Α/β value

A measure of the curvature of the cell survival curve. The α/β value is also the dose at which the linear α and quadratic β components of cell killing are equal. For normal and cancer tissues, the α/β value is a measure of their sensitivity to changes in dose fractionation. Tumor and early responding tissues have a high α/β ratio and are not sensitive to changes in dose fractionation while late responding tissues have a low α/β ratio and are sensitive to changes in dose fractionation.

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from ICRP Publication 131, 2015

A measure of the curvature of the cell survival curve. The α/β value is also the dose at which the linear and quadratic components of cell killing are equal. For tissues, the α/β value is a measure of their sensitivity to changes in dose fractionation. In vivo, the β component describes the dose–response slope at low doses, which is often considered independent of dose rate, but it is likely that it can be modified in chronic radiation scenarios by cell renewal and cell competition processes. The β component describes the increase in slope at higher doses due to cumulative damage, which is repairable during fractionated or low-dose-rate exposures.