In addition to the R = 3 protocols, 2 FLASH protocols with higher acceleration (R = 4) were tested: increased temporal resolution to 40 ms duration and increased spatial resolution to 256 × 144 matrix size. An example of R = 4 256 × 144 rest perfusion FLASH study is shown here. (a) and (b) are surface coil inhomogeneity corrected perfusion images for GRAPPA and nonlinear method. The time intensity curves for a pixel selected in myocardium are plots in (e). The pixel-wise MBF maps are shown in (e) and (d). Due to the very poor SNR in the linear reconstruction, its MBF map is degraded, while the nonlinear MBF map gives much better quality. For a ROI drawn in the myocardium, the MBFs (ml/min/g) are 0.97 ± 0.33 (linear) and O.85 ± 0.16 (nonlinear), demonstrating the reduction of variability of MBF estimation.