Fig. 2
From: Differentiating brain metastasis from glioblastoma by time-dependent diffusion MRI
Schematic representation of the diffusion gradient waveforms, (top line) and their corresponding diffusion encoding spectrums, |F(ω)|2, (bottom line) for pulsed gradient spin-echo (PGSE) (left) and oscillating gradient spin-echo (OGSE) (right). A 180° RF pulse is applied to the center of the gradient pair; therefore, the second gradient waveform acts as the opposite polarity. Δeff = Δ − δ/3. Δeff, effective diffusion time; Δ, diffusion gradient separation; δ, diffusion gradient pulse duration