ABSTRACT
Traditionally, brachytherapy was performed as a low-dose rate (LDR)
therapy using radium (
Ra) or its daughter element radon (
Rn). Radium
has the advantage of a very long half-life, but it also has the disadvantage
of producing the alpha-emitting gaseous daughter product radon. By
modern radiation safety standards, radium, and radon sources are
considered to be unsafe and are no longer used. Today, the vast majority of
interstitial brachytherapy treatments are being performed as a high-dose
rate (HDR) temporary implant brachytherapy with
Ir or
Co, or LDR
permanent implant brachytherapy with
I, or
Pd sources. The choice
of radionuclides that can be used for brachytherapy, however, is limited
because only a few have all the desirable properties of the ideal
brachytherapy source (see also Table 5.3). These ideal properties are as
follows:
1. The optimum gamma-ray emission energy should be high enough
to avoid increased energy deposition in bone by the photoelectric
effect and also high enough to minimize scatter. At the same time
it must be low enough to minimize protection requirements.
