Sädeannos

Sädeannos, often translated as radiation dose, is a fundamental concept in radiometry and radiation protection. It quantifies the amount of ionizing radiation absorbed by a material, typically biological tissue. The primary unit for absorbed dose is the Gray (Gy), defined as one joule of energy absorbed per kilogram of mass. Historically, the rad was used, with 1 Gy equaling 100 rad.

While absorbed dose measures the energy deposited, it does not fully account for the biological impact of different types of radiation. This is where the concept of equivalent dose comes into play. Equivalent dose considers the biological effectiveness of various radiation types, such as alpha particles or neutrons, compared to gamma rays or X-rays. It is measured in Sieverts (Sv). The equivalent dose is calculated by multiplying the absorbed dose by a radiation weighting factor specific to the type of radiation. One Sievert is equivalent to one Gray when the radiation weighting factor is one (e.g., for photons and electrons).

Effective dose is a further refinement that accounts for the varying sensitivity of different organs and tissues to radiation. It is calculated by summing the equivalent doses to individual organs, each multiplied by an organ weighting factor that reflects its radiosensitivity. Like equivalent dose, effective dose is also measured in Sieverts. These dose metrics are crucial for assessing the risks associated with radiation exposure, setting safety limits, and planning radiation therapy treatments.