Figure 4. Examining the stem-stone interface:

Five representative stones with identifiable stems are shown. 3D volume rendered images of stone with stems are shown in (a), while cross sectional images (b) reveal the lower mineral density of the stones (darker areas) in comparison to their higher density stems (lighter areas) based on Hounsfield units. The physical cross sections of the same stones, as observed using a scanning electron microscope can be seen in (c), while at a higher magnification the detail of stone-stem interface contained within the same cross section is shown in (d). Depending on the sectioning plane, intact and seemingly patent tubules were identified within the stem of the stone (3–5 in d).