Radonc Biology

# Linear Quadratic Model

## Isoeffect Model

D_{2}/D_{1} = (alpha/beta + d_{1})/(alpha/beta + d_{2})

- D and d are total dose and dose per fraction

## Change from low-dose-rate (LDR) to HDR.

*Effect of change to HDR on Tumor Control*

Assume alpha-beta ratio of 10 Gy with µ (tumor) = 0.46 h^{-1}

Desired tumor dose is LDR TD = 40

Dose rate is R = 0.55 Gy/hr

- BED (LDR) = (LDR TD) [1 + (2 x R)/(µ x alpha-beta)] = 49.6

## BED for fractionated radiation

- BED = Nd [ 1 + d/(alpha-beta) ]

N is number of fractions

d is dose per fraction

page revision: 8, last edited: 03 Sep 2008 14:55