R3.6: Alpha Beta Values
As discussed in the Linear Quadratic Equation topic, the alpha/beta values describe the curvature of a cell survival curve. The alpha/beta ratio is the dose where cell killing due to the linear and quadratic components are equal. In general:
- The higher the alpha/beta ratio, the more linear the cell survival curve will be
- The lower the alpha/beta ratio (ie. high beta relative to alpha), the more curved the cell survival curve.
This is important, as for low doses the low alpha/beta tissues are relatively resistant compared with high alpha/beta tissues. This allows for splitting of the effects seen in these tissues if doses in this range are given.
Typically:
- Early responding tissues have a high alpha beta ratio
- Late responding tissues have a low alpha beta ratio
- Most tumours have a high alpha beta ratio
- Some tumours (eg. melanoma, sarcoma, prostate) have a low alpha beta ratio
