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The linear no-threshold model (LNT) is a dose-response model used in radiation protection to estimate stochastic health effects such as radiation-induced cancer, genetic mutations and teratogenic effects on the human body due to exposure to ionizing radiation. The model assumes a linear relationship between dose and health effects, even for ...
The parameters of the dose response curve reflect measures of potency (such as EC50, IC50, ED50, etc.) and measures of efficacy (such as tissue, cell or population response). A commonly used dose–response curve is the EC 50 curve, the half maximal effective concentration, where the EC 50 point is defined as the inflection point of the curve.
The dose values are divided by the maximum dose, referred to as d max, yielding a plot in terms of percentage of the maximum dose. Dose measurements are generally made in water or "water equivalent" plastic with an ionization chamber , since water is very similar to human tissue with regard to radiation scattering and absorption.
For policy-making purposes, the commonly accepted model of dose response in radiobiology is the linear no-threshold model (LNT), which assumes a strictly linear dependence between the risk of radiation-induced adverse health effects and radiation dose, implying that there is no safe dose of radiation for humans.
Dose response curve of linear-non-threshold model. The International Commission on Radiological Protection (ICRP) describes how deterministic effects, or harmful tissue reactions, occur. [ 5 ] There is a threshold dose which causes clinical radiation damage of cells in the body. [ 5 ]
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
The radiation adaptive response seems to be a main origin of the potential hormetic effect. The theoretical studies indicate that the adaptive response is responsible for the shape of dose-response curve and can transform the linear relationship (LNT) into the hormetic one. [25] [26]
DVH summarizes 3D dose distributions in a graphical 2D format. In modern radiation therapy, 3D dose distributions are typically created in a computerized treatment planning system (TPS) based on a 3D reconstruction of a CT scan. The "volume" referred to in DVH analysis is a target of radiation treatment, a healthy organ nearby a target, or an ...