2850-2851 / 3107
α/β ratio: Fractionation sensitivity in tumours and normal tissues
• DR curve more bendy for late
responding tissues – LQ translates
into lower α/β ratio
• Late responding normal tissues
(spinal cord, kidney): 1-4 Gy
• Most tumours: 8-15 Gy
• Other tumours such as melanomas,
liposarcomas, prostate
adenocarcinoma: 1-4 Gy
• Early responding normal tissues
(skin, mucosa): 8-15 Gy
• Decrease dose per fraction (or dose
rate)
•
Tissues with lower / ratios will
be preferentially spared
compared to those with higher
/ ratios. – i.e. reduction in cell
kill