Figure 4.

The figure shows energy deposited in and around a spherical shell source. This approximates a situation where there is uptake around the outer rim of a core without uptake. Panels (a,b) illustrate examples of shell thicknesses for the two outer diameters and show the central slices of images containing the energy deposition maps of the shells, where each quarter shows a different source. In panels (c,d), the ratio of energy deposited in the shell source (E_dep(shell)) to total deposited energy (E_dep(total)) is plotted against the shell thickness. In panels (e,f), the ratio of energy deposited in the core (E_dep(core)) to total deposited energy is also plotted against shell thickness. Two different outer diameters were used: in (a,c,e), shells with an outer diameter of 10 mm are shown, and, in (b,d,f), shells with an outer diameter of 30 mm are shown. Four different sources were used, three pure beta sources with beta energies following the emission spectra for ⁹⁰Y, ¹⁷⁷Lu, and ¹³¹I, and an alpha source with alpha energies of 5.5 MeV.