線性二次方(LQ)模式、分次敏感度、α/β、與相對效應

An Introduction of the Linear-Quadratic (LQ) Model, Fractionation Sensitivity, α/β Ration, and Relative Effectiveness

任益民(Yee-Min Jen)

《放射治療與腫瘤學》 1卷1期 (1994/03) Pp. 47-53

https://doi.org/10.6316/TRO/199401(1)47

並列摘要

Mathematical models are introduced to quantify the relationship between radiation dose and the subsequent survival response. During the past 3 decades, target theory, in the following form, has been the most popular model in both the radiation biology and oncology fields: SF=exp(-D/1D0) {1- [1-exp(-D/nDo)]}.
During the past 10 years, another model has appeared that provides a number of new parameters and concepts apart from its simple mathematical form as follows:
SF=e-(αD+βD ²)
It was derived during the 1970’s with the assumption that DNA double strand breaks form the basis of cell kill. In 1976, it was first used to analyze a set of experimental data, using the “Fe plot” method and the following equation obtained from the simple LQ model: 1/D(α+βd)/E= (α/E) + (β/E)d
In 1982, it was published that tissues can be divided into either early or late responding tissues, and they show a differential sensitivity to alterations of fraction size. The early-responding tissues, showing a higher α/β ratio, are less sensitive to this change in fraction size, while late-respooding tissues, having a low α/β ratio, are more sensitive. In addition to fractionation sensitivity, the concept of relative effectiveness is also mathematically described:
(方程式), where d=dose/fraction.
The extrapolated resposne (tolerance) dose, or the biologically effective dose (BED), is defined as the following: .
(方程式), where D=total dose.
The BED can be used in a number of ways to quantitatively compare biological effects of different irradiation regimens, and is of potential clinical importance.