... half-life, low ( , n) 458 years Long half-life, easily shielded 124 Sb-Be 210 Po-Be 214 Am-Be -ray background, low cost -ray background, high cost 241 Am-242CmBe ( , n) 163 days Short half-life, ... Deckman, W.G Roberge, and K.L D'Amico, Three-Dimensional X-Ray Microtomography, Science, Vol 237, 18 Sept 1987, p 143 9-1 444 G.N Ramachandran and A.V Laksh-minarayanan, Three-Dimensional Reconstruction ... Deckman, W.G Roberge, and K.L D'Amico, Three-Dimensional X-Ray Microtomography, Science, Vol 237, 18 Sept 1987, p 143 9-1 444 52 G.N Ramachandran and A.V Laksh-minarayanan, Three-Dimensional Reconstruction...