75 / 1840
60
Co: containing radioactive needles, Wiiliam Myers, Ohio State University 1947
(cobanic: 45% Co & 55% Ni): 1mm small diameter and could be bent!
Radionuclides: A Review
137
Cs: Longer half life than
60
Co (30 vs. 5 years), lower energy than
60
Co
(0.662 vs. 1.25 MeV)
198
Au: replaces
222
Rn seeds since 1910.
192
Ir: since 1958 as seed by Ulrich Henscke. From early 1960s mainly
as wire (IGR, Paris-group). High speicifc activity and thus appropriate as
Miniaturized stepping source.
125
I: since late 60s as seeds for interstitial applications.
103
Pd: shorter half life than
125
I (17 vs. 59 days) and very high specific activity.