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We investigated the effect of microcirculatory flow on oscillating gradient spin echo (OGSE) diffusion MRI at low b‐values and developed a diffusion preparation method called diffusion encoding with dual‐frequency orthogonal gradients (DEFOG) to suppress the effect.

Compared to conventional OGSE sequences, DEFOG adds a pulsed gradient that is orthogonal to the oscillating gradient and has a moderate diffusion weighting (e.g., 300 s/mm²). In vivo MRI data were acquired from adult mouse brains (n = 5) on an 11.7 Tesla scanner, with diffusion times from 23.2 to 0.83 ms and b‐values from 50 to 700 s/mm².

Apparent diffusion coefficients (ADCs) measured using a conventional OGSE sequence at low b‐values (< 200 mm²/s) were significantly higher than those measured at moderate b‐values (> 300 mm²/s), potentially due to contributions from microcirculatory flow. In …