Apparent diffusion coefficient in the low-frequency limit when measured with oscillating-gradient spin-echo diffusion-weighted imaging

The target of oscillating-gradient spin-echo diffusion-weighted imaging (OGSE-DWI) is the spectral density of molecular diffusion, $u₂(ω)$, which is predicted to obey a set of asymptotic universality relations that are linked to the global organisation of the sample. In principle, the complex microstructure of a medium can be classified by measuring the spectral density in its low- and high-frequency limits. However, the quantity most often measured with OGSE-DWI is the apparent diffusion coefficient (ADC). It was the purpose of this study to investigate how the low-frequency asymptotic behaviour of the spectral density is reflected in the ADC.