Basic Clinical Radiobiology 2017

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 value) • 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