ABSTRACT
The clonogenic assay that celebrates its golden jubilee in 2006 is the cornerstone of classical radiobiology. This technique evolved from one that had long been used by bacteriologists for determining bacterial survival; the ‘‘plating’’ of diluted suspensions of bacteria on nutrient agar in a petri dish and counting the number of bacterial colonies that became visible after a short period of incubation. Puck and Marcus [1] developed an equivalent technique using a nutrient medium that would support the growth of mammalian cells. Single cells were plated in petri dishes; a proportion of the cells attached to the glass and those which were viable proliferated to form macroscopic colonies that could be counted after 7-10 days incubation. The first paper to describe this technique showed that radiation reduced the viability of mammalian cells in terms of clonogenic survival (Figure 4.1).
