Estimation of pore size in a microstructure phantom using the optimised gradient waveform diffusion weighted NMR sequence

► We implement optimised gradient waveform (GEN) diffusion protocols on a 9.4 T system. ► We construct microcapillary fibre phantoms with pore radii 1-10 μm. ► We compare sensitivity of GEN and optimized PGSE protocols to small pore radii. ► GEN provides improved sensitivity to the smaller pore radii compared to PGSE. ► Improvement most marked at gradient strengths available to clinical scanners.