Characteristics of 60Co γ-ray SPR (scatter-primary ratio), SF (scatter factor), β (dose-kerma ratio), and dmax (depth of maximum dose)

For 60Co γ-rays, using zero-area tissue-maximum ratio (TMR) and revised scatter-maximum ratio (SMR) data, we investigate how the scatter-primary ratio (SPR), the scatter factor (SF), and the dose-kerma ratio (β) change with field size and depth. We also investigate how the depth of maximum absorbed dose (dmax) changes with field size in three ways: the first uses zero-area primary plus scatter absorbed dose data, the second uses integrated primary absorbed dose data, and the third uses integrated primary plus scatter absorbed dose data. The investigated characteristics are also compared with reported ones. (author)