Compact proton accelerator could revolutionise radiotherapy
3 August 2007
The prospect of more widely available proton radiation
therapy has moved closer with the development of a compact device called a
dielectric wall accelerator (DWA).
A prototype DWA is currently
being built at Lawrence Livermore, Laboratory in the US. It can accelerate
protons to up to 100 million electron volts in just a metre. A two-metre DWA
could potentially supply protons of sufficiently high energy to treat all
tumours, including those buried deep in the body, while fitting in a
conventional radiation treatment room.
Artist's concept of a compact proton therapy system
based on a "dielectric wall accelerator."
Credit: Lawrence Livermore National Laboratory,
TomoTherapy, and University of California, Davis
Thomas R. Mackie,
a professor at the University of Wisconsin and co-founder of the radiation
therapy company TomoTherapy, presented the new design at last month's annual
meeting of the American Association of Physicists in Medicine in
Minneapolis. Professor Mackie is part of a multidisciplinary team that
includes his institutions as well as Lawrence Livermore National Laboratory
and the University of California, Davis.
Compared to the x-rays
conventionally used in radiation therapy, protons are potentially more
effective, as they can deposit more cell-killing energy in their tumour
targets and less in surrounding healthy tissue.
However, to kill tumours, the protons must be accelerated to sufficiently
high energies, which currently must be achieved in large, expensive devices
called cyclotrons or synchrocyclotrons that cost hundreds of millions of
dollars and occupy a room the size of basketball courts.
In addition to
its smaller size, a DWA-based proton therapy system would have another
benefit — it could vary both proton energy and proton-beam intensity, two
variables that cannot both be adjusted at the same time in existing
proton-treatment facilities. This capability could lead to
"intensity-modulated proton therapy" (IMPT), the proton version of the
x-ray-based intensity modulated radiation therapy (IMRT) technique which has
become a popular method for delivering precise radiation doses to the parts
of a tumour.
Professor Mackie cautions that clinical trials of the system
are at least five years away. But if the DWA approach proves feasible,
protons may eventually represent a widespread, rather than limited, option
for treating cancer.
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