# Biology Course question

Q2: The survival data for normal tissue cells and for tumour cells exposed to single acute doses of x-radiation are as follows:

Dose [Gy] |
Normal Tissue Cell Survival |
Tumour Tissue 1 Cell Survival |
Tumour Tissue 2 Cell Survival |

0 |
0.92000 |
0.77000 |
0.83000 |

0.9 |
0.80000 |
0.63000 |
0.78000 |

2.1 |
0.67000 |
0.45000 |
0.71000 |

3.3 |
0.50000 |
0.32000 |
0.59000 |

5.4 |
0.26000 |
0.13000 |
0.38000 |

7.6 |
0.10000 |
0.04000 |
0.20000 |

9.2 |
0.03000 |
0.02000 |
0.11000 |

12.4 |
0.00300 |
0.00300 |
0.02300 |

14.2 |
0.00070 |
0.00090 |
0.00880 |

On semi-logarithmic graphs, plot the points of the three cell survival curves. Then draw the “best-fit” curve through the sets of data points, using a spreadsheet or math program (e.g. MatLab, Excel) to do the fit. Use the Linear Quadratic (LQ) Model of cell killing to fit the data to each curve.

Determine the LQ parameter values of **α, β, and α/β **ratio for each cell type and illustrate these values on the graphs as a “check” of the curve-fitted values. Specify all units for these quantities.

What is the biophysical interpretation (in text – not math) of α, β, and the α/β ratio?