ABSTRACT
Since Henri Becquerel’s discovery of radioactivity in 1896 and Pierre
and Marie Curie’s discovery of radium in 1898, more than a century has
elapsed and
Ra and its daughter product
Rn are no longer used for
the treatment of cancer. They have now been totally replaced by artificially
produced radionuclides, such as
Ir,
Co,
Cs, and
I. After the
Manhattan Project, such replacements were inevitable for reasons of
radiation safety because of the high energies of
Ra gamma-photons,
its extremely long half-life of 1620 years, and the fact that
Rn is gaseous.
In addition, the maximum obtainable specific activity of
