  Diffusion-weighted imaging (DWI) is a powerful non-invasive tool which is
widely used in clinical routine. Mostly, apparent diffusion coefficient maps
are acquired, which cannot be directly related to cellular structure.
  More recently it was shown that DWI is able to reconstruct pore shapes using
a specialized magnetic field gradient scheme so that cell size distributions
may be obtained. So far, artificial systems have been used for experimental
demonstration without extraporal signal components and relatively low gradient
amplitudes.
  Therefore, the aim of this study was to investigate the feasibility of
diffusion pore imaging in the presence of extraporal fluids and to develop
correction methods for effects arising from extraporal signal contributions.
Monte Carlo simulations and validation experiments on a 14.1 T spectrometer
with a dedicated diffusion probe head were performed.
  Both by using a filter gradient approach suppressing extraporal signal
components as well as using postprocessing methods relying on the Gaussian
phase approximation, it was possible to reconstruct pore space functions in the
presence of extraporal fluids with little to no deviations from the
expectations. These results may be a significant step towards application of
diffusion pore imaging to biological samples. While still ultra-high gradients
are required, this problem may be mitigated by recent developments in the field
of local gradient coils for human applications.
