up to 20 MeV within 60 cm
of sophisticated iris-loaded wave-guides in which an
electromagnetic travelling wave accelerates the electrons.