FIGURE 1.

PMRI (top) and MRI (bottom) pulse sequences used in this work, with analytical expressions for the magnetization at the start of FID acquisition. Their ratio $\alpha$ represents the SNR gain due to prepolarization, as per Equation (2). $M_{\mathrm{t}}$ and $M_0$ are the magnetizations in thermal equilibrium with and without prepolarization and are directly proportional to $B_{\mathrm{t}}$ and $B_0$ respectively. Red dashed lines represent the longitudinal magnetization. Black points represent k‐space data measured during the acquisition, while white points are not measured and lead to a gap in $k$ space