Which type of cells are more susceptible to radiation damage in fractionation?

Rapidly dividing cells are more susceptible to radiation damage during fractionation due to their high rate of proliferation and metabolic activity. Radiation primarily affects cellular processes during the division phase, particularly during mitosis when the cells are more vulnerable to DNA damage.

Fractionation refers to delivering radiation in multiple smaller doses over time rather than a single large dose. Rapidly dividing cells, such as those found in tumors or tissues with high turnover like the intestinal lining and bone marrow, are actively engaged in the process of cell division. This engagement means they are more likely to encounter and be damaged by ionizing radiation, which can disrupt their ability to replicate and function.

In contrast, slowly dividing cells, such as muscle cells, tend to have a lower rate of division and thus are less frequently exposed during the critical phases of the cell cycle when they are most vulnerable to radiation exposure. Immune cells can vary, but many are not actively dividing in high numbers at all times, which also makes them less susceptible compared to rapidly dividing cells.