Figure 2.

Decay chains. Alpha-particle emitters are in red boxes and stable isotopes are in green boxes. The box in light green to the far right (²⁵¹Cf) indicates that although the isotope is considered stable in medical applications (T_1/2 = 898 years), it can still decay via ²²⁷Ac to ²⁰⁷Pb (stable). The T_1/2 is shown inside each box, and between boxes the type of decay [α, β^(−/+), or EC (electron capture)], with the probability of each decay route occurring (expressed as %). In the figure are also shown three alpha-particle emitters that are not mentioned in the text: ²³⁰U, ²²⁶Th, and ²⁵⁵Fm. Studies on the feasibility of producing ²³⁰U and its daughter ²²⁶Th via proton irradiation of ²³¹Pa according to the ²³¹Pa (p, 2n) ²³⁰U reaction have been performed (29). So far, there are no published data on the use of these three nuclides for TAT, although ²⁵⁵Fm has been occasionally mentioned as a potential candidate for targeted radionuclide therapy.