FIGURE 5.

Number of excitations required to fill the complete inner k‐space by the different techniques. A decay with T ₂* = 100 dk is assumed. Circles at the top illustrate the acquisition geometries. The number of excitations N _gap required to fill the inner 3D k‐space evolves with $k_{\mathit{gap}}^3$ for PETRA and $k_{\mathit{gap}}^2$ for WASPI. In the proposed HYFI method, inner k‐space is filled by a combination of single‐point imaging (SPI) and radial acquisitions, and thus the green area enclosed by the curves for PETRA and WASPI becomes accessible. Green lines represent selected HYFI acquisitions with amplitude coefficients A = 0.1 and 0.5