1014-1015 / 1173
Summary
• Continuous low dose rate irradiation
– Irradiation times (hours - days) are long as compared to
the half time of repair ( 0.5 - 1.5 hour ). Effect dominated
by repair capacity (α/β ratio)
• High dose rate irradiation
– Irradiation time is too short for repair during the
irradiation, unless repair is very fast (in the order of
minutes).
• IMRT
– For complex treatments lasting ≥20-30 min, loss of
effective dose may be 5-10%, but depends on α/β and
T
1/2.
– Possibly compensated by reoxygenation in vivo
– High instantaneous dose rate (flattening filter-free): no
change in effect