FIGURE 1. A model of the water ¹H NMR lineshapes in human cortical bone.

Across a macroscopic volume of cortical bone akin to an MRI voxel (middle), numerous bound and pore water components are combined into a broad net NMR spectrum with similarly broadened bound and pore water contributions. On the local microscale (right), bound water in the bone matrix space gives rise to a homogeneously broadened NMR spectrum. Conversely, the relatively mobile water within each pore space gives rise to a narrower NMR spectrum of varied chemical shift (dictated by pore geometry and pore-matrix susceptibility variation). The sum of these microscale contributions gives rise to a heterogeneously broadened pore water lineshape across macroscopic bone volumes (middle).