Radonc Biology

Linear Quadratic Model

Isoeffect Model

D2/D1 = (alpha/beta + d1)/(alpha/beta + d2)

  • 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

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-Share Alike 2.5 License.