What does stopping power refer to in radiation therapy?

Stopping power in radiation therapy refers to the kinetic energy lost per unit path length as charged particles pass through a material. This concept is crucial for understanding how particles, such as electrons or protons, interact with tissues during radiation treatment. When these particles travel through a medium, they lose energy primarily through ionization and excitation of the atoms in the material. The stopping power quantifies this energy loss, which helps to determine how much energy the particles deposit in the tissue over a specific distance.

Stopping power is crucial for accurately calculating dose distributions in radiation therapy, allowing clinicians to optimize treatment plans to maximize the therapeutic effect on tumors while minimizing damage to surrounding healthy tissues. The ability to quantify how quickly particles lose energy informs decisions regarding beam energy, treatment depth, and overall treatment efficacy.

The other options touch on important concepts in radiation therapy but do not accurately define stopping power. Rate of ionization relates to the activity of ionization events caused by radiation in a material, scattering describes how particles deviate from their original path when interacting with matter, and energy deposited in a material refers to the overall energy imparted from radiation but not specifically tied to the concept of stopping power as the energy lost per unit distance.