Accelerators have recently been used in cancer radiation treatment instead
of the application of X-rays. The main limitation of the use of X-rays
is that they deposit most of their energy where they originally enter the
body, and in order not to damage healthy tissue, the overall dose has to
be rather limited. On the other hand, particle beams offer the advantage
of depositing most of the energy in a rather narrow region just before
they are stopped in the tissue.
The four figures compare the dose received by different parts of the
body by X-ray irradiation (top) and proton irradiation (bottom). The left
images show the application of the beam from a single direction, and the
right images show the more advantageous application from several directions.
In both cases, the undesireable irradiation of healthy tissue is significantly
reduced by the use of protons, allowing for a more selective and effective
treatment of the cancer tissue.
||Two particle beam treatment facilities, the proton therapy system at
Loma Linda university (left), and the neutron system at Harper Hospital,
which is based on a cyclotron developed at Michigan State University (right).
|Irradiation by ion beams is also used in different medical applications;
wear and corrosion and hence failure of surgical steel can be reduced by
nitrogen implantation through bombardment, as in the artificial femur shown
on the right.