**2. α-particle emitters**

Radionuclides emitting α-particles such as 225Ac (half-life 10 days), 211At (half-life 7.2 h), 212Bi (half-life 60.55 min) and 213Bi (half-life 45.6 min) are options for treatment of small tumor nests or single disseminated tumor cells. Alfa particle emitting radionuclides are short ranged, high-energy helium nuclei with a high linear energy transfer (LET). As a consequence, α-emitters have a high relative biological effectiveness (RBE) which means, if nuclear localisation is possible, fewer radionuclides per cell are needed (Fass, 2009).
