ABSTRACT
This organ motion adds an additional component of
uncertainty, which may also exceed 10 mm, in localizing
the target for treatment delivery. Both organ motion and
setup variation must be taken into account in defining
planning target volume (PTV) margins to adequately
encompass the prostate with the intended dose (17-19).
Target positional variations over a course of treatment
have a number of potential sources, and their statistical
descriptions as random and systematic processes have
been developed to weigh their relative influences on
targeting accuracy (15,16).
