Fig. 1.

Settings of nominal flip angle (FA) (a), label duration (b), sequence repetition time (TR) (c) for optimal signal to noise ratio (SNR) per unit time as a function of B1 efficiency. Values are determined by combined numerical simulations of the labeling process, the general kinetic perfusion model, and a specific absorption rate (SAR) model of the 7-T MRI scanner. Resulting SNR per unit time (d). The following values were used for this simulation: pseudocontinuous arterial spin labeling repetition time (TR _pCASL) = 1.2 ms; mean gradient strength = 0.6 mT/m; cerebral blood flow (CBF) = 95 ml/100 ml/min; blood transit time from the labeling slab to the imaging slice = 1,450 ms; postlabeling delay = 1,500 ms, and blood velocity = 20 cm/s